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Sample records for monocytogenes viable counts

  1. Viable but non-culturable Listeria monocytogenes on parsley leaves and absence of recovery to a culturable state.

    Science.gov (United States)

    Dreux, N; Albagnac, C; Federighi, M; Carlin, F; Morris, C E; Nguyen-the, C

    2007-10-01

    To investigate the presence of viable but non-culturable Listeria monocytogenes during survival on parsley leaves under low relative humidity (RH) and to evaluate the ability of L. monocytogenes to recover from VBNC to culturable state under satured humidity. Under low RH (47-69%) on parsley leaves, the initial number of L. monocytogenes populations counted on non selective media (10(9) L. monocytogenes per leaf on TSA) was reduced by 6 log10 scales in 15 days, whereas number of viable L. monocytogenes counted under the microscope was reduced by 3-4 log10 scales, indicating the presence of VBNC cells. This was demonstrated on three L. monocytogenes strains (EGDe, Bug 1995 and LmP60). Changing from low to 100% RH permitted an increase of the culturable counts of L. monocytogenes and this growth was observed only when residual culturable cells were present. Moreover, VBNC L. monocytogenes inoculated on parsley leaves did not become culturable after incubation under 100% RH. Dry conditions induced VBNC L. monocytogenes on parsley leaves but these VBNC were likely unable to recover culturability after transfer to satured humidity. Enumeration on culture media presumably under-estimates the number of viable L. monocytogenes on fresh produce after exposure to low RH.

  2. Viable-but-Nonculturable Listeria monocytogenes and Salmonella enterica Serovar Thompson Induced by Chlorine Stress Remain Infectious

    Directory of Open Access Journals (Sweden)

    Callum J. Highmore

    2018-04-01

    Full Text Available The microbiological safety of fresh produce is monitored almost exclusively by culture-based detection methods. However, bacterial food-borne pathogens are known to enter a viable-but-nonculturable (VBNC state in response to environmental stresses such as chlorine, which is commonly used for fresh produce decontamination. Here, complete VBNC induction of green fluorescent protein-tagged Listeria monocytogenes and Salmonella enterica serovar Thompson was achieved by exposure to 12 and 3 ppm chlorine, respectively. The pathogens were subjected to chlorine washing following incubation on spinach leaves. Culture data revealed that total viable L. monocytogenes and Salmonella Thompson populations became VBNC by 50 and 100 ppm chlorine, respectively, while enumeration by direct viable counting found that chlorine caused a <1-log reduction in viability. The pathogenicity of chlorine-induced VBNC L. monocytogenes and Salmonella Thompson was assessed by using Caenorhabditis elegans. Ingestion of VBNC pathogens by C. elegans resulted in a significant life span reduction (P = 0.0064 and P < 0.0001, and no significant difference between the life span reductions caused by the VBNC and culturable L. monocytogenes treatments was observed. L. monocytogenes was visualized beyond the nematode intestinal lumen, indicating resuscitation and cell invasion. These data emphasize the risk that VBNC food-borne pathogens could pose to public health should they continue to go undetected.

  3. Behaviour of Listeria monocytogenes in artisanal raw milk Pecorino Umbro cheese: a microbiological challenge test

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    Roberta Ortenzi

    2015-09-01

    Full Text Available In the present study, a microbiological challenge test in artificially contaminated raw milk Pecorino Umbro cheese during cheese-making was carried out. Raw ewe milk was contaminated by a suspension of particular Listeria monocytogenes strains. The number of L. monocytogenes and L. monocytogenes dynamic growth were evaluated during cheese-making and storage. A significant decrease of the viable count of L. monocytogenes was observed during ripening and L. monocytogenes viable count was below the limit of quantification during storage. The results show that the product is unable to support the growth of the pathogen.

  4. Fate of viable but non-culturable Listeria monocytogenes in pig manure microcosms

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    Jeremy eDesneux

    2016-03-01

    Full Text Available The fate of two strains of L. monocytogenes and their ability to become viable but non-culturable (VBNC was investigated in microcosms containing piggery effluents (two raw manures and two biologically treated manures stored for two months at 8°C and 20°C. Levels of L. monocytogenes were estimated using the culture method, qPCR, and propidium monoazide treatment combined with qPCR (qPCRPMA. The chemical composition and the microbial community structure of the manures were also analysed. The strains showed similar decline rates and persisted up to 63 days. At day zero, the percentage of VBNC cells among viable cells was higher in raw manures (81.5-94.8% than in treated manures (67.8-79.2%. The changes in their proportion over time depended on the temperature and on the type of effluent: the biggest increase was observed in treated manures at 20°C and the smallest increase in raw manures at 8°C. The chemical parameters had no influence on the behaviour of the strains, but decrease of the persistence of viable cells was associated with an increase in the microbial richness of the manures. This study demonstrated that storing manure altered the culturability of L. monocytogenes, which rapidly entered the VBNC state, and underlines the importance of including VBNC cells when estimating the persistence of the pathogens in farm effluents.

  5. Inhibition of Listeria monocytogenes by piscicolin 126 in milk and Camembert cheese manufactured with a thermophilic starter.

    Science.gov (United States)

    Wan, J; Harmark, K; Davidson, B E; Hillier, A J; Gordon, J B; Wilcock, A; Hickey, M W; Coventry, M J

    1997-03-01

    The effect of bacteriocin, piscicolin 126, on the growth of Listeria monocytogenes and cheese starter bacteria was investigated in milk and in Camembert cheese manufactured from milk challenged with 10(2) cfu ml(-1) L. monocytogenes. In milk incubated at 30 degrees C, piscicolin 126 added in the range of 512-2,048 AU ml(-1) effectively inhibited growth of L. monocytogenes for more than 20 d when challenged with approximately 10(2) cfu ml(-1) L. monocytogenes. At higher challenge levels (10(4) and 10(6) cfu ml(-1)), piscicolin 126 reduced the viable count of L. monocytogenes by 4-5 log units immediately after addition of the bacteriocin; however, growth of Listeria occurred within 24 h. The minimum inhibitory concentration (MIC) of piscicolin 126 against lactic acid cheese starter bacteria was generally greater than 204,800 AU ml(-1) , and the viable count and acid production of these starter cultures in milk were not affected by the addition of 2,048 AU ml(-1) piscicolin 126. Camembert cheeses made from milk challenged with L. monocytogenes and with added piscicolin 126 showed a viable count of L. monocytogenes 3-4 log units lower than those without piscicolin 126. Inactivation of piscicolin 126 by proteolytic enzymes from cheese starter bacteria and mould together with the emergence of piscicolin 126-resistant isolates was responsible for the recovery of L. monocytogenes in the cheeses during ripening.

  6. Kinetics of killing Listeria monocytogenes by macrophages: correlation of 3H-DNA release from labeled bacteria and changes in numbers of viable organisms by mathematical model

    International Nuclear Information System (INIS)

    Davies, W.A.

    1982-01-01

    Conventional methods of assessing antibacterial activities of macrophages by viable counting are limited by the precision of the statistics and are difficult to interpret quantitatively because of unrestrained extracellular growth of bacteria. An alternative technique based on the release of radioactive DNA from labeled bacteria has been offered as overcoming these drawbacks. To assess it for use with macrophages I have made a correlation with the conventional viable counting method using a mathematical model. Opsonized Listeria monocytogenes labeled with 3 H-thymidine were exposed to rat macrophages for periods up to 4 hr. Numbers of viable bacteria determined after sonication increased exponentially in the absence of live cells and this growth rate was progressively inhibited by increasing numbers of macrophages. After a lag period of 30-60 min soluble 3 H appeared in the supernatant, the amount increasing with time and numbers of macrophages. To correlate these data I developed a mathematical model that considered that changes in numbers of viable organisms were due to the difference between rates of 1) growth of extracellular bacteria and 2) killing within the macrophage. On the basis of this model curves of best fit to the viable counts data were used to predict the release of radioactivity, assuming that death of a bacterium led to the total release of its label. These predictions and the experimental data agreed well, the lag period of 30-60 min between death of the bacterium and release of radioactivity being consistent with intracellular digestion. Release of soluble radioactivity appears to be an accurate reflection of the number of bacteria killed within the macrophage

  7. Response of Listeria monocytogenes to disinfection stress at the single-cell and population levels as monitored by intracellular pH measurements and viable-cell counts

    DEFF Research Database (Denmark)

    Kastbjerg, Vicky Gaedt; Nielsen, Dennis S.; Arneborg, Nils

    2009-01-01

    of the bacterium. In situ analyses of Listeria monocytogenes single cells were performed during exposure to different concentrations of the disinfectant Incimaxx DES to study a possible population subdivision. Bacterial survival was quantified with plate counting and disinfection stress at the single-cell level...... by measuring intracellular pH (pHi) over time by fluorescence ratio imaging microscopy. pHi values were initially 7 to 7.5 and decreased in both attached and planktonic L. monocytogenes cells during exposure to sublethal and lethal concentrations of Incimaxx DES. The response of the bacterial population...... was homogenous; hence, subpopulations were not detected. However, pregrowth with NaCl protected the planktonic bacterial cells during disinfection with Incimaxx (0.0015%) since pHi was higher (6 to 6.5) for the bacterial population pregrown with NaCl than for cells grown without NaCl (pHi 5 to 5.5) (P

  8. Bacteriophage biocontrol of Listeria monocytogenes on soft ripened white mold and red-smear cheeses.

    Science.gov (United States)

    Guenther, Susanne; Loessner, Martin J

    2011-03-01

    Soft-ripened cheeses belong to the type of food most often contaminated with Listeria monocytogenes, and they have been implicated in several outbreaks of listeriosis. Bacteriophages represent an attractive way to combat foodborne pathogens without affecting other properties of the food. We used the broad host range, virulent Listeria phage A511 for control of L. monocytogenes during the production and ripening phases of both types of soft-ripened cheeses, white mold (Camembert-type) cheese, as well as washed-rind cheese with a red-smear surface (Limburger-type). The surfaces of young, unripened cheese were inoculated with 10(1)-10(3) cfu/cm(2)L. monocytogenes strains Scott A (serovar 4b) or CNL 10(3)/2005 (serovar 1/2a). Phage was applied at defined time points thereafter, in single or repeated treatments, at 3 × 10(8) or 1 × 10(9) pfu/cm(2). With Scott A (10(3) cfu/cm(2)) and a single dose of A511 (3 × 10(8) pfu/cm(2)) on camembert-type cheese, viable counts dropped 2.5 logs at the end of the 21 day ripening period. Repeated phage application did not further inhibit the bacteria, whereas a single higher dose (1 × 10(9) pfu/cm(2)) was found to be more effective. On red-smear cheese ripened for 22 days, Listeria counts were down by more than 3 logs. Repeated application of A511 further delayed re-growth of Listeria, but did not affect bacterial counts after 22 days. With lower initial Listeria contamination (10(1)-10(2) cfu/cm(2)), viable counts dropped below the limit of detection, corresponding to more than 6 logs reduction compared to the control. Our data clearly demonstrate the potential of bacteriophage for biocontrol of L. monocytogenes in soft cheese.

  9. Effect of benzalkonium chloride on viability and energy metabolism in exponential- and stationary-growth-phase cells of Listeria monocytogenes

    NARCIS (Netherlands)

    Luppens, S.B.I.; Abee, T.; Oosterom, J.

    2001-01-01

    The difference in killing exponential- and stationary-phase cells of Listeria monocytogenes by benzalkonium chloride (BAC) was investigated by plate counting and linked to relevant bioenergetic parameters. At a low concentration of BAC (8 mg liter-1), a similar reduction in viable cell numbers was

  10. Listeria monocytogenes impact on mature or old Pseudomonas fluorescens biofilms during growth at 4 and 20ºC

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    Puga eCH

    2016-02-01

    Full Text Available Changes in spatial organization, as observed by confocal laser scanning microscopy (CLSM, viable cell content, biovolume and substratum surface coverage of the biofilms formed on glass by Pseudomonas fluorescens resulting from co-culture with Listeria monocytogenes, were examined. Two strains of L. monocytogenes, two culture temperatures and two biofilm developmental stages were investigated. Both L. monocytogenes strains, a persistently sampled isolate (collected repeatedly along 3 years from a meat factory and Scott A, induced shrinkage in matrix volume, both at 20ºC and 4ºC, in mature or old biofilms, without loss of P. fluorescens cell count per surface unit. The nearly homogeneous pattern of surface coverage shown by mono-species P. fluorescens biofilms, turned into more irregular layouts in co-culture with L. monocytogenes. The upper layer of both mono and dual-species biofilms turned to predominantly consist of matrix, with plenty of viable cells underneath, in old biofilms cultured at 20ºC, but not in those grown at 4ºC. Between 15 and 56% of the substratum area was covered by biofilm, the extent depending on temperature, time and L. monocytogenes strain. Real biofilms in food-related surfaces may thus be very heterogeneous regarding their superficial components, i.e. those more accessible to disinfectants. It is therefore a hygienic challenge to choose an adequate agent to disrupt them.

  11. Prevalence of Listeria monocytogenes in Retail Lightly Pickled Vegetables and Its Successful Control at Processing Plants.

    Science.gov (United States)

    Taguchi, Masumi; Kanki, Masashi; Yamaguchi, Yuko; Inamura, Hideichi; Koganei, Yosuke; Sano, Tetsuya; Nakamura, Hiromi; Asakura, Hiroshi

    2017-03-01

    Incidences of food poisoning traced to nonanimal food products have been increasingly reported. One of these was a recent large outbreak of Shiga toxin-producing Escherichia coli (STEC) O157 infection from the consumption of lightly pickled vegetables, indicating the necessity of imposing hygienic controls during manufacturing. However, little is known about the bacterial contamination levels in these minimally processed vegetables. Here we examined the prevalence of STEC, Salmonella spp., and Listeria monocytogenes in 100 lightly pickled vegetable products manufactured at 55 processing factories. Simultaneously, we also performed quantitative measurements of representative indicator bacteria (total viable counts, coliform counts, and β-glucuronidase-producing E. coli counts). STEC and Salmonella spp. were not detected in any of the samples; L. monocytogenes was detected in 12 samples manufactured at five of the factories. Microbiological surveillance at two factories (two surveys at factory A and three surveys at factory B) between June 2014 and January 2015 determined that the areas predominantly contaminated with L. monocytogenes included the refrigerators and packaging rooms. Genotyping provided further evidence that the contaminants found in these areas were linked to those found in the final products. Taken together, we demonstrated the prevalence of L. monocytogenes in lightly pickled vegetables sold at the retail level. Microbiological surveillance at the manufacturing factories further clarified the sources of the contamination in the retail products. These data indicate the necessity of implementing adequate monitoring programs to minimize health risks attributable to the consumption of these minimally processed vegetables.

  12. A combination of direct viable count and fluorescence in situ hybridization for specific enumeration of viable Lactobacillus delbrueckii subsp.bulgaricus and Streptococcus thermophilus.

    Science.gov (United States)

    García-Hernández, J; Moreno, Y; Amorocho, C M; Hernández, M

    2012-03-01

    We have developed a direct viable count (DVC)-FISH procedure for quickly and easily discriminating between viable and nonviable cells of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains, the traditional yogurt bacteria. direct viable count method has been modified and adapted for Lact. delbrueckii subsp. bulgaricus and Strep. thermophilus analysis by testing different times of incubation and concentrations of DNA-gyrase inhibitors. DVC procedure has been combined with fluorescent in situ hybridization (FISH) for the specific detection of viable cells of both bacteria with specific rRNA oligonucleotide probes (DVC-FISH). Of the four antibiotics tested (novobiocin, nalidixic acid, pipemidic acid and ciprofloxacin), novobiocin was the most effective for DVC method and the optimum incubation time was 7 h for both bacteria. The number of viable cells was obtained by the enumeration of specific hybridized cells that were elongated at least twice their original length for Lactobacillus and twice their original size for Streptococcus. This technique was successfully applied to detect viable cells in inoculated faeces. Results showed that this DVC-FISH procedure is a quick and culture-independent useful method to specifically detect viable Lact. delbrueckii subsp. bulgaricus and Strep. thermophilus in different samples, being applied for the first time to lactic acid bacteria. © 2011 The Authors. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.

  13. The use of flow cytometry to accurately ascertain total and viable counts of Lactobacillus rhamnosus in chocolate.

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    Raymond, Yves; Champagne, Claude P

    2015-04-01

    The goals of this study were to evaluate the precision and accuracy of flow cytometry (FC) methodologies in the evaluation of populations of probiotic bacteria (Lactobacillus rhamnosus R0011) in two commercial dried forms, and ascertain the challenges in enumerating them in a chocolate matrix. FC analyses of total (FC(T)) and viable (FC(V)) counts in liquid or dried cultures were almost two times more precise (reproducible) than traditional direct microscopic counts (DCM) or colony forming units (CFU). With FC, it was possible to ascertain low levels of dead cells (FC(D)) in fresh cultures, which is not possible with traditional CFU and DMC methodologies. There was no interference of chocolate solids on FC counts of probiotics when inoculation was above 10(7) bacteria per g. Addition of probiotics in chocolate at 40 °C resulted in a 37% loss in viable cells. Blending of the probiotic powder into chocolate was not uniform which raised a concern that the precision of viable counts could suffer. FCT data can serve to identify the correct inoculation level of a sample, and viable counts (FCV or CFU) can subsequently be better interpreted. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

  14. Comparative inhibitory effects of Thymus vulgaris L. essential oil against Staphylococcus aureus, Listeria monocytogenes and mesophilic starter co-culture in cheese-mimicking models.

    Science.gov (United States)

    de Carvalho, Rayssa Julliane; de Souza, Geanny Targino; Honório, Vanessa Gonçalves; de Sousa, Jossana Pereira; da Conceição, Maria Lúcia; Maganani, Marciane; de Souza, Evandro Leite

    2015-12-01

    In the present study, we assessed the effects of Thymus vulgaris L. essential oil (TVEO) on Staphylococcus aureus and Listeria monocytogenes, pathogenic bacteria frequently associated with fresh or low-ripened cheeses (e.g., Brazilian coalho cheese), and on a starter co-culture comprising Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris, which are commonly used for the production of different cheeses. To measure these effects, we determined the minimum inhibitory concentration (MIC) and assessed bacterial cell viability over time in (coalho) cheese-based broth and in a semi-solid (coalho) cheese model at 10 °C. The MIC for TVEO was 2.5 μL/mL against S. aureus and L. monocytogenes, while the MIC was 1.25 μL/mL against the starter co-culture. The TVEO (5 and 2.5 μL/mL) sharply reduced the viable counts of all assayed bacteria in cheese broth over 24 h; although, at 5 μL/mL, TVEO more severely affected the viability of the starter co-culture compared with pathogenic bacteria. The addition of 1.25 μL/g of TVEO in the semi-solid cheese model did not reduce the viable counts of all assayed bacteria. At 2.5 μL/g, TVEO slightly decreased the viable counts of S. aureus, L. monocytogenes and Lactococcus spp. in the semi-solid cheese model over 72 h. The final counts of Lactococcus spp. in a semi-solid cheese model containing 2.5 μL/mL TVEO were lower than those of pathogenic bacteria under the same conditions. These results suggest that the doses of TVEO used to control pathogenic bacteria in fermented dairy products, especially in low-ripened cheeses, should be cautiously considered for potential negative effects on the growth and survival of starter cultures. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Changes in total viable count and TVB-N content in marinated chicken breast fillets during storage

    Science.gov (United States)

    Baltić, T.; Ćirić, J.; Velebit, B.; Petronijević, R.; Lakićević, B.; Đorđević, V.; Janković, V.

    2017-09-01

    Marination is a popular technique for enhancing meat properties. Depending on the marinade type and ingredients added, marination can improve sensory, chemical and microbiological quality of meat products. In this study, the total viable count and total volatile basic nitrogen (TVB-N) content in marinated chicken breast fillets were investigated. The possible correlation between bacterial growth and formation of TVB-N was also tested. Chicken breast fillets were immersed in a solution of table salt (as a control) orthree different marinades,which consisted of table salt, sodium tripolyphosphate and/or sodium citrate, and stored in air for nine days at 4±1°C. Analyses of the total viable count and TVB-N were performed on days0, 3, 6 and 9 day of storage. The total viable count gradually increased in all examined groups, and statistically significant differences (pchicken were significantly higher (pchicken marinated with sodium citrate was established (pchicken marinated with sodium tripolyphosphate.

  16. Estimation of Microbial Contamination of Food from Prevalence and Concentration Data: Application to Listeria monocytogenes in Fresh Vegetables▿

    Science.gov (United States)

    Crépet, Amélie; Albert, Isabelle; Dervin, Catherine; Carlin, Frédéric

    2007-01-01

    A normal distribution and a mixture model of two normal distributions in a Bayesian approach using prevalence and concentration data were used to establish the distribution of contamination of the food-borne pathogenic bacteria Listeria monocytogenes in unprocessed and minimally processed fresh vegetables. A total of 165 prevalence studies, including 15 studies with concentration data, were taken from the scientific literature and from technical reports and used for statistical analysis. The predicted mean of the normal distribution of the logarithms of viable L. monocytogenes per gram of fresh vegetables was −2.63 log viable L. monocytogenes organisms/g, and its standard deviation was 1.48 log viable L. monocytogenes organisms/g. These values were determined by considering one contaminated sample in prevalence studies in which samples are in fact negative. This deliberate overestimation is necessary to complete calculations. With the mixture model, the predicted mean of the distribution of the logarithm of viable L. monocytogenes per gram of fresh vegetables was −3.38 log viable L. monocytogenes organisms/g and its standard deviation was 1.46 log viable L. monocytogenes organisms/g. The probabilities of fresh unprocessed and minimally processed vegetables being contaminated with concentrations higher than 1, 2, and 3 log viable L. monocytogenes organisms/g were 1.44, 0.63, and 0.17%, respectively. Introducing a sensitivity rate of 80 or 95% in the mixture model had a small effect on the estimation of the contamination. In contrast, introducing a low sensitivity rate (40%) resulted in marked differences, especially for high percentiles. There was a significantly lower estimation of contamination in the papers and reports of 2000 to 2005 than in those of 1988 to 1999 and a lower estimation of contamination of leafy salads than that of sprouts and other vegetables. The interest of the mixture model for the estimation of microbial contamination is discussed. PMID

  17. Cellular and soluble components decrease the viable pathogen counts in milk from dairy cows with subclinical mastitis.

    Science.gov (United States)

    Koshiishi, Tomoko; Watanabe, Masako; Miyake, Hajime; Hisaeda, Keiichi; Isobe, Naoki

    2017-08-10

    The present study was undertaken to clarify the factors that reduce the viable pathogen count in milk collected from the udders of subclinical mastitic cows during preservation. Milk was centrifuged to divide somatic cells (cellular components, precipitates) and antimicrobial peptides (soluble components, supernatants without fat layer); each fraction was cultured with bacteria, and the number of viable bacteria was assessed prior to and after culture. In 28.8% of milk samples, we noted no viable bacteria immediately after collection; this value increased significantly after a 5-hr incubation of milk with cellular components but not with soluble components (48.1 and 28.8%, respectively). After culture with cellular components, the numbers of bacteria (excluding Staphylococcus aureus and Streptococcus uberis) and yeast decreased dramatically, although the differences were not statistically significant. After cultivation with soluble components, only yeasts showed a tendency toward decreased mean viability, whereas the mean bacterial counts of S. uberis and T. pyogenes tended to increase after 5-hr preservation with soluble components. These results suggest that most pathogens in high somatic cell count (SCC) milk decreased during preservation at 15 to 25°C, due to both the cellular components and antimicrobial components in the milk. Particularly, the cellular components more potently reduced bacterial counts during preservation.

  18. Inactivation of Listeria monocytogenes in raw fruits by enterocin AS-48.

    Science.gov (United States)

    Molinos, Antonio Cobo; Abriouel, Hikmate; Ben Omar, Nabil; Lucas, Rosario; Valdivia, Eva; Gálvez, Antonio

    2008-12-01

    The purpose of this study was to determine the effect of enterocin AS-48 on Listeria monocytogenes CECT 4032 in fruits and fruit juice. Fruits were contaminated with a L. monocytogenes cell suspension, washed with enterocin AS-48 (25 microg/ml) or with sterile distilled water as control, and stored at different temperatures (-20, 6, 15, 22 degrees C). Washing treatments significantly inhibited or completely inactivated L. monocytogenes in strawberries, raspberries, and blackberries stored at 15 and 22 degrees C for up to 2 days and in blackberries and strawberries at 6 degrees C for up to 7 days. Washing treatments with enterocin AS-48 also reduced viable counts in sliced melon, watermelon, pear, and kiwi but did not avoid proliferation of survivors during storage at 15 and 22 degrees C. Added enterocin (25 microg/ml) completely inactivated L. monocytogenes in watermelon juice within 24 h. To enhance the antilisterial activity of treatments, enterocin AS-48 was tested in combination with other antimicrobial substances on sliced melon stored at 22 degrees C. The combinations of enterocin AS-48 and trisodium trimetaphosphate, sodium lactate, lactic acid, polyphosphoric acid, carvacrol, hydrocinnamic acid, p-hydroxybenzoic acid, n-propyl p-hydroxybenzoate, or 2-nitropropanol showed increased antilisterial activities compared with each antimicrobial tested separately. Washing treatments with enterocin AS-48 in combination with 12 mM carvacrol, as well as with 100 mM n-propyl p-hydroxybenzoate, avoided regrowth of Listeria during storage at 22 degrees C. Results from this study indicate that enterocin AS-48 alone or in combination with other preservatives could serve as an additional hurdle against L. monocytogenes in fruits and fruit juices.

  19. Evaluation of a monoclonal antibody able to detect live Listeria monocytogenes and Listeria innocua

    DEFF Research Database (Denmark)

    Sølve, Marianne; Boel, Jeppe; Nørrung, Birgit

    2000-01-01

    A monoclonal Listeria antibody, designated B4, was evaluated. The ability of the antibody to bind to viable bacteria belonging to Listeria spp, compared to bacteria of the same species killed by beat treatment, acid or base treatment, sanitizers, and irradiation was examined. The antibody was found...... to react with viable L. monocytogenes and L. innocua, but not with heat-killed (72 degrees C, 5 min) strains of these organisms. When L. monocytogenes and L. innocua were killed by methods other than heat treatment, it was ambiguous whether the antibody detected the organism or not. It was concluded...... that the B4 antibody has potential to be used in an immune capture step to capture live L, monocytogenes and L. innocua from foods prior to identification of L. monocytogenes by polymerase chain reaction (PCR)....

  20. CHALLENGE TESTS WITH LISTERIA MONOCYTOGENES IN SALAMI: PRELIMINARY RESULTS

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    R. Mioni

    2013-02-01

    Full Text Available Challenge tests are the preferable methodology to study the behaviour of Listeria monocytogenes on ready to eat foods, according to Regulation (EC 2073/2005. Challenge testing using L. monocytogenes in seasoned salami from different food business operators showed, after seasoning of the product, a count reduction of the inoculated organisms without any further growth of the pathogen; however differences of L. monocytogenes behaviour could be observed according to different production protocols.

  1. Evaluation of Bacteriological Quality of Ready-to-eat Chicken Products by Total Viable Count Method

    OpenAIRE

    Ramiz Raja; Asif Iqbal; Yasir Hafiz; Mehboob Willayet; Shakoor Bhat; Mudasir Rather

    2012-01-01

    The present investigation describes the total viable count of ready-to-eat chicken products (chicken patties and chicken rolls) in Srinagar city during two seasons viz. autumn and winter. A total of 120 ready-to-eat chicken products comprising of 60 chicken patties and 60 chicken rolls were tested. The mean bacterial count of 60 chicken patties and 60 chicken rolls was 5.1281 and 4.9395 log10 cfu/g. Bacillus cereus strains were isolated from 25 of chicken patties and 22 of the chicken rolls r...

  2. Evaluation of the thin agar layer method for the recovery of pressure-injured and heat-injured Listeria monocytogenes.

    Science.gov (United States)

    Lavieri, Nicolas A; Sebranek, Joseph G; Cordray, Joseph C; Dickson, James S; Jung, Stephanie; Manu, David K; Mendonça, Aubrey F; Brehm-Stecher, Byron F; Stock, Joseph; Stalder, Kenneth J

    2014-05-01

    A sublethally injured bacterial cell has been defined as a cell that survives a stress such as heating, freezing, acid treatment, or other antimicrobial intervention but can repair the cellular damage exerted by the stressor and later regain its original ability to grow. Consequently, sublethally injured cells are not likely to be included in conventional enumeration procedures, which could result in unrealistically low counts unless efforts are made to encourage recovery of the injured cells before enumeration. The objective of this study was to evaluate the use of the thin agar layer (TAL) method for the recovery of pressure-injured and heat-injured Listeria monocytogenes in a tryptic soy broth with 0.6% yeast extract system. Pressure injury consisted of treatment of a culture of mixed L. monocytogenes strains with high hydrostatic pressure at 400 or 600 MPa for 1 s, 2 min, 4 min, or 6 min at a process temperature of 12±2 °C. Heat injury consisted of treatment of a culture of mixed L. monocytogenes strains at 60±1 °C for 3, 6, or 9 min. Growth media were tryptic soy agar (TSA) with 0.6% yeast extract, modified Oxford medium (MOX), and TAL, which consisted of a 7-ml layer of TSA overlaid onto solidified MOX. Counts of viable L. monocytogenes on TAL were higher than those on MOX in the heat-injury experiment but not in the pressure-injury experiment. Therefore, the effectiveness of the TAL method may be specific to the type of injury applied to the microorganism and should be investigated in a variety of cellular injury scenarios.

  3. Quality of raw cow milk in Republic of Macedonia determined through the testing of somatic cell count and total viable count

    Directory of Open Access Journals (Sweden)

    Angelovski Ljupco

    2008-11-01

    Full Text Available Somatic cells count and total viable count are criteria used to estimate the compliance of raw cow milk with the Book of rules for demands for safety and hygiene and procedures for official controls of milk and milk products, Official Gazette of RM 157/2007. According to the given demands, raw milk operators are obliged to conduct all procedures and to guarantee that milk is in compliance with the criteria laid down in Book of rules. At the same time, Republic of Macedonia have to fulfill EU criteria laid down in Directive 92/46 (Council directive 92/46/EEC laying down the health rules for the production and placing on the market of raw milk, heat-treated milk and milkbased products for quality of raw milk as part of implementation of community legislation and milk production. The independent laboratory for milk quality control at FVM-Skopje, in frame of its activities in the period February- August 2008 has conducted a study for obtaining preliminary results for the situation with raw milk quality produced in R. of Macedonia for somatic cells counts and total viable count. In the study we analyzed 2065 samples for TVC and 1625 samples for SCC of raw milk samples produced in different parts of the country. From the tested samples only 41,8% fulfill criteria for SCC and 41,45% criteria for TVC lay down in Book of rules for 2008. Assessment of the results in light of Council Directive it is obvious that only 42,7% of the samples for SCC and 10,7% for TVC fulfill the criteria of Council Directive having in mind different requirements vs. Book of rules.

  4. Antibacterial activity of domestic Balkan donkey milk toward Listeria monocytogenes and Staphylococcus aureus

    Directory of Open Access Journals (Sweden)

    Šarić Ljubiša Ć.

    2014-01-01

    Full Text Available The aim of this study was to investigate the antibacterial activity of raw milk from Domestic Balkan donkey breed toward Listeria monocytogenes and Staphylococcus aureus. Examination of antibacterial activity was performed in artificially contaminated milk samples by monitoring the changes of count of viable cells of tested bacteria during 8 hours of incubation at 38°C. Lysozyme and fatty acids contents were also determined in donkey milk. The obtained results indicated inhibitory effect of donkey milk toward both tested bacteria. The lysozyme content in the analyzed milk samples was ranged from 0.67 to 3.54 g/L. The most abundant fatty acids with known antibacterial activity toward Gram positive bacteria were linoleic, lauric and oleic acid.

  5. A Dual Filtration-Based Multiplex PCR Method for Simultaneous Detection of Viable Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus on Fresh-Cut Cantaloupe.

    Directory of Open Access Journals (Sweden)

    Ke Feng

    Full Text Available Fresh-cut cantaloupe is particularly susceptible to contamination with pathogenic bacteria, such as Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus. Therefore, development of rapid, yet accurate detection techniques is necessary to ensure food safety. In this study, a multiplex PCR system and propidium monoazide (PMA concentration were optimized to detect all viable pathogens in a single tube. A dual filtration system utilized a filtration membrane with different pore sizes to enrich pathogens found on fresh-cut cantaloupe. The results revealed that an optimized multiplex PCR system has the ability to effectively detect three pathogens in the same tube. The viable pathogens were simultaneously detected for PMA concentrations above 10 μg/ml. The combination of a nylon membrane (15 μm and a micro pore filtration membrane (0.22 μm formed the dual filtration system used to enrich pathogens. The achieved sensitivity of PMA-mPCR based on this dual filtration system was 2.6 × 103 cfu/g for L. monocytogenes, 4.3 × 10 cfu/g for E. coli O157:H7, and 3.1 × 102 cfu/g for S. aureus. Fresh-cut cantaloupe was inoculated with the three target pathogens using concentrations of 103, 102, 10, and 1 cfu/g. After 6-h of enrichment culture, assay sensitivity increased to 1 cfu/g for each of these pathogens. Thus, this technique represents an efficient and rapid detection tool for implementation on fresh-cut cantaloupe.

  6. Antimicrobial treatments to control Listeria monocytogenes in queso fresco.

    Science.gov (United States)

    Lourenço, António; Kamnetz, Mary B; Gadotti, Camila; Diez-Gonzalez, Francisco

    2017-06-01

    Queso fresco, is a Hispanic non-fermented cheese highly susceptible to contamination with L. monocytogenes. This research was aimed to determine the effect of GRAS antimicrobial ingredients to control L. monocytogenes. Antimicrobials included caprylic acid (CA), Nisaplin ® (N, 2.5% nisin), a mixture of sodium lactate and sodium diacetate (SL/SD), Lactococcus lactis sbp. lactis DPC 3147, monolaurin, and lactic acid (LA). Batches of queso fresco curds were inoculated with 10 4  CFU/g and stored at 4 °C for three weeks. During storage the count of L. monocytogenes reached 7 to 8 Log CFU/g in control samples. Most individual antimicrobial treatments resulted in less than 1 Log CFU/g reductions in final counts, with the exception of N (0.5 g/kg) and CA (2.9 g/kg) that caused more than 3 and 5 Log CFU/g differences with controls, respectively. Mixtures of ingredients were more effective in inhibiting L. monocytogenes growth, and treatments with N and CA consistently delivered 6 Log CFU/g less counts than controls. Supplementation of 12 g/kg LA to treatments with SL/SD (3%/0.22%) caused differences of more than 4 Log CFU/g in final Listeria populations. Samples treated with the binary mixtures of N and CA (0.5 and 0.7 g/kg, respectively) were evaluated in a consumer panel (n = 67). Panelists slightly preferred control and commercial over treated samples, but all samples were in average rated between "slightly liking" and "moderately liking." These experiments indicated that combined use of antimicrobial ingredients may be an effective way to control the population of Listeria monocytogenes in queso fresco. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Preliminary stochastic model for managing Vibrio parahaemolyticus and total viable bacterial counts in a Pacific oyster (Crassostrea gigas) supply chain.

    Science.gov (United States)

    Fernandez-Piquer, Judith; Bowman, John P; Ross, Tom; Estrada-Flores, Silvia; Tamplin, Mark L

    2013-07-01

    Vibrio parahaemolyticus can accumulate and grow in oysters stored without refrigeration, representing a potential food safety risk. High temperatures during oyster storage can lead to an increase in total viable bacteria counts, decreasing product shelf life. Therefore, a predictive tool that allows the estimation of both V. parahaemolyticus populations and total viable bacteria counts in parallel is needed. A stochastic model was developed to quantitatively assess the populations of V. parahaemolyticus and total viable bacteria in Pacific oysters for six different supply chain scenarios. The stochastic model encompassed operations from oyster farms through consumers and was built using risk analysis software. Probabilistic distributions and predictions for the percentage of Pacific oysters containing V. parahaemolyticus and high levels of viable bacteria at the point of consumption were generated for each simulated scenario. This tool can provide valuable information about V. parahaemolyticus exposure and potential control measures and can help oyster companies and regulatory agencies evaluate the impact of product quality and safety during cold chain management. If coupled with suitable monitoring systems, such models could enable preemptive action to be taken to counteract unfavorable supply chain conditions.

  8. Bacteriocinogenic Lactococcus lactis subsp. lactis DF04Mi isolated from goat milk: Application in the control of Listeria monocytogenes in fresh Minas-type goat cheese

    Directory of Open Access Journals (Sweden)

    Danielle N. Furtado

    2015-03-01

    Full Text Available Listeria monocytogenes is a pathogen frequently found in dairy products. Its control in fresh cheeses is difficult, due to the psychrotrophic properties and salt tolerance. Bacteriocinogenic lactic acid bacteria (LAB with proven in vitro antilisterial activity can be an innovative technological approach but their application needs to be evaluated by means of in situ tests. In this study, a novel bacteriocinogenic Lactococcus lactis strain (Lc. lactis DF4Mi, isolated from raw goat milk, was tested for control of growth of L. monocytogenes in artificially contaminated fresh Minas type goat cheese during storage under refrigeration. A bacteriostatic effect was achieved, and counts after 10 days were 3 log lower than in control cheeses with no added LAB. However, this effect did not differ significantly from that obtained with a non-bacteriocinogenic Lc. lactis strain. Addition of nisin (12.5 mg/kg caused a rapid decrease in the number of viable L. monocytogenes in the cheeses, suggesting that further studies with the purified bacteriocin DF4Mi may open new possibilities for this strain as biopreservative in dairy products.

  9. Prevalence and antimicrobial susceptibility of Listeria monocytogenes on chicken carcasses in Bandung, Indonesia.

    Science.gov (United States)

    Sugiri, Yoni Darmawan; Gölz, Greta; Meeyam, Tongkorn; Baumann, Maximilian P O; Kleer, Josef; Chaisowwong, Warangkhana; Alter, Thomas

    2014-08-01

    This study was conducted to determine the prevalence and quantify the number of Listeria monocytogenes in fresh chicken carcasses sold in traditional markets and supermarkets in Bandung, West Java, Indonesia, and to determine the antimicrobial resistance patterns of the isolated L. monocytogenes strains. The overall prevalence of L. monocytogenes in chicken carcasses was 15.8% (29/184). When comparing samples from traditional markets and supermarkets, no significant difference in the L. monocytogenes prevalence was detectable (15.2 versus 16.3%). Of the samples, 97.3% had L. monocytogenes counts study were grouped into the molecular serogroup IIb, comprising the serovars 1/2b, 3b, and 7.

  10. Biofilm Formation and Disinfectant Susceptibility of Persistent and Nonpersistent Listeria monocytogenes Isolates from Gorgonzola Cheese Processing Plants.

    Science.gov (United States)

    Costa, Annalisa; Bertolotti, Luigi; Brito, Luisa; Civera, Tiziana

    2016-11-01

    The aim of this study was to investigate whether the biofilm-forming ability and/or the disinfectant susceptibility accounted for the persistence of Listeria monocytogenes in Gorgonzola cheese processing plants. For this purpose, a set of 16 L. monocytogenes isolates collected in the 2004-2007 period was analyzed, including 11 persistent isolates collected in different years, within the collection period, and displaying identical or highly correlated pulsotypes. The evaluation of biofilm-forming ability was assessed using crystal violet (CV) staining and the enumeration of viable cells on stainless steel coupons (SSC). Absorbance values obtained with CV staining for persistent and nonpersistent isolates were not significantly different (rm-ANOVA p > 0.05) and the cell counts from nonpersistent isolates showed to be higher compared with persistent isolates (rm-ANOVA p biofilms on SSC, grown in nutrient-rich (dirty) and limiting (clean) conditions using acid acetic-hydrogen peroxide (P3) and acid citric-hydrogen peroxide (MS) commercial disinfectants. The treatment was considered effective when a 4 Log reduction in viable cell count was observed. The Log reductions of persistent and nonpersistent isolates, obtained with both the assays in clean and dirty conditions, were compared and no significant differences were detected (rm-ANOVA p > 0.05). A greater influence of organic matter on MS could explain why P3 was efficient in reducing to effective levels the majority of the isolates at the lowest concentration suggested by the manufacturer (0.2% [v/v]), while the same purpose required a higher concentration (1% [v/v]) of MS. In conclusion, our results demonstrate that the persistence of these isolates in Gorgonzola cheese processing plants was linked neither to the biofilm-forming ability nor to their susceptibility to hydrogen peroxide-based disinfectants; therefore, other factors should contribute to the persistent colonization of the dairies.

  11. Different methods to quantify Listeria monocytogenesbiofilms cells showed different profile in their viability

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    Lizziane Kretli Winkelströter

    2015-03-01

    Full Text Available Listeria monocytogenes is a foodborne pathogen able to adhere and to form biofilms in several materials commonly present in food processing plants. The aim of this study was to evaluate the resistance of Listeria monocytogenes attached to abiotic surface, after treatment with sanitizers, by culture method, microscopy and Quantitative Real Time Polymerase Chain Reaction (qPCR. Biofilms of L. monocytogenes were obtained in stainless steel coupons immersed in Brain Heart Infusion Broth, under agitation at 37 °C for 24 h. The methods selected for this study were based on plate count, microscopic count with the aid of viability dyes (CTC-DAPI, and qPCR. Results of culture method showed that peroxyacetic acid was efficient to kill sessile L. monocytogenes populations, while sodium hypochlorite was only partially effective to kill attached L. monocytogenes (p < 0.05. When, viability dyes (CTC/DAPI combined with fluorescence microscopy and qPCR were used and lower counts were found after treatments (p < 0.05. Selective quantification of viable cells of L. monocytogenes by qPCR using EMA revelead that the pre-treatment with EMA was not appropriate since it also inhibited amplification of DNA from live cells by ca. 2 log. Thus, the use of CTC counts was the best method to count viable cells in biofilms.

  12. Behavior of Listeria monocytogenes in a multi-species biofilm with Enterococcus faecalis and Enterococcus faecium and control through sanitation procedures.

    Science.gov (United States)

    da Silva Fernandes, Meg; Kabuki, Dirce Yorika; Kuaye, Arnaldo Yoshiteru

    2015-05-04

    The formation of mono-species biofilm (Listeria monocytogenes) and multi-species biofilms (Enterococcus faecium, Enterococcus faecalis, and L. monocytogenes) was evaluated. In addition, the effectiveness of sanitation procedures for the control of the multi-species biofilm also was evaluated. The biofilms were grown on stainless steel coupons at various incubation temperatures (7, 25 and 39°C) and contact times (0, 1, 2, 4, 6 and 8 days). In all tests, at 7°C, the microbial counts were below 0.4 log CFU/cm(2) and not characteristic of biofilms. In mono-species biofilm, the counts of L. monocytogenes after 8 days of contact were 4.1 and 2.8 log CFU/cm(2) at 25 and 39°C, respectively. In the multi-species biofilms, Enterococcus spp. were present at counts of 8 log CFU/cm(2) at 25 and 39°C after 8 days of contact. However, the L. monocytogenes in multi-species biofilms was significantly affected by the presence of Enterococcus spp. and by temperature. At 25°C, the growth of L. monocytogenes biofilms was favored in multi-species cultures, with counts above 6 log CFU/cm(2) after 8 days of contact. In contrast, at 39°C, a negative effect was observed for L. monocytogenes biofilm growth in mixed cultures, with a significant reduction in counts over time and values below 0.4 log CFU/cm(2) starting at day 4. Anionic tensioactive cleaning complemented with another procedure (acid cleaning, disinfection or acid cleaning+disinfection) eliminated the multi-species biofilms under all conditions tested (counts of all micro-organismsbiofilms under all tested conditions (counts of the all microorganisms biofilms under all the test conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Listeria monocytogenes switches from dissemination to persistence by adopting a vacuolar lifestyle in epithelial cells

    Science.gov (United States)

    Mitchell, Gabriel

    2017-01-01

    Listeria monocytogenes causes listeriosis, a foodborne disease that poses serious risks to fetuses, newborns and immunocompromised adults. This intracellular bacterial pathogen proliferates in the host cytosol and exploits the host actin polymerization machinery to spread from cell-to-cell and disseminate in the host. Here, we report that during several days of infection in human hepatocytes or trophoblast cells, L. monocytogenes switches from this active motile lifestyle to a stage of persistence in vacuoles. Upon intercellular spread, bacteria gradually stopped producing the actin-nucleating protein ActA and became trapped in lysosome-like vacuoles termed Listeria-Containing Vacuoles (LisCVs). Subpopulations of bacteria resisted degradation in LisCVs and entered a slow/non-replicative state. During the subculture of host cells harboring LisCVs, bacteria showed a capacity to cycle between the vacuolar and the actin-based motility stages. When ActA was absent, such as in ΔactA mutants, vacuolar bacteria parasitized host cells in the so-called “viable but non-culturable” state (VBNC), preventing their detection by conventional colony counting methods. The exposure of infected cells to high doses of gentamicin did not trigger the formation of LisCVs, but selected for vacuolar and VBNC bacteria. Together, these results reveal the ability of L. monocytogenes to enter a persistent state in a subset of epithelial cells, which may favor the asymptomatic carriage of this pathogen, lengthen the incubation period of listeriosis, and promote bacterial survival during antibiotic therapy. PMID:29190284

  14. Effect of benzalkonium chloride on viability and energy metabolism in exponential- and stationary-growth-phase cells of Listeria monocytogenes.

    Science.gov (United States)

    Luppens, S B; Abee, T; Oosterom, J

    2001-04-01

    The difference in killing exponential- and stationary-phase cells of Listeria monocytogenes by benzalkonium chloride (BAC) was investigated by plate counting and linked to relevant bioenergetic parameters. At a low concentration of BAC (8 mg liter(-1)), a similar reduction in viable cell numbers was observed for stationary-phase cells and exponential-phase cells (an approximately 0.22-log unit reduction), although their membrane potential and pH gradient were dissipated. However, at higher concentrations of BAC, exponential-phase cells were more susceptible than stationary-phase cells. At 25 mg liter(-1), the difference in survival on plates was more than 3 log units. For both types of cells, killing, i.e., more than 1-log unit reduction in survival on plates, coincided with complete inhibition of acidification and respiration and total depletion of ATP pools. Killing efficiency was not influenced by the presence of glucose, brain heart infusion medium, or oxygen. Our results suggest that growth phase is one of the major factors that determine the susceptibility of L. monocytogenes to BAC.

  15. Effect of sodium alginate coating incorporated with nisin, Cinnamomum zeylanicum, and rosemary essential oils on microbial quality of chicken meat and fate of Listeria monocytogenes during refrigeration.

    Science.gov (United States)

    Raeisi, Mojtaba; Tabaraei, Alijan; Hashemi, Mohammad; Behnampour, Nasser

    2016-12-05

    The present study was conducted to preserve the microbial quality of chicken meat fillets during storage time by using sodium alginate active coating solutions incorporated with different natural antimicrobials including nisin, Cinnamomum zeylanicum (cinnamon), and rosemary essential oils (EOs) which were added individually and in combination. The samples were stored in refrigeration condition for 15days and were analyzed for total viable count, Enterobacteriaceae count, lactic acid bacteria count, Pseudomonas spp. count, psychrotrophic count, and yeast and mold count, as well as fate of inoculated Listeria monocytogenes at 3-day intervals. Results indicated that values of tested microbial indicators in all samples increased during storage. Antimicrobial agents, when used in combination, had stronger effect in preserving the microbial quality of chicken meat samples rather than their individual use and the strongest effect was observed in samples coated with alginate solution containing both cinnamon and rosemary EOs (CEO+REO). However, all treatments significantly inhibited microbial growth when compared to the control (Ppreservatives is recommended in meat products especially in chicken meats. Copyright © 2016. Published by Elsevier B.V.

  16. Impact of environmental factors on the culturability and viability of Listeria monocytogenes under conditions encountered in food processing plants.

    Science.gov (United States)

    Overney, Anaïs; Jacques-André-Coquin, Joséphine; Ng, Patricia; Carpentier, Brigitte; Guillier, Laurent; Firmesse, Olivier

    2017-03-06

    The ability of Listeria monocytogenes to adhere to and persist on surfaces for months or even years may be responsible for its transmission from contaminated surfaces to food products. Hence the necessity to find effective means to prevent the establishment of L. monocytogenes in food processing environments. The aim of this study was to assess, through a fractional experimental design, the environmental factors that could affect the survival of L. monocytogenes cells on surfaces to thereby prevent the persistence of this pathogen in conditions mimicking those encountered in food processing plants: culture with smoked salmon juice or meat exudate, use of two materials with different hygiene status, biofilm of L. monocytogenes in pure-culture or dual-culture with a Pseudomonas fluorescens strain, application of a drying step after cleaning and disinfection (C&D) and comparison of two strains of L. monocytogenes. Bacterial survival was assessed by culture, qPCR to quantify total cells, and propidium monoazide coupled with qPCR to quantify viable cells and highlight viable but non-culturable (VBNC) cells. Our results showed that failure to apply C&D causes cell persistence on surfaces. Moreover, the sanitation procedure leads only to a loss of culturability and appearance of VBNC populations. However, an additional daily drying step after C&D optimises the effectiveness of these procedures to reduce culturable populations. Our results reinforce the importance to use molecular tools to monitor viable pathogens in food processing plants to avoid underestimating the amounts of cells using only methods based on cell culture. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Inactivation of Listeria monocytogenes in milk by pulsed electric field.

    Science.gov (United States)

    Reina, L D; Jin, Z T; Zhang, Q H; Yousef, A E

    1998-09-01

    Pasteurized whole, 2%, and skim milk were inoculated with Listeria monocytogenes Scott A and treated with high-voltage pulsed electric field (PEF). The effects of milk composition (fat content) and PEF parameters (electric field strength, treatment time, and treatment temperature) on the inactivation of the bacterium were studied. No significant differences were observed in the inactivation of L. monocytogenes Scott A in three types of milk by PEF treatment. With treatment at 25 degrees C, 1- to 3-log reductions of L. monocytogenes were observed. PEF lethal effect was a function of field strength and treatment time. Higher field strength or longer treatment time resulted in a greater reduction of viable cells. A 4-log reduction of the bacterium was obtained by increasing the treatment temperature to 50 degrees C. Results indicate that the use of a high-voltage PEF is a promising technology for inactivation of foodborne pathogens.

  18. Comparison of viable plate count, turbidity measurement and real-time PCR for quantification of Porphyromonas gingivalis.

    Science.gov (United States)

    Clais, S; Boulet, G; Van Kerckhoven, M; Lanckacker, E; Delputte, P; Maes, L; Cos, P

    2015-01-01

    The viable plate count (VPC) is considered as the reference method for bacterial enumeration in periodontal microbiology but shows some important limitations for anaerobic bacteria. As anaerobes such as Porphyromonas gingivalis are difficult to culture, VPC becomes time-consuming and less sensitive. Hence, efficient normalization of experimental data to bacterial cell count requires alternative rapid and reliable quantification methods. This study compared the performance of VPC with that of turbidity measurement and real-time PCR (qPCR) in an experimental context using highly concentrated bacterial suspensions. Our TaqMan-based qPCR assay for P. gingivalis 16S rRNA proved to be sensitive and specific. Turbidity measurements offer a fast method to assess P. gingivalis growth, but suffer from high variability and a limited dynamic range. VPC was very time-consuming and less repeatable than qPCR. Our study concludes that qPCR provides the most rapid and precise approach for P. gingivalis quantification. Although our data were gathered in a specific research context, we believe that our conclusions on the inferior performance of VPC and turbidity measurements in comparison to qPCR can be extended to other research and clinical settings and even to other difficult-to-culture micro-organisms. Various clinical and research settings require fast and reliable quantification of bacterial suspensions. The viable plate count method (VPC) is generally seen as 'the gold standard' for bacterial enumeration. However, VPC-based quantification of anaerobes such as Porphyromonas gingivalis is time-consuming due to their stringent growth requirements and shows poor repeatability. Comparison of VPC, turbidity measurement and TaqMan-based qPCR demonstrated that qPCR possesses important advantages regarding speed, accuracy and repeatability. © 2014 The Society for Applied Microbiology.

  19. Effect of Filling Type and Heating Method on Prevalence of Listeria species and Listeria monocytogenes in Dumplings Produced in Poland.

    Science.gov (United States)

    Szymczak, Barbara; Dąbrowski, Waldemar

    2015-05-01

    The count of Listeria monocytogenes was determined, before and after heat treatment, in 200 samples of dumplings of 9 brands and with different types of stuffing. Analyses were conducted according to ISO 11290-1 standard and with real-time PCR method. The highest count of L. monocytogenes was found in meat dumplings (10(2) to 10(4) CFU/g), whereas products with white cheese-potato stuffing and vegetable-mushroom stuffing contained significantly less Listeria, 20 to 80 and 5 to 32 CFU/g, respectively. In cooled meat dumplings the extent of contamination depended significantly on the producer. In addition, a significant (P monocytogenes in meat dumplings. In contrast, the microwave heating applied for 2 min at 600 W only reduced the count of L. monocytogenes by 1 to 2 logs. Hence, the microwave heating failed to reduce the risk of infection with this pathogen below the level permissible in the EU regulation, especially in the most contaminated samples. In this case, the efficacy of microwave heating was significantly (P monocytogenes (rho = 0.626), then by meat content in the stuffing (0.476), and to the lowest extent--by the type of meat (0.415 to 0.425). However, no Listeria sp. and L. monocytogenes were isolated from cooked dumplings with fruits (strawberries or blueberries). © 2015 Institute of Food Technologists®

  20. Efficacy of household washing treatments for the control of Listeria monocytogenes on salad vegetables.

    Science.gov (United States)

    Nastou, Aikaterini; Rhoades, Jonathan; Smirniotis, Petros; Makri, Ioanna; Kontominas, Michael; Likotrafiti, Eleni

    2012-10-15

    The efficacy of household decontamination methods at reducing Listeria monocytogenes on fresh lettuce (Lactuca sativa), cucumber (Cucumis sativus) and parsley (Petroselinum sativum) was studied. Inoculated vegetable pieces were immersed in washing solutions and surviving L. monocytogenes enumerated. Parameters investigated were storage temperature prior to washing, dipping water temperature, agitation, acetic acid concentration and immersion time. The results indicated that the storage temperature significantly affects the efficacy of dipping vegetables in water for the control of L. monocytogenes, as the reduction in count was greatest when products had been stored at cooler temperatures. Decontamination with acetic acid (up to 2.0% v/v) was shown to have some effect in most cases, but the highest observed decrease in count was 2.6 log cfu/g. Experiments investigating the effect of exposure time to acetic acid (0.5% and 1.0% v/v, up to 30 min immersion) indicated that immersing the vegetables for more than 10 min is of minimal benefit. The most significant factor affecting washing and decontamination efficacy was the vegetable itself: L. monocytogenes colonizing cucumber epidermis was far more resistant to removal by washing and to acid treatment than that on the leafy vegetables, and L. monocytogenes on parsley was the most susceptible. This shows that published decontamination experiments (often performed with lettuce) cannot necessarily be extrapolated to other vegetables. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Bifidobacterium breve IPLA20005 affects in vitro the expression of hly and luxS genes, related to the virulence of Listeria monocytogenes Lm23.

    Science.gov (United States)

    Rios-Covian, David; Nogacka, Alicja; Salazar, Nuria; Hernández-Barranco, A M; Cuesta, Isabel; Gueimonde, Miguel; de Los Reyes Gavilán, Clara G

    2018-03-01

    Mechanistic features that characterize the interaction and inhibition of the food-borne pathogen Listeria monocytogenes by members of the genus Bifidobacterium still remain unclear. In the present work, we tried to shed light on the influence that co-cultivation of L. monocytogenes with Bifidobacterium breve may exert on both microorganisms and on virulence of the pathogen. Production of acetate and lactate was measured by gas chromatography and high-performance liquid chromatography, respectively; bacterial counts were obtained by plate count; gene expression was determined by RT-qPCR; and haemolytic activity was analyzed against goat erythrocytes. We found slightly but significantly lower final counts of Listeria and Bifidobacterium (p monocytogenes cells from cocultures than in those from monocultures. In contrast, the hly and luxS genes, which code for the cytolysin listeriolysin O and participate in biofilm formation, respectively, were overexpressed when L. monocytogenes was grown in coculture. This indicates that the presence of Bifidobacterium is able to modify the gene expression and haemolytic activity of L. monocytogenes when both microorganisms grow together.

  2. Assay of enterocin AS-48 for inhibition of foodborne pathogens in desserts.

    Science.gov (United States)

    Martinez Viedma, Pilar; Abriouel, Hikmate; Ben Omar, Nabil; Lucas López, Rosario; Valdivia, Eva; Gálvez, Antonio

    2009-08-01

    Enterocin AS-48 was tested against Staphylococcus aureus, Bacillus cereus, and Listeria monocytogenes in different kinds of desserts. The highest activity against S. aureus was detected in baker cream. However, in yogurt-type soy-based desserts and in gelatin pudding, AS-48 (175 arbitrary units [AU]/g) reduced viable cell counts of S. aureus by only 1.5 to 1.8 log units at most. The efficacy of AS-48 in puddings greatly depended on inoculum size, and viable S. aureus counts decreased below detection levels within 24 h for inocula lower than 4 to 5.5 log CFU/g. For L. monocytogenes, bacteriocin concentrations of 52.5 to 87.5 AU/g reduced viable counts below detection levels and avoided regrowth of survivors. The lowest activity was detected in yogurt-type desserts. For B. cereus, viable cell counts were reduced below detection levels for bacteriocin concentrations of 52.5 AU/g in instant pudding without soy or by 175 AU/g in the soy pudding. In gelatin pudding, AS-48 (175 AU/g) reduced viable cell counts of B. cereus below detection levels after 8 h at 10 degrees C or after 48 h at 22 degrees C. Bacteriocin addition also inhibited gelatin liquefaction caused by the proteolytic activity of B. cereus.

  3. Sensitivity of Listeria monocytogenes to irradiation

    International Nuclear Information System (INIS)

    Tarjan, Veronika

    1990-01-01

    Irradiation of Listeria monocytogenes (L.m.) was carried out in culture media and pork meat paste at room temperature with 60 Co radiation source of 6.6 kGy h -1 dose rate. The employed doses were 0, 0.5, 1, 2, 3, 4 and 6 kGy. One strain out of 3 survived as high as 4 kGy irradiation. Radiation with 2 kGy resulted 7 log cycles reduction of cell count. After lower irradiation doses the L.m. count decreased in proportion to increasing doses. It has been concluded that L.m. compared with Gram-negative pathogens, are less sensitive to irradiation. (author) 6 refs.; 4 figs

  4. Designing primers and evaluation of the efficiency of propidium monoazide – Quantitative polymerase chain reaction for counting the viable cells of Lactobacillus gasseri and Lactobacillus salivarius

    Directory of Open Access Journals (Sweden)

    Chieh-Hsien Lai

    2017-07-01

    Full Text Available The purpose of this study is to evaluate the efficiency of using propidium monoazide (PMA real-time quantitative polymerase chain reaction (qPCR to count the viable cells of Lactobacillus gasseri and Lactobacillus salivarius in probiotic products. Based on the internal transcription spacer and 23S rRNA genes, two primer sets specific for these two Lactobacillus species were designed. For a probiotic product, the total deMan Rogosa Sharpe plate count was 8.65±0.69 log CFU/g, while for qPCR, the cell counts of L. gasseri and L. salivarius were 8.39±0.14 log CFU/g and 8.57±0.24 log CFU/g, respectively. Under the same conditions, for its heat-killed product, qPCR counts for L. gasseri and L. salivarius were 6.70±0.16 log cells/g and 7.67±0.20 log cells/g, while PMA-qPCR counts were 5.33±0.18 log cells/g and 5.05±0.23 log cells/g, respectively. For cell dilutions with a viable cell count of 8.5 log CFU/mL for L. gasseri and L. salivarius, after heat killing, the PMA-qPCR count for both Lactobacillus species was near 5.5 log cells/mL. When the PMA-qPCR counts of these cell dilutions were compared before and after heat killing, although some DNA might be lost during the heat killing, significant qPCR signals from dead cells, i.e., about 4–5 log cells/mL, could not be reduced by PMA treatment. Increasing PMA concentrations from 100 μM to 200 μM or light exposure time from 5 minutes to 15 minutes had no or, if any, only minor effect on the reduction of qPCR signals from their dead cells. Thus, to differentiate viable lactic acid bacterial cells from dead cells using the PMA-qPCR method, the efficiency of PMA to reduce the qPCR signals from dead cells should be notable.

  5. Designing primers and evaluation of the efficiency of propidium monoazide - Quantitative polymerase chain reaction for counting the viable cells of Lactobacillus gasseri and Lactobacillus salivarius.

    Science.gov (United States)

    Lai, Chieh-Hsien; Wu, Sih-Rong; Pang, Jen-Chieh; Ramireddy, Latha; Chiang, Yu-Cheng; Lin, Chien-Ku; Tsen, Hau-Yang

    2017-07-01

    The purpose of this study is to evaluate the efficiency of using propidium monoazide (PMA) real-time quantitative polymerase chain reaction (qPCR) to count the viable cells of Lactobacillus gasseri and Lactobacillus salivarius in probiotic products. Based on the internal transcription spacer and 23S rRNA genes, two primer sets specific for these two Lactobacillus species were designed. For a probiotic product, the total deMan Rogosa Sharpe plate count was 8.65±0.69 log CFU/g, while for qPCR, the cell counts of L. gasseri and L. salivarius were 8.39±0.14 log CFU/g and 8.57±0.24 log CFU/g, respectively. Under the same conditions, for its heat-killed product, qPCR counts for L. gasseri and L. salivarius were 6.70±0.16 log cells/g and 7.67±0.20 log cells/g, while PMA-qPCR counts were 5.33±0.18 log cells/g and 5.05±0.23 log cells/g, respectively. For cell dilutions with a viable cell count of 8.5 log CFU/mL for L. gasseri and L. salivarius, after heat killing, the PMA-qPCR count for both Lactobacillus species was near 5.5 log cells/mL. When the PMA-qPCR counts of these cell dilutions were compared before and after heat killing, although some DNA might be lost during the heat killing, significant qPCR signals from dead cells, i.e., about 4-5 log cells/mL, could not be reduced by PMA treatment. Increasing PMA concentrations from 100 μM to 200 μM or light exposure time from 5 minutes to 15 minutes had no or, if any, only minor effect on the reduction of qPCR signals from their dead cells. Thus, to differentiate viable lactic acid bacterial cells from dead cells using the PMA-qPCR method, the efficiency of PMA to reduce the qPCR signals from dead cells should be notable. Copyright © 2016. Published by Elsevier B.V.

  6. Listeria monocytogenes in Food-Processing Facilities, Food Contamination, and Human Listeriosis: The Brazilian Scenario.

    Science.gov (United States)

    Camargo, Anderson Carlos; Woodward, Joshua John; Call, Douglas Ruben; Nero, Luís Augusto

    2017-11-01

    Listeria monocytogenes is a foodborne pathogen that contaminates food-processing environments and persists within biofilms on equipment, utensils, floors, and drains, ultimately reaching final products by cross-contamination. This pathogen grows even under high salt conditions or refrigeration temperatures, remaining viable in various food products until the end of their shelf life. While the estimated incidence of listeriosis is lower than other enteric illnesses, infections caused by L. monocytogenes are more likely to lead to hospitalizations and fatalities. Despite the description of L. monocytogenes occurrence in Brazilian food-processing facilities and foods, there is a lack of consistent data regarding listeriosis cases and outbreaks directly associated with food consumption. Listeriosis requires rapid treatment with antibiotics and most drugs suitable for Gram-positive bacteria are effective against L. monocytogenes. Only a minority of clinical antibiotic-resistant L. monocytogenes strains have been described so far; whereas many strains recovered from food-processing facilities and foods exhibited resistance to antimicrobials not suitable against listeriosis. L. monocytogenes control in food industries is a challenge, demanding proper cleaning and application of sanitization procedures to eliminate this foodborne pathogen from the food-processing environment and ensure food safety. This review focuses on presenting the L. monocytogenes distribution in food-processing environment, food contamination, and control in the food industry, as well as the consequences of listeriosis to human health, providing a comparison of the current Brazilian situation with the international scenario.

  7. Suppression of Listeria monocytogenes by the Native Micro-Flora in Teewurst Sausage.

    Science.gov (United States)

    Austin-Watson, Clytrice; Grant, Ar'Quette; Brice, Michline

    2013-10-21

    Modern consumers are interested in the use of non-chemical methods to control pathogens when heat sterilization is not an option. Such is the case with teewurst sausage, a raw spreadable sausage and a popular German commodity. Although Listeria was not found in teewurst, the optimal microbial growing conditions of teewurst coupled with the ubiquity of L. monocytogenes in nature, makes the possibility of contamination of products very possible. This pilot study was conducted to examine teewurst's native micro-flora's ability to suppress the outgrowth of L. monocytogenes at 10 °C using standard plate counts and PCR-DGGE. Traditional plating methods showed L. monocytogenes growth significantly decreased when in competition with the teewurst's native micro-flora ( p flora of the teewurst suppressed the overall growth of L. monocytogenes by an average of two logs, under these conditions. Denaturing Gradient Gel Electrophoresis (DGGE) amplicons with unique banding patterns were extracted from DGGE gel for identification. Brochothrix thermosphacta and Lactobacillus curvatus were identified as a part of the teewurst's native micro-flora. Although the native micro-flora did not decrease L. monocytogenes to below limits of detection, it was enough of a decrease to warrant further investigation.

  8. Survival of bioluminescent Listeria monocytogenes and Escherichia coli O157:H7 in soft cheeses.

    Science.gov (United States)

    Ramsaran, H; Chen, J; Brunke, B; Hill, A; Griffiths, M W

    1998-07-01

    Pasteurized and raw milks that had been inoculated at 10(4) cfu/ml with bioluminescent strains of Listeria monocytogenes and Escherichia coli O157:H7 were used in the manufacture of Camembert and Feta cheeses with or without nisin-producing starter culture. Survival of both organisms was determined during the manufacture and storage of Camembert and Feta cheeses at 2 +/- 1 degree C for 65 and 75 d, respectively. Bacterial bioluminescence was used as an indicator to enumerate the colonies plated on selective Listeria agar and on MacConkey agar. Escherichia coli O157:H7 survived the manufacturing process of both cheeses and was present at the end of the storage period in greater numbers than in the initial inoculum. At the end of 75 d of storage, E. coli O157:H7 was found in the brine of Feta cheese. The counts of L. monocytogenes increased as the pH of the Camembert cheese increased, and there were significant differences between the counts from samples taken from the inside and the counts from samples obtained near the surface of the cheese. The Feta cheese that contained nisin was the only cheese in which L. monocytogenes was at the level of the initial inoculum after 75 d of storage.

  9. The influence of Listeria monocytogenes cells on the primary immunologic response in irradiated mice

    International Nuclear Information System (INIS)

    Borowski, J.; Jokoniuk, P.

    1977-01-01

    The influence of killed Listeria monocytogenes cells on the primary immunologic response in mice irradiated with 300 or 500 R was studied. The immunologic response of the mice to sheep red blood cells used as antigen was assessed at the cellular level (by counting PFC) and humoral level. Injection of killed Listeria monocytogenes cells before irradiation of the mice diminished the immunosuppressive effect of roentgen radiation. Injection of the cells after irradiation accelerated regeneration of immunologic reactivity in the irradiated mice. (author)

  10. Prevalence and serotype distribution of Listeria monocytogenes isolated from foods in Montevideo-Uruguay

    Directory of Open Access Journals (Sweden)

    Valeria Braga

    Full Text Available ABSTRACT The aim of this work was to study the prevalence of Listeria monocytogenes in foods obtained in retail shops and food industries located in Montevideo-Uruguay, and to identify the serogroups of the obtained isolates. Three-thousand one-hundred and seventy-five food samples (frozen, deli meats, ready-to-eat and cheese were analyzed. The obtained isolates were serogrouped by multiplex PCR and serotyped by conventional procedure. Genetic comparisons were performed using pulsed-field gel electrophoresis on a sub-set of isolates belonging to the same serotype successively recovered from the same establishment. L. monocytogenes was isolated from 11.2% of samples. The highest prevalence was observed in frozen foods (38%, followed by cheese (10%. 1/2b and 4b were the most frequently identified serotypes. In six of 236 analyzed establishments we successively recovered L. monocytogenes isolates belonging to the same serotype. Most of them corresponded to serotype 1/2b. Pulsed-field gel electrophoresis profiles suggest that at least 33% of L. monocytogenes 1/2b isolates are genetically related and that may remain viable for prolonged periods. The observed prevalence of L. monocytogenes was lower than reported in neighboring countries. Our findings highlight the role that frozen foods may play in the spread of this pathogen, and the relevance of serotypes 1/2b and 4b.

  11. Effects of irradiation on bacterial load and Listeria monocytogenes in raw chicken

    International Nuclear Information System (INIS)

    Varabioff, Y.; Mitchell, G.E.; Nottingham, S.M.

    1992-01-01

    After irradiation of chickens to a dose of 2.5 kGy, the decrease in the standard plate count (SPC) was similar in air and in vacuum-packaged chickens. During storage at 4 degrees C for 15 d, the SPC increased progressively in both types of packaged chickens. At the end of the storage period, the SPC was higher in air-packaged chicken than in vacuum-packaged chickens. In irradiated chickens, Listeria monocytogenes was only recovered from the vacuum-packaged chickens after 7 d cold storage. In unirradiated chickens, L. monocytogenes proliferated similarly in both air- and vacuum-packaged chickens

  12. Suppression of Listeria monocytogenes by the Native Micro-Flora in Teewurst Sausage

    Directory of Open Access Journals (Sweden)

    Michline Brice

    2013-10-01

    Full Text Available Modern consumers are interested in the use of non-chemical methods to control pathogens when heat sterilization is not an option. Such is the case with teewurst sausage, a raw spreadable sausage and a popular German commodity. Although Listeria was not found in teewurst, the optimal microbial growing conditions of teewurst coupled with the ubiquity of L. monocytogenes in nature, makes the possibility of contamination of products very possible. This pilot study was conducted to examine teewurst’s native micro-flora’s ability to suppress the outgrowth of L. monocytogenes at 10 °C using standard plate counts and PCR-DGGE. Traditional plating methods showed L. monocytogenes growth significantly decreased when in competition with the teewurst’s native micro-flora (p < 0.05. The native micro-flora of the teewurst suppressed the overall growth of L. monocytogenes by an average of two logs, under these conditions. Denaturing Gradient Gel Electrophoresis (DGGE amplicons with unique banding patterns were extracted from DGGE gel for identification. Brochothrix thermosphacta and Lactobacillus curvatus were identified as a part of the teewurst’s native micro-flora. Although the native micro-flora did not decrease L. monocytogenes to below limits of detection, it was enough of a decrease to warrant further investigation.

  13. Listeria monocytogenes strains show large variations in competitive growth in mixed culture biofilms and suspensions with bacteria from food processing environments.

    Science.gov (United States)

    Heir, Even; Møretrø, Trond; Simensen, Andreas; Langsrud, Solveig

    2018-06-20

    Interactions and competition between resident bacteria in food processing environments could affect their ability to survive, grow and persist in microhabitats and niches in the food industry. In this study, the competitive ability of L. monocytogenes strains grown together in separate culture mixes with other L. monocytogenes (L. mono mix), L. innocua (Listeria mix), Gram-negative bacteria (Gram- mix) and with a multigenera mix (Listeria + Gram- mix) was investigated in biofilms on stainless steel and in suspensions at 12 °C. The mixed cultures included resident bacteria from processing surfaces in meat and salmon industry represented by L. monocytogenes (n = 6), L. innocua (n = 5) and Gram-negative bacteria (n = 6; Acinetobacter sp., Pseudomonas fragi, Pseudomonas fluorescens, Serratia liquefaciens, Stenotrophomonas maltophilia). Despite hampered in growth in mixed cultures, L. monocytogenes established in biofilms with counts at day nine between 7.3 and 9.0 log per coupon with the lowest counts in the Listeria + G- mix that was dominated by Pseudomonas. Specific L. innocua inhibited growth of L. monocytogenes strains differently; inhibition that was further enhanced by the background Gram-negative microbiota. In these multispecies and multibacteria cultures, the growth competitive effects lead to the dominance of a strong competitor L. monocytogenes strain that was only slightly inhibited by L. innocua and showed strong competitive abilities in mixed cultures with resident Gram-negative bacteria. The results indicates complex patterns of bacterial interactions and L. monocytogenes inhibition in the multibacteria cultures that only partially depend on cell contact and likely involve various antagonistic and bacterial tolerance mechanisms. The study indicates large variations among L. monocytogenes in their competitiveness under multibacterial culture conditions that should be considered in further studies towards understanding of L

  14. Growth potential of Listeria monocytogenes in sliced turkey bresaola packed in modified atmosphere

    Directory of Open Access Journals (Sweden)

    Elena Dalzini

    2014-02-01

    Full Text Available According to EC Regulation No 2073/2005, for food business operators that produce ready-to-eat (RTE product, it is crucial to be able to demonstrate if the product supports the growth of Listeria monocytogenes. The objective of the study was therefore to evaluate the behaviour of L. monocytogenes in sliced RTE turkey bresaola (made by cured turkey breast 4.5% NaCl, 1% sodium lactate, sodium nitrite 150 ppm and flavouring during the shelf life of the product, simulating a contamination during the slicing operation. Considering a shelf life of 90 days, as defined by manufacturer, the packages of sliced bresaola were stored at 5°C for 7 days and at 8°C for the remaining storage time (83 days. L. monocytogenes count decreased during storage test from 1.43/1.98 log cfu/g in the three batches tested to 1.03 log cfu/g in one batch and to undetectable levels in the other two batches. The results show that the investigated product is unable to support the growth of L. monocytogenes.

  15. Inhibitory Effect of Nisin on Listeria monocytogenes Inoculated into Surimi and Minced Meat

    Directory of Open Access Journals (Sweden)

    Masoud Rezaei

    2012-02-01

    Full Text Available Background & Objective: Listeria monocytogenes has already established as an important food born pathogen which induce listeriosis in human. Use of bacteriocins to provide food safety has been increased dramatically. Nisin has a wide spectrum inhibitory effect than the other bacteriocins and inhibits food-borne pathogens such as L. monocytogenes and many other Gram-positive spoilage microorganisms. The purpose of this study was to investigate the inhibitory effect of Nisin on population of Listeria monocytogenes and the role of changes in food components on the antilisterial properties of Nisin. Materials & Methods: The minced meat and surimi samples were inoculated by 1×104 cfu/g of L. monocytogenes. Then samples exposed to Nisin at the levels of 500 or 1000 IU/g were prepared. All treatments after packaging in plastic bags were kept for 12 days at refrigerator temperature. Samples were cultured on CHROMagarTM Listeria every 2 days and the number of listeria monocytogenes was counted. Results: two different concentrations of Nisin (500 or 1000 IU/g was not able to inhibit L. monocytogenes below the acceptable level for raw food (100 cells per g in minced meat and surimi of silver carp. But the number of bacteria reduces more in fish surimi as compared to the mince meal. Also, antilisterial activity of Nisin was reduced during the storage period. Conclusion: Inhibitory property of Nisin against L. monocytogenes in surimi significantly was higher than the minced (P<0.05. So it is possible the antilisterial properties of Nisin will increase by elimination of some enzymes during processing.

  16. Spatiotemporal Dynamics of Total Viable Vibrio spp. in a NW Mediterranean Coastal Area.

    Science.gov (United States)

    Girard, Léa; Peuchet, Sébastien; Servais, Pierre; Henry, Annabelle; Charni-Ben-Tabassi, Nadine; Baudart, Julia

    2017-09-27

    A cellular approach combining Direct Viable Counting and Fluorescent In Situ Hybridization using a one-step multiple-probe technique and Solid Phase Cytometry (DVC-FISH-SPC) was developed to monitor total viable vibrios and cover the detection of a large diversity of vibrios. FISH combined three probes in the same assay and targeted sequences located at different positions on the 16S rRNA of Vibrio and Aliivibrio members. We performed a 10-month in situ study to investigate the weekly dynamics of viable vibrios relative to culturable counts at two northwestern Mediterranean coastal sites, and identified the key physicochemical factors for their occurrence in water using a multivariate analysis. Total viable and culturable cell counts showed the same temporal pattern during the warmer season, whereas the ratios between both methods were inverted during the colder seasons (<15°C), indicating that some of the vibrio community had entered into a viable but non-culturable (VBNC) state. We confirmed that Seawater Surface Temperature explained 51-62% of the total variance in culturable counts, and also showed that the occurrence of viable vibrios is controlled by two variables, pheopigment (15%) and phosphate (12%) concentrations, suggesting that other unidentified factors play a role in maintaining viability.

  17. Purification of leucocin A for use on wieners to inhibit Listeria monocytogenes in the presence of spoilage organisms.

    Science.gov (United States)

    Balay, Danielle R; Dangeti, Ramana V; Kaur, Kamaljit; McMullen, Lynn M

    2017-08-16

    The aims of this study were to improve the method for purification of leucocin A to increase yield of peptide and to evaluate the efficacy of leucocin A and an analogue of leucocin A (leucocin N17L) to inhibit the growth of Listeria monocytogenes on wieners in the presence of spoilage organisms. Leucocin A was produced by Leuconostoc gelidum UAL187 and purified with a five-fold increase in yield; leucocin N17L was synthesized replacing asparagine at residue 17 with leucine. Five strains of L. monocytogenes associated with foodborne illness were used to assess bacteriocin efficacy in vitro and in situ. Minimum inhibitory concentrations could not be determined in broth; however, on agar the minimum inhibitory concentrations ranged from 11.7-62.5μM and 62.5->500μM for leucocin A and leucocin N17L, respectively. Leucocin N17L was less effective than the native bacteriocin at controlling the growth of L. monocytogenes. The inactivation profiles of L. monocytogenes in broth in the presence of leucocin A suggested each isolate had different levels of resistance to the bacteriocin as determined by the initial bactericidal effect. The formation of spontaneously resistance subpopulations were also observed for each strain of L. monocytogenes. In situ, wieners were inoculated with the spoilage organisms, Carnobacterium divergens and Brochothrix thermosphacta, followed by surface application of purified leucocin A, and inoculated with a cocktail of L. monocytogenes. Wieners were vacuum packaged and stored at 7°C for 16d. Leucocin A reduced the counts L. monocytogenes on wieners during storage, regardless of the presence of C. divergens. B. thermosphacta was unaffected by the presence of leucocin A on wieners over the duration of storage. This study suggests that leucocin A may be beneficial to industry as a surface application on wieners to help reduce L. monocytogenes counts due to post-processing contamination even in the presence of spoilage organisms. However, further

  18. Efficacy of ultraviolet light exposure against survival of Listeria monocytogenes on conveyor belts.

    Science.gov (United States)

    Morey, Amit; McKee, Shelly R; Dickson, James S; Singh, Manpreet

    2010-06-01

    Listeria monocytogenes has been repeatedly isolated from foods and food-processing facilities including food contact surfaces such as conveyor belts (CB). CBs are often difficult to clean and require rigorous sanitation programs for decontamination. Ultraviolet (UV) light has exhibited microbicidal properties on food contact surfaces and this study was conducted to determine the efficacy of UV against L. monocytogenes on CB made of different materials. A four-strain cocktail of L. monocytogenes (serotypes 3A, 4A, 4B, and 4C) was made to give a suspension of approximately 10(7) CFU/mL. CBs made from four different types of materials, (1) Ropanyl DM 8/2 A2 + 04 (belt 1), (2) Volta FRMW-3.0 (belt 2), (3) Volta FRMB-3.0 (belt 3), and (4) Ropanyl DM (belt 4), were inoculated with 1 mL of the four-strain cocktail (approximately 10(7) CFU/mL) of the bacterial suspension. CBs were treated with UV light (254 nm) for 1 and 3 sec at 5.53 and 5.95 mW/cm(2). Three replications of the experiments were conducted. Two-way analysis of variance of survival populations of L. monocytogenes showed that bacterial counts were significantly reduced (p belt types irrespective of UV light intensities and times of exposure. L. monocytogenes populations were reduced (p belts 1, 2, and 3 after exposure to 5.95 mW/cm(2) UV light intensity for 3 sec. L. monocytogenes-inoculated CBs that were exposed to 5.53 mW/cm(2) showed higher (p Belt 4 showed survival populations of L. monocytogenes ranging from 1.42 to 1.73 log(10) CFU/cm(2) after UV light treatment for 1 and 3 sec. UV light can be effectively used to reduce L. monocytogenes contamination on CBs.

  19. Assessing the capacity of growth, survival, and acid adaptive response of Listeria monocytogenes during storage of various cheeses and subsequent simulated gastric digestion.

    Science.gov (United States)

    Kapetanakou, Anastasia E; Gkerekou, Maria A; Vitzilaiou, Eirini S; Skandamis, Panagiotis N

    2017-04-04

    Different physicochemical and microbiological characteristics of cheeses may affect Listeria monocytogenes potential to grow, survive, or exhibit an acid adaptive response during storage and digestion. The objectives of the present study were to assess: i) the survival or growth potential of L.monocytogenes on various cheeses during storage, ii) the effect of initial indigenous microbiota on pathogen growth in comparison to expected growth curves retrieved by existing predictive models, and iii) the impact of habituation on/in cheeses surfaces on the subsequent acid resistance during simulated gastric digestion. Portions of cream (Cottage and Mascarpone), soft (Anthotyros, Camembert, Mastelo®, Manouri, Mozzarella, Ricotta), and semi-hard (Edam, Halloumi, Gouda) cheeses were inoculated with ca. 100CFU/g or cm 2 of L.monocytogenes and stored under vacuum or aerobic conditions at 7°C (n=4). The impact of varying (initial) levels of starter culture or indigenous spoilage microbiota on pathogen growth was evaluated by purchasing cheese packages on different dates in relation to production and expiration date (subsequently reflecting to different batches) mimicking a potential situation of cheese contamination with L.monocytogenes during retail display. Values of pH and a w were also monitored and used to simulate growth of L. monocytogenes by existing models and compare it with the observed data of the study. Survival in simulated gastric fluid (SGF) (pH1.5; HCl; max. 120min) was assessed at three time points during storage. Mascarpone, Ricotta, Mozzarella, Camembert, and Halloumi supported L.monocytogenes growth by 0.5-0.8logCFU/g or cm 2 per day, since low initial levels of total viable counts (TVC) (1.8-3.8logCFU/g or cm 2 ) and high pH/a w values (ca. 6.23-6.64/0.965-0.993) were recorded. On Cottage, Anthotyros, Manouri, Mastelo®, Edam, and Gouda, the pathogen survived at populations similar or lower than the inoculation level due to the high reported competition

  20. Effect of humidity and temperature on the survival of Listeria monocytogenes on surfaces.

    Science.gov (United States)

    Redfern, J; Verran, J

    2017-04-01

    Listeria monocytogenes is a pathogenic bacterium, with human disease and infection linked to dairy products, seafood, ready-to-eat meat and raw & undercooked meats. Stainless steel is the most common food preparation surface and therefore, it is important to understand how food storage conditions such as surface materials, temperature and relative humidity can affect survival of L. monocytogenes. In this study, survival of L. monocytogenes on stainless steel was investigated at three temperatures (4, 10 and 21°C), each approx. 11, 50 and 85% humidity. Results indicate that the lower the temperature, the more cells were recovered in all three humidity environments, while medium humidity enhances survival, irrespective of temperature. Lower humidity decreases recovery at all temperatures. These data support the guidance noted above that humidity control is important, and that lower humidity environments are less likely to support retention of viable L. monocytogenes on a stainless steel surface. Understanding survival of potential food-borne pathogens is essential for the safe production and preparation of food. While it has long been 'common knowledge' that relative humidity can affect the growth and survival of micro-organisms, this study systematically describes the survival of L. monocytogenes on stainless steel under varying humidity and temperatures for the first time. The outcomes from this paper will allow those involved with food manufacture and preparation to make informed judgement on environmental conditions relating to humidity control, which is lacking in the food standards guidelines. © 2017 The Society for Applied Microbiology.

  1. The role of defeathering in the contamination of turkey skin by Salmonella species and Listeria monocytogenes.

    Science.gov (United States)

    Clouser, C S; Doores, S; Mast, M G; Knabel, S J

    1995-04-01

    This study was undertaken to determine whether the incidence of either Salmonella spp. or Listeria monocytogenes on turkeys at three commercial processors could be related to the type of defeathering system: 1) conventional, 58 C common bath scald; 2) kosher, 7 C common bath scald; or 3) steam-spray, 62 C nonimmersion scald. Flocks were sampled before defeathering, after defeathering, and after chill at each facility. The incidence of Salmonella-positive turkeys significantly increased subsequent to conventional defeathering (10 positive out of 14) as compared with before defeathering (3/14). The number of Salmonella-positive carcasses following kosher (0/14) and steam-spray (2/14) defeathering were similar to the number of Salmonella-positive carcasses found prior to defeathering (1/14 and 3/14, respectively). The incidence of Salmonella-positive carcasses following chill was slightly lower, but not significantly different than the number of Salmonella-positive carcasses found immediately following defeathering at all processors (8/14, 0/14, 1/14 for conventional, kosher, and steam-spray processors, respectively). Although L. monocytogenes was detected on turkeys sampled before chilling (2/10, kosher) and after chilling (8/14, kosher; 1/14, conventional), no L. monocytogenes was detected on turkeys at any of the processors prior to the evisceration process. Flocks with high aerobic plate counts prior to processing were more likely to contain Salmonella-positive birds throughout processing. Aerobic plate counts of all flocks were similar after chill whether or not Salmonella spp. and L. monocytogenes were detected.

  2. Survival of Listeria monocytogenes in low acid italian sausage produced under brazilian conditions Sobrevivência de Listeria monocytogenes em salame tipo italiano de baixa acidez, produzido sob condições brasileiras de fabricação

    Directory of Open Access Journals (Sweden)

    Roberto Degenhardt

    2007-06-01

    Full Text Available Dry sausages have been considered ready-to-eat products with low risk of causing listeriosis due to the hurdles created during the manufacturing process such as low pH and a w, high salt concentration and presence of lactic acid bacteria (LAB. However, several studies have detected survival of Listeria monocytogenes in these products and also shown that process parameters, LAB and L. monocytogenes strains directly influence the results. In this work, survival of the pathogen in sausages prepared with three different formulations (one standard formulation, one formulation added of Lactobacillus plantarum and one added of 2% sodium lactate, using the manufacturing process usually employed in Brazil, was evaluated. Naturally contaminated sausages presented a small increase in the counts of L. monocytogenes in the first days of the process, followed by a gradual decrease until the end of the process. In experimentally contaminated samples containing L. plantarum, the reduction of counts of L. monocytogenes during processing was considerable, but there wasn´t significant differences between the treatments.Salames têm sido considerados produtos prontos para o consumo com baixo risco de provocar listeriose devido aos obstáculos criados no processo de fabricação e suas características de pH e atividade água baixos, alta concentração de sal e presença de bactérias lácticas. Entretanto, a sobrevivência de Listeria monocytogenes nesta classe de produtos é verificada e estudos de processo visando à redução da contaminação por este patógeno, têm demonstrado que particularidades como variação dos parâmetros de processo, cepas de bactérias lácticas e de L. monocytogenes influenciam diretamente os resultados. Neste estudo três formulações foram avaliadas (uma padrão, uma com inoculação da cultura Lactobacillus plantarum e outra com adição 2% de lactato de sódio empregando parâmetros de processo comumente praticados no Brasil

  3. Entry of Vibrio harveyi and Vibrio fischeri into the viable but nonculturable state

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaiah, Neelam; Ravel, J.; Straube, W.L.; Hill, R.T.; Colwell, R.R.

    , direct viable counts, actively respiring cell counts, nucleoid-containing cell counts, and total counts were determined. V. harveyi incubated at 22 degrees C nutrient-limited artificial seawater (ASW) became nonculturable after approximately 62 and 45 d...

  4. ASSESSMENT OF ACTION OF DISINFECTANTS AGAINST LISTERIA MONOCYTOGENES BIOFILMS

    Directory of Open Access Journals (Sweden)

    T. K. CABEÇA

    2008-12-01

    Full Text Available

    The purpose of this study was to assess the action of various disinfectants used in food industry against biofilm cells of Listeria monocytogenes formed on stainless steel surfaces during 24, 72 and 120 hours. Numbers of viable biofilm cells decreased after treatment with all the tested disinfectants (iodine, biguanide, quaternary ammonium compounds, peracetic acid and sodium hypochlorite. Sodium hypochlorite was the most effective disinfectant against the biofilm cells, while biguanide and iodine were the least. Scanning electron microscopy observations demonstrated attached cells on stainless steel surfaces after treatment with all the disinfectants. These observations showed that microorganisms were not completely removed from stainless steel surfaces after treatment with the disinfectants, however, the attachment did not means the viability of remaining cells. The biofilm age in hours (24, 72 and 120 had no apparent influence on resistance of microbiological cells to the disinfectants under study. In conclusion biofilm cells of L. monocytogenes can withstand disinfectants action.

  5. Quantifying the combined effects of pronase and benzalkonium chloride in removing late-stage Listeria monocytogenes-Escherichia coli dual-species biofilms.

    Science.gov (United States)

    Rodríguez-López, Pedro; Puga, Carmen H; Orgaz, Belén; Cabo, Marta L

    2017-09-01

    This work presents the assessment of the effectivity of a pronase (PRN)-benzalkonium chloride (BAC) sequential treatment in removing Listeria monocytogenes-Escherichia coli dual-species biofilms grown on stainless steel (SS) using fluorescence microscopy and plate count assays. The effects of PRN-BAC on the occupied area (OA) by undamaged cells in 168 h dual-species samples were determined using a first-order factorial design. Empirical equations significantly (r 2 = 0.927) described a negative individual effect of BAC and a negative interactive effect of PRN-BAC achieving OA reductions up to 46%. After treatment, high numbers of remaining attached and released viable and cultivable E. coli cells were detected in PRN-BAC combinations when low BAC concentrations were used. Therefore, at appropriate BAC doses, in addition to biofilm removal, sequential application of PRN and BAC represents an appealing strategy for pathogen control on SS surfaces while hindering the dispersion of live cells into the environment.

  6. Evaluation of PCR and DNA hybridization protocols for detection of viable enterotoxigenic Clostridium perfringens in irradiated beef

    International Nuclear Information System (INIS)

    Baez, L.A.; Juneja, V.K.; Thayer, D.W.; Sackitey, S.

    1997-01-01

    The sensitivity of DNA hybridization and polymerase chain reaction (PCR), was evaluated in irradiated cooked and raw beef samples. A membrane-based colony hybridization assay and a PCR protocol, both with specificity for the enterotoxin A gene of Clostridium perfringens, were compared with viable plate counts. The results of the colony hybridization procedure were in agreement with viable plate counts for detection and enumeration of enterotoxigenic C. perfringens. The PCR procedure combined a 4 h enrichment followed by a nucleic acid extraction step and assessed the amplification of 183 and 750 base pair enterotoxin gene targets. Detection of C. perfringens by PCR did not show a reliable correlation with viable plate counts or the colony hybridization assay. C. perfringens killed by irradiation were not detected by the plate count or colony hybridization methods; however, killed cells were detected with the PCR technique. By relying on the growth of viable cells for detection and/or enumeration, the colony hybridization and plate count methods provided a direct correlation with the presence of viable bacteria

  7. Nondestructive detection of total viable count changes of chilled pork in high oxygen storage condition based on hyperspectral technology

    Science.gov (United States)

    Zheng, Xiaochun; Peng, Yankun; Li, Yongyu; Chao, Kuanglin; Qin, Jianwei

    2017-05-01

    The plate count method is commonly used to detect the total viable count (TVC) of bacteria in pork, which is timeconsuming and destructive. It has also been used to study the changes of the TVC in pork under different storage conditions. In recent years, many scholars have explored the non-destructive methods on detecting TVC by using visible near infrared (VIS/NIR) technology and hyperspectral technology. The TVC in chilled pork was monitored under high oxygen condition in this study by using hyperspectral technology in order to evaluate the changes of total bacterial count during storage, and then evaluate advantages and disadvantages of the storage condition. The VIS/NIR hyperspectral images of samples stored in high oxygen condition was acquired by a hyperspectral system in range of 400 1100nm. The actual reference value of total bacteria was measured by standard plate count method, and the results were obtained in 48 hours. The reflection spectra of the samples are extracted and used for the establishment of prediction model for TVC. The spectral preprocessing methods of standard normal variate transformation (SNV), multiple scatter correction (MSC) and derivation was conducted to the original reflectance spectra of samples. Partial least squares regression (PLSR) of TVC was performed and optimized to be the prediction model. The results show that the near infrared hyperspectral technology based on 400-1100nm combined with PLSR model can describe the growth pattern of the total bacteria count of the chilled pork under the condition of high oxygen very vividly and rapidly. The results obtained in this study demonstrate that the nondestructive method of TVC based on NIR hyperspectral has great potential in monitoring of edible safety in processing and storage of meat.

  8. Fødevarebetinget listeria monocytogenes endokarditis

    DEFF Research Database (Denmark)

    Frydland, Martin; Bundgaard, Henning; Moser, Claus

    2014-01-01

    Infection with Listeria monocytogenes is rare and mainly seen in immunosuppressed patients. Infection with L. monocytogenes has a mortality rate of 30%. We present a case report of L. monocytogenes bacteraemia and endocarditis in a 70-year-old man with several co-morbidities and following four...... major surgical procedures. This illustrates the findings and characteristics in one of the 16 patients who died in 2013 and 2014 this summer due to sausage-related L. monocytogenes infection....

  9. Solar irradiance limits the long-term survival of Listeria monocytogenes in seawater.

    Science.gov (United States)

    NicAogáin, K; Magill, D; O'Donoghue, B; Conneely, A; Bennett, C; O'Byrne, C P

    2018-03-01

    Seafood has often been implicated in outbreaks of food-borne illness caused by Listeria monocytogenes but the source of contamination is usually not known. In this study we investigated the possibility that this pathogen could survive in seawater for an extended time period. Freshly collected seawater samples were inoculated with 1 × 10 8  CFU per ml of L. monocytogenes EGD-e and survival was monitored by plate counting for up to 25 days. When incubated in the dark, either at ambient temperatures (4-14°C) or at 16°C, >10 4  CFU per ml survivors were present after 25 days. However, when the seawater cell suspensions were exposed to ambient light (solar irradiation) and temperatures, L. monocytogenes lost viability rapidly and no survivors could be detected after the 80 h time point. Both UV-A and visible light in the blue region of the spectrum (470 nm) were found to contribute to this effect. The stress inducible sigma factor σ B was found to play a role in survival of L. monocytogenes in seawater. Together these data demonstrate that solar irradiation is a critical determinant of L. monocytogenes survival in marine environments. The data further suggest the possibility of controlling this food-borne pathogen in food-processing environments using visible light. Listeria monocytogenes is a food-borne bacterial pathogen capable of causing the life-threatening infection, listeriosis. In seafood the route of contamination from the environment is often not well understood as this pathogen is not generally thought to survive well in seawater. Here we provide evidence that L. monocytogenes is capable of surviving for long periods of time in seawater when light is excluded. Sunlight is demonstrated to have a significant effect on the survival of this pathogen in seawater, and both visible (470 nm) and UV-A light are shown to contribute to this effect. © 2017 The Society for Applied Microbiology.

  10. Entry of Vibrio harveyi and Vibrio fischeri into the viable but nonculturable state.

    Science.gov (United States)

    Ramaiah, N; Ravel, J; Straube, W L; Hill, R T; Colwell, R R

    2002-01-01

    Physiological responses of marine luminous bacteria, Vibrio harveyi (ATCC 14216) and V. fischeri (UM1373) to nutrient-limited normal strength (35 ppt iso-osmolarity) and low (10 ppt hypo-osmolarity) salinity conditions were determined. Plate counts, direct viable counts, actively respiring cell counts, nucleoid-containing cell counts, and total counts were determined. Vibrio harveyi incubated at 22 degrees C in nutrient-limited artificial seawater (ASW) became nonculturable after approximately 62 and 45 d in microcosms of 35 ppt and 10 ppt ASW, respectively. In contrast, V. fischeri became nonculturable at approximately 55 and 31 d in similar microcosms. Recovery of both culturability and luminescence of cells in the viable but nonculturable state was achieved by addition of nutrient broth or nutrient broth supplemented with a carbon source, including luminescence-stimulating compounds. Temperature upshift from 22 degrees C to 30 degrees C or 37 degrees C did not result in recovery from nonculturability. The study confirms entry of V. harveyi and V. fischeri into the viable but nonculturable state under low-nutrient conditions and demonstrates nutrient-dependent resuscitation from this state. This study confirms loss of luminescence of V. harveyi and V. fischeri on entry into the viable but nonculturable state and suggests that enumeration of luminescent cells in water samples may be a rapid method to deduce the nutrient status of a water sample.

  11. Effect of X-ray treatments on Escherichia coli 0157:H7, Listeria monocytogenes, Shigella flexneri, Salmonella enterica and inherent microbiota on whole mangoes

    Science.gov (United States)

    The aims of this investigation were to; (i) study the effect of X-ray treatments in reducing Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri on whole mangoes, and (ii) study the effect of Xray treatments on microflora counts (mesophilic counts, psychrotrop...

  12. The high prevalence of Listeria monocytogenes peritonitis in cirrhotic patients of an Egyptian Medical Center.

    Science.gov (United States)

    El Sayed Zaki, Maysaa; El Shabrawy, Walaa Othman; El-Eshmawy, Mervat M; Aly Eletreby, Shahera

    2011-09-01

    Spontaneous bacterial peritonitis (SBP) is a potentially lethal complication of cirrhosis. It is probably the most characteristic infectious complication of cirrhosis. The aim of this study was to evaluate the bacterial and fungal causes of SBP in Egyptian population. Furthermore to predict the occurrence of rare pathogen like Listeria monocytogenes in those patients. The study included 100 patients with end stage liver disease associated with ascites. Patients were suspected to have SBP. The ascitic fluids were subjected to full cytological and microbiological study. The peritoneal fluid cytological study revealed that 50 samples had cell counts >250 cells/mm(3). 37 samples had growth and 13 samples had no growth (CNNA). The distribution of isolated pathogens was Gram positive cocci 48.8% followed by L. monocytogenes 24.4%, Gram negative bacilli 12.2% and Mycobacterium tuberculosis 7.3. The cells counts associated with listeria culture were 475 cells/mm(3) with sensitivity 70% and specificity 68%. The study highlights the prevalence of microorganisms in Egyptian patients with liver cirrhosis associated with ascites. It reflects the occurrence of L. monocytogenes as an important pathogen of such clinical situation. Other rare pathogens like M. tuberculosis are not uncommon in those patients. Copyright © 2011 King Saud Bin Abdulaziz University for Health Sciences. Published by Elsevier Ltd. All rights reserved.

  13. Antimicrobial activity of reuterin produced by Lactobacillus reuteri on Listeria monocytogenes in cold-smoked salmon.

    Science.gov (United States)

    Montiel, R; Martín-Cabrejas, I; Langa, S; El Aouad, N; Arqués, J L; Reyes, F; Medina, M

    2014-12-01

    Lactobacillus reuteri INIA P579 was used for the production and purification of reuterin. The purity of reuterin was assessed by high resolution electrospray ionization mass spectrometry (HRESIMS) and nuclear magnetic resonance (NMR) spectroscopy. After purification, reuterin concentration obtained was 1.3 M. The inhibitory activity using Escherichia coli K12 as indicator strain was estimated to be 510 AU/ml. Survival curves in tryptic soy broth revealed that reuterin required to inhibit the growth of three Listeria monocytogenes strains was in the range of 2-4 AU/ml. Purified reuterin (10 AU/g) significantly reduced the growth of L. monocytogenes in cold-smoked salmon kept under moderate or strong temperature abuse conditions. After 15 d at 8 °C, cold-smoked salmon with added reuterin exhibited L. monocytogenes counts 2.0 log CFU/g lower than control smoked salmon with no reuterin added. At 30 °C, reuterin also controlled the growth of the pathogen, with counts 1.4 and 0.9 log CFU/g lower than those observed in control smoked salmon after 24 and 48 h, respectively. The addition of purified reuterin might be used as a hurdle technology to improve the safety and extend the shelf-life of lightly preserved seafood products such as cold-smoked salmon. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Ultrasonic cleaning of conveyor belt materials using Listeria monocytogenes as a model organism.

    Science.gov (United States)

    Tolvanén, Riina; Lunden, Janne; Korkeala, Hannu; Wirtanen, Gun

    2007-03-01

    Persistent Listeria monocytogenes contamination of food industry equipment is a difficult problem to solve. Ultrasonic cleaning offers new possibilities for cleaning conveyors and other equipment that are not easy to clean. Ultrasonic cleaning was tested on three conveyor belt materials: polypropylene, acetal, and stainless steel (cold-rolled, AISI 304). Cleaning efficiency was tested at two temperatures (30 and 45 degrees C) and two cleaning times (30 and 60 s) with two cleaning detergents (KOH, and NaOH combined with KOH). Conveyor belt materials were soiled with milk-based soil and L. monocytogenes strains V1, V3, and B9, and then incubated for 72 h to attach bacteria to surfaces. Ultrasonic cleaning treatments reduced L. monocytogenes counts on stainless steel 4.61 to 5.90 log units; on acetal, 3.37 to 5.55 log units; and on polypropylene, 2.31 to 4.40 log units. The logarithmic reduction differences were statistically analyzed by analysis of variance using Statistical Package for the Social Sciences software. The logarithmic reduction was significantly greater in stainless steel than in plastic materials (P conveyor belt materials.

  15. Effect of x-ray treatments on Escherichia coli O157:H7, Listeria monocytogenes, Shigella flexneri, Salmonella enterica and inherent microbiota on whole mangoes

    Science.gov (United States)

    The aims of this investigation were to; (i) study the effect of X-ray treatments in reducing Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri on whole mangoes, and (ii) study the effect of Xray treatments on microflora counts (mesophilic counts, psychrotrop...

  16. Detection and Verification of the Viable but Nonculturable (VBNC) State of Escherichia coli O157:H7 and Listeria monocytogenes Using Flow Cytometry and Standard Plating.

    Science.gov (United States)

    Afari, George Kwabena; Hung, Yen-Con

    2018-06-15

    The use of electrolyzed oxidizing (EO) water to inactivate microorganisms on foods has been extensively studied and shown to be effective. However, the prospect of the formation of "viable but nonculturable" (VBNC) cells in pathogens after low free chlorine concentration (FCC) treatments under high organic loads presents safety concerns. This study investigated the effect of EO water FCC on inducing Escherichia coli O157:H7 and Listeria monocytogenes into the VBNC state and studied possible resuscitation triggering procedures of the VBNC cells. A 5-strain cocktail of each pathogen (10 6 colony forming units [CFU]/mL) was exposed to EO water (FCC of 20, 10, 5, 2.5, 1.25, 0.625 mg/L) and allowed to stand for 1 and 5 min, followed by the addition of neutralizing broth. Treated samples were plated on nonselective agar and analyzed using flow cytometry. For resuscitation, samples treated with identified VBNC induction conditions were exposed to elevated temperatures (37 °C) as well as addition of sodium pyruvate (SP) and Tween® 20 (T20) solutions. The initial culturing procedures suggested complete inactivation of both pathogens at 2.5 and 1.25 mg/L FCC in the growth medium. However, flow cytometry profiles showed VBNC cells were present. Subjecting samples to the recovery procedures further proved that VBNC E. coli O157:H7 can be resuscitated after exposure to SP and T20 at 37 °C, while L. monocytogenes did not resuscitate. These findings show that treating pathogens at low FCC can induce the VBNC state, and culturability of E. coli O157:H7 can be restored under appropriate conditions. VBNC induction conditions for foodborne pathogens during chlorine washing treatment were determined in a broth system and the information can serve as a basis for future studies that address the prevention of VBNC formation during produce wash treatments. © 2018 Institute of Food Technologists®.

  17. Inhibition effect of tea tree oil on Listeria monocytogenes growth and exotoxin proteins listeriolysin O and p60 secretion.

    Science.gov (United States)

    Liu, Z; Meng, R; Zhao, X; Shi, C; Zhang, X; Zhang, Y; Guo, N

    2016-12-01

    Listeria monocytogenes (L. monocytogenes) is a Gram-positive bacterium that causes infections in humans. In this study, the effects of tea tree oil (TTO) at subinhibitory concentrations on L. monocytogenes growth and two important exotoxin proteins secreted by L. monocytogenes were researched. Treatment with half of minimal inhibitory concentration of TTO demonstrated very little or no reduction in numbers of viable ATCC 19115 cells. Listeriolysin O (LLO) and p60, were investigated. A listeriolysin assay was used to investigate the hemolytic activities of L. monocytogenes exposed to TTO, and the secretion of LLO and p60 was detected by immunoblot analysis. Additionally, real-time RT-PCR was used to analyse the influence of TTO on the transcription of LLO and p60 encoded genes hly and iap respectively. According to our experimental results, we propose that TTO could be used as a promising natural compound against L. monocytogenes and its virulence factors. This is the first report on the influence of subinhibitory concentrations of tea tree oil (TTO) on the secretion of listeriolysin O (LLO) and p60, the critical virulence factors involved in Listeria pathogenesis. The results showed that TTO at 0·25 mg ml -1 reduced the secretion of LLO and p60 to 10 and 34·9% respectively, in addtion, the transcription of hly and iap was reduced to 10 and 4·3% at 0·5 mg ml -1 respectively. We propose that TTO could be used as a promising antimicrobial compound and virulence inhibitor against L. monocytogenes. © 2016 The Society for Applied Microbiology.

  18. Application of zein antimicrobial edible film incorporating Zataria ...

    African Journals Online (AJOL)

    Aghomotsegin

    2015-06-12

    Jun 12, 2015 ... Addition of Z. multiflora boiss essential oil, resulted in decreasing the count of viable Salmonella enteritidis, Listeria monocytogenes, Escherichia coli and Staphylococcus aureus in the produced cheese. This investigation concludes that the biofilm containing Z. multiflora boiss essential oil can be highly.

  19. Prevalence, populations and pheno- and genotypic characteristics of Listeria monocytogenes isolated from ready-to-eat vegetables marketed in São Paulo, Brazil.

    Science.gov (United States)

    Sant'Ana, Anderson S; Igarashi, Maria Crystina; Landgraf, Mariza; Destro, Maria Teresa; Franco, Bernadette D G M

    2012-04-02

    Listeria monocytogenes is a foodborne pathogen of great concern due to the high fatality rates of listeriosis. The consumption of RTE vegetables has increased in Brazil over the last two decades, but little is known about the risks associated to the consumption of these products. This study evaluated the prevalence and counts of L. monocytogenes in 512 packages of ready-to-eat vegetables marketed in São Paulo. The isolates were characterized for their serotypes, ribotypes, positivity for virulence genes inlA, inlC and inlJ, resistance to chlorine, growth rate variability and capability to form biofilm on stainless steel (AISI 304, #4) coupons. L. monocytogenes was detected in 3.1% of the samples. Only five samples presented countable levels, with counts between 1.0×10(1) and 2.6×10(2)CFU/g. Isolates belonged to serotypes 1/2b or 4b and most were positive for genes inlC and inlJ. Ribotypable isolates were grouped into four groups: 1038 (69.4%), 19175 (11.3%), 19191 (17.7%) and 18604 (one isolate). Most isolates survived to exposure to 125 ppm of a chlorine-based disinfectant for 3 min. All isolates were capable to attach to the coupons, reaching counts above 4 log(10) CFU/cm(2) and the growth rate (μ) at 25°C of the majority of the isolates varied between 0.1 and 0.2 log OD/h, but for few strains the μ was as high as 0.26 log OD/h. Results of this survey indicate that RTE vegetables may be vehicles of L. monocytogenes strains with limited variation in serotype, ribotype and virulence factors but varying significantly in resistance to chlorine disinfectants, capability of forming biofilm and growth rate. Data obtained is of foremost importance to serve as baseline for the development of scientific-based policies to control the incidence of L. monocytogenes in RTE vegetables in Brazil. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Rapid assessment of viable but non-culturable Bacillus coagulans MTCC 5856 in commercial formulations using Flow cytometry

    Science.gov (United States)

    Majeed, Muhammed; Majeed, Shaheen; Nagabhushanam, Kalyanam; Punnapuzha, Ardra; Philip, Sheena

    2018-01-01

    Accurate enumeration of bacterial count in probiotic formulation is imperative to ensure that the product adheres to regulatory standards and citation in consumer product label. Standard methods like plate count, can enumerate only replicating bacterial population under selected culture conditions. Viable but non culturable bacteria (VBNC) retain characteristics of living cells and can regain cultivability by a process known as resuscitation. This is a protective mechanism adapted by bacteria to evade stressful environmental conditions. B. coagulans MTCC 5856(LactoSpore®) is a probiotic endospore which can survive for decades in hostile environments without dividing. In the present study, we explored the use of flow cytometry to enumerate the viable count of B. coagulans MTCC 5856 under acidic and alkaline conditions, high temperature and in commercial formulations like compressed tablets and capsules. Flow cytometry (FCM) was comparable to plate count method when the spores were counted at physiological conditions. We show that VBNC state is induced in B. coagulans MTCC 5856by high temperature and acidic pH. The cells get resuscitated under physiological conditions and FCM was sensitive to detect the VBNC spores. Flow cytometry showed excellent ability to assess the viable spore count in commercial probiotic formulations of B. coagulans MTCC 5856. The results establish Flow cytometry as a reliable method to count viable bacteria in commercial probiotic preparations. Sporulation as well as existence as VBNC could contribute to the extreme stability of B. coagulans MTCC 5856. PMID:29474436

  1. Rapid assessment of viable but non-culturable Bacillus coagulans MTCC 5856 in commercial formulations using Flow cytometry.

    Directory of Open Access Journals (Sweden)

    Muhammed Majeed

    Full Text Available Accurate enumeration of bacterial count in probiotic formulation is imperative to ensure that the product adheres to regulatory standards and citation in consumer product label. Standard methods like plate count, can enumerate only replicating bacterial population under selected culture conditions. Viable but non culturable bacteria (VBNC retain characteristics of living cells and can regain cultivability by a process known as resuscitation. This is a protective mechanism adapted by bacteria to evade stressful environmental conditions. B. coagulans MTCC 5856(LactoSpore® is a probiotic endospore which can survive for decades in hostile environments without dividing. In the present study, we explored the use of flow cytometry to enumerate the viable count of B. coagulans MTCC 5856 under acidic and alkaline conditions, high temperature and in commercial formulations like compressed tablets and capsules. Flow cytometry (FCM was comparable to plate count method when the spores were counted at physiological conditions. We show that VBNC state is induced in B. coagulans MTCC 5856by high temperature and acidic pH. The cells get resuscitated under physiological conditions and FCM was sensitive to detect the VBNC spores. Flow cytometry showed excellent ability to assess the viable spore count in commercial probiotic formulations of B. coagulans MTCC 5856. The results establish Flow cytometry as a reliable method to count viable bacteria in commercial probiotic preparations. Sporulation as well as existence as VBNC could contribute to the extreme stability of B. coagulans MTCC 5856.

  2. Rapid assessment of viable but non-culturable Bacillus coagulans MTCC 5856 in commercial formulations using Flow cytometry.

    Science.gov (United States)

    Majeed, Muhammed; Majeed, Shaheen; Nagabhushanam, Kalyanam; Punnapuzha, Ardra; Philip, Sheena; Mundkur, Lakshmi

    2018-01-01

    Accurate enumeration of bacterial count in probiotic formulation is imperative to ensure that the product adheres to regulatory standards and citation in consumer product label. Standard methods like plate count, can enumerate only replicating bacterial population under selected culture conditions. Viable but non culturable bacteria (VBNC) retain characteristics of living cells and can regain cultivability by a process known as resuscitation. This is a protective mechanism adapted by bacteria to evade stressful environmental conditions. B. coagulans MTCC 5856(LactoSpore®) is a probiotic endospore which can survive for decades in hostile environments without dividing. In the present study, we explored the use of flow cytometry to enumerate the viable count of B. coagulans MTCC 5856 under acidic and alkaline conditions, high temperature and in commercial formulations like compressed tablets and capsules. Flow cytometry (FCM) was comparable to plate count method when the spores were counted at physiological conditions. We show that VBNC state is induced in B. coagulans MTCC 5856by high temperature and acidic pH. The cells get resuscitated under physiological conditions and FCM was sensitive to detect the VBNC spores. Flow cytometry showed excellent ability to assess the viable spore count in commercial probiotic formulations of B. coagulans MTCC 5856. The results establish Flow cytometry as a reliable method to count viable bacteria in commercial probiotic preparations. Sporulation as well as existence as VBNC could contribute to the extreme stability of B. coagulans MTCC 5856.

  3. Modeling the behavior of Listeria monocytogenes during enrichment in half Fraser broth; impact of pooling and the duration of enrichment on the detection of L. monocytogenes in food.

    Science.gov (United States)

    Augustin, Jean-Christophe; Kalmokoff, Martin; Ells, Timothy; Favret, Sandra; Desreumaux, Jennifer; Decourseulles Brasseur, Emilie; Gnanou Besse, Nathalie

    2016-12-01

    A stochastic model describing the growth of Listeria monocytogenes during enrichment in half Fraser was developed for the purpose of estimating the effects of modifications to the first enrichment step of the EN ISO 11290-1 detection method. Information pertaining to the variability of growth rates, physiological state of the cell, and the behavior of individual cells contaminating the food were obtained from previously published studies. We used this model to investigate the impact of pooling enrichment broths (wet pooling) on the performance of the standard method. For validation of the model, the numbers of L. monocytogenes occurring in 88 naturally contaminated foods following pre-enrichment were compared to model-simulated microbial counts. The model was then used to perform simulations representative of the natural contamination observed for smoked salmon in the European baseline survey of 2010-2011. The model-estimated L. monocytogenes levels following individual enrichment or following the pooling of five broths where only one would be contaminated were compared. The model indicated a 10% loss of method sensitivity resulting from wet pooling. The model also predicted a 5% decrease in the sensitivity of the method when the duration of the enrichment was reduced from 24 to 22 h. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Essential oils of thyme and Rosemary in the control of Listeria monocytogenes in raw beef

    Directory of Open Access Journals (Sweden)

    Maíra Maciel Mattos de Oliveira

    2013-12-01

    Full Text Available This study was developed in order to evaluate two alternatives for the control of Listeria monocytogenes in raw bovine meat pieces, both based on the use of Thymus vulgaris and Rosmarinus officinalis essential oils (EOs. The antilisterial activity of different concentrations of the EOs was tested in vitro using agar dilution and disk volatilization techniques. In addition, L. monocytogenes was inoculated in meat pieces, which were submerged in edible gelatin coatings containing 2% (v/v EOs or submitted to the vapor of EOs (0.74 μL.cm-3. L. monocytogenes was quantified after one, 48 and 96 hours of storage (7 °C. In the in vitro tests, the EO of T. vulgaris presented higher activity. The two options used (edible gelatin coating and vapor activity, in spite of exercising effects with differentiated behaviors, presented antibacterial activity against L. monocytogenes inoculated in raw bovine meat (p < 0.05. Greatest antibacterial activity were obtained in the experiment that used edible coatings containing EOs, at 48 hours of storage reductions in bacterial counts between 1.09 and 1.25 Log CFU.g-1 were obtained. In the vapor effect experiment, the EO of T. vulgaris caused the highest reduction in the population of bacteria inoculated in raw bovine meat (p < 0.05, 0.40 Log CFU.g-1 at 96 hours of storage. This study supplied important information regarding new and promising natural alternatives, based on the concept of active packaging, for the control of L. monocytogenes in the meat industry.

  5. Anti-listerial activity of a polymeric film coated with hybrid coatings doped with Enterocin 416K1 for use as bioactive food packaging.

    Science.gov (United States)

    Iseppi, Ramona; Pilati, Francesco; Marini, Michele; Toselli, Maurizio; de Niederhäusern, Simona; Guerrieri, Elisa; Messi, Patrizia; Sabia, Carla; Manicardi, Giuliano; Anacarso, Immacolata; Bondi, Moreno

    2008-04-30

    In this study, Enterocin 416K1, a bacteriocin produced by Enterococcus casseliflavus IM 416K1, was entrapped in an organic-inorganic hybrid coating applied to a LDPE (low-density polyethylene) film for its potential use in the active food packaging field. The antibacterial activity of the coated film was evaluated against Listeria monocytogenes NCTC 10888 by qualitative modified agar diffusion assay, quantitative determination in listeria saline solution suspension and direct contact with artificially contaminated food samples (frankfurters and fresh cheeses) stored at room and refrigeration temperatures. All investigations demonstrated that enterocin-activated coatings have a good anti-listeria activity. Qualitative tests showed a clear zone of inhibition in the indicator lawn in contact with and around the coated film. During the quantitative antibacterial evaluation the L. monocytogenes viable counts decreased to 1.5 log units compared to the control. The inhibitory capability was confirmed also in food-contact assays. In all food samples packed with coated films we observed a significant decrease in L. monocytogenes viable counts in the first 24 h compared to the control. This difference was generally maintained up to the seventh day and then decreased, with the exception of the cheese samples stored at refrigeration temperature.

  6. Growth and survival of Escherichia coli O157:H7 and Listeria monocytogenes in egg products held at different temperatures.

    Science.gov (United States)

    Yang, S E; Chou, C C

    2000-07-01

    Growth and survival of Escherichia coli O157:H7 and Listeria monocytogenes in steamed eggs and scrambled eggs held at different temperatures (5, 18, 22, 37, 55, and 60 degrees C) were investigated in the present study. Among the holding temperatures tested, both pathogens multiplied best at 37 degrees C followed by 22, 18, and 5 degrees C. In general, E. coli O157:H7 grew better in the egg products than L. monocytogenes did at all the storage temperatures tested except at 5 degrees C. E. coli O157:H7 did not grow in steamed eggs and scrambled eggs held at 5 degrees C. L. monocytogenes showed a slight population increase of approximately 0.6 to 0.9 log CFU/g in these egg products at the end of the 36-h storage period at 5 degrees C. The population of both pathogens detected in the egg products was affected by the initial population, holding temperature, and length of the holding period. It was also noted that L. monocytogenes was more susceptible than E. coli O157:H7 in steamed eggs held at 60 degrees C. After holding at 60 degrees C for 1 h, no detectable viable cells of L. monocytogenes with a population reduction of 5.4 log CFU/g was observed in steamed eggs, whereas a lower population reduction of only approximately 0.5 log CFU/ml was noted for E. coli O157:H7.

  7. Combination of endolysins and high pressure to inactivate Listeria monocytogenes.

    Science.gov (United States)

    van Nassau, Tomas J; Lenz, Christian A; Scherzinger, Anna S; Vogel, Rudi F

    2017-12-01

    Outbreaks of listeriosis are often related to the consumption of low-processed ready-to-eat food products (e.g. soft cheeses or smoked fish) contaminated with Listeria monocytogenes. Traditional preservation techniques, such as heat treatment, cannot eliminate Listeria from these products without strongly affecting the quality of the foods. We therefore investigated the use of endolysin (PlyP40, Ply511, or PlyP825) in combination with high hydrostatic pressure processing to kill L. monocytogenes in buffer. The results demonstrated a more than additive effect when both treatments were combined. For example, whereas 0.16 μg/mL PlyP825 or 300 MPa (1 min, 30 °C) applied individually reduced the cell count by 0.2 and 0.3 log cfu, respectively, a combined treatment resulted in a reduction of 5.5 log cfu. Similar results were obtained for the other endolysins combined with high pressure processing. We also showed that the synergistic inactivation of cells by endolysin and HHP is possible at a pressure level of only 200 MPa (2 min, 30 °C). Thus, the application of endolysins did not only substantially increase the bactericidal effect of high pressure, but it also enabled the inactivation of bacterial cells at much lower pressure levels. This shows the potential of using such combined processes for the inactivation of L. monocytogenes and food preservation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Listeria monocytogenes-carrying consortia in food industry. Composition, subtyping and numerical characterisation of mono-species biofilm dynamics on stainless steel.

    Science.gov (United States)

    Rodríguez-López, Pedro; Saá-Ibusquiza, Paula; Mosquera-Fernández, Maruxa; López-Cabo, Marta

    2015-08-03

    In order to find out how real Listeria monocytogenes-carrying biofilms are in industrial settings, a total of 270 environmental samples belonging to work surfaces from fish (n = 123), meat (n = 75) and dairy industries (n = 72) were analysed in order to detect L. monocytogenes. 12 samples were positive for L. monocytogenes and a total of 18 different species were identified as accompanying microbiota in fish and meat industry. No L. monocytogenes was found in samples from dairy industry. Molecular characterisation combining results of AscI and ApaI macrorestriction PFGE assays yielded 7 different subtypes of L. monocytogenes sharing in 71.43% of cases the same serogroup (1/2a-3a). Results from dynamic numerical characterisation between L. monocytogenes monospecies biofilms on stainless steel (SS) using MATLAB-based tool BIOFILMDIVER demonstrated that except in isolate A1, in which a significant increase in the percentage of covered area (CA), average diffusion distance (ADD) and maximum diffusion distance (MDD) was observed after 120 h of culture, no significant differences were observed in the dynamics of the rest of the L. monocytogenes isolates. Quantitative dual-species biofilm association experiments performed on SS indicated that L. monocytogenes cell counts presented lower values in mixed-species cultures with certain species at 24 and 48 h compared with mono-species culture. However, they remained unaltered after 72 h except when co-cultured with Serratia fonticola which presented differences in all sampling times and was also the dominant species within the dual-species biofilm. When considering frequency of appearance of accompanying species, an ecological distribution was demonstrated as Escherichia coli appeared to be the most abundant in fish industry and Carnobacterium spp. in meat industry. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Internalisation potential of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica subsp. enterica serovar Typhimurium and Staphylococcus aureus in lettuce seedlings and mature plants.

    Science.gov (United States)

    Standing, Taryn-Ann; du Plessis, Erika; Duvenage, Stacey; Korsten, Lise

    2013-06-01

    The internalisation potential of Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7 and Salmonella enterica subsp. enterica serovar Typhimurium in lettuce was evaluated using seedlings grown in vermiculite in seedling trays as well as hydroponically grown lettuce. Sterile distilled water was spiked with one of the four human pathogenic bacteria (10(5) CFU/mL) and used to irrigate the plants. The potential for pathogen internalisation was investigated over time using light microscopy, transmission electron microscopy and viable plate counts. Additionally, the identities of the pathogens isolated from internal lettuce plant tissues were confirmed using polymerase chain reaction with pathogen-specific oligonucleotides. Internalisation of each of the human pathogens was evident in both lettuce seedlings and hydroponically grown mature lettuce plants. To our knowledge, this is the first report of S. aureus internalisation in lettuce plants. In addition, the levels of background microflora in the lettuce plants were determined by plate counting and the isolates identified using matrix-assisted laser ionisation-time of flight (MALDI-TOF). Background microflora assessments confirmed the absence of the four pathogens evaluated in this study. A low titre of previously described endophytes and soil inhabitants, i.e., Enterobacter cloacae, Enterococcus faecalis, Lysinibacillus fusiformis, Rhodococcus rhodochrous, Staphylococcus epidermidis and Staphylococcus hominis were identified.

  10. First Trimester Listeria monocytogenes Septicemia

    NARCIS (Netherlands)

    Goddijn, M.; Schipper, H. G.; Spanjaard, L.; Wolf, H.

    1997-01-01

    Background: Little is known about fetal outcome after Listeria monocytogenes septicemia in the first trimester of pregnancy.Case: A primigravida with L. monocytogenes septicemia at 9 weeks gestation was treated with amoxicillin. At 40 weeks gestation a healthy female infant was born.Conclusion: This

  11. Survival and High-Hydrostatic Pressure Inactivation of Foodborne Pathogens in Salmorejo, a Traditional Ready-to-Eat Food.

    Science.gov (United States)

    Toledo Del Árbol, Julia; Pérez Pulido, Rubén; Grande, Ma José; Gálvez, Antonio; Lucas, Rosario

    2015-11-01

    Salmorejo is a traditional tomato-based creamy product. Because salmorejo is not heat-processed, there is a risk of contamination with foodborne pathogens from raw materials. Even though bacterial growth in salmorejo is strongly inhibited because of its acidic pH (close to 3.9), the growth and survival of 3 foodborne pathogens in this food has not been studied before. In this study, 3 cocktails consisting of Escherichia coli O157, Salmonella enterica serovar Enteritidis, and Listeria monocytogenes strains were inoculated in freshly prepared salmorejo. The food was treated by high hydrostatic pressure (HHP) at 400, 500, or 600 MPa for 8 min, or left untreated, and stored at 4 °C for 30 d. Viable cell counts were determined on selective media and also by the triple-layer agar method in order to detect sublethally injured cells. In control samples, L. monocytogenes viable cells decreased by 2.4 log cycles at day 7 and were undetectable by day 15. S. enterica cells decreased by 0.5 or 2.4 log cycles at days 7 and 15 respectively, but still were detectable at day 30. E. coli O157 cells survived much better in salmorejo, decreasing only by 1.5 log cycles at day 30. Treatments at pressures of 400 MPa or higher reduced viable counts of L. monocytogenes and S. enterica to undetectable levels. HHP treatments significantly (P food, usually produced on a small scale. HHP treatment at 600 MPa for 8 min can be an efficient nonthermal method for industrial-scale preparation of preservative-free salmorejo with improved safety against transmission of foodborne pathogens L. monocytogenes serotyes 4a and 4b, S. enterica serovar Enteritidis, and E. coli O157. © 2015 Institute of Food Technologists®

  12. Listeria monocytogenes, a down-to-earth pathogen.

    Science.gov (United States)

    Vivant, Anne-Laure; Garmyn, Dominique; Piveteau, Pascal

    2013-01-01

    Listeria monocytogenes is the causative agent of the food-borne life threatening disease listeriosis. This pathogenic bacterium received much attention in the endeavor of deciphering the cellular mechanisms that underlie the onset of infection and its ability to adapt to the food processing environment. Although information is available on the presence of L. monocytogenes in many environmental niches including soil, water, plants, foodstuff and animals, understanding the ecology of L. monocytogenes in outdoor environments has received less attention. Soil is an environmental niche of pivotal importance in the transmission of this bacterium to plants and animals. Soil composition, microbial communities and macrofauna are extrinsic edaphic factors that direct the fate of L. monocytogenes in the soil environment. Moreover, farming practices may further affect its incidence. The genome of L. monocytogenes presents an extensive repertoire of genes encoding transport proteins and regulators, a characteristic of the genome of ubiquitous bacteria. Postgenomic analyses bring new insights in the process of soil adaptation. In the present paper focussing on soil, we review these extrinsic and intrinsic factors that drive environmental adaptation of L. monocytogenes.

  13. Evaluation of possible use of disinfectant based on chlorine dioxide in dairy plant

    Directory of Open Access Journals (Sweden)

    Rakić-Martinez Mira

    2009-01-01

    Full Text Available Poor sanitation of food contact surfaces has been a contributing factor in food borne disease outbreaks, especially those involving Listeria monocytogenes, Salmonella spp., Escherichia coli, Staphylococcus aureus etc. The objectives of this study were therefore to: 1. Determine the efficiency of a disinfectant based on chlorine dioxide in suspension in a closed system in a dairy plant. 2. Evaluate the possibility of disinfection of working surfaces with a disinfectant based on chlorine dioxide. In order to determine the germicidal effect of the disinfectant based on chlorine dioxide by suspension test (BSEN 1276:1997; the following test organisms were used: Listeria monocytogenes, Proteus mirabilis, Escherichia coli, Bacillus cereus, Staphylococcus aureus and Pseudomonas aeruginosa clinical isolate. The corrosive properties of the disinfectant based on chlorine dioxide were tested by IDF 077:1977 standard. The efficacy of this disinfectant was investigated in a closed system in a dairy plant. Results indicated a 100% reduction of >108 cfu/ml L. monocytogenes, E. coli, Proteus mirabilis, Pseudomonas aeruginosa, S. aureus, viable count after 1 minute of exposure to 100 ppm of the disinfectant based on chlorine dioxide and 400 ppm for Bacillus cereus. In the presence of 2% skim milk and 4 % skim milk concentrations of 200 and 250 ppm resulted in 100% reduction in numbers of the five of six test microorganisms, respectively. The spore former, Bacillus cereus is less susceptible to the disinfectant. Therefore, the efficient concentration for 100% reduction in viable count after 1 minute exposure was 500 ppm. The corrosive properties of the disinfectant were not determined. In the case of closed system disinfection in a dairy plant, reduction in viable count after 15 minute exposure to 100 ppm of disinfectant based on chlorine dioxide ranged from 80 to 100%.

  14. Gene expression in Listeria monocytogenes exposed to sublethal concentration of benzalkonium chloride.

    Science.gov (United States)

    Tamburro, Manuela; Ripabelli, Giancarlo; Vitullo, Monia; Dallman, Timothy James; Pontello, Mirella; Amar, Corinne Francoise Laurence; Sammarco, Michela Lucia

    2015-06-01

    In this study, tolerance at sublethal concentration of benzalkonium chloride and transcription levels of mdrL, ladR, lde, sigB and bcrABC genes in Listeria monocytogenes strains were evaluated. Viable cells reduction occurred in 45% of strains and clinical isolates showed lower sensitivity than isolates from foods. An increased transcription of an efflux system encoding gene was found in 60% of strains, and simultaneous mdrL overexpression and ladR underexpression occurred in 30% of isolates. A significant association between reduced benzalkonium chloride activity and both mdrL and sigB overexpression was observed; sigB expression also correlated with both mdrL and ladR genes. The bcrABC gene was only found in six strains, all isolated from foods and sensitive to benzalkonium chloride, and in four strains an underexpression was observed. Disinfection at sublethal concentration was less effective in clinical isolates, and mdrL and sigB expression was significantly affected by disinfection. Further insights are needed to understand the adaptation to benzalkonium chloride and to evaluate whether changes in gene expression could affect the L. monocytogenes virulence traits and persistence in the environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Morphological and Physiological Characterization of Listeria monocytogenes Subjected to High Hydrostatic Pressure

    Science.gov (United States)

    Ritz, M.; Tholozan, J. L.; Federighi, M.; Pilet, M. F.

    2001-01-01

    High hydrostatic pressure is a new food preservation technology known for its capacity to inactivate spoilage and pathogenic microorganisms. That inactivation is usually assessed by the number of colonies growing on solid media after treatment. Under normal conditions the method does not permit recovery of damaged cells and may underestimate the number of cells that will remain viable and grow after a few days in high-pressure-processed foodstuffs. This study investigated the damage inflicted on Listeria monocytogenes cells treated by high pressure for 10 min at 400 MPa in pH 5.6 citrate buffer. Under these conditions, no cell growth occurred after 48 h on plate count agar. Scanning electron microscopy, light scattering by flow cytometry, and cell volume measurements were compared to evaluate the morphological changes in cells after pressurization. All these methods revealed that cellular morphology was not really affected. Esterase activity, as assessed either by enzymatic activity assays or by carboxy fluorescein diacetate fluorescence monitored by flow cytometry, was dramatically lowered, but not totally obliterated, under the effects of treatment. The measurement of propidium iodide uptake followed by flow cytometry demonstrated that membrane integrity was preserved in a small part of the population, although the membrane potential measured by analytical methods or evaluated by oxonol uptake was reduced from −86 to −5 mV. These results showed that such combined methods as fluorescent dyes monitored by flow cytometry and physiological activity measurements provide valuable indications of cellular viability. PMID:11319107

  16. Evaluation of a loop-mediated isothermal amplification method for the detection of Listeria monocytogenes in dairy food

    Directory of Open Access Journals (Sweden)

    Erica Tirloni

    2017-12-01

    Full Text Available Objective of the present study was to test the performances of a loop-mediated isothermal amplification (LAMP-based method for the detection of Listeria monocytogenes, with particular focus on the dairy products. The specificity of the method was evaluated on 42 different Listeria spp. strains from collections, food and environmental samples. 100% (32 of 32 of the L. monocytogenes strains were correctly recognised, and none of other 10 Listeria spp. strains was misidentified. The sensitivity was evaluated on four L. monocytogenes strains from different sources. The instrument was able to detect 10-400 CFU/mL. The ability to detect low initial numbers of L. monocytogenes (0.3- 0.7 Log CFU/g was also evaluated, in duplicate, in pasteurised milk (whole and skimmed and dairy samples (fresh ricotta, crescenza, mascarpone, mozzarella, cottage cheese, cream cheese, taleggio, gorgonzola. The analysis was performed after 18, 24 and 48 h of incubation, and was coupled with the count of L. monocytogenes in the broth. Microbial loads were insufficient to achieve a positive result after 18 and 24 h in most of the samples; after 48 h, all the products, except taleggio and one gorgonzola sample, were identified as positive; the sensitivity of the method when applied to contaminated dairy foods was about 5 Log CFU/g. The LAMP method tested can be considered a very useful tool, as it is a costeffective and easy-functioning method. The preliminary data obtained should be confirmed with a validation process taking into account different food typologies.

  17. Construction of a system using a deep learning algorithm to count cell numbers in nanoliter wells for viable single-cell experiments.

    Science.gov (United States)

    Kamatani, Takashi; Fukunaga, Koichi; Miyata, Kaede; Shirasaki, Yoshitaka; Tanaka, Junji; Baba, Rie; Matsusaka, Masako; Kamatani, Naoyuki; Moro, Kazuyo; Betsuyaku, Tomoko; Uemura, Sotaro

    2017-12-04

    For single-cell experiments, it is important to accurately count the number of viable cells in a nanoliter well. We used a deep learning-based convolutional neural network (CNN) on a large amount of digital data obtained as microscopic images. The training set consisted of 103 019 samples, each representing a microscopic grayscale image. After extensive training, the CNN was able to classify the samples into four categories, i.e., 0, 1, 2, and more than 2 cells per well, with an accuracy of 98.3% when compared to determination by two trained technicians. By analyzing the samples for which judgments were discordant, we found that the judgment by technicians was relatively correct although cell counting was often difficult by the images of discordant samples. Based on the results, the system was further enhanced by introducing a new algorithm in which the highest outputs from CNN were used, increasing the accuracy to higher than 99%. Our system was able to classify the data even from wells with a different shape. No other tested machine learning algorithm showed a performance higher than that of our system. The presented CNN system is expected to be useful for various single-cell experiments, and for high-throughput and high-content screening.

  18. Potential of chitosan from Mucor rouxxi UCP064 as alternative natural compound to inhibit Listeria monocytogenes

    Science.gov (United States)

    Bento, Roberta A.; Stamford, Tânia L.M.; de Campos-Takaki, Galba M.; Stamford, Thayza C.M.; de Souza, Evandro L.

    2009-01-01

    Listeria monocytogenes is widely distributed in nature and the infection listeriosis is recognized as a potential threat for human health because of its mortality rate. The objective of this study was to evaluate the growth profile and chitosan production by Mucor rouxxi UCP 064 grown in yam bean (Pachyrhizus erosus L. Urban) medium. It was also to assess the anti-L. monocytogenes efficacy of the obtained chitosan. Higher values of biomass of M. rouxxi (16.9 g.L-1) and best yield of chitosan (62 mg.g-1) were found after 48 h of cultivation. Residual glucose and nitrogen in the growth media were 4.1 and 0.02 g.L-1 after 96 h, respectively. Obtained chitosan presented 85 % of degree of deacetylation and 2.60 x 104 g.mol-1 of viscosimetric molecular weight. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values of chitosan against L. monocytogenes ATCC 7644 were, respectively, 2.5 and 5.0 mg.mL-1. At 2.5 and 5.0 mg.mL-1 chitosan caused cidal effect in a maximum time of 4 h. Bacterial count below 2 log cfu.mL-1 were found from 2 h onwards and no recovery in bacterial growth was noted in the remainder period. These results show the biotechnological potential of yam bean medium for chitosan production by Mucor rouxxi and support the possible rational use of chitosan from fungi as natural antimicrobial to control L. monocytogenes. PMID:24031403

  19. Control of Listeria monocytogenes in goat's milk and goat's jben by the bacteriocinogenic Enterococcus faecium F58 strain.

    Science.gov (United States)

    Achemchem, Fouad; Abrini, Jamal; Martínez-Bueno, Manuel; Valdivia, Eva; Maqueda, Mercedes

    2006-10-01

    The bacteriocinogenic Enterococcus faecium F58 strain, a natural goat's jben cheese isolate, lacks decarboxylase activity involved in most biogenic amine formation. It was also sensitive to 13 antibiotics assayed and free of virulence and vancomycin resistance genes. The F58 strain reached the stationary phase after 12 h of growth in sterile goat's milk, and the production of enterocin F-58 (Ent L50) was first detected after 48 h (400 AU/ml), thereafter remaining stable up to 5 days. The effectiveness of the F58 strain in controlling Listeria monocytogenes serovar 4b in reduced fat and whole goat's milk, and in goat's jben has been examined. Coculture experiments of F58-L. monocytogenes in both types of milk demonstrated that listeriae were not eliminated, although reductions by 1 to 4 log units were found. Nevertheless, when the F58 strain was previously inoculated in whole milk and left to grow for 12 h before contamination, the pathogen was completely eliminated after 130 h of coculture. Production of jben cheese contaminated with L. monocytogenes prior to packaging, using preparations of F58-producer strain, caused a significant decrease in the number of viable listeriae, which were undetectable after 1 week of cheese storage at 22 degrees C. Altogether, results from this study suggest that E. faecium F58 strain may be used as an adjunct culture in cheese to control contamination and growth of L. monocytogenes by in situ enterocin production, thus providing an additional hurdle to enhance control of this pathogen.

  20. Occurrence of Listeria monocytogenes in smoked fish in Sokoto ...

    African Journals Online (AJOL)

    STORAGESEVER

    2008-09-03

    Sep 3, 2008 ... monocytogenes and other Listeria species are common contaminant of smoked fish, and this may pose serious public health implications. Key words: Smoked fish, Listeria monocytogenes, contamination, public health. INTRODUCTION ... L. monocytogenes belong to the recently emerging psychrotrophic ...

  1. Listeria monocytogenes infection in pregnancy and neonatal sepsis

    Directory of Open Access Journals (Sweden)

    Francesca Pascale

    2008-06-01

    Full Text Available Authors report a fatal neonatal sepsis caused by Listeria monocytogenes. While the diagnostic procedure aimed to identify the microrganism is described, it is emphasized the importance to recover Streptococcus agalactiae (GBS and L. monocytogenes by means of vaginal-rectal swab culture. The intrapartum screening for L. monocytogenes, by Polymerase Chain Reaction (PCR providing results in 75 minutes is also evaluated.

  2. Listeria monocytogenes - Danger for health safety vegetable production.

    Science.gov (United States)

    Kljujev, Igor; Raicevic, Vera; Jovicic-Petrovic, Jelena; Vujovic, Bojana; Mirkovic, Milica; Rothballer, Michael

    2018-04-22

    The microbiologically contaminated vegetables represent a risk for consumers, especially vegetables without thermal processing. It is known that human pathogen bacteria, such as Listeria monocytogenes, could exist on fresh vegetables. The fresh vegetables could become Listeria-contaminated if they come in touch with contaminated soil, manure, irrigation water. The aim of this work was to investigate the presence of Listeria spp. and L. monocytogenes in different kind of vegetables grown in field and greenhouse condition as well as surface and endophytic colonization plant roots of different vegetables species by L. monocytogenes in laboratory conditions. The detection of Listeria spp. and L. monocytogenes in vegetable samples was done using ISO and PCR methods. The investigation of colonization vegetable roots and detection Listeria-cells inside plant root tissue was done using Fluorescence in situ hybridization (FISH) method in combination with confocal laser scanning microscopy (CLSM). The results showed that 25.58% vegetable samples were positive for Listeria spp. and only one sample (carrot) was positive for L. monocytogenes out of 43 samples in total collected from field and greenhouse. The strain L. monocytogenes EGD-E surface and endophytic colonized carrot root in highest degree while strain L. monocytogenes SV4B was the most represented at leafy vegetable plants, such at lettuce (1.68 × 10 6  cells/mm 3 absolutely dry root) and spinach (1.39 × 10 6  cells/mm 3 absolutely dry root) root surface. The cells of L. monocytogenes SV4B were visible as single cells in interior tissue of plant roots (celery and sweet corn roots) as well as in the interior of the plant root cell at sweet corn root. The cells of L. monocytogenes EGD-E bind to the surface of the plant root and they were less commonly found out on root hair. In the inner layers of the root, those bacterial cells were inhabited intercellular spaces mainly as single cells very close to the

  3. Listeria monocytogenes serovar 4a is a possible evolutionary intermediate between L. monocytogenes serovars 1/2a and 4b and L. innocua.

    Science.gov (United States)

    Chen, Jianshun; Jiang, Lingli; Chen, Xueyan; Luo, Xiaokai; Chen, Yang; Yu, Ying; Tian, Guoming; Liu, Dongyou; Fang, Weihuan

    2009-03-01

    The genus Listeria consists of six closely related species and forms three phylogenetic groups: L. monocytogenes- L. innocua, L. ivanovii-L. seeligeri-L. welshimeri, and L. grayi. In this report, we attempted to examine the evolutionary relationship in the L. monocytogenes-L. innocua group by probing the nucleotide sequences of 23S rRNA and 16S rRNA, and the gene clusters lmo0029-lmo0042, ascBdapE, rplS-infC, and prs-ldh in L. monocytogenes serovars 1/2a, 4a, and 4b, and L. innocua. Additionally, we assessed the status of L. monocytogenes-specific inlA and inlB genes and 10 L. innocua-specific genes in these species/serovars, together with phenotypic characterization by using in vivo and in vitro procedures. The results indicate that L. monocytogenes serovar 4a strains are genetically similar to L. innocua in the lmo0035-lmo0042, ascB-dapE, and rplS-infC regions and also possess L. innocua-specific genes lin0372 and lin1073. Furthermore, both L. monocytogenes serovar 4a and L. innocua exhibit impaired intercellular spread ability and negligible pathogenicity in mouse model. On the other hand, despite resembling L. monocytogenes serovars 1/2a and 4b in having a nearly identical virulence gene cluster, and inlA and inlB genes, these serovar 4a strains differ from serovars 1/2a and 4b by harboring notably altered actA and plcB genes, displaying strong phospholipase activity and subdued in vivo and in vitro virulence. Thus, by possessing many genes common to L. monocytogenes serovars 1/2a and 4b, and sharing many similar gene deletions with L. innocua, L. monocytogenes serovar 4a represents a possible evolutionary intermediate between L. monocytogenes serovars 1/2a and 4b and L. innocua.

  4. Combined effect of ultrasound and essential oils to reduce Listeria monocytogenes on fresh produce.

    Science.gov (United States)

    Özcan, Gülçin; Demirel Zorba, Nükhet Nilüfer

    2016-06-01

    Salads prepared from contaminated fresh produce have a high risk of causing food-borne illnesses. Essential oils obtained from plants have antimicrobial activity and may provide a natural approach to reduce the pathogens on fresh produce. Additionally, ultrasound treatments have been shown to reduce the microbial counts on different foods. The objective of this study was to investigate the antimicrobial activities of cinnamon and lemon essential oils in vitro and in food applications. Mixtures of lettuce, parsley and dill were inoculated with Listeria monocytogenes and then dip-treated for 5 min in one of the following treatments: sterile tap water, chlorinated water, 1% lemon essential oil, 2% cinnamon essential oil or 2% cinnamon essential oil + ultrasound. The samples were stored at 4 ℃ and collected at d 0, 1, 3, 5, 7 and 9 post inoculation. The 1% lemon (4 log) and 2% cinnamon (2 log) essential oil washes provided partial inhibition against L. monocytogenes by d 1. The combined application of 2% cinnamon oil and ultrasound resulted in only 0.85 log inhibition by d 1; however, the number of L. monocytogenes increased during storage and became nearly equal to the control at d 9. Therefore, different combinations of essential oils with other antimicrobials or novel technologies are required. © The Author(s) 2015.

  5. Biofilm Formation of Listeria monocytogenes on Various Surfaces

    Directory of Open Access Journals (Sweden)

    M Mahdavi

    2007-10-01

    Full Text Available Introduction & Objective: Listeria monocytogenes is considered as a ubiquitous foodborne pathogen which can lead to serious infections, especially in newborns, elderly, pregnant, and immunocompromised people. The organism has been isolated from many foods and may cause meningitis, septicemia and abortion in pregnant women. Also L. monocytogenes forms biofilms on many food contact surface materials and medical devices. Development of biofilms on many surfaces is a potential source of contamination of foods that may lead to spoilage or transmission of foodborne pathogens. Materials & Methods: Biofilm formation of L. monocytogenes (RITCC 1293 serotype 4a was investigated. Hydrophobicity of L. monocytogenes was measured by MATH method. Then biofilm formation of the organism was assessed at 2, 4, 8, 16 and 20 hours on stainless steel (type 304 no 2B, polyethylene and glass by drop plate method. Results: Results indicated that L. monocytogenes with 85% of hydrophobicity formed biofilm on each of three surfaces. Biofilm formation on stainless steel surfaces was significantly more than other surfaces (p<0.05. Conclusion: The ability of biofilm formation of L. monocytogenes on medical devices and food containers is very important as far as hygiene and disease outbreaks are concerned.

  6. 78 FR 27939 - Draft Interagency Risk Assessment-Listeria monocytogenes

    Science.gov (United States)

    2013-05-13

    ... Listeria (L.) monocytogenes contamination of certain ready-to-eat (RTE) foods, for example cheese, deli... Scott, V.N., Survey of Listeria monocytogenes in ready-to-eat foods. Journal of Food Protection, 2003... monocytogenes in ready-to-eat processed meat and poultry collected in four FoodNet states in International...

  7. Presence of Listeria monocytogenes in Mediterranean-Style Dry Fermented Sausages

    Directory of Open Access Journals (Sweden)

    Domenico Meloni

    2015-03-01

    Full Text Available The morphological, physiological and epidemiological features of L. monocytogenes, together with the severity of human listeriosis infections, make L. monocytogenes of particular concern for manufacturers of cold-stored “ready to eat” (RTE foods. L. monocytogenes has been isolated from a wide variety of RTE foods and is responsible for several outbreaks associated with the consumption of RTE meat, poultry, dairy, fish and vegetable products. Although L. monocytogenes is among the most frequently-detected pathogens in dry fermented sausages, these products could be included in the category of RTE products in which the growth of L. monocytogenes is not favored and have rarely been implicated in listeriosis outbreaks. However, L. monocytogenes is highly difficult to control in fermented sausage processing environments due to its high tolerance to low pH and high salt concentration. In many Mediterranean-style dry fermented sausages, an empirical application of the hurdle technology often occurs and the frequent detection of L. monocytogenes in these products at the end of ripening highlights the need for food business operators to properly apply hurdle technology and to control the contamination routes of L. monocytogenes in the processing plants. In the following, through an up-to-date review of (personal and un- published data, the main aspects of the presence of L. monocytogenes in Mediterranean-style dry fermented sausages will be discussed.

  8. Presence of Listeria monocytogenes in Mediterranean-Style Dry Fermented Sausages.

    Science.gov (United States)

    Meloni, Domenico

    2015-03-12

    The morphological, physiological and epidemiological features of L. monocytogenes , together with the severity of human listeriosis infections, make L. monocytogenes of particular concern for manufacturers of cold-stored "ready to eat" (RTE) foods. L. monocytogenes has been isolated from a wide variety of RTE foods and is responsible for several outbreaks associated with the consumption of RTE meat, poultry, dairy, fish and vegetable products. Although L. monocytogenes is among the most frequently-detected pathogens in dry fermented sausages, these products could be included in the category of RTE products in which the growth of L. monocytogenes is not favored and have rarely been implicated in listeriosis outbreaks. However, L. monocytogenes is highly difficult to control in fermented sausage processing environments due to its high tolerance to low pH and high salt concentration. In many Mediterranean-style dry fermented sausages, an empirical application of the hurdle technology often occurs and the frequent detection of L. monocytogenes in these products at the end of ripening highlights the need for food business operators to properly apply hurdle technology and to control the contamination routes of L. monocytogenes in the processing plants. In the following, through an up-to-date review of (personal and un-) published data, the main aspects of the presence of L. monocytogenes in Mediterranean-style dry fermented sausages will be discussed.

  9. Incorporation of Listeria monocytogenes strains in raw milk biofilms.

    Science.gov (United States)

    Weiler, Christiane; Ifland, Andrea; Naumann, Annette; Kleta, Sylvia; Noll, Matthias

    2013-02-01

    Biofilms develop successively on devices of milk production without sufficient cleaning and originate from the microbial community of raw milk. The established biofilm matrices enable incorporation of pathogens like Listeria monocytogenes, which can cause a continuous contamination of food processing plants. L. monocytogenes is frequently found in raw milk and non-pasteurized raw milk products and as part of a biofilm community in milk meters and bulk milk tanks. The aim of this study was to analyze whether different L. monocytogenes strains are interacting with the microbial community of raw milk in terms of biofilm formation in the same manner, and to identify at which stage of biofilm formation a selected L. monocytogenes strain settles best. Bacterial community structure and composition of biofilms were analyzed by a cloning and sequencing approach and terminal restriction fragment length polymorphism analysis (T-RFLP) based on the bacterial 16S rRNA gene. The chemical composition of biofilms was analyzed by Fourier transform infrared spectroscopy (FTIR), while settled L. monocytogenes cells were quantified by fluorescence in situ hybridization (FISH). Addition of individual L. monocytogenes strains to raw milk caused significant shifts in the biofilm biomass, in the chemical as well as in the bacterial community composition. Biofilm formation and attachment of L. monocytogenes cells were not serotype but strain specific. However, the added L. monocytogenes strains were not abundant since mainly members of the genera Citrobacter and Lactococcus dominated the bacterial biofilm community. Overall, added L. monocytogenes strains led to a highly competitive interaction with the raw milk community and triggered alterations in biofilm formation. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Listeria monocytogenes as a vector for anti-cancer therapies.

    LENUS (Irish Health Repository)

    Tangney, Mark

    2012-01-31

    The intracellular pathogen Listeria monocytogenes represents a promising therapeutic vector for the delivery of DNA, RNA or protein to cancer cells or to prime immune responses against tumour-specific antigens. A number of biological properties make L. monocytogenes a promising platform for development as a vector for either gene therapy or as an anti-cancer vaccine vector. L. monocytogenes is particularly efficient in mediating internalization into host cells. Once inside cells, the bacterium produces specific virulence factors which lyse the vaculolar membrane and allow escape into the cytoplasm. Once in the cytosol, L. monocytogenes is capable of actin-based motility and cell-to-cell spread without an extracellular phase. The cytoplasmic location of L. monocytogenes is significant as this potentiates entry of antigens into the MHC Class I antigen processing pathway leading to priming of specific CD8(+) T cell responses. The cytoplasmic location is also beneficial for the delivery of DNA (bactofection) by L. monocytogenes whilst cell-to-cell spread may facilitate access of the vector to cells throughout the tumour. Several preclinical studies have demonstrated the ability of L. monocytogenes for intracellular gene or protein delivery in vitro and in vivo, and this vector has also displayed safety and efficacy in clinical trial. Here, we review the features of the L. monocytogenes host-pathogen interaction that make this bacterium such an attractive candidate with which to induce appropriate therapeutic responses. We focus primarily upon work that has led to attenuation of the pathogen, demonstrated DNA, RNA or protein delivery to tumour cells as well as research that shows the efficacy of L. monocytogenes as a vector for tumour-specific vaccine delivery.

  11. Prevalence and growth of Listeria monocytogenes in naturally contaminated seafood

    DEFF Research Database (Denmark)

    Jørgensen, Lasse Vigel; Huss, Hans Henrik

    1998-01-01

    Listeria monocytogenes contamination of seafood varies with product category. The highest prevalence was found in cold- smoked fish (34-60%), while the lowest was found in heat- treated and cured seafood (4-12%). The prevalence of L. monocytogenes differed greatly in cold-smoked salmon between...... production sites, ranging from monocytogenes. The organism showed moderate growth...... in naturally contaminated cold-smoked, and 'gravad', fish while the growth appeared faster in hot smoked fish. Thus L. monocytogenes is not under control in these products. Finally, the prevalence and growth of L. monocytogenes in naturally contaminated cold-smoked salmon are discussed in relation...

  12. Listeria monocytogenes endophthalmitis following keratoconjunctivitis

    Directory of Open Access Journals (Sweden)

    Shoughy SS

    2014-01-01

    Full Text Available Samir S Shoughy,1 Khalid F Tabbara1–31The Eye Center and The Eye Foundation for Research in Ophthalmology, Riyadh, Saudi Arabia; 2Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia; 3The Wilmer Ophthalmological Institute of The Johns Hopkins University School of Medicine, Baltimore, MD, USAAbstract: Endophthalmitis due to endogenous or exogenous bacteria is a rare infection of the eye. We report a case of endophthalmitis following Listeria monocytogenes keratoconjunctivitis in a 27-year-old healthy white male presenting with hand motion visual acuity, right eye mucopurulent conjunctivitis, elevated intraocular pressure, and pigmented hypopyon 6 months post-keratectomy. The conjunctivitis was unresponsive to a 5-day course of topical tobramycin eye drops, and the patient developed keratitis with pain that progressed to endophthalmitis after 21 days. Diagnostic B-scan revealed vitreous exudates. Intraocular fluid specimen showed Gram-positive organisms and the aqueous culture grew penicillin-/aminoglycoside-sensitive L. monocytogenes. The patient was given intravitreal and systemic vancomycin and ceftazidime. The eye was unresponsive to intravenous penicillin and gentamicin; the anterior chamber progressively flattened and developed phthisis bulbi. L. monocytogenes keratoconjunctivitis may lead to bacterial endophthalmitis. Prompt culture and early antibiotic therapy are recommended.Keywords: conjunctivitis, L. monocytogenes, endophthalmitis

  13. Isolation of a bacteriocin-producing Lactococcus lactis subsp. lactis and application to control Listeria monocytogenes in Moroccan jben.

    Science.gov (United States)

    Benkerroum, N; Oubel, H; Zahar, M; Dlia, S; Filali-Maltouf, A

    2000-12-01

    Use of a bacteriocin-producing lactococcal strain to control Listeria monocytogenes in jben. A Lactococcus lactis strain isolated from lben was shown, by the spot technique, to produce a bacteriocin different from nisin. Inhibitory activity of the bacteriocin-producing strain against Listeria monocytogenes was investigated in jben, made from cow's milk fermented with the producer organism and contaminated with 104 or 107 cfu ml-1. Listeria counts were monitored during manufacture, and during conservation at room and at refrigeration temperatures. Results showed that the pathogen was reduced by 2.7 logarithmic units after 30 h of jben processing when the initial inoculum of 107 cfu ml(-1) was used. For the initial inoculum of 104 cfu ml(-1), the bacterium was completely eliminated at 24 h. Furthermore, the use of the bacteriocin-producing starter culture extended the shelf-life of jben by 5 days. In situ production of the lactococcal bacteriocin is an efficient biological means of controlling L. monocytogenes in jben and of allowing shelf-life extension. The proposed technology will essentially benefit minimally processed dairy products and those made with raw milk.

  14. Listeria monocytogenes contamination in dairy plants: evaluation of Listeria monocytogenes environmental contamination in two cheese-making plants using sheeps milk

    Directory of Open Access Journals (Sweden)

    Michela Ibba

    2013-09-01

    Full Text Available Listeria monocytogenes harbouring niches established in the processing plant support post-process contamination of dairy products made from pasteurised or thermised milk. The present study investigated L. monocytogenes environmental contamination in two sheep’s milk cheese-making plants. Persistence of contamination in the area at higher risk was also investigated. During a one-year survey 7 samplings were carried out in each dairy plant, along the production lines of Pecorino Romano and ricotta salata cheese. A total of 613 environmental samples collected from food contact and non-food contact surfaces were analysed according to ISO 11290-1:2005 standard method. Identification of the isolated strains was carried out by polymerase chain reaction. L. monocytogenes prevalence was 23.2% in dairy A and 13.1% in dairy B, respectively. The higher prevalence rate was found in the following areas: salting, products washing, packaging, ricotta salata storage and Pecorino Romano ripening rooms. L. monocytogenes was never found in the cheese-making area. The probability of observing samples positive for the presence of L. monocytogenes was asso- ciated with dairy plant, sampling area and the period of cheese-making (P<0.001. The greater persistence of contamination over time was observed in the washing, salting, and Pecorino Romano ripening areas. The control of persistent environmental contamination relies on the identification of L. monocytogenes niches within the processing environment and the prevention of harborage sites formation. The importance of strict cleaning and sanitising procedure in controlling L. monocytogenes environmental contamination is confirmed by the lower level of contamination observed after these procedures were correctly implemented.

  15. Viable Mycobacterium avium ssp. paratuberculosis isolated from calf milk replacer.

    Science.gov (United States)

    Grant, Irene R; Foddai, Antonio C G; Tarrant, James C; Kunkel, Brenna; Hartmann, Faye A; McGuirk, Sheila; Hansen, Chungyi; Talaat, Adel M; Collins, Michael T

    2017-12-01

    When advising farmers on how to control Johne's disease in an infected herd, one of the main recommendations is to avoid feeding waste milk to calves and instead feed calf milk replacer (CMR). This advice is based on the assumption that CMR is free of viable Mycobacterium avium ssp. paratuberculosis (MAP) cells, an assumption that has not previously been challenged. We tested commercial CMR products (n = 83) obtained from dairy farms around the United States by the peptide-mediated magnetic separation (PMS)-phage assay, PMS followed by liquid culture (PMS-culture), and direct IS900 quantitative PCR (qPCR). Conventional microbiological analyses for total mesophilic bacterial counts, coliforms, Salmonella, coagulase-negative staphylococci, streptococci, nonhemolytic Corynebacterium spp., and Bacillus spp. were also performed to assess the overall microbiological quality of the CMR. Twenty-six (31.3%) of the 83 CMR samples showed evidence of the presence of MAP. Seventeen (20.5%) tested positive for viable MAP by the PMS-phage assay, with plaque counts ranging from 6 to 1,212 pfu/50 mL of reconstituted CMR (average 248.5 pfu/50 mL). Twelve (14.5%) CMR samples tested positive for viable MAP by PMS-culture; isolates from all 12 of these samples were subsequently confirmed by whole-genome sequencing to be different cattle strains of MAP. Seven (8.4%) CMR samples tested positive for MAP DNA by IS900 qPCR. Four CMR samples tested positive by both PMS-based tests and 5 CMR samples tested positive by IS900 qPCR plus one or other of the PMS-based tests, but only one CMR sample tested positive by all 3 MAP detection tests applied. All conventional microbiology results were within current standards for whole milk powders. A significant association existed between higher total bacterial counts and presence of viable MAP indicated by either of the PMS-based assays. This represents the first published report of the isolation of viable MAP from CMR. Our findings raise concerns

  16. [Study on modeling method of total viable count of fresh pork meat based on hyperspectral imaging system].

    Science.gov (United States)

    Wang, Wei; Peng, Yan-Kun; Zhang, Xiao-Li

    2010-02-01

    Once the total viable count (TVC) of bacteria in fresh pork meat exceeds a certain number, it will become pathogenic bacteria. The present paper is to explore the feasibility of hyperspectral imaging technology combined with relevant modeling method for the prediction of TVC in fresh pork meat. For the certain kind of problem that has remarkable nonlinear characteristic and contains few samples, as well as the problem that has large amount of data used to express the information of spectrum and space dimension, it is crucial to choose a logical modeling method in order to achieve good prediction result. Based on the comparative result of partial least-squares regression (PLSR), artificial neural networks (ANNs) and least square support vector machines (LS-SVM), the authors found that the PLSR method was helpless for nonlinear regression problem, and the ANNs method couldn't get approving prediction result for few samples problem, however the prediction models based on LS-SVM can give attention to the little training error and the favorable generalization ability as soon as possible, and can make them well synchronously. Therefore LS-SVM was adopted as the modeling method to predict the TVC of pork meat. Then the TVC prediction model was constructed using all the 512 wavelength data acquired by the hyperspectral imaging system. The determination coefficient between the TVC obtained with the standard plate count for bacterial colonies method and the LS-SVM prediction result was 0.987 2 and 0.942 6 for the samples of calibration set and prediction set respectively, also the root mean square error of calibration (RMSEC) and the root mean square error of prediction (RMSEP) was 0.207 1 and 0.217 6 individually, and the result was considerably better than that of MLR, PLSR and ANNs method. This research demonstrates that using the hyperspectral imaging system coupled with the LS-SVM modeling method is a valid means for quick and nondestructive determination of TVC of pork

  17. Listeria monocytogenes endophthalmitis following keratoconjunctivitis.

    Science.gov (United States)

    Shoughy, Samir S; Tabbara, Khalid F

    2014-01-01

    Endophthalmitis due to endogenous or exogenous bacteria is a rare infection of the eye. We report a case of endophthalmitis following Listeria monocytogenes keratoconjunctivitis in a 27-year-old healthy white male presenting with hand motion visual acuity, right eye mucopurulent conjunctivitis, elevated intraocular pressure, and pigmented hypopyon 6 months post-keratectomy. The conjunctivitis was unresponsive to a 5-day course of topical tobramycin eye drops, and the patient developed keratitis with pain that progressed to endophthalmitis after 21 days. Diagnostic B-scan revealed vitreous exudates. Intraocular fluid specimen showed Gram-positive organisms and the aqueous culture grew penicillin-/aminoglycoside-sensitive L. monocytogenes. The patient was given intravitreal and systemic vancomycin and ceftazidime. The eye was unresponsive to intravenous penicillin and gentamicin; the anterior chamber progressively flattened and developed phthisis bulbi. L. monocytogenes keratoconjunctivitis may lead to bacterial endophthalmitis. Prompt culture and early antibiotic therapy are recommended.

  18. Microbiological profile and incidence of Salmonella and Listeria monocytogenes on hydroponic bell peppers and greenhouse cultivation environment.

    Science.gov (United States)

    Avila-Vega, Dulce E; Alvarez-Mayorga, Beatriz; Arvizu-Medrano, Sofía M; Pacheco-Aguilar, Ramiro; Martínez-Peniche, Ramón; Hernández-Iturriaga, Montserrat

    2014-11-01

    The aim of this study was to generate information regarding the microbiological profile, including Salmonella and Listeria monocytogenes incidence, of hydroponically grown bell peppers and materials associated with their production in greenhouses located in Mexico. Samples of coconut fiber (24), knives (30), drippers (20), conveyor belts (161), pepper transportation wagons (30), air (178), water (16), nutrient solution for plant irrigation (78), and bell pepper fruits (528) were collected during one cycle of production (2009 to 2010) for the quantification of microbial indicators (aerobic plate counts [APC], molds, coliforms, and Escherichia coli) and the detection of Salmonella and L. monocytogenes. With regard to surfaces (conveyor belts and wagons) and utensils (knives and drippers), the APC, coliform, and mold counts ranged from 3.0 to 6.0, from 1.4 to 6.3, and from 3.6 to 5.2 log CFU/100 cm(2) or per utensil, respectively. The air in the greenhouse contained low median levels of APC (1.2 to 1.4 log CFU/100 liters) and molds (2.2 to 2.5 log CFU/100 liters). The median content of APC and coliforms in water were 0.5 log CFU/ml and 0.3 log MPN/100 ml, respectively. The median content of coliforms in nutrient solution ranged from 1.8 to 2.4 log MPN/100 ml, and E. coli was detected in 18 samples (range, fruit, respectively; E. coli was detected in 5.1% of the samples (range, 0.23 to 1.4 log MPN per fruit). Salmonella was isolated from only one sample (1.6%) of conveyor belt located at the packing area and in four bell pepper samples (3%). L. monocytogenes was not detected. This information could help producers to establish effective control measures to prevent the presence of foodborne pathogens in bell peppers based on a scientific approach.

  19. Quantifying Listeria monocytogenes prevalence and concentration in minced pork meat and estimating performance of three culture media from presence/absence microbiological testing using a deterministic and stochastic approach.

    Science.gov (United States)

    Andritsos, Nikolaos D; Mataragas, Marios; Paramithiotis, Spiros; Drosinos, Eleftherios H

    2013-12-01

    Listeria monocytogenes poses a serious threat to public health, and the majority of cases of human listeriosis are associated with contaminated food. Reliable microbiological testing is needed for effective pathogen control by food industry and competent authorities. The aims of this work were to estimate the prevalence and concentration of L. monocytogenes in minced pork meat by the application of a Bayesian modeling approach, and also to determine the performance of three culture media commonly used for detecting L. monocytogenes in foods from a deterministic and stochastic perspective. Samples (n = 100) collected from local markets were tested for L. monocytogenes using in parallel the PALCAM, ALOA and RAPID'L.mono selective media according to ISO 11290-1:1996 and 11290-2:1998 methods. Presence of the pathogen was confirmed by conducting biochemical and molecular tests. Independent experiments (n = 10) for model validation purposes were performed. Performance attributes were calculated from the presence-absence microbiological test results by combining the results obtained from the culture media and confirmative tests. Dirichlet distribution, the multivariate expression of a Beta distribution, was used to analyze the performance data from a stochastic perspective. No L. monocytogenes was enumerated by direct-plating (media were best at ruling in L. monocytogenes presence than ruling it out. Sensitivity and specificity varied depending on the culture-dependent method. None of the culture media was perfect in detecting L. monocytogenes in minced pork meat alone. The use of at least two culture media in parallel enhanced the efficiency of L. monocytogenes detection. Bayesian modeling may reduce the time needed to draw conclusions regarding L. monocytogenes presence and the uncertainty of the results obtained. Furthermore, the problem of observing zero counts may be overcome by applying Bayesian analysis, making the determination of a test performance feasible

  20. Occurrence of Salmonella, Listeria monocytogenes, and enterotoxigenic Staphylococcus in goat milk from small and medium-sized farms located in Minas Gerais State, Brazil.

    Science.gov (United States)

    Cavicchioli, V Q; Scatamburlo, T M; Yamazi, A K; Pieri, F A; Nero, L A

    2015-12-01

    Consumption of goat milk has been increasing due to its nutritional characteristics and health benefits. Therefore, assessment of the presence of foodborne pathogens in this product is critical to ensure its safety to consumers. The present study aimed to identify common foodborne pathogens in raw goat milk. Fifty-three samples of raw goat milk from 11 farms were collected and cultured for the presence of Salmonella spp. and Listeria monocytogenes, as well as for enumeration and isolation of coagulase-positive and coagulase-negative Staphylococcus (CPS and CNS, respectively). All samples tested negative for Salmonella spp. and L. monocytogenes. The CPS counts in raw goat milk samples were predominantly less than 2 log cfu/mL (n=39), and CNS counts were predominantly higher than 3 log cfu/mL (n=42). Based on Staphylococcus counts, 51 isolates were selected (CPS=26; CNS=25) and tested by PCR for the presence of classic enterotoxin-encoding genes (sea, seb, sec, sed, and see). Only 3 isolates (CPS=2, CNS=1) were negative for all enterotoxin-encoding genes tested, and the genotype sec and see was the most frequent (n=16), followed by sea, sec, and see (n=13) and sec (n=13); sed was not detected in any isolate. The frequencies of enterotoxin-encoding genes for CPS and CNS were similar, demonstrating the equivalence of both groups in harboring these virulent markers. These results suggest that Salmonella and L. monocytogenes are not frequent contaminants of raw goat milk, but that Staphylococcus spp. that are capable of producing enterotoxins are prevalent; therefore, consumers of raw goat milk and products made from raw milk are at risk. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  1. Listeria monocytogenes Monographic Study

    Directory of Open Access Journals (Sweden)

    Emil Tirziu

    2010-05-01

    Full Text Available Listeria monocytogenes is a ubiquitous bacteria with a remarkable resistance in discordant condition which produce listeriosis, an infectious disease that affects multiple domestic and wild animals’ species, but also humans. Receptive to listeriosis are the majority of domestic or wild mammals and birds, in the last years being registered an increase of receptivity in humans. The concept of listeriosis in human pathology, a disease caused by eating or drinking contaminated food and water, appeared for the first time in 1981, during an outbreak in Canada with seven cases in adults and 34 cases of maternalfetal listeriosis. The alimentary origin of human listeriosis can be easily explained if considered some general characteristics of the bacteria. Thus, resistance in various conditions, especially at lower temperatures, justifies its dissemination and food contamination, particularly when is conserved by refrigeration. Also, L. monocytogenes has a significant presence in alimentary products. Some studies showed that 4% of the milk products, 29% of the meat products, 5% of the vegetable products and 26% of the products obtained from fishes and shell fishes are positive for L. monocytogenes, which allows us to say that battle against these bacteria is a war against microbial contamination.

  2. Dynamics of biofilm formation by Listeria monocytogenes on stainless steel under mono-species and mixed-culture simulated fish processing conditions and chemical disinfection challenges.

    Science.gov (United States)

    Papaioannou, Eleni; Giaouris, Efstathios D; Berillis, Panagiotis; Boziaris, Ioannis S

    2018-02-21

    The progressive ability of a six-strains L. monocytogenes cocktail to form biofilm on stainless steel (SS), under fish-processing simulated conditions, was investigated, together with the biocide tolerance of the developed sessile communities. To do this, the pathogenic bacteria were left to form biofilms on SS coupons incubated at 15°C, for up to 240h, in periodically renewable model fish juice substrate, prepared by aquatic extraction of sea bream flesh, under both mono-species and mixed-culture conditions. In the latter case, L. monocytogenes cells were left to produce biofilms together with either a five-strains cocktail of four Pseudomonas species (fragi, savastanoi, putida and fluorescens), or whole fish indigenous microflora. The biofilm populations of L. monocytogenes, Pseudomonas spp., Enterobacteriaceae, H 2 S producing and aerobic plate count (APC) bacteria, both before and after disinfection, were enumerated by selective agar plating, following their removal from surfaces through bead vortexing. Scanning electron microscopy was also applied to monitor biofilm formation dynamics and anti-biofilm biocidal actions. Results revealed the clear dominance of Pseudomonas spp. bacteria in all the mixed-culture sessile communities throughout the whole incubation period, with the in parallel sole presence of L. monocytogenes cells to further increase (ca. 10-fold) their sessile growth. With respect to L. monocytogenes and under mono-species conditions, its maximum biofilm population (ca. 6logCFU/cm 2 ) was reached at 192h of incubation, whereas when solely Pseudomonas spp. cells were also present, its biofilm formation was either slightly hindered or favored, depending on the incubation day. However, when all the fish indigenous microflora was present, biofilm formation by the pathogen was greatly hampered and never exceeded 3logCFU/cm 2 , while under the same conditions, APC biofilm counts had already surpassed 7logCFU/cm 2 by the end of the first 96h of

  3. Survival of Listeria monocytogenes and Salmonella typhimurium and quality attributes of cooked pork chops and cured ham after irradiation

    International Nuclear Information System (INIS)

    Fu, A.H.; Sebranek, J.G.; Murano, E.A.

    1995-01-01

    Cooked pork chops (pumped with salt/polyphosphate brine or untreated) and cured hams were inoculated with Listeria monocytogenes and Salmonella typhimurium. The samples were irradiated at low (0.75 to 0.90 kGy) or medium doses (1.8 to 2.0 kGy), and each dose was delivered at either a low (2.5 M/min conveyor speed) or high (5.4 M/min) dose rate. Low-dose irradiation reduced L. monocytogenes by more than 2 log and S. typhimurium by 1 to 3 log. Pathogen populations and total plate counts (TPC) were reduced to undetectable levels by medium doses. No meat quality attributes were affected, and no dose rate effect was observed. Nitrite reduced (P 0.05) both pathogens and TPC during 7 degrees C storage in ham, especially when combined with low-dose irradiation

  4. Efecto de tiempo y temperatura de cocción en chorizo inoculados artificialmente con Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Ana K. Carrascal-Camacho

    2009-12-01

    Full Text Available Effect of cooking time and temperature on sausages artificially inoculated with Listeria monocytogenes. Objective. To find whetherthe cooking times traditionally used by consumers are enough to inactivate Listeria monocytogenes artificially inoculated into sausages.Materials and methods. A survey asking about sausage cooking habits was completed with 50 housewives. We analyzed 60 samples ofsausages previously inoculated with 103 CFU g-1 from a pool of 5 strains of L. monocytogenes, then the cooking procedures described inthe survey were applied to the samples, and counting was done immediately after. Additionally, a complementary test was carried out byinoculating 20 samples of sausages with 103 CFU g-1 and exposing them to 72 oC and 73 oC for 30 seg. Results. The survey showed that15 minute boiling and 5 minute frying are the most frequent ways of preparing sausages by consumers. We established that the time andcooking conditions used in our assay had a statistically significant effect (p: 0.016 on the inoculated samples. In the complementary assay,statistical data (p: 0.0001 indicated that internal temperatures of 73 oC are enough to inactivate the pathogen at an industrial scale.Conclusion. Cooking by 15 minute boiling and 5 minute frying are enough to inactive concentrations of 103 g-1 of Listeria monocytogenesartificially inoculated into sausages.

  5. The effect of ozone and open air factor on surface-attached and biofilm environmental Listeria monocytogenes.

    Science.gov (United States)

    Nicholas, R; Dunton, P; Tatham, A; Fielding, L

    2013-08-01

    The effects of gaseous ozone and open air factor (OAF) on environmental Listeria monocytogenes attached to three common food contact surfaces were investigated. Listeria monocytogenes on different food contact surfaces was treated with ozone and OAF. Microbiological counts, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed. Ozone at 10 ppm gave <1-log reduction when L. monocytogenes was attached to stainless steel, while 45 ppm gave a log reduction of 3.41. OAF gave better log reductions than 10 ppm ozone, but lower log reductions than 45 ppm. Significant differences were found between surfaces. Biofilm organisms were significantly more resistant than those surface attached on stainless steel. SEM and AFM demonstrated different membrane and cell surface modifications following ozone or OAF treatment. The strain used demonstrated higher resistance to ozone than previous studies. This may be due to the fact that it was isolated from a food manufacturing premises that used oxidizing disinfectants. OAF was more effective at reducing the levels of the organism than an ozone concentration of 10 ppm. Pathogen management strategies must account for resistance of environmental strains when validating cleaning and disinfection. OAF has shown potential for surface decontamination compared with ozone. SEM and AFM are valuable tools for determining mechanisms of action of antimicrobial agents. © 2013 The Society for Applied Microbiology.

  6. Enterocin CRL35 inhibits Listeria monocytogenes in a murine model.

    Science.gov (United States)

    Salvucci, Emiliano; Saavedra, Lucila; Hebert, Elvira Maria; Haro, Cecilia; Sesma, Fernando

    2012-01-01

    Listeria monocytogenes is a foodborne pathogen causative of opportunistic infections. Listeriosis is associated with severe infections in pregnant women causing abortion or neonatal listeriosis. An alternative to antibiotics are safe novel bacteriocins peptides such as enterocin CRL35 with strong antilisterial activity produced by Enterococcus mundtii CRL35. In the present paper, our goal is to study the effectiveness of this peptide and the producer strain in a murine model of pregnancy-associated listeriosis. A single dose of 5×10(9) colony-forming unit of L. monocytogenes FBUNT (Faculty of Biochemistry-University of Tucumán) resulted in translocation of pathogen to liver and spleen of BALB/c pregnant mice. The maximum level of Listeria was observed on day 3 postinfection. Interestingly, the intragastric administration of enterocin CRL35 significantly reduced the translocation of the pathogen to vital organs. On the other hand, the preadministration of E. mundtii CRL35 slightly inhibited this translocation. Listeria infection caused a significant increase in polymorphonuclear leukocytes at day 3 postinfection compared to the noninfected group. This value was reduced after the administration of enterocin CRL35. No significant changes were observed in either white blood cells or lymphocytes counts. Based on the data presented in the present work enterocin CRL35 would be a promising alternative for the prevention of Listeria infections.

  7. Listeria monocytogenes associated kerato-conjunctivitis in four horses in Norway.

    Science.gov (United States)

    Revold, Tobias; Abayneh, Takele; Brun-Hansen, Hege; Kleppe, Signe L; Ropstad, Ernst-Otto; Hellings, Robert A; Sørum, Henning

    2015-11-09

    Listeria monocytogenes has been reported to cause various infectious diseases in both humans and animals. More rarely, ocular infections have been reported. To our knowledge, only two cases of Listeria keratitis have been described in horses. We report kerato-conjunctivitis in four Norwegian horses associated with L. monocytogenes. Clinically, all cases were presented with recurrent unilateral kerato-conjunctivitis. L. monocytogenes bacteria were isolated from swab samples from all cases, and cytology carried out in 3 cases was indicative of L. monocytogenes infection. The present report describes the first known cases in which L. monocytogenes has been isolated from keratitic lesions in horses in Norway. A potential risk factor may be feeding of silage or haylage, but other sources of infection cannot be ruled out. The phenotypic features including antimicrobial susceptibility and serotype of the isolates are described. Laboratory detection of L. monocytogenes demands extra caution since only low numbers of bacteria were detected in the eye-swabs, probably due to the low volume of sample material and the intracellular niche of the bacterium. A general poor response to treatment in all these cases indicates that clinicians should pay extra attention to intensity and duration of treatment if L. monocytogenes is identified in connection with equine kerato-conjunctivitis.

  8. Recombinant probiotic expressing Listeria adhesion protein attenuates Listeria monocytogenes virulence in vitro.

    Directory of Open Access Journals (Sweden)

    Ok Kyung Koo

    Full Text Available BACKGROUND: Listeria monocytogenes, an intracellular foodborne pathogen, infects immunocompromised hosts. The primary route of transmission is through contaminated food. In the gastrointestinal tract, it traverses the epithelial barrier through intracellular or paracellular routes. Strategies to prevent L. monocytogenes entry can potentially minimize infection in high-risk populations. Listeria adhesion protein (LAP aids L. monocytogenes in crossing epithelial barriers via the paracellular route. The use of recombinant probiotic bacteria expressing LAP would aid targeted clearance of Listeria from the gut and protect high-risk populations from infection. METHODOLOGY/PRINCIPAL FINDINGS: The objective was to investigate the ability of probiotic bacteria or LAP-expressing recombinant probiotic Lactobacillus paracasei (Lbp(LAP to prevent L. monocytogenes adhesion, invasion, and transwell-based transepithelial translocation in a Caco-2 cell culture model. Several wild type probiotic bacteria showed strong adhesion to Caco-2 cells but none effectively prevented L. monocytogenes infection. Pre-exposure to Lbp(LAP for 1, 4, 15, or 24 h significantly (P<0.05 reduced adhesion, invasion, and transepithelial translocation of L. monocytogenes in Caco-2 cells, whereas pre-exposure to parental Lb. paracasei had no significant effect. Similarly, Lbp(LAP pre-exposure reduced L. monocytogenes translocation by as much as 46% after 24 h. Lbp(LAP also prevented L. monocytogenes-mediated cell damage and compromise of tight junction integrity. Furthermore, Lbp(LAP cells reduced L. monocytogenes-mediated cell cytotoxicity by 99.8% after 1 h and 79% after 24 h. CONCLUSIONS/SIGNIFICANCE: Wild type probiotic bacteria were unable to prevent L. monocytogenes infection in vitro. In contrast, Lbp(LAP blocked adhesion, invasion, and translocation of L. monocytogenes by interacting with host cell receptor Hsp60, thereby protecting cells from infection. These data show promise

  9. Prevalence and location of Listeria monocytogenes in farmed rainbow trout.

    Science.gov (United States)

    Miettinen, Hanna; Wirtanen, Gun

    2005-10-15

    A total of 510 rainbow trout originating from fish farms in lakes and sea areas around Finland were studied for the presence of Listeria monocytogenes. Samples were studied as pools from five fish. Gill, viscera, and skin from the pooled samples were analysed separately. The individual samples were analysed later if the pooled sample was found to be Listeria positive. The prevalence of Listeria spp. and L. monocytogenes in pooled unprocessed fresh rainbow trout was on average 35.0% and 14.6%, respectively. On the other hand, the prevalence of Listeria spp. and L. monocytogenes in individual thawed fish was found to be 14.3% and 8.8%, respectively. These numbers tend to overestimate and underestimate the real situation because not all fish in pooled samples were necessarily contaminated and in some of the Listeria positive pooled samples all individual samples turned out to be Listeria free. The prevalence of L. monocytogenes varied greatly between different fish farms from zero to 100% in pooled samples and from zero to 75% according to individually studied fish samples. Some indications of the influence of weather conditions and seasonal variations that strongly affected the Listeria contamination of fish were also noticed. The location of Listeria spp. and L. monocytogenes in different parts of the fish differed with statistical significance in rainbow trout. Up to 95.6% of the L. monocytogenes and 84.5% of Listeria spp. positive samples were gill samples. Only 4.4% (2/45) of the L. monocytogenes positive samples were obtained from skin or viscera. Closer study at one fish farm revealed that there was only one L. monocytogenes ribotype present in the contaminated fish, although water and surfaces were heavily contaminated with six other L. monocytogenes ribotypes.

  10. A case of bovine raw milk contamination with Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Hunt Karen

    2012-07-01

    Full Text Available Abstract During routine sampling of bulk raw milk on a dairy farm, the pathogenic bacteria Listeria monocytogenes was found to be a contaminant, at numbers L. monocytogenes, indicating a possible case of excretion of the L. monocytogenes directly into the milk. Milk samples were collected from the individual cows and analysed, resulting in the identification of L. monocytogenes excretion (at 280 cfu/ml from one of the 4 mammary quarters of one dairy cow out of 180. When the infected cow was isolated from the herd, no L. monocytogenes was detected from the remaining herd. The pulsed-field gel electrophoresis pattern of the strain from the individual cow was indistinguishable from that originally isolated from the bulk milk. The infected cow did not show any clinical signs of disease, nor did the appearance of the milk have any physical abnormalities. Antibiotic treatment of the infected mammary quarter was found to be ineffective. This study shows that there can be risks associated with direct contamination of raw milk with L. monocytogenes.

  11. Inhibition of sortase A by chalcone prevents Listeria monocytogenes infection.

    Science.gov (United States)

    Li, Hongen; Chen, Yutao; Zhang, Bing; Niu, Xiaodi; Song, Meng; Luo, Zhaoqing; Lu, Gejin; Liu, Bowen; Zhao, Xiaoran; Wang, Jianfeng; Deng, Xuming

    2016-04-15

    The critical role of sortase A in gram-positive bacterial pathogenicity makes this protein a good potential target for antimicrobial therapy. In this study, we report for the first time the crystal structure of Listeria monocytogenes sortase A and identify the active sites that mediate its transpeptidase activity. We also used a sortase A (SrtA) enzyme activity inhibition assay, simulation, and isothermal titration calorimetry analysis to discover that chalcone, an agent with little anti-L. monocytogenes activity, could significantly inhibit sortase A activity with an IC50 of 28.41 ± 5.34 μM by occupying the active site of SrtA. The addition of chalcone to a co-culture of L. monocytogenes and Caco-2 cells significantly inhibited bacterial entry into the cells and L. monocytogenes-mediated cytotoxicity. Additionally, chalcone treatment decreased the mortality of infected mice, the bacterial burden in target organs, and the pathological damage to L. monocytogenes-infected mice. In conclusion, these findings suggest that chalcone is a promising candidate for the development of treatment against L. monocytogenes infection. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Resistance of Listeria monocytogenes biofilms to sanitizing agents

    Science.gov (United States)

    Listeria monocytogenes is notorious for its capacity to colonize the environment and equipment of food processing facilities and to persist in the processing plant ecosystem, sometimes for decades. Such persistence is mediated by multiple attributes of L. monocytogenes, including the pathogen’s capa...

  13. Relationship between Listeria monocytogenes and Listeria spp. in seafood processing plants.

    Science.gov (United States)

    Alali, Walid Q; Schaffner, Donald W

    2013-07-01

    The objective of this study was to evaluate the relationship between prevalence of Listeria monocytogenes as an outcome and Listeria spp. as an explanatory variable by food products, food contact surfaces, and nonfood contact surfaces in seafood processing plants by using peer-reviewed published data. Nine sets of prevalence data of L. monocytogenes and Listeria spp. were collected from published studies and used for the analyses. Based on our analysis, the relationship between L. monocytogenes prevalence and Listeria spp. prevalence in food products (incoming raw materials and finish products) was significant (P = 0.04) with (low) R² = 0.36. Furthermore, Listeria spp. were not a good indicator for L. monocytogenes when testing food contact surfaces (R² = 0.10). Listeria spp. were a good indicator for L. monocytogenes only on nonfood contact surfaces (R² = 0.90). On the other hand, the presence of Listeria spp. on food contact surfaces (R² = 0.002) and nonfood contact surfaces (R² = 0.03) was not a good indicator for L. monocytogenes presence in food products. In general, prevalence of Listeria spp. does not seem to be a good indicator for L. monocytogenes prevalence in seafood processing plants.

  14. LISTERIA MONOCYTOGENES RISK EVALUATION IN READY TO EAT DELI PRODUCTS

    Directory of Open Access Journals (Sweden)

    T Civera

    2013-02-01

    Full Text Available Listeria monocytogenes has become one of the major concerns for food safety. Its ability to survive and replicate at low temperature, pH and high salt concentration, makes the bacterium a threat, mostly for RTE products. For these reasons, the present research was aimed at detecting the ability of growth of L. monocytogenes in RTE products retrieved from one deli store. Samples were analysed for L. monocytogenes detection, then inoculated with the pathogen (105cell/ml and stored at refrigeration temperature for the duration of their shelf-life (15-60 days. In all the products L. monocytogenes was not detected before experimental contamination. The challenge test evidenced that experimentally inoculated L. monocytogenes was not able to multiply for the duration of the entire shelf-life. These results indicated that the tested products could be considered as foods which are not able to support the growth of L. monocytogenes, as indicated by E.C. Regulation 2073/05. However, in order to guarantee consumer’s safety, it needs to be emphasized the need of a correct application of the GMPs, required for lowering the risk of initial contamination.

  15. Internalization of Listeria monocytogenes in cantaloupes during dump tank washing and hydrocooling.

    Science.gov (United States)

    Macarisin, Dumitru; Wooten, Anna; De Jesus, Antonio; Hur, Minji; Bae, Seonjae; Patel, Jitendra; Evans, Peter; Brown, Eric; Hammack, Thomas; Chen, Yi

    2017-09-18

    Recent listeriosis outbreaks and recalls associated with cantaloupes urge for studies to understand the mechanisms of cantaloupe contamination by Listeria monocytogenes. Postharvest practices such as washing and hydrocooling were suggested to facilitate the contamination of fresh fruits by human pathogens. This study assessed the potential of L. monocytogenes internalization into cantaloupes during dump tank washing and immersion-type hydrocooling in water contaminated with L. monocytogenes. The effect of cantaloupe cultivar, water temperature, and harvesting technique on L. monocytogenes internalization was also evaluated. Full slip (cantaloupe without any residual stem) Western and Eastern cultivar cantaloupes were pre-warmed to 42°C (to imitate peak-high field temperatures of freshly harvested cantaloupes) and then immersed in water at 6°C and 18°C containing 4 and 6logCFU/ml of L. monocytogenes. Clipped (cantaloupe with short stem residues obtained by clipping the stem at harvest) Western and Eastern cantaloupes were pre-warmed to 42°C and then immersed in water at 6°C containing 6logCFU/ml of L. monocytogenes. Additionally, full slip and clipped Western cantaloupes were equilibrated to 18°C and then immersed in water at 18°C containing 6logCFU/ml of L. monocytogenes (isothermal immersion without temperature differential). Water containing L. monocytogenes infiltrated both full slip and clipped cantaloupes through the stems/stem scars and was then distributed along the vascular system in hypodermal mesocarp reaching the calyx area of the fruit. The current study demonstrated that, under experimental conditions, L. monocytogenes can internalize into cantaloupes during immersion in water contaminated by L. monocytogenes, both in the presence and absence of temperature differential, and that temperature differential moderately enhanced the internalization of L. monocytogenes. The incidence and levels of L. monocytogenes internalized in the middle

  16. Listeria monocytogenes growth limits and stress resistance mechanisms

    NARCIS (Netherlands)

    Veen, van der S.

    2008-01-01

    The food-borne pathogen Listeria monocytogenes is a Gram-positive facultative anaerobic rod, which is the causative agent of listeriosis. Due to the severity of the disease and the fact that its incidence is increasing in numerous European countries, L. monocytogenes is of great public health

  17. Listeria monocytogenes in poultry and poultry products: Epidemiological investigations in seven Danish abattoirs

    DEFF Research Database (Denmark)

    Ojeniyi, B.; Wegener, Henrik Caspar; Jensen, N.E.

    1996-01-01

    Listeria monocytogenes was isolated from 11/236 (4 . 7%) caecal samples from parent flocks, providing broilers to the abattoirs investigated. Caecal samples from 2078 broilers representing 90 randomly selected broiler flocks were negative for L. monocytogenes. A total of 3080 samples from seven...... abattoirs including poultry processing line samples, and final products were also examined for L. monocytogenes. Listeria monocytogenes was isolated in 0 . 3% to 18 . 7% of the samples collected in the different abattoirs. Epidemiological typing of 247 L. monocytogenes isolates, including serotyping, phage...... isolates of L. monocytogenes since only 120/247 (48 . 6%) isolates were typable by phage typing and 230/247 (93 . 1%) L. monocytogenes belonged to serotype 01 while 6/247 (2 . 4%) belonged to 04. The discovery of a few dominating clones in each abattoir might indicate an endemic occurrence of L...

  18. Aerosol studies with Listeria innocua and Listeria monocytogenes.

    Science.gov (United States)

    Zhang, Guodong; Ma, Li; Oyarzabal, Omar A; Doyle, Michael P

    2007-08-01

    Aerosol studies of Listeria monocytogenes in food processing plants have been limited by lack of a suitable surrogate microorganism. The objective of this study was to investigate the potential of using green fluorescent protein-labeled strains of Listeria innocua as a surrogate for L. monocytogenes for aerosol studies. These studies were conducted in a laboratory bioaerosol chamber and a pilot food-processing facility. Four strains of L. innocua and five strains of L. monocytogenes were used. In the laboratory chamber study, Listeria cells were released into the environment at two different cell numbers and under two airflow conditions. Trypticase soy agar (TSA) plates and oven-roasted breasts of chicken and turkey were placed in the chamber to monitor Listeria cell numbers deposited from aerosols. A similar experimental design was used in the pilot plant study; however, only L. innocua was used. Results showed that L. monocytogenes and L. innocua survived equally well on chicken and turkey breast meats and TSA plates. No-fan and continuous fan applications, which affected airflow, had no significant effect on settling rates of aerosolized L. monocytogenes and L. innocua in the bioaerosol chamber or L. innocua in the pilot plant study. Listeriae cell numbers in the air decreased rapidly during the first 1.5 h following release, with few to no listeriae detected in the air at 3 h. Aerosol particles with diameters of 1 and 2 microM correlated directly with the number of Listeria cells in the aerosol but not with particles that were 0.3, 0.5, and 5 microM in diameter. Results indicate that L. innocua can be used as a surrogate for L. monocytogenes in an aerosol study.

  19. Potential of chitosan from Mucor rouxxi UCP064 as alternative natural compound to inhibit Listeria monocytogenes Potencial de quitosana de Mucor rouxxi UCP 064 como componente alternativo para inibir Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Roberta A. Bento

    2009-09-01

    Full Text Available Listeria monocytogenes is widely distributed in nature and the infection listeriosis is recognized as a potential threat for human health because of its mortality rate. The objective of this study was to evaluate the growth profile and chitosan production by Mucor rouxxi UCP 064 grown in yam bean (Pachyrhizus erosus L. Urban medium. It was also to assess the anti-L. monocytogenes efficacy of the obtained chitosan. Higher values of biomass of M. rouxxi (16.9 g.L¹ and best yield of chitosan (62 mg.g-1 were found after 48 h of cultivation. Residual glucose and nitrogen in the growth media were 4.1 and 0.02 g.L¹ after 96 h, respectively. Obtained chitosan presented 85 % of degree of deacetylation and 2.60 x 10(4 g.mol-1of viscosimetric molecular weight. Minimum Inhibitory Concentration (MIC and Minimum Bactericidal Concentration (MBC values of chitosan against L. monocytogenes ATCC 7644 were, respectively, 2.5 and 5.0 mg.mL-1. At 2.5 and 5.0 mg.mL-1 chitosan caused cidal effect in a maximum time of 4 h. Bacterial count below 2 log cfu.mL-1were found from 2 h onwards and no recovery in bacterial growth was noted in the remainder period. These results show the biotechnological potential of yam bean medium for chitosan production by Mucor rouxxi and support the possible rational use of chitosan from fungi as natural antimicrobial to control L. monocytogenes.Listeria monocytogenes apresentase como um microrganismo amplamente distribuído na natureza, sendo que a infecção listeriose é reconhecida como uma potencial ameaça a saúde humana devido a sua taxa de mortalidade. O objetivo deste estudo foi avaliar o perfil de crescimento e de produção de quitosana por Mucor rouxxi UCP 064 cultivado em meio jacatupé (Pachyrhizus erosus L. Urban, bem como avaliar a eficácia anti-L. monocytogenes da quitosana produzida com vistas a uma possível aplicação em alimentos. Os mais elevados valores de biomassa de M. rouxxi (16,9 g.L¹ e o maior rendimento na

  20. Low prevalence of Listeria monocytogenes in cull sows and pork.

    Science.gov (United States)

    Wesley, Irene V; Larsen, Steven; Hurd, H Scott; McKean, James D; Griffith, Ronald; Rivera, Fernando; Nannapaneni, Ramakrishna; Cox, Mandy; Johnson, Michael; Wagner, Dean; de Martino, Mary

    2008-03-01

    The goal of this study was to determine the prevalence of Listeria monocytogenes in sows slaughtered at a single Midwestern plant on two occasions (trial 1, n = 179 sows; trial 2, n = 160 sows). Fecal samples collected antemortem (trial 1) as well as animal tissues, and carcass swabs collected at the abattoir (trials 1 and 2) were analyzed. Eight isolates of L. monocytogenes were recovered from five samples that represented 0.18% of the total samples (n = 2,775). In trial 1, L. monocytogenes was detected in a tonsil sample (0.6%; 1 positive of 181 tonsils), in a carcass (0.6%; 1 positive of 179 carcasses), which was sampled prior to the organic rinse, and in two chopped meat block samples (1.2%; 2 positive of 165 samples). In trial 2, L. monocytogenes was only detected in a single chopped meat block sample (0.15%; 1 positive of 688 total samples). These data indicate the low prevalence of L. monocytogenes in the cull sow.

  1. Antimicrobial resistance of Listeria monocytogenes isolated from dairy-based food products.

    Science.gov (United States)

    Harakeh, Steve; Saleh, Imane; Zouhairi, Omar; Baydoun, Elias; Barbour, Elie; Alwan, Nisreen

    2009-06-15

    In this study Listeria monocytogenes (L. monocytogenes) was isolated from three traditionally consumed Lebanese dairy-based food products. One hundred and sixty four samples (45 samples of Baladi cheese, 36 samples of Shankleesh and 83 of Kishk) were collected from the Bekaa Valley in the Northeast region of Lebanon. Suspected Listeria colonies were selected and initially identified by using standard biochemical tests. Initial identification of the positive L. monocytogenes colonies was confirmed at the molecular level by Polymerase Chain Reaction (n=30) and the confirmed isolates were evaluated for their susceptibility to 10 commonly used antimicrobials. All of the 30 isolates were confirmed to be L. monocytogenes yielding a PCR product of approximately 660 base pairs (bp). L. monocytogenes was detected in 26.67%, 13.89% and 7.23% of the Baladi cheese, Shankleesh and Kishk samples, respectively. The highest resistance in L. monocytogenes isolates was noted against oxacillin (93.33%) followed by penicillin (90%). The results provide an indication of the contamination levels of dairy-based foods in Lebanon and highlight the emergence of multi-drug resistant Listeria in the environment.

  2. Behaviour of Listeria monocytogenes in packaged fresh mushrooms (Agaricus bisporus).

    Science.gov (United States)

    González-Fandos, E; Olarte, C; Giménez, M; Sanz, S; Simón, A

    2001-11-01

    The aim of this study was to evaluate the potential of Listeria monocytogenes to grow in mushrooms packaged in two different types of PVC films when stored at 4 degrees C and 10 degrees C. Mushrooms were packed in two polymeric films (perforated and nonperforated PVC) and stored at 4 degrees C and 10 degrees C. The carbon dioxide and oxygen content inside the packages, aerobic mesophiles, psychrotrophs, Pseudomonas spp., Listeria monocytogenes, faecal coliforms, Escherichia coli, anaerobic spores and major sensory factors were determined. The mushrooms packaged in nonperforated film and stored at 4 degrees C had the most desirable quality parameters (texture, development stage and absence of moulds). Listeria monocytogenes was able to grow at 4 degrees C and 10 degrees C in inoculated mushrooms packaged in perforated and nonperforated films between 1 and 2 log units during the first 48 h. After 10 d of storage, the populations of L. monocytogenes were higher in mushrooms packaged in nonperforated film and stored at 10 degrees C. MAP followed by storage at 4 degrees C or 10 degrees C extends the shelf life by maintaining an acceptable appearance, but allows the growth and survival of L. monocytogenes. According to this study additional hurdles must be studied in order to prevent the growth of L. monocytogenes.

  3. Listeria monocytogenes Circulating in Rabbit Meat Products and Slaughterhouses in Italy: Prevalence Data and Comparison Among Typing Results.

    Science.gov (United States)

    De Cesare, Alessandra; Parisi, Antonio; Mioni, Renzo; Comin, Damiano; Lucchi, Alex; Manfreda, Gerardo

    2017-03-01

    Rabbit meat has outstanding dietetic and nutritional properties. However, few data on microbiological hazards associated with rabbit productions are available. In this study, the presence of Listeria monocytogenes was determined in 430 rabbit carcasses, 256 rabbit meat cuts and products, and 599 environmental sponges collected from four Italian rabbit slaughterhouses over a period of 1 year. Prevalence of L. monocytogenes among the 1285 rabbit meat and environmental samples was 11%, with statistically significant differences between slaughterhouses. The highest prevalence (33.6%) was observed in rabbit meat cuts and products; the majority of positive environmental samples were collected from conveyor belts. Overall, 27.9% and 14.3% of rabbit cuts and carcasses, respectively, had L. monocytogenes counts higher than 1 colony-forming unit (CFU)/10 g. A selection of 123 isolates from positive samples was genotyped and serotyped to determine genetic profiles and diversity among L. monocytogenes isolates contaminating different slaughterhouses and classes of products investigated. Discriminatory power and concordance among the results obtained using multilocus variable-number tandem-repeat analysis (MLVA), multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), automated EcoRI ribotyping, and serotyping were assessed. The isolates selected for typing were classified into serotypes 1/2a (52.8%), 1/2c (32.5%), and 1/2b (14.6%). The majority of the isolates were classified as ST14 (34.1%), ST9 (35.5%), ST121 (17.9%), and ST224 (14.6%). The greatest discriminatory power was observed with the MLVA typing, followed by MLST, PFGE, and ribotyping. The best bidirectional concordance was achieved between PFGE and MLST. There was 100% correlation between both MLST and MLVA with serotype. Moreover, a high unidirectional correspondence was observed between MLVA and both MLST and PFGE, as well as between PFGE and both MLST and serotyping. The results of this

  4. Prevalence and characteristics of Listeria monocytogenes in bovine colostrum in Japan.

    Science.gov (United States)

    Hasegawa, Megumi; Iwabuchi, Eriko; Yamamoto, Shiori; Esaki, Hidetake; Kobayashi, Kazuhiko; Ito, Masahiko; Hirai, Katsuya

    2013-02-01

    This study was conducted to determine the prevalence and characteristics of Listeria monocytogenes in bovine colostrum in Japan. We collected bovine colostrum samples from 210 dams from 21 dairy farms in Hokkaido prefecture (Japan) between March and June 2009. L. monocytogenes was detected in samples from 6 (28.6%) of the 21 farms. Of the 210 samples, 16 (7.6%) were positive for L. monocytogenes. We recovered 80 L. monocytogenes isolates; 44 (55%) isolates were classified as serotype 1/2b and 36 (45%) were classified as serotype 4b. The isolates were susceptible to penicillin, ampicillin, amoxicillin, gentamicin, kanamycin, streptomycin, erythromycin, vancomycin, tetracycline, chloramphenicol, ciprofloxacin, and trimethoprim-sulfamethoxazole. Pulsed-field gel electrophoresis (PFGE) characterization of the 80 isolates revealed six PFGE types. Two PFGE types corresponded to human listeriosis cases. Most L. monocytogenes isolates possessed virulence-associated genes (actA, hly, iap, inlA, inlC, mpl, plcA, plcB, opuCA, prfA, and clpC). One PFGE type isolate possessed an epidemic clone II marker. Our findings suggest that isolates from bovine colostrum have the potential to cause human and animal listeriosis. This is the first study on the prevalence and characteristics of L. monocytogenes isolated from bovine colostrum obtained from dairy farms. Our results have important implications for improving public health and elucidating the epidemiology of L. monocytogenes in bovine colostrum.

  5. Prevalence of Listeria monocytogenes in poultry meat

    Directory of Open Access Journals (Sweden)

    Mehmet ELMALI

    2015-01-01

    Full Text Available AbstractThe objectives of this study were i to isolate Listeria spp. and Listeria monocytogenes in broiler wing meat samples, ii to confirm the isolates by PCR, based on prs and hly A gene sequences, iii to determine the seasonal and monthly distribution of the isolates. A total of 120 broiler wing meat samples (60 packaged pieces wrapped using strech film in styrofoam plates and 60 unpackaged pieces bought from different markets in Hatay province were analysed. Listeria spp. was isolated from 57 (47.5% out of 120 samples. Fifty-four, out of 57 Listeria spp. isolates were identified as L. monocytogenes. L. monocytogenes was isolated from the samples collected during the spring, winter, summer, and autumn at the levels of 26.6%, 40%, 53.3%, 60%, respectively. In this study, the isolation rates were found to be the highest in autumn, while the isolation rates were found to be the lowest in spring. As a consequence, high prevalence of Listeria spp. and L. monocytogenes in poultry wing meat samples may pose a risk for human health. We consider that with obeying the rules of good hygiene practices (GHP, good manufacturing practices (GMP and HACCP can minimize the contamination with Listeria spp.

  6. Biocontrole de Listeria monocytogenes por Pediococcus acidilactici em couve minimamente processada Biocontrol of Listeria monocytogenes by Pediococcus acidilactici in fresh-cut kale

    Directory of Open Access Journals (Sweden)

    Wanessa Altimiras Costa

    2009-12-01

    Full Text Available Este estudo avaliou um sistema de biocontrole para inibição de Listeria monocytogenes em couve minimamente processada, objetivando sua segurança durante estocagem sob refrigeração e em condições de abuso de temperatura. O potencial inibitório de bactérias láticas tolerantes ao sal e psicrotróficas contaminantes naturais da couve e Lactobacillus plantarum, Lactobacillus delbrueckii ATCC 9649 e Lactobacillus casei CCT 1465 foram avaliadas contra L. monocytogenes. O isolado de couve identificado como P. acidilactici CCA3 inibiu L. monocytogenes a 10 e 15 °C em ágar MRS e foi selecionado como possível agente de biocontrole. O número de L. monocytogenes na couve minimamente processada aumentou 3,7 e 4,7 ciclos logarítmicos a 5 e 10 °C, respectivamente, após 20 dias de armazenamento e 4,6 ciclos logarítmicos após oito dias a 15 °C. Entretanto, quando 10(8 UFC.g-1 de P. acidilactici CCA3 foram inoculados no produto processado, o crescimento de L. monocytogenes reduziu 2,3 ciclos logarítmicos sob temperatura abusiva de 15 °C. A acidez titulável e as características sensoriais da couve não foram alteradas pela presença de CCA3 ao longo do período de vida útil. Estes resultados sugerem o potencial de aplicação dos bioconservantes na couve minimamente processada, que necessitam estar associados à refrigeração e sanitização para garantir segurança.This study evaluated a biological control system for the inhibition of Listeria monocytogenes in minimally processed kale focusing on its freshness under refrigeration and extreme temperatures. The inhibitory potential of salt and cold tolerant lactic bacteria from natural microflora of kale, Lactobacillus delbrueckii ATCC 9649, Lactobacillus plantarum, and Lactobacillus casei CCT 1465 strains were evaluated against L. monocytogenes. Pediococcus acidilactici CCA3 isolated from kale exhibited a large inhibition zone of L. monocytogenes at 10 and 15 °C in MRS agar and was

  7. Assessment of the microbial parameters along the production phases at a dairy plant

    Directory of Open Access Journals (Sweden)

    Angelovski Ljupco

    2012-01-01

    Full Text Available The main objective of this paper was to detect the prevalence of pathogenic bacteria (Listeria monocytogenes, Campylobacter spp., Salmonella spp., Staphylococcus aureus and Escherichia coli in raw milk, to assess the hygiene parameters during the milk processing and to evaluate the safety of the fi nal dairy products using standard ISO methods. Staphylococcus aureus showed highest prevalence of the pathogen microorganisms (85%, followed by Escherichia coli (46% and Listeria monocytogenes (9.8 in bulk tank milk samples. Campylobacter spp. and Salmonella spp. were not detected in any of the tested samples.The swab samples taken from employees and working surfaces, water samples and pasteurized milk samples detected inadequate sanitary procedures during the phase of milk processing. Analysis of the swabs from employees hands revealed 1 positive sample for enumeration for Enterobacteriaceae and 7 samples with higher total viable count that did not comply withthe legislative, while the analysis of the swabs from working surfaces detected 5 samples positive for Enterobacteriaceae and 4 samples with higher total viable count that did not comply with the same legislative. The analysis of the water samples detected 2 samples with higher total viable count on 22°C, 2 samples for total viable count on 37°C and 1 sample for coliform bacteria that did not comply with the national legislative. None of the samples showed presence of Pseudomonas aeruginosa, Escherichia coli, sulphite reducing clostridia and intestinal enterococci. The analysis ofthe pasteurized milk confi rmed 3 samples with presence of Enterobacteriacae, 1 sample for coagulase-positive staphylococci and 2 samples with high total viable count at 30°C that did not comply with the national legislative. The analysis of fermented milk products and cheese samples confirmed the need for immediate corective measures and subsequently, improved sanitation procedures. The testing detected 9 samples of

  8. Listeria monocytogenes in retailed raw chicken meat in Turkey.

    Science.gov (United States)

    Siriken, Belgin; Ayaz, Naim Deniz; Erol, Irfan

    2014-01-01

    The objectives of this study were, to find the prevalence and antimicrobial resistance of L. monocytogenes from a total of 116 chicken meat samples including 50 carcasses and 66 meat parts marketed in Turkey between 2008 and 2009 using immunomagnetic separation (IMS) based cultivation technique, to detect the hlyA gene for the verification of the isolates by PCR, and to identify the genoserotypes of the L. monocytogenes isolates by multiplex PCR assay. In the study, 51 L. monocytogenes colonies were isolated from 34 (29.3%) chicken meat samples (eleven [22.0%] carcasses and 23 [34.8%] pieces of meat) by IMS based cultivation technique and confirmed by PCR. According to the multiplex PCR results, all the 51 isolates were identified as genoserotype IIa (1/2a or 3a). L. monocytogenes isolates were also tested for their susceptibility to eight antibiotic (gentamicin, vancomycin, chloramphenicol, streptomycin, tetracycline, ampicillin, penicillin G, erythromycin) agents using the disk diffusion method. 14 isolates (27.45%) were susceptible to all eight antimicrobials drugs tested and the remaining 37 isolates (72.54%) were resistant to gentamicin (one isolate, 1.96%), vancomycin (four isolates, 7.84%), penicillin G (six isolates, 11.76%), streptomycin (nine isolates, 17.64%; resistant or intermediate), tetracycline (seven isolates, 13.72%) and ampicillin (six isolates, 11.76%). This study showed that antimicrobial resistance is not highly prevalent in L. monocytogenes isolated from chicken carcasses and pieces of meat. The presence of L. monocytogenes in chicken samples suggests an importance of this pathogen in chicken.

  9. Listeria monocytogenes in Fresh Produce: Outbreaks, Prevalence and Contamination Levels

    Directory of Open Access Journals (Sweden)

    Qi Zhu

    2017-03-01

    Full Text Available Listeria monocytogenes, a member of the genus Listeria, is widely distributed in agricultural environments, such as soil, manure and water. This organism is a recognized foodborne pathogenic bacterium that causes many diseases, from mild gastroenteritis to severe blood and/or central nervous system infections, as well as abortion in pregnant women. Generally, processed ready-to-eat and cold-stored meat and dairy products are considered high-risk foods for L. monocytogenes infections that cause human illness (listeriosis. However, recently, several listeriosis outbreaks have been linked to fresh produce contamination around the world. Additionally, many studies have detected L. monocytogenes in fresh produce samples and even in some minimally processed vegetables. Thus L. monocytogenes may contaminate fresh produce if present in the growing environment (soil and water. Prevention of biofilm formation is an important control measure to reduce the prevalence and survival of L. monocytogenes in growing environments and on fresh produce. This article specifically focuses on fresh produce–associated listeriosis outbreaks, prevalence in growing environments, contamination levels of fresh produce, and associated fresh produce safety challenges.

  10. Commensal microbes provide first line defense against Listeria monocytogenes infection

    Science.gov (United States)

    Littmann, Eric R.; Kim, Sohn G.; Morjaria, Sejal M.; Ling, Lilan; Gyaltshen, Yangtsho; Taur, Ying; Leiner, Ingrid M.

    2017-01-01

    Listeria monocytogenes is a foodborne pathogen that causes septicemia, meningitis and chorioamnionitis and is associated with high mortality. Immunocompetent humans and animals, however, can tolerate high doses of L. monocytogenes without developing systemic disease. The intestinal microbiota provides colonization resistance against many orally acquired pathogens, and antibiotic-mediated depletion of the microbiota reduces host resistance to infection. Here we show that a diverse microbiota markedly reduces Listeria monocytogenes colonization of the gut lumen and prevents systemic dissemination. Antibiotic administration to mice before low dose oral inoculation increases L. monocytogenes growth in the intestine. In immunodeficient or chemotherapy-treated mice, the intestinal microbiota provides nonredundant defense against lethal, disseminated infection. We have assembled a consortium of commensal bacteria belonging to the Clostridiales order, which exerts in vitro antilisterial activity and confers in vivo resistance upon transfer into germ free mice. Thus, we demonstrate a defensive role of the gut microbiota against Listeria monocytogenes infection and identify intestinal commensal species that, by enhancing resistance against this pathogen, represent potential probiotics. PMID:28588016

  11. Meningoencefalite por Listeria monocytogenes em ovinos Meningoencephalitis in sheep caused by Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Daniel R. Rissi

    2010-01-01

    Full Text Available São descritos sete casos de doença neurológica em ovinos por Listeria monocytogenes no Rio Grande do Sul e Paraná entre 2000 e 2007. Foram afetados ovinos com idades entre 12-24 meses. Os casos ocorreram no verão e início da primavera e os índices gerais de morbidade e letalidade foram de 3,15% e 100%, respectivamente. Quando essa informação estava disponível, nenhum dos ovinos afetados era alimentado com silagem. Em três propriedades havia contato próximo dos ovinos afetados com outras espécies. A evolução do quadro clínico foi de 12 horas a três dias e os sinais clínicos foram caracterizados por decúbito (7/7, desvio da cabeça (4/7, incoordenação (3/7, depressão (3/7, andar em círculos (2/7, cegueira unilateral, emagrecimento progressivo, febre, midríase, movimentos de pedalagem, nistagmo lateral, opistótono, paralisia flácida dos membros pélvicos ou dos quatro membros, salivação excessiva e tremores (1/7 cada. Histologicamente observou-se encefalite com microabscessos, predominantemente unilateral com variáveis graus de gliose e alterações degenerativas como esferóides axonais e infiltração de células Gitter. As lesões se estendiam desde a medula oblonga até o mesencéfalo. Antígenos de Listeria monocytogenes foram detectados por imuno-histoquímica em seções de tronco encefálico de todos os ovinos afetados. O diagnóstico foi realizado com base nos achados epidemiológicos e clinico-patológicos, e confirmado pela imuno-histoquímica (IHQ utilizando anticorpo policlonal anti-L. monocytogenes.Seven cases of neurological disease in sheep caused by Listeria monocytogenes in Rio Grande do Sul and Paraná state, southern Brazil are described. The cases occurred between 2000 and 2007 and 12-24-month-old sheep were affected. Overall morbidity and lethality rates were 3.15% and 100%, respectively. Cases occurred in the summer and early spring. When this information was available, affected sheep had not been

  12. Listeria monocytogenes infection of HD11, chicken macrophage-like cells.

    Science.gov (United States)

    Jarvis, N A; Donaldson, J R; O'Bryan, C A; Ricke, S C; Crandall, P G

    2017-04-01

    Listeria monocytogenes can be carried by and infect poultry, although the clinical disease in birds is rare. Escape from macrophage phagocytosis is a key step in pathogenesis for L. monocytogenes. Therefore, we investigated the infection of the chicken macrophage-like cell line HD11 with 2 strains of L. monocytogenes EGD-e and Scott A. After infection, L. monocytogenes was quantified by spread plating and HD11 was quantified with trypan blue exclusion stain before enumeration. The standard macrophage killing protocols require washing the cell monolayers 3 times with PBS, which was found to negatively influence HD11 monolayers. Maximum bacterial densities within macrophages were not different between the 2 Listeria strains. HD11 required more than 11 h to effectively reduce intracellular L. monocytogenes Scott A, and Scott A was more susceptible to HD11 killing than EGD-e. It appears that Listeria infection initially causes attenuation of HD11 growth, and infected HD11 cells do not begin to lyse until at least 11 h post infection. These results suggest that there are subtle strain to strain differences in response to HD11 macrophage phagocytosis. The long lead-time required for HD11 to kill L. monocytogenes cells means that there is sufficient time available for chicken macrophages to circulate in the blood and transfer the intracellular Listeria to multiple tissues. © 2016 Poultry Science Association Inc.

  13. Survival of Bactericidal Antibiotic Treatment by a Persister Subpopulation of Listeria monocytogenes

    DEFF Research Database (Denmark)

    Knudsen, Gitte Maegaard; Ng, Yin; Gram, Lone

    2013-01-01

    Listeria monocytogenes can cause the serious infection listeriosis, which despite antibiotic treatment has a high mortality. Understanding the response of L. monocytogenes to antibiotic exposure is therefore important to ensure treatment success. Some bacteria survive antibiotic treatment...... by formation of persisters, which are a dormant antibiotic-tolerant subpopulation. The purpose of this study was to determine whether L. monocytogenes can form persisters and how bacterial physiology affects the number of persisters in the population. A stationary-phase culture of L. monocytogenes was adjusted...... that eradication of persisters is possible. Our study adds L. monocytogenes to the list of bacterial species capable of surviving bactericidal antibiotics in a dormant stage, and this persister phenomenon should be borne in mind when developing treatment regimens....

  14. Persistence and potential Viable but Non-culturable state of pathogenic bacteria during storage of digestates from agricultural biogas plants

    Directory of Open Access Journals (Sweden)

    Geraldine Maynaud

    2016-09-01

    Full Text Available Despite the development of on-farm anaerobic digestion as a process for making profitable use of animal by-products, factors leading to the inactivation of pathogenic bacteria during storage of digestates remain poorly described. Here, a microcosm approach was used to evaluate the persistence of three pathogenic bacteria (Salmonella enterica Derby, Campylobacter coli and Listeria monocytogenes in digestates from farms, stored for later land spreading. Nine samples, including raw digestates, liquid fractions of digestate and composted digestates, were inoculated with each pathogen and maintained for 40 days at 24°C. Concentrations of pathogens were monitored using culture and qPCR methods. The persistence of L. monocytogenes, detected up to 20 days after inoculation, was higher than that of Salmonella Derby, detected for 7-20 days, and of C. coli (not detected after 7 days. In some digestates, the concentration of the pathogens by qPCR assay was several orders of magnitude higher than the concentration of culturable cells, suggesting a potential loss of culturability and induction of Viable but Non-Culturable (VBNC state. The potential VBNC state which was generally not observed in the same digestate for the three pathogens, occurred more frequently for C. coli and L. monocytogenes than for Salmonella Derby. Composting a digestate reduced the persistence of seeded L. monocytogenes but promoted the maintenance of Salmonella Derby. The effect of NH4+/NH3 on the culturability of C. coli and Salmonella Derby was also shown.The loss of culturability may be the underlying mechanism for the regrowth of pathogens. We have also demonstrated the importance of using molecular tools to monitor pathogens in environmental samples since culture methods may underestimate cell concentration. Our results underline the importance of considering VBNC cells when evaluating the sanitary effect of an anaerobic digestion process and the persistence of pathogens during

  15. Detection of Listeria Spp. and Listeria monocytogenes in vegetables ...

    African Journals Online (AJOL)

    This paper aimed to study the prevalence and antibiotic resistance pattern among Listeria monocytogenes in raw vegetables sourced from commercial farms and local farms in Terengganu. Thirteen types of vegetables investigated for the presence of L. monocytogenes using multiplex PCR and LAMP methods. Isolation of ...

  16. Inhibition of Listeria monocytogenes ATCC 19115 on ham steak by tea bioactive compounds incorporated into chitosan-coated plastic films

    Directory of Open Access Journals (Sweden)

    Vodnar Dan C

    2012-07-01

    Full Text Available Abstract Background The consumer demands for better quality and safety of food products have given rise to the development and implementation of edible films. The use of antimicrobial films can be a promising tool for controlling L. monocytogenes on ready to eat products. The aim of this study was to develop effective antimicrobial films incorporating bioactive compounds from green and black teas into chitosan, for controlling L. monocytogenes ATCC 19115 on vacuum-packaged ham steak. The effectiveness of these antimicrobial films was evaluated at room temperature (20°C for 10 days and at refrigerated temperature (4°C for 8 weeks. Results The HPLC results clearly show that relative concentrations of catechins and caffeine in green tea ranked EGCG>EGC>CAF>ECG>EC>C while in black tea extracts ranked CAF>EGCG>ECG>EGC>EC>C. The chitosan-coated plastic films incorporating green tea and black tea extracts shows specific markers identified by FTIR. Incorporating natural extracts into chitosan showed that the growth of L monocytogenes ATCC 19115 was inhibited. The efficacy of antimicrobial effect of tea extracts incorporated into chitosan-coated plastic film was dose dependent. However, chitosan-coated films without addition of tea extracts did not inhibit the growth of L. monocytogenes ATCC 19115. Chitosan-coated plastic films incorporating 4% Green tea extract was the most effective antimicrobial, reducing the initial counts from 3.2 to 2.65 log CFU/cm2 during room temperature storage and from 3.2 to 1–1.5 log CFU/cm2 during refrigerated storage. Conclusions Incorporation of tea extracts into the chitosan-coated films considerably enhanced their effectiveness against L. monocytogenes ATCC 19115. 4% Green tea incorporated into chitosan-coated plastic film had a better antilisterial effect than 2% green tea or 2% and 4% black tea. Data from this study would provide new formulation options for developing antimicrobial packaging films using tea

  17. Early trigeminal nerve involvement in Listeria monocytogenes rhombencephalitis

    DEFF Research Database (Denmark)

    Karlsson, William K; Harboe, Zitta Barrella; Roed, Casper

    2017-01-01

    dysfunction on that side. In addition, we identified another 120 cases of Listeria rhombencephalitis following a systematic review. Cranial nerves VII, V, IX, and X, respectively, medulla oblongata, cerebellum and pons, were the most frequently involved brain structures. The present clinical and radiological...... findings corroborate earlier data from animal experiments, indicating that L. monocytogenes may be capable of retrograde intra-axonal migration along the cranial nerves. We suggest that in a subset of patients with rhombencephalitis L. monocytogenes enters the cerebellopontine angle through the trigeminal......Listeria monocytogenes is associated with rhombencephalitis. However, the exact mechanisms of brainstem invasion remains poorly understood. Here, we demonstrate clinical and radiological data suggesting that Listeria may invade the brainstem via the trigeminal nerve. Three females (41, 64 and 70...

  18. Morphological Change and Decreasing Transfer Rate of Biofilm-Featured Listeria monocytogenes EGDe.

    Science.gov (United States)

    Lee, Yuejia; Wang, Chinling

    2017-03-01

    Listeria monocytogenes , a lethal foodborne pathogen, has the ability to resist the hostile food processing environment and thus frequently contaminates ready-to-eat foods during processing. It is commonly accepted that the tendency of L. monocytogenes ' to generate biofilms on various surfaces enhances its resistance to the harshness of the food processing environment. However, the role of biofilm formation in the transferability of L. monocytogenes EGDe remains controversial. We examined the growth of Listeria biofilms on stainless steel surfaces and their effect on the transferability of L. monocytogenes EGDe. The experiments were a factorial 2 × 2 design with at least three biological replicates. Through scanning electron microscopy, a mature biofilm with intensive aggregates of cells was observed on the surface of stainless steel after 3 or 5 days of incubation, depending on the initial level of inoculation. During biofilm development, L. monocytogenes EGDe carried out binary fission vigorously before a mature biofilm was formed and subsequently changed its cellular morphology from rod shaped to sphere shaped. Furthermore, static biofilm, which was formed after 3 days of incubation at 25°C, significantly inhibited the transfer rate of L. monocytogenes EGDe from stainless steel blades to 15 bologna slices. During 7 days of storage at 4°C, however, bacterial growth rate was not significantly impacted by whether bacteria were transferred from biofilm and the initial concentrations of transferred bacteria on the slice. In conclusion, this study is the first to report a distinct change in morphology of L. monocytogenes EGDe at the late stage of biofilm formation. More importantly, once food is contaminated by L. monocytogenes EGDe, contamination proceeds independently of biofilm development and the initial level of contamination when food is stored at 4°C, even if contamination with L. monocytogenes EGDe was initially undetectable before storage.

  19. Simultaneous and individual quantitative estimation of Salmonella, Shigella and Listeria monocytogenes on inoculated Roma tomatoes (Lycopersicon esculentum var. Pyriforme) and Serrano peppers (Capsicum annuum) using an MPN technique.

    Science.gov (United States)

    Cabrera-Díaz, E; Martínez-Chávez, L; Sánchez-Camarena, J; Muñiz-Flores, J A; Castillo, A; Gutiérrez-González, P; Arvizu-Medrano, S M; González-Aguilar, D G; Martínez-Gonzáles, N E

    2018-08-01

    Simultaneous and individual enumeration of Salmonella, Shigella and Listeria monocytogenes was compared on inoculated Roma tomatoes and Serrano peppers using an Most Probable Number (MPN) technique. Samples consisting of tomatoes (4 units) or peppers (8 units) were individually inoculated with a cocktail of three strains of Salmonella, Shigella or L. monocytogenes, or by simultaneous inoculation of three strains of each pathogen, at low (1.2-1.7 log CFU/sample) and high (2.2-2.7 log CFU/sample) inocula. Samples were analyzed by an MPN technique using universal pre-enrichment (UP) broth at 35 °C for 24 ± 2 h. The UP tubes from each MPN series were transferred to enrichment and plating media following adequate conventional methods for isolating each pathogen. Data were analyzed using multifactorial analysis of variance (p  simultaneous), type of bacteria (Salmonella > Shigella and L. monocytogenes), type of sample (UP broth > pepper and tomato), and inoculum level (high > low). The MPN technique was effective for Salmonella on both commodities. Shigella counts were higher on tomatoes compared to peppers, (p < 0.05), and for L. monocytogenes on peppers (p < 0.05). Copyright © 2018 Elsevier Ltd. All rights reserved.

  20. Modeling the growth of Listeria monocytogenes in soft blue-white cheese

    DEFF Research Database (Denmark)

    Rosshaug, Per Sand; Detmer, Ann; Ingmer, Hanne

    2012-01-01

    The aim of this study was to develop a predictive model simulating growth over time of the pathogenic bacterium Listeria monocytogenes in a soft blue-white cheese. The physicochemical properties in a matrix such as cheese are essential controlling factors influencing the growth of L. monocytogenes....... We developed a predictive tertiary model of the bacterial growth of L. monocytogenes as a function of temperature, pH, NaCl, and lactic acid. We measured the variations over time of the physicochemical properties in the cheese. Our predictive model was developed based on broth data produced...... production and retail conditions showed that the number of L. monocytogenes cells increases 3 to 3.5 log within the shelf life of the cheese....

  1. Validation of the ANSR(®) Listeria monocytogenes Method for Detection of Listeria monocytogenes in Selected Food and Environmental Samples.

    Science.gov (United States)

    Caballero, Oscar; Alles, Susan; Le, Quynh-Nhi; Gray, R Lucas; Hosking, Edan; Pinkava, Lisa; Norton, Paul; Tolan, Jerry; Mozola, Mark; Rice, Jennifer; Chen, Yi; Ryser, Elliot; Odumeru, Joseph

    2016-01-01

    Work was conducted to validate performance of the ANSR(®) for Listeria monocytogenes method in selected food and environmental matrixes. This DNA-based assay involves amplification of nucleic acid via an isothermal reaction based on nicking enzyme amplification technology. Following single-step sample enrichment for 16-24 h for most matrixes, the assay is completed in 40 min using only simple instrumentation. When 50 distinct strains of L. monocytogenes were tested for inclusivity, 48 produced positive results, the exceptions being two strains confirmed by PCR to lack the assay target gene. Forty-seven nontarget strains (30 species), including multiple non-monocytogenes Listeria species as well as non-Listeria, Gram-positive bacteria, were tested, and all generated negative ANSR assay results. Performance of the ANSR method was compared with that of the U.S. Department of Agriculture, Food Safety and Inspection Service Microbiology Laboratory Guidebook reference culture procedure for detection of L. monocytogenes in hot dogs, pasteurized liquid egg, and sponge samples taken from an inoculated stainless steel surface. In addition, ANSR performance was measured against the U.S. Food and Drug Administration Bacteriological Analytical Manual reference method for detection of L. monocytogenes in Mexican-style cheese, cantaloupe, sprout irrigation water, and guacamole. With the single exception of pasteurized liquid egg at 16 h, ANSR method performance as quantified by the number of positives obtained was not statistically different from that of the reference methods. Robustness trials demonstrated that deliberate introduction of small deviations to the normal assay parameters did not affect ANSR method performance. Results of accelerated stability testing conducted using two manufactured lots of reagents predicts stability at the specified storage temperature of 4°C of more than 1 year.

  2. Occurrence of Listeria monocytogenes in smoked fish in Sokoto ...

    African Journals Online (AJOL)

    The present study was conducted to determine the prevalence of Listeria monocytogenes in smoked fish in Sokoto, Nigeria. A total of 115 different species of smoked fish from the various retail outlets and market places within the metropolis were analysed for the presence of L. monocytogenes using ISO culture method.

  3. Effekt av ulike desinfeksjonsstrategier mot Listeria monocytogenes

    OpenAIRE

    Fossmo, Sabine

    2013-01-01

    Kontroll med bakterier som Listeria utgjør en stor utfordring for mange matprodusenter. Listeria monocytogenes er hovedsakelig et produksjonshygienisk problem, forbedret hygiene kan derfor være tiltak for å redusere overlevelse og smitteoverføring av bakterien i produksjonsmiljø. Hensikten med forsøkene i oppgaven var å undersøke effekten av ulike desinfeksjonsstrategier på drap av L. monocytogenes, både når bakteriene var i biofilm og i suspensjon. Dette inkluderte bruk av tradisjonelle desi...

  4. Listeria spp. in Street-Vended Ready-to-Eat Foods

    Science.gov (United States)

    El-Shenawy, Moustafa; El-Shenawy, Mohamed; Mañes, Jordi; Soriano, Jose M.

    2011-01-01

    Street-vended ready-to-eat food sold in Egypt, including sandwiches and dishes of traditional food, was examined for the presence of Listeria species. Out of 576 samples, 24% were found to contain Listeria species. L. monocytogenes and L. innocua were isolated from 57% and 39% of the contaminated samples, respectively. Other Listeria spp. were detected with lower frequency. L. monocytogenes of ≥103 CFU/g were detected in 7% of the total examined samples, which represent 49% of the contaminated food samples (meat, poultry, seafood, dairy products, and products of plant origin). Most of the samples contaminated by L. monocytogenes had high levels of total viable bacterial counts. The results obtained may help to clarify the epidemiology of listeriosis in the country and draw the attention of the decision makers to issue hygienic regulations for food processing industries as well as street vendors in order to ensure safe street-vended ready-to-eat food. PMID:22194742

  5. Listeria spp. in Street-Vended Ready-to-Eat Foods

    Directory of Open Access Journals (Sweden)

    Moustafa El-Shenawy

    2011-01-01

    Full Text Available Street-vended ready-to-eat food sold in Egypt, including sandwiches and dishes of traditional food, was examined for the presence of Listeria species. Out of 576 samples, 24% were found to contain Listeria species. L. monocytogenes and L. innocua were isolated from 57% and 39% of the contaminated samples, respectively. Other Listeria spp. were detected with lower frequency. L. monocytogenes of ≥103 CFU/g were detected in 7% of the total examined samples, which represent 49% of the contaminated food samples (meat, poultry, seafood, dairy products, and products of plant origin. Most of the samples contaminated by L. monocytogenes had high levels of total viable bacterial counts. The results obtained may help to clarify the epidemiology of listeriosis in the country and draw the attention of the decision makers to issue hygienic regulations for food processing industries as well as street vendors in order to ensure safe street-vended ready-to-eat food.

  6. Microbial counts of mealworm larvae (Tenebrio molitor) and crickets (Acheta domesticus and Gryllodes sigillatus) from different rearing companies and different production batches.

    Science.gov (United States)

    Vandeweyer, D; Crauwels, S; Lievens, B; Van Campenhout, L

    2017-02-02

    The rising interest in insects for human consumption and the changing regulations in Europe require a profound insight into the food safety of insects reared and sold in Western society. The microbial quality of edible insects has only been studied occasionally. This study aimed at generating an overview of intrinsic parameters (pH, water activity and moisture content) and microbial quality of fresh mealworm larvae and crickets for several rearing companies and for several batches per rearer. In total, 21 batches obtained from 7 rearing companies were subjected to analysis of intrinsic parameters, a range of plate counts and presence-absence tests for Salmonella spp. and Listeria monocytogenes. The microbial counts of the fresh insects were generally high. Different rearing batches from a single rearing company showed differences in microbial counts which could not be explained by variations in intrinsic properties. The largest variations were found in numbers of bacterial endospores, psychrotrophs and fungi. Salmonella spp. and L. monocytogenes were not detected in any of the samples. Altogether, our study shows that large variations were found between batches from individual rearers. As a consequence, no overall differences between rearers could be observed. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Monitoring paneer for Listeria monocytogenes - A high risk food ...

    African Journals Online (AJOL)

    A multiplex polymerase chain reaction (PCR) assay was developed and applied to spiked and natural paneer samples to detect Listeria monocytogenes, a high risk food pathogen. The sensitivity of the assay on L. monocytogenes spiked paneer samples was 104 cells prior to enrichment, was improved to 103 cells after 4 h ...

  8. Genome sequences of Listeria monocytogenes strains with resistance to arsenic

    Science.gov (United States)

    Listeria monocytogenes frequently exhibits resistance to arsenic. We report here the draft genome sequences of eight genetically diverse arsenic-resistant L. monocytogenes strains from human listeriosis and food-associated environments. Availability of these genomes would help to elucidate the role ...

  9. Effects of prebiotics on the infective potential of Listeria monocytogenes

    DEFF Research Database (Denmark)

    Ebersbach, Tine

    % xylooligosaccharides (XOS), galactooligosaccharides (GOS), inulin, apple pectin or polydextrose for three weeks before oral challenge with L. monocytogenes. XOS and GOS significantly improved resistance of guinea pigs to L. monocytogenes, while inulin and apple pectin decreased the resistance. No significant effect...

  10. Restraining reactive oxygen species in Listeria monocytogenes promotes the apoptosis of glial cells.

    Science.gov (United States)

    Li, Sen; Li, Yixuan; Chen, Guowei; Zhang, Jingchen; Xu, Fei; Wu, Man

    2017-07-01

    Listeria monocytogenes is a facultative anaerobic foodborne pathogen that can traverse the blood-brain barrier and cause brain infection. L. monocytogenes infection induces host cell apoptosis in several cell types. In this study, we investigated the apoptosis of human glioma cell line U251 invaded by L. monocytogenes and evaluated the function of bacterial reactive oxygen species (ROS) during infection. Bacterial ROS level was reduced by carrying out treatment with N-acetyl cysteine (NAC) and diphenyleneiodonium chloride (DPI). After infection, the apoptosis of U251 cells was examined by flow cytometry assay and propidium iodide staining. DPI and NAC efficiently decreased ROS level in L. monocytogenes without affecting bacterial growth. Moreover, the apoptosis of glial cells was enhanced upon invasion of DPI- and NAC-pretreated L. monocytogenes. Results indicate that the apoptosis of glial cells can be induced by L. monocytogenes, and that the inhibition of bacterial ROS increases the apoptosis of host cells.

  11. Survival of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes on raw peanut and pecan kernels stored at -24, 4, and 22°C.

    Science.gov (United States)

    Brar, Pardeepinder K; Proano, Lisseth G; Friedrich, Loretta M; Harris, Linda J; Danyluk, Michelle D

    2015-02-01

    Cocktails of lawn-collected cells were used to determine the survival of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes on the surface of raw peanut and pecan kernels. Kernels were inoculated with mixtures of four to five strains at 3 or 6 log CFU/g, dried at room temperature, and then stored at -24 ± 1, 4 ± 2, and 22 ± 1°C for 28 or 365 days. In most cases, rates of decline of the pathogens did not differ significantly between the two inoculum concentrations in the 28-day study. At 6 log CFU/g, populations of all pathogens were reduced by 0.5 to 1.6 log CFU/g during an initial 3-day drying period on both peanuts and pecans. The moisture content of peanuts and pecans remained stable at -24 ± 1 and 22 ± 1°C; at 4 ± 2°C, the moisture content increased from 3.8 to 5.6% on peanuts and from 2.6 to 3% on pecans over 365 days. Pathogen populations were stable on pecans stored under frozen and refrigerated conditions, except for L. monocytogenes, which declined at a rate of 0.03 log CFU/g/30 days at 4 ± 2°C. Salmonella populations were stable on peanuts stored at -24 ± 1 and 4 ± 2°C, but E. coli O157:H7 and L. monocytogenes declined at rates of 0.03 to 0.12 log CFU/g/30 days. At 22 ± 1°C, Salmonella, E. coli O157:H7, and L. monocytogenes declined at a rate of 0.22, 0.37, and 0.59 log CFU/g/30 days, respectively, on peanuts, and at 0.15, 0.34, and 1.17 log CFU/g/30 days, respectively, on pecans. Salmonella counts were above the limit of detection (0.30 log CFU/g) throughout the study. In most cases during storage, counts obtained from pecans were higher than from peanuts.

  12. Control of Listeria monocytogenes on vacuum-packaged frankfurters sprayed with lactic acid alone or in combination with sodium lauryl sulfate.

    Science.gov (United States)

    Byelashov, Oleksandr A; Kendall, Patricia A; Belk, Keith E; Scanga, John A; Sofos, John N

    2008-04-01

    U.S. regulations require that processors employ lethal or inhibitory antimicrobial alternatives in production of ready-to-eat meat and poultry products that support growth of Listeria monocytogenes and may be exposed to the processing environment after a lethality treatment. In this study, lactic acid (LA; 5%, vol/vol) and sodium lauryl sulfate (SLS; 0.5%, wt/vol) were evaluated individually or as a mixture (LASLS) for control of L. monocytogenes on frankfurters. Frankfurters were inoculated with a 10-strain mixture of L. monocytogenes, sprayed for 10 s (20 bar, 23 +/- 2 degrees C) with antimicrobials or distilled water (DW) before (LASLS or DW) or after (LA, SLS, LASLS, or DW) inoculation (4.8 +/- 0.1 log CFU/cm2), vacuum packaged, and stored at 4 degrees C for 90 days. Samples were analyzed for numbers of the pathogen (on PALCAM agar) and for total microbial counts (on tryptic soy agar with yeast extract) during storage. Spraying with DW, LA, or SLS after inoculation reduced numbers of L. monocytogenes by 1.3 +/- 0.2, 1.8 +/- 0.5, and 2.0 +/- 0.4 log CFU/cm2, respectively. The LASLS mixture applied before or after inoculation reduced pathogen populations by 1.8 +/- 0.4 and 2.8 +/- 0.2 log CFU/cm2, respectively. No further reduction by any treatment was observed during storage. The bacterial growth curves (fitted by the model of Baranyi and Roberts) indicated that the lag-phase duration of the bacterium on control samples (13.85 to 15.18 days) was extended by spraying with all solutions containing LA. For example, LA suppressed growth of L. monocytogenes for 39.14 to 41.01 days. Pathogen growth rates also were lower on frankfurters sprayed after inoculation with LA or LASLS compared to those sprayed with DW. Therefore, spraying frankfurters with a mixture of LA and SLS may be a useful antilisterial alternative treatment for ready-to-eat meat and poultry products.

  13. Listeria monocytogenes internalizes in Romaine Lettuce grown in greenhouse conditions

    Science.gov (United States)

    Listeria monocytogenes has been implicated in a number of outbreaks involving fresh produce, including an outbreak in 2016 resulting from contaminated packaged salads. The persistence and internalization potential of L. monocytogenes in romaine lettuce was evaluated, and the persistence of two L. mo...

  14. Growth inhibition of Listeria monocytogenes by a nonbacteriocinogenic Carnobacterium piscicola

    DEFF Research Database (Denmark)

    Nilsson, Lilian; Bech Hansen, T.; Garrido, P.

    2005-01-01

    Aims: This study elucidates the mechanisms by which a nonbacteriocinogenic Carnobacterium piscicola inhibits growth of Listeria monocytogenes. Methods and Results: Listeria monocytogenes was exposed to live cultures of a bacteriocin-negative variant of C. piscicola A9b in co-culture, in a diffusion...... chamber system, and to a cell-free supernatant. Suppression of maximum cell density (0-3.5 log units) of L. monocytogenes was proportional to initial levels of C. pisciola (10(3)-10(7) CFU ml(-1)). Cell-to-cell contact was not required to cause inhibition. The cell-free C. piscicola supernatant caused...... a decrease in L. monocytogenes maximum cell density, which was abolished by glucose addition but not by amino acid, vitamin or mineral addition. The fermentate also gave rise to a longer lag phase and a reduction in growth rate. These effects were independent of glucose and may have been caused by acetate...

  15. Inactivation of Salmonella enterica and Listeria monocytogenes in cantaloupe puree by high hydrostatic pressure with/without added ascorbic acid.

    Science.gov (United States)

    Mukhopadhyay, Sudarsan; Sokorai, Kimberly; Ukuku, Dike; Fan, Xuetong; Juneja, Vijay; Sites, Joseph; Cassidy, Jennifer

    2016-10-17

    The objective of this research was to evaluate and develop a method for inactivation of Salmonella enterica and Listeria monocytogenes in cantaloupe puree (CP) by high hydrostatic pressure (HHP). Cantaloupe being the most netted varieties of melons presents a greater risk of pathogen transmission. Freshly prepared CP with or without 0.1% ascorbic acid (AA) was inoculated with a bacterial cocktail composed of a three serotype mixture of S. enterica (S. Poona, S. Newport H1275 and S. Stanley H0558) and a mixture of three strains of L. monocytogenes (Scott A, 43256 and 51742) to a population of ca. 10(8)CFU/g. Double sealed and double bagged inoculated CP (ca. 5g) were pressure treated at 300, 400 and 500MPa at 8°C and 15°C for 5min. Data indicated increased inactivation of both Salmonella and Listeria spp. with higher pressure. Log reduction for CP at 300MPa, 8°C for 5min was 2.4±0.2 and 1.6±0.5logCFU/g for Salmonella and Listeria, respectively. Survivability of the pathogens was significantly compromised at 400MPa and 8°C, inactivating 4.5±0.3logCFU/g of Salmonella and 3.0±0.4logCFU/g of Listeria spp. Complete inactivation of the pathogens in the puree (log reduction >6.7logCFU/g), with or without AA, was achieved when the pressure was further increased to 500MPa, except that for Listeria containing no AA at 8°C. Listeria presented higher resistance to pressure treatment compared to Salmonella spp. Initial temperatures (8 and 15°C) had no significant influence on Salmonella log reductions. Log reduction of pathogens increased but not significantly with increase of temperature. AA did not show any significant antimicrobial activity. Viable counts were about 0.2-0.4logCFU/g less in presence of 0.1% AA. These data validate that HHP can be used as an effective method for decontamination of cantaloupe puree. Published by Elsevier B.V.

  16. Prevalence and serotypes of Listeria monocytogenes contamination in Chinese beef processing plants.

    Science.gov (United States)

    Zhu, Lixian; Feng, Xiaohui; Zhang, Lihua; Zhu, Ruiliang; Luo, Xin

    2012-06-01

    The aim of this work was to study the epidemiology of Listeria spp., particularly Listeria monocytogenes, and to identify the serotypes present in contaminated samples from beef processing plants in China. A total of 439 samples were obtained from bovine feces, hides, and carcasses at three commercial processing plants. A standard protocol (ISO 11290-1) was followed to detect Listeria spp. and L. monocytogenes, and multiplex polymerase chain reaction was used to identify the various L. monocytogenes serotypes. The overall prevalences of Listeria spp. and L. monocytogenes were 65.6% and 26.4%, respectively, and the contamination was highest in the hide samples. The identified L. monocytogenes serotypes were 1/2c and 1/2a. The results of the current study indicate that Listeria spp. contamination is common in Chinese beef processing plants; specific measures should be taken to prevent and/or treat L. monocytogenes contamination of feces and hides in beef slaughter plants. Furthermore, because Listeria spp. contamination was found to be prevalent, it should, therefore, be studied further. The prevention of cases of sporadic listeriosis in China should also be addressed.

  17. Survival strategies of Listeria monocytogenes - roles of regulators and transporters

    NARCIS (Netherlands)

    Wemekamp-Kamphuis, H.H.

    2003-01-01

    Outbreaks of the food-borne pathogen Listeria monocytogenes are mainly associated with ready-to-eatfoods. Survival strategies of L. monocytogenes in relation to minimally processed foods were studied.

  18. Microbiological criteria for Listeria monocytogenes in foods under special consideration of risk assessment approaches

    DEFF Research Database (Denmark)

    Nørrung, Birgit

    2000-01-01

    This paper shortly summarizes data related to risk assessment of Listeria monocytogenes. From available data on risk assessment, it is concluded that the levels of L. monocytogenes consumed is an important factor affecting the incidence of listeriosis. Foods that do not support the growth of L....... monocytogenes are unlikely to be a source of listeriosis, whereas foods that support the growth to high levels, should be the target of risk management efforts. Based on current epidemiological information from several countries, a concentration of L. monocytogenes not exceeding 100/g of food at the time...... of L. monocytogenes in the food during prevailing storage and distribution conditions is needed....

  19. Prevalence of Listeria monocytogenes in raw milk in North Lebanon

    International Nuclear Information System (INIS)

    Al Kassaa, I; El Omari, Kh.; Esmail, B.; Hamze, M; Saati, M.

    2016-01-01

    Listeriosis, although a zoonosis, is an invasive disease that can affect newborns, pregnant women and immunocompromised adults. Clinical manifestations can be expressedby febrile gastroenteritis, invasive forms including severe sepsis, meningitis, rhombencephalitis, prenatal infections and abortions. Species of Listeria bacteria are ubiquitous and adaptableto the environment in animal and plant foods. This study aimed to determine the prevalence of Listeria monocytogenes in 100 samples of fresh cow milk collected from different areas of North Lebanon. Listeria monocytogenes was detected by using the Grand VIDAS technique (Biomérieux France). The results obtained revealed the absence of Listeria monocytogenes inall analyzed samples. (Author)

  20. Rapid differentiation of Listeria monocytogenes epidemic clones III and IV and their intact compared with heat-killed populations using Fourier transform infrared spectroscopy and chemometrics.

    Science.gov (United States)

    Nyarko, Esmond B; Puzey, Kenneth A; Donnelly, Catherine W

    2014-06-01

    subtyping methods, and can be used for L. monocytogenes strain typing by food industries and public health agencies to enable faster response and intervention to listeriosis outbreaks. FT-IR can also be applied for routine monitoring of the pathogen in food processing plants and for investigating postprocessing contamination because it is capable of differentiating heat-killed and viable L. monocytogenes populations. © 2014 Institute of Food Technologists®

  1. Microbial survey of ready-to-eat salad ingredients sold at retail reveals the occurrence and the persistence of Listeria monocytogenes Sequence Types 2 and 87 in pre-packed smoked salmon.

    Science.gov (United States)

    Chau, Man Ling; Aung, Kyaw Thu; Hapuarachchi, Hapuarachchige Chanditha; Lee, Pei Sze Valarie; Lim, Pei Ying; Kang, Joanne Su Lin; Ng, Youming; Yap, Hooi Ming; Yuk, Hyun-Gyun; Gutiérrez, Ramona Alikiiteaga; Ng, Lee Ching

    2017-02-28

    As the preparation of salads involves extensive handling and the use of uncooked ingredients, they are particularly vulnerable to microbial contamination. This study aimed to determine the microbial safety and quality of pre-packed salads and salad bar ingredients sold in Singapore, so as to identify public health risks that could arise from consuming salads and to determine areas for improvement in the management of food safety. The most frequently encountered organism in pre-packed salad samples was B. cereus, particularly in pasta salads (33.3%, 10/30). The most commonly detected organism in salad bar ingredients was L. monocytogenes, in particular seafood ingredients (44.1%, 15/34), largely due to contaminated smoked salmon. Further investigation showed that 21.6% (37/171) of the pre-packed smoked salmon sold in supermarkets contained L. monocytogenes. Significantly higher prevalence of L. monocytogenes and higher Standard Plate Count were detected in smoked salmon at salad bars compared to pre-packed smoked salmon in supermarkets, which suggested multiplication of the organism as the products move down the supply chain. Further molecular analysis revealed that L. monocytogenes Sequence Type (ST) 2 and ST87 were present in a particular brand of pre-packed salmon products over a 4-year period, implying a potential persistent contamination problem at the manufacturing level. Our findings highlighted a need to improve manufacturing and retail hygiene processes as well as to educate vulnerable populations to avoid consuming food prone to L. monocytogenes contamination.

  2. Prebiotic Oligosaccharides Potentiate Host Protective Responses against L. Monocytogenes Infection

    Directory of Open Access Journals (Sweden)

    Poyin Chen

    2017-12-01

    Full Text Available Prebiotic oligosaccharides are used to modulate enteric pathogens and reduce pathogen shedding. The interactions with prebiotics that alter Listeria monocytogenes infection are not yet clearly delineated. L. monocytogenes cellular invasion requires a concerted manipulation of host epithelial cell membrane receptors to initiate internalization and infection often via receptor glycosylation. Bacterial interactions with host glycans are intimately involved in modulating cellular responses through signaling cascades at the membrane and in intracellular compartments. Characterizing the mechanisms underpinning these modulations is essential for predictive use of dietary prebiotics to diminish pathogen association. We demonstrated that human milk oligosaccharide (HMO pretreatment of colonic epithelial cells (Caco-2 led to a 50% decrease in Listeria association, while Biomos pretreatment increased host association by 150%. L. monocytogenes-induced gene expression changes due to oligosaccharide pretreatment revealed global alterations in host signaling pathways that resulted in differential subcellular localization of L. monocytogenes during early infection. Ultimately, HMO pretreatment led to bacterial clearance in Caco-2 cells via induction of the unfolded protein response and eIF2 signaling, while Biomos pretreatment resulted in the induction of host autophagy and L. monocytogenes vacuolar escape earlier in the infection progression. This study demonstrates the capacity of prebiotic oligosaccharides to minimize infection through induction of host-intrinsic protective responses.

  3. Deciphering the landscape of host barriers to Listeria monocytogenes infection.

    Science.gov (United States)

    Zhang, Ting; Abel, Sören; Abel Zur Wiesch, Pia; Sasabe, Jumpei; Davis, Brigid M; Higgins, Darren E; Waldor, Matthew K

    2017-06-13

    Listeria monocytogenes is a common food-borne pathogen that can disseminate from the intestine and infect multiple organs. Here, we used sequence tag-based analysis of microbial populations (STAMP) to investigate L monocytogenes population dynamics during infection. We created a genetically barcoded library of murinized L monocytogenes and then used deep sequencing to track the pathogen's dissemination routes and quantify its founding population ( N b ) sizes in different organs. We found that the pathogen disseminates from the gastrointestinal tract to distal sites through multiple independent routes and that N b sizes vary greatly among tissues, indicative of diverse host barriers to infection. Unexpectedly, comparative analyses of sequence tags revealed that fecally excreted organisms are largely derived from the very small number of L. monocytogenes cells that colonize the gallbladder. Immune depletion studies suggest that distinct innate immune cells restrict the pathogen's capacity to establish replicative niches in the spleen and liver. Finally, studies in germ-free mice suggest that the microbiota plays a critical role in the development of the splenic, but not the hepatic, barriers that prevent L. monocytogenes from seeding these organs. Collectively, these observations illustrate the potency of the STAMP approach to decipher the impact of host factors on population dynamics of pathogens during infection.

  4. Listeria monocytogenes: diagnostic problems

    NARCIS (Netherlands)

    Beumer, R.R.; Hazeleger, W.C.

    2003-01-01

    The first isolation methods for the detection of Listeria spp. were generally based on the direct culture of samples on simple agar media, but isolation of the pathogenic Listeria monocytogenes was difficult. In time, new techniques were developed, based on a variety of selective and elective agents

  5. Assessment of Listeria sp. Interference Using a Molecular Assay To Detect Listeria monocytogenes in Food.

    Science.gov (United States)

    Zittermann, Sandra I; Stanghini, Brenda; See, Ryan Soo; Melano, Roberto G; Boleszczuk, Peter; Murphy, Allana; Maki, Anne; Mallo, Gustavo V

    2016-01-01

    Detection of Listeria monocytogenes in food is currently based on enrichment methods. When L. monocytogenes is present with other Listeria species in food, the species compete during the enrichment process. Overgrowth competition of the nonpathogenic Listeria species might result in false-negative results obtained with the current reference methods. This potential issue was noted when 50 food samples artificially spiked with L. monocytogenes were tested with a real-time PCR assay and Canada's current reference method, MFHPB-30. Eleven of the samples studied were from foods naturally contaminated with Listeria species other than those used for spiking. The real-time PCR assay detected L. monocytogenes in all 11 of these samples; however, only 6 of these samples were positive by the MFHPB-30 method. To determine whether L. monocytogenes detection can be affected by other species of the same genus due to competition, an L. monocytogenes strain and a Listeria innocua strain with a faster rate of growth in the enrichment broth were artificially coinoculated at different ratios into ground pork meat samples and cultured according to the MFHPB-30 method. L. monocytogenes was detected only by the MFHPB-30 method when L. monocytogenes/L. innocua ratios were 6.0 or higher. In contrast, using the same enrichments, the real-time PCR assay detected L. monocytogenes at ratios as low as 0.6. Taken together, these findings support the hypothesis that L. monocytogenes can be outcompeted by L. innocua during the MFHPB-30 enrichment phase. However, more reliable detection of L. monocytogenes in this situation can be achieved by a PCR-based method mainly because of its sensitivity.

  6. Comparative experimental infection of Listeria monocytogenes and Listeria ivanovii in bovine trophoblasts.

    Science.gov (United States)

    Rocha, Cláudia E; Mol, Juliana P S; Garcia, Luize N N; Costa, Luciana F; Santos, Renato L; Paixão, Tatiane A

    2017-01-01

    Listeria monocytogenes is a Gram-positive, facultative intracellular and invasive bacterium that has tropism to the placenta, and causes fetal morbidity and mortality in several mammalian species. While infection with L. monocytogenes and L. ivanovii are known as important causes of abortion and reproductive failure in cattle, the pathogenesis of maternal-fetal listeriosis in this species is poorly known. This study used the bovine chorioallantoic membrane explant model to investigate the kinetics of L. monocytogenes, L. ivanovii, and L. innocua infections in bovine trophoblastic cells for up to 8 h post infection. L. monocytogenes and L. ivanovii were able to invade and multiply in trophoblastic cells without causing cell death or inducing expression of pro-inflammatory genes. Although L. innocua was unable to multiply in bovine trophoblastic cells, it induced transcription of the pro-inflammatory mediator CXCL6. This study demonstrated for the first time the susceptibility of bovine trophoblastic cells to L. monocytogenes and L. ivanovii infection.

  7. Growth potential of Salmonella spp. and Listeria monocytogenes in nine types of ready-to-eat vegetables stored at variable temperature conditions during shelf-life.

    Science.gov (United States)

    Sant'Ana, Anderson S; Barbosa, Matheus S; Destro, Maria Teresa; Landgraf, Mariza; Franco, Bernadette D G M

    2012-06-15

    Growth potential (δ) is defined as the difference between the population of a microorganism at the end of shelf-life of specific food and its initial population. The determination of δ of Salmonella and Listeria monocytogenes in RTE vegetables can be very useful to determine likely threats to food safety. However, little is known on the behavior of these microorganisms in several RTE vegetables. Therefore, the aim of this study was to determine the δ of both pathogens in nine different types of RTE vegetables (escarole, collard green, spinach, watercress, arugula, grated carrot, green salad, and mix for yakisoba) stored at refrigeration (7°C) and abuse temperature (15°C). The population of aerobic microorganisms and lactic acid bacteria, including those showing antimicrobial activity has been also determined. Results indicated that L. monocytogenes was able to grow (δ≥0.5 log(10)) in more storage conditions and vegetables than Salmonella. Both microorganisms were inhibited in carrots, although a more pronounced effect has been observed against L. monocytogenes. The highest δ values were obtained when the RTE vegetables were stored 15°C/6days in collard greens (δ=3.3) and arugula (δ=3.2) (L. monocytogenes) and arugula (δ=4.1) and escarole (δ=2.8) (Salmonella). In most vegetables and storage conditions studied, the counts of total aerobic microorganisms raised significantly independent of the temperature of storage (pvegetables partially or fully stored at abuse temperature with recovery of isolates showing antimicrobial activity. In conclusion, the results of this study show that Salmonella and L. monocytogenes may grow and reach high populations in RTE vegetables depending on storage conditions and the definition of effective intervention strategies are needed to control their growth in these products. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Incidence and control of Listeria monocytogenes in foods in Denmark

    DEFF Research Database (Denmark)

    Nørrung, Birgit; Andersen, Jens Kirk; Schlundt, Jørgen

    1999-01-01

    The Danish regulatory policy on Listeria monocytogenes in foods is based on the principles of HACCP and was developed using a health risk assessment approach. The Danish policy focuses examinations and criteria for L. monocytogenes in ready-to-eat foods and is based on a combination of inspection...

  9. The occurrence, transmission, virulence and antibiotic resistance of Listeria monocytogenes in fish processing plant.

    Science.gov (United States)

    Skowron, Krzysztof; Kwiecińska-Piróg, Joanna; Grudlewska, Katarzyna; Świeca, Agnieszka; Paluszak, Zbigniew; Bauza-Kaszewska, Justyna; Wałecka-Zacharska, Ewa; Gospodarek-Komkowska, Eugenia

    2018-06-13

    The aim of this research was to investigate the occurrence of Listeria monocytogenes in fish and fish processing plant and to determine their transmission, virulence and antibiotic resistance. L. monocytogenes was isolated according to the ISO 11290-1. The identification of L. monocytogenes was confirmed by multiplex PCR method. Genetic similarity of L. monocytogenes strains was determined with the Pulsed-Filed Gene Electrophoresis (PFGE) method. The multiplex PCR was used for identification of L. monocytogenes serogroups and detection of selected virulence genes (actA, fbpA, hlyA, iap, inlA, inlB, mpl, plcA, plcB, prfA). The L. monocytogens isolates susceptibility to penicillin, ampicillin, meropenem, erythromycin, trimethoprim/sulfamethoxazole was evaluated with disc diffusion method according to EUCAST v. 7.1. The presence of 237 L. monocytogenes isolates (before genetic similarity assessment) in 614 examined samples was confirmed. After strain differentiation by PFGE techniques the presence of 161 genetically different strains were confirmed. The genetic similarity of the examined isolates suggested that the source of the L. monocytogenes strains were fishes originating from farms. All tested strains possessed all detected virulence genes. Among examined strains, the most (26, 38.6%) belonged to the group 1/2a-3a. The most of tested strains were resistant to erythromycin (47.1%) and trimethoprim/sulfamethoxazole (47.1%). Copyright © 2018. Published by Elsevier B.V.

  10. Spontaneous Loss of Virulence in Natural Populations of Listeria monocytogenes.

    Science.gov (United States)

    Maury, Mylène M; Chenal-Francisque, Viviane; Bracq-Dieye, Hélène; Han, Lei; Leclercq, Alexandre; Vales, Guillaume; Moura, Alexandra; Gouin, Edith; Scortti, Mariela; Disson, Olivier; Vázquez-Boland, José A; Lecuit, Marc

    2017-11-01

    The pathogenesis of Listeria monocytogenes depends on the ability of this bacterium to escape from the phagosome of the host cells via the action of the pore-forming toxin listeriolysin O (LLO). Expression of the LLO-encoding gene ( hly ) requires the transcriptional activator PrfA, and both hly and prfA genes are essential for L. monocytogenes virulence. Here, we used the hemolytic activity of LLO as a phenotypic marker to screen for spontaneous virulence-attenuating mutations in L. monocytogenes Sixty nonhemolytic isolates were identified among a collection of 57,820 confirmed L. monocytogenes strains isolated from a variety of sources (0.1%). In most cases (56/60; 93.3%), the nonhemolytic phenotype resulted from nonsense, missense, or frameshift mutations in prfA Five strains carried hly mutations leading to a single amino acid substitution (G299V) or a premature stop codon causing strong virulence attenuation in mice. In one strain, both hly and gshF (encoding a glutathione synthase required for full PrfA activity) were missing due to genomic rearrangements likely caused by a transposable element. The PrfA/LLO loss-of-function (PrfA - /LLO - ) mutants belonged to phylogenetically diverse clades of L. monocytogenes , and most were identified among nonclinical strains (57/60). Consistent with the rare occurrence of loss-of-virulence mutations, we show that prfA and hly are under purifying selection. Although occurring at a low frequency, PrfA - /LLO - mutational events in L. monocytogenes lead to niche restriction and open an evolutionary path for obligate saprophytism in this facultative intracellular pathogen. Copyright © 2017 Maury et al.

  11. Efficacy of chlorine dioxide against Listeria monocytogenes in brine chilling solutions.

    Science.gov (United States)

    Valderrama, W B; Mills, E W; Cutter, C N

    2009-11-01

    Chilled brine solutions are used by the food industry to rapidly cool ready-to-eat meat products after cooking and before packaging. Chlorine dioxide (ClO(2)) was investigated as an antimicrobial additive to eliminate Listeria monocytogenes. Several experiments were performed using brine solutions made of sodium chloride (NaCl) and calcium chloride (CaCl(2)) inoculated with L. monocytogenes and/or treated with 3 ppm of ClO(2). First, 10 and 20% CaCl(2) and NaCl solutions (pH 7.0) were inoculated with a five-strain cocktail of L. monocytogenes to obtain approximately 7 log CFU/ml and incubated 8 h at 0 degrees C. The results demonstrated that L. monocytogenes survived in 10% CaCl(2), 10 and 20% NaCl, and pure water. L. monocytogenes levels were reduced approximately 1.2 log CFU/ml in 20% CaCl(2). Second, inoculated ( approximately 7 log CFU/ml) brine solutions (10 and 20% NaCl and 10% CaCl(2)) treated with 3 ppm of ClO(2) resulted in a approximately 4-log reduction of the pathogen within 90 s. The same was not observed in a solution of 20% CaCl(2); further investigation demonstrated that high levels of divalent cations interfere with the disinfectant. Spent brine solutions from hot dog and ham chilling were treated with ClO(2) at concentrations of 3 or 30 ppm. At these concentrations, ClO(2) did not reduce L. monocytogenes. Removal of divalent cations and organic material in brine solutions prior to disinfection with ClO(2) should be investigated to improve the efficacy of the compound against L. monocytogenes. The information from this study may be useful to processing establishments and researchers who are investigating antimicrobials in chilling brine solutions.

  12. Review of Prosthetic Joint Infection from Listeria monocytogenes.

    Science.gov (United States)

    Bader, Gilbert; Al-Tarawneh, Mohammed; Myers, James

    2016-12-01

    Prosthetic joint infection from Listeria monocytogenes is rare. We decided to shed light on this illness and review the reported cases to better understand its characteristics. We conducted a comprehensive review of the English literature using PubMed. We also included one case that we had managed. We found 25 cases of prosthetic joint infection from L. monocytogenes reported individually and a retrospective study of 43 cases of joint and bone listerial infection, including 34 with prosthetic joint infection, conducted in France. We have described their clinical and para-clinical features and tried to elaborate on the pathophysiology, treatment, and prevention. Prosthetic joint infection from L. monocytogenes is mainly late. Systemic inflammation may be absent. Although rare, it must be suspected in patients at high risk for both prosthetic joint and listerial infections. In addition, those patients must be instructed on appropriate preventive measures.

  13. Animal models for oral transmission of Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Sarah E F D'Orazio

    2014-02-01

    Full Text Available Listeria monocytogenes has been recognized as a food borne pathogen in humans since the 1980s, but we still understand very little about oral transmission of L. monocytogenes or the host factors that determine susceptibility to gastrointestinal infection, due to the lack of an appropriate small animal model of oral listeriosis. Early feeding trials suggested that many animals were highly resistant to oral infection, and the more reproducible intravenous or intraperitoneal routes of inoculation soon came to be favored. There are a fair number of previously published studies using an oral infection route, but the work varies widely in terms of bacterial strain choice, the methods used for oral transmission, and various manipulations used to enhance infectivity. This mini review will summarize the published literature using oral routes of L. monocytogenes infection and will highlight recent technological advances that have made oral infection a more attractive model system.

  14. Listeria monocytogenes en alimentos: ¿son todos los aislamientos igual de virulentos? Foodborne Listeria monocytogenes: are all the isolates equally virulent?

    Directory of Open Access Journals (Sweden)

    V. López

    2006-12-01

    Full Text Available Listeria monocytogenes es un patógeno humano que se transmite a través de los alimentos y que causa infecciones graves, con una alta tasa de mortalidad. A pesar de la ubicuidad del microorganismo, la tasa real de la enfermedad es bastante baja y se asocia casi siempre a condiciones predisponentes. Tradicionalmente se consideraba que los aislamientos presentes en los alimentos y en el ambiente tenían la misma capacidad patogénica que los aislamientos de origen clínico. Pero el análisis de mutaciones en los genes de determinados factores de virulencia (internalina, hemolisina, fosfolipasas, proteína de superficie ActA y proteína reguladora PrfA, los estudios cuantitativos realizados con cultivos celulares y la genética de poblaciones, están replanteando la discusión sobre la variabilidad de la virulencia de L. monocytogenes. A pesar de todos estos avances, no existe un único marcador que permita comprobar la virulencia de los aislamientos naturales de esta especie. Probablemente en el futuro, la combinación de diferentes marcadores moleculares permitirá detectar los alimentos contaminados sólo por los clones virulentos de L. monocytogenes, con lo que se mejorará la prevención de la listeriosis humana transmitida por alimentos.Listeria monocytogenes is a foodborne human pathogen responsible for invasive infections presenting overall a high mortality. Despite the ubiquity of the microorganism, the actual disease rate is quite low and the disease is most often associated with an underlying predisposition. Foodborne and environmental isolates were traditionally considered of similar pathogenicity compared to clinical isolates. But the analysis of mutations in the genes encoding specific virulence factors (internalin, hemolysin, phospholipases, surface protein ActA and regulator protein PrfA, quantitative studies with cell cultures and population genetics have raised considerable concerns about virulence differences among L

  15. Genotyping of Listeria monocytogenes isolates from poultry carcasses using high resolution melting (HRM) analysis.

    Science.gov (United States)

    Sakaridis, Ioannis; Ganopoulos, Ioannis; Madesis, Panagiotis; Tsaftaris, Athanasios; Argiriou, Anagnostis

    2014-01-02

    An outbreak situation of human listeriosis requires a fast and accurate protocol for typing Listeria monocytogenes . Existing techniques are either characterized by low discriminatory power or are laborious and require several days to give a final result. Polymerase chain reaction (PCR) coupled with high resolution melting (HRM) analysis was investigated in this study as an alternative tool for a rapid and precise genotyping of L. monocytogenes isolates. Fifty-five isolates of L. monocytogenes isolated from poultry carcasses and the environment of four slaughterhouses were typed by HRM analysis using two specific markers, internalin B and ssrA genes. The analysis of genotype confidence percentage of L. monocytogenes isolates produced by HRM analysis generated dendrograms with two major groups and several subgroups. Furthermore, the analysis of the HRM curves revealed that all L. monocytogenes isolates could easily be distinguished. In conclusion, HRM was proven to be a fast and powerful tool for genotyping isolates of L. monocytogenes .

  16. Prevalence of Listeria monocytogenes in poultry production in France.

    Science.gov (United States)

    Chemaly, Marianne; Toquin, Marie-Therese; Le Nôtre, Yolene; Fravalo, Philippe

    2008-10-01

    This study aimed to update and create a data set from laying hens and broilers regarding contamination by Listeria monocytogenes. Two hundred laying-hen flocks were sampled, with 88 flocks reared in cages and 112 reared on the floor. One hundred forty-five broiler flocks were sampled, with 85 conventional and 60 free-range flocks. A total of 774 and 725 samples were analyzed from laying hens and broilers, respectively. L. monocytogenes was detected in 31 of 200 flocks, yielding an estimated prevalence of 15.5% in laying-hen flocks. Among positive flocks, there appeared a significant (P = 0.004) difference between caged and floor-reared hens, with a higher detection in dust samples from floor-reared hens. In positive caged hen flocks, significant (P = 0.028) differences between dust and fecal samples appeared, with a higher detection in feces than in dust samples. In broiler flocks, L. monocytogenes was isolated in 46 of 145 flocks, yielding an estimated prevalence of 32% (28% in conventional flocks versus 37% in the free-range flocks). L. monocytogenes was isolated in samples taken from conventional flocks with a lower frequency than in free-range flocks (13 versus 18%, respectively). The serotyping of L. monocytogenes strains showed that the majority belonged to type 1/2a in laying-hen flocks (74.3%) and in broiler flocks (40.5%). A significant difference (P = 0.007) between laying hens and broilers was shown for serogroup 4 and for serovar 1/2b (P = 0.007); these serogroups were more prevalent in broilers (40%) than in laying hens (5.7%).

  17. PASTEURISASI HIGH TEMPERATURE SHORT TIME (HTST) SUSU TERHADAP Listeria monocytogenes PADA PENYIMPANAN REFRIGERATOR

    OpenAIRE

    SABIL, SYAHRIANA

    2015-01-01

    2015 SYAHRIANA SABIL (I 111 11 273). Pasteurisasi High Temperature Short Time (HTST) Susu terhadap Listeria monocytogenes pada Penyimpanan Refrigerator. Dibimbing oleh RATMAWATI MALAKA dan FARIDA NUR YULIATI. Pasteurisasi High Temperature Short Time (HTST) merupakan proses pemanasan susu di bawah titik didih yang diharapkan dapat membunuh Listeria monocytogenes (L. monocytogenes) karena bersifat patogen dan mengakibatkan listeriosis yang merupakan penyakit zoonosis. Tu...

  18. Romer Labs RapidChek®Listeria monocytogenes Test System for the Detection of L. monocytogenes on Selected Foods and Environmental Surfaces.

    Science.gov (United States)

    Juck, Gregory; Gonzalez, Verapaz; Allen, Ann-Christine Olsson; Sutzko, Meredith; Seward, Kody; Muldoon, Mark T

    2018-04-27

    The Romer Labs RapidChek ® Listeria monocytogenes test system (Performance Tested Method ℠ 011805) was validated against the U.S. Department of Agriculture-Food Safety and Inspection Service Microbiology Laboratory Guidebook (USDA-FSIS/MLG), U.S. Food and Drug Association Bacteriological Analytical Manual (FDA/BAM), and AOAC Official Methods of Analysis ℠ (AOAC/OMA) cultural reference methods for the detection of L. monocytogenes on selected foods including hot dogs, frozen cooked breaded chicken, frozen cooked shrimp, cured ham, and ice cream, and environmental surfaces including stainless steel and plastic in an unpaired study design. The RapidChek method uses a proprietary enrichment media system, a 44-48 h enrichment at 30 ± 1°C, and detects L. monocytogenes on an immunochromatographic lateral flow device within 10 min. Different L. monocytogenes strains were used to spike each of the matrixes. Samples were confirmed based on the reference method confirmations and an alternate confirmation method. A total of 140 low-level spiked samples were tested by the RapidChek method after enrichment for 44-48 h in parallel with the cultural reference method. There were 88 RapidChek presumptive positives. One of the presumptive positives was not confirmed culturally. Additionally, one of the culturally confirmed samples did not exhibit a presumptive positive. No difference between the alternate confirmation method and reference confirmation method was observed. The respective cultural reference methods (USDA-FSIS/MLG, FDA/BAM, and AOAC/OMA) produced a total of 63 confirmed positive results. Nonspiked samples from all foods were reported as negative for L. monocytogenes by all methods. Probability of detection analysis demonstrated no significant differences in the number of positive samples detected by the RapidChek method and the respective cultural reference method.

  19. Recombinant phage probes for Listeria monocytogenes

    Science.gov (United States)

    Carnazza, S.; Gioffrè, G.; Felici, F.; Guglielmino, S.

    2007-10-01

    Monitoring of food and environmental samples for biological threats, such as Listeria monocytogenes, requires probes that specifically bind biological agents and ensure their immediate and efficient detection. There is a need for robust and inexpensive affinity probes as an alternative to antibodies. These probes may be recruited from random peptide libraries displayed on filamentous phage. In this study, we selected from two phage peptide libraries phage clones displaying peptides capable of specific and strong binding to the L. monocytogenes cell surface. The ability of isolated phage clones to interact specifically with L. monocytogenes was demonstrated using enzyme-linked immunosorbent assay (ELISA) and confirmed by co-precipitation assay. We also assessed the sensitivity of phage-bacteria binding by PCR on phage-captured Listeria cells, which could be detected at a concentration of 104 cells ml-1. In addition, as proof-of-concept, we tested the possibility of immobilizing the affinity-selected phages to a putative biosensor surface. The quality of phage deposition was monitored by ELISA and fluorescent microscopy. Phage-bacterial binding was confirmed by high power optical phase contrast microscopy. Overall, the results of this work validate the concept of affinity-selected recombinant filamentous phages as probes for detecting and monitoring bacterial agents under any conditions that warrant their recognition, including in food products.

  20. Dual-species biofilm of Listeria monocytogenes and Escherichia coli on stainless steel surface.

    Science.gov (United States)

    de Grandi, Aline Zago; Pinto, Uelinton Manoel; Destro, Maria Teresa

    2018-04-12

    Listeria monocytogenes is a Gram-positive bacterium commonly associated with foodborne diseases. Due its ability to survive under adverse environmental conditions and to form biofilm, this bacterium is a major concern for the food industry, since it can compromise sanitation procedures and increase the risk of post-processing contamination. Little is known about the interaction between L. monocytogenes and Gram-negative bacteria on biofilm formation. Thus, in order to evaluate this interaction, Escherichia coli and L. monocytogenes were tested for their ability to form biofilms together or in monoculture. We also aimed to evaluate the ability of L. monocytogenes 1/2a and its isogenic mutant strain (ΔprfA ΔsigB) to form biofilm in the presence of E. coli. We assessed the importance of the virulence regulators, PrfA and σ B , in this process since they are involved in many aspects of L. monocytogenes pathogenicity. Biofilm formation was assessed using stainless steel AISI 304 #4 slides immersed into brain heart infusion broth, reconstituted powder milk and E. coli preconditioned medium at 25 °C. Our results indicated that a higher amount of biofilm was formed by the wild type strain of L. monocytogenes than by its isogenic mutant, indicating that prfA and sigB are important for biofilm development, especially maturation under our experimental conditions. The presence of E. coli or its metabolites in preconditioned medium did not influence biofilm formation by L. monocytogenes. Our results confirm the possibility of concomitant biofilm formation by L. monocytogenes and E. coli, two bacteria of major significance in the food industry.

  1. Novel Cadmium Resistance Determinant in Listeria monocytogenes.

    Science.gov (United States)

    Parsons, Cameron; Lee, Sangmi; Jayeola, Victor; Kathariou, Sophia

    2017-03-01

    Listeria monocytogenes is a foodborne pathogen that can cause severe disease (listeriosis) in susceptible individuals. It is ubiquitous in the environment and often exhibits resistance to heavy metals. One of the determinants that enables Listeria to tolerate exposure to cadmium is the cadAC efflux system, with CadA being a P-type ATPase. Three different cadA genes (designated cadA1 to cadA3 ) were previously characterized in L. monocytogenes A novel putative cadmium resistance gene ( cadA4 ) was recently identified through whole-genome sequencing, but experimental confirmation for its involvement in cadmium resistance is lacking. In this study, we characterized cadA4 in L. monocytogenes strain F8027, a cadmium-resistant strain of serotype 4b. By screening a mariner-based transposon library of this strain, we identified a mutant with reduced tolerance to cadmium and that harbored a single transposon insertion in cadA4 The tolerance to cadmium was restored by genetic complementation with the cadmium resistance cassette ( cadA4C ), and enhanced cadmium tolerance was conferred to two unrelated cadmium-sensitive strains via heterologous complementation with cadA4C Cadmium exposure induced cadA4 expression, even at noninhibitory levels. Virulence assessments in the Galleria mellonella model suggested that a functional cadA4 suppressed virulence, potentially promoting commensal colonization of the insect larvae. Biofilm assays suggested that cadA4 inactivation reduced biofilm formation. These data not only confirm cadA4 as a novel cadmium resistance determinant in L. monocytogenes but also provide evidence for roles in virulence and biofilm formation. IMPORTANCE Listeria monocytogenes is an intracellular foodborne pathogen causing the disease listeriosis, which is responsible for numerous hospitalizations and deaths every year. Among the adaptations that enable the survival of Listeria in the environment are the abilities to persist in biofilms, grow in the cold, and

  2. Modelling the growth of Listeria monocytogenes on the surface of smear- or mould-ripened cheese

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    Sol eSchvartzman

    2014-07-01

    Full Text Available Surface-ripened cheeses are matured by means of manual or mechanical technologies posing a risk of cross-contamination, if any cheeses are contaminated with Listeria monocytogenes. In predictive microbiology, primary models are used to describe microbial responses, such as growth rate over time and secondary models explain how those responses change with environmental factors. In this way, primary models were used to assess the growth rate of L. monocytogenes during ripening of the cheeses and the secondary models to test how much the growth rate was affected by either the pH and/or the water activity (aw of the cheeses. The two models combined can be used to predict outcomes. The purpose of these experiments was to test three primary (the modified Gompertz equation, the Baranyi and Roberts model and the Logistic model and three secondary (the Cardinal model, the Ratowski model and the Presser model mathematical models in order to define which combination of models would best predict the growth of L. monocytogenes on the surface of artificially contaminated surface-ripened cheeses. Growth on the surface of the cheese was assessed and modelled. The primary models were firstly fitted to the data and the effects of pH and aw on the growth rate (μmax were incorporated and assessed one by one with the secondary models. The Logistic primary model by itself did not show a better fit of the data among the other primary models tested, but the inclusion of the Cardinal secondary model improved the final fit. The aw was not related to the growth of Listeria. This study suggests that surface-ripened cheese should be separately regulated within EU microbiological food legislation and results expressed as counts per surface area rather than per gram.

  3. Modeling the growth of Listeria monocytogenes on the surface of smear- or mold-ripened cheese.

    Science.gov (United States)

    Schvartzman, M Sol; Gonzalez-Barron, Ursula; Butler, Francis; Jordan, Kieran

    2014-01-01

    Surface-ripened cheeses are matured by means of manual or mechanical technologies posing a risk of cross-contamination, if any cheeses are contaminated with Listeria monocytogenes. In predictive microbiology, primary models are used to describe microbial responses, such as growth rate over time and secondary models explain how those responses change with environmental factors. In this way, primary models were used to assess the growth rate of L. monocytogenes during ripening of the cheeses and the secondary models to test how much the growth rate was affected by either the pH and/or the water activity (aw) of the cheeses. The two models combined can be used to predict outcomes. The purpose of these experiments was to test three primary (the modified Gompertz equation, the Baranyi and Roberts model, and the Logistic model) and three secondary (the Cardinal model, the Ratowski model, and the Presser model) mathematical models in order to define which combination of models would best predict the growth of L. monocytogenes on the surface of artificially contaminated surface-ripened cheeses. Growth on the surface of the cheese was assessed and modeled. The primary models were firstly fitted to the data and the effects of pH and aw on the growth rate (μmax) were incorporated and assessed one by one with the secondary models. The Logistic primary model by itself did not show a better fit of the data among the other primary models tested, but the inclusion of the Cardinal secondary model improved the final fit. The aw was not related to the growth of Listeria. This study suggests that surface-ripened cheese should be separately regulated within EU microbiological food legislation and results expressed as counts per surface area rather than per gram.

  4. Age-Dependent Differences in Systemic and Cell-Autonomous Immunity to L. monocytogenes

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    Ashley M. Sherrid

    2013-01-01

    Full Text Available Host defense against infection can broadly be categorized into systemic immunity and cell-autonomous immunity. Systemic immunity is crucial for all multicellular organisms, increasing in importance with increasing cellular complexity of the host. The systemic immune response to Listeria monocytogenes has been studied extensively in murine models; however, the clinical applicability of these findings to the human newborn remains incompletely understood. Furthermore, the ability to control infection at the level of an individual cell, known as “cell-autonomous immunity,” appears most relevant following infection with L. monocytogenes; as the main target, the monocyte is centrally important to innate as well as adaptive systemic immunity to listeriosis. We thus suggest that the overall increased risk to suffer and die from L. monocytogenes infection in the newborn period is a direct consequence of age-dependent differences in cell-autonomous immunity of the monocyte to L. monocytogenes. We here review what is known about age-dependent differences in systemic innate and adaptive as well as cell-autonomous immunity to infection with Listeria monocytogenes.

  5. A novel suicide plasmid for efficient gene mutation in Listeria monocytogenes

    Science.gov (United States)

    Although several plasmids have been used in Listeria monocytogenes for generating mutants by allelic exchange, construction of L. monocytogenes mutants has been inefficient due to lack of effective selection markers for first and second recombination events. To address this problem, we have develope...

  6. Inactivation of Listeria monocytogenes ATCC 7644 on tomatoes using sodium docecyl sulphate, levulinic acid and sodium hypochlorite solution

    Directory of Open Access Journals (Sweden)

    E. Mnyandu

    2015-06-01

    Full Text Available The human pathogen Listeria monocytogenes poses a serious threat to public health. A study was carried out to evaluate the effectiveness of four sanitizers, used individually or combined, against L. monocytogenes ATCC 7644. The contact times for bacteria and sanitizer were varied to 1, 3 and 5 minutes. Levulinic acid, sodium dodecyl sulphate (SDS, sodium hypochlorite solution (chlorine and a combination of SDS and levulinic acid (mixture were tested. Results revealed that 0.5% levulinic acid, when used individually, is capable of reducing the surviving colonies by 3.63 log CFU/mL, 4.05 log CFU/mL, 6.71 log CFU/mL after exposure for 1, 3 and 5 minutes respectively.SDS resulted in an 8 log CFU/mL reduction after 1, 3 and 5 minutes. A combination of 0.5% levulinic acid and 0.05% SDS caused a 3.69 log CFU /mL reduction, 4.4 log CFU/mL reduction, 7.97 log CFU/mL reduction for 1, 3 and 5 minutes respectively. Chlorine was the least effective with 2.93 log CFU/mL reduction, 3.16 log CFU/ mL reduction and 4.53 log CFU/ mL reduction respectively. When stored for up to 72 hours at 4°C, the surviving colonies remained viable and decreased in number significantly P < 0.05 = 0.001. The titratable acidity of samples treated with levulinic acid and samples treated with SDS/Lev mixture was lowered significantly compared to the control sample. No significant differences were noted in these same parameters for samples treated with chlorine or SDS. The application of SDS in the fresh produce industry as a sanitizing agent may be successful in eradicating or reducing the viability of L. monocytogenes on fresh produce, thereby replacing the routine chlorine washing.

  7. Assessment of Listeria monocytogenes virulence in the Galleria mellonella insect larvae model.

    Science.gov (United States)

    Rakic Martinez, Mira; Wiedmann, Martin; Ferguson, Martine; Datta, Atin R

    2017-01-01

    Several animal models have been used to understand the molecular basis of the pathogenicity, infectious dose and strain to strain variation of Listeria monocytogenes. The greater wax worm Galleria mellonella, as an alternative model, provides some useful advantages not available with other models and has already been described as suitable for the virulence assessment of various pathogens including L. monocytogenes. The objectives of this study are: 1) confirming the usefulness of this model with a wide panel of Listeria spp. including non-pathogenic L. innocua, L. seeligeri, L. welshimeri and animal pathogen L. ivanovii; 2) assessment of virulence of several isogenic in-frame deletion mutants in virulence and stress related genes of L. monocytogenes and 3) virulence assessment of paired food and clinical isolates of L. monocytogenes from 14 major listeriosis outbreaks occurred worldwide between 1980 and 2015. Larvae injected with different concentrations of Listeria were incubated at 37°C and monitored over seven days for time needed to kill 50% of larvae (LT50) and to determine change of bacterial population in G. mellonella, 2 and 24 hours post-inoculation. Non-pathogenic members of Listeria and L. ivanovii showed significantly (P monocytogenes strains. Isogenic mutants of L. monocytogenes with the deletions in prfA, plcA, hly, actA and virR genes, also showed significantly (P monocytogenes strains related to non-invasive (gastroenteritis) outbreaks of listeriosis showed significantly (P < 0.05) lower virulence than isolates of the same serotype obtained from outbreaks with invasive symptoms. The difference, however, was dose and strain- dependent. No significant differences in virulence were observed among the serotype tested in this study.

  8. Lactobacillus plantarum inhibits growth of Listeria monocytogenes in an in vitro continuous flow gut model, but promotes invasion of L. monocytogenes in the gut of gnotobiotic rats

    DEFF Research Database (Denmark)

    Bernbom, Nete; Licht, Tine Rask; Saadbye, Peter

    2006-01-01

    The ability of the pediocin AcH producing Lactobacillus plantarum DDEN 11007 and its non-producing plasmid-cured isogenic variant, DDEN 12305 to prevent the persistence and growth of Listeria monocytogenes EP2 in two gastrointestinal (GI) tract models was examined. In vitro studies conducted...... in a two-stage continuous flow system showed that L. plantarum DDEN 11007 inhibited L. monocytogenes EP2 under these conditions, while less effect was seen of the non-bacteriocin producing variant. The inhibitory effect was more pronounced at pH 5 than at pH 7. No effect on persistence of L. monocytogenes...... in the GI tract was seen in gnotobiotic rats colonized with either the pediocin AcH producing or the non-bacteriocin producing variant of L. plantarum when compared to rats inoculated with L. monocytogenes EP2 alone. Surprisingly, inoculation of the gnotobiotic animals with either of the L. plantarum...

  9. Effect of eugenol on growth and listeriolysin o production by Listeria monocytogenes

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    Cristina Tostes Filgueiras

    2006-05-01

    Full Text Available The inhibitory effect of eugenol, a naturally occurring compound mainly present in the essential oil fraction of cloves, was studied on the growth and listeriolysin O (LLO production by Listeria monocytogenes. Potassium efflux from cells promoted by eugenol was also determined after 24 h incubation in phosphate buffered saline. Eugenol promoted a delay on the growth of L. monocytogenes at concentrations of 100, 300 and 500 µg mL-1and above 800 µg mL-1 the effect was bactericidal. Production of LLO by L. monocytogenes in the presence of eugenol was reduced 80-100%. An accumulation of external K+ was observed above 300 µg mL-1 of eugenol which indicated that the cell membrane was affected. The results showed the effectiveness of eugenol in controlling growth and LLO production of L. monocytogenes cells.O efeito inibitório do eugenol, o principal constituinte do óleo essencial de cravo, foi avaliado sobre o crescimento e produção de listeriolisina O (LLO por Listeria monocytogenes. O efluxo de íons potássio das células também foi determinado após 24 h de incubação em solução tampão, contendo eugenol. Concentrações de 100, 300 e 500 µg mL-1 de eugenol promoveram a inibição do crescimento de L. monocytogenes e, em concentrações acima de 800 µg mL-1, constatou-se um efeito bactericida. O crescimento de L. monocytogenes na presença de eugenol resultou na inibição de 80 a 100% da produção de LLO. O efluxo de K+ promovido pelo eugenol indicou que a membrana celular foi afetada. Estes resultados indicam a efetividade do eugenol para o controle do crescimento e da produção de LLO por L. monocytogenes.

  10. Prevalence and contamination patterns of Listeria monocytogenes in catfish processing environment and fresh fillets.

    Science.gov (United States)

    Chen, Bang-Yuan; Pyla, Rajkumar; Kim, Tae-Jo; Silva, Juan L; Jung, Yean-Sung

    2010-08-01

    Catfish skins, intestines, fresh fillets, processing surfaces at different production stages, chiller water and non-food contact surfaces were sampled for Listeria monocytogenes and other Listeria species. Among 315 samples, prevalence of L. monocytogenes, Listeria innocua and a group of Listeria seeligeri-Listeria welshimeri-Listeria ivanovii was 21.6, 13.0 and 29.5%, respectively. No Listeria grayi was detected in this survey. While no L. monocytogenes strains were isolated from catfish skins and intestines, the strains were found with a frequency of 76.7% in chilled fresh catfish fillets and 43.3% in unchilled fillets. L. monocytogenes and Listeria spp. were also detected in fish contact surfaces such as deheading machine, trimming board, chiller water, conveyor belts at different stages, and fillet weighing table. Among L. monocytogenes, 1/2b (47.0%), 3b (16.0%) and 4c (14%) were the predominant serotypes isolated, whereas 4b, 4e, 1/2c and 1/2a were detected at much lower frequencies. Genotype analyses of L. monocytogenes isolates using serotyping, pulsed-field gel electrophoresis (PFGE) and enterobacterial repetitive intergenic consensus (ERIC)-PCR revealed that chiller water represented an important contamination source of L. monocytogenes in the chilled catfish fillets of two processing facilities, whereas fillet weighing table significantly contributed to the catfish fillet contamination of the third facility. This study suggests that L. monocytogenes contamination in the processed catfish fillets originates from the processing environment, rather than directly from catfish. Results from this study can aid the catfish industry to develop a plant-specific proper cleaning and sanitation procedure for equipment and the processing environment designed to specifically target L. monocytogenes contamination. Copyright 2010 Elsevier Ltd. All rights reserved.

  11. Comparison of susceptibility to antibiotics of Staphylococcus aureus isolated from fresh cheeses and clinical samples from the Area Metropolitana and evaluation of the presence of Listeria monocytogenes in the same foodstuff

    International Nuclear Information System (INIS)

    Piedra Ramirez, Hiryna

    2014-01-01

    60 samples of fresh cheeses were analyzed from the central markets of Alajuela, Heredia, Cartago and San Jose. Staphylococcus aureus, total coliform and thermotolerant counts were performed, as well as Escherichia coli by the NMP technique. The presence of Listeria monocytogenes was evaluated in 25 g of cheese. The confirmatory identification and sensitivity profile of S. aureus strains were obtained using the Vitek system. L. monocytogenes were identified by means of biochemical tests. The statistical package Statistical Package for the Social Sciences (SPSS) and Excell were used to analyze the data. The presence of fecal contamination was identified as well as S. aureus in fresh cheeses from the four provinces studied. The comparative analysis of S. aureus antibiotic susceptibility profiles from clinical specimens and cheeses, for the majority of antibiotics under study was able to determine that the sensitivity patterns shown have been different. The clinical strains of origin could be observed with a pattern of multiresistance more marked than the strains of alimentary origin. The presence of L. monocytogenes was identified in an important percentage of cheese samples. (author) [es

  12. A multiplex PCR for detection of Listeria monocytogenes and its lineages.

    Science.gov (United States)

    Rawool, Deepak B; Doijad, Swapnil P; Poharkar, Krupali V; Negi, Mamta; Kale, Satyajit B; Malik, S V S; Kurkure, Nitin V; Chakraborty, Trinad; Barbuddhe, Sukhadeo B

    2016-11-01

    A novel multiplex PCR assay was developed to identify genus Listeria, and discriminate Listeria monocytogenes and its major lineages (LI, LII, LIII). This assay is a rapid and inexpensive subtyping method for screening and characterization of L. monocytogenes. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Industrial disinfectants do not select for resistance in Listeria monocytogenes following long term exposure

    DEFF Research Database (Denmark)

    Kastbjerg, Vicky Gaedt; Gram, Lone

    2012-01-01

    or tolerance would evolve in L. monocytogenes under continued selection in three industrial disinfectants. L. monocytogenes EGD was exposed to Desinfect CL (hypochlorite) and Incimaxx DES (peracedic acid and hydrogen peroxide) for several hundred generations. This caused no increase in the minimal inhibitory......, and that the disinfectants are still efficient for controlling microorganisms such as L. monocytogenes....

  14. Control of Listeria monocytogenes in turkey deli loaves using organic acids as formulation ingredients.

    Science.gov (United States)

    Lloyd, T; Alvarado, C Z; Brashears, M M; Thompson, L D; McKee, S R; Berrang, M

    2009-10-01

    The growth of Listeria monocytogenes in further-processed meat products has become a major concern and an important food safety issue. The meat and poultry industries have incorporated interventions such as organic acids in marinades to inhibit the growth of L. monocytogenes. In this study, organic acids were utilized in the raw product and as a postcook dip to determine their inhibitory effect on the growth of L. monocytogenes in turkey deli loaves. The turkey deli loaves were processed, cooked, cooled, inoculated with streptomycin-resistant L. monocytogenes, and then dipped. Treatments were potassium lactate (PL) in the raw product with sodium lactate (SL), sodium diacetate (SD) dip, PL with SL/PL/SD dip, SL with SL/SD dip, and SL with SL/PL/SD dip. There was also a positive (inoculated) and negative (noninoculated) control, which was dipped in distilled water. Days 0, 7, 14, 21, 28, 42, and 56 were sampled for L. monocytogenes. There were no differences (P>0.05) among the organic acid treatments in the turkey deli loaves at any time points; therefore, all of the treatments increased the lag phase of L. monocytogenes, extending the shelf-life of the product. However, there was a difference between the treatments and the positive control at d 7, 14, 21, 28, 42, and 56. The growth of L. monocytogenes increased immediately in the positive control, whereas the negative control appeared to have no growth. These organic acids can provide meat processors with a useful method for extending the lag phase of L. monocytogenes in ready-to-eat meat and poultry products.

  15. L. monocytogenes in a cheese processing facility: Learning from contamination scenarios over three years of sampling.

    Science.gov (United States)

    Rückerl, I; Muhterem-Uyar, M; Muri-Klinger, S; Wagner, K-H; Wagner, M; Stessl, B

    2014-10-17

    The aim of this study was to analyze the changing patterns of Listeria monocytogenes contamination in a cheese processing facility manufacturing a wide range of ready-to-eat products. Characterization of L. monocytogenes isolates included genotyping by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Disinfectant-susceptibility tests and the assessment of L. monocytogenes survival in fresh cheese were also conducted. During the sampling period between 2010 and 2013, a total of 1284 environmental samples were investigated. Overall occurrence rates of Listeria spp. and L. monocytogenes were 21.9% and 19.5%, respectively. Identical L. monocytogenes genotypes were found in the food processing environment (FPE), raw materials and in products. Interventions after the sampling events changed contamination scenarios substantially. The high diversity of globally, widely distributed L. monocytogenes genotypes was reduced by identifying the major sources of contamination. Although susceptible to a broad range of disinfectants and cleaners, one dominant L. monocytogenes sequence type (ST) 5 could not be eradicated from drains and floors. Significantly, intense humidity and steam could be observed in all rooms and water residues were visible on floors due to increased cleaning strategies. This could explain the high L. monocytogenes contamination of the FPE (drains, shoes and floors) throughout the study (15.8%). The outcome of a challenge experiment in fresh cheese showed that L. monocytogenes could survive after 14days of storage at insufficient cooling temperatures (8 and 16°C). All efforts to reduce L. monocytogenes environmental contamination eventually led to a transition from dynamic to stable contamination scenarios. Consequently, implementation of systematic environmental monitoring via in-house systems should either aim for total avoidance of FPE colonization, or emphasize a first reduction of L. monocytogenes to sites where

  16. Metabolic responses of primary and transformed cells to intracellular Listeria monocytogenes.

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    Nadine Gillmaier

    Full Text Available The metabolic response of host cells, in particular of primary mammalian cells, to bacterial infections is poorly understood. Here, we compare the carbon metabolism of primary mouse macrophages and of established J774A.1 cells upon Listeria monocytogenes infection using (13C-labelled glucose or glutamine as carbon tracers. The (13C-profiles of protein-derived amino acids from labelled host cells and intracellular L. monocytogenes identified active metabolic pathways in the different cell types. In the primary cells, infection with live L. monocytogenes increased glycolytic activity and enhanced flux of pyruvate into the TCA cycle via pyruvate dehydrogenase and pyruvate carboxylase, while in J774A.1 cells the already high glycolytic and glutaminolytic activities hardly changed upon infection. The carbon metabolism of intracellular L. monocytogenes was similar in both host cells. Taken together, the data suggest that efficient listerial replication in the cytosol of the host cells mainly depends on the glycolytic activity of the hosts.

  17. [Risk assessment of Listeria monocytogenes in deli meats and vegetable salads].

    Science.gov (United States)

    Tian, Jing; Liu, Xiu-mei

    2009-09-01

    To analysis risk from Listeria monocytogenes in deli meats and vegetable salads. Use Risk Ranger which is a software programme developed by the University of Hobart, Australia and answer 11 questions on affecting the risk from hazards in the specific foods by combining data from national foodborne diseases surveillance network and some references to make semi-quantitative risk assessment for the specific food. Relative risk from Listeria monocytogenes in deli meats and vegetable salads is 61 and 52, respectively. Incidence of listeriosis caused by deli meats-Listeria monocytogenes pairs and vegetable salads-Listeria monocytogenes pairs is 5.4 and 0.2 cases per million people, respectively. Risk from the former is 32 times than that from the latter. By changing the selection for some risk factors in the model, it was known that the risks from two food-hazard combinations could decrease 10 times, if taking necessary actions after processing. Deli meats is a kind of high risk food for listeriosis.

  18. Listeria monocytogenes meningitis in the elderly: epidemiological, clinical and therapeutic findings.

    Science.gov (United States)

    Pagliano, Pasquale; Ascione, Tiziana; Boccia, Giovanni; De Caro, Francesco; Esposito, Silvano

    2016-06-01

    Listeria monocytogenes is a Gram-positive bacillus and facultative intracellular bacterium whose transmission occurs mainly through the consumption of contaminated food, L. monocytogenes invades the host cells using various protein and can escape to the human T-cell immune system by cell-to-cell spreading. If the infection is not controlled at the stage in which the bacterium is in the liver, for instance, due to a severe immunodepression, a secondary bacteraemia can be developed and L. monocytogenes reaches the preferred sites transgressing the blood-brain barrier or the placental barrier. Individuals with T-cell dysfunction, such as pregnant women, the elderly, and those receiving immunosuppressive therapy are at the highest risk of contracting the disease. Average life expectancy throughout developed countries has rapidly increased during the latter half of the 20th century and geriatric infectious diseases have become an increasingly important issue. L. monocytogenes meningitis in young previously healthy adults has been reported only in anecdotal observations. Differently, L. monocytogenes is the third most common cause of bacterial meningitis in the elderly population, after Streptococcus pneumoniae and Neisseria meningitidis. Patients with L. monocytogenes meningitis presented with signs and symptoms that were similar to those of the general population with community-acquired bacterial meningitis, but reported a longer prodromal phase. According to literature data, the prevalence of the classic triad of fever, neck stiffness, and altered mental status is 43%, and almost all patients present with at least 2 of the 4 classic symptoms of headache, fever, neck stiffness, and altered mental status. On the basis of our published data, in patients aged over 50 years, diagnosing L. monocytogenes meningitis was more challenging than pneumococcal meningitis, as demonstrated by the lower percentage of cases receiving a correct diagnosis within 48 hours from the onset

  19. Occurrence of Listeria monocytogenes in cheese and ice cream produced in the State of Paraná, Brazil Ocorrência de Listeria monocytogenes em queijos e sorvetes produzidos no Estado do Paraná, Brasil

    Directory of Open Access Journals (Sweden)

    Wanda Moscalewski Abrahão

    2008-06-01

    Full Text Available The occurrence of Listeria monocytogenes in Brazilian ice cream and in some soft and semi-soft cheeses produced and sold in the State of Paraná, Brazil was evaluated. Ninety samples of cheese and sixty samples of ice creams were analyzed following the guidelines outlined by the official institutes, AOAC and FDA. In the ice cream samples no isolation of Listeria spp. was found. The percentage of these ninety samples of cheeses positive for Listeria spp. was 12.20%. Listeria monocytogenes was detected in six (6.70% of the same samples. The presence of Listeria innocua was five (5.50% in the samples analyzed was also observed. According to the results of the work it is possible to presume that there is a potential health risk to the brazilian population, heightened by aging and the increase in immunodepressed. These results indicate the need for the implementation of monitoring of these microorganisms as much by producers as by health inspectors. The results also show that the VIP (visual immunoprecipitation assay is a viable triage method of contaminated samples for the liberation of products for commercialization, as it is quick, reliable and does not require additional equipment other than that normally found in production labs, while presenting reliable results.A ocorrência de Listeria monocytogenes em sorvetes e alguns tipos de queijos macios e semi-macios produzidos e vendidos no Estado do Paraná Brasil foram avaliados. Noventa amostras de queijo e sessenta amostras de sorvete foram analisadas seguindo os protocolos da AOAC e FDA. Nas amostras de sorvete, não ocorreu o isolamento de Listeria spp. Foi detectada Listeria spp em 12,20% de amostras de queijo, das quais 6 (6,70% foram positivas para Listeria monocytogenes. Foi também observada a presença de Listeria innocua em 5 amostras (5,50% das mesmas amostras. Pelos resultados deste trabalho pode-se pressupor que existe um risco potencial à saúde da população brasileira com o

  20. Recombinant phage probes for Listeria monocytogenes

    Energy Technology Data Exchange (ETDEWEB)

    Carnazza, S; Gioffre, G; Felici, F; Guglielmino, S [Department of Microbiological, Genetic and Molecular Sciences, University of Messina, Messina (Italy)

    2007-10-03

    Monitoring of food and environmental samples for biological threats, such as Listeria monocytogenes, requires probes that specifically bind biological agents and ensure their immediate and efficient detection. There is a need for robust and inexpensive affinity probes as an alternative to antibodies. These probes may be recruited from random peptide libraries displayed on filamentous phage. In this study, we selected from two phage peptide libraries phage clones displaying peptides capable of specific and strong binding to the L. monocytogenes cell surface. The ability of isolated phage clones to interact specifically with L. monocytogenes was demonstrated using enzyme-linked immunosorbent assay (ELISA) and confirmed by co-precipitation assay. We also assessed the sensitivity of phage-bacteria binding by PCR on phage-captured Listeria cells, which could be detected at a concentration of 10{sup 4} cells ml{sup -1}. In addition, as proof-of-concept, we tested the possibility of immobilizing the affinity-selected phages to a putative biosensor surface. The quality of phage deposition was monitored by ELISA and fluorescent microscopy. Phage-bacterial binding was confirmed by high power optical phase contrast microscopy. Overall, the results of this work validate the concept of affinity-selected recombinant filamentous phages as probes for detecting and monitoring bacterial agents under any conditions that warrant their recognition, including in food products.

  1. Frequency of contamination Listeria monocytogenes of raw dried cured vacuum packed sausages

    Directory of Open Access Journals (Sweden)

    Hristo Daskalov

    2014-03-01

    Full Text Available The aim of this study was to collect actual data concerning the frequency of contamination with Listeria monocytogenes of some very popular in Bulgaria raw dried cured vacuum packed sausages, produced from October 2004 till May 2008. 148 vacuum-packed samples were taken from 9 different food business operators during all seasons of the year. The samples were analyzed according to USDA method for meat foods. Ten specimens were positive for presence of Listeria monocytogenes equal to 6,75% of all tested samples. In two other raw dried cured sausages L.welshimeri and L.innocua were found, but these species are not pathogenic for consumers. In the period before the official implementation of HACCP system (01.01.2006 in Bulgaria, 52 samples were examined and 5 Listeria monocytogenes isolates were found (~10%. 2,5 years after the HACCP implementation, 96 specimens from the same meat factories were tested and 5 Listeria monocytogenes isolates (5,2% were detected. Samples taken from lots, produced in winter time were contaminated with Listeria monocytogenes more often (7 of all 10 than specimens taken during other seasons. Data were discussed through the point of view of the effectiveness of hygienic practices and HACCP system application. Also, application of ‘microbiological criterion’ set in COMMISSION REGULATION (EC No 2073/2005 for ready-to-eat foods unable to support the growth of L. monocytogenes was considered.

  2. An insight into the isolation, enumeration and molecular detection of Listeria monocytogenes in food

    Directory of Open Access Journals (Sweden)

    Jodi Woan-Fei Law

    2015-11-01

    Full Text Available Listeria monocytogenes, a foodborne pathogen that can cause listeriosis through the consumption of food contaminated with this pathogen. The ability of L. monocytogenes to survive in extreme conditions and cause food contaminations have become a major concern. Hence, routine microbiological food testing is necessary to prevent food contamination and outbreaks of foodborne illness. This review provides insight into the methods for cultural detection, enumeration and molecular identification of L. monocytogenes in various food samples. There are a number of enrichment and plating media that can be used for the isolation of L. monocytogenes from food samples. Enrichment media such as buffered Listeria Enrichment Broth (BLEB, Fraser broth and University of Vermont Medium (UVM Listeria enrichment broth are recommended by regulatory agencies such as FDA-BAM, USDA-FSIS and ISO. Many plating media are available for the isolation of L. monocytogenes, for instance, PALCAM, Oxford and other chromogenic media. Besides, reference methods like FDA-BAM, ISO 11290 method and USDA-FSIS method are usually applied for the cultural detection or enumeration of L. monocytogenes. MPN technique is applied for the enumeration of L. monocytogenes in the case of low level contamination. Molecular methods including polymerase chain reaction (PCR, multiplex polymerase chain reaction (mPCR, real-time/quantitative polymerase chain reaction (qPCR, nucleic acid sequence-based amplification (NASBA, loop-mediated isothermal amplification (LAMP, DNA microarray and Next Generation Sequencing (NGS technology for the detection and identification of L. monocytogenes are discussed in this review. Overall, molecular methods are rapid, sensitive, specific, time- and labour-saving. In future, there are chances for the development of new techniques for the detection and identification of foodborne with improved features.

  3. Incidence of Listeria monocytogenes and Listeria spp. in a small-scale mushroom production facility.

    Science.gov (United States)

    Viswanath, Prema; Murugesan, Latha; Knabel, Stephen J; Verghese, Bindhu; Chikthimmah, Naveen; Laborde, Luke F

    2013-04-01

    Listeria monocytogenes is a foodborne pathogen of significant concern to the agricultural and food processing industry because of its ability to grow and persist in cool and moist environments and its association with listeriosis, a disease with a very high mortality rate. Although there have been no listeriosis outbreaks attributed to fresh mushrooms in the United States, retail surveys and recalls are evidence that L. monocytogenes contamination of mushrooms (Agaricus bisporus) can occur. The objective of this study was to determine the prevalence of Listeria spp., including L. monocytogenes, in a small-scale mushroom production facility on the campus of the Pennsylvania State University in the United States. Of 184 samples taken from five production zones within the facility, 29 (15.8%) samples were positive for Listeria spp. Among the Listeria spp. isolates, L. innocua was most prevalent (10.3%) followed by L. welshimeri (3.3%), L. monocytogenes (1.6%), and L. grayi (0.5%). L. monocytogenes was recovered only from the phase I raw material composting area. Isolates of L. monocytogenes were confirmed and serotyped by multiplex PCR. The epidemiological relatedness of the three L. monocytogenes isolates to those serotypes or lineages frequently encountered in listeriosis infections was determined by multi-virulence-locus sequence typing using six virulence genes, namely, prfA, inlB, inlC, dal, clpP, and lisR. The phylogenetic positions of the three isolates in the dendrogram prepared with data from other isolates of L. monocytogenes showed that all isolates were grouped with serotype 4a, lineage IIIA. To date, this serotype has rarely been reported in foodborne disease outbreaks.

  4. An ecological perspective of Listeria monocytogenes biofilms in food processing facilities.

    Science.gov (United States)

    Valderrama, Wladir B; Cutter, Catherine N

    2013-01-01

    Listeria monocytogenes can enter the food chain at virtually any point. However, food processing environments seem to be of particular importance. From an ecological point of view, food processing facilities are microbial habitats that are constantly disturbed by cleaning and sanitizing procedures. Although L. monocytogenes is considered ubiquitous in nature, it is important to recognize that not all L. monocytogenes strains appear to be equally distributed; the distribution of the organism seems to be related to certain habitats. Currently, no direct evidence exists that L. monocytogenes-associated biofilms have played a role in food contamination or foodborne outbreaks, likely because biofilm isolation and identification are not part of an outbreak investigation, or the definition of biofilm is unclear. Because L. monocytogenes is known to colonize surfaces, we suggest that contamination patterns may be studied in the context of how biofilm formation is influenced by the environment within food processing facilities. In this review, direct and indirect epidemiological and phenotypic evidence of lineage-related biofilm formation capacity to specific ecological niches will be discussed. A critical view on the development of the biofilm concept, focused on the practical implications, strengths, and weaknesses of the current definitions also is discussed. The idea that biofilm formation may be an alternative surrogate for microbial fitness is proposed. Furthermore, current research on the influence of environmental factors on biofilm formation is discussed.

  5. Real-time monitoring of non-viable airborne particles correlates with airborne colonies and represents an acceptable surrogate for daily assessment of cell-processing cleanroom performance.

    Science.gov (United States)

    Raval, Jay S; Koch, Eileen; Donnenberg, Albert D

    2012-10-01

    Airborne particulate monitoring is mandated as a component of good manufacturing practice. We present a procedure developed to monitor and interpret airborne particulates in an International Organization for Standardization (ISO) class 7 cleanroom used for the cell processing of Section 351 and Section 361 products. We collected paired viable and non-viable airborne particle data over a period of 1 year in locations chosen to provide a range of air quality. We used receiver operator characteristic (ROC) analysis to determine empirically the relationship between non-viable and viable airborne particle counts. Viable and non-viable particles were well-correlated (r(2) = 0.78), with outlier observations at the low end of the scale (non-viable particles without detectable airborne colonies). ROC analysis predicted viable counts ≥ 0.5/feet(3) (a limit set by the United States Pharmacopeia) at an action limit of ≥ 32 000 particles (≥ 0.5 µ)/feet(3), with 95.6% sensitivity and 50% specificity. This limit was exceeded 2.6 times during 18 months of retrospective daily cleanroom data (an expected false alarm rate of 1.3 times/year). After implementing this action limit, we were alerted in real time to an air-handling failure undetected by our hospital facilities management. A rational action limit for non-viable particles was determined based on the correlation with airborne colonies. Reaching or exceeding the action limit of 32 000 non-viable particles/feet(3) triggers suspension of cleanroom cell-processing activities, deep cleaning, investigation of air handling, and a deviation management process. Our full procedure for particle monitoring is available as an online supplement.

  6. Evaluation of DNA extraction methods for PCR-based detection of Listeria monocytogenes from vegetables.

    Science.gov (United States)

    Vojkovska, H; Kubikova, I; Kralik, P

    2015-03-01

    Epidemiological data indicate that raw vegetables are associated with outbreaks of Listeria monocytogenes. Therefore, there is a demand for the availability of rapid and sensitive methods, such as PCR assays, for the detection and accurate discrimination of L. monocytogenes. However, the efficiency of PCR methods can be negatively affected by inhibitory compounds commonly found in vegetable matrices that may cause false-negative results. Therefore, the sample processing and DNA isolation steps must be carefully evaluated prior to the introduction of such methods into routine practice. In this study, we compared the ability of three column-based and four magnetic bead-based commercial DNA isolation kits to extract DNA of the model micro-organism L. monocytogenes from raw vegetables. The DNA isolation efficiency of all isolation kits was determined using a triplex real-time qPCR assay designed to specifically detect L. monocytogenes. The kit with best performance, the PowerSoil(™) Microbial DNA Isolation Kit, is suitable for the extraction of amplifiable DNA from L. monocytogenes cells in vegetable with efficiencies ranging between 29.6 and 70.3%. Coupled with the triplex real-time qPCR assay, this DNA isolation kit is applicable to the samples with bacterial loads of 10(3) bacterial cells per gram of L. monocytogenes. Several recent outbreaks of Listeria monocytogenes have been associated with the consumption of fruits and vegetables. Real-time PCR assays allow fast detection and accurate quantification of microbes. However, the success of real-time PCR is dependent on the success with which template DNA can be extracted. The results of this study suggest that the PowerSoil(™) Microbial DNA Isolation Kit can be used for the extraction of amplifiable DNA from L. monocytogenes cells in vegetable with efficiencies ranging between 29.6 and 70.3%. This method is applicable to samples with bacterial loads of 10(3) bacterial cells per gram of L. monocytogenes. © 2014

  7. In vitro activity of naturally occurring peptides (defensins against Listeria monocytogenes Ação in vitro de peptídeos naturais (defensinas sobre Listeria monocytogenes

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    Maria da Graça F. Nascimento

    1994-12-01

    Full Text Available Autoclaved distilled water samples were inoculated with L. monocytogenes strain V7 and strain VPH-1, and incubated aerobically, at 30 C for 48 hours. Each strain was tested individually, and growth curves were determined at 1, 2, 3, 4, 5, 21, 24, and 48 hours. The growth or survival of L. monocytogenes was similar for both strains, with survivors at 24 hour-incubation. The microbicidal activity of one synthetic cationic peptide (NP-2 was examined against L. monocytogenes strain V7, in a water system. Antibacterial activity of NP-2 (1, 5, and 10 g/ml was best expressed at 60 minute-incubation, with 10 g/ml of peptide, at 30 C.Amostras de água destilada, autoclavadas, foram inoculadas com L. monocytogenes cepa V7 e cepa VPH-1, e incubadas, aerobicamente, a 30ºC por 48 horas. Cada cepa foi testada individualmente, e determinou-se curvas de crescimento a 1, 2, 3, 4, 5, 21, 24, e 48 horas. O crescimento ou sobrevivência das duas cepas foi semelhante e encontrou-se sobreviventes em 24 horas de incubação. Examinou-se a atividade bactericida de um dos peptídeos catiônicos sintéticos (NP-2 contra L. monocytogenes cepa V7, em sistema aquoso. A atividade antibacteriana de NP-2 (1, 5, and 10µg/ml foi melhor aos 60 minutos de incubação, com 10µg/ml de peptídeo, a 30 C.

  8. Prevalence and Persistence of Listeria monocytogenes in Ready-to-Eat Tilapia Sashimi Processing Plants.

    Science.gov (United States)

    Chen, Bang-Yuan; Wang, Chung-Yi; Wang, Chia-Lan; Fan, Yang-Chi; Weng, I-Ting; Chou, Chung-Hsi

    2016-11-01

    A 2-year study was performed at two ready-to-eat tilapia sashimi processing plants (A and B) to identify possible routes of contamination with Listeria monocytogenes during processing. Samples were collected from the aquaculture environments, transportation tanks, processing plants, and final products. Seventy-nine L. monocytogenes isolates were found in the processing environments and final products; 3.96% (50 of 1,264 samples) and 3.86% (29 of 752 samples) of the samples from plants A and B, respectively, were positive for L. monocytogenes . No L. monocytogenes was detected in the aquaculture environments or transportation tanks. The predominant L. monocytogenes serotypes were 1/2b (55.70%) and 4b (37.97%); serotypes 3b and 4e were detected at much lower percentages. At both plants, most processing sections were contaminated with L. monocytogenes before the start of processing, which indicated that the cleaning and sanitizing methods did not achieve adequate pathogen removal. Eleven seropulsotypes were revealed by pulsed-field gel electrophoresis and serotyping. Analysis of seropulsotype distribution revealed that the contamination was disseminated by the processing work; the same seropulsotypes were repeatedly found along the work flow line and in the final products. Specific seropulsotypes were persistently found during different sampling periods, which suggests that the sanitation procedures or equipment used at these plants were inadequate. Plant staff should improve the sanitation procedures and equipment to reduce the risk of L. monocytogenes cross-contamination and ensure the safety of ready-to-eat tilapia products.

  9. Prevalence and antimicrobial resistance of Listeria monocytogenes isolated in chicken slaughterhouses in Northern Greece.

    Science.gov (United States)

    Sakaridis, I; Soultos, N; Iossifidou, E; Papa, A; Ambrosiadis, I; Koidis, P

    2011-06-01

    This study was conducted to determine the prevalence and antimicrobial resistance of Listeria monocytogenes recovered from chicken carcasses in slaughterhouses in Northern Greece. A total of 100 poultry samples (300 carcasses) were examined for Listeria spp. The samples were neck skin taken from four different slaughterhouses in Northern Greece. Forty samples were also taken from the environment of the slaughterhouses. Identification of L. monocytogenes was carried out by PCR and fingerprinting of the isolates by random amplified polymorphic DNA. L. monocytogenes strains isolated from chicken carcasses and from the environment of the slaughterhouses were also examined for antibiotic resistance. Fifty-five isolates of L. monocytogenes were tested for susceptibility to 20 antibiotics using the disk diffusion method. Listeria spp. were present in 99 of the poultry samples tested (99%), and 38 yielded L monocytogenes (38%). L. monocytogenes was also isolated in 80% of samples from the environment of a certain slaughterhouse, while the other slaughterhouses were found to be contaminated only with Listeria spp. All isolates were resistant to nalidixic acid and oxolinic acid, the majority of them to clindamycin, and only a few to tetracycline and oxytetracycline, whereas they were found to be susceptible to all other antimicrobials. The results of this study demonstrate a high prevalence of L. monocytogenes contamination in chicken carcasses, and all isolates were found to be sensitive to the antimicrobials most commonly used to treat human listeriosis.

  10. Listeria monocytogenes response regulators important for stress tolerance and pathogenesis

    DEFF Research Database (Denmark)

    Kallipolitis, B H; Ingmer, H

    2001-01-01

    Environmental sensing by two-component signal transduction systems is likely to play a role for growth and survival of Listeria monocytogenes both during transmission in food products and within a host organism. Two-component systems typically consist of a membrane-associated sensor histidine...... kinase and a gene regulatory protein, the response regulator (RR). We have identified seven putative RR genes in L. monocytogenes LO28 by PCR using degenerate oligonucleotide primers. By insertional inactivation we obtained data suggesting that three of the putative RRs contribute to the pathogenicity...... of L. monocytogenes in mice. Strikingly, the mutants that were attenuated in virulence also had a decreased ability to grow in the presence of various stress conditions potentially encountered in an infection process. Thus, our data point to a connection between the ability of the putative two...

  11. Mechanism of Nisin, Pediocin 34, and Enterocin FH99 Resistance in Listeria monocytogenes.

    Science.gov (United States)

    Kaur, Gurpreet; Singh, Tejinder Pal; Malik, Ravinder Kumar; Bhardwaj, Arun

    2012-03-01

    Nisin-, pediocin 34-, and enterocin FH99-resistant variants of Listeria monocytogenes ATCC 53135 were developed. In an attempt to clarify the possible mechanisms underlying bacteriocin resistance in L. monocytogenes ATCC 53135, sensitivity of the resistant strains of L. monocytogenes ATCC 53135 to nisin, pediocin 34, and enterocin FH99 in the absence and presence of different divalent cations was assessed, and the results showed that the addition of divalent cations significantly reduced the inhibitory activity of nisin, pediocin 34, and enterocin FH99 against resistant variants of L. monocytogenes ATCC 53135. The addition of EDTA, however, restored this activity suggesting that the divalent cations seem to affect the initial electrostatic interaction between the positively charged bacteriocin and the negatively charged phospholipids of the membrane. Nisin-, pediocin 34-, and enterocin-resistant variants of L. monocytogenes ATCC 53135 were more resistant to lysozyme as compared to the wild-type strain both in the presence as well as absence of nisin, pediocin 34, and enterocin FH99. Ultra structural profiles of bacteriocin-sensitive L. monocytogenes and its bacteriocin-resistant counterparts revealed that the cells of wild-type strain of L. monocytogenes were maximally in pairs or short chains, whereas, its nisin-, pediocin 34-, and enterocin FH99-resistant variants tend to form aggregates. Results indicated that without a cell wall, the acquired nisin, pediocin 34, and enterocin FH99 resistance of the variants was lost. Although the bacteriocin-resistant variants appeared to lose their acquired resistance toward nisin, pediocin 34, and enterocin FH99, the protoplasts of the resistant variants appeared to be more resistant to bacteriocins than the protoplasts of their wild-type counterparts.

  12. Performance of Isfahan North Wastewater Treatment Plant in the Removal of Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    nahid Navijouy

    2013-08-01

    Full Text Available Listeria and in particular Listeria monocytogenes is considered a ubiquitous foodborne pathogen which can lead listeriosis in human and animals. Listeriosis can be serious and may cause meningitis, septicemia and abortion in pregnant women. Although wastewater or sludge may contaminate foods of plant origin, there are no data on occurrence of Listeria spp. in wastewater and sludge in Iran. The purpose of current investigation was to study the occurrence of Listeria spp. in various samples of wastewater and sludge in Isfahan North wastewater treatment plant. Influent, effluent, raw sludge and dried sludge samples were collected from Isfahan North municipal wastewater treatment plant. L. monocytogenes were enumerated by a three–tube most probable number (MPN assay using enrichment Fraser broth. A total of 65 various samples from five step in 13 visits were collected. The presence of Listeria spp. also was determined using USDA procedure. Then, phenotypically identified L. monocytogenes were further confirmed by Polymerase Chain Reaction amplification. L. monocytogenes isolated from 76.9%, 38.5%, 84.6%, 69.2% and 46.2% of influent, effluent, raw sludge, stabilized sludge and dried sludge respectively. The efficiency of wastewater treatment processes, digester tank and drying bed in removal L. monocytogenes were 69.6%, 64.7% and 73.4% respectively. All phenotypically identified L. monocytogenes were further confirmed by Polymerase Chain Reaction. The results of present study have shown that Listeriaspp. and L. monocytogenes in particular, were present in wastewater treatment plant effluents and sludge at high level. The bacteria may spread on agriculture land and contaminate foods of plant origin. This may cause a risk of spreading disease to human and animals.

  13. Novel Biocontrol Methods for Listeria monocytogenes Biofilms in Food Production Facilities.

    Science.gov (United States)

    Gray, Jessica A; Chandry, P Scott; Kaur, Mandeep; Kocharunchitt, Chawalit; Bowman, John P; Fox, Edward M

    2018-01-01

    High mortality and hospitalization rates have seen Listeria monocytogenes as a foodborne pathogen of public health importance for many years and of particular concern for high-risk population groups. Food manufactures face an ongoing challenge in preventing the entry of L. monocytogenes into food production environments (FPEs) due to its ubiquitous nature. In addition to this, the capacity of L. monocytogenes strains to colonize FPEs can lead to repeated identification of L. monocytogenes in FPE surveillance. The contamination of food products requiring product recall presents large economic burden to industry and is further exacerbated by damage to the brand. Poor equipment design, facility layout, and worn or damaged equipment can result in Listeria hotspots and biofilms where traditional cleaning and disinfecting procedures may be inadequate. Novel biocontrol methods may offer FPEs effective means to help improve control of L. monocytogenes and decrease cross contamination of food. Bacteriophages have been used as a medical treatment for many years for their ability to infect and lyse specific bacteria. Endolysins, the hydrolytic enzymes of bacteriophages responsible for breaking the cell wall of Gram-positive bacteria, are being explored as a biocontrol method for food preservation and in nanotechnology and medical applications. Antibacterial proteins known as bacteriocins have been used as alternatives to antibiotics for biopreservation and food product shelf life extension. Essential oils are natural antimicrobials formed by plants and have been used as food additives and preservatives for many years and more recently as a method to prevent food spoilage by microorganisms. Competitive exclusion occurs naturally among bacteria in the environment. However, intentionally selecting and applying bacteria to effect competitive exclusion of food borne pathogens has potential as a biocontrol application. This review discusses these novel biocontrol methods and their

  14. A dynamical systems approach to actin-based motility in Listeria monocytogenes

    Science.gov (United States)

    Hotton, S.

    2010-11-01

    A simple kinematic model for the trajectories of Listeria monocytogenes is generalized to a dynamical system rich enough to exhibit the resonant Hopf bifurcation structure of excitable media and simple enough to be studied geometrically. It is shown how L. monocytogenes trajectories and meandering spiral waves are organized by the same type of attracting set.

  15. On-Chip Dielectrophoretic Separation and Concentration of Viable, Non-Viable and Viable but Not Culturable (VBNC) Escherichia coli

    Energy Technology Data Exchange (ETDEWEB)

    Packard, M M; Shusteff, M; Alocilja, E C

    2012-04-12

    Although bacterial culture remains the gold standard for detection of viable bacteria in environmental specimens, the typical time requirement of twenty-four hours can delay and even jeopardize appropriate public health intervention. In addition, culture is incapable of detecting viable but not culturable (VBNC) species. Conversely, nucleic acid and antibody-based methods greatly decrease time to detection but rarely characterize viability of the bacteria detected. Through selection by membrane permeability, the method described in this work employs positive dielectrophoresis (pDEP) for separation and purification of viable and VBNC species from water and allows concentration of bacteria for downstream applications.

  16. Longitudinal monitoring of Listeria monocytogenes and Listeria phages in seafood processing environments in Thailand.

    Science.gov (United States)

    Vongkamjan, Kitiya; Benjakul, Soottawat; Kim Vu, Hue Thi; Vuddhakul, Varaporn

    2017-09-01

    Listeria monocytogenes is a foodborne pathogen commonly found in environments of seafood processing, thus presenting a challenge for eradication from seafood processing facilities. Monitoring the prevalence and subtype diversity of L. monocytogenes together with phages that are specific to Listeria spp. ("Listeria phages") will provide knowledge on the bacteria-phage ecology in food processing plants. In this work, a total of 595 samples were collected from raw material, finished seafood products and environmental samples from different sites of a seafood processing plant during 17 sampling visits in 1.5 years of study. L. monocytogenes and Listeria spp. (non-monocytogenes) were found in 22 (3.7%) and 43 (7.2%) samples, respectively, whereas 29 Listeria phages were isolated from 9 (1.5%) phage-positive samples. DNA fingerprint analysis of L. monocytogenes isolates revealed 11 Random Amplified Polymorphic DNA (RAPD) profiles, with two subtypes were frequently observed over time. Our data reveal a presence of Listeria phages within the same seafood processing environments where a diverse set of L. monocytogenes subtypes was also found. Although serotype 4b was observed at lower frequency, data indicate that isolates from this seafood processing plant belonged to both epidemiologically important serotypes 1/2a and 4b, which may suggest a potential public health risk. Phages (all showed a unique genome size of 65 ± 2 kb) were classified into 9 host range groups, representing both broad- and narrow-host range. While most L. monocytogenes isolates from this facility were susceptible to phages, five isolates showed resistance to 12-20 phages. Variations in phage host range among Listeria phages isolated from food processing plant may affect a presence of a diverse set of L. monocytogenes isolates derived from the same processing environment in Thailand. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. An insight into the isolation, enumeration, and molecular detection of Listeria monocytogenes in food

    Science.gov (United States)

    Law, Jodi Woan-Fei; Ab Mutalib, Nurul-Syakima; Chan, Kok-Gan; Lee, Learn-Han

    2015-01-01

    Listeria monocytogenes, a foodborne pathogen that can cause listeriosis through the consumption of food contaminated with this pathogen. The ability of L. monocytogenes to survive in extreme conditions and cause food contaminations have become a major concern. Hence, routine microbiological food testing is necessary to prevent food contamination and outbreaks of foodborne illness. This review provides insight into the methods for cultural detection, enumeration, and molecular identification of L. monocytogenes in various food samples. There are a number of enrichment and plating media that can be used for the isolation of L. monocytogenes from food samples. Enrichment media such as buffered Listeria enrichment broth, Fraser broth, and University of Vermont Medium (UVM) Listeria enrichment broth are recommended by regulatory agencies such as Food and Drug Administration-bacteriological and analytical method (FDA-BAM), US Department of Agriculture-Food and Safety (USDA-FSIS), and International Organization for Standardization (ISO). Many plating media are available for the isolation of L. monocytogenes, for instance, polymyxin acriflavin lithium-chloride ceftazidime aesculin mannitol, Oxford, and other chromogenic media. Besides, reference methods like FDA-BAM, ISO 11290 method, and USDA-FSIS method are usually applied for the cultural detection or enumeration of L. monocytogenes. most probable number technique is applied for the enumeration of L. monocytogenes in the case of low level contamination. Molecular methods including polymerase chain reaction, multiplex polymerase chain reaction, real-time/quantitative polymerase chain reaction, nucleic acid sequence-based amplification, loop-mediated isothermal amplification, DNA microarray, and next generation sequencing technology for the detection and identification of L. monocytogenes are discussed in this review. Overall, molecular methods are rapid, sensitive, specific, time- and labor-saving. In future, there are

  18. MicroRNA-146a Deficiency Protects against Listeria monocytogenes Infection by Modulating the Gut Microbiota

    Directory of Open Access Journals (Sweden)

    Chong-Tao Du

    2018-03-01

    Full Text Available The gut microbiota and microRNAs play important roles in the defense against infection. However, the role of miR-146a in L. monocytogenes infection and gut microbiota remains unclear. We tried to determine whether miR-146a controlled L. monocytogenes infection by regulating the gut microbiota. Wild-type and miR-146a-deficient mice or macrophages were used to characterize the impact of miR-146a on animal survival, cell death, bacterial clearance, and gut microbiota following L. monocytogenes challenge. We found that L. monocytogenes infection induced miR-146a expression both in vitro and in vivo. When compared to wild-type mice, miR-146a-deficient mice were more resistant to L. monocytogenes infection. MiR-146a deficiency in macrophages resulted in reduced invasion and intracellular survival of L. monocytogenes. High-throughput sequencing of 16S rRNA revealed that the gut microbiota composition differed between miR-146a-deficient and wild-type mice. Relative to wild-type mice, miR-146a-deficient mice had decreased levels of the Proteobacteria phylum, Prevotellaceae family, and Parasutterella genus, and significantly increased short-chain fatty acid producing bacteria, including the genera Alistipes, Blautia, Coprococcus_1, and Ruminococcus_1. Wild-type mice co-housed with miR-146a-deficient mice had increased resistance to L. monocytogenes, indicating that miR-146a deficiency guides the gut microbiota to alleviate infection. Together, these results suggest that miR-146a deficiency protects against L. monocytogenes infection by regulating the gut microbiota.

  19. MicroRNA-146a Deficiency Protects against Listeria monocytogenes Infection by Modulating the Gut Microbiota.

    Science.gov (United States)

    Du, Chong-Tao; Gao, Wei; Ma, Ke; Yu, Shui-Xing; Li, Na; Yan, Shi-Qing; Zhou, Feng-Hua; Liu, Zhen-Zhen; Chen, Wei; Lei, Lian-Cheng; Yang, Yong-Jun; Han, Wen-Yu

    2018-03-26

    The gut microbiota and microRNAs play important roles in the defense against infection. However, the role of miR-146a in L. monocytogenes infection and gut microbiota remains unclear. We tried to determine whether miR-146a controlled L. monocytogenes infection by regulating the gut microbiota. Wild-type and miR-146a-deficient mice or macrophages were used to characterize the impact of miR-146a on animal survival, cell death, bacterial clearance, and gut microbiota following L. monocytogenes challenge. We found that L. monocytogenes infection induced miR-146a expression both in vitro and in vivo. When compared to wild-type mice, miR-146a-deficient mice were more resistant to L. monocytogenes infection. MiR-146a deficiency in macrophages resulted in reduced invasion and intracellular survival of L. monocytogenes . High-throughput sequencing of 16S rRNA revealed that the gut microbiota composition differed between miR-146a-deficient and wild-type mice. Relative to wild-type mice, miR-146a-deficient mice had decreased levels of the Proteobacteria phylum, Prevotellaceae family, and Parasutterella genus, and significantly increased short-chain fatty acid producing bacteria, including the genera Alistipes , Blautia , Coprococcus_1, and Ruminococcus_1 . Wild-type mice co-housed with miR-146a-deficient mice had increased resistance to L. monocytogenes , indicating that miR-146a deficiency guides the gut microbiota to alleviate infection. Together, these results suggest that miR-146a deficiency protects against L. monocytogenes infection by regulating the gut microbiota.

  20. Microbial counts of food contact surfaces at schools depending on a feeding scheme

    Directory of Open Access Journals (Sweden)

    Nthabiseng Nhlapo

    2014-11-01

    Full Text Available The prominence of disease transmission between individuals in confined environments is a concern, particularly in the educational environment. With respect to school feeding schemes, food contact surfaces have been shown to be potential vehicles of foodborne pathogens. The aim of this study was to assess the cleanliness of the surfaces that come into contact with food that is provided to children through the National School Nutrition Programme in central South Africa. In each school under study, microbiological samples were collected from the preparation surface and the dominant hand and apron of the food handler. The samples were analysed for total viable counts, coliforms, Escherichia coli, Staphylococcus aureus and yeasts and moulds. The criteria specified in the British Columbia Guide for Environmental Health Officers were used to evaluate the results. Total viable counts were high for all surfaces, with the majority of colonies being too numerous to count (over 100 colonies per plate. Counts of organisms were relatively low, with 20% of the surfaces producing unsatisfactory enumeration of S. aureus and E. coli and 30% unsatisfactory for coliforms. Yeast and mould produced 50% and 60% unsatisfactory counts from preparation surfaces and aprons, respectively. Statistically significant differences could not be established amongst microbial counts of the surfaces, which suggests cross-contamination may have occurred. Contamination may be attributed to foodstuffs and animals in the vicinity of the preparation area rather than to the food handlers, because hands had the lowest counts of enumerated organisms amongst the analysed surfaces.

  1. Inhibitory activity of Syzygium aromaticum and Cymbopogon citratus (DC.) Stapf. essential oils against Listeria monocytogenes inoculated in bovine ground meat.

    Science.gov (United States)

    de Oliveira, Thales Leandro Coutinho; das Graças Cardoso, Maria; de Araújo Soares, Rodrigo; Ramos, Eduardo Mendes; Piccoli, Roberta Hilsdorf; Tebaldi, Victor Maximiliano Reis

    2013-01-01

    This research evaluated the antimicrobial effect of the clove (Syzygium aromaticum) and lemongrass (Cymbopogon citratus (DC.) Stapf.) essential oils (EOs) against Listeria monocytogenes ATCC 19117 growth added to bovine ground meat stored under refrigeration (5 ± 2 °C) for three days. The EOs, extracted by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS), were tested in vitro using an agar well diffusion methodology for determination of Minimum Inhibitory Concentration (MIC). The MIC concentrations for both essential oils on culture tested of L. monocytogenes were 1.56%. The EOs concentrations applied in contaminated ground beef were 1.56, 3.125 and 6.25% (w/v) based on MIC levels and possible activity reductions by food constituents. The bacteria populations were significantly reduced (p ≤ 0.05) after one day of storage in ground meat samples treated with clove and lemongrass EOs at concentrations of 1.56%. There were no significant counts of L. monocytogenes in samples at the other concentrations of the two oils applied after the second day of storage. The sensory acceptability evaluation of the bovine ground meat samples treated with EOs showed that the addition at concentrations higher than 1.56% promote undesirable alterations of taste, odor and characteristic color. The application of EOs at low concentrations in food products can be used in combination with other preservation methods, such as refrigeration, to control pathogens and spoilage bacteria during shelf-life; which goes according to current market trends, where consumers are requesting natural products.

  2. Inhibitory activity of Syzygium aromaticum and Cymbopogon citratus (DC. Stapf. essential oils against Listeria monocytogenes inoculated in bovine ground meat

    Directory of Open Access Journals (Sweden)

    Thales Leandro Coutinho de Oliveira

    2013-01-01

    Full Text Available This research evaluated the antimicrobial effect of the clove (Syzygium aromaticum and lemongrass (Cymbopogon citratus (DC. Stapf. essential oils (EOs against Listeria monocytogenes ATCC 19117 growth added to bovine ground meat stored under refrigeration (5 ± 2 °C for three days. The EOs, extracted by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS, were tested in vitro using an agar well diffusion methodology for determination of Minimum Inhibitory Concentration (MIC. The MIC concentrations for both essential oils on culture tested of L. monocytogenes were 1.56%. The EOs concentrations applied in contaminated ground beef were 1.56, 3.125 and 6.25% (w/v based on MIC levels and possible activity reductions by food constituents. The bacteria populations were significantly reduced (p < 0.05 after one day of storage in ground meat samples treated with clove and lemongrass EOs at concentrations of 1.56%. There were no significant counts of L. monocytogenes in samples at the other concentrations of the two oils applied after the second day of storage. The sensory acceptability evaluation of the bovine ground meat samples treated with EOs showed that the addition at concentrations higher than 1.56% promote undesirable alterations of taste, odor and characteristic color. The application of EOs at low concentrations in food products can be used in combination with other preservation methods, such as refrigeration, to control pathogens and spoilage bacteria during shelf-life; which goes according to current market trends, where consumers are requesting natural products.

  3. Assessment of Listeria monocytogenes virulence in the Galleria mellonella insect larvae model.

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    Mira Rakic Martinez

    Full Text Available Several animal models have been used to understand the molecular basis of the pathogenicity, infectious dose and strain to strain variation of Listeria monocytogenes. The greater wax worm Galleria mellonella, as an alternative model, provides some useful advantages not available with other models and has already been described as suitable for the virulence assessment of various pathogens including L. monocytogenes. The objectives of this study are: 1 confirming the usefulness of this model with a wide panel of Listeria spp. including non-pathogenic L. innocua, L. seeligeri, L. welshimeri and animal pathogen L. ivanovii; 2 assessment of virulence of several isogenic in-frame deletion mutants in virulence and stress related genes of L. monocytogenes and 3 virulence assessment of paired food and clinical isolates of L. monocytogenes from 14 major listeriosis outbreaks occurred worldwide between 1980 and 2015. Larvae injected with different concentrations of Listeria were incubated at 37°C and monitored over seven days for time needed to kill 50% of larvae (LT50 and to determine change of bacterial population in G. mellonella, 2 and 24 hours post-inoculation. Non-pathogenic members of Listeria and L. ivanovii showed significantly (P < 0.05 higher LT50 (lower virulence than the wild type L. monocytogenes strains. Isogenic mutants of L. monocytogenes with the deletions in prfA, plcA, hly, actA and virR genes, also showed significantly (P < 0.05 higher LT50 than the wild type strain at the inoculum of 106CFU/larva. Food isolates had significantly (P < 0.05 lower virulence than the paired clinical isolates, at all three inoculum concentrations. L. monocytogenes strains related to non-invasive (gastroenteritis outbreaks of listeriosis showed significantly (P < 0.05 lower virulence than isolates of the same serotype obtained from outbreaks with invasive symptoms. The difference, however, was dose and strain- dependent. No significant differences in

  4. Listeria monocytogenes serotype prevalence and biodiversity in diverse food products.

    Science.gov (United States)

    Hadjilouka, Agni; Andritsos, Nikolaos D; Paramithiotis, Spiros; Mataragas, Marios; Drosinos, Eleftherios H

    2014-12-01

    The aim of this study was to assess serotype prevalence and biodiversity of Listeria monocytogenes strains isolated from diverse food products, i.e., minced pork, fruits, and vegetables. Three hundred twenty-six samples previously purchased from supermarkets and street markets within the Athens area were studied for L. monocytogenes prevalence. A total of 121 strains were isolated from the 36 samples that were positive for L. monocytogenes. Serotyping was performed with multiplex PCR, and biodiversity was assessed with random amplified polymorphic DNA (RAPD) PCR analysis using M13, UBC155, and HLWL85 as primers and with repetitive element palindromic (rep) PCR analysis using (GTG)5 as the primer. The majority (17 of 22) of the contaminated minced pork samples contained strains identified as serotype 1/2a, either alone or in combination with strains belonging to serotypes 1/2b, 4a, 4c, or 4ab. However, all L. monocytogenes isolates from fruits and vegetables belonged to serotype 4b. Rep-PCR provided better differentiation of the isolates than did RAPD PCR and resulted in discrimination of the isolates into a larger number of unique profiles. Complete differentiation was achieved only with the combination of these subtyping techniques.

  5. COMPARISON OF TWO METHODS FOR THE DETECTION OF LISTERIA MONOCYTOGENES

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    G. Tantillo

    2013-02-01

    Full Text Available The aim of this study was to compare the performance of the conventional methods for detection of Listeria monocytogenes in food using media Oxford and ALOA (Agar Listeria acc. to Ottaviani & Agosti in according to the ISO 11290-1 to a new chromogenic medium “CHROMagar Listeria” standardized in 2005 AFNOR ( CHR – 21/1-12/01. A total of 40 pre-packed ready-to-eat food samples were examined. Using two methods six samples were found positive for Listeria monocytogenes but the medium “CHROMagar Listeria” was more selective in comparison with the others. In conclusion this study has demonstrated that isolation medium able to target specifically the detection of L. monocytogenes such as “CHROMagar Listeria” is highly recommendable because of that detection time is significantly reduced and the analysis cost is less expensive.

  6. Role of Extracellular DNA during Biofilm Formation by Listeria monocytogenes

    DEFF Research Database (Denmark)

    Harmsen, Morten; Lappann, Martin; Knøchel, S

    2010-01-01

    (eDNA) may be the only central component of the biofilm matrix and that it is necessary for both initial attachment and early biofilm formation for 41 L. monocytogenes strains that were tested. DNase I treatment resulted in dispersal of biofilms, not only in microtiter tray assays but also in flow......Listeria monocytogenes is a food-borne pathogen that is capable of living in harsh environments. It is believed to do this by forming biofilms, which are surface-associated multicellular structures encased in a self-produced matrix. In this paper we show that in L. monocytogenes extracellular DNA...... cell biofilm assays. However, it was also demonstrated that in a culture without eDNA, neither Listeria genomic DNA nor salmon sperm DNA by itself could restore the capacity to adhere. A search for additional necessary components revealed that peptidoglycan (PG), specifically N-acetylglucosamine (NAG...

  7. Phenotypic and Genotypic Characteristics of Listeria monocytogenes Isolated From Dairy and Meat Products

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    Bahador

    2015-08-01

    Full Text Available Background Listeria monocytogenes is a foodborne pathogen and a serious threat to the public health in the world. Consumption of traditional foods such as dairy and meat products can be a major reason for relative abundance and isolation of these bacteria. Objectives The purpose of this study was to determine the phenotypic and genotypic characteristics of L. monocytogenes strains isolated from dairy and meat products. Materials and Methods A total of 317 dairy products and meat-processed samples were collected. Antibiotic susceptibility test was performed on each sample by the disk diffusion method (Kirby Bauer. Five reference loci were used for typing of L. monocytogenes strains by MLVA (Multiple Locus VNTR Analysis Technique. Results A total of 24 L. monocytogenes isolates were collected from the dairy and meat products. Resistance of isolated L. monocytogenes strains to penicillin G were 54.54% (from dairy products and 46.15% (from processed meat. Genetic relatedness of isolates were assessed by MLVA. Out of 13 different types, type 2 with 6 strains and type 3 with 4 strains, were the most common types. Conclusions MLVA analysis showed that samples obtained from different sources could have similar genetic profile. As a result, administration of penicillin in patients with listeriosis (especially pregnant women and antibiotic susceptibility test are recommended. The fast and accurate methods such as MLVA for tracking of pollution sources of L. monocytogenes are recommended during outbreaks.

  8. Antimicrobial activity of chitosan coatings and films against Listeria monocytogenes on black radish.

    Science.gov (United States)

    Jovanović, Gordana D; Klaus, Anita S; Nikšić, Miomir P

    2016-01-01

    The antibacterial activity of chitosan coatings prepared with acetic or lactic acid, as well as of composite chitosan-gelatin films prepared with essential oils, was evaluated in fresh shredded black radish samples inoculated with Listeria monocytogenes ATCC 19115 and L. monocytogenes ATCC 19112 during seven days of storage at 4°C. The chitosan coating prepared with acetic acid showed the most effective antibacterial activity. All tested formulations of chitosan films exhibited strong antimicrobial activity on the growth of L. monocytogenes on black radish, although a higher inhibition of pathogens was achieved at higher concentrations of chitosan. The antimicrobial effect of chitosan films was even more pronounced with the addition of essential oils. Chitosan-gelatin films with thyme essential oils showed the most effective antimicrobial activity. A reduction of 2.4log10CFU/g for L. monocytogenes ATCC 19115 and 2.1log10CFU/g for L. monocytogenes ATCC 19112 was achieved in the presence of 1% chitosan film containing 0.2% of thyme essential oil after 24h of storage. Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

  9. Lineage specific recombination rates and microevolution in Listeria monocytogenes

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    Nightingale Kendra K

    2008-10-01

    Full Text Available Abstract Background The bacterium Listeria monocytogenes is a saprotroph as well as an opportunistic human foodborne pathogen, which has previously been shown to consist of at least two widespread lineages (termed lineages I and II and an uncommon lineage (lineage III. While some L. monocytogenes strains show evidence for considerable diversification by homologous recombination, our understanding of the contribution of recombination to L. monocytogenes evolution is still limited. We therefore used STRUCTURE and ClonalFrame, two programs that model the effect of recombination, to make inferences about the population structure and different aspects of the recombination process in L. monocytogenes. Analyses were performed using sequences for seven loci (including the house-keeping genes gap, prs, purM and ribC, the stress response gene sigB, and the virulence genes actA and inlA for 195 L. monocytogenes isolates. Results Sequence analyses with ClonalFrame and the Sawyer's test showed that recombination is more prevalent in lineage II than lineage I and is most frequent in two house-keeping genes (ribC and purM and the two virulence genes (actA and inlA. The relative occurrence of recombination versus point mutation is about six times higher in lineage II than in lineage I, which causes a higher genetic variability in lineage II. Unlike lineage I, lineage II represents a genetically heterogeneous population with a relatively high proportion (30% average of genetic material imported from external sources. Phylograms, constructed with correcting for recombination, as well as Tajima's D data suggest that both lineages I and II have suffered a population bottleneck. Conclusion Our study shows that evolutionary lineages within a single bacterial species can differ considerably in the relative contributions of recombination to genetic diversification. Accounting for recombination in phylogenetic studies is critical, and new evolutionary models that

  10. PRESERVATIVE POTENTIAL OF PURIFIED BACTERIOCIN PRODUCED FROM BREVIBACILLUS BORSTELENSIS AG1 ISOLATED FROM MARCHA – A TRADITIONAL WINE STARTER CULTURE CAKE IN TOMATO PASTE

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    Anupama Gupta

    2015-04-01

    Full Text Available Purified bacteriocin produced from Brevibacillus borstelensis AG1 isolated from Marcha a local wine starter herbal cake, was used to enhance the shelf life of tomato paste. Preservative effect of purified bacteriocin was studied for nine days in tomato paste inoculated with food borne pathogens and was compared to commercial biopreservative – nisin and chemical preservative – sodium benzoate. The indicator strains i.e. Listeria monocytogenes MTCC839, Bacillus subtilis CRI and Clostridium perfringens MTCC1739 were used at the amount 8.16, 8.13 and 8.18 log CFU/ml. Viable cells were counted periodically and a consistent reduction in number of viable cells of each tested pathogen was observed. It was found antagonistic against L. monocytogenes MTCC839, B. subtilis CRI and C. perfringes MTCC1739 which are the most challengeable and food borne pathogens found in processed vegetables products. Purified bacteriocin was found active over a wide pH range i.e. 3.0 to 11.0 and was able to withstand temperature up to 100oC. It showed a better preservative potential by reducing pathogenic load of the tested strains (by 2.02, 2.05 and 2.02 log cycles (CFU/ml of L. monocytogenes MTCC839, B. subtilis CRI and C. perfringes MTCC1739, respectively in tomato paste as compared to control (without bacteriocin. This proves efficiency of bacteriocin produced by B. borstelensis AG1 as biopreservative to enhance the safety and shelf life of acidic foods.

  11. Gross alpha/beta analyses in water by liquid scintillation counting

    International Nuclear Information System (INIS)

    Wong, C.T.; Lawrence Livermore National Laboratory, CA; Soliman, V.M.; Perera, S.K.

    2005-01-01

    The standard procedure for analyzing gross alpha and gross beta in water is evaporation of the sample and radioactivity determination of the resultant solids by proportional counting. This technique lacks precision, and lacks sensitivity for samples with high total dissolved solids. Additionally, the analytical results are dependent on the choice of radionuclide calibration standard and the sample matrix. Direct analysis by liquid scintillation counting has the advantages of high counting efficiencies and minimal sample preparation time. However, due to the small sample aliquants used for analysis, long count times are necessary to reach required detection limits. The procedure proposed consists of evaporating a sample aliquant to dryness, dissolving the resultant solids in a small volume of dilute acid, followed by liquid scintillation counting to determine radioactivity. This procedure can handle sample aliquants containing up to 500 mg of dissolved solids. Various acids, scintillation cocktail mixtures, instrument discriminator settings, and regions of interest (ROI) were evaluated to determine optimum counting conditions. Precision is improved and matrix effects are reduced as compared to proportional counting. Tests indicate that this is a viable alternative to proportional counting for gross alpha and gross beta analyses of water samples. (author)

  12. [Occurrence and typing of Listeria monocytogenes isolated from raw cow's milk collected on farms and from vending machines].

    Science.gov (United States)

    Gelbícová, T; Karpísková, R

    2012-04-01

    Evaluation of the incidence and characteristics of L. monocytogenes in samples of raw cow's milk collected on farms (bulk tank milk samples) and from vending machines. Detection of L. monocytogenes and enumeration were carried out according to EN/ISO 11290--1, 2. Strains were characterised by serotyping and macrorestriction analysis using pulsed-field gel electrophoresis. The presence of L. monocytogenes was detected in 3,2 % (11/346) of bulk tank milk samples and 1,8 % (4/219) samples of raw cow's milk from vending machines. Findings of L. monocytogenes in raw milk were sporadic. Only on one farm strains of L. monocytogenes were detected repeatedly. Thirteen strains of L. monocytogenes belonged to serotype 1/2a, two strains to serotype 1/2b and one to serotype 4b. Macrorestriction analysis revealed considerable heterogeinity of profiles, with nine different pulsotypes being detected. Pulsotype 711 was the most frequent. This pulsotype was found on three different farms. The incidence of L. monocytogenes in raw cow's milk is relatively low in the Czech Republic. The results confirmed that some clones of L. monocytogenes from raw milk are identical with food and human strains.

  13. In vitro detection of pathogenic Listeria monocytogenes from food sources by conventional, molecular and cell culture method

    Directory of Open Access Journals (Sweden)

    J.A. Khan

    2013-09-01

    Full Text Available Among current in vitro methods for identification of pathogenic Listeria monocytogenes (L. monocytogenes rely on growth in culture media, followed by isolation, and biochemical and serological identification. Now PCR (Polymerase Chain Reaction has been used for the rapid, sensitive and specific detection of pathogenic L. monocytogenes. The pathogenicity of the organism is highly correlated with haemolytic factor known as listeriolysin O (LLO. A total of 400 samples from meat and 250 samples from raw milk and their products were collected from various local dairy farms, dairy units and butcheries in Bareilly, India. Pure isolates of L. monocytogenes obtained after enrichment in Buffered Listeria enrichment broth (BLEB followed by plating onto Listeria oxford agar. The DNA extracted from pure isolates and used for the detection of bacterial pathogen. The oligonucleotide primer pairs (F: CGGAGGTTCCGCAAAAGATG; R: CCTCCAGAGTGATCGATGTT complementary to the nucleotide sequence of the hlyA gene selected for detection of L. monocytogenes using polymerase chain reaction (PCR. PCR products of 234 bp generated with DNA from all of L. monocytogenes isolates. The highest occurrence of haemolytic L. monocytogenes isolates from various meat samples was in raw chicken (6.0%, followed by fish meat (4.0%, and then beef (2.5%. Among various milk and milk products, curd (2.0% showed the highest prevalence, followed by raw milk (1.3%. The cytotoxic effects of haemolytic L. monocytogenes isolates were screened on vero cell lines. The cell lines with cell free culture supernatant (CFCS examined at 1 min, 10 min, 30 min, and 60 min. The significant changes in vero cells were observed at 30 min with both 30 µL and 50 µL of volume. We conclude that application of PCR approaches can provide critical information on distribution of haemolytic strains of L. monocytogenes in food processing environments. Vero cell cytotoxicity assay (in vitro resulted positive in twenty four

  14. Listeria monocytogenes and Listeria spp. contamination patterns in retail delicatessen establishments in three U.S. states.

    Science.gov (United States)

    Simmons, Courtenay; Stasiewicz, Matthew J; Wright, Emily; Warchocki, Steven; Roof, Sherry; Kause, Janell R; Bauer, Nathan; Ibrahim, Salam; Wiedmann, Martin; Oliver, Haley F

    2014-11-01

    Postprocessing contamination in processing plants has historically been a significant source of Listeria monocytogenes in ready-to-eat delicatessen meats, and therefore a major cause of human listeriosis cases and outbreaks. Recent risk assessments suggest that a majority of human listeriosis cases linked to consumption of contaminated deli meats may be due to L. monocytogenes contamination that occurs at the retail level. To better understand the ecology and transmission of Listeria spp. in retail delicatessens, food and nonfood contact surfaces were tested for L. monocytogenes and other Listeria spp. in a longitudinal study conducted in 30 retail delis in three U.S. states. In phase I of the study, seven sponge samples were collected monthly for 3 months in 15 delis (5 delis per state) prior to start of daily operation; in phase II, 28 food contact and nonfood contact sites were sampled in each of 30 delis during daily operation for 6 months. Among the 314 samples collected during phase I, 6.8% were positive for L. monocytogenes. Among 4,503 samples collected during phase II, 9.5% were positive for L. monocytogenes; 9 of 30 delis showed low L. monocytogenes prevalence (Listeria spp. isolates, including 184 Listeria innocua, 48 Listeria seeligeri, and 13 Listeria welshimeri were characterized. Pulsed-field gel electrophoresis (PFGE) was used to characterize 446 L. monocytogenes isolates. PFGE showed that for 12 of 30 delis, one or more PFGE types were isolated on at least three separate occasions, providing evidence for persistence of a given L. monocytogenes subtype in the delis. For some delis, PFGE patterns for isolates from nonfood contact surfaces were distinct from patterns for occasional food contact surface isolates, suggesting limited cross-contamination between these sites in some delis. This study provides longitudinal data on L. monocytogenes contamination patterns in retail delis, which should facilitate further development of control strategies in

  15. LACTIC FLORA-LISTERIA MONOCYTOGENES INTERACTION

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    S. Colombo

    2012-08-01

    Full Text Available The EC Regulation 2073/2005 (1 requires that food processors evaluate the capability of ready-to-use (RTE products to support the development of Listeria monocytogenes when their pH and aW values are favourable to the growth of this microorganism. It is renown that the lactic flora plays an important role in many different foods, both from a technological and a food safety standpoint. This study was aimed to observe the behaviour and the potential anti-Listeria effect of some natural lactic flora present in Italian liver patè crostini (chicken heart and liver, anchovies, onions, capers, starch, no added preservatives through the Combase Predictor – Max Growth Rate predictive software. The natural lactic flora of the crostini demonstrated a variable capability to inhibit the growth of Listeria monocytogenes which depends upon : the concentration of the lactic flora at the beginning of the shelf life period and the subsequent lag phase, the possible release of anti-Listeria substances, and the maximum growth rate.

  16. An outbreak of an unusual strain of Listeria monocytogenes infection in North-East Scotland

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    Emmanuel Okpo

    2015-11-01

    Full Text Available Summary: Listeria monocytogenes infection is an important cause of illness and hospitalization in vulnerable individuals. In the present study, we describe a community outbreak of Listeria monocytogenes in the North-East region of Scotland, which was epidemiologically, environmentally and microbiologically linked to a local meat product and ready-to-eat product manufacturer. Infected individuals were interviewed, and an environmental investigation was conducted. Clinical and environmental samples were tested by culture, and isolates were typed by fluorescent amplified fragment length polymorphism (fAFLP. Three cases of Listeria monocytogenes were linked geographically, had the same serotype (1/2a and were indistinguishable by fAFLP type XII.6. The human, food and environmental isolates were of the same serotype and were indistinguishable by molecular typing.This is the first community outbreak of L. monocytogenes reported in Scotland since the current outbreak surveillance was established in 1996. Epidemiological and laboratory evidence indicated poor hand hygiene, unhygienic practices and cross-contamination throughout the manufacturing process of ready-to-eat foods as a possible cause of the outbreak. More stringent control of commercial food establishments that provide ready-to-eat food and the need to advise specifically vulnerable groups, e.g., pregnant women, of the risk of L. monocytogenes in ready-to-eat food is urgently needed. Keywords: Listeria monocytogenes, Outbreak, Foodborne, Community acquired infection, Listeriosis

  17. Listeria monocytogenes inhibition by defatted mustard meal-based edible films.

    Science.gov (United States)

    Lee, Hahn-Bit; Noh, Bong Soo; Min, Sea C

    2012-02-01

    An antimicrobial edible film was developed from defatted mustard meal (Sinapis alba) (DMM), a byproduct from the bio-fuel industry, without incorporating external antimicrobials and its antimicrobial activity against Listeria monocytogenes and physical properties were investigated. The DMM colloidal solution consisting of 184 g water, 14 g DMM, and 2g glycerol was homogenized and incubated at 37°C for 0.2, 0.5, 24 or 48 h to prepare a film-forming solution. The pH of a portion of the film-forming solution (pH 5.5) was adjusted to 2.0 or 4.0. Films were formed by drying the film-forming solutions at 23°C for 48 h. The film-forming solution incubated for 48 h inhibited L. monocytogenes in broth and on agar media. Antimicrobial effects of the film prepared from the 48 h-incubated solution increased with decrease in pH of the solution from 5.5 to 2.0. The film from the film forming solution incubated for 48 h (pH 2.0) initially inhibited more than 4.0 log CFU/g of L. monocytogenes inoculated on film-coated salmon. The film-coating retarded the growth of L. monocytogenes in smoked salmon at 5, 10, and 15°C and the antimicrobial effect during storage was more noticeable when the coating was applied before inoculation than when it was applied after inoculation. The tensile strength, percentage elongation, solubility in watercxu, and water vapor permeability of the anti microbial film were 2.44 ± 0.19 MPa, 6.40 ± 1.13%, 3.19 ± 0.90%, and 3.18 ± 0.63 gmm/kPa hm(2), respectively. The antimicrobial DMM films have demonstrated a potential to be applied to foods as wraps or coatings to control the growth of L. monocytogenes. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Comparison of sodium hypochlorite-based foam and peroxyacetic acid-based fog sanitizing procedures in a salmon smokehouse: Survival of the general microflora and Listeria monocytogenes

    DEFF Research Database (Denmark)

    Bagge, Dorthe; Gardshodn, K.; Gram, Lone

    2003-01-01

    The effects of fog sanitization with peroxyacetic acid (hydrogen peroxide, peracetic acid, and acetic acid in combination) on general hygiene (aerobic plate count) and on Listeria monocytogenes were assessed in a slicing area at a salmon smokehouse and compared with the effects of foam sanitization...... sample, and a total of 288 bacterial strains were randomly isolated and tentatively identified to genus level by physiological and biochemical tests. The microflora was dominated by Neisseriaceae, Enterobacteriaceae, and lactic acid bacteria during production. Foam sanitization caused a change...

  19. Novel Biocontrol Methods for Listeria monocytogenes Biofilms in Food Production Facilities

    Directory of Open Access Journals (Sweden)

    Jessica A. Gray

    2018-04-01

    Full Text Available High mortality and hospitalization rates have seen Listeria monocytogenes as a foodborne pathogen of public health importance for many years and of particular concern for high-risk population groups. Food manufactures face an ongoing challenge in preventing the entry of L. monocytogenes into food production environments (FPEs due to its ubiquitous nature. In addition to this, the capacity of L. monocytogenes strains to colonize FPEs can lead to repeated identification of L. monocytogenes in FPE surveillance. The contamination of food products requiring product recall presents large economic burden to industry and is further exacerbated by damage to the brand. Poor equipment design, facility layout, and worn or damaged equipment can result in Listeria hotspots and biofilms where traditional cleaning and disinfecting procedures may be inadequate. Novel biocontrol methods may offer FPEs effective means to help improve control of L. monocytogenes and decrease cross contamination of food. Bacteriophages have been used as a medical treatment for many years for their ability to infect and lyse specific bacteria. Endolysins, the hydrolytic enzymes of bacteriophages responsible for breaking the cell wall of Gram-positive bacteria, are being explored as a biocontrol method for food preservation and in nanotechnology and medical applications. Antibacterial proteins known as bacteriocins have been used as alternatives to antibiotics for biopreservation and food product shelf life extension. Essential oils are natural antimicrobials formed by plants and have been used as food additives and preservatives for many years and more recently as a method to prevent food spoilage by microorganisms. Competitive exclusion occurs naturally among bacteria in the environment. However, intentionally selecting and applying bacteria to effect competitive exclusion of food borne pathogens has potential as a biocontrol application. This review discusses these novel biocontrol

  20. Novel Biocontrol Methods for Listeria monocytogenes Biofilms in Food Production Facilities

    Science.gov (United States)

    Gray, Jessica A.; Chandry, P. Scott; Kaur, Mandeep; Kocharunchitt, Chawalit; Bowman, John P.; Fox, Edward M.

    2018-01-01

    High mortality and hospitalization rates have seen Listeria monocytogenes as a foodborne pathogen of public health importance for many years and of particular concern for high-risk population groups. Food manufactures face an ongoing challenge in preventing the entry of L. monocytogenes into food production environments (FPEs) due to its ubiquitous nature. In addition to this, the capacity of L. monocytogenes strains to colonize FPEs can lead to repeated identification of L. monocytogenes in FPE surveillance. The contamination of food products requiring product recall presents large economic burden to industry and is further exacerbated by damage to the brand. Poor equipment design, facility layout, and worn or damaged equipment can result in Listeria hotspots and biofilms where traditional cleaning and disinfecting procedures may be inadequate. Novel biocontrol methods may offer FPEs effective means to help improve control of L. monocytogenes and decrease cross contamination of food. Bacteriophages have been used as a medical treatment for many years for their ability to infect and lyse specific bacteria. Endolysins, the hydrolytic enzymes of bacteriophages responsible for breaking the cell wall of Gram-positive bacteria, are being explored as a biocontrol method for food preservation and in nanotechnology and medical applications. Antibacterial proteins known as bacteriocins have been used as alternatives to antibiotics for biopreservation and food product shelf life extension. Essential oils are natural antimicrobials formed by plants and have been used as food additives and preservatives for many years and more recently as a method to prevent food spoilage by microorganisms. Competitive exclusion occurs naturally among bacteria in the environment. However, intentionally selecting and applying bacteria to effect competitive exclusion of food borne pathogens has potential as a biocontrol application. This review discusses these novel biocontrol methods and their

  1. Listeria monocytogenes : nog steeds een probleem?

    NARCIS (Netherlands)

    Beumer, R.R.

    2011-01-01

    Listeria monocytogenes is net als vele andere bacteriële voedselpathogenen al tientallen jaren bekend. De meeste grondstoffen voor voedingsmiddelen komen uit de akker- en tuinbouw, de veehouderij en de visserij. Besmetting vindt daar plaats met micro-organismen afkomstig uit grond, fecaliën, water,

  2. Growth characteristics of Listeria monocytogenes as affected by a native microflora in cooked ham under refrigerated and temperature abuse conditions.

    Science.gov (United States)

    Hwang, Cheng-An; Sheen, Shiowshuh

    2011-05-01

    This study examined the growth characteristics of Listeria monocytogenes as affected by a native microflora in cooked ham at refrigerated and abuse temperatures. A five-strain mixture of L. monocytogenes and a native microflora, consisting of Brochothrix spp., isolated from cooked meat were inoculated alone (monocultured) or co-inoculated (co-cultured) onto cooked ham slices. The growth characteristics, lag phase duration (LPD, h), growth rate (GR, log(10) cfu/h), and maximum population density (MPD, log(10) cfu/g), of L. monocytogenes and the native microflora in vacuum-packed ham slices stored at 4, 6, 8, 10, and 12 °C for up to 5 weeks were determined. At 4-12 °C, the LPDs of co-cultured L. monocytogenes were not significantly different from those of monocultured L. monocytogenes in ham, indicating the LPDs of L. monocytogenes at 4-12 °C were not influenced by the presence of the native microflora. At 4-8 °C, the GRs of co-cultured L. monocytogenes (0.0114-0.0130 log(10) cfu/h) were statistically but marginally lower than those of monocultured L. monocytogenes (0.0132-0.0145 log(10) cfu/h), indicating the GRs of L. monocytogenes at 4-8 °C were reduced by the presence of the native microflora. The GRs of L. monocytogenes were reduced by 8-7% with the presence of the native microflora at 4-8 °C, whereas there was less influence of the native microflora on the GRs of L. monocytogenes at 10 and 12 °C. The MPDs of L. monocytogenes at 4-8 °C were also reduced by the presence of the native microflora. Data from this study provide additional information regarding the growth suppression of L. monocytogenes by the native microflora for assessing the survival and growth of L. monocytogenes in ready-to-eat meat products. Published by Elsevier Ltd.

  3. Gamma irradiation as a means to eliminate Listeria monocytogenes from frozen chicken meat

    International Nuclear Information System (INIS)

    Kamat, A.S.; Nair, M.P.

    1995-01-01

    Cells of Listeria monocytogenes ATCC 35152 were sensitive to gamma irradiation in phosphate buffer, pH 7.00 (D 10 , dose required for 10% survival—0.15 kGy) at 0–5°C. The cells showed higher radiation survival when irradiated under frozen condition, with a D 10 of 0.3 kGy. The protection offered by shrimp/chicken/kheema homogenates (100 g litre−1) was evidenced by even higher D 10 values (0.5 kGy) at both 0–5°C and cryogenic temperature. Boneless chicken meat samples were artificially inoculated with L monocytogenes ATCC 35152 cells at low (5 × 10 3 ) colony-forming unit (cfu) g −1 and high (5 × 10 6 cfu g −1 ) concentrations and irradiated at 1, 3, 4, 6 kGy doses under cryogenic conditions. The efficacy of the radiation process was evaluated by detecting L monocytogenes during storage at 2–4°C in the irradiated samples. These studies, when repeated with three other serotypes of L monocytogenes, clearly suggested the need for a dose of 3 kGy for elimination of 10 3 cfu cells of L monocytogenes g −1 from air-packed frozen chicken meat. (author)

  4. How Listeria monocytogenes organizes its surface for virulence

    Science.gov (United States)

    Carvalho, Filipe; Sousa, Sandra; Cabanes, Didier

    2014-01-01

    Listeria monocytogenes is a Gram-positive pathogen responsible for the manifestation of human listeriosis, an opportunistic foodborne disease with an associated high mortality rate. The key to the pathogenesis of listeriosis is the capacity of this bacterium to trigger its internalization by non-phagocytic cells and to survive and even replicate within phagocytes. The arsenal of virulence proteins deployed by L. monocytogenes to successfully promote the invasion and infection of host cells has been progressively unveiled over the past decades. A large majority of them is located at the cell envelope, which provides an interface for the establishment of close interactions between these bacterial factors and their host targets. Along the multistep pathways carrying these virulence proteins from the inner side of the cytoplasmic membrane to their cell envelope destination, a multiplicity of auxiliary proteins must act on the immature polypeptides to ensure that they not only maturate into fully functional effectors but also are placed or guided to their correct position in the bacterial surface. As the major scaffold for surface proteins, the cell wall and its metabolism are critical elements in listerial virulence. Conversely, the crucial physical support and protection provided by this structure make it an ideal target for the host immune system. Therefore, mechanisms involving fine modifications of cell envelope components are activated by L. monocytogenes to render it less recognizable by the innate immunity sensors or more resistant to the activity of antimicrobial effectors. This review provides a state-of-the-art compilation of the mechanisms used by L. monocytogenes to organize its surface for virulence, with special focus on those proteins that work “behind the frontline”, either supporting virulence effectors or ensuring the survival of the bacterium within its host. PMID:24809022

  5. Encefalitis del tallo cerebral y mielitis por Listeria monocytogenes

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    Aracelly Castro

    2013-09-01

    Full Text Available La romboencefalitis por Listeria monocytogenes es una presentación poco común de la listeriosis del sistema nervioso central; sin embargo, es la presentación más común en personas inmunocompetentes. Aun más rara es la combinación de romboencefalitis con mielitis causada por L. monocytogenes; no obstante, en este artículo se reporta un caso de encefalitis del tallo y mielitis grave en un paciente sin compromiso del sistema inmunitario. Se presenta un paciente de 21 años de edad, sin deficiencias del sistema inmunitario, que consumió productos lácteos no pasteurizados y, posteriormente, presentó un cuadro de cefalea, vómito, deterioro de su estado general y, finalmente, alteración del estado de conciencia y muerte. Consultó al Instituto Neurológico de Colombia y se hizo diagnóstico de encefalitis del tallo y mielitis por L. monocytogenes. Se discuten las diferencias entre el caso presentado y los reportados en la literatura científica. Ante un paciente con signos de compromiso del tallo cerebral, de posible origen infeccioso, es prudente iniciar tratamiento antibiótico para L. monocytogenes y, en caso de poca respuesta, escalar rápidamente en dicho tratamiento. También lo es extender el estudio radiológico hacia la columna vertebral, con el fin de descartar compromiso de la médula espinal.   doi: http://dx.doi.org/10.7705/biomedica.v33i3.1482

  6. Survey for Listeria monocytogenes in and on Ready-to-Eat Foods from Retail Establishments in the United States (2010 through 2013): Assessing Potential Changes of Pathogen Prevalence and Levels in a Decade.

    Science.gov (United States)

    Luchansky, John B; Chen, Yuhuan; Porto-Fett, Anna C S; Pouillot, Régis; Shoyer, Bradley A; Johnson-DeRycke, Rachel; Eblen, Denise R; Hoelzer, Karin; Shaw, William K; van Doren, Jane M; Catlin, Michelle; Lee, Jeehyun; Tikekar, Rohan; Gallagher, Daniel; Lindsay, James A; Dennis, Sherri

    2017-06-01

    A multiyear interagency Listeria monocytogenes Market Basket Survey was undertaken for selected refrigerated ready-to-eat foods purchased at retail in four FoodNet sites in the United States. Food samples from 16 food categories in six broad groups (seafood, produce, dairy, meat, eggs, and combination foods) were collected weekly at large national chain supermarkets and independent grocery stores in California, Maryland, Connecticut, and Georgia for 100 weeks between December 2010 and March 2013. Of the 27,389 total samples, 116 samples tested positive by the BAX PCR system for L. monocytogenes , and the pathogen was isolated and confirmed for 102 samples. Among the 16 food categories, the proportion of positive samples (i.e., without considering clustering effects) based on recovery of a viable isolate of L. monocytogenes ranged from 0.00% (95% confidence interval: 0.00, 0.18) for the category of soft-ripened and semisoft cheese to 1.07% (0.63, 1.68) for raw cut vegetables. Among the 571 samples that tested positive for Listeria-like organisms, the proportion of positive samples ranged from 0.79% (0.45, 1.28) for soft-ripened and semisoft cheese to 4.76% (2.80, 7.51) for fresh crab meat or sushi. Across all 16 categories, L. monocytogenes contamination was significantly associated with the four states (P < 0.05) but not with the packaging location (prepackaged by the manufacturer versus made and/or packaged in the store), the type of store (national chain versus independent), or the season. Among the 102 samples positive for L. monocytogenes , levels ranged from <0.036 most probable number per g to 6.1 log CFU/g. For delicatessen (deli) meats, smoked seafood, seafood salads, soft-ripened and semisoft cheeses, and deli-type salads without meat, the percentage of positive samples was significantly lower (P < 0.001) in this survey than that reported a decade ago based on comparable surveys in the United States. Use of mixed logistic regression models to address

  7. Occurrence and antimicrobial resistance patterns of Listeria monocytogenes isolated from vegetables

    OpenAIRE

    Byrne,Vanessa de Vasconcelos; Hofer,Ernesto; Vallim,Deyse Christina; Almeida,Rogeria Comastri de Castro

    2016-01-01

    Abstract Although the consumption of fresh and minimally processed vegetables is considered healthy, outbreaks related to the contamination of these products are frequently reported. Among the food-borne pathogens that contaminate vegetables is Listeria monocytogenes, a ubiquitous organism that exhibits the ability to survive and multiply at refrigerated temperatures. This study aimed to evaluate the occurrence of L. monocytogenes in vegetables as well as the antimicrobial resistance of isola...

  8. Listeria monocytogenes Infection in Hairy Cell Leukemia: A Case Report and Literature Review

    Directory of Open Access Journals (Sweden)

    James C. Barton

    2018-01-01

    Full Text Available Listeria monocytogenes infections have been described in patients with diverse types of malignancy, especially leukemia. We report the case of a 65-year-old man with previously untreated hairy cell leukemia characterized by CD5 positivity and trisomy 12 (3% of blood lymphocytes who developed bacteremia due to L. monocytogenes serotype 1/2b. We summarize clinical features and treatment of this patient and five previously reported patients with hairy cell leukemia who also had L. monocytogenes infections. All six patients were men. Their mean age at infection diagnosis was 70 y. Three men had undergone splenectomy 4–11 y before they developed L. monocytogenes infection. The central nervous system was the primary site of infection in four men. Bacteremia alone occurred in two other men. At diagnosis of infection, one man was receiving antileukemia chemotherapy and another man was receiving treatment for Kaposi’s sarcoma. Two other patients had other comorbid conditions. All six men recovered from their infections.

  9. Glycerol metabolism induces Listeria monocytogenes biofilm formation at the air-liquid interface.

    Science.gov (United States)

    Crespo Tapia, Natalia; den Besten, Heidy M W; Abee, Tjakko

    2018-05-20

    Listeria monocytogenes is a food-borne pathogen that can grow as a biofilm on surfaces. Biofilm formation in food-processing environments is a big concern for food safety, as it can cause product contamination through the food-processing line. Although motile aerobic bacteria have been described to form biofilms at the air-liquid interface of cell cultures, to our knowledge, this type of biofilm has not been described in L. monocytogenes before. In this study we report L. monocytogenes biofilm formation at the air-liquid interface of aerobically grown cultures, and that this phenotype is specifically induced when the media is supplemented with glycerol as a carbon and energy source. Planktonic growth, metabolic activity assays and HPLC measurements of glycerol consumption over time showed that glycerol utilization in L. monocytogenes is restricted to growth under aerobic conditions. Gene expression analysis showed that genes encoding the glycerol transporter GlpF, the glycerol kinase GlpK and the glycerol 3-phosphate dehydrogenase GlpD were upregulated in the presence of oxygen, and downregulated in absence of oxygen. Additionally, motility assays revealed the induction of aerotaxis in the presence of glycerol. Our results demonstrate that the formation of biofilms at the air-liquid interface is dependent on glycerol-induced aerotaxis towards the surface of the culture, where L. monocytogenes has access to higher concentrations of oxygen, and is therefore able to utilize this compound as a carbon source. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Thermal Inactivation of Listeria monocytogenes and Salmonella during Water and Steam Blanching of Vegetables.

    Science.gov (United States)

    Ceylan, Erdogan; McMahon, Wendy; Garren, Donna M

    2017-09-01

    Thermal inactivation of Listeria monocytogenes and Salmonella was evaluated on peas, spinach, broccoli, potatoes, and carrots that were treated with hot water and steam. One gram-positive bacterium, L. monocytogenes, and one gram-negative bacterium, Salmonella, were selected as pertinent human pathogens for evaluation. Samples were inoculated with a composite of five strains each of L. monocytogenes and Salmonella to achieve approximately 10 8 to 10 9 CFU/g. Inoculated samples were treated with hot water at 85 and 87.8°C and with steam at 85 and 96.7°C for up to 3.5 min. A greater than 5-log reduction of L. monocytogenes and Salmonella was achieved on all products within 0.5 min by hot water blanching at 85 and 87.8°C. Steam blanching at 85°C reduced Salmonella populations by greater than 5 log on spinach and peas within 2 min and on carrots and broccoli within 3.5 min. Populations of Salmonella were reduced by more than 5 log within 1 min on carrot, spinach, and broccoli and within 2 min on peas by steam blanching at 96.7°C. Steam blanching at 85°C reduced L. monocytogenes populations by more than 5 log on carrots and spinach within 2 min and on broccoli and peas within 3.5 min. L. monocytogenes populations were reduced more than 5 log within 1 min on carrot, spinach, peas and broccoli by steam blanching at 96.7°C. Longer treatment times and higher temperatures were required for steam-blanched samples than for samples blanched with hot water. Results suggest that hot water and steam blanching practices commonly used by the frozen vegetable industry will achieve the desired 5-log lethality of L. monocytogenes and Salmonella and will enhance microbiological safety prior to freezing.

  11. Listeria spp., y L. monocytogenes EN LECHE CRUDA DE CABRA

    Directory of Open Access Journals (Sweden)

    Yolanda Albarracín C

    2008-08-01

    Full Text Available Objective. To test non-pasteurized goat’s milk from the village of ‘la Garita’, Northern Santander, for Listeria monocytogenes. Material and methods. 90 samples of non-pasteurized goat’s milk were obtained over a 4 month period; pH and temperature of each sample were measured. The INVIMA technique was used to isolate L. monocytogenes; the species was confirmed by PCR. Results. The study showed that eight goat milk providers of the zone neither had refrigeration nor pasteurized the milk. The prevalence of L. monocytogenes was 3%; 15% of the samples had other species of Listeria. The milk obtained from this zone contained the pathogen that may cause listeriosis in children less than 5 years of age, pregnant women, adults and immunologically compromised patients. Conclusions. This study shows the occurrence of this pathogen in goat’s milk and identified areas of risk for those people who drink goat’s milk.

  12. [Analysis of antibiotic susceptibility of foodborne Listeria monocytogenes in China].

    Science.gov (United States)

    Yang, Yang; Fu, Ping; Guo, Yunchang; Liu, Xiurmei

    2008-03-01

    To study the antibiotic susceptibility of foodborne Listeria monocytogenes in China. The susceptibilities of 476 strains of foodborne Listeria monocytogenes to antibiotics were determined in Broth Microdilution Susceptibility Testing in Clinical and Laboratory Standards Institute. The antibiotics of gentamicin, ampicillin, penicillin, tetracycline, doxycycline, imipenem, erythromycin, ciprofloxacin, levofloxacin, cephalothin, rifampin, vancomycin, chloramphenicol, Trimethoprim-sulfamethoxazole, ampicillin-sulbactam were used. The rates of antibiotic resistance in 467 is olates were 4.5%. Tetracycline resistance was most prevalent, accouting for 4.07% . The foods that the rates of antibiotic resistance were highest were vegetable (10%). Among 14 provinces, Jilin, Hubei and Hebei were the third top, the rate of which were 19.6% and 9.1% and 8%, respectively. It was suggested that antibiotic resistance exists in foodborne Listeria monocytogenes to a certain extent in China. It should pay more attention to the use of drugs in prevention and clinic treatment to reduce the antibiotic resistant strains.

  13. Silver as antibacterial towards Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Simone eBelluco

    2016-03-01

    Full Text Available Listeria monocytogenes is a serious foodborne pathogen that can contaminate food during processing and can grow during food shelf-life. New types of safe and effective food contact materials embedding antimicrobial agents, like silver, can play an important role in the food industry. The present work aimed at evaluating the in vitro growth kinetics of different strains of L. monocytogenes in the presence of silver, both in its ionic and nano form. The antimicrobial effect was determined by assaying the number of culturable bacterial cells, which formed colonies after incubation in the presence of silver nanoparticles (AgNPs or silver nitrate (AgNO3. Ionic release experiments were performed in parallel. A different reduction of bacterial viability between silver ionic and nano forms was observed, with a time delayed effect exerted by AgNPs. An association between antimicrobial activity and ions concentration was shown by both silver chemical forms, suggesting the major role of ions in the antimicrobial mode of action.

  14. REALIS: Postgenomic Analysis of Listeria Monocytogenes

    Directory of Open Access Journals (Sweden)

    The REALIS Consortium

    2006-04-01

    Full Text Available Listeria monocytogenes is a remarkably successful food-borne pathogen. It is capable a of surviving and proliferating under conditions that exist within the food chain, such as at low temperatures, high salt and low pH and b of colonizing animal host tissues after ingestion of contaminated food, causing opportunistic infections mainly, but not exclusively, in immunocompromised hosts. The ultimate goals of REALIS are two fold: Firstly, it aims to completely decipher all genes required for survival in and adaptation of Listeria monocytogenes to two very different environments, ie., the infected host and the external environment. Secondly, using genomics and postgenomic tools, REALIS seeks to precisely address fundamental questions regarding evolutionary relationships between pathogenic and non-pathogenic Listeria and to define qualities of particularly successful clonal pathovariants in causing disease. This project will provide both industry and health care managers with rational approaches to curbing food-borne contamination, minimising risks of infection and providing novel pharmacological approaches for halting the fulminant course of infection.

  15. Listeriolysin O Regulates the Expression of Optineurin, an Autophagy Adaptor That Inhibits the Growth of Listeria monocytogenes.

    Science.gov (United States)

    Puri, Madhu; La Pietra, Luigi; Mraheil, Mobarak Abu; Lucas, Rudolf; Chakraborty, Trinad; Pillich, Helena

    2017-09-05

    Autophagy, a well-established defense mechanism, enables the elimination of intracellular pathogens including Listeria monocytogenes . Host cell recognition results in ubiquitination of L . monocytogenes and interaction with autophagy adaptors p62/SQSTM1 and NDP52, which target bacteria to autophagosomes by binding to microtubule-associated protein 1 light chain 3 (LC3). Although studies have indicated that L . monocytogenes induces autophagy, the significance of this process in the infectious cycle and the mechanisms involved remain poorly understood. Here, we examined the role of the autophagy adaptor optineurin (OPTN), the phosphorylation of which by the TANK binding kinase 1 (TBK1) enhances its affinity for LC3 and promotes autophagosomal degradation, during L . monocytogenes infection. In LC3- and OPTN-depleted host cells, intracellular replicating L . monocytogenes increased, an effect not seen with a mutant lacking the pore-forming toxin listeriolysin O (LLO). LLO induced the production of OPTN. In host cells expressing an inactive TBK1, bacterial replication was also inhibited. Our studies have uncovered an OPTN-dependent pathway in which L . monocytogenes uses LLO to restrict bacterial growth. Hence, manipulation of autophagy by L . monocytogenes , either through induction or evasion, represents a key event in its intracellular life style and could lead to either cytosolic growth or persistence in intracellular vacuolar structures.

  16. Listeriolysin S: A bacteriocin from epidemic Listeria monocytogenes strains that targets the gut microbiota.

    Science.gov (United States)

    Quereda, Juan J; Meza-Torres, Jazmín; Cossart, Pascale; Pizarro-Cerdá, Javier

    2017-07-04

    Listeria monocytogenes is a Gram-positive food-borne pathogen that in humans may traverse the intestinal, placental and blood/brain barriers, causing gastroenteritis, abortions and meningitis. Crossing of these barriers is dependent on the bacterial ability to enter host cells, and several L. monocytogenes surface and secreted virulence factors are known to facilitate entry and the intracellular lifecycle. The study of L. monocytogenes strains associated to human listeriosis epidemics has revealed the presence of novel virulence factors. One such factor is Listeriolysin S, a thiazole/oxazole modified microcin that displays bactericidal activity and modifies the host microbiota during infection. Our recent results therefore highlight the interaction of L. monocytogenes with gut microbes as a crucial step in epidemic listeriosis. In this article, we will discuss novel implications for this family of toxins in the pathogenesis of diverse medically relevant microorganisms.

  17. PRÉVALENCE DE LISTERIA MONOCYTOGENES DANS LE LAIT CRU DE VACHE AU LIBAN NORD

    Directory of Open Access Journals (Sweden)

    Imad al Kassaa

    2016-06-01

    Full Text Available Al Kassaa Imad, Khaled el Omari, Marwa Saati, Bachar Ismail and Monzer Hamze. 2016. Prevalence of Listeria monocytogenes in raw cow milk in north Lebanon. Lebanese Science Journal, 17(1: 39-45. Listeriosis, although a zoonosis, is an invasive disease that can affect newborns, pregnant women and immunocompromised adults. Clinical manifestations can be expressed by febrile gastroenteritis, invasive forms including severe sepsis, meningitis, rhombencephalitis, prenatal infections and abortions. Species of Listeria bacteria are ubiquitous and adaptable to the environment in animal and plant foods. This study aimed to determine the prevalence of Listeria monocytogenes in 100 samples of fresh cow milk collected from different areas of North Lebanon. Listeria monocytogenes was detected by using the Grand VIDAS technique (Biomérieux France. The results obtained revealed the absence of Listeria monocytogenes in all analyzed samples.

  18. Environmental prevalence and persistence of Listeria monocytogenes in cold-smoked trout processing plants

    Science.gov (United States)

    The presence of Listeria monocytogenes on the surfaces of equipment and workers' hands during different production stages, as well as on fish skin and meat during processing and storage of cold-smoked trout, was investigated. Listeria monocytogenes was recovered from 10 (6.06%) of a total 165 cotto...

  19. Listeria monocytogenes Meningitis in an Immunosuppressed Patient with Autoimmune Hepatitis and IgG4 Subclass Deficiency

    Directory of Open Access Journals (Sweden)

    Shahin Gaini

    2015-01-01

    Full Text Available A 51-year-old Caucasian woman with Listeria monocytogenes meningitis was treated and discharged after an uncomplicated course. Her medical history included immunosuppressive treatment with prednisolone and azathioprine for autoimmune hepatitis. A diagnostic work-up after the meningitis episode revealed that she had low levels of the IgG4 subclass. To our knowledge, this is the first case report describing a possible association between autoimmune hepatitis and the occurrence of Listeria monocytogenes meningitis, describing a possible association between Listeria monocytogenes meningitis and deficiency of the IgG4 subclass and finally describing a possible association between Listeria monocytogenes meningitis and immunosuppressive therapy with prednisolone and azathioprine.

  20. Listeria monocytogenes Meningitis in an Immunosuppressed Patient with Autoimmune Hepatitis and IgG4 Subclass Deficiency

    DEFF Research Database (Denmark)

    Gaini, Shahin

    2015-01-01

    A 51-year-old Caucasian woman with Listeria monocytogenes meningitis was treated and discharged after an uncomplicated course. Her medical history included immunosuppressive treatment with prednisolone and azathioprine for autoimmune hepatitis. A diagnostic work-up after the meningitis episode...... revealed that she had low levels of the IgG4 subclass. To our knowledge, this is the first case report describing a possible association between autoimmune hepatitis and the occurrence of Listeria monocytogenes meningitis, describing a possible association between Listeria monocytogenes meningitis...... and deficiency of the IgG4 subclass and finally describing a possible association between Listeria monocytogenes meningitis and immunosuppressive therapy with prednisolone and azathioprine....

  1. Application of an active alginate coating to control the growth of Listeria monocytogenes on poached and deli turkey products.

    Science.gov (United States)

    Juck, Greg; Neetoo, Hudaa; Chen, Haiqiang

    2010-09-01

    The relatively high prevalence of Listeria monocytogenes in ready-to-eat (RTE) turkey products is of great concern. The overall objective of this study was to develop antimicrobial edible coating formulations to effectively control the growth of this pathogen. The antimicrobials studied were nisin (500IU/g), Novagard CB 1 (0.25%), Guardian NR100 (500ppm), sodium lactate (SL, 2.4%), sodium diacetate (SD, 0.25%), and potassium sorbate (PS, 0.3%). These were incorporated alone or in binary combinations into five edible coatings: alginate, kappa-carrageenan, pectin, xanthan gum, and starch. The coatings were applied onto the surface of home-style poached and processed deli turkey discs inoculated with ~3log CFU/g of L. monocytogenes. The turkey samples were then stored at 22 degrees C for 7days. For poached and processed deli turkey, the coatings were found to be equally effective, with pectin being slightly less effective than the others. The most effective poached turkey treatments seemed to be SL (2.4%)/SD (0.25%) and Nisin (500IU/g)/SL (2.4%), which yielded final populations of 3.0 and 4.9log CFU/g respectively compared to the control which was 7.9log CFU/g. For processed deli turkey, the most effective antimicrobial treatments seemed to be Nisin (500IU/g)/SD (0.25%) and Nisin (500IU/g)/SL (2.4%) with final populations of 1.5 and 1.7log CFU/g respectively compared to the control which was 6.5log CFU/g. In the second phase of the study, home-style poached and store-purchased roasted (deli) turkey inoculated with the pathogen at a level of ~3log CFU/g were coated with alginate incorporating selected antimicrobial combinations and stored for 8weeks at 4 degrees C. Alginate coatings supplemented with SL (2.4%)/PS (0.3%) delayed the growth of L. monocytogenes with final counts reaching 4.3log CFU/g (home-style poached turkey) and 6.5log CFU/g (roasted deli turkey) respectively while the counts in their untreated counterparts were significantly higher (P<0.05) reaching 9

  2. Stevia rebaudiana Bertoni effect on the hemolytic potential of Listeria monocytogenes.

    Science.gov (United States)

    Sansano, S; Rivas, A; Pina-Pérez, M C; Martinez, A; Rodrigo, D

    2017-06-05

    The effect of Stevia rebaudiana Bertoni on the hemolytic potential of Listeria monocytogenes was studied by means of the assessment of the Listeriolysin O (LLO) production. The three factors under study, stevia concentration in the range [0-2.5] % (w/v), incubation temperature (10 and 37°C), and exposure time (0-65h) significantly affected (p≤0.05) the hemolytic activity of L. monocytogenes. Results showed that at the lower incubation temperature the hemolytic potential of the bacterium was significantly reduced, from 100% at 37°C to 8% at 10°C (after 65h of incubation) in unsupplemented substrate (0% stevia). Irrespective of the temperature, 10 or 37°C, supplementation of the medium with stevia at 2.5 % (w/v) reduced the bacterium's hemolytic activity by a maximum of 100%. Furthermore, the time of exposure to 2.5 % (w/v) stevia concentration was also a significant factor reducing the hemolytic capability of L. monocytogenes. The possibility of reducing the pathogenic potential of L. monocytogenes (hemolysis) by exposure to stevia should be confirmed in real food matrices, opening a research niche with a valuable future impact on food safety. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. The virulence regulator PrfA promotes biofilm formation by Listeria monocytogenes.

    Science.gov (United States)

    Lemon, Katherine P; Freitag, Nancy E; Kolter, Roberto

    2010-08-01

    Listeria monocytogenes is a food-borne facultative intracellular pathogen. It is widespread in the environment and has several distinct life-styles. The key transcriptional activator PrfA positively regulates L. monocytogenes virulence genes to mediate the transition from extracellular, flagellum-propelled cell to intracellular pathogen. Here we report the first evidence that PrfA also has a significant positive impact on extracellular biofilm formation. Mutants lacking prfA were defective in surface-adhered biofilm formation. The DeltaprfA mutant exhibited wild-type flagellar motility, and its biofilm defect occurred after initial surface adhesion. We also observed that mutations that led to the constitutive expression of PrfA-dependent virulence genes had a minimal impact on biofilm formation. Furthermore, biofilm development was enhanced in a mutant encoding a PrfA protein variant unable to fully transition from the extracellular form to the virulent, intracellular activity conformation. These results indicate that PrfA positively regulates biofilm formation and suggest that PrfA has a global role in modulating the life-style of L. monocytogenes. The requirement of PrfA for optimal biofilm formation may provide selective pressure to maintain this critical virulence regulator when L. monocytogenes is outside host cells in the environment.

  4. Symptomatic hydrocephalus in a newborn infected with listeria monocytogenes Hidrocefalia sintomática em um recém-nascido infectado com Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Analía L. Laciar

    2000-03-01

    Full Text Available Central nervous system infections caused by Listeria monocytogenes produce a wide range of clinical symptoms which include cerebral abscesses, meningitis and nonmeningitic parenchymal cerebritis. A case study is presented of early listeriosis with signs of meningitis accompanied with septicemia and complicated with severe hydrocephalus.As infecções do sistema nervoso central produzidas por Listeria monocytogenes provocam una grande variedade de sintomas clínicos que incluem abscessos cerebrais, meningites e cerebrites parenquimáticas não meningíticas. Apresenta-se um caso de listeriose precoce com sinais de meningite acompanhada de septicemia e agravado com hidrocefalia grave.

  5. Genetic Characterization of Listeria monocytogenes Isolates from Industrial and Retail Ready-to-Eat Meat-Based Foods and Their Relationship with Clinical Strains from Human Listeriosis in Portugal.

    Science.gov (United States)

    Henriques, A R; Cristino, J Melo; Fraqueza, M J

    2017-04-01

    Listeria monocytogenes isolates (n = 81) recovered from ready-to-eat meat-based food products (RTEMP) collected in industrial processing plants and retail establishments were genetically characterized for comparison with those from human clinical cases of listeriosis (n = 49). The aim was to assess RTEMP as a possible food source for human infection. L. monocytogenes was detected in 12.5% of the RTEMP samples, and in some cases, counts were above the European food safety criteria. All isolates were assessed by multiplex PCR for serogroup determination and detection of virulence-associated genes inlA, inlB, inlC, inlJ, plcA, hlyA, actA, and iap. Serogroups IIb and IVb dominated in RTEMP and human isolates, and all were positive for the assessed virulence genes. Antibiotic susceptibility testing by the disk diffusion method revealed a low level of resistance among the isolates. Pulsed-field gel electrophoresis (PFGE) of L. monocytogenes isolates, using restriction enzymes ApaI and AscI, revealed genetic variability and differentiated the isolates in five clusters. Although some pulsed-field gel electrophoresis profiles of particular RTEMP and human isolates seemed to be highly related, exhibiting more than 90% similarity, which suggests a possible common source, in most cases the strains were not genetically or temporally matched. The close genetic relatedness of RTEMP and human listeriosis strains stressed the importance of preventive measure implementation throughout the food chain.

  6. Listeria monocytogenes: monitoramento desse perigo biológico na cadeia produtiva de frangos do sul do Rio Grande do Sul Listeria monocytogenes: assessing this microbiological hazard in a poultry productive chain in southern Rio Grande do Sul

    Directory of Open Access Journals (Sweden)

    Élen Silveira Nalério

    2009-09-01

    Full Text Available Listeria monocytogenes é uma bactéria patogênica que se tornou um grande desafio para as indústrias de alimentos, entre elas a de frangos, assim como para os órgãos de vigilância sanitária. Apesar da produção de frangos estar em expansão na região sul do Rio Grande do Sul, não há relatos sobre esse patógeno, dessa forma, objetivou-se avaliar a prevalência de L. monocytogenes e de seus sorotipos nos diversos segmentos dessa cadeia produtiva. Nos aviários isolou-se L. monocytogenes em 2,9% (1/35 das amostras de swabs cloacais, não se isolando o microrganismo em amostras provenientes das camas de aviários. No abatedouro, 11,7% (15/128 das amostras apresentaram contaminação por L. monocytogenes e nos frangos resfriados procedentes do comércio, a prevalência foi de 33,3% (15/45.Observou-se que 51,6% (16/31 das cepas de L. monocytogenes pertenciam ao sorotipo 1/2b; 22,5% (7/31 ao sorotipo 4e; 16,1% (5/31 ao sorotipo 1/2a; 6,4% (2/31 ao sorotipo 4b; e 3,2% (1/31 ao sorotipo 1/2c. Há disseminação de L. monocytogenes na cadeia produtiva de frangos da região sul do Rio Grande do Sul e a presença de sorotipos prevalentes em casos/surtos de listeriose traz preocupação à saúde pública.Listeria monocytogenes is a pathogenic bacterium which has become a huge challenge to the food industries, including the poultry industry, and to the health surveillance agencies. Although poultry production is in expansion in southern of Rio Grande do Sul, Brazil, there are not reports about this pathogen thus this study aimed at assessing the prevalence of L monocytogenes and its serotypes in the several segments of this productive chain. In the broilers flocks L. monocytogenes were isolated in 2.9% (1/35 from cloacal swabs samples. This microorganism was not isolated from broiler houses samples. In the abattoir, 11% of the samples presented L. monocytogenes contamination, and in the chilled chicken from retailers its prevalence was 33.3% (15

  7. Campylobacter, Salmonella, Listeria monocytogenes, verotoxigenic Escherichia coli, and Escherichia coli prevalence, enumeration, and subtypes on retail chicken breasts with and without skin.

    Science.gov (United States)

    Cook, Angela; Odumeru, Joseph; Lee, Susan; Pollari, Frank

    2012-01-01

    This study examined the prevalence, counts, and subtypes of Campylobacter, Salmonella, Listeria monocytogenes, verotoxigenic Escherichia coli (VTEC), and E. coli on raw retail chicken breast with the skin on versus the skin off. From January to December 2007, 187 raw skin-on chicken breasts and 131 skin-off chicken breasts were collected from randomly selected retail grocery stores in the Region of Waterloo, Ontario, Canada. Campylobacter isolates were recovered from a higher proportion of the skin-off chicken breasts, 55 (42%) of 131, than of the skin-on chicken breasts tested, 55 (29%) of 187 (P = 0.023). There was no difference in the proportion of Salmonella isolates recovered from the two meat types (P = 0.715): 40 (31%) of 131 skin-off chicken breasts versus 61 (33%) of 187 skin-on chicken breasts. L. monocytogenes isolates were recovered from a statistically lower proportion of the skin-off chicken breasts, 15 (15%) of 99, than of the skin-on chicken breasts, 64 (34%) of 187 (P = 0.001). There was no difference in the proportion of E. coli isolates recovered from the skin-off chicken breasts, 33 (33%) of 99, than from the skin-on chicken breasts, 77 (41%) of 187 (P = 0.204). VTEC was detected on a single skin-off chicken breast. Campylobacter jejuni was the most frequent species isolated on both types of chicken meat: skin-on, 48 (87%) of 55, and skin-off, 51 (94%) of 54. Salmonella serotypes Kentucky and Heidelberg and L. monocytogenes serotype 1/2a were the most frequently detected serotypes from both skin-off and skin-on chicken breasts. Although there appeared to be a trend toward higher enumeration values of these pathogens and E. coli on the skin-on chicken, the differences did not exceed 1 log. This study suggested that skin-off chicken breast may represent a higher risk of consumer exposure to Campylobacter, a similar risk for Salmonella, VTEC, and E. coli, and a lower risk for L. monocytogenes than skin-on chicken breast.

  8. Prevalence and methodologies for detection, characterization and subtyping of Listeria monocytogenes and L. ivanovii in foods and environmental sources

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    Jin-Qiang Chen

    2017-09-01

    Full Text Available Listeria monocytogenes, one of the most important foodborne pathogens, can cause listeriosis, a lethal disease for humans. L. ivanovii, which is closely related to L. monocytogenes, is also widely distributed in nature and infects mainly warm-blooded ruminants, causing economic loss. Thus, there are high priority needs for methodologies for rapid, specific, cost-effective and accurate detection, characterization and subtyping of L. monocytogenes and L. ivanovii in foods and environmental sources. In this review, we (A described L. monocytogenes and L. ivanovii, world-wide incidence of listeriosis, and prevalence of various L. monocytogenes strains in food and environmental sources; (B comprehensively reviewed different types of traditional and newly developed methodologies, including culture-based, antigen/antibody-based, LOOP-mediated isothermal amplification, matrix-assisted laser desorption ionization-time of flight-mass spectrometry, DNA microarray, and genomic sequencing for detection and characterization of L. monocytogenes in foods and environmental sources; (C comprehensively summarized different subtyping methodologies, including pulsed-field gel electrophoresis, multi-locus sequence typing, ribotyping, and phage-typing, and whole genomic sequencing etc. for subtyping of L. monocytogenes strains from food and environmental sources; and (D described the applications of these methodologies in detection and subtyping of L. monocytogenes in foods and food processing facilities.

  9. Comparative Genomics Reveals the Diversity of Restriction-Modification Systems and DNA Methylation Sites in Listeria monocytogenes.

    Science.gov (United States)

    Chen, Poyin; den Bakker, Henk C; Korlach, Jonas; Kong, Nguyet; Storey, Dylan B; Paxinos, Ellen E; Ashby, Meredith; Clark, Tyson; Luong, Khai; Wiedmann, Martin; Weimer, Bart C

    2017-02-01

    Listeria monocytogenes is a bacterial pathogen that is found in a wide variety of anthropogenic and natural environments. Genome sequencing technologies are rapidly becoming a powerful tool in facilitating our understanding of how genotype, classification phenotypes, and virulence phenotypes interact to predict the health risks of individual bacterial isolates. Currently, 57 closed L. monocytogenes genomes are publicly available, representing three of the four phylogenetic lineages, and they suggest that L. monocytogenes has high genomic synteny. This study contributes an additional 15 closed L. monocytogenes genomes that were used to determine the associations between the genome and methylome with host invasion magnitude. In contrast to previous findings, large chromosomal inversions and rearrangements were detected in five isolates at the chromosome terminus and within rRNA genes, including a previously undescribed inversion within rRNA-encoding regions. Each isolate's epigenome contained highly diverse methyltransferase recognition sites, even within the same serotype and methylation pattern. Eleven strains contained a single chromosomally encoded methyltransferase, one strain contained two methylation systems (one system on a plasmid), and three strains exhibited no methylation, despite the occurrence of methyltransferase genes. In three isolates a new, unknown DNA modification was observed in addition to diverse methylation patterns, accompanied by a novel methylation system. Neither chromosome rearrangement nor strain-specific patterns of epigenome modification observed within virulence genes were correlated with serotype designation, clonal complex, or in vitro infectivity. These data suggest that genome diversity is larger than previously considered in L. monocytogenes and that as more genomes are sequenced, additional structure and methylation novelty will be observed in this organism. Listeria monocytogenes is the causative agent of listeriosis, a disease

  10. Atlas(®) Listeria monocytogenes LmG2 Detection Assay Using Transcription Mediated Amplification to Detect Listeria monocytogenes in Selected Foods and Stainless Steel Surface.

    Science.gov (United States)

    Bres, Vanessa; Yang, Hua; Hsu, Ernie; Ren, Yan; Cheng, Ying; Wisniewski, Michele; Hanhan, Maesa; Zaslavsky, Polina; Noll, Nathan; Weaver, Brett; Campbell, Paul; Reshatoff, Michael; Becker, Michael

    2014-01-01

    The Atlas Listeria monocytogenes LmG2 Detection Assay, developed by Roka Bioscience Inc., was compared to a reference culture method for seven food types (hot dogs, cured ham, deli turkey, chicken salad, vanilla ice cream, frozen chocolate cream pie, and frozen cheese pizza) and one surface (stainless steel, grade 316). A 125 g portion of deli turkey was tested using a 1:4 food:media dilution ratio, and a 25 g portion for all other foods was tested using 1:9 food:media dilution ratio. The enrichment time and media for Roka's method was 24 to 28 h for 25 g food samples and environmental surfaces, and 44 to 48 h for 125 g at 35 ± 2°C in PALCAM broth containing 0.02 g/L nalidixic acid. Comparison of the Atlas Listeria monocytogenes LmG2 Detection Assay to the reference method required an unpaired approach. For each matrix, 20 samples inoculated at a fractional level and five samples inoculated at a high level with a different strain of Listeria monocytogenes were tested by each method. The Atlas Listeria monocytogenes LmG2 Detection Assay was compared to the Official Methods of Analysis of AOAC INTERNATIONAL 993.12 method for dairy products, the U.S. Department of Agriculture, Food Safety and Inspection Service, Microbiology Laboratory Guidebook 8.08 method for ready-to-eat meat and environmental samples, and the U.S. Food and Drug Administration Bacteriological Analytical Manual, Chapter 10 method for frozen foods. In the method developer studies, Roka's method, at 24 h (or 44 h for 125 g food samples), had 126 positives out of 200 total inoculated samples, compared to 102 positives for the reference methods at 48 h. In the independent laboratory studies, vanilla ice cream, deli turkey and stainless steel grade 316 were evaluated. Roka's method, at 24 h (or 44 h for 125 g food samples), had 64 positives out of 75 total inoculated samples compared to 54 positives for the reference methods at 48 h. The Atlas Listeria monocytogenes LmG2 Detection Assay detected all 50

  11. Prevalence and quantification of Listeria monocytogenes in beef offal at retail level in Selangor, Malaysia.

    Science.gov (United States)

    Kuan, Chee Hao; Wong, Woan Chwen; Pui, Chai Fung; Mahyudin, Nor Ainy; Tang, John Yew Huat; Nishibuchi, Mitsuaki; Radu, Son

    2013-12-01

    A total of 63 beef offal samples (beef liver = 16; beef lung = 14; beef intestine = 9; beef tripe = 15; beef spleen = 9) from three wet markets (A, B, and C) in Selangor, Malaysia were examined for the prevalence and microbial load of Listeria monocytogenes. A combination of the most probable number and polymerase chain reaction (MPN-PCR) method was employed in this study. It was found that L. monocytogenes detected in 33.33% of the beef offal samples. The prevalence of L. monocytogenes in beef offal purchased from wet markets A, B, and C were 22.73%, 37.50% and 41.18% respectively. The density of L. monocytogenes in all the samples ranged from 2,400 MPN/g. The findings in this study indicate that beef offal can be a potential vehicle of foodborne listeriosis.

  12. Variations in virulence between different electrophoretic types of Listeria monocytogenes

    DEFF Research Database (Denmark)

    Nørrung, Birgit; Andersen, Jens Kirk

    2000-01-01

    A total of 245 strains of Listeria monocytogenes, representing 33 different electrophoretic types (ETs), were examined quantitatively for haemolytic activity. No significant difference was observed in the mean haemolytic activity between different ETs. Eighty four out of 91 strains examined were...... compared with 3.64 among food isolates). The explanation for this may be that more virulent strains are more prone to cause human infection. It is, however, also possible that strains oft. monocytogenes may become more virulent while multiplying in a living organism compared with multiplying in foods....

  13. Fluxes of Ca2+ and K+ are required for the listeriolysin O-dependent internalization pathway of Listeria monocytogenes.

    Science.gov (United States)

    Vadia, Stephen; Seveau, Stephanie

    2014-03-01

    Listeria monocytogenes is responsible for the life-threatening food-borne disease listeriosis. This disease mainly affects elderly and immunocompromised individuals, causing bacteremia and meningoencephalitis. In pregnant women, L. monocytogenes infection leads to abortion and severe infection of the fetus or newborn. The L. monocytogenes intracellular life cycle is critical for pathogenesis. Previous studies have established that the major virulence factor of L. monocytogenes, the pore-forming toxin listeriolysin O (LLO), is sufficient to induce L. monocytogenes internalization into human epithelial cell lines. This internalization pathway strictly requires the formation of LLO pores in the plasma membrane and can be stimulated by the heterologous pore-forming toxin pneumolysin, suggesting that LLO acts nonspecifically by forming transmembrane pores. The present work tested the hypothesis that Ca2+ and K+ fluxes subsequent to perforation by LLO control L. monocytogenes internalization. We report that L. monocytogenes perforates the host cell plasma membrane in an LLO-dependent fashion at the early stage of invasion. In response to perforation, host cells undergo Ca2+ -dependent but K+ -independent resealing of their plasma membrane. In contrast to the plasma membrane resealing process, LLO-induced L. monocytogenes internalization requires both Ca2+ and K+ fluxes. Further linking ion fluxes to bacterial internalization, treating cells with a combination of Ca2+ and K+ ionophores but not with individual ionophores is sufficient to induce efficient internalization of large cargoes, such as 1-μm polystyrene beads and bacteria. We propose that LLO-induced L. monocytogenes internalization requires a Ca2+ - and K+ -dependent internalization pathway that is mechanistically distinct from the process of plasma membrane resealing.

  14. Multifaceted Activity of Listeriolysin O, the Cholesterol-Dependent Cytolysin of Listeria monocytogenes

    Science.gov (United States)

    2014-01-01

    The cholesterol-dependent cytolysins (CDCs) are a large family of pore-forming toxins that are produced by numerous Gram-positive bacterial pathogens. These toxins are released in the extracellular environment as water-soluble monomers or dimers that bind to cholesterol-rich membranes and assemble into large pore complexes. Depending upon their concentration, the nature of the host cell and membrane (cytoplasmic or intracellular) they target, the CDCs can elicit many different cellular responses. Among the CDCs, listeriolysin O (LLO), which is a major virulence factor of the facultative intracellular pathogen Listeria monocytogenes, is involved in several stages of the intracellular lifecycle of the bacterium and displays unique characteristics. It has long been known that following L. monocytogenes internalization into host cells, LLO disrupts the internalization vacuole, enabling the bacterium to replicate into the host cell cytosol. LLO is then used by cytosolic bacteria to spread from cell to cell, avoiding bacterial exposure to the extracellular environment. Although LLO is continuously produced during the intracellular lifecycle of L. monocytogenes, several processes limit its toxicity to ensure the survival of infected cells. It was previously thought that LLO activity was limited to mediating vacuolar escape during bacterial entry and cell to cell spreading. This concept has been challenged by compelling evidence suggesting that LLO secreted by extracellular L. monocytogenes perforates the host cell plasma membrane, triggering important host cell responses. This chapter provides an overview of the well-established intracellular activity of LLO and the multiple roles attributed to LLO secreted by extracellular L. monocytogenes. PMID:24798012

  15. Listeria Monocytogenes Persistence in Ready-to-Eat Sausages and in Processing Plants.

    Science.gov (United States)

    Mureddu, Anna; Mazza, Roberta; Fois, Federica; Meloni, Domenico; Bacciu, Roberto; Piras, Francesca; Mazzette, Rina

    2014-01-21

    Listeria monocytogenes is of major concern in the fermented meat products and is able to persist in their processing environments. The aim of the present work was to evaluate the virulence profile and the persistence capacity of L. monocytogenes strains isolated in Sardinian fermented sausages processing plants. Food (ground meat, sausages at the end of acidification and ripening stage) and environmental samples (a total of n. 385), collected from 4 meat processing plants located in Sardinia (Italy), were examined to detect L. monocytogenes presence. All the L. monocytogenes isolates were identified by polymerase chain reaction (PCR) method. A subset of strains was also characterised by multiplex PCR-based serogrouping, using the lmo0737 , lmo1118 , ORF2819 and ORF2110 genes. Three different multiplex PCRs were used to obtain the virulence profiles by the rrn , hlyA , actA , prfA , inlA , inlB , iap , plcA , plcB and mpl marker genes. Furthermore, in vitro biofilm forming ability and resistance to disinfectants were carried out on microtiter plate. The overall prevalence was 31.5% in food, and 68.5% in environmental samples. The prevalent serotype resulted 1/2c (43%), followed by 1/2a (40%), 4b (8.6%), and 1/2b (8.6%). The amplification products of the virulence genes were found in all the isolates with the following prevalence: 77.1% hlyA ; 100% rrn ; 100% prfA ; 97.1% iap ; 65.7% inlB ; 88.6% inlA ; 100% plcA ; 100% plcB and 74.3% mpl . As for biofilm forming ability, 37.1% of the strains were positive and resulted weak producer, but all the isolates were sensible to disinfectants showing a reduction of L. monocytogenes growth after each incubation time. More appropriate technologies and application of measures of hygienic control should be implemented to prevent the L. monocytogenes growth and cross-contamination in salsiccia sarda processing plants.

  16. Listeria monocytogenes persistence in ready-to-eat sausages and in processing plants

    Directory of Open Access Journals (Sweden)

    Anna Mureddu

    2014-02-01

    Full Text Available Listeria monocytogenes is of major concern in the fermented meat products and is able to persist in their processing environments. The aim of the present work was to evaluate the virulence profile and the persistence capacity of L. monocytogenes strains isolated in Sardinian fermented sausages processing plants. Food (ground meat, sausages at the end of acidification and ripening stage and environmental samples (a total of n. 385, collected from 4 meat processing plants located in Sardinia (Italy, were examined to detect L. monocytogenes presence. All the L. monocytogenes isolates were identified by polymerase chain reaction (PCR method. A subset of strains was also characterised by multiplex PCR-based serogrouping, using the lmo0737, lmo1118, ORF2819 and ORF2110 genes. Three different multiplex PCRs were used to obtain the virulence profiles by the rrn, hlyA, actA, prfA, inlA, inlB, iap, plcA, plcB and mpl marker genes. Furthermore, in vitro biofilm forming ability and resistance to disinfectants were carried out on microtiter plate. The overall prevalence was 31.5% in food, and 68.5% in environmental samples. The prevalent serotype resulted 1/2c (43%, followed by 1/2a (40%, 4b (8.6%, and 1/2b (8.6%. The amplification products of the virulence genes were found in all the isolates with the following prevalence: 77.1% hlyA; 100% rrn; 100% prfA; 97.1% iap; 65.7% inlB; 88.6% inlA; 100% plcA; 100% plcB and 74.3% mpl. As for biofilm forming ability, 37.1% of the strains were positive and resulted weak producer, but all the isolates were sensible to disinfectants showing a reduction of L. monocytogenes growth after each incubation time. More appropriate technologies and application of measures of hygienic control should be implemented to prevent the L. monocytogenes growth and crosscontamination in salsiccia sarda processing plants.

  17. REAL-TIME PCR DETECTION OF LISTERIA MONOCYTOGENES IN FOOD SAMPLES OF ANIMAL ORIGIN

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    Jaroslav Pochop

    2013-02-01

    Full Text Available The aim of this study was to follow the contamination of food with Listeria monocytogenes by using Step One real time polymerase chain reaction (PCR. We used the PrepSEQ Rapid Spin Sample Preparation Kit for isolation of DNA and SensiFAST SYBR Hi-ROX Kit for the real-time PCR performance. In 24 samples of food of animal origin without incubation were detected strains of Listeria monocytogenes in 15 samples (swabs. Nine samples were negative. Our results indicated that the real-time PCR assay developed in this study could sensitively detect Listeria monocytogenes in food of animal origin without incubation. This could prevent infection caused by Listeria monocytogenes, and also could benefit food manufacturing companies by extending their product’s shelf-life as well as saving the cost of warehousing their food products while awaiting pathogen testing results. The rapid real-time PCR-based method performed very well compared to the conventional method. It is a fast, simple, specific and sensitive way to detect nucleic acids, which could be used in clinical diagnostic tests in the future.

  18. Listeria monocytogenes Identification in Food of Animal Origin Used with Real Time PCR

    Directory of Open Access Journals (Sweden)

    Jaroslav Pochop

    2013-10-01

    Full Text Available The aim of this study was to follow the contamination of food with Listeria monocytogenes by using Step One real time polymerase chain reaction (RT PCR. We used the PrepSEQ Rapid Spin Sample Preparation Kit for isolation of DNA and SensiFAST SYBR Hi-ROX Kit for the real-time PCR performance. In 20 samples of food of animal origin with incubation were detected strains of Listeria monocytogenes in 9 samples (swabs. Eleven samples were negative. Our results indicated that the real-time PCR assay developed in this study could sensitively detect Listeria monocytogenes in food of animal origin without incubation. This could prevent infection caused by Listeria monocytogenes, and also could benefit food manufacturing companies by extending their product’s shelf-life as well as saving the cost of warehousing their food products while awaiting pathogen testing results. The rapid real-time PCR-based method performed very well compared to the conventional method. It is a fast, simple, specific and sensitive way to detect nucleic acids, which could be used in clinical diagnostic tests in the future.

  19. An Assessment of Different Genomic Approaches for Inferring Phylogeny of Listeria monocytogenes

    DEFF Research Database (Denmark)

    Henri, Clementine; Leekitcharoenphon, Pimlapas; Carleton, Heather A.

    2017-01-01

    Background/objectives: Whole genome sequencing (WGS) has proven to be a powerful subtyping tool for foodborne pathogenic bacteria like L. monocytogenes. The interests of genome-scale analysis for national surveillance, outbreak detection or source tracking has been largely documented. The genomic......MLPPST) or pan genome (wgMLPPST). Currently, there are little comparisons studies of these different analytical approaches. Our objective was to assess and compare different genomic methods that can be implemented in order to cluster isolates of L monocytogenes.Methods: The clustering methods were evaluated...... on a collection of 207 L. monocytogenes genomes of food origin representative of the genetic diversity of the Anses collection. The trees were then compared using robust statistical analyses.Results: The backward comparability between conventional typing methods and genomic methods revealed a near...

  20. Identification of Surface Protein Biomarkers of Listeria monocytogenes via Bioinformatics and Antibody-Based Protein Detection Tools

    Science.gov (United States)

    Zhang, Cathy X. Y.; Brooks, Brian W.; Huang, Hongsheng; Pagotto, Franco

    2016-01-01

    ABSTRACT The Gram-positive bacterium Listeria monocytogenes causes a significant percentage of the fatalities among foodborne illnesses in humans. Surface proteins specifically expressed in a wide range of L. monocytogenes serotypes under selective enrichment culture conditions could serve as potential biomarkers for detection and isolation of this pathogen via antibody-based methods. Our study aimed to identify such biomarkers. Interrogation of the L. monocytogenes serotype 4b strain F2365 genome identified 130 putative or known surface proteins. The homologues of four surface proteins, LMOf2365_0578, LMOf2365_0581, LMOf2365_0639, and LMOf2365_2117, were assessed as biomarkers due to the presence of conserved regions among strains of L. monocytogenes which are variable among other Listeria species. Rabbit polyclonal antibodies against the four recombinant proteins revealed the expression of only LMOf2365_0639 on the surface of serotype 4b strain LI0521 cells despite PCR detection of mRNA transcripts for all four proteins in the organism. Three of 35 monoclonal antibodies (MAbs) to LMOf2365_0639, MAbs M3643, M3644, and M3651, specifically recognized 42 (91.3%) of 46 L. monocytogenes lineage I and II isolates grown in nonselective brain heart infusion medium. While M3644 and M3651 reacted with 14 to 15 (82.4 to 88.2%) of 17 L. monocytogenes lineage I and II isolates, M3643 reacted with 22 (91.7%) of 24 lineage I, II, and III isolates grown in selective enrichment media (UVM1, modified Fraser, Palcam, and UVM2 media). The three MAbs exhibited only weak reactivities (the optical densities at 414 nm were close to the cutoff value) to some other Listeria species grown in selective enrichment media. Collectively, the data indicate the potential of LMOf2365_0639 as a surface biomarker of L. monocytogenes, with the aid of specific MAbs, for pathogen detection, identification, and isolation in clinical, environmental, and food samples. IMPORTANCE L. monocytogenes is

  1. Listeria monocytogenes alters mast cell phenotype, mediator and osteopontin secretion in a listeriolysin-dependent manner.

    Directory of Open Access Journals (Sweden)

    Catherine E Jobbings

    Full Text Available Whilst mast cells participate in the immune defence against the intracellular bacterium Listeria monocytogenes, there is conflicting evidence regarding the ability of L. monocytogenes to infect mast cells. It is known that the pore-forming toxin listeriolysin (LLO is important for mast cell activation, degranulation and the release of pro-inflammatory cytokines. Mast cells, however, are a potential source of a wide range of cytokines, chemokines and other mediators including osteopontin, which contributes to the clearing of L. monocytogenes infections in vivo, although its source is unknown. We therefore aimed to resolve the controversy of mast cell infection by L. monocytogenes and investigated the extent of mediator release in response to the bacterium. In this paper we show that the infection of bone marrow-derived mast cells by L. monocytogenes is inefficient and LLO-independent. LLO, however, is required for calcium-independent mast cell degranulation as well as for the transient and selective downregulation of cell surface CD117 (c-kit on mast cells. We demonstrate that in addition to the key pro-inflammatory cytokines TNF-α and IL-6, mast cells release a wide range of other mediators in response to L. monocytogenes. Osteopontin, IL-2, IL-4, IL-13 and granulocyte macrophage colony-stimulating factor (GM-CSF, and chemokines including CCL2, CCL3, CCL4 and CCL5 are released in a MyD88-dependent manner. The wide range of mediators released by mast cells in response to L. monocytogenes may play an important role in the recruitment and activation of a variety of immune cells in vivo. The cocktail of mediators, however, is unlikely to skew the immune response to a particular effector response. We propose that mast cells provide a hitherto unreported source of osteopontin, and may provide an important role in co-ordinating the immune response during Listeria infection.

  2. Control options for Listeria monocytogenes in seafoods

    DEFF Research Database (Denmark)

    Huss, Hans Henrik; Jørgensen, Lasse Vigel; Vogel, Birte Fonnesbech

    2000-01-01

    At least three outbreaks of listeriosis associated with seafood have been reported. Listeria monocytogenes is widely distributed in the general environment including fresh water, coastal water and live fish from these areas. Contamination or recontamination of seafood may also take place during...

  3. Prevalence of Listeria monocytogenes in ready-to-eat seafood marketed in Thessaloniki (Northern Greece

    Directory of Open Access Journals (Sweden)

    N. Soultos

    2014-11-01

    Full Text Available Aim: In the current study, a contribution to the knowledge on the prevalence and level of contamination of Listeria monocytogenes in ready-to-eat (RTE seafood marketed in Thessaloniki (Northern Greece was provided; the serovar identity of the L. monocytogenes isolates was also determined. Materials and Methods: A total of 132 RTE seafood samples consisting of 74 smoked fish products, 18 salted fish products, 16 dried fish products, 9 raw marinated fish products, 10 cooked marinated cephalopods and 5 surimi crab stick products were analyzed. L. monocytogenes were isolated and enumerated based on ISO 11290-1/A1 and ISO 11290-2/A1 protocols, respectively, and identified using a multiplex polymerase chain reaction (PCR system utilizing genus and species specific primers. For the identification of serotypes a second multiplex PCR assay was used which clusters L. monocytogenes strains into four major serogroups. Results: Of the samples examined, 11 (8.3% proved positive for Listeria spp. with 8 (6.1% yielding L. monocytogenes. Only in one sample of smoked mackerel the level of L. monocytogenes exceeded the legal safety limit of 100 cfu/g set out in Commission Regulation (EC No. 1441/2007. Serotyping showed higher percentages of isolates belonging to PCR serogroup 3:1/2b, 3b, 7 (46.7% and serogroup 1:1/2a, 3a (40% followed by serogroup 4:4b, 4d, 4e (13.3%. Conclusion: This study demonstrated that L. monocytogenes can be isolated from processed RTE seafood products at retail in Thessaloniki (Northern Greece in low concentrations. However, the presence of this human pathogen in RTE seafood should not be overlooked, but it should be considered as having significance public health implications, particularly among the persons who are at greater risk. Therefore, RTE seafood should be produced under appropriate hygienic and technological conditions since the product does not undergo any treatment before consumption.

  4. Prevalence and contamination levels of listeria monocytogenes in ready-to-eat foods in Tokyo, Japan.

    Science.gov (United States)

    Shimojima, Yukako; Ida, Miki; Nakama, Akiko; Nishino, Yukari; Fukui, Rie; Kuroda, Sumiyo; Hirai, Akihiko; Kai, Akemi; Sadamasu, Kenji

    2016-08-01

    We surveyed prevalence and contamination levels of Listeria monocytogenes in ready-to-eat foods between 2000 and 2012 in Tokyo. L. monocytogenes was isolated from 52 (1.7%) out of 2,980 samples. Comparing the prevalence in the study period, 2.2% were positive in the former period (2000-2005) and 1.2% in the latter (2006-2012). Using the most probable number (MPN) technique, 32 samples were contaminated with fewer than 0.3 L. monocytogenes/g, 10 samples with 0.3-1.0/g and 4 samples with more than 1.0/g (the maximum was 2.3/g). The most common serovar was 1/2a, followed by 1/2b, 4b and 1/2c. We revealed that ready-to-eat foods in Tokyo were contaminated with L. monocytogenes, although the contamination levels were low.

  5. Prevalence and quantification of Listeria monocytogenes in beef offal at retail level in Selangor, Malaysia

    Science.gov (United States)

    Kuan, Chee Hao; Wong, Woan Chwen; Pui, Chai Fung; Mahyudin, Nor Ainy; Tang, John Yew Huat; Nishibuchi, Mitsuaki; Radu, Son

    2013-01-01

    A total of 63 beef offal samples (beef liver = 16; beef lung = 14; beef intestine = 9; beef tripe = 15; beef spleen = 9) from three wet markets (A, B, and C) in Selangor, Malaysia were examined for the prevalence and microbial load of Listeria monocytogenes. A combination of the most probable number and polymerase chain reaction (MPN-PCR) method was employed in this study. It was found that L. monocytogenes detected in 33.33% of the beef offal samples. The prevalence of L. monocytogenes in beef offal purchased from wet markets A, B, and C were 22.73%, 37.50% and 41.18% respectively. The density of L. monocytogenes in all the samples ranged from 2,400 MPN/g. The findings in this study indicate that beef offal can be a potential vehicle of foodborne listeriosis. PMID:24688507

  6. Prevalence and quantification of Listeria monocytogenes in beef offal at retail level in Selangor, Malaysia

    Directory of Open Access Journals (Sweden)

    Chee Hao Kuan

    2013-12-01

    Full Text Available A total of 63 beef offal samples (beef liver = 16; beef lung = 14; beef intestine = 9; beef tripe = 15; beef spleen = 9 from three wet markets (A, B, and C in Selangor, Malaysia were examined for the prevalence and microbial load of Listeria monocytogenes. A combination of the most probable number and polymerase chain reaction (MPN-PCR method was employed in this study. It was found that L. monocytogenes detected in 33.33% of the beef offal samples. The prevalence of L. monocytogenes in beef offal purchased from wet markets A, B, and C were 22.73%, 37.50% and 41.18% respectively. The density of L. monocytogenes in all the samples ranged from 2,400 MPN/g. The findings in this study indicate that beef offal can be a potential vehicle of foodborne listeriosis.

  7. Separation of viable and non-viable tomato (Solanum lycopersicum L.) seeds using single seed near-infrared spectroscopy

    DEFF Research Database (Denmark)

    Shrestha, Santosh; Deleuran, Lise Christina; Gislum, René

    2017-01-01

    Single seed near-infrared (NIR) spectroscopy is a non-destructive technology commonly used for predicting lipids, proteins, carbohydrates and water content of agricultural products. The aim of the current study is to investigate the prospects of NIR spectroscopy in classifying viable and non...... identified as important for classification of viable and non-viable tomato seeds by iPLS-DA. The sensitivity i.e. ability to correctly identify the positive samples and specificity i.e. ability to reject the negative samples of the (iPLS-DA) model on identified spectral regions for prediction of viable......-viable tomato seeds of two cultivars using chemometrics. The data exploration were performed by principal component analysis (PCA). Subsequently, viable and non-viable seeds were classified by partial least squares-discriminant analysis (PLS-DA) and interval PLS-DA (iPLS-DA). The indication of clustering...

  8. Growth, viability and architecture of biofilms of Listeria monocytogenes formed on abiotic surfaces

    Directory of Open Access Journals (Sweden)

    Fernanda Barbosa dos Reis-Teixeira

    Full Text Available Abstract The pathogenic bacterium Listeria monocytogenes can persist in food processing plants for many years, even when appropriate hygienic measures are in place, with potential for contaminating ready-to-eat products and, its ability to form biofilms on abiotic surfaces certainly contributes for the environmental persistence. In this research, L. monocytogenes was grown in biofilms up 8 days attached to stainless steel and glass surfaces, contributing for advancing the knowledge on architecture of mature biofilms, since many literature studies carried out on this topic considered only early stages of cell adhesion. In this study, biofilm populations of two strains of L. monocytogenes (serotypes 1/2a and 4b on stainless steel coupons and glass were examined using regular fluorescence microscopy, confocal laser scanning microscopy and classic culture method. The biofilms formed were not very dense and microscopic observations revealed uneven biofilm structures, with presence of exopolymeric matrix surrounding single cells, small aggregates and microcolonies, in a honeycomb-like arrangement. Moreover, planktonic population of L. monocytogenes (present in broth media covering the abiotic surface remained stable throughout the incubation time, which indicates an efficient dispersal mechanism, since the culture medium was replaced daily. In conclusion, even if these strains of L. monocytogenes were not able to form thick multilayer biofilms, it was noticeable their high persistence on abiotic surfaces, reinforcing the need to focus on measures to avoid biofilm formation, instead of trying to eradicate mature biofilms.

  9. Growth, viability and architecture of biofilms of Listeria monocytogenes formed on abiotic surfaces.

    Science.gov (United States)

    Reis-Teixeira, Fernanda Barbosa Dos; Alves, Virgínia Farias; de Martinis, Elaine Cristina Pereira

    The pathogenic bacterium Listeria monocytogenes can persist in food processing plants for many years, even when appropriate hygienic measures are in place, with potential for contaminating ready-to-eat products and, its ability to form biofilms on abiotic surfaces certainly contributes for the environmental persistence. In this research, L. monocytogenes was grown in biofilms up 8 days attached to stainless steel and glass surfaces, contributing for advancing the knowledge on architecture of mature biofilms, since many literature studies carried out on this topic considered only early stages of cell adhesion. In this study, biofilm populations of two strains of L. monocytogenes (serotypes 1/2a and 4b) on stainless steel coupons and glass were examined using regular fluorescence microscopy, confocal laser scanning microscopy and classic culture method. The biofilms formed were not very dense and microscopic observations revealed uneven biofilm structures, with presence of exopolymeric matrix surrounding single cells, small aggregates and microcolonies, in a honeycomb-like arrangement. Moreover, planktonic population of L. monocytogenes (present in broth media covering the abiotic surface) remained stable throughout the incubation time, which indicates an efficient dispersal mechanism, since the culture medium was replaced daily. In conclusion, even if these strains of L. monocytogenes were not able to form thick multilayer biofilms, it was noticeable their high persistence on abiotic surfaces, reinforcing the need to focus on measures to avoid biofilm formation, instead of trying to eradicate mature biofilms. Copyright © 2017. Published by Elsevier Editora Ltda.

  10. Molecular analysis of the iap gene of Listeria monocytogenes isolated from cheeses in Rio Grande do Sul, Brazil Análise molecular do gene iap de Listeria monocytogenes isoladas de queijos no Estado do Rio Grande do Sul, Brasil

    Directory of Open Access Journals (Sweden)

    Jozi Fagundes de Mello

    2008-03-01

    Full Text Available The polymorphic region sequences in the iap gene were analyzed in 25 strains of Listeria monocytogenes isolated from cheeses in the state of Rio Grande do Sul, and compared with reference strains. This investigation distinguished two clusters of L. monocytogenes: I (20 strains and II (5 strains.A seqüência da região polimórfica do gene iap foi analisada em 25 cepas de Listeria monocytogenes isoladas de queijo no Estado do Rio Grande do Sul e comparadas com cepas referências. Esta investigação distinguiu L. monocytogenes em dois grupos: I (20 cepas e II (5 cepas.

  11. Phloretin Attenuates Listeria monocytogenes Virulence Both In vitro and In vivo by Simultaneously Targeting Listeriolysin O and Sortase A.

    Science.gov (United States)

    Wang, Jianfeng; Liu, Bowen; Teng, Zihao; Zhou, Xuan; Wang, Xiyan; Zhang, Bing; Lu, Gejin; Niu, Xiaodi; Yang, Yongjun; Deng, Xuming

    2017-01-01

    The critical roles of sortase A (SrtA) and listeriolysin O (LLO) in Listeria monocytogenes pathogenicity render these two virulence factors as ideal targets for the development of anti-virulence agents against L. monocytogenes infection. Additionally, the structures of SrtA and LLO are highly conserved among the members of sortase enzyme family and cholesterol dependent toxin family. Here, phloretin, a natural polyphenolic compound derived from apples and pears that has little anti- L. monocytogenes activity, was identified to simultaneously inhibit LLO expression and neutralize SrtA catalytic activity. Phloretin neutralized SrtA activity by causing a conformational change in the protein's active pocket, which prevented engagement with its substrate. Treatment with phloretin simultaneously reduced L. monocytogenes invasion into host cells and blocked the escape of vacuole-entrapped L. monocytogenes into cytoplasm. Further, L. monocytogenes -infected mice that received phloretin showed lower mortality, decreased bacterial burden and reduced pathological injury. Our results demonstrate that phloretin is a promising anti-infective therapeutic for infections caused by L. monocytogenes due to its simultaneous targeting of SrtA and LLO, which may result in fewer side effects than those caused by other antibiotics.

  12. Diversity Assessment of Heat Resistance of Listeria monocytogenes Strains in a Continuous-Flow Heating System

    NARCIS (Netherlands)

    Veen, van der S.; Wagendorp, A.; Abee, T.; Wells-Bennik, M.H.J.

    2009-01-01

    Listeria monocytogenes is a foodborne pathogen that has the ability to survive relatively high temperatures compared with other nonsporulating foodborne pathogens. This study was performed to determine whether L. monocytogenes strains with relatively high heat resistances are adequately inactivated

  13. A Meta-analysis of the Rates of Listeria monocytogenes and Enterococcus in Febrile Infants.

    Science.gov (United States)

    Leazer, Rianna; Perkins, Amy M; Shomaker, Kyrie; Fine, Bryan

    2016-04-01

    A change in the epidemiology of pathogens causing serious bacterial infection (SBI) has been noted since original recommendations were made for the empirical antibiotic choices for young infants with fever. To assess the prevalence of SBI caused by Listeria monocytogenes and Enterococcus species. A literature search was conducted on keywords related to SBI, L. monocytogenes, and Enterococcus spp. infections. Eligible studies were those conducted in the United States and published between January 1998 and June 2014 focusing on SBI in infants≤90 days of age. The rates of urinary tract infection, bacteremia, and meningitis for each pathogen were recorded for each study. Meta-analysis was performed to calculate the prevalence for each pathogen in a random effects model with 0.5 continuity correction added to studies with zero events. Sixteen studies were included. A total of 20,703 blood cultures were included, with weighted prevalences for L. monocytogenes and Enterococcus spp. bacteremia of 0.03% and 0.09%, respectively. A total of 13,775 cerebrospinal fluid cultures were included with event rates (unweighted prevalences) for L. monocytogenes and Enterococcus spp. meningitis of 0.02% and 0.03%, respectively. A total of 18,283 urine cultures were included, with no cases of L. monocytogenes and a weighted prevalence for Enterococcus spp. urinary tract infection of 0.28%. There may have been reporting bias or incomplete retrieval or inadvertent exclusion of relevant studies. SBI caused by L. monocytogenes and Enterococcus spp. in febrile infants is rare, and therefore clinicians may consider a change in empirical antibiotic choices. Copyright © 2016 by the American Academy of Pediatrics.

  14. Comparison of Listeria monocytogenes recoveries from spiked mung bean sprouts by the enrichment methods of three regulatory agencies.

    Science.gov (United States)

    Cauchon, Kaitlin E; Hitchins, Anthony D; Smiley, R Derike

    2017-09-01

    Three selective enrichment methods, the United States Food and Drug Administration's (FDA method), the United States Department of Agriculture Food Safety Inspection Service's (USDA method), and the EN ISO 11290-1 standard method, were assessed for their suitability for recovery of Listeria monocytogenes from spiked mung bean sprouts. Three parameters were evaluated; the enrichment L. monocytogenes population from singly-spiked sprouts, the enrichment L. monocytogenes population from doubly-spiked (L. monocytogenes and Listeria innocua) sprouts, and the population differential resulting from the enrichment of doubly-spiked sprouts. Considerable L. monocytogenes inter-strain variation was observed. The mean enrichment L. monocytogenes populations for singly-spiked sprouts were 6.1 ± 1.2, 4.9 ± 1.2, and 6.9 ± 2.3 log CFU/mL for the FDA, USDA, and EN ISO 11290-1 methods, respectively. The mean L. monocytogenes populations for doubly-spiked sprouts were 4.7 ± 1.1, 5.5 ± 1.3, and 4.6 ± 1.4 log CFU/mL for the FDA, USDA, and ISO 11290-1 enrichment methods, respectively. The corresponding mean population differentials were 2.8 ± 1.1, 3.3 ± 1.3, and 3.6 ± 1.4 Δlog CFU/mL for the same three enrichment methods, respectively. The presence of L. innocua and resident microorganisms on the sprouts negatively impacted final levels of L. monocytogenes with all three enrichment methods. Published by Elsevier Ltd.

  15. Real-time PCR detection of Listeria monocytogenes in infant formula and lettuce following macrophage-based isolation and enrichment.

    Science.gov (United States)

    Day, J B; Basavanna, U

    2015-01-01

    To develop a rapid detection procedure for Listeria monocytogenes in infant formula and lettuce using a macrophage-based enrichment protocol and real-time PCR. A macrophage cell culture system was employed for the isolation and enrichment of L. monocytogenes from infant formula and lettuce for subsequent identification using real-time PCR. Macrophage monolayers were exposed to infant formula and lettuce contaminated with a serial dilution series of L. monocytogenes. As few as approx. 10 CFU ml(-1) or g(-1) of L. monocytogenes were detected in infant formula and lettuce after 16 h postinfection by real-time PCR. Internal positive PCR controls were utilized to eliminate the possibility of false-negative results. Co-inoculation with Listeria innocua did not reduce the L. monocytogenes detection sensitivity. Intracellular L. monocytogenes could also be isolated on Listeria selective media from infected macrophage lysates for subsequent confirmation. The detection method is highly sensitive and specific for L. monocytogenes in infant formula and lettuce and establishes a rapid identification time of 20 and 48 h for presumptive and confirmatory identification, respectively. The method is a promising alternative to many currently used q-PCR detection methods which employ traditional selective media for enrichment of contaminated food samples. Macrophage enrichment of L. monocytogenes eliminates PCR inhibitory food elements and contaminating food microflora which produce cleaner samples that increase the rapidity and sensitivity of detection. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

  16. Occurrence and antimicrobial resistance patterns of Listeria monocytogenes isolated from vegetables

    Directory of Open Access Journals (Sweden)

    Vanessa de Vasconcelos Byrne

    2016-06-01

    Full Text Available Abstract Although the consumption of fresh and minimally processed vegetables is considered healthy, outbreaks related to the contamination of these products are frequently reported. Among the food-borne pathogens that contaminate vegetables is Listeria monocytogenes, a ubiquitous organism that exhibits the ability to survive and multiply at refrigerated temperatures. This study aimed to evaluate the occurrence of L. monocytogenes in vegetables as well as the antimicrobial resistance of isolates. The results showed that 3.03% of samples were contaminated with L. monocytogenes, comprising 2.22% of raw vegetables and 5.56% of ready-to-eat vegetables. Multiplex PCR confirmed the virulence potential of the isolates. Antimicrobial resistance profiling showed that 50% of the isolates were susceptible to the antibiotics used. The resistance of one isolate to penicillin G, a commonly employed therapeutic agent, and the presence of serotype 4b, a serotype commonly associated with food-borne outbreaks, could be potential health hazards for consumers.

  17. Mechanistic studies of the agmatine deiminase from Listeria monocytogenes.

    Science.gov (United States)

    Soares, Charles A; Knuckley, Bryan

    2016-06-01

    Listeria monocytogenes is a Gram-positive food-borne pathogen that is capable of living within extreme environments (i.e. low temperatures and pH). This ability to survive in such conditions may arise, at least in part, from agmatine catabolism via the agmatine deiminase system (AgDS). This catabolic pathway utilizes an agmatine deiminase (AgD) to hydrolyse agmatine into N-carbamoylputrescine (NCP), with concomitant release of ammonia, which increases the pH, thus mitigating the ill effects of the acidic environment. Given the potential significance of this pathway for cell survival, we set out to study the catalytic mechanism of the AgD encoded by L. monocytogenes In the present paper, we describe the catalytic mechanism employed by this enzyme based on pH profiles, pKa measurements of the active site cysteine and solvent isotope effects (SIE). In addition, we report inhibition of this enzyme by two novel AgD inhibitors, i.e. N-(4-aminobutyl)-2-fluoro-ethanimidamide (ABFA) and N-(4-aminobutyl)-2-chloro-ethanimidamide (ABCA). In contrast with other orthologues, L. monocytogenes AgD does not use the reverse protonation or substrate-assisted mechanism, which requires an active site cysteine with a high pKa and has been commonly seen in other members of the guanidinium-modifying enzyme (GME) superfamily. Instead, the L. monocytogenes AgD has a low pKa cysteine in the active site leading to an alternative mechanism of catalysis. This is the first time that this mechanism has been observed in the GME superfamily and is significant because it explains why previously developed mechanism-based inactivators of AgDs are ineffective against this orthologue. © 2016 The Author(s). published by Portland Press Limited on behalf of the Biochemical Society.

  18. Biofilm formation by Listeria monocytogenes on stainless steel surface and biotransfer potential

    Directory of Open Access Journals (Sweden)

    Maíra Maciel Mattos de Oliveira

    2010-03-01

    Full Text Available An experimental model was proposed to study biofilm formation by Listeria monocytogenes ATCC 19117 on AISI 304 (#4 stainless steel surface and biotransfer potential during this process. In this model, biofilm formation was conducted on the surface of stainless steel coupons, set on a stainless steel base with 4 divisions, each one supporting 21 coupons. Trypic Soy Broth was used as bacterial growth substrate, with incubation at 37 ºC and stirring of 50 rpm. The number of adhered cells was determined after 3, 48, 96, 144, 192 and 240 hours of biofilm formation and biotransfer potential from 96 hours. Stainless steel coupons were submitted to Scanning Electron Microscopy (SEM after 3, 144 and 240 hours. Based on the number of adhered cells and SEM, it was observed that L. monocytogenes adhered rapidly to the stainless steel surface, with mature biofilm being formed after 240 hours. The biotransfer potential of bacterium to substrate occurred at all the stages analyzed. The rapid capacity of adhesion to surface, combined with biotransfer potential throughout the biofilm formation stages, make L. monocytogenes a potential risk to the food industry. Both the experimental model developed and the methodology used were efficient in the study of biofilm formation by L. monocytogenes on stainless steel surface and biotransfer potential.

  19. Biofilm formation by Listeria monocytogenes on stainless steel surface and biotransfer potential.

    Science.gov (United States)

    de Oliveira, Maíra Maciel Mattos; Brugnera, Danilo Florisvaldo; Alves, Eduardo; Piccoli, Roberta Hilsdorf

    2010-01-01

    An experimental model was proposed to study biofilm formation by Listeria monocytogenes ATCC 19117 on AISI 304 (#4) stainless steel surface and biotransfer potential during this process. In this model, biofilm formation was conducted on the surface of stainless steel coupons, set on a stainless steel base with 4 divisions, each one supporting 21 coupons. Trypic Soy Broth was used as bacterial growth substrate, with incubation at 37 °C and stirring of 50 rpm. The number of adhered cells was determined after 3, 48, 96, 144, 192 and 240 hours of biofilm formation and biotransfer potential from 96 hours. Stainless steel coupons were submitted to Scanning Electron Microscopy (SEM) after 3, 144 and 240 hours. Based on the number of adhered cells and SEM, it was observed that L. monocytogenes adhered rapidly to the stainless steel surface, with mature biofilm being formed after 240 hours. The biotransfer potential of bacterium to substrate occurred at all the stages analyzed. The rapid capacity of adhesion to surface, combined with biotransfer potential throughout the biofilm formation stages, make L. monocytogenes a potential risk to the food industry. Both the experimental model developed and the methodology used were efficient in the study of biofilm formation by L. monocytogenes on stainless steel surface and biotransfer potential.

  20. Prevalence, enumeration and pheno- and genotypic characteristics of Listeria monocytogenes isolated from raw foods in South China

    Directory of Open Access Journals (Sweden)

    Moutong eChen

    2015-09-01

    Full Text Available Listeria monocytogenes is an important foodborne pathogen that can cause serious illness in immunocompromised individuals, pregnant women, the elderly, and newborns. The aim of this study was to: (i evaluate the prevalence and contamination level (most probable number, MPN of L. monocytogenes in 567 retail raw foods (fishery products, n=154; raw/fresh meat, n=123; frozen foods, n=110; edible fungi, n=108; vegetables, n=72 collected from South China and (ii to gain further knowledge on the phenotype and genotype distributions of this important foodborne pathogen. Approximately 22% of the samples were positive for L. monocytogenes. The contamination levels were between 0.3 and 10 MPN/g in 75.0%, between 10 and 100 MPN/g in 11.0% and less than 100 MPN/g in 14.0% of the countable samples. Five serogroups were identified among the177 foodborne L. monocytogenes isolates, with1/2a-3a (42.4% and1/2b-3b (26.0% serogroups being the most dominant. Serogroup I.1 and II.2 were only found in the edible mushrooms, while serogroup III was dominant in the fishery products, suggesting that specific serogroups of L. monocytogenes may have distinct ecological niches. Ten (5.6% L. monocytogenes isolates exhibited multidrug resistance. Genetic relatedness analysis revealed the absence of distinct associations between specific food types, antibiotic resistance, serogroups, and genetic diversity. The present study provided the first baseline data on the prevalence, contamination level, and characteristics of L. monocytogenes isolated from raw foods in South China. Some multidrug resistant strains belonged to the epidemiologically important serogroups (I.1 and II.1, implying a potential public health risk. In addition, these findings also provide basic information for the Chinese food safety associated authorities to draft appropriate standards to control L. monocytogenes contamination and improve microbiological safety of raw foods.

  1. Local Outbreak of Listeria monocytogenes Serotype 4b Sequence Type 6 Due to Contaminated Meat Pâté.

    Science.gov (United States)

    Althaus, Denise; Jermini, Marco; Giannini, Petra; Martinetti, Gladys; Reinholz, Danuta; Nüesch-Inderbinen, Magdalena; Lehner, Angelika; Stephan, Roger

    2017-04-01

    In January and February 2016, five cases of confirmed and two cases of probable infection due to Listeria monocytogenes serotype 4b, sequence type (ST) 6 belonging to a single pulsed-field gel electrophoresis pulsotype pattern were registered in a region of southern Switzerland. L. monocytogenes was detected in blood samples (four cases) and pleural fluid (one case). Furthermore, L. monocytogenes 4b ST6 was detected in a stool sample of an asymptomatic person exposed to a common food. Forthwith, the food safety authority and a local gourmet meat producer reported L. monocytogenes contamination of meat pâté. Analysis of further food and environmental samples from the premises of the producer yielded isolates matching the clinical strains and confirmed the presence of L. monocytogenes 4b ST6 in the mincing machine as the cause of the food contamination.

  2. Triclosan-Induced Aminoglycoside-Tolerant Listeria monocytogenes Isolates Can Appear as Small-Colony Variants

    DEFF Research Database (Denmark)

    Kastbjerg, Vicky Gaedt; Hein-Kristensen, Line; Gram, Lone

    2014-01-01

    Exposure of the human food-borne pathogen Listeria monocytogenes to sublethal concentrations of triclosan can cause resistance to several aminoglycosides. Aminoglycoside-resistant isolates exhibit two colony morphologies: normal-size and pinpoint colonies. The purposes of the present study were...... to characterize the small colonies of L. monocytogenes and to determine if specific genetic changes could explain the triclosan-induced aminoglycoside resistance in both pinpoint and normal-size isolates. Isolates from the pinpoint colonies grew poorly under aerated conditions, but growth was restored by addition......I and that exposure to triclosan can cause resistance to antibiotics that enters the cell via active transport. Further studies are needed to elucidate if L. monocytogenes pinpoint isolates could have any clinical impact, e.g., in persistent infections....

  3. Effect of starter cultures on survival of Listeria monocytogenes in Čajna sausage

    Science.gov (United States)

    Bošković, M.; Tadić, V.; Đorđević, J.; Glišić, M.; Lakićević, B.; Dimitrijević, M.; Baltić, M. Ž.

    2017-09-01

    The aim of the study was to evaluate the survival of Listeria monocytogenes during the production of Čajna sausage with short maturation time. Sausage batter was inoculated with three different serotypes 4b and serotype 1/2a of L. monocytogenes. Control sausages were without any starter culture added; the second batch was inoculated with strains of Lactobacillus sakei, Staphylococcus carnosus and Staphylococcus xylosus, and the third batch was inoculated with strains of Debaryomyces hansenii, Lactobacillus sakei, Pediococcus acidilactici, Pediococcus pentosaceus, Staphylococcus carnosus and Staphylococcus xylosus. After 18 days of ripening, L. monocytogenes was not detected in any of the sausages, but during this fermentation and drying, the numbers of this pathogen was lower in the sausages inoculated with starter cultures.

  4. Factors associated with Listeria monocytogenes contamination of cold-smoked pork products produced in Latvia and Lithuania.

    OpenAIRE

    Berzins,-A; Horman,-A; Lunden,-J; Korkeala,-H

    2007-01-01

    A total of 312 samples of sliced, vacuum packaged, cold-smoked pork from 15 meat processing plants in Latvia and Lithuania, obtained over a 15-month period from 2003 until 2004, were analyzed for the presence of Listeria monocytogenes at the end of their shelf-life. Overall, 120 samples (38%) tested positive for L. monocytogenes. Despite the long storing period, the levels of L. monocytogenes in cold-smoked pork products were low. Manufacturing processes were studied at seven meat processing ...

  5. An outbreak of an unusual strain of Listeria monocytogenes infection in North-East Scotland.

    Science.gov (United States)

    Okpo, Emmanuel; Leith, Jayne; Smith-Palmer, Alison; Bell, John; Parks, Duncan; Browning, Fiona; Byers, Lynn; Corrigan, Helen; Webster, Diana; Karcher, Anne M; Murray, Andrew; Storey, Tom

    2015-01-01

    Listeria monocytogenes infection is an important cause of illness and hospitalization in vulnerable individuals. In the present study, we describe a community outbreak of Listeria monocytogenes in the North-East region of Scotland, which was epidemiologically, environmentally and microbiologically linked to a local meat product and ready-to-eat product manufacturer. Infected individuals were interviewed, and an environmental investigation was conducted. Clinical and environmental samples were tested by culture, and isolates were typed by fluorescent amplified fragment length polymorphism (fAFLP). Three cases of Listeria monocytogenes were linked geographically, had the same serotype (1/2a) and were indistinguishable by fAFLP type XII.6. The human, food and environmental isolates were of the same serotype and were indistinguishable by molecular typing. This is the first community outbreak of L. monocytogenes reported in Scotland since the current outbreak surveillance was established in 1996. Epidemiological and laboratory evidence indicated poor hand hygiene, unhygienic practices and cross-contamination throughout the manufacturing process of ready-to-eat foods as a possible cause of the outbreak. More stringent control of commercial food establishments that provide ready-to-eat food and the need to advise specifically vulnerable groups, e.g., pregnant women, of the risk of L. monocytogenes in ready-to-eat food is urgently needed. Copyright © 2015 King Saud Bin Abdulaziz University for Health Sciences. Published by Elsevier Ltd. All rights reserved.

  6. Identification of a Peptide-Pheromone that Enhances Listeria monocytogenes Escape from Host Cell Vacuoles

    Science.gov (United States)

    Xayarath, Bobbi; Alonzo, Francis; Freitag, Nancy E.

    2015-01-01

    Listeria monocytogenes is a Gram-positive facultative intracellular bacterial pathogen that invades mammalian cells and escapes from membrane-bound vacuoles to replicate within the host cell cytosol. Gene products required for intracellular bacterial growth and bacterial spread to adjacent cells are regulated by a transcriptional activator known as PrfA. PrfA becomes activated following L. monocytogenes entry into host cells, however the signal that stimulates PrfA activation has not yet been defined. Here we provide evidence for L. monocytogenes secretion of a small peptide pheromone, pPplA, which enhances the escape of L. monocytogenes from host cell vacuoles and may facilitate PrfA activation. The pPplA pheromone is generated via the proteolytic processing of the PplA lipoprotein secretion signal peptide. While the PplA lipoprotein is dispensable for pathogenesis, bacteria lacking the pPplA pheromone are significantly attenuated for virulence in mice and have a reduced efficiency of bacterial escape from the vacuoles of nonprofessional phagocytic cells. Mutational activation of PrfA restores virulence and eliminates the need for pPplA-dependent signaling. Experimental evidence suggests that the pPplA peptide may help signal to L. monocytogenes its presence within the confines of the host cell vacuole, stimulating the expression of gene products that contribute to vacuole escape and facilitating PrfA activation to promote bacterial growth within the cytosol. PMID:25822753

  7. Listeria monocytogenes incidence changes and diversity in some Brazilian dairy industries and retail products.

    Science.gov (United States)

    Oxaran, Virginie; Lee, Sarah Hwa In; Chaul, Luíza Toubas; Corassin, Carlos Humberto; Barancelli, Giovana Verginia; Alves, Virgínia Farias; de Oliveira, Carlos Augusto Fernandes; Gram, Lone; De Martinis, Elaine Cristina Pereira

    2017-12-01

    Listeria monocytogenes can cause listeriosis, a severe foodborne disease. In Brazil, despite very few reported cases of listeriosis, the pathogen has been repeatedly isolated from dairies. This has led the government to implement specific legislation to reduce the hazard. Here, we determined the incidence of L. monocytogenes in five dairies and retail products in the Southeast and Midwest regions of Brazil over eight months. Of 437 samples, three samples (0.7%) from retail and only one sample (0.2%) from the dairies were positive for L. monocytogenes. Thus, the contamination rate was significantly reduced as compared to previous studies. MultiLocus Sequence Typing (MLST) was used to determine if contamination was caused by new or persistent clones leading to the first MLST profile of L. monocytogenes from the Brazilian dairy industry. The processing environment isolate is of concern being a sequence-type (ST) 2, belonging to the lineage I responsible for the majority of listeriosis outbreaks. Also, ST3 and ST8 found in commercialized cheese have previously been reported in outbreaks. Despite the lower incidence, dairy products still pose a potential health risk and the occurrence of L. monocytogenes in dairies and retail products emphasize the need for continuous surveillance of this pathogen in the Brazilian dairy industry. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Detection of Listeria monocytogenes in ready-to-eat food by Step One real-time polymerase chain reaction.

    Science.gov (United States)

    Pochop, Jaroslav; Kačániová, Miroslava; Hleba, Lukáš; Lopasovský, L'ubomír; Bobková, Alica; Zeleňáková, Lucia; Stričík, Michal

    2012-01-01

    The aim of this study was to follow contamination of ready-to-eat food with Listeria monocytogenes by using the Step One real time polymerase chain reaction (PCR). We used the PrepSEQ Rapid Spin Sample Preparation Kit for isolation of DNA and MicroSEQ® Listeria monocytogenes Detection Kit for the real-time PCR performance. In 30 samples of ready-to-eat milk and meat products without incubation we detected strains of Listeria monocytogenes in five samples (swabs). Internal positive control (IPC) was positive in all samples. Our results indicated that the real-time PCR assay developed in this study could sensitively detect Listeria monocytogenes in ready-to-eat food without incubation.

  9. The challenge of setting risk-based microbiological criteria for Listeria monocytogenes

    DEFF Research Database (Denmark)

    Andersen, Jens Kirk; Nørrung, Birgit

    2011-01-01

    After more than 20 years of work with discussing the setting of microbiological criteria for Listeria monocytogenes in foods, Codex Alimentarius on Food Hygiene has finalised a proposal that was recently adopted by the Codex Alimentarius Commission. The effort of developing procedures for making...... the microbiological criteria risk-based to the greatest extent possible has challenged scientists and managers during this long time period. Yet, the establishment of microbiological criteria for L. monocytogenes is still being discussed and several approaches are possible. Setting of microbiological criteria...

  10. Listeria monocytogenes presence during fermentation, drying and storage of Petrovská klobása sausage

    Science.gov (United States)

    Janković, V.; Mitrović, R.; Lakićević, B.; Velebit, B.; Baltić, T.

    2017-09-01

    The majority of human listeriosis cases appear to be caused by consumption of ready-to-eat (RTE) foods contaminated at the time of consumption with high levels of Listeria monocytogenes. Although strategies to prevent growth of L. monocytogenes in RTE products are critical for reducing the incidence of human listeriosis, this pathogen is highly difficult to control in fermented sausage processing environments due to its high tolerance to low pH and high salt concentration. The aims of the present study were to investigate the occurrence, presence and elimination of L. monocytogenes in Petrovská klobása sausage during processing, fermentation, drying and storage. L. monocytogenes, which was detected at the beginning of the production cycle, disappeared before day 30. The pathogen decline was much faster in those sausages which were dried in controlled, industrial conditions than in those dried applying the traditional, household technique.

  11. Inhibitory effect of liposome-entrapped lemongrass oil on the growth of Listeria monocytogenes in cheese.

    Science.gov (United States)

    Cui, H Y; Wu, J; Lin, L

    2016-08-01

    Listeria monocytogenes infection in dairy products is of mounting public concern. To inhibit bacterial growth, we engineered stimuli-responsive liposomes containing lemongrass oil for this study. The controlled release of liposome-entrapped lemongrass oil is triggered by listerolysin O, secreted by L. monocytogenes. We investigated the antibiotic activities of lemongrass oil liposomes against L. monocytogenes in cheese. We also assessed their possible effects on the quality of the cheese. Liposomes containing lemongrass oil (5.0mg/mL) presented the optimal polydispersity index (0.246), zeta-potential (-58.9mV) and entrapment efficiency (25.7%). The liposomes displayed satisfactory antibiotic activity against L. monocytogenes in cheese over the storage period at 4°C. We observed no effects on the physical and sensory properties of the cheese after the liposome treatment. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  12. Spatial and Temporal Factors Associated with an Increased Prevalence of Listeria monocytogenes in Spinach Fields in New York State

    Science.gov (United States)

    Weller, Daniel; Wiedmann, Martin

    2015-01-01

    While rain and irrigation events have been associated with an increased prevalence of foodborne pathogens in produce production environments, quantitative data are needed to determine the effects of various spatial and temporal factors on the risk of produce contamination following these events. This study was performed to quantify these effects and to determine the impact of rain and irrigation events on the detection frequency and diversity of Listeria species (including L. monocytogenes) and L. monocytogenes in produce fields. Two spinach fields, with high and low predicted risks of L. monocytogenes isolation, were sampled 24, 48, 72, and 144 to 192 h following irrigation and rain events. Predicted risk was a function of the field's proximity to water and roads. Factors were evaluated for their association with Listeria species and L. monocytogenes isolation by using generalized linear mixed models (GLMMs). In total, 1,492 (1,092 soil, 334 leaf, 14 fecal, and 52 water) samples were collected. According to the GLMM, the likelihood of Listeria species and L. monocytogenes isolation from soil samples was highest during the 24 h immediately following an event (odds ratios [ORs] of 7.7 and 25, respectively). Additionally, Listeria species and L. monocytogenes isolates associated with irrigation events showed significantly lower sigB allele type diversity than did isolates associated with precipitation events (P = monocytogenes contamination. Small changes in management practices (e.g., not irrigating fields before harvest) may therefore reduce the risk of L. monocytogenes contamination of fresh produce. PMID:26116668

  13. Application of carboxymethyl cellulose and chitosan coatings containing Mentha spicata essential oil in fresh strawberries.

    Science.gov (United States)

    Shahbazi, Yasser

    2018-06-01

    The aim of the present study was to investigate the effects of carboxymethyl cellulose (CMC) and chitosan (CH) coatings containing Mentha spicata essential oil (MSO 0.1 and 0.2%) on survival of Listeria monocytogenes, and physicochemical (weight loss, titratable acidity and pH), microbial (total viable count, psychrotrophic bacteria as well as yeasts and molds) and sensory (appearance, color, texture and overall acceptability) properties of fresh strawberries during refrigerated storage. The treatments of fruits with CH+MSO 0.2% and CMC+MSO 0.2% resulted in the best microbial, physicochemical and organoleptic properties after 12days storage. The final population of L. monocytogenes in treated samples was decreased by 3.92-3.69 compared to control groups. It can be concluded that CH and CMC coatings enriched with MSO can be used as appropriate active packaging materials to preserve fresh strawberries in the food industry. Copyright © 2018 Elsevier B.V. All rights reserved.

  14. Diversity assessment of Listeria monocytogenes biofilm formation: Impact of growth condition, serotype and strain origin

    NARCIS (Netherlands)

    Kadam, S.R.; Besten, den H.M.W.; Veen, van der S.; Zwietering, M.H.; Moezelaar, R.; Abee, T.

    2013-01-01

    The foodborne pathogen Listeria monocytogenes has the ability to produce biofilms in food-processing environments and then contaminate food products, which is a major concern for food safety. The biofilm forming behavior of 143 L. monocytogenes strains was determined in four different media that

  15. Isolation and characterization of an atypical Listeria monocytogenes associated with a canine urinary tract infection

    Science.gov (United States)

    Listeria monocytogenes, a well-described cause of encephalitis and abortion in ruminants and of food-borne illness in humans, is rarely associated with disease in companion animals. A case of urinary tract infection associated with an atypical, weakly hemolytic L. monocytogenes strain is described i...

  16. Prevalence and quantification of Listeria monocytogenes in chicken offal at the retail level in Malaysia.

    Science.gov (United States)

    Kuan, C H; Goh, S G; Loo, Y Y; Chang, W S; Lye, Y L; Puspanadan, S; Tang, J Y H; Nakaguchi, Y; Nishibuchi, M; Mahyudin, N A; Radu, S

    2013-06-01

    A total of 216 chicken offal samples (chicken liver = 72; chicken heart = 72; chicken gizzard = 72) from wet markets and hypermarkets in Selangor, Malaysia, were examined for the presence and density of Listeria monocytogenes by using a combination of the most probable number and PCR method. The prevalence of L. monocytogenes in 216 chicken offal samples examined was 26.39%, and among the positive samples, the chicken gizzard showed the highest percentage at 33.33% compared with chicken liver (25.00%) and chicken heart (20.83%). The microbial load of L. monocytogenes in chicken offal samples ranged from Malaysia.

  17. Inhibition of Listeria monocytogenes by propionic acid-based ingredients in cured deli-style Turkey.

    Science.gov (United States)

    Glass, Kathleen A; McDonnell, Lindsey M; Von Tayson, Roxanne; Wanless, Brandon; Badvela, Mani

    2013-12-01

    Listeria monocytogenes growth can be controlled on ready-to-eat meats through the incorporation of antimicrobial ingredients into the formulation or by postlethality kill steps. However, alternate approaches are needed to provide options that reduce sodium content but maintain protection against pathogen growth in meats after slicing. The objective of this study was to determine the inhibition of L. monocytogenes by propionic acid-based ingredients in high-moisture, cured turkey stored at 4 or 7°C. Six formulations of sliced, cured (120 ppm of NaNO2 ), deli-style turkey were tested, including control without antimicrobials, 3.2% lactate-diacetate blend (LD), 0.4% of a liquid propionate-benzoate-containing ingredient, or 0.3, 0.4, and 0.5% of a liquid propionate-containing ingredient. Products were inoculated with 5 log CFU L. monocytogenes per 100-g package (3 log CFU/ml rinsate), vacuum-sealed, and stored at 4 or 7°C for up to 12 weeks; and populations were enumerated by plating on modified Oxford agar. As expected, the control without antimicrobials supported rapid growth, with >2 log average per ml rinsate increase within 4 weeks of storage at 4°C, whereas growth was observed at 6 weeks for the LD treatment. For both replicate trials, all treatments that contained liquid propionate or propionate-benzoate limited L. monocytogenes growth to an increase of 1-log increase) was observed in individual samples for all propionate-containing treatments at weeks 10, 11, and 12. As expected, L. monocytogenes grew more rapidly when products were stored at 7°C, but trends in relative inhibition were similar to those observed at 4°C. These results verify that propionate-based ingredients inhibit growth of L. monocytogenes on sliced, high-moisture, cured turkey and can be considered as an alternative to reduce sodium-based salts while maintaining food safety.

  18. Genome Sequences of Two Listeria monocytogenes Strains from Nectarines Associated with Listeriosis in 2014

    Science.gov (United States)

    Lu, Chunye; Marjanovic, Olivera; Kiang, David

    2017-01-01

    ABSTRACT Listeria monocytogenes is an important foodborne pathogen. Here, we present the annotated whole genome of Listeria monocytogenes strains F14M01297-C2 and F14M01297-C4, isolated from nectarines distributed by a packing facility in California during an investigation of listeriosis associated with stone fruit in 2014. PMID:28729255

  19. Phenotypic and Genotypic Characteristics of Listeria monocytogenes Isolated From Dairy and Meat Products

    OpenAIRE

    Bahador; Sadeghi Kalani; Valian; Irajian; Lotfollahi

    2015-01-01

    Background Listeria monocytogenes is a foodborne pathogen and a serious threat to the public health in the world. Consumption of traditional foods such as dairy and meat products can be a major reason for relative abundance and isolation of these bacteria. Objectives The purpose of this study was to determine the phenotypic and genotypic characteristics of L. monocytogenes strains isolated from dairy and meat products. ...

  20. Various Ready-to-Eat Products from Retail Stores Linked to Occurrence of Diverse Listeria monocytogenes and Listeria spp. Isolates.

    Science.gov (United States)

    Vongkamjan, Kitiya; Fuangpaiboon, Janejira; Turner, Matthew P; Vuddhakul, Varaporn

    2016-02-01

    Listeriosis outbreaks have been associated with a variety of foods. This study investigated the prevalence and diversity of Listeria monocytogenes and Listeria spp. in ready-to-eat (RTE) products and evaluated the performance of a rapid detection method, the 3M molecular detection assay for L. monocytogenes (MDA-LM), for detection of L. monocytogenes. Assay results were compared with those obtained using the U.S. Food and Drug Administration standard culture method described in the Bacteriological Analytical Manual. Products (n = 200) were purchased from retail stores: 122 aquatic products, 22 products of animal origin, 18 vegetarian products, 15 deli meat products, 13 salad and vegetable products, 4 desserts, 2 egg-based products, and 4 other products. L. monocytogenes prevalence was comparable with both methods. Overall, 15 (7.5%) of 200 samples were positive for L. monocytogenes: 3% of aquatic products, 1.5% of products of animal origin, 1% of vegetarian products, and 2% of deli meat products. Compared with the standard culture method, the sensitivity, specificity, and the accuracy of the MDA-LM were 86.7% (95% confidence interval, 58.4 to 97.7%), 98.4% (95% confidence interval, 95.0 to 99.6%), and 97.5%, respectively. Using the culture-based method, 18 (9%) of 200 samples were positive for Listeria species other than L. monocytogenes. Listeria isolates from these samples were classified into nine allelic types (ATs). The majority of isolates were classified as ATs 58 and 74, which were identified as L. monocytogenes lineages I and IV, respectively. Listeria innocua and Listeria welshimeri also were represented by isolates of multiple ATs. The MDA-LM is a rapid and reliable technique for detecting L. monocytogenes in various RTE foods. Further study is needed to develop effective control strategies to reduce L. monocytogenes contamination in RTE foods.

  1. Introduce of Viable But Nonculturable Bacteria

    Directory of Open Access Journals (Sweden)

    Mehdi Hassanshahian

    2008-03-01

    Full Text Available Viable-But-Nonculturable-State (VBNC is the condition in which bacteria fail to grow on their routine bacteriological media where they would normally grow and develop into colonies, but are still alive and capable of renewed metabolic activity. VBNC state is useful for evaluating public health and for ascertaining the sterility of drinking water, pharmaceuticals, and foodstuff. A number of bacteria, mostly pathogenic to humans, have been proved to enter into this state in response to natural stresses such as starvation, incubation out of optimum growth temperature, increased osmotic pressure, etc. Once in the VBNC state, they undergo various physiological, structural, and genetic alterations. These alterations result in reduced cell size, conversion from bacilli to coccid, thickened cell walls, and peptidoglycan gaining many cross links. Metabolic changes also occur that include reductions in growth, nutrient transport, and respiratory rate; biosynthesis of new protein, and ATP remaining at a constant level. It has been shown that in the VBNC state, some pathogens conserve their virulence properties. Gene expression continues in the VBNC cell. Nucleic acids remain intact in the early VBNC phase but they gradually undergo degradation with prolonged VBNC. Cytological methods such as direct viable count and reduction of tetrazolium salts, and molecular methods such as reverse transcription polymerase chain reaction and green fluorescent protein have been used for the study of VBNC. Resuscitation from VBNC state starts when the inducing factor(s is/are lifted. Factors that help the resuscitation of VBNC bacteria include addition of certain nutrients and chemicals, introduction of a few culturable cells into the VBNC cell population, and passage through the animal host. As virulence properties are sustained during the VBNC phase, special care must be paid when evaluating sterility of drinking water.

  2. Prevalence of Listeria monocytogenes in raw bovine milk and milk products from central highlands of Ethiopia.

    Science.gov (United States)

    Seyoum, Eyasu Tigabu; Woldetsadik, Daniel Asrat; Mekonen, Tesfu Kassa; Gezahegn, Haile Alemayehu; Gebreyes, Wondwossen Abebe

    2015-11-30

    Listeria monocytogenes is of major significance in human and veterinary medicine. Most human Listeria infections are foodborne and the association of contaminated milk and dairy produce consumption with human listeriosis is noteworthy. In Ethiopia, there is limited data regarding the prevalence of L. monocytogenes in raw bovine milk and dairy products. The aim of this study was, therefore, to determine the prevalence of L. monocytogenes in raw bovine milk and dairy produce. A total of 443 milk and milk product samples were microbiologically analyzed following methods recommended by the U.S. Food and Drug Administration Bacteriological Analytical Manual to isolate Listeria spp. The overall prevalence of Listeria spp. was 28.4% and specifically that of L. monocytogenes was 5.6%. Taking the prevalence of Listeria spp. into consideration, cheese was found to be highly contaminated at 60%, followed by pasteurized milk samples (40%), raw milk (18.9%) and yoghurt (5%). Considering the prevalence of Listeria monocytogenes only, raw milk had the lowest contamination while cheese had the highest, followed by pasteurized milk and yoghurt. Raw milk and milk products produced in urban and peri-urban areas of central Ethiopia were contaminated with pathogenic bacteria, L. monocytogenes. The detection of this pathogen in raw milk and milk products warrants an urgent regulatory mechanism to be put in place and also the potential role of milk processing plants in the contamination of dairy products should be investigated.

  3. Effect of packaging and storage time on survival of Listeria monocytogenes on kippered beef steak and turkey tenders.

    Science.gov (United States)

    Uppal, Kamaldeep K; Getty, Kelly J K; Boyle, Elizabeth A E; Harper, Nigel M; Lobaton-Sulabo, April Shayne S; Barry, Bruce

    2012-01-01

    The objective of our study was to determine effect of packaging method and storage time on reducing Listeria monocytogenes in shelf-stable meat snacks. Commercially available kippered beef steak strips and turkey tenders were dipped into a 5-strain L. monocytogenes cocktail, and dried at 23 °C until a water activity of 0.80 was achieved. Inoculated samples were packaged with 4 treatments: (1) vacuum, (2) nitrogen flushed with oxygen scavenger, (3) heat sealed with oxygen scavenger, and (4) heat sealed without oxygen scavenger. Samples were stored at 23 °C and evaluated for L. monocytogenes levels at 0, 24, 48, and 72 h. Initial levels (time 0) of L. monocytogenes were approximately 5.7 log CFU/cm² for steak and tenders. After 24 h of storage time, a 1 log CFU/cm² reduction of L. monocytogenes was observed for turkey tenders for all packaging treatments. After 48 h, turkey tenders showed >1 log CFU/cm² reduction of L. monocytogenes for all packaging treatments except for vacuum, where only 0.9 log CFU/cm² reduction was observed. After 72 h, reductions for all packaging treatments for turkey tenders ranged from 1.5 to 2.4 log CFU/cm². For kippered beef steak, there was no interaction between the packaging treatments and all storage times (P > 0.05) whereas, time was different (P packaging treatments and a 2.1 log CFU/ cm² L. monocytogenes reduction at 72 h of storage time. Processors of kippered beef steak and turkey tenders could use a combination of vacuum or nitrogen-flushing or heat sealed with an oxygen scavenger packaging methods and a holding time of 24 h prior to shipping to reduce potential L. monocytogenes numbers by ≥1 log. However, processors should be encouraged to hold packaged product a minimum of 72 h to enhance the margin of safety for L. monocytogenes control. © 2011 Institute of Food Technologists®

  4. Pulsed-Field Gel Electrophoresis characterization of Listeria monocytogenes isolates from cheese manufacturing plants in São Paulo, Brazil.

    Science.gov (United States)

    Barancelli, Giovana V; Camargo, Tarsila M; Gagliardi, Natália G; Porto, Ernani; Souza, Roberto A; Campioni, Fabio; Falcão, Juliana P; Hofer, Ernesto; Cruz, Adriano G; Oliveira, Carlos A F

    2014-03-03

    This study aimed to evaluate the occurrence of Listeria monocytogenes in cheese and in the environment of three small-scale dairy plants (A, B, C) located in the Northern region state of São Paulo, Brazil, and to characterize the isolates using conventional serotyping and PFGE. A total of 393 samples were collected and analyzed from October 2008 to September 2009. From these, 136 came from dairy plant A, where only L. seeligeri was isolated. In dairy plant B, 136 samples were analyzed, and L. innocua, L. seeligeri and L. welshimeri were isolated together with L. monocytogenes. In dairy plant C, 121 samples were analyzed, and L. monocytogenes and L. innocua were isolated. Cheese from dairy plants B and C were contaminated with Listeria spp, with L. innocua being found in Minas frescal cheese from both dairy plants, and L. innocua and L. monocytogenes in Prato cheese from dairy plant C. A total of 85 L. monocytogenes isolates were classified in 3 serotypes: 1/2b, 1/2c, and 4b, with predominance of serotype 4b in both dairy plants. The 85 isolates found in the dairy plants were characterized by genomic macrorestriction using ApaI and AscI with Pulsed Field Gel Electrophoresis (PFGE). Macrorestriction yielded 30 different pulsotypes. The presence of indistinguishable profiles repeatedly isolated during a 12-month period indicated the persistence of L. monocytogenes in dairy plants B and C, which were more than 100 km away from each other. Brine used in dairy plant C contained more than one L. monocytogenes lineage. The routes of contamination were identified in plants B and C, and highlighted the importance of using molecular techniques and serotyping to track L. monocytogenes sources of contamination, distribution, and routes of contamination in dairy plants, and to develop improved control strategies for L. monocytogenes in dairy plants and dairy products. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Adhesion to the host cell surface is sufficient to mediate Listeria monocytogenes entry into epithelial cells

    Science.gov (United States)

    Ortega, Fabian E.; Rengarajan, Michelle; Chavez, Natalie; Radhakrishnan, Prathima; Gloerich, Martijn; Bianchini, Julie; Siemers, Kathleen; Luckett, William S.; Lauer, Peter; Nelson, W. James; Theriot, Julie A.

    2017-01-01

    The intestinal epithelium is the first physiological barrier breached by the Gram-positive facultative pathogen Listeria monocytogenes during an in vivo infection. Listeria monocytogenes binds to the epithelial host cell receptor E-cadherin, which mediates a physical link between the bacterium and filamentous actin (F-actin). However, the importance of anchoring the bacterium to F-actin through E-cadherin for bacterial invasion has not been tested directly in epithelial cells. Here we demonstrate that depleting αE-catenin, which indirectly links E-cadherin to F-actin, did not decrease L. monocytogenes invasion of epithelial cells in tissue culture. Instead, invasion increased due to increased bacterial adhesion to epithelial monolayers with compromised cell–cell junctions. Furthermore, expression of a mutant E-cadherin lacking the intracellular domain was sufficient for efficient L. monocytogenes invasion of epithelial cells. Importantly, direct biotin-mediated binding of bacteria to surface lipids in the plasma membrane of host epithelial cells was sufficient for uptake. Our results indicate that the only requirement for L. monocytogenes invasion of epithelial cells is adhesion to the host cell surface, and that E-cadherin–mediated coupling of the bacterium to F-actin is not required. PMID:28877987

  6. Effects of essential oils of oregano and nutmeg on growth and survival of Yersinia enterocolitica and Listeria monocytogenes in barbecued chicken.

    Science.gov (United States)

    Firouzi, R; Shekarforoush, S S; Nazer, A H K; Borumand, Z; Jooyandeh, A R

    2007-11-01

    The in vitro effects of plant essential oils (EOs) against pathogenic bacteria are well known, yet few studies have addressed the effects of these compounds against pathogens associated with ready-to-cook foods. Experiments were conducted to determine the effectiveness of oregano and nutmeg EOs on the growth and survival of Yersinia enterocolitica and Listeria monocytogenes in broth culture and in Iranian barbecued chicken. Ready-to-cook Iranian barbecued chicken was prepared according to the common practice with 1, 2, and 3 microl/g of oregano and nutmeg EOs. The test and control (without EOs) samples were inoculated with Y. enterocolitica and L. monocytogenes to a final concentration of 6 to 7 log CFU/g and stored at 3, 8, and 20 degrees C. Microorganisms were counted just before and at 24, 48, and 72 h after storage based on growth on Yersinia selective agar supplemented with cefsulodine, igrasan, and novobiocin and on Listeria selective agar supplemented with nalidixic acid and acriflavin. In the broth culture system, the nutmeg EO had a greater effect on L. monocytogenes (MIC = 0.20 nicrol/ml) than did the oregano EO (MIC = 0.26 microl/ml). However, the oregano EO had a greater effect on Y. enterocolitica (MIC = 0.16 microl/ml) than did the nutmeg EO (MIC = 0.25 microl/ml). In ready-to-cook Iranian barbecued chicken, the log CFU per gram of both bacteria after up to 72 h of incubation was not decreased significantly by various combinations of oregano and nutmeg EOs (1, 2, and 3 microl/g) and storage temperatures (3, 8, and 20 degrees C) when compared with control samples (without EOs). Although examination of spices in culture media can yield accurate microbiological data, without complementary tests in foods these data are of limited value for assessing food safety.

  7. Listeria monocytogenes Growth Kinetics in Milkshakes Made from Naturally and Artificially Contaminated Ice Cream

    Directory of Open Access Journals (Sweden)

    Joelle K. Salazar

    2018-01-01

    Full Text Available This study assessed the growth of Listeria monocytogenes in milkshakes made using the process-contaminated ice cream associated with a listeriosis outbreak in comparison to milkshakes made with artificially contaminated ice cream. For all temperatures, growth kinetics including growth rates, lag phases, maximum populations, and population increases were determined for the naturally and artificially derived contaminants at 5, 10, 15, and 25°C storage for 144 h. The artificially inoculated L. monocytogenes presented lower growth rates and shorter lag phases than the naturally contaminated populations at all temperatures except for 5°C, where the reverse was observed. At 25°C, lag phases of the naturally and artificially contaminated L. monocytogenes were 11.6 and 7.8 h, respectively. The highest increase in population was observed for the artificially inoculated pathogen at 15°C after 96 h (6.16 log CFU/mL of storage. Growth models for both contamination states in milkshakes were determined. In addition, this study evaluated the antimicrobial effectiveness of flavoring agents, including strawberry, chocolate and mint, on the growth of the pathogen in milkshakes during 10°C storage. All flavor additions resulted in decreased growth rates of L. monocytogenes for both contamination states. The addition of chocolate and mint flavoring also resulted in significantly longer lag phases for both contamination states. This study provides insight into the differences in growth between naturally and artificially contaminated L. monocytogenes in a food product.

  8. Listeria monocytogenes Growth Kinetics in Milkshakes Made from Naturally and Artificially Contaminated Ice Cream.

    Science.gov (United States)

    Salazar, Joelle K; Bathija, Vriddi M; Carstens, Christina K; Narula, Sartaj S; Shazer, Arlette; Stewart, Diana; Tortorello, Mary Lou

    2018-01-01

    This study assessed the growth of Listeria monocytogenes in milkshakes made using the process-contaminated ice cream associated with a listeriosis outbreak in comparison to milkshakes made with artificially contaminated ice cream. For all temperatures, growth kinetics including growth rates, lag phases, maximum populations, and population increases were determined for the naturally and artificially derived contaminants at 5, 10, 15, and 25°C storage for 144 h. The artificially inoculated L. monocytogenes presented lower growth rates and shorter lag phases than the naturally contaminated populations at all temperatures except for 5°C, where the reverse was observed. At 25°C, lag phases of the naturally and artificially contaminated L. monocytogenes were 11.6 and 7.8 h, respectively. The highest increase in population was observed for the artificially inoculated pathogen at 15°C after 96 h (6.16 log CFU/mL) of storage. Growth models for both contamination states in milkshakes were determined. In addition, this study evaluated the antimicrobial effectiveness of flavoring agents, including strawberry, chocolate and mint, on the growth of the pathogen in milkshakes during 10°C storage. All flavor additions resulted in decreased growth rates of L. monocytogenes for both contamination states. The addition of chocolate and mint flavoring also resulted in significantly longer lag phases for both contamination states. This study provides insight into the differences in growth between naturally and artificially contaminated L. monocytogenes in a food product.

  9. Enoyl-Acyl Carrier Protein Reductase I (FabI) Is Essential for the Intracellular Growth of Listeria monocytogenes

    Science.gov (United States)

    Ericson, Megan E.; Frank, Matthew W.

    2016-01-01

    Enoyl-acyl carrier protein reductase catalyzes the last step in each elongation cycle of type II bacterial fatty acid synthesis and is a key regulatory protein in bacterial fatty acid synthesis. Genes of the facultative intracellular pathogen Listeria monocytogenes encode two functional enoyl-acyl carrier protein isoforms based on their ability to complement the temperature-sensitive growth phenotype of Escherichia coli strain JP1111 [fabI(Ts)]. The FabI isoform was inactivated by the FabI selective inhibitor AFN-1252, but the FabK isoform was not affected by the drug, as expected. Inhibition of FabI by AFN-1252 decreased endogenous fatty acid synthesis by 80% and lowered the growth rate of L. monocytogenes in laboratory medium. Robust exogenous fatty acid incorporation was not detected in L. monocytogenes unless the pathway was partially inactivated by AFN-1252 treatment. However, supplementation with exogenous fatty acids did not restore normal growth in the presence of AFN-1252. FabI inactivation prevented the intracellular growth of L. monocytogenes, showing that neither FabK nor the incorporation of host cellular fatty acids was sufficient to support the intracellular growth of L. monocytogenes. Our results show that FabI is the primary enoyl-acyl carrier protein reductase of type II bacterial fatty acid synthesis and is essential for the intracellular growth of L. monocytogenes. PMID:27736774

  10. Occurrence and antimicrobial resistance patterns of Listeria monocytogenes isolated from vegetables.

    Science.gov (United States)

    de Vasconcelos Byrne, Vanessa; Hofer, Ernesto; Vallim, Deyse Christina; de Castro Almeida, Rogeria Comastri

    2016-01-01

    Although the consumption of fresh and minimally processed vegetables is considered healthy, outbreaks related to the contamination of these products are frequently reported. Among the food-borne pathogens that contaminate vegetables is Listeria monocytogenes, a ubiquitous organism that exhibits the ability to survive and multiply at refrigerated temperatures. This study aimed to evaluate the occurrence of L. monocytogenes in vegetables as well as the antimicrobial resistance of isolates. The results showed that 3.03% of samples were contaminated with L. monocytogenes, comprising 2.22% of raw vegetables and 5.56% of ready-to-eat vegetables. Multiplex PCR confirmed the virulence potential of the isolates. Antimicrobial resistance profiling showed that 50% of the isolates were susceptible to the antibiotics used. The resistance of one isolate to penicillin G, a commonly employed therapeutic agent, and the presence of serotype 4b, a serotype commonly associated with food-borne outbreaks, could be potential health hazards for consumers. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

  11. Leucocins 4010 from Leuconostoc carnosum cause a matrix related decrease in intracellular pH of Listeria monocytogenes

    DEFF Research Database (Denmark)

    Fang, Weihuan; Budde, Birgitte Bjørn; Siegumfeldt, Henrik

    2006-01-01

    A mixed culture of single cells of Listeria monocytogenes and the bacteriocin producing Leuconostoc carnosum 4010 showed growth inhibition of L. monocytogenes, although the intracellular pH (pHi) of L. monocytogenes followed by fluorescence ratio imaging microscopy was not affected. Furthermore, L...

  12. The Conceptual Mechanism for Viable Organizational Learning Based on Complex System Theory and the Viable System Model

    Science.gov (United States)

    Sung, Dia; You, Yeongmahn; Song, Ji Hoon

    2008-01-01

    The purpose of this research is to explore the possibility of viable learning organizations based on identifying viable organizational learning mechanisms. Two theoretical foundations, complex system theory and viable system theory, have been integrated to provide the rationale for building the sustainable organizational learning mechanism. The…

  13. Listeria monocytogenes in five Sardinian swine slaughterhouses: prevalence, serotype, and genotype characterization.

    Science.gov (United States)

    Meloni, Domenico; Piras, Francesca; Mureddu, Anna; Fois, Federica; Consolati, Simonetta Gianna; Lamon, Sonia; Mazzette, Rina

    2013-11-01

    In a 3-year study (2008 to 2011) to estimate the prevalence and the contamination sources of Listeria monocytogenes in pork meat in Sardinia, Italy, 211 samples were collected from five Sardinian swine slaughterhouses: 171 samples from slaughtered pigs and 40 from the slaughterhouse environment. Fifty L. monocytogenes isolates were characterized by PCR-based serotyping, presence of virulence-associated genes, and pulsed-field gel electrophoresis restriction analysis. The overall prevalence of L. monocytogenes was 33% in swine carcasses, 7% in cecal material, 23% on meat contact surfaces, and 25% on noncontact surfaces. Only two serotypes were detected: 1/2c (78%) and 1/2a (22%). In all, based on the presence of virulence-associated genes, eight pathogenic profiles were detected. Only 42% of all isolates carried the full complement of virulence-associated genes and were allotted to profile 1. Six pulsed-field gel electrophoresis profiles persisted in the slaughterhouses; restriction profiles appeared to be specific to each plant.

  14. Listeria monocytogenes cross-contamination of cheese: risk throughout the food supply chain.

    Science.gov (United States)

    Sauders, B D; D'Amico, D J

    2016-10-01

    Listeria monocytogenes has been the most common microbial cause of cheese-related recalls in both the United States and Canada in recent years. Since L. monocytogenes is inactivated by pasteurization, the majority of these cases have been linked to environmental and cross-contamination of fresh-soft, soft-ripened, and semi-soft cheeses. Cross-contamination of foods with L. monocytogenes is a continuous risk throughout the food supply chain and presents unique challenges for subsequent illness and outbreak investigations. Reports on outbreaks of listeriosis attributed to cross-contamination downstream from primary processing help highlight the critical role of epidemiological investigation coupled with coordinated molecular subtyping and surveillance in the recognition and investigation of complex foodborne outbreaks. Despite their complexity, environmental sampling throughout the supply chain coupled with improved genotyping approaches and concomitant analysis of foodborne illness epidemiological exposure data are needed to help resolve these and similar cases more rapidly and with greater confidence.

  15. Genotypic profile of Listeria monocytogenes isolated in refrigerated chickens in southern Rio Grande do Sul, Brazil

    Directory of Open Access Journals (Sweden)

    Karla Sequeira Mendonça

    2016-01-01

    Full Text Available ABSTRACT: Listeria monocytogenes is of notable concern to the food industry, due to its ubiquitous nature and ability to grow in adverse conditions. This study aimed to determine the genotypic profile of L. monocytogenes strains isolated from refrigerated chickens marketed in the southern part of Rio Grande do Sul, Brazil. The strains of L. monocytogenes isolated were characterized by serotyping and Pulsed Field Gel Electrophoresis (PFGE. Three different serotypes (1/2a, 1/2b and 4e were evaluated by PFGE, and the macrorestriction patterns utilizing enzymes AscI and ApaI, revealed five different pulsotypes. The presence of such varied genotypic profiles demonstrates the prevalence of L. monocytogenes contamination of chicken processing environments, which combined with ineffective cleaning procedures, allowing the survival, adaptation and proliferation of these pathogens, not only in the processing environment, but also in local grocery stores.

  16. New perspectives on the gastrointestinal mode of transmission in invasive Listeria monocytogenes infection

    Energy Technology Data Exchange (ETDEWEB)

    Schlech, W.F. III

    1984-01-01

    The route or mechanism of transmission of Listeria monocytogenes from its rural veterinary reservoir to newborn and older human populations has been obscure. Anecdotal reports of milk-borne infection from cows with Listeria mastitis have been published, but intensive investigations of small outbreaks of L. monocytogenes infections in humans have not supported a gastrointestinal mode of infection. Several recent studies, however, strongly suggest this possibility, and case-control studies of epidemic listeriosis in the Canadian Maritime provinces in 1981 documented an association between ingestion of uncooked vegetables and the development of illness (p = 0.02). In that study, coleslaw from a regional producer which was distributed throughout the Maritimes was considered to be the vehicle of transmission. Cabbage, the raw product in the production of coleslaw, was contaminated at a farm prior to arrival at the plant. Contamination occurred through fertilization with raw manure from a flock of sheep known to harbor L. monocytogenes. Therefore, an indirect link was established between Listeria monocytogenes infection of sheep on a cabbage farm and subsequent development of invasive listeriosis in humans. This study supports findings from other epidemiologic studies of human listeriosis and is consistent with results of investigations into the mode of transmission of natural and laboratory-acquired listeriosis in animals. 34 references.

  17. The use of Listeria monocytogenes as a DNA delivery vector for cancer gene therapy.

    LENUS (Irish Health Repository)

    Tangney, Mark

    2012-01-31

    Listeria monocytogenes is an intracellular pathogen that lyses the phagosomal vacuole of infected cells, proliferates in the host cell cytoplasm and can actively enter adjacent cells. The pathogen is therefore well suited to exploitation as a vector for the delivery of DNA to target cells as the lifecycle favors cellular targeting with vector amplification and the potential for cell-to-cell spread. We have recently demonstrated DNA transfer by L. monocytogenes in growing tumors in murine models. Our approach exploited an ampicillin sensitive stain of L. monocytogenes which can be lysed through systemic administration of ampicillin to facilitate release of plasmid DNA for expression by infected mammalian cells. Here, we discuss the implications of this technology and the potential for future improvements of the system.

  18. Antibacterial activity of bacteriocin-like substance P34 on Listeria monocytogenes in chicken sausage

    Directory of Open Access Journals (Sweden)

    Voltaire Sant'Anna

    2013-12-01

    Full Text Available The antimicrobial activity of the bacteriocin-like substance (BLS P34 against Listeria monocytogenes was investigated in chicken sausage. The BLS was applied to chicken sausages (256 AU g-1 previously inoculated with a suspension of 10² cfu g-1 of L. monocytogenes. BLS P34 inhibited the indicator microorganism in situ in all incubation times for up to 10 days at 5 °C. The effectiveness of BLS P34 was increased when it was added in combination with nisin. The bacteriocin was also tested in natural eatable natural bovine wrapping (salty semi-dried tripe against the same indicator microorganism, also showing inhibitory capability in vitro. BLS P34 showed potential to control L. monocytogenes in refrigerated meat products.

  19. Enrichment dynamics of Listeria monocytogenes and the associated microbiome from naturally contaminated ice cream linked to a listeriosis outbreak.

    Science.gov (United States)

    Ottesen, Andrea; Ramachandran, Padmini; Reed, Elizabeth; White, James R; Hasan, Nur; Subramanian, Poorani; Ryan, Gina; Jarvis, Karen; Grim, Christopher; Daquiqan, Ninalynn; Hanes, Darcy; Allard, Marc; Colwell, Rita; Brown, Eric; Chen, Yi

    2016-11-16

    Microbiota that co-enrich during efforts to recover pathogens from foodborne outbreaks interfere with efficient detection and recovery. Here, dynamics of co-enriching microbiota during recovery of Listeria monocytogenes from naturally contaminated ice cream samples linked to an outbreak are described for three different initial enrichment formulations used by the Food and Drug Administration (FDA), the International Organization of Standardization (ISO), and the United States Department of Agriculture (USDA). Enrichment cultures were analyzed using DNA extraction and sequencing from samples taken every 4 h throughout 48 h of enrichment. Resphera Insight and CosmosID analysis tools were employed for high-resolution profiling of 16S rRNA amplicons and whole genome shotgun data, respectively. During enrichment, other bacterial taxa were identified, including Anoxybacillus, Geobacillus, Serratia, Pseudomonas, Erwinia, and Streptococcus spp. Surprisingly, incidence of L. monocytogenes was proportionally greater at hour 0 than when tested 4, 8, and 12 h later with all three enrichment schemes. The corresponding increase in Anoxybacillus and Geobacillus spp.indicated these taxa co-enriched in competition with L. monocytogenes during early enrichment hours. L. monocytogenes became dominant after 24 h in all three enrichments. DNA sequences obtained from shotgun metagenomic data of Listeria monocytogenes at 48 h were assembled to produce a consensus draft genome which appeared to have a similar tracking utility to pure culture isolates of L. monocytogenes. All three methods performed equally well for enrichment of Listeria monocytogenes. The observation of potential competitive exclusion of L. mono by Anoxybacillus and Geobacillus in early enrichment hours provided novel information that may be used to further optimize enrichment formulations. Application of Resphera Insight for high-resolution analysis of 16S amplicon sequences accurately identified L. monocytogenes

  20. Spatial and Temporal Factors Associated with an Increased Prevalence of Listeria monocytogenes in Spinach Fields in New York State.

    Science.gov (United States)

    Weller, Daniel; Wiedmann, Martin; Strawn, Laura K

    2015-09-01

    While rain and irrigation events have been associated with an increased prevalence of foodborne pathogens in produce production environments, quantitative data are needed to determine the effects of various spatial and temporal factors on the risk of produce contamination following these events. This study was performed to quantify these effects and to determine the impact of rain and irrigation events on the detection frequency and diversity of Listeria species (including L. monocytogenes) and L. monocytogenes in produce fields. Two spinach fields, with high and low predicted risks of L. monocytogenes isolation, were sampled 24, 48, 72, and 144 to 192 h following irrigation and rain events. Predicted risk was a function of the field's proximity to water and roads. Factors were evaluated for their association with Listeria species and L. monocytogenes isolation by using generalized linear mixed models (GLMMs). In total, 1,492 (1,092 soil, 334 leaf, 14 fecal, and 52 water) samples were collected. According to the GLMM, the likelihood of Listeria species and L. monocytogenes isolation from soil samples was highest during the 24 h immediately following an event (odds ratios [ORs] of 7.7 and 25, respectively). Additionally, Listeria species and L. monocytogenes isolates associated with irrigation events showed significantly lower sigB allele type diversity than did isolates associated with precipitation events (P = <0.001), suggesting that irrigation water may be a point source of L. monocytogenes contamination. Small changes in management practices (e.g., not irrigating fields before harvest) may therefore reduce the risk of L. monocytogenes contamination of fresh produce. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  1. Faecal shedding and strain diversity of Listeria monocytogenes in healthy ruminants and swine in Northern Spain

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    Hurtado Ana

    2009-01-01

    Full Text Available Abstract Background Listeria monocytogenes is among the most important foodborne bacterial pathogens due to the high mortality rate and severity of the infection. L. monocytogenes is a ubiquitous organism occasionally present in the intestinal tract of various animal species and faecal shedding by asymptomatically infected livestock poses a risk for contamination of farm environments and raw food at the pre-harvest stages. The aim of this study was to determine the prevalence and strain diversity of L. monocytogenes in healthy ruminants and swine herds. Results Faecal samples from 30 animals per herd were collected from 343 herds (120 sheep, 124 beef cattle, 82 dairy cattle and 17 swine in the Basque Country and screened in pools by an automated enzyme-linked fluorescent immunoassay (VIDAS® to estimate the prevalence of positive herds. Positive samples were subcultured onto the selective and differential agar ALOA and biochemically confirmed. L. monocytogenes was isolated from 46.3% of dairy cattle, 30.6% beef cattle and 14.2% sheep herds, but not from swine. Within-herd prevalence investigated by individually analysing 197 sheep and 221 cattle detected 1.5% of faecal shedders in sheep and 21.3% in cattle. Serotyping of 114 isolates identified complex 4b as the most prevalent (84.2%, followed by 1/2a (13.2%, and PFGE analysis of 68 isolates showed a highly diverse L. monocytogenes population in ruminant herds. Conclusion These results suggested that cattle represent a potentially important reservoir for L. monocytogenes in the Basque Country, and highlighted the complexity of pathogen control at the farm level.

  2. Effect of citral and carvacrol on the susceptibility of Listeria monocytogenes and Listeria innocua to antibiotics.

    Science.gov (United States)

    Zanini, S F; Silva-Angulo, A B; Rosenthal, A; Rodrigo, D; Martínez, A

    2014-05-01

    The aim of this study was to evaluate the antibiotic susceptibility of Listeria innocua (L. innocua) and Listeria monocytogenes (L. monocytogenes) cells in the presence of citral and carvacrol at sublethal concentrations in an agar medium. The presence of terpenes in the L. monocytogenes and L. innocua culture medium provided a reduction in the minimal inhibitory concentration (MIC) of all the antibiotics tested. These effects were dependent on the concentration of terpenes present in the culture medium. The combination of citral and carvacrol potentiated antibiotic activity by reducing the MIC values of bacitracin and colistin from 32.0 and 128.0 μg ml⁻¹ to 1.0 and 2.0 μg ml⁻¹, respectively. Thus, both Listeria species became more susceptible to these drugs. In this way, the colistin and bacitracin resistance of L. monocytogenes and L. innocua was reversed in the presence of terpenes. Results obtained in this study show that the phytochemicals citral and carvacrol potentiate antibiotic activity, reducing the MIC values of cultured L. monocytogenes and L. innocua. Phytochemicals citral and carvacrol potentiate antibiotic activity of erythromycin, bacitracin and colistin by reducing the MIC values of cultured Listeria monocytogenes and Listeria innocua. This effect in reducing the MIC values of the antibiotics tested in both micro-organisms was increased when natural antimicrobials were combined. This finding indicated that the combination among terpenes and antibiotic may contribute in reducing the required dosage of antibiotics due to the possible effect of terpenes on permeation barrier of the micro-organism cell membrane. © 2014 The Society for Applied Microbiology.

  3. Concerns about the microbiological quality of traditional raw milk cheeses: a worldwide issue

    Directory of Open Access Journals (Sweden)

    Erica Tirloni

    2014-11-01

    Full Text Available Six types of unripened raw milk fresh (Robiola, Crescenza, Primo sale and Formaggella and  “pasta filata” cheeses (Mozzarella and Burrata were evaluated for microbiological parameters. No Listeria monocytogenes or Salmonella spp. were detected, but high microbial counts were revealed. Significantly higher Total Viable Counts (TVC and Enterobacteriaceae counts were observed in “fresh cheese” than in “pasta filata” samples. Values > 6 Log CFU/g were found in 81.3% of fresh vs 50% in pasta filata for TVC and 65.6% vs 12.5% for Enterobacteriaceae, respectively. An evident contamination by Escherichia coli, Coagulase-positive Staphylococci and Pseudomonas spp. was detected in all the cheeses: the causes could be the improper hygiene of the artisanal production practices and the permanence of the cheeses on the refrigerated shelves. A careful attention to the respect of the good manufacturing practices is suggested to avoid the presence of initial high bacterial loads.

  4. Sensitive enumeration of Listeria monocytogenes and other Listeria species in various naturally contaminated matrices using a membrane filtration method.

    Science.gov (United States)

    Barre, Léna; Brasseur, Emilie; Doux, Camille; Lombard, Bertrand; Besse, Nathalie Gnanou

    2015-06-01

    For the enumeration of Listeria monocytogenes (L. monocytogenes) in food, a sensitive enumeration method has been recently developed. This method is based on a membrane filtration of the food suspension followed by transfer of the filter on a selective medium to enumerate L. monocytogenes. An evaluation of this method was performed with several categories of foods naturally contaminated with L. monocytogenes. The results obtained with this technique were compared with those obtained from the modified reference EN ISO 11290-2 method for the enumeration of L. monocytogenes in food, and are found to provide more precise results. In most cases, the filtration method enabled to examine a greater quantity of food thus greatly improving the sensitivity of the enumeration. However, it was hardly applicable to some food categories because of filtration problems and background microbiota interference. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Modelling the growth of Listeria monocytogenes in fresh green coconut (Cocos nucifera L.) water.

    Science.gov (United States)

    Walter, Eduardo H M; Kabuki, Dirce Y; Esper, Luciana M R; Sant'Ana, Anderson S; Kuaye, Arnaldo Y

    2009-09-01

    The behaviour of Listeria monocytogenes in the fresh coconut water stored at 4 degrees C, 10 degrees C and 35 degrees C was studied. The coconut water was aseptically extracted from green coconuts (Cocos nucifera L.) and samples were inoculated in triplicate with a mixture of 5 strains of L. monocytogenes with a mean population of approximately 3 log(10) CFU/mL. The kinetic parameters of the bacteria were estimated from the Baranyi model, and compared with predictions of the Pathogen Modelling Program so as to predict its behaviour in the beverage. The results demonstrated that fresh green coconut water was a beverage propitious for the survival and growth of L. monocytogenes and that refrigeration at 10 degrees C or 4 degrees C retarded, but did not inhibit, growth of this bacterium. Temperature abuse at 35 degrees C considerably reduced the lagtimes. The study shows that L. monocytogenes growth in fresh green coconut water is controlled for several days by storage at low temperature, mainly at 4 degrees C. Thus, for risk population this product should only be drunk directly from the coconut or despite the sensorial alterations should be consumed pasteurized.

  6. Acanthamoeba feature a unique backpacking strategy to trap and feed on Listeria monocytogenes and other motile bacteria

    DEFF Research Database (Denmark)

    Doyscher, Dominik; Fieseler, Lars; Dons, Lone Elisabet

    2013-01-01

    Despite its prominent role as an intracellular human pathogen, Listeria monocytogenes normally features a saprophytic lifestyle, and shares many environmental habitats with predatory protozoa. Earlier studies claimed that Acanthamoeba may act as environmental reservoirs for L.?monocytogenes, wher......Despite its prominent role as an intracellular human pathogen, Listeria monocytogenes normally features a saprophytic lifestyle, and shares many environmental habitats with predatory protozoa. Earlier studies claimed that Acanthamoeba may act as environmental reservoirs for L.......?monocytogenes, whereas others failed to confirm this hypothesis. Our findings support the latter and provide clear evidence that L.?monocytogenes is unable to persist in Acanthamoeba castellanii and A.?polyphaga. Instead, external Listeria cells are rapidly immobilized on the surface of Acanthamoeba trophozoites......-lapse microscopy revealed that shortly after the bacteria are collected, the amoeba can change direction of movement, phagocytose the backpack and continue to repeat the process. The phenomenon was also observed with avirulent L.?monocytogenes mutants, non-pathogenic Listeria, and other motile bacteria, indicating...

  7. Comparison of the Prevalences and Diversities of Listeria Species and Listeria monocytogenes in an Urban and a Rural Agricultural Watershed.

    Science.gov (United States)

    Stea, Emma C; Purdue, Laura M; Jamieson, Rob C; Yost, Chris K; Truelstrup Hansen, Lisbeth

    2015-06-01

    Foods and related processing environments are commonly contaminated with the pathogenic Listeria monocytogenes. To investigate potential environmental reservoirs of Listeria spp. and L. monocytogenes, surface water and point source pollution samples from an urban and a rural municipal water supply watershed in Nova Scotia, Canada, were examined over 18 months. Presumptive Listeria spp. were cultured from 72 and 35% of rural and urban water samples, respectively, with 24% of the positive samples containing two or three different Listeria spp. The L. innocua (56%) and L. welshimeri (43%) groups were predominant in the rural and urban watersheds, respectively. Analysis by the TaqMan assay showed a significantly (P monocytogenes of 62% versus 17% by the culture-based method. Both methods revealed higher prevalences in the rural watershed and during the fall and winter seasons. Elevated Escherichia coli (≥ 100 CFU/100 ml) levels were not associated with the pathogen regardless of the detection method. Isolation of Listeria spp. were associated with 70 times higher odds of isolating L. monocytogenes (odds ratio = 70; P monocytogenes isolates, followed by IVb (16.1%), IIb (15.8%), and IIc (0.4%). L. monocytogenes was detected in cow feces and raw sewage but not in septic tank samples. Pulsotyping of representative water (n = 54) and local human (n = 19) isolates suggested genetic similarities among some environmental and human L. monocytogenes isolates. In conclusion, temperate surface waters contain a diverse Listeria species population and could be a potential reservoir for L. monocytogenes, especially in rural agricultural watersheds. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  8. Listeria monocytogenes in RTE foods marketed in Italy: prevalence and automated EcoRI ribotyping of the isolates.

    Science.gov (United States)

    Meloni, Domenico; Galluzzo, Pietro; Mureddu, Anna; Piras, Francesca; Griffiths, Mansel; Mazzette, Rina

    2009-02-15

    The aims of the present study were: (a) to investigate the prevalence and the enumeration of Listeria monocytogenes in 200 samples of ready to eat (RTE) foods of animal and vegetal origin collected from different outlets and processing plants in Sardinia; (b) to characterize the isolates by phenotypical and molecular methods; (c) to analyze a subset of 42 L. monocytogenes by automated EcoRI ribotyping in order to predict the strain's potential virulence for humans. The strains were isolated from: smoked fish products, cooked marinated products, meat products and pre-packaged mixed vegetable salads. Of the samples tested, 22% were positive for Listeria spp. The prevalence of L. monocytogenes was 9.5%, while the level of L. monocytogenes in the positive samples was 93%), belonging to 17 different DuPont Identification Library Codes (DUP-IDs) clones. The Simpson's numerical index of discrimination was 0.911. Cluster analysis pointed out a high similarity among strains isolated from meat, fish, and vegetables of different origin. These results confirmed the existence of a widespread population of L. monocytogenes, characterized by highly related strains existing in different geographical areas. 65% of these strains belonged to lineage II (serotypes 1/2a and 1/2c), subtypes known to be associated with sporadic human listeriosis outbreaks. The remaining 35% of the isolates (serotypes 1/2b, 3b and 4b) were allocated to lineage I and belong to distinct clonal groups (DUP-ID 1038 and 1042), which again have been associated with several outbreaks of human listeriosis. Neither atypical profiles nor lineage III strains were found. EcoRI ribotyping was confirmed as a rapid and reliable method for L. monocytogenes typing, providing useful data for epidemiologic and clonality surveys of L. monocytogenes strains isolated from RTE foods.

  9. Prevalence, antimicrobial susceptibility and virulotyping of Listeria species and Listeria monocytogenes isolated from open-air fish markets.

    Science.gov (United States)

    Jamali, Hossein; Paydar, Mohammadjavad; Ismail, Salmah; Looi, Chung Yeng; Wong, Won Fen; Radmehr, Behrad; Abedini, Atefeh

    2015-07-25

    The aim of this study was to investigate the prevalence and characterization of Listeria species and Listeria monocytogenes isolated from raw fish and open-air fish market environments. Eight hundred and sixty two samples including raw fish and fish market environments (samples from workers' hands, workers' knives, containers and work surface) were collected from the open-air fish markets in the Northern region of Iran. Listeria spp. was isolated from 104/488 (21.3%) raw fish and 29/374 (7.8%) of samples from open-air fish market environment. The isolates of Listeria spp. included L. innocua (35.3%), L. monocytogenes (32.3%), L. seeligeri (18%), and L. ivanovii (14.3%). Of the 43 L. monocytogenes isolates, 31 (72.1%), 10 (23.3%) and 2 (4.7%) belonged to serovars 1/2a, 4b, and 1/2b, respectively. The inlA, inlB, inlC, inlJ, actA, hlyA, iap, plcA, and prfA virulence-associated genes were detected in almost all of the L. monocytogenes isolates. The Listeria spp. isolates showed high resistance against tetracycline (23.3%), penicillin G, and cephalothin (each 16.5%). Besides, we observed significant resistance level to tetracycline (27.9%), ampicillin (20.9%), cephalothin, penicillin G, and streptomycin (each 16.3%) in the L. monocytogenes isolates. All of the isolates were susceptible to cefotaxime, gentamicin, kanamycin, and pefloxacin. We found that tetM (25.6%), tetA (23.3%), ampC (14%), and penA (11.6%) were the most prevalent antibiotic resistance genes in the L. monocytogenes isolates. Recovery of potentially pathogenic L. monocytogenes from raw fish and environment of open-air fish market samples in this study is a convincing evidence for the zoonotic potential of listeriosis.

  10. Polymerase chain reaction-based discrimination of viable from non-viable Mycoplasma gallisepticum

    Directory of Open Access Journals (Sweden)

    Ching Giap Tan

    2014-09-01

    Full Text Available The present study was based on the reverse transcription polymerase chain reaction (RT-PCR of the 16S ribosomal nucleic acid (rRNA of Mycoplasma for detection of viable Mycoplasma gallisepticum. To determine the stability of M. gallisepticum 16S rRNA in vitro, three inactivation methods were used and the suspensions were stored at different temperatures. The 16S rRNA of M. gallisepticum was detected up to approximately 20–25 h at 37 °C, 22–25 h at 16 °C, and 23–27 h at 4 °C. The test, therefore, could detect viable or recently dead M. gallisepticum (< 20 h. The RT-PCR method was applied during an in vivo study of drug efficacy under experimental conditions, where commercial broiler-breeder eggs were inoculated with M. gallisepticum into the yolk. Hatched chicks that had been inoculated in ovo were treated with Macrolide 1. The method was then applied in a flock of day 0 chicks with naturally acquired vertical transmission of M. gallisepticum, treated with Macrolide 2. Swabs of the respiratory tract were obtained for PCR and RT-PCR evaluations to determine the viability of M. gallisepticum. This study proved that the combination of both PCR and RT-PCR enables detection and differentiation of viable from non-viable M. gallisepticum.

  11. Differential gene expression and filamentation of Listeria monocytogenes 08-5923 exposed to sodium lactate and sodium diacetate.

    Science.gov (United States)

    Liu, Xiaoji; Basu, Urmila; Miller, Petr; McMullen, Lynn M

    2017-05-01

    This study reports the gene expression and filamentation in Listeria monocytogenes 08-5923 following exposure to food preservatives sodium lactate (NaL) and sodium diacetate (SD). L. monocytogenes 08-5923 was challenged with a mixture of NaL/SD, NaL or sodium acetate at 37 °C in tryptic soy broth. In the initial study, L. monocytogenes 08-5923 was exposed to NaL/SD for 24 h. The transcriptome was investigated by RNA sequencing. A stress response network was discovered in L. monocytogenes 08-5923, which is mediated by genes encoding two-component systems (hisJ, lisK, OmpR family gene, resE) and RNA polymerase factors (sigC, sigH). NaL/SD resulted in the down-regulation of genes in glycolysis (pykA, eno, fbaA, pgm) and up-regulation of genes in DNA repair (radC), cell division (ftsE) and cell structure synthesis (flagella synthesis: flgK, fliF, fliD). Filamentation was monitored by flow cytometry. NaL/SD mixture resulted in filamentation in L. monocytogenes 08-5923. Longer exposure was required to induce filamentation in L. monocytogenes for SD (24 h) than for NaL (8 h) when cells were exposed to individual salt. The quantitative real time PCR analysis revealed the down-regulation of ftsE in filamented cells of Listeria exposed to NaL or sodium acetate. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Development of multiple strain competitive index assays for Listeria monocytogenes using pIMC; a new site-specific integrative vector

    Directory of Open Access Journals (Sweden)

    Cronin Michael

    2008-06-01

    Full Text Available Abstract Background The foodborne, gram-positive pathogen, Listeria monocytogenes, is capable of causing lethal infections in compromised individuals. In the post genomic era of L. monocytogenes research, techniques are required to identify and validate genes involved in the pathogenicity and environmental biology of the organism. The aim here was to develop a widely applicable method to tag L. monocytogenes strains, with a particular emphasis on the development of multiple strain competitive index assays. Results We have constructed a new site-specific integrative vector, pIMC, based on pPL2, for the selection of L. monocytogenes from complex samples. The pIMC vector was further modified through the incorporation of IPTG inducible markers (antibiotic and phenotypic to produce a suite of four vectors which allowed the discrimination of multiple strains from a single sample. We were able to perform murine infection studies with up to four EGDe isolates within a single mouse and showed that the tags did not impact upon growth rate or virulence. The system also allowed the identification of subtle differences in virulence between strains of L. monocytogenes commonly used in laboratory studies. Conclusion This study has developed a competitive index assay that can be broadly applied to all L. monocytogenes strains. Improved statistical robustness of the data was observed, resulting in fewer mice being required for virulence assays. The competitive index assays provide a powerful method to analyse the virulence or fitness of L. monocytogenes in complex biological samples.

  13. Effect of Listeria seeligeri or Listeria welshimeri on Listeria monocytogenes detection in and recovery from buffered Listeria enrichment broth.

    Science.gov (United States)

    Dailey, Rachel C; Welch, Lacinda J; Hitchins, Anthony D; Smiley, R Derike

    2015-04-01

    The presence of multiple species of Listeria in regulated food products is not uncommon and can complicate the recovery of Listeria monocytogenes particularly on a non-differentiating medium. The potential complications of Listeria seeligeri and Listeria welshimeri on the recovery of L. monocytogenes from inoculated food test samples using the U.S. Food and Drug Administration's (FDA) selective enrichment procedure was investigated. Post-enrichment enumeration, in the absence of food product, indicates that some L. seeligeri and L. monocytogenes pairings may have population differentials as great as 2.7 ± 0.1 logs with L. seeligeri being the predominant species. A similar observation was noted for L. welshimeri and L. monocytogenes pairings which resulted in population differentials as large as 3.7 ± 0.2 logs with L. welshimeri being the predominant species. Select strain pairings were used to inoculate guacamole, crab meat, broccoli, and cheese with subsequent recovery by the FDA Bacteriological Analytical Manual (BAM) method with 10 colonies per sample selected for confirmation. The presence of L. seeligeri had little effect on the recovery of L. monocytogenes. The presence of L. welshimeri resulted in the failure to recover L. monocytogenes in three out of the four food matrices. This work extends the observation that non-pathogenic species of Listeria can complicate the recovery of L. monocytogenes and that competition during selective enrichment is not limited to the presence of just Listeria innocua. Published by Elsevier Ltd.

  14. Effect of Listeria seeligeri or Listeria welshimeri on Listeria monocytogenes detection in and recovery from buffered Listeria enrichment broth☆

    Science.gov (United States)

    Dailey, Rachel C.; Welch, Lacinda J.; Hitchins, Anthony D.; Smiley, R. Derike

    2016-01-01

    The presence of multiple species of Listeria in regulated food products is not uncommon and can complicate the recovery of Listeria monocytogenes particularly on a non-differentiating medium. The potential complications of Listeria seeligeri and Listeria welshimeri on the recovery of L. monocytogenes from inoculated food test samples using the U.S. Food and Drug Administration's (FDA) selective enrichment procedure was investigated. Post-enrichment enumeration, in the absence of food product, indicates that some L. seeligeri and L. monocytogenes pairings may have population differentials as great as 2.7 ± 0.1 logs with L. seeligeri being the predominant species. A similar observation was noted for L. welshimeri and L. monocytogenes pairings which resulted in population differentials as large as 3.7 ± 0.2 logs with L. welshimeri being the predominant species. Select strain pairings were used to inoculate guacamole, crab meat, broccoli, and cheese with subsequent recovery by the FDA Bacteriological Analytical Manual (BAM) method with 10 colonies per sample selected for confirmation. The presence of L. seeligeri had little effect on the recovery of L. monocytogenes. The presence of L. welshimeri resulted in the failure to recover L. monocytogenes in three out of the four food matrices. This work extends the observation that non-pathogenic species of Listeria can complicate the recovery of L. monocytogenes and that competition during selective enrichment is not limited to the presence of just Listeria innocua. PMID:25475325

  15. Modelling and predicting the simultaneous growth of Listeria monocytogenes and spoilage micro-organisms in cold-smoked salmon

    DEFF Research Database (Denmark)

    Gimenez, B.; Dalgaard, Paw

    2004-01-01

    Aims: To evaluate and model the simultaneous growth of Listeria monocytogenes and spoilage micro-organisms in cold-smoked salmon.Methods and Results: Growth kinetics of L. monocytogenes, lactic acid bacteria (LAB), Enterobacteriaceae, enterococci and Photobacterium phosphoreum were determined...

  16. Listeria monocytogenes repellence by enzymatically modified PES surfaces

    NARCIS (Netherlands)

    Veen, van der S.; Nady, N.; Franssen, M.C.R.; Zuilhof, H.; Boom, R.M.; Abee, T.; Schroën, C.G.P.H.

    2015-01-01

    : The effect of enzyme-catalyzed modification of poly(ethersulfone) (PES) on the adhesion and biofilm formation of two Listeria monocytogenes strains is evaluated under static and dynamic flow conditions. PES has been modified with gallic acid, ferulic acid and 4-hydroxybenzoic acid. The surfaces

  17. 9 CFR 430.4 - Control of Listeria monocytogenes in post-lethality exposed ready-to-eat products.

    Science.gov (United States)

    2010-01-01

    ... post-lethality exposed ready-to-eat products. 430.4 Section 430.4 Animals and Animal Products FOOD... Control of Listeria monocytogenes in post-lethality exposed ready-to-eat products. (a) Listeria... comes into direct contact with a food contact surface which is contaminated with L. monocytogenes. (b...

  18. Self-contained chlorine dioxide generation and delivery pods for controlling Listeria monocytogenes in model floor drains.

    Science.gov (United States)

    Listeria monocytogenes is a foodborne pathogen that has been associated with poultry products. This organism is ubiquitous in nature and has been found to enter poultry further processing plants on incoming raw product. Once in the plant, L. monocytogenes can become a long term persistent colonize...

  19. Evaluation of bacteriocin-producing Lactobacillus sakei 1 against Listeria monocytogenes 1/2a growth and haemolytic activity Avaliação de Lactobacillus sakei 1 produtor de bacteriocina frente a Listeria monocytogenes 1/2a e sua atividade hemolítica

    Directory of Open Access Journals (Sweden)

    Rafael C.R. Martinez

    2005-03-01

    Full Text Available Bacteriocin-producing Lactobacillus sakei 1 was cultivated in Brain-Heart Infusion broth (24 h at 25ºC. The culture supernatant was neutralized, filter sterilized and used to test the activity of bacteriocin against Listeria monocytogenes 1/2a, at 8ºC and 15ºC. Non-bacteriocinogenic Lactobacillus sakei ATCC 15521 was used as a negative control. L. monocytogenes 1/2a was inoculated in culture supernatant medium from L. sakei 1 and L. sakei ATCC 15521 and the listerial populations were determined after 0, 5 and 10 days. The bacteriocin production was quantified as arbitrary units per mL (AU/mL using agar antagonism test. Additionally, to investigate if L. monocytogenes virulence pattern could be changed after bactericion exposure, the ability of L. monocytogenes to cause haemolysis in sheep red blood cells was determined, before and after exposure to bacteriocin at 8ºC. In the presence of the antimicrobial peptide, at 8ºC, L. monocytogenes population decreased, but growth of resistant cells was observed. At 15ºC, there was no difference between test and control. Furthermore, the haemolytic activity of L. monocytogenes 1/2a was not altered by exposure to L. sakei 1 bacteriocin, which suggests no change in its virulence pattern.Lactobacillus sakei 1 produtor de bacteriocina foi cultivado em caldo Infusão Cérebro-Coração por 24h a 25ºC. O sobrenadante da cultura foi neutralizado, esterilizado por filtração e usado para testar a atividade da bacteriocina frente a Listeria monocytogenes 1/2a, a 8ºC e 15ºC. Lactobacillus sakei ATCC 15521 não bacteriocinogênico, foi utilizado como controle negativo. L. monocytogenes 1/2a foi inoculada no sobrenadante da cultura de L.sakei 1 e L. sakei ATCC 15521 e as populações listeriais foram determinadas após 0, 5 e 10 dias. A produção de bacteriocina foi quantificada como unidades arbitrárias por mL (UA/mL, utilizando-se o teste de antagonismo em ágar. Adicionalmente, para investigar se o padr

  20. Modeling and predicting the growth boundary of Listeria monocytogenes in lightly preserved seafood

    DEFF Research Database (Denmark)

    Mejlholm, Ole; Dalgaard, Paw

    2007-01-01

    The antimicrobial effect of diacetate and lactate against Listeria monocytogenes was evaluated in challenge tests with vacuum-packaged or modified atmosphere packaged (MAP) cold-smoked salmon, marinated salmon, cold-smoked Greenland halibut, marinated Greenland halibut, and gravad salmon. MAP col...... characteristics required to prevent the growth of L. monocytogenes, thereby making it possible to identify critical control points, and is useful for compliance with the new European Union regulation on ready-to-eat foods (EC 2073/2005)....

  1. Changes in gene expression during adaptation of Listeria monocytogenes to the soil environment.

    Science.gov (United States)

    Piveteau, Pascal; Depret, Géraldine; Pivato, Barbara; Garmyn, Dominique; Hartmann, Alain

    2011-01-01

    Listeria monocytogenes is a ubiquitous opportunistic pathogen responsible for listeriosis. In order to study the processes underlying its ability to adapt to the soil environment, whole-genome arrays were used to analyse transcriptome modifications 15 minutes, 30 minutes and 18 h after inoculation of L. monocytogenes EGD-e in soil extracts. Growth was observed within the first day of incubation and large numbers were still detected in soil extract and soil microcosms one year after the start of the experiment. Major transcriptional reprofiling was observed. Nutrient acquisition mechanisms (phosphoenolpyruvate-dependent phosphotransferase systems and ABC transporters) and enzymes involved in catabolism of specific carbohydrates (β-glucosidases; chitinases) were prevalent. This is consistent with the overrepresentation of the CodY regulon that suggests that in a nutrient depleted environment, L. monocytogenes recruits its extensive repertoire of transporters to acquire a range of substrates for energy production.

  2. Visualization of gold and platinum nanoparticles interacting with Salmonella Enteritidis and Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Ewa Sawosz

    2010-08-01

    Full Text Available Ewa Sawosz1, André Chwalibog2, Jacek Szeliga3, Filip Sawosz2, Marta Grodzik1, Marlena Rupiewicz1, Tomasz Niemiec1, Katarzyna Kacprzyk11Division of Biotechnology and Biochemistry of Nutrition, Warsaw University of Life Sciences, Warsaw, Poland; 2Department of Basic Animal and Veterinary Sciences, University of Copenhagen, Copenhagen, Denmark; 3Division of Microbiology of Analytical Centre, Warsaw University of Life Sciences, Warsaw, PolandPurpose: Rapid development of nanotechnology has recently brought significant attention to the extraordinary biological features of nanomaterials. The objective of the present ­investigation was to evaluate morphological characteristics of the assembles of gold and platinum nanoparticles (nano-Au and nano-Pt respectively, with Salmonella Enteritidis (Gram-negative and Listeria monocytogenes (Gram-positive, to reveal possibilities of constructing bacteria-nanoparticle vehicles.Methods: Hydrocolloids of nano-Au or nano-Pt were added to two bacteria suspensions in the following order: nano-Au + Salmonella Enteritidis; nano-Au + Listeria monocytogenes; nano-Pt + Salmonella Enteritidis; nano-Pt + Listeria monocytogenes. Samples were inspected by transmission electron microscope.Results: Visualization of morphological interaction between nano-Au and Salmonella Enteritidis and Listeria monocytogenes, showed that nano-Au were aggregated within flagella or biofilm network and did not penetrate the bacterial cell. The analysis of morphological effects of interaction of nano-Pt with bacteria revealed that nano-Pt entered cells of Listeria monocytogenes and were removed from the cells. In the case of Salmonella Enteritidis, nano-Pt were seen inside bacteria cells, probably bound to DNA and partly left bacterial cells. After washing and centrifugation, some of the nano-Pt-DNA complexes were observed within Salmonella Enteritidis.Conclusion: The results indicate that the bacteria could be used as a vehicle to deliver nano

  3. Important vectors for Listeria monocytogenes transmission at farm dairies manufacturing fresh sheep and goat cheese from raw milk.

    Science.gov (United States)

    Schoder, Dagmar; Melzner, Daniela; Schmalwieser, Alois; Zangana, Abdoulla; Winter, Petra; Wagner, Martin

    2011-06-01

    The aim of this study was to determine the transmission routs of Listeria spp. in dairy farms manufacturing fresh cheese made from ovine and caprine raw milk and to evaluate the impact of Listeria monocytogenes mastitis on raw milk contamination. Overall, 5,799 samples, including 835 environmental samples, 230 milk and milk product samples, and 4,734 aseptic half-udder foremilk samples were collected from 53 dairy farms in the dairy intensive area of Lower Austria. Farms were selected for the study because raw milk was processed to cheese that was sold directly to consumers. A total of 153 samples were positive for Listeria spp., yielding an overall prevalence of 2.6%; L. monocytogenes was found in 0.9% of the samples. Bulk tank milk, cheese, and half-udder samples were negative for Listeria spp. Because none of the sheep and goats tested positive from udder samples, L. monocytogenes mastitis was excluded as a significant source of raw milk contamination. L. monocytogenes was detected at 30.2% of all inspected farms. Swab samples from working boots and fecal samples had a significantly higher overall prevalence (P < 0.001) of L. monocytogenes (15.7 and 13.0%, respectively) than did swab samples from the milk processing environment (7.9%). A significant correlation was found between the prevalence of L. monocytogenes in the animal and in the milk processing environment and the silage feeding practices. Isolation of L. monocytogenes was three to seven times more likely from farms where silage was fed to animals throughout the year than from farms where silage was not fed to the animals.

  4. Adaptation of Listeria monocytogenes in a simulated cheese medium: effects on virulence using the Galleria mellonella infection model.

    Science.gov (United States)

    Schrama, D; Helliwell, N; Neto, L; Faleiro, M L

    2013-06-01

    The aim of this study was to evaluate the effect of the acid and salt adaptation in a cheese-based medium on the virulence potential of Listeria monocytogenes strains isolated from cheese and dairy processing environment using the Galleria mellonella model. Four L. monocytogenes strains were exposed to a cheese-based medium in conditions of induction of an acid tolerance response and osmotolerance response (pH 5·5 and 3·5% w/v NaCl) and injected in G. mellonella insects. The survival of insects and the L. monocytogenes growth kinetics in insects were evaluated. The gene expression of hly, actA and inlA genes was determined by real-time PCR. The adapted cells of two dairy strains showed reduced insect mortality (P 0·05) was found between adapted and nonadapted cells. The gene expression results evidenced an overexpression of virulence genes in cheese-based medium, but not in simulated insect-induced conditions. Our results suggest that adaptation to low pH and salt in a cheese-based medium can affect the virulence of L. monocytogenes, but this effect is strain dependent. In this study, the impact of adaptation to low pH and salt in a cheese-based medium on L. monocytogenes virulence was tested using the Wax Moth G. mellonella model. This model allowed the differentiation of the virulence potential between the L. monocytogenes strains. The effect of adaptation on virulence is strain dependent. The G. mellonella model revealed to be a prompt method to test food-related factors on L. monocytogenes virulence. © 2013 The Society for Applied Microbiology.

  5. Listeria monocytogenes isolated in ready-to-eat food in South Bačka region of Vojvodina province, Serbia

    Directory of Open Access Journals (Sweden)

    Gusman Vera

    2014-01-01

    Full Text Available Listeria monocytogenes is pathogenic bacterium that can contaminate food products during and after processing. As ready-to-eat food does not undergo any treatment to ensure its safety before consumption, the risk of foodborne disease must be considered if this pathogen is present in the food. As diseases caused by contaminated food are an important public health problem today, the aim of this study was to determine the prevalence of Listeria monocytogenes in different ready-to-eat food products. In the seven-month period from June 1 to December 31, 2011, a total of 1 380 food samples were examined in the Division of Sanitary Bacteriology, Center for Microbiology, Institute of Public Health of Vojvodina in Novi Sad. A total of 912 samples were analyzed for the presence of Listeria monocytogenes according to ISO 11290-2. The identity of suspected Listeria monocytogenes was confirmed using the VITEK 2 Compact system (BioMerieux, France. Out of 912 samples, Listeria monocytogenes was detected in 18 (1.97%. Listeria monocytogenes was mostly found in cooked meals (in 6 samples out of 18, sandwiches (4 samples and frozen food, such as ice-cream and frozen vegetables (4 samples. It was also found in tofu bread spreads (2 samples, cream cheese (1 sample and cakes (1 sample. The presence of Listeria monocytogenes in some ready-to-eat food could present a public health hazard, particularly to the high-risk population group, because of the high mortality rate associated with listeriosis and the widespread nature of the organism. Monitoring of listeriosis is essential to prevent foodborne outbreaks, and in assessing human health risk in ready-to-eat foods.

  6. Tolerance to quaternary ammonium compound disinfectants may enhance growth of Listeria monocytogenes in the food industry.

    Science.gov (United States)

    Møretrø, Trond; Schirmer, Bjørn C T; Heir, Even; Fagerlund, Annette; Hjemli, Pernille; Langsrud, Solveig

    2017-01-16

    The antibacterial effect of disinfectants is crucial for the control of Listeria monocytogenes in food processing environments. Tolerance of L. monocytogenes to sublethal levels of disinfectants based on quaternary ammonium compounds (QAC) is conferred by the resistance determinants qacH and bcrABC. The presence and distribution of these genes have been anticipated to have a role in the survival and growth of L. monocytogenes in food processing environments where QAC based disinfectants are in common use. In this study, a panel of 680 L. monocytogenes from nine Norwegian meat- and salmon processing plants were grouped into 36 MLVA profiles. The presence of qacH and bcrABC was determined in 101 isolates from the 26 most common MLVA profiles. Five MLVA profiles contained qacH and two contained bcrABC. Isolates with qacH and bcrABC showed increased tolerance to the QAC Benzalkonium chloride (BC), with minimal inhibitory concentrations (MICs) of 5-12, 10-13 and 100ppm). A sample with lower BC concentrations (14ppm of chain length C-12 and 2.7ppm of chain length C-14) inhibited growth of L. monocytogenes not containing bcrABC or qacH, compared to strains with these genes. The study has shown that L. monocytogenes harbouring the QAC resistance genes qacH and bcrABC are prevalent in the food industry and that residuals of QAC may be present in concentrations after sanitation in the industry that result in a growth advantage for bacteria with such resistance genes. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  7. Characterization and antibiotic susceptibility of Listeria monocytogenes isolated from poultry and red meat in Morocco

    Directory of Open Access Journals (Sweden)

    Hayat Ennaji

    2008-09-01

    Full Text Available Hayat Ennaji1,2, Mohammed Timinouni2, My Mustapha Ennaji3, Mohammed Hassar1, Nozha Cohen11Laboratoire de Microbiologie et Hygiène des Aliments et de l’Environnement, Institut Pasteur du Maroc., Casablanca, Morocco; 2Laboratoire de Microbiologie et Biologie Moléculaire, Institut Pasteur du Maroc., Casablanca, Morocco; 3Laboratoire de Virologie et Hygiène and Microbiologie., Faculté des Sciences et Techniques - Mohammedia, Université Hassan II, Mohammedia, MoroccoAbstract: This study was carried out on 426 samples of raw meats collected from butcheries and supermarkets in Casablanca, Morocco. The samples were examined for the occurrence of Listeria species. Strains of Listeria monocytogenes were characterized by several biochemical tests and confirmed by polymerase chain reaction (PCR. β-hemolytic cultures and nonhemolytic isolates were tested for biochemical properties with the Listeria API test. Among the 43 Listeria species isolates; we identified 10 strains for L. monocytogenes (23.3%, 31 strains for L. innocua (72.1% and 2 strains for L. welshimeri (4.6%. Strains of L. monocytogenes were separated by multiplex PCR; two serogroups IIb and IVb were thus differentiated. Antibiotic susceptibility of L. monocytogenes to 21 antibiotics was determined by the disk diffusion method. All isolates were susceptible to a wide range of the tested antibiotics with the exception of nalidixic acid, colistine and cephalosporins second and third generation for which they were all resistant.Keywords: antibiotic susceptibility, Listeria monocytogenes, meat, PCR

  8. Effect of gamma-irradiation on the survival of Listeria monocytogenes and allergenicity of cherry tomatoes

    International Nuclear Information System (INIS)

    Todoriki, Setsuko; Bari, Latiful; Kitta, Kazumi; Ohba, Mika; Ito, Yasuhiro; Tsujimoto, Yuka; Kanamori, Norihito; Yano, Erika; Moriyama, Tatsuya; Kawamura, Yukio; Kawamoto, Shinichi

    2009-01-01

    The presence of Listeria monocytogenes in fresh produce is a growing concern because of the possibility of food-borne illness. Ionizing radiation is an effective non-thermal means of eliminating pathogenic bacteria in fresh produce; however, the effect of ionizing irradiation on the allergenic properties of the host commodities remains unknown. This study aimed (i) to determine the effective dose of gamma-irradiation in eliminating L. monocytogenes on whole cherry tomatoes and (ii) to evaluate the effect of gamma-irradiation on the allergenic properties of tomato proteins. Cherry tomatoes that were inoculated with a mixture of five L. monocytogenes strains were treated with gamma-rays from a 60 Co source. A 1.25 kGy dose of gamma-irradiation was found to be sufficient to eliminate L. monocytogenes on whole cherry tomatoes. The immunoblot profile of serum samples obtained from two patients with tomato allergy revealed that gamma-irradiation did not affect the allergenicity of tomato proteins for up to 7 days after irradiation when the tomatoes were stored at 20 deg. C. Additionally, the m-RNA levels of β-fructofuranosidase, polygalacturonase, pectin esterase, and superoxide dismutase, the main allergenic proteins in tomato, were not affected by the applied irradiation dose. Thus, this study demonstrated that a 1.25 kGy dose of gamma-irradiation effectively eliminates L. monocytogenes on cherry tomatoes without affecting the expression of allergenic proteins in the fruits.

  9. Effect of gamma-irradiation on the survival of Listeria monocytogenes and allergenicity of cherry tomatoes

    Science.gov (United States)

    Todoriki, Setsuko; Bari, Latiful; Kitta, Kazumi; Ohba, Mika; Ito, Yasuhiro; Tsujimoto, Yuka; Kanamori, Norihito; Yano, Erika; Moriyama, Tatsuya; Kawamura, Yukio; Kawamoto, Shinichi

    2009-07-01

    The presence of Listeria monocytogenes in fresh produce is a growing concern because of the possibility of food-borne illness. Ionizing radiation is an effective non-thermal means of eliminating pathogenic bacteria in fresh produce; however, the effect of ionizing irradiation on the allergenic properties of the host commodities remains unknown. This study aimed (i) to determine the effective dose of gamma-irradiation in eliminating L. monocytogenes on whole cherry tomatoes and (ii) to evaluate the effect of gamma-irradiation on the allergenic properties of tomato proteins. Cherry tomatoes that were inoculated with a mixture of five L. monocytogenes strains were treated with gamma-rays from a 60Co source. A 1.25 kGy dose of gamma-irradiation was found to be sufficient to eliminate L. monocytogenes on whole cherry tomatoes. The immunoblot profile of serum samples obtained from two patients with tomato allergy revealed that gamma-irradiation did not affect the allergenicity of tomato proteins for up to 7 days after irradiation when the tomatoes were stored at 20 °C. Additionally, the m-RNA levels of β-fructofuranosidase, polygalacturonase, pectin esterase, and superoxide dismutase, the main allergenic proteins in tomato, were not affected by the applied irradiation dose. Thus, this study demonstrated that a 1.25 kGy dose of gamma-irradiation effectively eliminates L. monocytogenes on cherry tomatoes without affecting the expression of allergenic proteins in the fruits.

  10. Effect of gamma-irradiation on the survival of Listeria monocytogenes and allergenicity of cherry tomatoes

    Energy Technology Data Exchange (ETDEWEB)

    Todoriki, Setsuko [National Food Research Institute, Tsukuba, Ibaraki 305-8642 (Japan)], E-mail: setsuko@affrc.go.jp; Bari, Latiful; Kitta, Kazumi; Ohba, Mika; Ito, Yasuhiro; Tsujimoto, Yuka [National Food Research Institute, Tsukuba, Ibaraki 305-8642 (Japan); Kanamori, Norihito [Japan International Research Center for Agricultural Science, Tsukuba, Ibaraki 305-8686 (Japan); Yano, Erika; Moriyama, Tatsuya; Kawamura, Yukio [School of Agriculture, Kinki University, Nara-city, Nara 631-8505 (Japan); Kawamoto, Shinichi [National Food Research Institute, Tsukuba, Ibaraki 305-8642 (Japan)

    2009-07-15

    The presence of Listeria monocytogenes in fresh produce is a growing concern because of the possibility of food-borne illness. Ionizing radiation is an effective non-thermal means of eliminating pathogenic bacteria in fresh produce; however, the effect of ionizing irradiation on the allergenic properties of the host commodities remains unknown. This study aimed (i) to determine the effective dose of gamma-irradiation in eliminating L. monocytogenes on whole cherry tomatoes and (ii) to evaluate the effect of gamma-irradiation on the allergenic properties of tomato proteins. Cherry tomatoes that were inoculated with a mixture of five L. monocytogenes strains were treated with gamma-rays from a {sup 60}Co source. A 1.25 kGy dose of gamma-irradiation was found to be sufficient to eliminate L. monocytogenes on whole cherry tomatoes. The immunoblot profile of serum samples obtained from two patients with tomato allergy revealed that gamma-irradiation did not affect the allergenicity of tomato proteins for up to 7 days after irradiation when the tomatoes were stored at 20 deg. C. Additionally, the m-RNA levels of {beta}-fructofuranosidase, polygalacturonase, pectin esterase, and superoxide dismutase, the main allergenic proteins in tomato, were not affected by the applied irradiation dose. Thus, this study demonstrated that a 1.25 kGy dose of gamma-irradiation effectively eliminates L. monocytogenes on cherry tomatoes without affecting the expression of allergenic proteins in the fruits.

  11. Rapid detection of Listeria monocytogenes in milk using confocal micro-Raman spectroscopy and chemometric analysis.

    Science.gov (United States)

    Wang, Junping; Xie, Xinfang; Feng, Jinsong; Chen, Jessica C; Du, Xin-jun; Luo, Jiangzhao; Lu, Xiaonan; Wang, Shuo

    2015-07-02

    Listeria monocytogenes is a facultatively anaerobic, Gram-positive, rod-shape foodborne bacterium causing invasive infection, listeriosis, in susceptible populations. Rapid and high-throughput detection of this pathogen in dairy products is critical as milk and other dairy products have been implicated as food vehicles in several outbreaks. Here we evaluated confocal micro-Raman spectroscopy (785 nm laser) coupled with chemometric analysis to distinguish six closely related Listeria species, including L. monocytogenes, in both liquid media and milk. Raman spectra of different Listeria species and other bacteria (i.e., Staphylococcus aureus, Salmonella enterica and Escherichia coli) were collected to create two independent databases for detection in media and milk, respectively. Unsupervised chemometric models including principal component analysis and hierarchical cluster analysis were applied to differentiate L. monocytogenes from Listeria and other bacteria. To further evaluate the performance and reliability of unsupervised chemometric analyses, supervised chemometrics were performed, including two discriminant analyses (DA) and soft independent modeling of class analogies (SIMCA). By analyzing Raman spectra via two DA-based chemometric models, average identification accuracies of 97.78% and 98.33% for L. monocytogenes in media, and 95.28% and 96.11% in milk were obtained, respectively. SIMCA analysis also resulted in satisfied average classification accuracies (over 93% in both media and milk). This Raman spectroscopic-based detection of L. monocytogenes in media and milk can be finished within a few hours and requires no extensive sample preparation. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Overlevingsstrategieën Listeria monocytogenes bij lage temperatuur

    NARCIS (Netherlands)

    Wemekamp-Kamphuis, H.H.; Abee, T.

    2004-01-01

    Listeria monocytogenes is an important food-borne pathogen that may cause severe infections in humans. Many outbreaks caused by this organism have been associated with ready-to-eat foods wich may have undergone some form of minimal processing, or have been contaminated after processing. Ready-to-eat

  13. Incidence of Listeria monocytogenes and Other Bacteria in ...

    African Journals Online (AJOL)

    Prof. Ogunji

    Abstract. The involvement of Listeria monocytogenes in spontaneous abortion in Jos was investigated. One hundred blood and 100 placenta samples were collected from spontaneous abortion patients in Jos. The samples were inoculated first into Listeria enrichment broth. Incubation was at 37o C, followed by cold ...

  14. Genotypes Associated with Listeria monocytogenes Isolates Displaying Impaired or Enhanced Tolerances to Cold, Salt, Acid, or Desiccation Stress

    Science.gov (United States)

    Hingston, Patricia; Chen, Jessica; Dhillon, Bhavjinder K.; Laing, Chad; Bertelli, Claire; Gannon, Victor; Tasara, Taurai; Allen, Kevin; Brinkman, Fiona S. L.; Truelstrup Hansen, Lisbeth; Wang, Siyun

    2017-01-01

    The human pathogen Listeria monocytogenes is a large concern in the food industry where its continuous detection in food products has caused a string of recalls in North America and Europe. Most recognized for its ability to grow in foods during refrigerated storage, L. monocytogenes can also tolerate several other food-related stresses with some strains possessing higher levels of tolerances than others. The objective of this study was to use a combination of phenotypic analyses and whole genome sequencing to elucidate potential relationships between L. monocytogenes genotypes and food-related stress tolerance phenotypes. To accomplish this, 166 L. monocytogenes isolates were sequenced and evaluated for their ability to grow in cold (4°C), salt (6% NaCl, 25°C), and acid (pH 5, 25°C) stress conditions as well as survive desiccation (33% RH, 20°C). The results revealed that the stress tolerance of L. monocytogenes is associated with serotype, clonal complex (CC), full length inlA profiles, and the presence of a plasmid which was identified in 55% of isolates. Isolates with full length inlA exhibited significantly (p monocytogenes sequence types, a new inlA PMSC, and several connections between CCs and the presence/absence or variations of specific genetic elements. A whole genome single-nucleotide-variants phylogeny revealed sporadic distribution of tolerant isolates and closely related sensitive and tolerant isolates, highlighting that minor genetic differences can influence the stress tolerance of L. monocytogenes. Specifically, a number of cold and desiccation sensitive isolates contained PMSCs in σB regulator genes (rsbS, rsbU, rsbV). Collectively, the results suggest that knowing the sequence type of an isolate in addition to screening for the presence of full-length inlA and a plasmid, could help food processors and food agency investigators determine why certain isolates might be persisting in a food processing environment. Additionally, increased

  15. Genetic Separation of Listeria monocytogenes Causing Central Nervous System Infections in Animals

    Directory of Open Access Journals (Sweden)

    Lisandra Aguilar-Bultet

    2018-02-01

    Full Text Available Listeria monocytogenes is a foodborne pathogen that causes abortion, septicemia, gastroenteritis and central nervous system (CNS infections in ruminants and humans. L. monocytogenes strains mainly belong to two distinct phylogenetic groups, named lineages I and II. In general, clinical cases in humans and animals, in particular CNS infections, are caused by lineage I strains, while most of the environmental and food strains belong to lineage II. Little is known about why lineage I is more virulent than lineage II, even though various molecular factors and mechanisms associated with pathogenesis are known. In this study, we have used a variety of whole genome sequence analyses and comparative genomic tools in order to find characteristics that distinguish lineage I from lineage II strains and CNS infection strains from non-CNS strains. We analyzed 225 strains and identified single nucleotide variants between lineages I and II, as well as differences in the gene content. Using a novel approach based on Reads Per Kilobase per Million Mapped (RPKM, we identified 167 genes predominantly absent in lineage II but present in lineage I. These genes are mostly encoding for membrane-associated proteins. Additionally, we found 77 genes that are largely absent in the non-CNS associated strains, while 39 genes are especially lacking in our defined “non-clinical” group. Based on the RPKM analysis and the metadata linked to the L. monocytogenes strains, we identified 6 genes potentially associated with CNS cases, which include a transcriptional regulator, an ABC transporter and a non-coding RNA. Although there is not a clear separation between pathogenic and non-pathogenic strains based on phylogenetic lineages, the presence of the genes identified in our study reveals potential pathogenesis traits in ruminant L. monocytogenes strains. Ultimately, the differences that we have found in our study will help steer future studies in understanding the virulence

  16. Genetic Separation of Listeria monocytogenes Causing Central Nervous System Infections in Animals

    Science.gov (United States)

    Aguilar-Bultet, Lisandra; Nicholson, Pamela; Rychener, Lorenz; Dreyer, Margaux; Gözel, Bulent; Origgi, Francesco C.; Oevermann, Anna; Frey, Joachim; Falquet, Laurent

    2018-01-01

    Listeria monocytogenes is a foodborne pathogen that causes abortion, septicemia, gastroenteritis and central nervous system (CNS) infections in ruminants and humans. L. monocytogenes strains mainly belong to two distinct phylogenetic groups, named lineages I and II. In general, clinical cases in humans and animals, in particular CNS infections, are caused by lineage I strains, while most of the environmental and food strains belong to lineage II. Little is known about why lineage I is more virulent than lineage II, even though various molecular factors and mechanisms associated with pathogenesis are known. In this study, we have used a variety of whole genome sequence analyses and comparative genomic tools in order to find characteristics that distinguish lineage I from lineage II strains and CNS infection strains from non-CNS strains. We analyzed 225 strains and identified single nucleotide variants between lineages I and II, as well as differences in the gene content. Using a novel approach based on Reads Per Kilobase per Million Mapped (RPKM), we identified 167 genes predominantly absent in lineage II but present in lineage I. These genes are mostly encoding for membrane-associated proteins. Additionally, we found 77 genes that are largely absent in the non-CNS associated strains, while 39 genes are especially lacking in our defined “non-clinical” group. Based on the RPKM analysis and the metadata linked to the L. monocytogenes strains, we identified 6 genes potentially associated with CNS cases, which include a transcriptional regulator, an ABC transporter and a non-coding RNA. Although there is not a clear separation between pathogenic and non-pathogenic strains based on phylogenetic lineages, the presence of the genes identified in our study reveals potential pathogenesis traits in ruminant L. monocytogenes strains. Ultimately, the differences that we have found in our study will help steer future studies in understanding the virulence mechanisms of the

  17. Survival of Listeria monocytogenes in Soil Requires AgrA-Mediated Regulation.

    Science.gov (United States)

    Vivant, Anne-Laure; Garmyn, Dominique; Gal, Laurent; Hartmann, Alain; Piveteau, Pascal

    2015-08-01

    In a recent paper, we demonstrated that inactivation of the Agr system affects the patterns of survival of Listeria monocytogenes (A.-L. Vivant, D. Garmyn, L. Gal, and P. Piveteau, Front Cell Infect Microbiol 4:160, http://dx.doi.org/10.3389/fcimb.2014.00160). In this study, we investigated whether the Agr-mediated response is triggered during adaptation in soil, and we compared survival patterns in a set of 10 soils. The fate of the parental strain L. monocytogenes L9 (a rifampin-resistant mutant of L. monocytogenes EGD-e) and that of a ΔagrA deletion mutant were compared in a collection of 10 soil microcosms. The ΔagrA mutant displayed significantly reduced survival in these biotic soil microcosms, and differential transcriptome analyses showed large alterations of the transcriptome when AgrA was not functional, while the variations in the transcriptomes between the wild type and the ΔagrA deletion mutant were modest under abiotic conditions. Indeed, in biotic soil environments, 578 protein-coding genes and an extensive repertoire of noncoding RNAs (ncRNAs) were differentially transcribed. The transcription of genes coding for proteins involved in cell envelope and cellular processes, including the phosphotransferase system and ABC transporters, and proteins involved in resistance to antimicrobial peptides was affected. Under sterilized soil conditions, the differences were limited to 86 genes and 29 ncRNAs. These results suggest that the response regulator AgrA of the Agr communication system plays important roles during the saprophytic life of L. monocytogenes in soil. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  18. Uncovering Listeria monocytogenes hypervirulence by harnessing its biodiversity

    Science.gov (United States)

    Charlier, Caroline; Touchon, Marie; Chenal-Francisque, Viviane; Leclercq, Alexandre; Criscuolo, Alexis; Gaultier, Charlotte; Roussel, Sophie; Brisabois, Anne; Disson, Olivier; Rocha, Eduardo P. C.; Brisse, Sylvain; Lecuit, Marc

    2016-01-01

    Microbial pathogenesis studies are typically performed with reference strains, thereby overlooking microbial intra-species virulence heterogeneity. Here we integrated human epidemiological and clinical data with bacterial population genomics to harness the biodiversity of the model foodborne pathogen Listeria monocytogenes and decipher the basis of its neural and placental tropisms. Taking advantage of the clonal structure of this bacterial species, we identify clones epidemiologically associated with either food or human central nervous system (CNS) and maternal-neonatal (MN) listeriosis. The latter are also most prevalent in patients without immunosuppressive comorbidities. Strikingly, CNS and MN clones are hypervirulent in a humanized mouse model of listeriosis. By integrating epidemiological data and comparative genomics, we uncovered multiple novel putative virulence factors and demonstrated experimentally the contribution of the first gene cluster mediating Listeria monocytogenes neural and placental tropisms. This study illustrates the exceptional power of harnessing microbial biodiversity to identify clinically relevant microbial virulence attributes. PMID:26829754

  19. Depletion of proton motive force by nisin in Listeria monocytogenes cells.

    Science.gov (United States)

    Bruno, M E; Kaiser, A; Montville, T J

    1992-07-01

    The basal proton motive force (PMF) levels and the influence of the bacteriocin nisin on the PMF were determined in Listeria monocytogenes Scott A. In the absence of nisin, the interconversion of the pH gradient (Z delta pH) and the membrane potential (delta psi) led to the maintenance of a fairly constant PMF at -160 mV over the external pH range 5.5 to 7.0. The addition of nisin at concentrations of greater than or equal to 5 micrograms/ml completely dissipated PMF in cells at external pH values of 5.5 and 7.0. With 1 microgram of nisin per ml, delta pH was completely dissipated but delta psi decreased only slightly. The action of nisin on PMF in L. monocytogenes Scott A was both time and concentration dependent. Valinomycin depleted only delta pH, whereas nigericin and carbonyl cyanide m-chlorophenylhydrazone depleted only delta psi, under conditions in which nisin depleted both. Four other L. monocytogenes strains had basal PMF parameters similar to those of strain Scott A. Nisin (2.5 micrograms/ml) also completely dissipated PMF in these strains.

  20. Efflux pump-mediated benzalkonium chloride resistance in Listeria monocytogenes isolated from retail food.

    Science.gov (United States)

    Jiang, Xiaobing; Yu, Tao; Liang, Yu; Ji, Shengdong; Guo, Xiaowei; Ma, Jianmin; Zhou, Lijun

    2016-01-18

    In this study, efflux pump-mediated benzalkonium chloride (BC) resistance, including plasmid-encoded (Qac protein family and BcrABC) and chromosome-borne efflux pumps, was investigated in Listeria monocytogenes from retail food in China. Among the 59 L. monocytogenes strains, 13 (22.0%) strains were resistant to BC. The PCR results showed that bcrABC was harbored by 2 of 13 BC resistant strains. However, none of the qac genes were detected among the 59 strains. The bcrABC was absent in both of the plasmid cured strains, indicating that this BC resistance determinant was plasmid-encoded in the two bcrABC-positive strains. In the presence of reserpine, most of the bcrABC-negative strains had decreases in the MICs of BC, suggesting the existence of other efflux pumps and their role in BC resistance. After exposed to reserpine, the reduction in BC MICs was observed in the two cured strains, indicating that efflux pumps located on chromosome was also involved in BC resistance. Our findings suggest that food products may act as reservoirs for BC resistant isolates of L. monocytogenes and plasmid- and chromosome-encoded efflux pumps could mediate the BC resistance of L. monocytogenes, which is especially relevant to the adaption of this organism in food-related environments with frequent BC use. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Modeling the effect of temperature on survival rate of Listeria monocytogenes in yogurt.

    Science.gov (United States)

    Szczawiński, J; Szczawińska, M E; Łobacz, A; Jackowska-Tracz, A

    2016-01-01

    The aim of the study was to (i) evaluate the behavior of Listeria monocytogenes in a commercially produced yogurt, (ii) determine the survival/inactivation rates of L. monocytogenes during cold storage of yogurt and (iii) to generate primary and secondary mathematical models to predict the behavior of these bacteria during storage at different temperatures. The samples of yogurt were inoculated with the mixture of three L. monocytogenes strains and stored at 3, 6, 9, 12 and 15°C for 16 days. The number of listeriae was determined after 0, 1, 2, 3, 5, 7, 9, 12, 14 and 16 days of storage. From each sample a series of decimal dilutions were prepared and plated onto ALOA agar (agar for Listeria according to Ottaviani and Agosti). It was found that applied temperature and storage time significantly influenced the survival rate of listeriae (pbacteria was found in the samples stored at 6°C (D-10 value = 243.9 h), whereas the highest reduction in the number of the bacteria was observed in the samples stored at 15°C (D-10 value = 87.0 h). The number of L. monocytogenes was correlated with the pH value of the samples (pyogurt stored under temperature range from 3 to 15°C, however, the polynomial model gave a better fit to the experimental data.

  2. Genotypes Associated with Listeria monocytogenes Isolates Displaying Impaired or Enhanced Tolerances to Cold, Salt, Acid, or Desiccation Stress

    DEFF Research Database (Denmark)

    Hingston, Patricia A.; Chen, Jessica; Dhillon, Bhavjinder K

    2017-01-01

    elements. A whole genome single-nucleotide-variants phylogeny revealed sporadic distribution of tolerant isolates and closely related sensitive and tolerant isolates, highlighting that minor genetic differences can influence the stress tolerance of L. monocytogenes. Specifically, a number of cold......The human pathogen Listeria monocytogenes is a large concern in the food industry where its continuous detection in food products has caused a string of recalls in North America and Europe. Most recognized for its ability to grow in foods during refrigerated storage, L. monocytogenes can also...... tolerate several other food-related stresses with some strains possessing higher levels of tolerances than others. The objective of this study was to use a combination of phenotypic analyses and whole genome sequencing to elucidate potential relationships between L. monocytogenes genotypes and food...

  3. Complete genome sequence of Listeria monocytogenes strain MR310, isolated from a pastured-flock poultry farm system

    Science.gov (United States)

    Investigation of Listeria monocytogenes transmission from environmental sources associated with pasture-raised chickens to poultry products is needed to determine ways to prevent potential foodborne illness. Here, we report the complete genome sequence of Listeria monocytogenes MR310, one of the iso...

  4. Differential Biofilm Formation and Chemical Disinfection Resistance of Sessile Cells of Listeria monocytogenes Strains under Monospecies and Dual-Species (with Salmonella enterica) Conditions

    Science.gov (United States)

    Kostaki, Maria; Chorianopoulos, Nikos; Braxou, Elli; Nychas, George-John

    2012-01-01

    This study aimed to investigate the possible influence of bacterial intra- and interspecies interactions on the ability of Listeria monocytogenes and Salmonella enterica to develop mixed-culture biofilms on an abiotic substratum, as well as on the subsequent resistance of sessile cells to chemical disinfection. Initially, three strains from each species were selected and left to attach and form biofilms on stainless steel (SS) coupons incubated at 15°C for 144 h, in periodically renewable tryptone soy broth (TSB), under either monoculture or mixed-culture (mono-/dual-species) conditions. Following biofilm formation, mixed-culture sessile communities were subjected to 6-min disinfection treatments with (i) benzalkonium chloride (50 ppm), (ii) sodium hypochlorite (10 ppm), (iii) peracetic acid (10 ppm), and (iv) a mixture of hydrogen peroxide (5 ppm) and peracetic acid (5 ppm). Results revealed that both species reached similar biofilm counts (ca. 105 CFU cm−2) and that, in general, interspecies interactions did not have any significant effect either on the biofilm-forming ability (as this was assessed by agar plating enumeration of the mechanically detached biofilm bacteria) or on the antimicrobial resistance of each individual species. Interestingly, pulsed-field gel electrophoresis (PFGE) analysis clearly showed that the three L. monocytogenes strains did not contribute at the same level either to the formation of mixed-culture sessile communities (mono-/dual species) or to their antimicrobial recalcitrance. Additionally, the simultaneous existence inside the biofilm structure of S. enterica cells seemed to influence the occurrence and resistance pattern of L. monocytogenes strains. In sum, this study highlights the impact of microbial interactions taking place inside a mixed-culture sessile community on both its population dynamics and disinfection resistance. PMID:22307304

  5. Pathogenic potential of Listeria monocytogenes isolated from cattle ...

    African Journals Online (AJOL)

    Listeria monocytogenes is an opportunistic food-borne pathogen causing listeriosis especially among immune-compromised persons. Its high rate of morbidity and mortality has classed the organism among the top watch list in foods. It is known to produce several virulence factors which aid its survival in harsh conditions ...

  6. Incidence of Listeria monocytogenes and Other Bacteria in ...

    African Journals Online (AJOL)

    The involvement of Listeria monocytogenes in spontaneous abortion in Jos was investigated. One hundred blood and 100 placenta samples were collected from spontaneous abortion patients in Jos. The samples were inoculated first into Listeria enrichment broth. Incubation was at 37o C, followed by cold enrichment at ...

  7. Prevalence and antibiotic susceptibility of Listeria monocytogenes in ...

    African Journals Online (AJOL)

    One hundred and ninety two raw milk samples were collected from lactating cows identified in Fulani herds and small scale dairy farms within Sokoto metropolis in order to investigate the presence and determine the antibiotic susceptibility of Listeria monocytogenes in the milk. Selective culture and identification method ...

  8. Listeria monocytogenes meningitis in the Netherlands, 1985-2014: A nationwide surveillance study.

    Science.gov (United States)

    Koopmans, Merel M; Bijlsma, Merijn W; Brouwer, Matthijs C; van de Beek, Diederik; van der Ende, Arie

    2017-07-01

    Listeria monocytogenes can cause sepsis and meningitis. We report national surveillance data on L. monocytogenes meningitis in the Netherlands, describing incidence changes, genetic epidemiology and fatality rate. We analyzed data from the Netherlands Reference Laboratory of Bacterial Meningitis for cases of L. monocytogenes meningitis. Strains were assessed by serotyping and bacterial population structure by multi-locus sequence typing. A total of 375 cases of Listeria meningitis were identified between 1985 and 2014. Peak incidence rates were observed in neonates (0.61 per 100,000 live births) and older adults (peak at 87 year; 0.53 cases per 100,000 population of the same age). Neonatal listerial meningitis decreased 17-fold from 1.95 per 100,000 live births between 1985 and 1989, to 0.11 per 100,000 live births between 2010 and 2014. Overall case fatality rate was 31%, in a multivariate analysis older age and concomitant bacteremia were associated with mortality (both p listeria meningitis has remained high. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  9. Listeria spp. E Listeria monocytogenes NA PRODUÇÃO DE SALSICHAS TIPO HOT DOG

    Directory of Open Access Journals (Sweden)

    ALESSANDRA PARO RODRIGUES CESAR

    2011-06-01

    Full Text Available Listeria monocytogenes is widely distributed in the environment and it has been isolated from food that were associated to outbreaks of high lethality in many countries. Thus, this bacterium represents an important pathogen to the public health. Ready-to-eat products, likecooked stuffed food, within them, frankfurters, are associated to human listeriosis in many countries. Taking into consideration the importance of the subject and the need of more data about it, the occurrence of Listeria spp. and L. monocytogenes in industrial plants, in meat raw materials, in slurry and frankfurters was investigated.These samples were collected in two production plants with SIF (Federal Inspection Service; in one of them GMP, HACCP and SOP were implemented. The results of the 1 06 microbiological analysis were submitted to the program @Risk to obtain the risk analysis; the meanvalues results showed that 7 to 9% of the frankfurters in the market may have L. monocytogenes. The analysis indicated that 88 strains of L. monocytogenes were obtained from 1 06 samples; among them, 76 werecollected in the industrial plants that participate in the experiment, and 30 were collected in the market. In serological typification, 95% of these strains were classified as serotypes 4b, 1 /2a and 1 /2b. Besides the presence of the bacterium in frankfurthers consumed inBrazil and the risk factors associated to this pathogen, the situation concerns because of the lack of epidemiological data, absence of patterns and the deficient information given to the consumer, specially information related to the presence of L. monocytogenes, particularly important to the groups at risk, as well as information related to the importance of heating the product

  10. Prevalence and populations of Listeria monocytogenes in meat products retailed in Sao Paulo, Brazil.

    Science.gov (United States)

    Ristori, Christiane Asturiano; Rowlands, Ruth Estela Gravato; Martins, Cecília Geraldes; Barbosa, Maria Luisa; Yoshida, Júlia T U; Franco, Bernadette D G de Melo

    2014-12-01

    This study evaluated the prevalence of the populations and serotypes of Listeria monocytogenes in 552 refrigerated samples of ground beef, chicken leg, hot dog, and pork sausage collected in supermarkets in the city of Sao Paulo, SP, Brazil, between May 2008 and July 2009. The supermarkets were selected after stratification by geographical region and by random draw. Tests for presence and enumeration of L. monocytogenes were based on ISO 11290-1:1996/Amd.1:2004 and ISO 11290-2:1998 methods, respectively. Listeria spp. were detected in 469 (85.0%) of the studied meat products. The most frequently isolated species was L. innocua (64.1%), followed by L. monocytogenes (48.7%), L. welshimeri (13.4%), L. seeligeri (7.1%), L. ivanovii (0.2%), and L. grayi subspecies murrayi (0.2%). L. monocytogenes was detected in 269 (48.7%) samples, with highest prevalence in ground beef (59.4%) followed by chicken legs (58.0%), pork sausages (39.8%), and hot dogs (37.7%). The populations were Prevalence of serotypes varied according to the type of meat product. These data are relevant for estimating the risks of listeriosis associated with consumption of meat products in Sao Paulo, and for establishing science-based intervention strategies aimed at reducing these risks, especially for pregnant women and immunocompromised individuals.

  11. A Dual Microscopy-Based Assay To Assess Listeria monocytogenes Cellular Entry and Vacuolar Escape.

    Science.gov (United States)

    Quereda, Juan J; Pizarro-Cerdá, Javier; Balestrino, Damien; Bobard, Alexandre; Danckaert, Anne; Aulner, Nathalie; Shorte, Spencer; Enninga, Jost; Cossart, Pascale

    2016-01-01

    Listeria monocytogenes is a Gram-positive bacterium and a facultative intracellular pathogen that invades mammalian cells, disrupts its internalization vacuole, and proliferates in the host cell cytoplasm. Here, we describe a novel image-based microscopy assay that allows discrimination between cellular entry and vacuolar escape, enabling high-content screening to identify factors specifically involved in these two steps. We first generated L. monocytogenes and Listeria innocua strains expressing a β-lactamase covalently attached to the bacterial cell wall. These strains were then incubated with HeLa cells containing the Förster resonance energy transfer (FRET) probe CCF4 in their cytoplasm. The CCF4 probe was cleaved by the bacterial surface β-lactamase only in cells inoculated with L. monocytogenes but not those inoculated with L. innocua, thereby demonstrating bacterial access to the host cytoplasm. Subsequently, we performed differential immunofluorescence staining to distinguish extracellular versus total bacterial populations in samples that were also analyzed by the FRET-based assay. With this two-step analysis, bacterial entry can be distinguished from vacuolar rupture in a single experiment. Our novel approach represents a powerful tool for identifying factors that determine the intracellular niche of L. monocytogenes. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  12. Sublethal injury and virulence changes in Listeria monocytogenes and Listeria innocua treated with antimicrobials carvacrol and citral.

    Science.gov (United States)

    Silva, A; Genovés, S; Martorell, P; Zanini, S F; Rodrigo, D; Martinez, A

    2015-09-01

    The aim of this study was to evaluate the effect of two antimicrobial substances, carvacrol and citral, on Listeria monocytogenes and Listeria innocua cells, as well as possible virulence changes in injured cells, using Caenorhabditis elegans as a model test. The results indicated that the percentage of sublethal damage was higher in L. monocytogenes than in L. innocua. The results of the study carried out by using C. elegans indicated that C. elegans fed in a lawn of L. monocytogenes previously treated with carvacrol showed a loss in life span (p ≤ 0.05) as compared with L. monocytogenes treated with citral, Escherichia coli OP50 as a negative control, and treated and untreated L. innocua. Egg laying was also affected: worms fed in a lawn of treated and untreated L. monocytogenes laid fewer eggs than those fed in a lawn of treated and untreated L. innocua or fed with OP50 as a negative control. Worms fed in a lawn of treated and untreated L. innocua also laid fewer eggs than those fed with OP50 as a negative control. A phenotype named bag of worms and an undescribed new one, "vulva inflammation", were also observed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Monitoring viable cells of the biological control agent Lactobacillus plantarum PM411 in aerial plant surfaces by means of a strain-specific viability quantitative PCR.

    Science.gov (United States)

    Daranas, Núria; Bonaterra, Anna; Francés, Jesús; Cabrefiga, Jordi; Montesinos, Emilio; Badosa, Esther

    2018-03-09

    A viability qPCR (v-qPCR) assay was developed for the unambiguous detection and quantification of Lactobacillus plantarum PM411 viable cells in aerial plant surfaces. A 972 bp region of a PM411 predicted prophage with mosaic architecture enabled the identification of a PM411 strain-specific molecular marker. Three primer sets, with different amplicon lengths (92, 188, and 317 bp), and one TaqMan probe were designed. All the qPCR assays showed good linearity over a 4-log range and good efficiencies, but differed in sensitivity. The nucleic acid-binding dye PEMAX was used for selectively detecting and enumerating viable bacteria by v-qPCR. The primer set amplifying a 188 bp DNA fragment was selected as the most suitable for v-qPCR. The performance of the method was assessed on apple blossoms, pear, strawberry and kiwifruit leaves in potted plants under controlled environmental conditions, and pear and apple blossoms under field conditions, by comparing v-qPCR population estimation to those obtained by qPCR and specific plate counting on MRS-rifampicin. The population estimation did not differ significantly between methods when conditions were conducive to bacterial survival. However, under stressful conditions, differences between methods were observed due to cell death or viable but non-culturable state induction. While qPCR overestimated the population level, plate counting underestimated this value in comparison to v-qPCR. PM411 attained stable population levels of viable cells on flower environment under high relative humidity. However, the unfavourable conditions onto the leaf surface and the relatively dryness in the field caused an important decrease of viable population. IMPORTANCE The v-qPCR method in combination with plate counting and qPCR is a powerful tool for studies of colonization and survival in field conditions, to improve formulations and delivery strategies of PM411, or to optimize the dose and timing of spray schedules. It is expected that PEMAX

  14. Isolation and detection of Listeria monocytogenes in poultry meat by standard culture methods and PCR

    Science.gov (United States)

    Kureljušić, J.; Rokvić, N.; Jezdimirović, N.; Kureljušić, B.; Pisinov, B.; Karabasil, N.

    2017-09-01

    Listeria is the genus of a bacteria found in soil and water and some animals, including poultry and cattle. It can be present in raw milk and food made from raw milk. It can also live in food processing plants and contaminate a variety of processed meats. Microscopically, Listeria species appear as small, Gram-positive rods, which are sometimes arranged in short chains. In direct smears, they can be coccoid, so they can be mistaken for streptococci. Longer cells can resemble corynebacteria. Flagella are produced at room temperature but not at 37°C. Haemolytic activity on blood agar has been used as a marker to distinguish Listeria monocytogenes among other Listeria species, but it is not an absolutely definitive criterion. Further biochemical characterization is necessary to distinguish between the different Listeria species. The objective of this study was to detect, isolate and identify Listeria monocytogenes from poultry meat. Within a period of six months from January to June 2017, a total of 15 samples were collected. Three samples were positive for the presence of Listeria monocytogenes. Biochemical and microbiological tests as well as PCR technique using specific primers were used to confirm L. Monocytogenes in the samples.

  15. Phenotypic and Genotypic Characterization of Atypical Listeria monocytogenes and Listeria innocua Isolated from Swine Slaughterhouses and Meat Markets

    Directory of Open Access Journals (Sweden)

    Luisa Zanolli Moreno

    2014-01-01

    Full Text Available In the last decade, atypical Listeria monocytogenes and L. innocua strains have been detected in food and the environment. Because of mutations in the major virulence genes, these strains have different virulence intensities in eukaryotic cells. In this study, we performed phenotypic and genotypic characterization of atypical L. monocytogenes and L. innocua isolates obtained from swine slaughterhouses and meat markets. Forty strains were studied, including isolates of L. monocytogenes and L. innocua with low-hemolytic activity. The isolates were characterized using conventional phenotypic Listeria identification tests and by the detection and analysis of L. monocytogenes-specific genes. Analysis of 16S rRNA was used for the molecular identification of the Listeria species. The L. monocytogenes isolates were positive for all of the virulence genes studied. The atypical L. innocua strains were positive for hly, plcA, and inlC. Mutations in the InlC, InlB, InlA, PI-PLC, PC-PLC, and PrfA proteins were detected in the atypical isolates. Further in vitro and transcriptomic studies are being developed to confirm the role of these mutations in Listeria virulence.

  16. Different transcriptional responses from slow and fast growth rate strains of Listeria monocytogenes adapted to low temperature

    Directory of Open Access Journals (Sweden)

    Ninoska eCordero

    2016-03-01

    Full Text Available Listeria monocytogenes has become one of the principal foodborne pathogens worldwide. The capacity of this bacterium to grow at low temperatures has opened an interesting field of study in terms of the identification and classification of new strains of L. monocytogenes with different growth capacities at low temperatures. We determined the growth rate at 8 ºC of 110 strains of L. monocytogenes isolated from different food matrices. We identified a group of slow and fast strains according to their growth rate at 8 °C and performed a global transcriptomic assay in strains previously adapted to low temperature. We then identified shared and specific transcriptional mechanisms, metabolic and cellular processes of both groups; bacterial motility was the principal process capable of differentiating the adaptation capacity of L. monocytogenes strains with different ranges of tolerance to low temperatures. Strains belonging to the fast group were less motile, which may allow these strains to achieve a greater rate of proliferation at low temperature.

  17. Effect of pulmonary irradiation from inhaled 90Y on immunity to Listeria monocytogenes in mice

    International Nuclear Information System (INIS)

    Sanchez, A.; Lundgren, D.L.; McClellan, R.O.

    1976-01-01

    The immunological response of mice subjected to irradiation from particles deposited in the lungs and challenged with Listeria monocytogenes was investigated. Mice, exposed by inhalation to 90 Y (a beta-emitting radionuclide) in relatively insoluble fused aluminosilicate particles, were immunized with L. monocytogenes either before or after exposure. Two additional groups of mice were either immunized or irradiated only. A group of control mice received no irradiation or immunization. The beta radiation dose absorbed by the lungs of each mouse at time of challenge averaged 10,000 rads. Fourteen days after immunization, all mice were challenged with 2 LD 50 doses of L. monocytogenes via the respiratory route. Survival of all immunized mice either with or without exposure to 90 Y varied from 90 to 100% as compared to 10 to 20% for the mice irradiated only and for control mice through 14 days after challenge. Pulmonary clearance of inhaled L. monocytogenes during the first 4 hr after challenge was suppressed in the mice irradiated only but not in those immunized only, or in the immunized and irradiated groups, and control mice. There appeared to be a suppression of proliferation of L. monocytogenes in lungs and spleen in the immunized groups 72 hr after challenge, whereas the lungs and spleens of the mice irradiated only and the control mice had extensive bacterial invasion. It was concluded that the 10,000 rads of beta radiation absorbed by the lungs did not suppress the immune mechanisms of the immunized mice

  18. Microbial diversity and structure are drivers of the biological barrier effect against Listeria monocytogenes in soil.

    Science.gov (United States)

    Vivant, Anne-Laure; Garmyn, Dominique; Maron, Pierre-Alain; Nowak, Virginie; Piveteau, Pascal

    2013-01-01

    Understanding the ecology of pathogenic organisms is important in order to monitor their transmission in the environment and the related health hazards. We investigated the relationship between soil microbial diversity and the barrier effect against Listeria monocytogenes invasion. By using a dilution-to-extinction approach, we analysed the consequence of eroding microbial diversity on L. monocytogenes population dynamics under standardised conditions of abiotic parameters and microbial abundance in soil microcosms. We demonstrated that highly diverse soil microbial communities act as a biological barrier against L. monocytogenes invasion and that phylogenetic composition of the community also has to be considered. This suggests that erosion of diversity may have damaging effects regarding circulation of pathogenic microorganisms in the environment.

  19. Use of results of microbiological analyses for risk-based control of Listeria monocytogenes in marinated broiler legs.

    Science.gov (United States)

    Aarnisalo, Kaarina; Vihavainen, Elina; Rantala, Leila; Maijala, Riitta; Suihko, Maija-Liisa; Hielm, Sebastian; Tuominen, Pirkko; Ranta, Jukka; Raaska, Laura

    2008-02-10

    Microbial risk assessment provides a means of estimating consumer risks associated with food products. The methods can also be applied at the plant level. In this study results of microbiological analyses were used to develop a robust single plant level risk assessment. Furthermore, the prevalence and numbers of Listeria monocytogenes in marinated broiler legs in Finland were estimated. These estimates were based on information on the prevalence, numbers and genotypes of L. monocytogenes in 186 marinated broiler legs from 41 retail stores. The products were from three main Finnish producers, which produce 90% of all marinated broiler legs sold in Finland. The prevalence and numbers of L. monocytogenes were estimated by Monte Carlo simulation using WinBUGS, but the model is applicable to any software featuring standard probability distributions. The estimated mean annual number of L. monocytogenes-positive broiler legs sold in Finland was 7.2x10(6) with a 95% credible interval (CI) 6.7x10(6)-7.7x10(6). That would be 34%+/-1% of the marinated broiler legs sold in Finland. The mean number of L. monocytogenes in marinated broiler legs estimated at the sell-by-date was 2 CFU/g, with a 95% CI of 0-14 CFU/g. Producer-specific L. monocytogenes strains were recovered from the products throughout the year, which emphasizes the importance of characterizing the isolates and identifying strains that may cause problems as part of risk assessment studies. As the levels of L. monocytogenes were low, the risk of acquiring listeriosis from these products proved to be insignificant. Consequently there was no need for a thorough national level risk assessment. However, an approach using worst-case and average point estimates was applied to produce an example of single producer level risk assessment based on limited data. This assessment also indicated that the risk from these products was low. The risk-based approach presented in this work can provide estimation of public health risk

  20. Advanced Analysis to Distinguish between Physical Decrease and Inactivation of Viable Phages in Aerosol by Quantitating Phage-Specific Particles.

    Science.gov (United States)

    Shimasaki, Noriko; Nojima, Yasuhiro; Sakakibara, Masaya; Kikuno, Ritsuko; Iizuka, Chiori; Okaue, Akira; Okuda, Shunji; Shinohara, Katsuaki

    2018-01-01

     Recent studies have investigated the efficacy of air-cleaning products against pathogens in the air. A standard method to evaluate the reduction in airborne viruses caused by an air cleaner has been established using a safe bacteriophage instead of pathogenic viruses; the reduction in airborne viruses is determined by counting the number of viable airborne phages by culture, after operating the air cleaner. The reduction in the number of viable airborne phages could be because of "physical decrease" or "inactivation". Therefore, to understand the mechanism of reduction correctly, an analysis is required to distinguish between physical decrease and inactivation. The purpose of this study was to design an analysis to distinguish between the physical decrease and inactivation of viable phi-X174 phages in aerosols. We established a suitable polymerase chain reaction (PCR) system by selecting an appropriate primer-probe set for PCR and validating the sensitivity, linearity, and specificity of the primer-probe set to robustly quantify phi-X174-specific airborne particles. Using this quantitative PCR system and culture assay, we performed a behavior analysis of the phage aerosol in a small chamber (1 m 3 ) at different levels of humidity, as humidity is known to affect the number of viable airborne phages. The results revealed that the reduction in the number of viable airborne phages was caused not only by physical decrease but also by inactivation under particular levels of humidity. Our study could provide an advanced analysis to differentiate between the physical decrease and inactivation of viable airborne phages.

  1. Genomic presence of gadD1 glutamate decarboxylase correlates with the organization of ascB-dapE internalin cluster in Listeria monocytogenes.

    Science.gov (United States)

    Chen, Jianshun; Fang, Chun; Zheng, Tianlun; Zhu, Ningyu; Bei, Yijiang; Fang, Weihuan

    2012-02-01

    The ability to survive and proliferate in acidic environments is a prerequisite for the infection of Listeria monocytogenes. The glutamate decarboxylase (GAD) system is responsible for acid resistance, and three GAD homologs have been identified in L. monocytogenes: gadD1, gadD2, and gadD3. To examine whether GAD genes are specific to lineage, serovar, or certain subpopulation, we performed a systematic investigation on the prevalence of GAD genes in 164 L. monocytogenes. In contrast to gadD2 and gadD3 conserved in all L. monocytogenes strains, gadD1 was identified in 36.6% (60/164) of L. monocytogenes strains, including all serovar 1/2c and 68.5% (37/54) of serovar 1/2a strains, as well as a small fraction of serovar 1/2b (3.4%, 1/29) and lineage III (13.8%, 4/29) strains. All serovar 4b and lineage IV strains lacked this gene. According to the ascB-dapE structure, L. monocytogenes strains were classified into four subpopulations, carrying inlC2DE, inlGC2DE, inlGHE, or no internalin cluster, respectively. All L. monocytogenes strains with inlGC2DE or inlGHE pattern harbored gadD1, whereas those bearing inlC2DE or no internalin cluster between ascB and dapE lacked gadD1. In addition, other five non-monocytogenes Listeria species lacking ascB-dapE internalin cluster were gadD1-negative. Overall, the presence of gadD1 is not fully dependent on lineages or serovars but correlates with ascB-dapE internalin profiles, suggesting gadD1 might have co-evolved with the ascB-dapE internalin cluster in the primitive L. monocytogenes before divergence of serovars.

  2. The effect of milk components and storage conditions on the virulence of Listeria monocytogenes as determined by a Caco-2 cell assay.

    Science.gov (United States)

    Pricope-Ciolacu, Luminita; Nicolau, Anca Ioana; Wagner, Martin; Rychli, Kathrin

    2013-08-16

    Nearly all cases of human listeriosis have been associated with consumption of contaminated food, therefore the investigation of the virulence of Listeria (L.) monocytogenes after exposure to environmental conditions in food matrices is critical in order to understand and control its impact on public health. As milk and dairy products have been implicated in more than half of the listeriosis outbreaks, we investigated the in vitro virulence of L. monocytogenes incubated in different milk types at various storage conditions. Incubation in pasteurized milk at refrigeration conditions (4°C) revealed a higher invasion and intracellular proliferation of four different L. monocytogenes strains compared to raw milk using human intestinal epithelial Caco-2 cells. Furthermore the period of storage, which increased L. monocytogenes cell numbers, decreased in vitro virulence. However, L. monocytogenes stored for 3weeks at 4°C in milk are still able to invade and proliferate into the host cell. Interestingly abused storage temperatures (25°C and 30°C) for a short time period (2h) revealed an attenuated impact on the in vitro virulence of L. monocytogenes compared to the storage temperature of 4°C. Regarding the major milk compounds, the level of milk fat significantly affected the in vitro virulence of L. monocytogenes. Pre-incubation in milk with high fat content (3.6%) resulted in a lower invasion capability compared to milk with low fat content. In contrast casein and lactose did not influence the invasiveness of L. monocytogenes into the host cell. In conclusion our study shows that the milk environment and different storage conditions influence the in vitro virulence of L. monocytogenes, both of which have to be considered in the risk assessment of contaminated food. Copyright © 2013 Elsevier B.V. All rights reserved.

  3. Effect of Listeria monocytogenes inoculation, sodium acetate and ...

    African Journals Online (AJOL)

    Jane

    2011-08-08

    Aug 8, 2011 ... monocytogenes has been isolated from surface fresh waters and ... been reported that contamination of aquatic products with ..... In fish sausage treated with nisin, the peroxide value was lower in comparison with that of control (Raju et al., 2003). TBA assay is usually used as indicator for the assessment of.

  4. Listeria monocytogenes CadC Regulates Cadmium Efflux and Fine-tunes Lipoprotein Localization to Escape the Host Immune Response and Promote Infection.

    Science.gov (United States)

    Pombinho, Rita; Camejo, Ana; Vieira, Ana; Reis, Olga; Carvalho, Filipe; Almeida, Maria Teresa; Pinheiro, Jorge Campos; Sousa, Sandra; Cabanes, Didier

    2017-05-01

    Listeria monocytogenes is a major intracellular human foodborne bacterial pathogen. We previously revealed L. monocytogenes cadC as highly expressed during mouse infection. Here we show that L. monocytogenes CadC is a sequence-specific, DNA-binding and cadmium-dependent regulator of CadA, an efflux pump conferring cadmium resistance. CadC but not CadA is required for L. monocytogenes infection in vivo. Interestingly, CadC also directly represses lspB, a gene encoding a lipoprotein signal peptidase whose expression appears detrimental for infection. lspB overexpression promotes the release of the LpeA lipoprotein to the extracellular medium, inducing tumor necrosis factor α and interleukin 6 expression, thus impairing L. monocytogenes survival in macrophages. We propose that L. monocytogenes uses CadC to repress lspB expression during infection to avoid LpeA exposure to the host immune system, diminishing inflammatory cytokine expression and promoting intramacrophagic survival and virulence. CadC appears as the first metal efflux pump regulator repurposed during infection to fine-tune lipoprotein processing and host responses. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.

  5. Listeria monocytogenes incidence changes and diversity in some Brazilian dairy industries and retail products

    DEFF Research Database (Denmark)

    Oxaran, Virginie; In Lee, Sarah Hwa; Chaul, Luiza Toubas

    2017-01-01

    the incidence of L. monocytogenes in five dairies and retail products in the Southeast and Midwest regions of Brazil over eight months. Of 437 samples, three samples (0.7%) from retail and only one sample (0.2%) from the dairies were positive for L. monocytogenes. Thus, the contamination rate was significantly...... reduced as compared to previous studies. MultiLocus Sequence Typing (MLST) was used to determine if contamination was caused by new or persistent clones leading to the first MLST profile of L. monocytogenes from the Brazilian dairy industry. The processing environment isolate is of concern being...... a sequence-type (ST) 2, belonging to the lineage I responsible for the majority of listeriosis outbreaks. Also, ST3 and ST8 found in commercialized cheese have previously been reported in outbreaks. Despite the lower incidence, dairy products still pose a potential health risk and the occurrence of L...

  6. Infectious Dose of Listeria monocytogenes in Outbreak Linked to Ice Cream, United States, 2015.

    Science.gov (United States)

    Pouillot, Régis; Klontz, Karl C; Chen, Yi; Burall, Laurel S; Macarisin, Dumitru; Doyle, Matthew; Bally, Kären M; Strain, Errol; Datta, Atin R; Hammack, Thomas S; Van Doren, Jane M

    2016-12-01

    The relationship between the number of ingested Listeria monocytogenes cells in food and the likelihood of developing listeriosis is not well understood. Data from an outbreak of listeriosis linked to milkshakes made from ice cream produced in 1 factory showed that contaminated products were distributed widely to the public without any reported cases, except for 4 cases of severe illness in persons who were highly susceptible. The ingestion of high doses of L. monocytogenes by these patients infected through milkshakes was unlikely if possible additional contamination associated with the preparation of the milkshake is ruled out. This outbreak illustrated that the vast majority of the population did not become ill after ingesting a low level of L. monocytogenes but raises the question of listeriosis cases in highly susceptible persons after distribution of low-level contaminated products that did not support the growth of this pathogen.

  7. Characterization of virulent Listeria monocytogenes isolates recovered from ready-to-eat meat products and consumers in Cairo, Egypt

    Directory of Open Access Journals (Sweden)

    Maysa A. I. Awadallah

    2014-10-01

    Full Text Available Aim: This study aimed to investigate the occurrence of some virulence genes distributed in Listeria monocytogenes isolated from ready-to-eat (RTE meat products and consumers in Cairo province, Egypt. Materials and Methods: A total of 120 beef luncheon, chicken luncheon and frankfurter beef (40 samples, each were collected from 10 different local shops situated in Al-salam city, Cairo province, Egypt. Stool samples were collected from 40 people who had the habit of consuming RTE meat. The suspected L. monocytogenes isolates were subjected to a multiplex polymerase chain reaction (PCR for rapid speciation and virulence determination using primers specific for inIA, inIC, and inIJ genes. Results: Culture examination of all samples on Oxford media revealed presence of colonies characteristic to L. monocytogenes in 6 beef luncheon (15%, 4 chicken luncheon (10%, 1 frankfurter beef (2.5% and 1 human stool (2.5% samples. Species identity of L. monocytogenes was verified through the amplification of a 800 bp fragment with inIA primers in 2 out of 6 culture isolates from beef luncheon (5%, and 1 out 4 culture isolates from chicken luncheon (2.5% samples. Statistical analysis revealed no significant difference between the occurrence of L. monocytogenes in different food samples examined (p>0.05. The virulence of these strains was ascertained by the presence of 517 bp and 238 bp fragments of inIC and inIJ genes, respectively in the isolates that contained the 800 bp fragment. The culture isolates obtained from one frankfurter beef sample, and one human stool sample were found negative by multiplex PCR for the presence of L. monocytogenes and its virulence specific genes. Conclusion: It could be concluded that L. monocytogenes are circulating in beef and chicken luncheon sold in Cairo, Egypt. Multiplex PCR is reliable for confirmation of L. monocytogenes. This study suggests the implementation of hygienic measures at all levels from production to consumption

  8. Validation of a Previously Developed Geospatial Model That Predicts the Prevalence of Listeria monocytogenes in New York State Produce Fields

    Science.gov (United States)

    Weller, Daniel; Shiwakoti, Suvash; Bergholz, Peter; Grohn, Yrjo; Wiedmann, Martin

    2015-01-01

    Technological advancements, particularly in the field of geographic information systems (GIS), have made it possible to predict the likelihood of foodborne pathogen contamination in produce production environments using geospatial models. Yet, few studies have examined the validity and robustness of such models. This study was performed to test and refine the rules associated with a previously developed geospatial model that predicts the prevalence of Listeria monocytogenes in produce farms in New York State (NYS). Produce fields for each of four enrolled produce farms were categorized into areas of high or low predicted L. monocytogenes prevalence using rules based on a field's available water storage (AWS) and its proximity to water, impervious cover, and pastures. Drag swabs (n = 1,056) were collected from plots assigned to each risk category. Logistic regression, which tested the ability of each rule to accurately predict the prevalence of L. monocytogenes, validated the rules based on water and pasture. Samples collected near water (odds ratio [OR], 3.0) and pasture (OR, 2.9) showed a significantly increased likelihood of L. monocytogenes isolation compared to that for samples collected far from water and pasture. Generalized linear mixed models identified additional land cover factors associated with an increased likelihood of L. monocytogenes isolation, such as proximity to wetlands. These findings validated a subset of previously developed rules that predict L. monocytogenes prevalence in produce production environments. This suggests that GIS and geospatial models can be used to accurately predict L. monocytogenes prevalence on farms and can be used prospectively to minimize the risk of preharvest contamination of produce. PMID:26590280

  9. Elucidation of Listeria monocytogenes contamination routes in cold-smoked salmon processing plants detected by DNA-based typing methods

    DEFF Research Database (Denmark)

    Vogel, Birte Fonnesbech; Huss, Hans Henrik; Ojeniyi, B.

    2001-01-01

    and environment could not be excluded. Contamination of the product occurred in specific areas (the brining and slicing areas). In plant I, the same RAPD type (RAPD type 12) was found over a 4-year period, indicating that an established in-house flora persisted and was not eliminated by routine hygienic......, monocytogenes). A total of 429 strains of L. monocytogenes were subsequently compared by random amplified polymorphic DNA (RAPD) profiling, and 55 different RAPD types were found. The RAPD types detected on the products were identical to types found on the processing equipment and in the processing environment...... procedures. In plant II, where the prevalence of L, monocytogenes was much tower, no RAPD type persisted over long periods of time, and several different L, monocytogenes RAPD types were isolated. This indicates that persistent strains may be avoided by rigorous cleaning and sanitation; however, due...

  10. Utility of NucleoCounter for the chondrocyte count in the collagenase digest of human native cartilage

    Science.gov (United States)

    Yonenaga, Kazumichi; Nishizawa, Satoru; Akizawa, Miki; Asawa, Yukiyo; Fujihara, Yuko; Takato, Tsuyoshi

    2010-01-01

    In cartilage tissue engineering, viable cell numbers should be correctly counted in the collagenase digest of the biopsied cartilage. However, this is a difficult task due to the presence of matrix debris, cell ghosts and their aggregates. To search for the correct cell counting method in this situation, we evaluated the utility of an automatic cell counting device, the NucleoCounter, and compared it with conventional staining using the LIVE/DEAD® kit. We first measured the cell numbers of a standard chondrocyte sample by the NucleoCounter, which showed a high accuracy (R2 = 0.9999) and reproducibility (%CV: 2.00–8.66). We then calculated the cell numbers and viability in some collagenase digests of native cartilage using either the NucleoCounter or LIVE/DEAD® kit, revealing that the total cell numbers, viable ones and viability were highly correlated between them (R2 = 0.9601, 0.9638 and 0.917, respectively). However, both the intrapersonal and interpersonal variabilities in the NucleoCounter was significantly decreased to about 1/20–1/5, compared to that of the LIVE/DEAD® kit. The NucleoCounter was regarded as a useful tool for simple, rapid, and highly reproducible cell counts, which may not only provide constant experimental data in a certain laboratory, but also contribute to the high reproducibility of the clinical results of cartilage tissue engineering among multiple institutions. PMID:20845070

  11. Prevalence, distribution, and diversity of Listeria monocytogenes in retail environments, focusing on small establishments and establishments with a history of failed inspections.

    Science.gov (United States)

    Hoelzer, Karin; Sauders, Brian D; Sanchez, Maria D; Olsen, Peter T; Pickett, Michele M; Mangione, Kurt J; Rice, Daniel H; Corby, Joe; Stich, Stephen; Fortes, Esther D; Roof, Sherry E; Grohn, Yrjo T; Wiedmann, Martin; Oliver, Haley F

    2011-07-01

    Despite growing concerns about cross-contamination of ready-to-eat foods with Listeria monocytogenes, our knowledge about the ecology and transmission of L. monocytogenes in retail establishments has remained limited. We conducted a cross-sectional study to characterize the prevalence, distribution, and subtype diversity of L. monocytogenes in 120 New York State retail deli establishments that were hypothesized to present an increased risk for environmental L. monocytogenes contamination (i.e., small establishments and establishments with a history of failed New York State Agriculture and Markets inspections). Analysis of these data along with previously reported data for 121 predominantly larger retail establishments in New York State identified establishment size, geographic location, and inspection history as significant predictors of L. monocytogenes presence and prevalence. The odds of an establishment being L. monocytogenes positive were approximately twice as high for large establishments, establishments located in New York City, or establishments with poor inspection history (as compared with establishments without these attributes), even though correlation between location and inspection history complicated interpretation of results. Within an establishment, L. monocytogenes was significantly more prevalent on nonfood contact surfaces than on food contact surfaces; prevalence was particularly high for floors and in floor drains, sinks, the dairy case, and milk crates. L. monocytogenes subtype diversity differed between sites, with lineage I isolates significantly associated with nonfood contact surfaces and lineage II isolates significantly associated with food contact surfaces. Isolates belonging to the same ribotype were often found dispersed across multiple sites within an operation. Copyright ©, International Association for Food Protection

  12. Distribution of the bacteria Listeria monocytogenes in the western part of the Sea of Okhotsk

    Science.gov (United States)

    Terekhova, V. E.; Sosnin, V. A.; Buzoleva, L. S.; Shakirov, R. B.

    2010-04-01

    The Amur River’s influence on the distribution of the opportunistic bacteria Listeria monocytogenes in the western part of the Sea of Okhotsk is discussed. The presence of Listeria in the seawater, sea ice, and sediments on the northeastern Sakhalin shelf and slope supports the idea of its connection with the Amur River discharge. The hypothesis of the allochtonic parentage of L. monocytogenes in the sea’s development is proved.

  13. Inhibition of Listeria monocytogenes on Ready-to-Eat Meats Using Bacteriocin Mixtures Based on Mode-of-Action

    Directory of Open Access Journals (Sweden)

    Paul Priyesh Vijayakumar

    2017-03-01

    Full Text Available Bacteriocin-producing (Bac+ lactic acid bacteria (LAB comprising selected strains of Lactobacillus curvatus, Lactococcus lactis, Pediococcus acidilactici, and Enterococcus faecium and thailandicus were examined for inhibition of Listeria monocytogenes during hotdog challenge studies. The Bac+ strains, or their cell-free supernatants (CFS, were grouped according to mode-of-action (MOA as determined from prior studies. Making a mixture of as many MOAs as possible is a practical way to obtain a potent natural antimicrobial mixture to address L. monocytogenes contamination of RTE meat products (i.e., hotdogs. The heat resistance of the bacteriocins allowed the use of pasteurization to eliminate residual producer cells for use as post-process surface application or their inclusion into hotdog meat emulsion during cooking. The use of Bac+ LAB comprising 3× MOAs directly as co-inoculants on hotdogs was not effective at inhibiting L. monocytogenes. However, the use of multiple MOA Bac+ CFS mixtures in a variety of trials demonstrated the effectiveness of this approach by showing a >2-log decrease of L. monocytogenes in treatment samples and 6–7 log difference vs. controls. These data suggest that surface application of multiple mode-of-action bacteriocin mixtures can provide for an Alternative 2, and possibly Alternative 1, process category as specified by USDA-FSIS for control of L. monocytogenes on RTE meat products.

  14. Listeria monocytogenes endophthalmitis - case report and review of risk factors and treatment outcomes.

    Science.gov (United States)

    Bajor, Anna; Luhr, Anke; Brockmann, Dorothee; Suerbaum, Sebastian; Framme, Carsten; Sedlacek, Ludwig

    2016-07-16

    The majority of cases of endophthalmitis are caused by exogenous pathogens; only 5-10 % are of endogenous origin. One cause of these rare cases of endogenous endophthalmitis is Listeria monocytogenes. Twenty-six cases of endophthalmitis due to this pathogen have been published over the last twenty years. The aim of this review is to summarize the main risk factors and common clinical findings of endogenous endophthalmitis due to Listeria monocytogenes. We report on a 62-year-old female presenting with a sterile hypopyon iritis with secondary glaucoma and an underlying rheumatoid disease. In microbiological analysis we identified Listeria monocytogenes. Further we searched through all published cases for typical signs, risk factors, details of medical and surgical treatment and outcome of endogenous endophthalmitis due to this rare pathogen. Ocular symptoms in almost all of these published cases included pain, redness of the eye, and decreased vision. Main clinical features included elevated intraocular pressure and fibrinous anterior chamber reaction, as well as a dark hypopyon. While the infection is typically spread endogenously, neither an exogenous nor endogenous source of infection could be identified in most cases. Immunocompromised patients are at higher risk of being infected than immunocompetent patients. The clinical course of endophthalmitis caused by Listeria monocytogenes had different visual outcomes. In some cases, the infection led to enucleation, blindness, or strong visual loss, whereas most patients showed a tendency of visual improvement during therapy. Early diagnosis and treatment initiation are crucial factors in the outcome of endogenous endophthalmitis caused by Listeria monocytogenes. This possible differential diagnosis should be kept in mind while treating patients with presumable sterile hypopyon and anterior uveitis having a high intraocular pressure. A bacterial source should be considered with a prompt initiation of systemic

  15. Detection of Listeria monocytogenes from selective enrichment broth using MALDI-TOF Mass Spectrometry.

    Science.gov (United States)

    Jadhav, Snehal; Sevior, Danielle; Bhave, Mrinal; Palombo, Enzo A

    2014-01-31

    Conventional methods used for primary detection of Listeria monocytogenes from foods and subsequent confirmation of presumptive positive samples involve prolonged incubation and biochemical testing which generally require four to five days to obtain a result. In the current study, a simple and rapid proteomics-based MALDI-TOF MS approach was developed to detect L. monocytogenes directly from selective enrichment broths. Milk samples spiked with single species and multiple species cultures were incubated in a selective enrichment broth for 24h, followed by an additional 6h secondary enrichment. As few as 1 colony-forming unit (cfu) of L. monocytogenes per mL of initial selective broth culture could be detected within 30h. On applying the same approach to solid foods previously implicated in listeriosis, namely chicken pâté, cantaloupe and Camembert cheese, detection was achieved within the same time interval at inoculation levels of 10cfu/mL. Unlike the routine application of MALDI-TOF MS for identification of bacteria from solid media, this study proposes a cost-effective and time-saving detection scheme for direct identification of L. monocytogenes from broth cultures.This article is part of a Special Issue entitled: Trends in Microbial Proteomics. Globally, foodborne diseases are major causes of illness and fatalities in humans. Hence, there is a continual need for reliable and rapid means for pathogen detection from food samples. Recent applications of MALDI-TOF MS for diagnostic microbiology focused on detection of microbes from clinical specimens. However, the current study has emphasized its use as a tool for detecting the major foodborne pathogen, Listeria monocytogenes, directly from selective enrichment broths. This proof-of-concept study proposes a detection scheme that is more rapid and simple compared to conventional methods of Listeria detection. Very low levels of the pathogen could be identified from different food samples post-enrichment in

  16. Integrative genomic analysis identifies isoleucine and CodY as regulators of Listeria monocytogenes virulence.

    Directory of Open Access Journals (Sweden)

    Lior Lobel

    2012-09-01

    Full Text Available Intracellular bacterial pathogens are metabolically adapted to grow within mammalian cells. While these adaptations are fundamental to the ability to cause disease, we know little about the relationship between the pathogen's metabolism and virulence. Here we used an integrative Metabolic Analysis Tool that combines transcriptome data with genome-scale metabolic models to define the metabolic requirements of Listeria monocytogenes during infection. Twelve metabolic pathways were identified as differentially active during L. monocytogenes growth in macrophage cells. Intracellular replication requires de novo synthesis of histidine, arginine, purine, and branch chain amino acids (BCAAs, as well as catabolism of L-rhamnose and glycerol. The importance of each metabolic pathway during infection was confirmed by generation of gene knockout mutants in the respective pathways. Next, we investigated the association of these metabolic requirements in the regulation of L. monocytogenes virulence. Here we show that limiting BCAA concentrations, primarily isoleucine, results in robust induction of the master virulence activator gene, prfA, and the PrfA-regulated genes. This response was specific and required the nutrient responsive regulator CodY, which is known to bind isoleucine. Further analysis demonstrated that CodY is involved in prfA regulation, playing a role in prfA activation under limiting conditions of BCAAs. This study evidences an additional regulatory mechanism underlying L. monocytogenes virulence, placing CodY at the crossroads of metabolism and virulence.

  17. Control of Listeria monocytogenes in food production plants

    Directory of Open Access Journals (Sweden)

    Dimitrijević Mirjana

    2008-01-01

    Full Text Available L. monocytogenes has been established in different plants for the production of food, including dairy plants, abattoirs, plants for the processing of fish, as well as those for the production of ready-to-eat (RTE food and this fact is being considered as the primary mechanism of food contamination with this bacteria. There is also the factor of numerous and diverse contaminated production equipment, because it has certain parts that are inaccessible for the necessary cleaning and disinfection. The temperature, position, as well as the material of the work surface are also linked to the contamination of plants with this bacteria. Investigations carried out so far have helped toward the better understanding of the manner and time of contamination of food items in the course of the production process, but there are still unresolved problems, including most certainly the biggest one - the adherence of bacteria and the creation of a biofilm, when the bacteria is in that condition more resistant to so-called stress factors which are usually used in the food industry for the purpose of decontamination of the surfaces with which foods come into contact. The control of L. monocytogenes in food production plants is possible primarily by using an integrated programme, compatible with the systems Hazard Analysis Critical Control Point (HACCP and Good Hygiene Practice (GHP, necessary in the production of food that is safe for the consumer. Essentially, the control measures that can contribute to reducing the incidence of findings of L.monocytogenes in the finished product, as well as the reducing of the level of contamination with this bacteria are linked, on the one hand, with hygiene procedures in the production process, and, on the other, with the applied technological procedures.

  18. Short-term genome evolution of Listeria monocytogenes in a non-controlled environment

    Directory of Open Access Journals (Sweden)

    Ivy Reid A

    2008-11-01

    Full Text Available Abstract Background While increasing data on bacterial evolution in controlled environments are available, our understanding of bacterial genome evolution in natural environments is limited. We thus performed full genome analyses on four Listeria monocytogenes, including human and food isolates from both a 1988 case of sporadic listeriosis and a 2000 listeriosis outbreak, which had been linked to contaminated food from a single processing facility. All four isolates had been shown to have identical subtypes, suggesting that a specific L. monocytogenes strain persisted in this processing plant over at least 12 years. While a genome sequence for the 1988 food isolate has been reported, we sequenced the genomes of the 1988 human isolate as well as a human and a food isolate from the 2000 outbreak to allow for comparative genome analyses. Results The two L. monocytogenes isolates from 1988 and the two isolates from 2000 had highly similar genome backbone sequences with very few single nucleotide (nt polymorphisms (1 – 8 SNPs/isolate; confirmed by re-sequencing. While no genome rearrangements were identified in the backbone genome of the four isolates, a 42 kb prophage inserted in the chromosomal comK gene showed evidence for major genome rearrangements. The human-food isolate pair from each 1988 and 2000 had identical prophage sequence; however, there were significant differences in the prophage sequences between the 1988 and 2000 isolates. Diversification of this prophage appears to have been caused by multiple homologous recombination events or possibly prophage replacement. In addition, only the 2000 human isolate contained a plasmid, suggesting plasmid loss or acquisition events. Surprisingly, besides the polymorphisms found in the comK prophage, a single SNP in the tRNA Thr-4 prophage represents the only SNP that differentiates the 1988 isolates from the 2000 isolates. Conclusion Our data support the hypothesis that the 2000 human listeriosis

  19. Use of multi-locus sequencing typing as identification method for the food-borne pathogen Listeria monocytogenes: a review

    Directory of Open Access Journals (Sweden)

    Sonia Lamon

    2015-01-01

    Full Text Available Listeria monocytogenes is an ubiquitous, intracellular pathogen which has been implicated within the past decade as the causative organism in several outbreaks of foodborne diseases. In this review, a new approach to molecular typing primarily designed for global epidemiology has been described: multi-locus sequencing typing (MLST. This approach is novel, in that it uses data that allow the unambiguous characterization of bacterial strains via the Internet. Our aim is to present the currently available selection of references on L. monocytogenes MLST detection methods and to discuss its use as gold standard to L. monocytogenes subtyping method.

  20. Phosphatidylcholine nanovesicles coated with chitosan or chondroitin sulfate as novel devices for bacteriocin delivery

    Science.gov (United States)

    da Silva, Indjara Mallmann; Boelter, Juliana Ferreira; da Silveira, Nádya Pesce; Brandelli, Adriano

    2014-07-01

    There is increased interest on the use of natural antimicrobial peptides in biomedicine and food preservation technologies. In this study, the antimicrobial activity of nisin encapsulated into nanovesicles containing polyanionic polysaccharides was investigated. Nisin was encapsulated in phosphatidylcholine (PC) liposomes containing chitosan or chondroitin sulfate by the thin-film hydration method and tested for antimicrobial activity against Listeria spp. The mean particle size of PC liposomes was 145 nm and varied to 210 and 134 nm with the incorporation of chitosan and chondroitin sulfate, respectively. Nisin-containing nanovesicles with and without incorporation of polysaccharides had a zeta potential values around -20 mV, showing mostly spherical structures when observed by transmission electron microscopy. Encapsulated nisin had similar efficiency as free nisin in inhibiting Listeria spp. isolated from bovine carcass, and greater efficiency in inhibiting Listeria monocytogenes. The formulation containing chitosan was more stable and more efficient in inhibiting L. monocytogenes when compared to the other nanovesicles tested. After 24 h, the viable cell counts were 2 log lower as compared with the other treatments and 7 log comparing to controls.

  1. Current Perspectives on Viable but Non-culturable State in Foodborne Pathogens.

    Science.gov (United States)

    Zhao, Xihong; Zhong, Junliang; Wei, Caijiao; Lin, Chii-Wann; Ding, Tian

    2017-01-01

    The viable but non-culturable (VBNC) state, a unique state in which a number of bacteria respond to adverse circumstances, was first discovered in 1982. Unfortunately, it has been reported that many foodborne pathogens can be induced to enter the VBNC state by the limiting environmental conditions during food processing and preservation, such as extreme temperatures, drying, irradiation, pulsed electric field, and high pressure stress, as well as the addition of preservatives and disinfectants. After entering the VBNC state, foodborne pathogens will introduce a serious crisis to food safety and public health because they cannot be detected using conventional plate counting techniques. This review provides an overview of the various features of the VBNC state, including the biological characteristics, induction and resuscitation factors, formation and resuscitation mechanisms, detection methods, and relationship to food safety.

  2. Irrigation Is Significantly Associated with an Increased Prevalence of Listeria monocytogenes in Produce Production Environments in New York State.

    Science.gov (United States)

    Weller, Daniel; Wiedmann, Martin; Strawn, Laura K

    2015-06-01

    Environmental (i.e., meteorological and landscape) factors and management practices can affect the prevalence of foodborne pathogens in produce production environments. This study was conducted to determine the prevalence of Listeria monocytogenes, Listeria species (including L. monocytogenes), Salmonella, and Shiga toxin-producing Escherichia coli (STEC) in produce production environments and to identify environmental factors and management practices associated with their isolation. Ten produce farms in New York State were sampled during a 6-week period in 2010, and 124 georeferenced samples (80 terrestrial, 33 water, and 11 fecal) were collected. L. monocytogenes, Listeria spp., Salmonella, and STEC were detected in 16, 44, 4, and 5% of terrestrial samples, 30, 58, 12, and 3% of water samples, and 45, 45, 27, and 9% of fecal samples, respectively. Environmental factors and management practices were evaluated for their association with terrestrial samples positive for L. monocytogenes or other Listeria species by univariate logistic regression; analysis was not conducted for Salmonella or STEC because the number of samples positive for these pathogens was low. Although univariate analysis identified associations between isolation of L. monocytogenes or Listeria spp. from terrestrial samples and various water-related factors (e.g., proximity to wetlands and precipitation), multivariate analysis revealed that only irrigation within 3 days of sample collection was significantly associated with isolation of L. monocytogenes (odds ratio = 39) and Listeria spp. (odds ratio = 5) from terrestrial samples. These findings suggest that intervention at the irrigation level may reduce the risk of produce contamination.

  3. Radiation sensitivities of Listeria monocytogenes isolated from chicken meat and their growth at refrigeration temperatures

    International Nuclear Information System (INIS)

    Harsojo; Banati, D.; Ito, H.

    1997-01-01

    Listeria monocytogenes were isolated in 5 lots, more than one cell in each 25-g sample of 10 lots of chicken meat, which was obtained from several different areas in Japan. From taxonomic study, the psychrotrophic type of 3 isolates grew well at 4°C on Trypticase soy agar slant, whereas 2 isolates grew poorly. Cells of all isolates were sensitive to γ-irradiation in phosphate buffer, and the D 10 values obtained were 0.16 to 0.18 kGy under aerobic irradiation conditions similar to the values of salmonellae. In the chicken meat sample, the D 10 value obtained was 0.42 kGy the same value as in phosphate buffer under anaerobic irradiation conditions, and the necessary dose for inactivation of L. monocytogenes was estimated to be 2 kGy in raw chicken meat below 10 -4 CFU (colony forming unit) per gram. In the storage study of chicken meat which was inoculated with about 3×10 3 CFU per gram of L. monocytogenes, the psychrotrophic type of the isolates grew quickly at 7 to 10°C storage. However, a dose of 1 kGy was also effective to suppress the growth of L. monocytogenes at refrigeration temperatures below 10°C

  4. Antimicrobial resistance of Listeria monocytogenes and Listeria innocua from meat products and meat-processing environment.

    Science.gov (United States)

    Gómez, Diego; Azón, Ester; Marco, Noelia; Carramiñana, Juan J; Rota, Carmina; Ariño, Agustín; Yangüela, Javier

    2014-09-01

    A total of 336 Listeria isolates from ready-to-eat (RTE) meat products and meat-processing environments, consisting of 206 Listeria monocytogenes, and 130 Listeria innocua isolates, were characterized by disc diffusion assay and minimum inhibitory concentration (MIC) values for antimicrobial susceptibility against twenty antimicrobials. Resistance to one or two antimicrobials was observed in 71 L. monocytogenes isolates (34.5%), and 56 L. innocua isolates (43.1%). Multidrug resistance was identified in 24 Listeria isolates, 18 belonging to L. innocua (13.9%) and 6 to L. monocytogenes (2.9%). Oxacillin resistance was the most common resistance phenotype and was identified in 100% Listeria isolates. A medium prevalence of resistance to clindamycin (39.3% isolates) and low incidence of resistance to tetracycline (3.9% isolates) were also detected. Listeria isolates from RTE meat products displayed higher overall antimicrobial resistance (31.3%) than those from the environment (13.4%). All the strains assayed were sensitive to the preferred antibiotics used to treat listeriosis. Results showed that although antimicrobial resistance in L. monocytogenes still occurs at a low prevalence, L. innocua can form a reservoir of resistance genes which may transfer between bacterial species, including transference to organisms capable of causing disease in humans. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Differentiation of different mixed Listeria strains and also acid-injured, heat-injured, and repaired cells of Listeria monocytogenes using fourier transform infrared spectroscopy.

    Science.gov (United States)

    Nyarko, Esmond; Donnelly, Catherine

    2015-03-01

    Fourier transform infrared (FT-IR) spectroscopy was used to differentiate mixed strains of Listeria monocytogenes and mixed strains of L. monocytogenes and Listeria innocua. FT-IR spectroscopy was also applied to investigate the hypothesis that heat-injured and acid-injured cells would return to their original physiological integrity following repair. Thin smears of cells on infrared slides were prepared from cultures for mixed strains of L. monocytogenes, mixed strains of L. monocytogenes and L. innocua, and each individual strain. Heat-injured and acid-injured cells were prepared by exposing harvested cells of L. monocytogenes strain R2-764 to a temperature of 56 ± 0.2°C for 10 min or lactic acid at pH 3 for 60 min, respectively. Cellular repair involved incubating aliquots of acid-injured and heat-injured cells separately in Trypticase soy broth supplemented with 0.6% yeast extract for 22 to 24 h; bacterial thin smears on infrared slides were prepared for each treatment. Spectral collection was done using 250 scans at a resolution of 4 cm(-1) in the mid-infrared wavelength region. Application of multivariate discriminant analysis to the wavelength region from 1,800 to 900 cm(-1) separated the individual L. monocytogenes strains. Mixed strains of L. monocytogenes and L. monocytogenes cocultured with L. innocua were successfully differentiated from the individual strains when the discriminant analysis was applied. Different mixed strains of L. monocytogenes were also successfully separated when the discriminant analysis was applied. A data set for injury and repair analysis resulted in the separation of acid-injured, heat-injured, and intact cells; repaired cells clustered closer to intact cells when the discriminant analysis (1,800 to 600 cm(-1)) was applied. FT-IR spectroscopy can be used for the rapid source tracking of L. monocytogenes strains because it can differentiate between different mixed strains and individual strains of the pathogen.

  6. A small RNA controls expression of the chitinase ChiA in Listeria monocytogenes

    DEFF Research Database (Denmark)

    Nielsen, Jesper S; Larsen, Marianne Halberg; Lillebæk, Eva Maria Sternkopf

    2011-01-01

    role of LhrA in L. monocytogenes. To this end, we determined the effects of LhrA on global-wide gene expression. We observed that nearly 300 genes in L. monocytogenes are either positively or negatively affected by LhrA. Among these genes, we identified lmo0302 and chiA as direct targets of LhrA, thus...... establishing LhrA as a multiple target regulator. Lmo0302 encodes a hypothetical protein with no known function, whereas chiA encodes one of two chitinases present in L. monocytogenes. We show here that LhrA acts as a post-transcriptional regulator of lmo0302 and chiA by interfering with ribosome recruitment......, and we provide evidence that both LhrA and Hfq act to down-regulate the expression of lmo0302 and chiA. Furthermore, in vitro binding experiments show that Hfq stimulates the base pairing of LhrA to chiA mRNA. Finally, we demonstrate that LhrA has a negative effect on the chitinolytic activity of L...

  7. Enhanced biofilm formation in dual-species culture of Listeria monocytogenes and Ralstonia insidiosa

    Directory of Open Access Journals (Sweden)

    Yunfeng Xu

    2017-09-01

    Full Text Available In the natural environments microorganisms coexist in communities as biofilms. Since foodborne pathogens have varying abilities to form biofilms, investigation of bacterial interactions in biofilm formation may enhance our understanding of the persistence of these foodborne pathogens in the environment. Thus the objective of this study was to investigate the interactions between Listeria monocytogenes and Ralstonia insidiosa in dual species biofilms. Biofilm development after 24 h was measured using crystal violet in 96-well microtiter plate. Scanning electron microscopy and cell enumeration were employed after growth on stainless steel coupons. When compared with their single species counterparts, the dual species biofilms exhibited a significant increase in biofilm biomass. The number of L. monocytogenes in co-culture biofilms on stainless steel also increased significantly. However, there was no effect on the biofilm formation of L. monocytogenes when cultured with R. insidiosa separated by a semi-permeable membrane-linked compartment or cultured in R. insidiosa cell-free supernatant, indicating that direct cell-cell contact is critical for this interaction.

  8. A large outbreak of Listeria monocytogenes infection with short incubation period in a tertiary care hospital.

    Science.gov (United States)

    Johnsen, Bjørn Odd; Lingaas, Egil; Torfoss, Dag; Strøm, Erik H; Nordøy, Ingvild

    2010-12-01

    Listeria monocytogenes is a foodborne pathogen with a high mortality rate. We report a large, nosocomial outbreak of Listeria monocytogenes infection. Patients with L. monocytogenes isolated from a sterile site, or from faeces when diarrhoea and fever were present, were included. Clinical data were collected from the patient records. The incubation period was calculated as the time between exposure and start of symptoms. Seventeen patients (11 women, median age 64 years) were infected of whom 15 patients were at increased risk for listeriosis. Eleven patients received empiric antibiotic treatment, eight of them with cephalosporins. Three patients died with a resulting mortality rate of 18%. The source of the outbreak was a Camembert cheese made from pasteurised milk containing up to 360 million colony forming units per portion. The median incubation period was 3-4 days. The incubation period in this outbreak was significantly shorter than previously reported, a fact that may be due to the high number of ingested bacteria. Furthermore, food restrictions in hospitals seem warranted, as do treatment with antibiotics effective against L. monocytogenes in at-risk populations. Copyright © 2010 The British Infection Association. Published by Elsevier Ltd. All rights reserved.

  9. Occurrence of Listeria monocytogenes in Ready-to-Eat Meat Products and Meat Processing Plants in Spain

    Directory of Open Access Journals (Sweden)

    Diego Gómez

    2015-07-01

    Full Text Available The aim of this work was to study the occurrence of Listeria monocytogenes in several types of ready-to-eat (RTE meat products and in the environment of meat processing plants. A total of 129 samples of RTE meat products and 110 samples from work surfaces and equipment were analyzed. L. monocytogenes was detected in 6 out of 35 cooked products (17.14%, 21 out of 57 raw-cured products (36.84%, and 9 out of 37 dry-cured, salted products (24.32%. The number of sample units that exceeded the food safety limit of 100 cfu/g decreased from the manufacture date to half shelf life, and then it was further reduced at the end of shelf life. L. monocytogenes was detected in 25 out of 110 (22.72% food contact surfaces. The number of positive and negative results from both food and environmental samples were cross-tabulated and the calculated Cohen’s kappa coefficient (κ was 0.3233, indicating a fair agreement in terms of Listeria contamination. L. monocytogenes was recovered after cleaning and disinfection procedures in four plants, highlighting the importance of thorough cleaning and disinfection.

  10. Flagellar motility is critical for Listeria monocytogenes biofilm formation.

    Science.gov (United States)

    Lemon, Katherine P; Higgins, Darren E; Kolter, Roberto

    2007-06-01

    The food-borne pathogen Listeria monocytogenes attaches to environmental surfaces and forms biofilms that can be a source of food contamination, yet little is known about the molecular mechanisms of its biofilm development. We observed that nonmotile mutants were defective in biofilm formation. To investigate how flagella might function during biofilm formation, we compared the wild type with flagellum-minus and paralyzed-flagellum mutants. Both nonmotile mutants were defective in biofilm development, presumably at an early stage, as they were also defective in attachment to glass during the first few hours of surface exposure. This attachment defect could be significantly overcome by providing exogenous movement toward the surface via centrifugation. However, this centrifugation did not restore mature biofilm formation. Our results indicate that it is flagellum-mediated motility that is critical for both initial surface attachment and subsequent biofilm formation. Also, any role for L. monocytogenes flagella as adhesins on abiotic surfaces appears to be either minimal or motility dependent under the conditions we examined.

  11. Biosensor for the detection of Listeria monocytogenes: emerging trends

    KAUST Repository

    Soni, Dharmendra Kumar

    2018-05-23

    The early detection of Listeria monocytogenes (L. monocytogenes) and understanding the disease burden is of paramount interest. The failure to detect pathogenic bacteria in the food industry may have terrible consequences, and poses deleterious effects on human health. Therefore, integration of methods to detect and trace the route of pathogens along the entire food supply network might facilitate elucidation of the main contamination sources. Recent research interest has been oriented towards the development of rapid and affordable pathogen detection tools/techniques. An innovative and new approach like biosensors has been quite promising in revealing the foodborne pathogens. In spite of the existing knowledge, advanced research is still needed to substantiate the expeditious nature and sensitivity of biosensors for rapid and in situ analysis of foodborne pathogens. This review summarizes recent developments in optical, piezoelectric, cell-based, and electrochemical biosensors for Listeria sp. detection in clinical diagnostics, food analysis, and environmental monitoring, and also lists their drawbacks and advantages.

  12. Validation of a Previously Developed Geospatial Model That Predicts the Prevalence of Listeria monocytogenes in New York State Produce Fields.

    Science.gov (United States)

    Weller, Daniel; Shiwakoti, Suvash; Bergholz, Peter; Grohn, Yrjo; Wiedmann, Martin; Strawn, Laura K

    2016-02-01

    Technological advancements, particularly in the field of geographic information systems (GIS), have made it possible to predict the likelihood of foodborne pathogen contamination in produce production environments using geospatial models. Yet, few studies have examined the validity and robustness of such models. This study was performed to test and refine the rules associated with a previously developed geospatial model that predicts the prevalence of Listeria monocytogenes in produce farms in New York State (NYS). Produce fields for each of four enrolled produce farms were categorized into areas of high or low predicted L. monocytogenes prevalence using rules based on a field's available water storage (AWS) and its proximity to water, impervious cover, and pastures. Drag swabs (n = 1,056) were collected from plots assigned to each risk category. Logistic regression, which tested the ability of each rule to accurately predict the prevalence of L. monocytogenes, validated the rules based on water and pasture. Samples collected near water (odds ratio [OR], 3.0) and pasture (OR, 2.9) showed a significantly increased likelihood of L. monocytogenes isolation compared to that for samples collected far from water and pasture. Generalized linear mixed models identified additional land cover factors associated with an increased likelihood of L. monocytogenes isolation, such as proximity to wetlands. These findings validated a subset of previously developed rules that predict L. monocytogenes prevalence in produce production environments. This suggests that GIS and geospatial models can be used to accurately predict L. monocytogenes prevalence on farms and can be used prospectively to minimize the risk of preharvest contamination of produce. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  13. Rapid detection of Listeria monocytogenes in raw milk and soft cheese by a redox potential measurement based method combined with real-time PCR.

    Science.gov (United States)

    Erdősi, Orsolya; Szakmár, Katalin; Reichart, Olivér; Szili, Zsuzsanna; László, Noémi; Székely Körmöczy, Péter; Laczay, Péter

    2014-09-01

    The incidence of outbreaks of foodborne listeriosis has indicated the need for a reliable and rapid detection of the microbe in different foodstuffs. A method combining redox potential measurement and real-time polymerase chain reaction (PCR) was developed to detect Listeria monocytogenes in artificially contaminated raw milk and soft cheese. Food samples of 25 g or 25 ml were homogenised in 225 ml of Listeria Enrichment Broth (LEB) with Oxford supplement, and the redox potential measurement technique was applied. For Listeria species the measuring time was maximum 34 h. The absence of L. monocytogenes could reliably be proven by the redox potential measurement method, but Listeria innocua and Bacillus subtilis could not be differentiated from L. monocytogenes on the basis of the redox curves. The presence of L. monocytogenes had to be confirmed by real-time PCR. The combination of these two methods proved to detect < 10 cfu/g of L. monocytogenes in a cost- and time-effective manner. This method can potentially be used as an alternative to the standard nutrient method for the rapid detection of L. monocytogenes in food.

  14. In vivo transcriptional profiling of Listeria monocytogenes and mutagenesis identify new virulence factors involved in infection.

    Directory of Open Access Journals (Sweden)

    Ana Camejo

    2009-05-01

    Full Text Available Listeria monocytogenes is a human intracellular pathogen able to colonize host tissues after ingestion of contaminated food, causing severe invasive infections. In order to gain a better understanding of the nature of host-pathogen interactions, we studied the L. monocytogenes genome expression during mouse infection. In the spleen of infected mice, approximately 20% of the Listeria genome is differentially expressed, essentially through gene activation, as compared to exponential growth in rich broth medium. Data presented here show that, during infection, Listeria is in an active multiplication phase, as revealed by the high expression of genes involved in replication, cell division and multiplication. In vivo bacterial growth requires increased expression of genes involved in adaptation of the bacterial metabolism and stress responses, in particular to oxidative stress. Listeria interaction with its host induces cell wall metabolism and surface expression of virulence factors. During infection, L. monocytogenes also activates subversion mechanisms of host defenses, including resistance to cationic peptides, peptidoglycan modifications and release of muramyl peptides. We show that the in vivo differential expression of the Listeria genome is coordinated by a complex regulatory network, with a central role for the PrfA-SigB interplay. In particular, L. monocytogenes up regulates in vivo the two major virulence regulators, PrfA and VirR, and their downstream effectors. Mutagenesis of in vivo induced genes allowed the identification of novel L. monocytogenes virulence factors, including an LPXTG surface protein, suggesting a role for S-layer glycoproteins and for cadmium efflux system in Listeria virulence.

  15. Listeria monocytogenes isolates from food and food environment harbouring tetM and ermB resistance genes.

    Science.gov (United States)

    Haubert, L; Mendonça, M; Lopes, G V; de Itapema Cardoso, M R; da Silva, W P

    2016-01-01

    Listeria monocytogenes is a foodborne pathogen that has become an important cause of human and animal diseases worldwide. The purpose of this study was to evaluate the serotypes, virulence potential, antimicrobial resistance profile, and genetic relationships of 50 L. monocytogenes isolates from food and food environment in southern Brazil. In this study, the majority of L. monocytogenes isolates belonged to the serotypes 1/2b (42%) and 4b (26%), which are the main serotypes associated with human listeriosis. In addition, all isolates harboured internalin genes (inlA, inlC, inlJ), indicating a virulence potential. The isolates were sensitive to most of the antimicrobial compounds analysed, and five isolates (10%) were multi-resistant. Two isolates harboured antimicrobial resistance genes (tetM and ermB) and in one of them, the gene was present in the plasmid. Moreover, according to the pulsed field gel electrophoresis assay, two multi-resistant isolates were a single clone isolated from food and the processing plant. The isolates were susceptible to the most frequently used antibiotics for listeriosis treatment. However, the presence of multidrug-resistant isolates and antimicrobial resistance genes including in the plasmid could even be transferred between bacterial species, suggesting a potential health risk to consumers and a potential risk of spreading multi-resistance genes to other bacteria. Listeria monocytogenes is an important agent of foodborne diseases. The results of this study suggest a potential capacity of L. monocytogenes isolates from food and food environment to cause human infections. Antimicrobial multi-resistance profiles were detected in 10%, and two isolates harboured tetM and ermB resistance genes. Moreover, the present research can help to build up a better knowledge about antimicrobial resistance of L. monocytogenes. Additionally, we found one isolate carrying tetM resistance gene in a plasmid, that suggests a possible transmission

  16. Inhibition of Listeria monocytogenes by Lactobacillus bavaricus MN in beef systems at refrigeration temperatures.

    OpenAIRE

    Winkowski, K; Crandall, A D; Montville, T J

    1993-01-01

    The ability of Lactobacillus bavaricus, a meat isolate, to inhibit the growth of three Listeria monocytogenes strains was examined in three beef systems: beef cubes, beef cubes in gravy, and beef cubes in gravy containing glucose. The beef was minimally heat treated, inoculated with L. bavaricus at 10(5) or 10(3) CFU/g and L. monocytogenes at 10(2) CFU/g, vacuum sealed, and stored at 4 or 10 degrees C. The meat samples were monitored for microbial growth, pH, and bacteriocin production. The p...

  17. How the study of Listeria monocytogenes has led to new concepts in biology.

    Science.gov (United States)

    Rolhion, Nathalie; Cossart, Pascale

    2017-06-01

    The opportunistic intracellular bacterial pathogen Listeria monocytogenes has in 30 years emerged as an exceptional bacterial model system in infection biology. Research on this bacterium has provided considerable insight into how pathogenic bacteria adapt to mammalian hosts, invade eukaryotic cells, move intracellularly, interfere with host cell functions and disseminate within tissues. It also contributed to unveil features of normal host cell pathways and unsuspected functions of previously known cellular proteins. This review provides an updated overview of our knowledge on this pathogen. In many examples, findings on L. monocytogenes provided the basis for new concepts in bacterial regulation, cell biology and infection processes.

  18. Molecular Characterization and Phylogenetic Analysis of Listeria monocytogenes Isolated from Milk and Milk Products in Kaduna, Nigeria

    Directory of Open Access Journals (Sweden)

    U. B. Usman

    2016-01-01

    Full Text Available In this study, Listeria (L. monocytogenes isolated from milk and milk products in Kaduna, Nigeria, were subjected to a multiplex PCR assay to identify virulence-associated genes (such as prf A, inl A, hly A, act A, and iap. Of the 36 isolates, 9 (25% were positive for one or two virulence-associated genes. Based on the sample type, 6 (16.9% of the isolates that possessed virulence-associated genes were obtained from raw milk, 2 (3.2% from “Manshanu,” and 1 (2.8% from “Kindrimo.” Sequence and phylogenetic analysis based on the 16S rRNA revealed that Nigerian L. monocytogenes isolates (NGA 34A, NGA 35A, NGA 41A, and NGA 38A, when compared with reference L. monocytogenes, were grouped into two distinct clusters, A and B, with sequence (NGA 34A, NGA 35A, and NGA 41A phylogenetically closer to J1776; N1-011A; R2-502; J1816; and J2-031, whereas L. monocytogenes isolate (NGA 38A clustered with EDG; J1-220; J1926; J1817; and J2-1091. The separation of the Nigerian L. monocytogenes isolates into linage A (responsible for epidemic listeriosis and lineage B (responsible for sporadic cases of listeriosis is of public health concern and that local isolates might have potentials for human food borne listeriosis based on the virulence factors so far identified.

  19. Prevalence and Level of Listeria monocytogenes in Ice Cream Linked to a Listeriosis Outbreak in the United States.

    Science.gov (United States)

    Chen, Y I; Burall, Laurel S; Macarisin, Dumitru; Pouillot, Régis; Strain, Errol; DE Jesus, Antonio J; Laasri, Anna; Wang, Hua; Ali, Laila; Tatavarthy, Aparna; Zhang, Guodong; Hu, Lijun; Day, James; Kang, Jihun; Sahu, Surasri; Srinivasan, Devayani; Klontz, Karl; Parish, Mickey; Evans, Peter S; Brown, Eric W; Hammack, Thomas S; Zink, Donald L; Datta, Atin R

    2016-11-01

    A most-probable-number (MPN) method was used to enumerate Listeria monocytogenes in 2,320 commercial ice cream scoops manufactured on a production line that was implicated in a 2015 listeriosis outbreak in the United States. The analyzed samples were collected from seven lots produced in November 2014, December 2014, January 2015, and March 2015. L. monocytogenes was detected in 99% (2,307 of 2,320) of the tested samples (lower limit of detection, 0.03 MPN/g), 92% of which were contaminated at ice cream products linked to a listeriosis outbreak provided a unique data set for further understanding the risk associated with L. monocytogenes contamination for highly susceptible populations.

  20. Internalin profiling and multilocus sequence typing suggest four Listeria innocua subgroups with different evolutionary distances from Listeria monocytogenes.

    Science.gov (United States)

    Chen, Jianshun; Chen, Qiaomiao; Jiang, Lingli; Cheng, Changyong; Bai, Fan; Wang, Jun; Mo, Fan; Fang, Weihuan

    2010-03-31

    Ecological, biochemical and genetic resemblance as well as clear differences of virulence between L. monocytogenes and L. innocua make this bacterial clade attractive as a model to examine evolution of pathogenicity. This study was attempted to examine the population structure of L. innocua and the microevolution in the L. innocua-L. monocytogenes clade via profiling of 37 internalin genes and multilocus sequence typing based on the sequences of 9 unlinked genes gyrB, sigB, dapE, hisJ, ribC, purM, gap, tuf and betL. L. innocua was genetically monophyletic compared to L. monocytogenes, and comprised four subgroups. Subgroups A and B correlated with internalin types 1 and 3 (except the strain 0063 belonging to subgroup C) and internalin types 2 and 4 respectively. The majority of L. innocua strains belonged to these two subgroups. Subgroup A harbored a whole set of L. monocytogenes-L. innocua common and L. innocua-specific internalin genes, and displayed higher recombination rates than those of subgroup B, including the relative frequency of occurrence of recombination versus mutation (rho/theta) and the relative effect of recombination versus point mutation (r/m). Subgroup A also exhibited a significantly smaller exterior/interior branch length ratio than expected under the coalescent model, suggesting a recent expansion of its population size. The phylogram based on the analysis with correction for recombination revealed that the time to the most recent common ancestor (TMRCA) of L. innocua subgroups A and B were similar. Additionally, subgroup D, which correlated with internalin type 5, branched off from the other three subgroups. All L. innocua strains lacked seventeen virulence genes found in L. monocytogenes (except for the subgroup D strain L43 harboring inlJ and two subgroup B strains bearing bsh) and were nonpathogenic to mice. L. innocua represents a young species descending from L. monocytogenes and comprises four subgroups: two major subgroups A and B

  1. Internalin profiling and multilocus sequence typing suggest four Listeria innocua subgroups with different evolutionary distances from Listeria monocytogenes

    Science.gov (United States)

    2010-01-01

    Background Ecological, biochemical and genetic resemblance as well as clear differences of virulence between L. monocytogenes and L. innocua make this bacterial clade attractive as a model to examine evolution of pathogenicity. This study was attempted to examine the population structure of L. innocua and the microevolution in the L. innocua-L. monocytogenes clade via profiling of 37 internalin genes and multilocus sequence typing based on the sequences of 9 unlinked genes gyrB, sigB, dapE, hisJ, ribC, purM, gap, tuf and betL. Results L. innocua was genetically monophyletic compared to L. monocytogenes, and comprised four subgroups. Subgroups A and B correlated with internalin types 1 and 3 (except the strain 0063 belonging to subgroup C) and internalin types 2 and 4 respectively. The majority of L. innocua strains belonged to these two subgroups. Subgroup A harbored a whole set of L. monocytogenes-L. innocua common and L. innocua-specific internalin genes, and displayed higher recombination rates than those of subgroup B, including the relative frequency of occurrence of recombination versus mutation (ρ/θ) and the relative effect of recombination versus point mutation (r/m). Subgroup A also exhibited a significantly smaller exterior/interior branch length ratio than expected under the coalescent model, suggesting a recent expansion of its population size. The phylogram based on the analysis with correction for recombination revealed that the time to the most recent common ancestor (TMRCA) of L. innocua subgroups A and B were similar. Additionally, subgroup D, which correlated with internalin type 5, branched off from the other three subgroups. All L. innocua strains lacked seventeen virulence genes found in L. monocytogenes (except for the subgroup D strain L43 harboring inlJ and two subgroup B strains bearing bsh) and were nonpathogenic to mice. Conclusions L. innocua represents a young species descending from L. monocytogenes and comprises four subgroups: two

  2. Stochastic modelling of Listeria monocytogenes single cell growth in cottage cheese with mesophilic lactic acid bacteria from aroma producing cultures

    DEFF Research Database (Denmark)

    Østergaard, Nina Bjerre; Christiansen, Lasse Engbo; Dalgaard, Paw

    2015-01-01

    . 2014. Modelling the effect of lactic acid bacteria from starter- and aroma culture on growth of Listeria monocytogenes in cottage cheese. International Journal of Food Microbiology. 188, 15-25]. Growth of L. monocytogenes single cells, using lag time distributions corresponding to three different......A stochastic model was developed for simultaneous growth of low numbers of Listeria monocytogenes and populations of lactic acid bacteria from the aroma producing cultures applied in cottage cheese. During more than two years, different batches of cottage cheese with aroma culture were analysed...

  3. Longitudinal study on the sources of Listeria monocytogenes contamination in cold-smoked salmon and its processing environment in Italy.

    Science.gov (United States)

    Di Ciccio, Pierluigi; Meloni, Domenico; Festino, Anna Rita; Conter, Mauro; Zanardi, Emanuela; Ghidini, Sergio; Vergara, Alberto; Mazzette, Rina; Ianieri, Adriana

    2012-08-01

    The aim of the present study was to investigate the sources of Listeria monocytogenes contamination in a cold smoked salmon processing environment over a period of six years (2003-2008). A total of 170 samples of raw material, semi-processed, final product and processing surfaces at different production stages were tested for the presence of L. monocytogenes. The L. monocytogenes isolates were characterized by multiplex PCR for the analysis of virulence factors and for serogrouping. The routes of contamination over the six year period were traced by PFGE. L. monocytogenes was isolated from 24% of the raw salmon samples, 14% of the semi-processed products and 12% of the final products. Among the environmental samples, 16% were positive for L. monocytogenes. Serotyping yielded three serovars: 1/2a, 1/2b, 4b, with the majority belonging to serovars 1/2a (46%) and 1/2b (39%). PFGE yielded 14 profiles: two of them were repeatedly isolated in 2005-2006 and in 2007-2008 mainly from the processing environment and final products but also from raw materials. The results of this longitudinal study highlighted that contamination of smoked salmon occurs mainly during processing rather than originating from raw materials, even if raw fish can be a contamination source of the working environment. Molecular subtyping is critical for the identification of the contamination routes of L. monocytogenes and its niches into the production plant when control strategies must be implemented with the aim to reduce its prevalence during manufacturing. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. A putative ABC transporter is involved in negative regulation of biofilm formation by Listeria monocytogenes

    DEFF Research Database (Denmark)

    Zhu, Xinna; Long, Fei; Chen, Yonghui

    2008-01-01

    Listeria monocytogenes may persist for long periods in food processing environments. In some instances, this may be due to aggregation or biofilm formation. To investigate the mechanism controlling biofilm formation in the food-borne pathogen L. monocytogenes, we characterized LM-49, a mutant...... with enhanced ability of biofilm-formation generated via transposon Tn917 mutagenesis of L. monocytogenes 4b G. In this mutant, a Tn917 insertion has disrupted the coding region of the gene encoding a putative ATP binding cassette (ABC) transporter permease identical to Lmof2365_1771 (a putative ABC...... the same amount of biofilm biomass as the wild-type strain. Furthermore, transcription of the downstream lm.G_1770 was not influenced by the upstream Tn917 insertion, and the presence of Tn917 has no effect on biofilm formation. These results suggest that lm.G_1771 was solely responsible for the negative...

  5. Influence of Organic Material and Biofilms on Disinfectant Efficacy Against Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Hilda Nyati

    2012-04-01

    Full Text Available The effects of organic material and biofilm formation on the efficacy of Suma Tab D4 chlorine tablets and Suma Bac D10 quaternary ammonium compound (QAC against Listeria monocytogenes was determined in suspension and on stainless steel and polystyrene surfaces according to standard disinfectant test methodology. Exposure to 200 and 740 mg L-1 QAC and to 150 mg L-1 active chlorine resulted in a > 5.0 log10 CFU mL-1 and > 5.0 log10 CFU/coupon reduction of six L. monocytogenes strains within one minute, in suspension tests, and on stainless steel surfaces, respectively. Additionally, there was a reduction by as much as 5 log10 CFU/coupon or 5 log10 CFU/well of reference strains EGDe and Scott A biofilms within five minutes on stainless steel and polystyrene surfaces. Organic material, added as bovine serum albumin at 0.3% (w/v completely prevented the inactivation of L. monocytogenes in 150 mg L-1 chlorine, while reductions of only 0.6 +- 0.1 log10 CFU mL-1 were recorded in the presence of UHT milk at 3% (v/v. In contrast, reductions of 5 log10 CFU mL-1 were recorded within one minute on exposure to 740 mg L-1 QAC in the presence of 0.3% (w/v bovine serum albumin and within two minutes in the presence of 20 % (v/v UHT milk. Although Suma D4 chlorine tablets and Suma Bac D10 QAC are effective listericidal agents at recommended concentrations, Suma Tab D4 chlorine efficacy against L. monocytogenes is impaired by the presence of low concentrations of organic material, while Suma Bac D10 QAC maintains its listericidal activity in high organic loads.

  6. An Assessment of Different Genomic Approaches for Inferring Phylogeny of Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Clémentine Henri

    2017-11-01

    Full Text Available Background/objectives: Whole genome sequencing (WGS has proven to be a powerful subtyping tool for foodborne pathogenic bacteria like L. monocytogenes. The interests of genome-scale analysis for national surveillance, outbreak detection or source tracking has been largely documented. The genomic data however can be exploited with many different bioinformatics methods like single nucleotide polymorphism (SNP, core-genome multi locus sequence typing (cgMLST, whole-genome multi locus sequence typing (wgMLST or multi locus predicted protein sequence typing (MLPPST on either core-genome (cgMLPPST or pan-genome (wgMLPPST. Currently, there are little comparisons studies of these different analytical approaches. Our objective was to assess and compare different genomic methods that can be implemented in order to cluster isolates of L. monocytogenes.Methods: The clustering methods were evaluated on a collection of 207 L. monocytogenes genomes of food origin representative of the genetic diversity of the Anses collection. The trees were then compared using robust statistical analyses.Results: The backward comparability between conventional typing methods and genomic methods revealed a near-perfect concordance. The importance of selecting a proper reference when calling SNPs was highlighted, although distances between strains remained identical. The analysis also revealed that the topology of the phylogenetic trees between wgMLST and cgMLST were remarkably similar. The comparison between SNP and cgMLST or SNP and wgMLST approaches showed that the topologies of phylogenic trees were statistically similar with an almost equivalent clustering.Conclusion: Our study revealed high concordance between wgMLST, cgMLST, and SNP approaches which are all suitable for typing of L. monocytogenes. The comparable clustering is an important observation considering that the two approaches have been variously implemented among reference laboratories.

  7. RAPID DNA EXTRACTION AND PCR VALIDATION FOR DIRECT DETECTION OF Listeria monocytogenes IN RAW MILK

    Directory of Open Access Journals (Sweden)

    Edith Burbano

    2006-05-01

    Full Text Available Objective. The aim of this study was to validate a method for detecting L. monocytogenes in raw milk.Materials and methods. The extraction procedure carried out using a chaotropic agent like NaI, toreduce fat in the sample to 0.2% w/v, which is the lowest limit for detection in the Gerber method, toavoid the polymerization. The raw milk samples were analyzed by using the traditional gold standardmethod for L. monocytogenes. Detection PCR was done on the specificity of primers that recognize theListeria genus by amplifying a specific fragment of about 938bp of the 16S rDNA. Several primer setswere use: L1 (CTCCATAAAGGTGACCCT, U1 (CAGCMGCCGCGGTAATWC, LF (CAAACGTTAACAACGCAGTAand LR (TCCAGAGTGATCGATGTTAA that recognize the hlyA gene of L. monocytogenes, amplifying a 750bpfragment. Results. The DNA of 39 strains evidenced high specificity of the technique since all the strainsof L. monocytogenes amplified the fragments 938bp and 750bp, specifically for genus and species,respectively. The detection limit of the PCR was 101 CFU/ml. T he PCR reproducibility showed a Kappa of0.85; the specificity and sensitivity of 100% were found, predictive positive and negative values were of100% respectively. Conclusions. These results demonstrate that is possible to detect of Listeria spp. byusing any of the three methods since they share the same sensitivity and specificity. One hundred percentof the predictive value for PCR (alternative method provides high reliability, and allows the detection ofthe positive samples. The extraction procedure combined with a PCR method can reduce in 15 days thetime of identification of L. monocytogenes in raw milk. This PCR technique could be adapted and validatedto be use for other types of food such as poultry, meat products and cheeses

  8. Determining If Phylogenetic Relatedness of Listeria Monocytogenes Isolates Corresponds to Persistence in Poultry Processing Plants Using Whole-Genome Sequencing

    Science.gov (United States)

    Introduction: Controlling Listeria monocytogenes on ready-to-eat meat and poultry products and in food processing facilities is challenging. Surveys have found that some L. monocytogenes types are more persistent in processing facilities than others, but the reason is unknown. It is possible persist...

  9. Formation of biofilm by strains of Listeria monocytogenes isolated ...

    African Journals Online (AJOL)

    Quantification of biofilm formation by 40 Listeria monocytogenes strains from wara soft cheese and its processing environment was assessed on glass vials surfaces. Attachement to glass surface was quantified using a crystal violet binding assay. All the 40 strains produced biofilms after 48 and 72 h incubation at 37oC.

  10. Carrier status for Listeria monocytogenes and other Listeria species ...

    African Journals Online (AJOL)

    Background: Listeria organisms are documented to be zoonotic; one of the sources of infection is the domestic fowl where it could occur as in apparent infection. The carriage of Listeria monocytogenes and other Listeria in indigenous birds has not been documented in Kenya. Objective: To establish whether healthy looking ...

  11. Tolerance development in Listeria monocytogenes-Escherichia coli dual-species biofilms after sublethal exposures to pronase-benzalkonium chloride combined treatments.

    Science.gov (United States)

    Rodríguez-López, Pedro; Cabo, Marta López

    2017-10-01

    This study was designed to assess the effects that sublethal exposures to pronase (PRN) and benzalkonium chloride (BAC) combined treatments have on Listeria monocytogenes-Escherichia coli dual-species biofilms grown on stainless steel in terms of tolerance development (TD) to these compounds. Additionally, fluorescence microscopy was used to observe the changes of the biofilm structure. PRN-BAC exposure was carried out using three different approaches and TD was evaluated treating biofilms with a final 100 μg/ml PRN followed by 50 μg/ml BAC combined treatment. Results showed that exposure to PRN-BAC significantly decreased the number of adhered L. monocytogenes (P reduction values were generally lower in L. monocytogenes compared to E. coli. Additionally, microscopy images showed an altered morphology produced by sublethal PRN-BAC in exposed L. monocytogenes-E. coli dual-species biofilms compared to control samples. Results also demonstrated that L. monocytogenes-E. coli dual-species biofilms are able to develop tolerance to PRN-BAC combined treatments depending on way they have been previously exposed. Moreover, they suggest that the generation of bacterial tolerance should be included as a parameter for sanitation procedures design. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Survival of Listeria monocytogenes in mozzarella cheese and ice cream exposed to gamma irradiation

    International Nuclear Information System (INIS)

    Hashisaka, A.E.; Weagant, S.D.; Dong, F.M.

    1989-01-01

    The survival of Listeria monocytogenes preinoculated into ice cream and mozzarella cheese prior to gamma-irradiation treatment was determined. Samples were maintained at -78 degrees C and exposed to targeted doses of 2, 4, 8, 16, and 32 kGy of gamma-irradiation. The calculated D10 values were 1.4 kGy for mozzarella cheese and 2.0 kGy for ice cream. The effective level of irradiation (12D) for inactivating L. monocytogenes was 16.8 kGy for mozzarella cheese and 24.4 kGy for ice cream

  13. Listeria Spp. and Listeria Monocytogenes Contamination in Ready-To-Eat Sandwiches Collected from Vending Machines.

    Science.gov (United States)

    Cossu, Francesca; Spanu, Carlo; Deidda, Silvia; Mura, Erica; Casti, Daniele; Pala, Carlo; Lamon, Sonia; Spanu, Vincenzo; Ibba, Michela; Marrocu, Elena; Scarano, Christian; Piana, Andrea; De Santis, Enrico Pietro Luigi

    2016-04-19

    Ready-to-eat (RTE) food is characterised by a long shelf-life at refrigerated temperature and can be consumed as such, without any treatment. The aim of the work was to evaluate the presence of Listeria spp. and Listeria monocytogenes in RTEs collected from refrigerated vending machines placed in hospital environment and accessible to the hospitalised patients. In 4 different sampling, 55 RTEs were collected from vending machines of six hospitals located in different areas of Sardinia region. All the samples were characterised by similar manufacturing process, such as the use of modified atmosphere packaging and belonged to 5 different producers. Listeria spp. was not countable using the enumeration method in all of the analysed samples. Using the detection method, Listeria spp. was recovered from 9 sandwich samples. Interestingly, 3 of these samples (5.5%) made by the manufacturer, were positive for L. monocytogenes contamination. The risk related to the L. monocytogenes presence in RTEs proportionally increases when food is introduced in susceptible environments , such as hospitals and consumed by susceptible people . Although the RTEs analysed showed values that complied with the European microbiological criteria for foodstuffs, the availability of these products in a susceptible environment should be carefully checked. Therefore, in order to limit the possible exposition to L. monocytogenes , more information on the risk related to RTE consumption should be provided to the hospitalised patients.

  14. Listeria spp. and Listeria monocytogenes contamination in ready-to-eat sandwiches collected from vending machines

    Directory of Open Access Journals (Sweden)

    Francesca Cossu

    2016-05-01

    Full Text Available Ready-to-eat (RTE food is characterised by a long shelf-life at refrigerated temperature and can be consumed as such, without any treatment. The aim of the work was to evaluate the presence of Listeria spp. and Listeria monocytogenes in RTEs collected from refrigerated vending machines placed in hospital environment and accessible to the hospitalised patients. In 4 different sampling, 55 RTEs were collected from vending machines of six hospitals located in different areas of Sardinia region. All the samples were characterised by similar manufacturing process, such as the use of modified atmosphere packaging and belonged to 5 different producers. Listeria spp. was not countable using the enumeration method in all of the analysed samples. Using the detection method, Listeria spp. was recovered from 9 sandwich samples. Interestingly, 3 of these samples (5.5% made by the manufacturer, were positive for L. monocytogenes contamination. The risk related to the L. monocytogenes presence in RTEs proportionally increases when food is introduced in susceptible environments, such as hospitals and consumed by susceptible people. Although the RTEs analysed showed values that complied with the European microbiological criteria for foodstuffs, the availability of these products in a susceptible environment should be carefully checked. Therefore, in order to limit the possible exposition to L. monocytogenes, more information on the risk related to RTE consumption should be provided to the hospitalised patients.

  15. Comparative genomics analyses revealed two virulent Listeria monocytogenes strains isolated from ready-to-eat food.

    Science.gov (United States)

    Lim, Shu Yong; Yap, Kien-Pong; Thong, Kwai Lin

    2016-01-01

    Listeria monocytogenes is an important foodborne pathogen that causes considerable morbidity in humans with high mortality rates. In this study, we have sequenced the genomes and performed comparative genomics analyses on two strains, LM115 and LM41, isolated from ready-to-eat food in Malaysia. The genome size of LM115 and LM41 was 2,959,041 and 2,963,111 bp, respectively. These two strains shared approximately 90% homologous genes. Comparative genomics and phylogenomic analyses revealed that LM115 and LM41 were more closely related to the reference strains F2365 and EGD-e, respectively. Our virulence profiling indicated a total of 31 virulence genes shared by both analysed strains. These shared genes included those that encode for internalins and L. monocytogenes pathogenicity island 1 (LIPI-1). Both the Malaysian L. monocytogenes strains also harboured several genes associated with stress tolerance to counter the adverse conditions. Seven antibiotic and efflux pump related genes which may confer resistance against lincomycin, erythromycin, fosfomycin, quinolone, tetracycline, and penicillin, and macrolides were identified in the genomes of both strains. Whole genome sequencing and comparative genomics analyses revealed two virulent L. monocytogenes strains isolated from ready-to-eat foods in Malaysia. The identification of strains with pathogenic, persistent, and antibiotic resistant potentials from minimally processed food warrant close attention from both healthcare and food industry.

  16. Predictive models for the effect of storage temperature on Vibrio parahaemolyticus viability and counts of total viable bacteria in Pacific oysters (Crassostrea gigas).

    Science.gov (United States)

    Fernandez-Piquer, Judith; Bowman, John P; Ross, Tom; Tamplin, Mark L

    2011-12-01

    Vibrio parahaemolyticus is an indigenous bacterium of marine environments. It accumulates in oysters and may reach levels that cause human illness when postharvest temperatures are not properly controlled and oysters are consumed raw or undercooked. Predictive models were produced by injecting Pacific oysters (Crassostrea gigas) with a cocktail of V. parahaemolyticus strains, measuring viability rates at storage temperatures from 3.6 to 30.4°C, and fitting the data to a model to obtain parameter estimates. The models were evaluated with Pacific and Sydney Rock oysters (Saccostrea glomerata) containing natural populations of V. parahaemolyticus. V. parahaemolyticus viability was measured by direct plating samples on thiosulfate-citrate-bile salts-sucrose (TCBS) agar for injected oysters and by most probable number (MPN)-PCR for oysters containing natural populations. In parallel, total viable bacterial counts (TVC) were measured by direct plating on marine agar. Growth/inactivation rates for V. parahaemolyticus were -0.006, -0.004, -0.005, -0.003, 0.030, 0.075, 0.095, and 0.282 log₁₀ CFU/h at 3.6, 6.2, 9.6, 12.6, 18.4, 20.0, 25.7, and 30.4°C, respectively. The growth rates for TVC were 0.015, 0.023, 0.016, 0.048, 0.055, 0.071, 0.133, and 0.135 log₁₀ CFU/h at 3.6, 6.2, 9.3, 14.9, 18.4, 20.0, 25.7, and 30.4°C, respectively. Square root and Arrhenius-type secondary models were generated for V. parahaemolyticus growth and inactivation kinetic data, respectively. A square root model was produced for TVC growth. Evaluation studies showed that predictive growth for V. parahaemolyticus and TVC were "fail safe." The models can assist oyster companies and regulators in implementing management strategies to minimize V. parahaemolyticus risk and enhancing product quality in supply chains.

  17. Comparative genomics and transcriptomics of lineages I, II, and III strains of Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Hain Torsten

    2012-04-01

    Full Text Available Abstract Background Listeria monocytogenes is a food-borne pathogen that causes infections with a high-mortality rate and has served as an invaluable model for intracellular parasitism. Here, we report complete genome sequences for two L. monocytogenes strains belonging to serotype 4a (L99 and 4b (CLIP80459, and transcriptomes of representative strains from lineages I, II, and III, thereby permitting in-depth comparison of genome- and transcriptome -based data from three lineages of L. monocytogenes. Lineage III, represented by the 4a L99 genome is known to contain strains less virulent for humans. Results The genome analysis of the weakly pathogenic L99 serotype 4a provides extensive evidence of virulence gene decay, including loss of several important surface proteins. The 4b CLIP80459 genome, unlike the previously sequenced 4b F2365 genome harbours an intact inlB invasion gene. These lineage I strains are characterized by the lack of prophage genes, as they share only a single prophage locus with other L. monocytogenes genomes 1/2a EGD-e and 4a L99. Comparative transcriptome analysis during intracellular growth uncovered adaptive expression level differences in lineages I, II and III of Listeria, notable amongst which was a strong intracellular induction of flagellar genes in strain 4a L99 compared to the other lineages. Furthermore, extensive differences between strains are manifest at levels of metabolic flux control and phosphorylated sugar uptake. Intriguingly, prophage gene expression was found to be a hallmark of intracellular gene expression. Deletion mutants in the single shared prophage locus of lineage II strain EGD-e 1/2a, the lma operon, revealed severe attenuation of virulence in a murine infection model. Conclusion Comparative genomics and transcriptome analysis of L. monocytogenes strains from three lineages implicate prophage genes in intracellular adaptation and indicate that gene loss and decay may have led to the emergence

  18. Listeria monocytogenes behaviour in presence of non-UV-irradiated titanium dioxide nanoparticles.

    Directory of Open Access Journals (Sweden)

    Maria Grazia Ammendolia

    Full Text Available Listeria monocytogenes is the agent of listeriosis, a food-borne disease. It represents a serious problem for the food industry because of its environmental persistence mainly due to its ability to form biofilm on a variety of surfaces. Microrganisms attached on the surfaces are a potential source of contamination for environment and animals and humans. Titanium dioxide nanoparticles (TiO2 NPs are used in food industry in a variety of products and it was reported that daily exposure to these nanomaterials is very high. Anti-listerial activity of TiO2 NPs was investigated only with UV-irradiated nanomaterials, based on generation of reactive oxigen species (ROS with antibacterial effect after UV exposure. Since both Listeria monocytogenes and TiO2 NPs are veicolated with foods, this study explores the interaction between Listeria monocytogenes and non UV-irradiated TiO2 NPs, with special focus on biofilm formation and intestinal cell interaction. Scanning electron microscopy and quantitative measurements of biofilm mass indicate that NPs influence both production and structural architecture of listerial biofilm. Moreover, TiO2 NPs show to interfere with bacterial interaction to intestinal cells. Increased biofilm production due to TiO2 NPs exposure may favour bacterial survival in environment and its transmission to animal and human hosts.

  19. Genes that are involved in high hydrostatic pressure treatments in a Listeria monocytogenes Scott A ctsR deletion mutant

    Science.gov (United States)

    Listeria monocytogenes is a food-borne pathogen of significant threat to public health. High Hydrostatic Pressure (HHP) treatment can be used to control L. monocytogenes in food. The CtsR (class three stress gene repressor) protein negatively regulates the expression of class III heat shock genes....

  20. The pathogenic potential of different pulsed-field gel electrophoresis types of Listeria monocytogenes strains isolated from food in Northeast Bosnia and Herzegovina.

    Science.gov (United States)

    Hodžić, Snjezana; Hukić, Mirsada; Franciosa, Giovanna; Aureli, Paolo

    2011-09-01

    Listeria monocytogenes is often present in meat and meat products that are sold in the area of northeast Bosnia and Herzegovina. The major objective of this study was to examine the virulence of L. monocytogenes strains isolated from these types of food in that geographic area. Polymerase chain reaction was used to detect eight genes responsible for virulence of this pathogen, namely, prfA, inlA, inlB, hly, plcA, plcB, actA, and mpl. All examined isolates were confirmed to possess the eight virulence genes. Ten different pulsed-field gel electrophoresis (PFGE) macrorestriction profiles were recognized among 19 L. monocytogenes strains after restriction with two different endonucleases (ApaI and AscI). The pathogenicity of three different PFGE types of L. monocytogenes was confirmed through in vivo tests, which were performed on female white mice (Pasteur strain), and it ranged from 3.55 × 10(8) LD50 to 1.58 × 10(10) LD50. All of the three different PFGE types of L. monocytogenes were regarded as moderately virulent in relation to the reference strain L. monocytogenes Scott A. This result might be one of the reasons for the absence of reported listeriosis in northeast Bosnia and Herzegovina, despite the high degree of food contamination with this pathogen.

  1. Fate of gamma-irradiated Listeria monocytogenes during refrigerated storage on raw or cooked turkey breast meat

    International Nuclear Information System (INIS)

    Thayer, D.W.; Boyd, G.; Kim, A.; Fox, J.B. Jr.; Farrell, H.M. Jr.

    1998-01-01

    The radiation resistance and ability of Listeria monocytogenes ATCC 7644, 15313, 43256, and 49594 to multiply on irradiated, air-packed, refrigerated raw or cooked turkey breast meat nuggets (ca. 25 g) and ground turkey breast meat was investigated. Gamma-radiation D values for L. monocytogenes were significantly different on raw and cooked nuggets, 0.56 +/- 0.03 kGy and 0.69 +/- 0.03 kGy, respectively; but they were not significantly different (P less than or equal to 0.05) on raw and cooked ground turkey meat. High populations (approximately 10(9) CFU/g) of L. monocytogenes declined during 14 days of storage at 4 degrees C in both irradiated and nonirradiated samples of raw but not of cooked ground turkey breast meat. A moderate inoculum (approximately 10(3) CFU/g) did not survive a radiation dose of 3 kGy. The population increased in cooked but not in raw samples of irradiated ground turkey meat stored at either 2 or 7 degrees C for 21 days. The D value changed significantly from 0.70 +/- 0.04 to 0.60 +/- 0.02 kGy when the product was cooked to an internal temperature of 80 degrees C before irradiation. Growth on either raw or cooked turkey meat did not alter the radiation resistance of L. monocytogenes. Analyses were performed for pH, a(w), moisture, and reducing potential of raw and cooked turkey meat and for pH, amino acid profile, thiamine, and riboflavin contents of aqueous extracts of raw and cooked turkey meats without identifying the factor or factors involved in differences in the survival and multiplication of L. monocytogenes on raw and cooked meat

  2. Prevalence of Listeria monocytogenes in pork-meat and other processed products from the Colombian swine industry

    Directory of Open Access Journals (Sweden)

    Andrea Gamboa Marín

    2012-04-01

    Full Text Available Objective. To determine the prevalence of L. monocytogenes in pork carcasses, meat cuts, and meat products (“chorizo”, sausage and ham. Materials and methods. Stratified sampling was implemented in meat-processed products. We analyzed 566 (37% carcasses, 472 (31% meat cuts, and 481, (32% meat-processed products, distributed as follows: 169 (11% sausage, 163 (11% ham, and 149 (10% “chorizo”, for a total of 1519 (100% samples in a period of 18 months. The samples were processed using the ISO-17604, ISO-11290-1 and the USDA/FSIS (MLG-8.03 methods. Genus and species were confirmed by multiplex-PCR. Results. We obtained isolates of L. monocytogenes from 21 carcasses (10%, 160 (76% from meat deboning, 10 (5% from ham, 6 (3% from “chorizo”, and 13 (6% from sausage. The prevalence found was 3.7% and 33.9% in carcasses and meat deboning respectively. The prevalence in the meat-processed products was 4.03% in “chorizo”, 6.13% in ham and 7.69% in sausage. The overall prevalence of L. monocytogenes in the study was 13.82%. Conclusions. We found L. monocytogenes in different products analyzed, with particular interest in ham and sausage since both are consumed without previous heat treatment.

  3. Enumeration of Vibrio parahaemolyticus in the viable but nonculturable state using direct plate counts and recognition of individual gene fluorescence in situ hybridization.

    Science.gov (United States)

    Griffitt, Kimberly J; Noriea, Nicholas F; Johnson, Crystal N; Grimes, D Jay

    2011-05-01

    Vibrio parahaemolyticus is a gram-negative, halophilic bacterium indigenous to marine and estuarine environments and it is capable of causing food and water-borne illness in humans. It can also cause disease in marine animals, including cultured species. Currently, culture-based techniques are used for quantification of V. parahaemolyticus in environmental samples; however, these can be misleading as they fail to detect V. parahaemolyticus in a viable but nonculturable (VBNC) state which leads to an underestimation of the population density. In this study, we used a novel fluorescence visualization technique, called recognition of individual gene fluorescence in situ hybridization (RING-FISH), which targets chromosomal DNA for enumeration. A polynucleotide probe labeled with Cyanine 3 (Cy3) was created corresponding to the ubiquitous V. parahaemolyticus gene that codes for thermolabile hemolysin (tlh). When coupled with the Kogure method to distinguish viable from dead cells, RING-FISH probes reliably enumerated total, viable V. parahaemolyticus. The probe was tested for sensitivity and specificity against a pure culture of tlh(+), tdh(-), trh(-)V. parahaemolyticus, pure cultures of Vibrio vulnificus, Vibrio harveyi, Vibrio alginolyticus and Vibrio fischeri, and a mixed environmental sample. This research will provide additional tools for a better understanding of the risk these environmental organisms pose to human health. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. The Distribution of Listeria in Pasture-Raised Broiler Farm Soils Is Potentially Related to University of Vermont Medium Enrichment Bias toward Listeria innocua over Listeria monocytogenes

    Science.gov (United States)

    Locatelli, Aude; Lewis, Micah A.; Rothrock, Michael J.

    2017-01-01

    The occurrence of Listeria monocytogenes has been widely investigated in the poultry production chain from the processing plant to the final product. However, limited data are available on Listeria species, including Listeria monocytogenes, in the poultry farm environment. Therefore, fecal and soil samples from 37 pastured poultry flocks from 10 all-natural farms over 3 years were assessed to determine the prevalence and diversity of Listeria within these alternative poultry farm environments using standard cultural and molecular methods. Listeria species were isolated in 15% of poultry farm samples and included Listeria innocua (65.7%), L. monocytogenes (17.4%), and Listeria welshimeri (15.1%). Additional multiplex PCR serotyping showed group 1/2a-3a to be the most dominant L. monocytogenes serovar group. Based on these results, monoculture growth experiments were conducted on four Listeria soil isolates (three L. monocytogenes isolates representing the three recovered serovar groups and one L. innocua isolate) to determine if culture medium [tripticase soy broth (TSB) and University of Vermont modified Listeria enrichment broth (UVM)], inoculum concentration (102 or 105 CFU/ml), or incubation temperature (20, 30, and 42°C) differentially affected these Listeria species. Overall, very few significant growth differences were observed between the behavior of the three L. monocytogenes isolates (representing the three recovered serovar groups) under the growth conditions tested. Alternatively, at 30°C in UVM with the lower inoculum concentration, the L. innocua isolate had a significantly shorter lag phase than the L. monocytogenes isolates. In coculture growth studies under these same incubation conditions, the lag phase of L. innocua and L. monocytogenes was similar, but the final concentration of L. innocua was significantly higher than L. monocytogenes. However, cocultures in UVM for high inoculum concentration did not show preferential growth of L. innocua

  5. The Distribution of Listeria in Pasture-Raised Broiler Farm Soils Is Potentially Related to University of Vermont Medium Enrichment Bias toward Listeria innocua over Listeria monocytogenes.

    Science.gov (United States)

    Locatelli, Aude; Lewis, Micah A; Rothrock, Michael J

    2017-01-01

    The occurrence of Listeria monocytogenes has been widely investigated in the poultry production chain from the processing plant to the final product. However, limited data are available on Listeria species, including Listeria monocytogenes , in the poultry farm environment. Therefore, fecal and soil samples from 37 pastured poultry flocks from 10 all-natural farms over 3 years were assessed to determine the prevalence and diversity of Listeria within these alternative poultry farm environments using standard cultural and molecular methods. Listeria species were isolated in 15% of poultry farm samples and included Listeria innocua (65.7%), L. monocytogenes (17.4%), and Listeria welshimeri (15.1%). Additional multiplex PCR serotyping showed group 1/2a-3a to be the most dominant L. monocytogenes serovar group. Based on these results, monoculture growth experiments were conducted on four Listeria soil isolates (three L. monocytogenes isolates representing the three recovered serovar groups and one L. innocua isolate) to determine if culture medium [tripticase soy broth (TSB) and University of Vermont modified Listeria enrichment broth (UVM)], inoculum concentration (10 2 or 10 5  CFU/ml), or incubation temperature (20, 30, and 42°C) differentially affected these Listeria species. Overall, very few significant growth differences were observed between the behavior of the three L. monocytogenes isolates (representing the three recovered serovar groups) under the growth conditions tested. Alternatively, at 30°C in UVM with the lower inoculum concentration, the L. innocua isolate had a significantly shorter lag phase than the L. monocytogenes isolates. In coculture growth studies under these same incubation conditions, the lag phase of L. innocua and L. monocytogenes was similar, but the final concentration of L. innocua was significantly higher than L. monocytogenes . However, cocultures in UVM for high inoculum concentration did not show preferential growth of L

  6. Construction of a multiple fluorescence labeling system for use in co-invasion studies of Listeria monocytogenes

    DEFF Research Database (Denmark)

    Andersen, Jens Bo; Roldgaard, Bent; Lindner, A. B.

    2006-01-01

    strains at the single cell level by use of fluorescence microscopy. More than 90% of the L. monocytogenes host cells maintained the fluorescence tags for 40 generations. The fluorescence tags did not alter the invasive capacity of the L. monocytogenes cells in a traditional Caco-2 cell invasion assay......, and visual discrimination between invaded bacteria carrying different fluorescent labels inside the cells was possible. Conclusion The constructed fluorescent marker system is stable, easy to use, does not affect the virulence of L. monocytogenes in Caco-2 cell assays, and allows discrimination between...... deviations in the observed capacity for infection when animal models are used. One way to circumvent this problem is to carry out virulence studies as competition assays between 2 or more strains. This, however, requires invasion-neutral markers that enable easy discrimination between the different strains...

  7. Chitinase Expression in Listeria monocytogenes Is Influenced by lmo0327, Which Encodes an InternalinLike Protein

    DEFF Research Database (Denmark)

    Paspaliari, Dafni Katerina; Kastbjerg, Vicky Gaedt; Ingmer, Hanne

    2017-01-01

    The chitinolytic system of Listeria monocytogenes thus far comprises two chitinases, ChiA and ChiB, and a lytic polysaccharide monooxygenase, Lmo2467. The role of the system in the bacterium appears to be pleiotropic, as besides mediating hydrolysis of chitin, the second most ubiquitous...... chitinase activities enabling them to utilize chitin as the sole source of carbon and nitrogen. Interestingly, several bacterial chitinases may also be involved in host pathogenesis. For example, in the important food borne pathogen Listeria monocytogenes, the chitinases ChiA and ChiB, and the lytic...... ChiA and ChiB in the culture supernatants of the mutant strain. Our results provide new information regarding the function of the lmo0325-lmo0327 locus in L. monocytogenes and link it to the expression of chitinolytic activity.Importance: Many bacteria from terrestrial and marine environments express...

  8. Collection of Listeria monocytogenes Isolates from Milk, Dairy Products and Food Processing Environments in Slovakia for the Purposes of European Molecular Database

    OpenAIRE

    Kubicová Z.; Filipová M.; Jurovčíková J.; Cabanová L

    2017-01-01

    The molecular typing of Listeria monocytogenes isolates is an important tool for monitoring the spread of the strains in food chains, providing evidence for epidemiological investigations and for the detection of out-breaks. The demand of European typing data centralization, collection and sharing stimulated the generation of “EURL L. monocytogenes Database (EURL Lm DB)” in 2012 led by the European Union Reference Laboratory (EURL) for L. monocytogenes (ANSES Maisons-Alfort Laboratory for Foo...

  9. Mechanistic model coupling gas exchange dynamics and Listeria monocytogenes growth in modified atmosphere packaging of non respiring food.

    Science.gov (United States)

    Chaix, E; Broyart, B; Couvert, O; Guillaume, C; Gontard, N; Guillard, V

    2015-10-01

    A mechanistic model coupling O2 and CO2 mass transfer (namely diffusion and solubilisation in the food itself and permeation through the packaging material) to microbial growth models was developed aiming at predicting the shelf life of modified atmosphere packaging (MAP) systems. It was experimentally validated on a non-respiring food by investigating concomitantly the O2/CO2 partial pressure in packaging headspace and the growth of Listeria monocytogenes (average microbial count) within the food sample. A sensitivity analysis has revealed that the reliability of the prediction by this "super-parametrized" model (no less than 47 parameters were required for running one simulation) was strongly dependent on the accuracy of the microbial input parameters. Once validated, this model was used to decipher the role of O2/CO2 mass transfer on microbial growth and as a MAP design tool: an example of MAP dimensioning was provided in this paper as a proof of concept. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Prevalence of L. monocytogenes in environmental samples collected in dairy plants of Sassari Province, Italy

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    Giovanni Terrosu

    2015-09-01

    Full Text Available Listeria (L. monocytogenes is frequently isolated from food production environment and often persists in dairy plants despite vigorous sanitation regimes. In recent years several alert notifications were sent to Rapid Alert System for Food Products system as a consequence of Listeria monocytogenes contamination of ricotta cheese. After the alert of 2012, competent authority (Local Health Unit of Sassari Province organised an environmental monitoring plan with the partnership of the Institute for Experimental Veterinary Medicine of Sardinia to verify analysis of dairy plants own-check according to Regulation (EC N° 2073/05 and further modifications. In 2014 n. 665 processing areas samples of n. 50 dairy plants of Sassari Province were examined. UNI EN ISO 11290-1:2005 for detection of L. monocytogenes was used. Non-compliance in n. 5 diary plants are observed (n. 8 positive samples. Post-non-compliance environmental sanitisation was efficient and own-check plans included appropriate corrective actions.

  11. Use Carum copticum essential oil for controlling the Listeria monocytogenes growth in fish model system

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    Soghra Rabiey

    2014-01-01

    Full Text Available This study was conducted to evaluate the antibacterial effect of Carum copticum essential oil (Ajowan EO against Listeria monocytogenes in fish model system. Ajowan EO chemical composition was determined by gas chromatography/mass spectral analysis and the highest concentration of Carum copticum essential oil without any significant changes on sensory properties of kutum fish (Rutilus frisii kutum was assigned. Then the inhibitory effect of Ajowan EO at different concentrations in presence of salt and smoke component was tested on L. monocytogenes growth in fish peptone broth (FPB, kutum broth and cold smoked kutum broth at 4 ºC for 12 days. Ajowan EO completely decreased the number of L. monocytogenes in FPB after 12 days of storage, however, antimicrobial effect of EO significantly reduced in kutum and cold smoked kutum broth. Addition of 4% NaCl and smoke component improved the anti-listerial activity of Ajowan EO in all fish model broths.

  12. Influence of temperature on alkali stress adaptation in Listeria monocytogenes

    Science.gov (United States)

    Listeria monocytogenes cells may induce alkali stress adaptation when exposed to sublethal concentrations of alkaline cleaners and sanitizers that may be frequently used in the food processing environment. In the present study, the effect of temperature on the induction and the stability of such alk...

  13. Behavior of Escherichia coli O157:H7 and Listeria monocytogenes during fermentation and storage of camel yogurt.

    Science.gov (United States)

    Al-Nabulsi, Anas A; Olaimat, Amin N; Osaili, Tareq M; Ayyash, Mutamed M; Abushelaibi, Aisha; Jaradat, Ziad W; Shaker, Reyad; Al-Taani, Mahmoud; Holley, Richard A

    2016-03-01

    In addition to its nutritional and therapeutic properties, camel milk has the ability to suppress the growth of a wide range of foodborne pathogens, but there is a lack of information regarding the behavior of these pathogens in products such as yogurt produced from camel milk. The objective of the current study was to investigate the behavior of Listeria monocytogenes and Escherichia coli O157:H7 during manufacture and storage of camel yogurt. Camel milk inoculated with L. monocytogenes and E. coli O157:H7 was fermented at 43° C for 5h using freeze-dried lactic acid bacteria (LAB) starter cultures (Streptococcus thermophilus and Lactobacillus bulgaricus) and stored at 4 or 10 °C for 14 d. Camel milk inoculated with L. monocytogenes and E. coli O157:H7 without starter culture was also prepared. During fermentation, the numbers of L. monocytogenes and E. coli O157:H7 increased 0.3 and 1.6 log cfu/mL, respectively, in the presence of LAB, and by 0.3 and 2.7 log cfu/mL in the absence of LAB. During storage at 4 or 10 °C, L. monocytogenes increased 0.8 to 1.2 log cfu/mL by 14 d in camel milk without LAB, but in the presence of LAB, the numbers of L. monocytogenes were reduced by 1.2 to 1.7 log cfu/mL by 14 d. Further, E. coli O157:H7 numbers in camel milk were reduced by 3.4 to 3.5 log cfu/mL in the absence of LAB, but E. coli O157:H7 was not detected (6.3 log cfu/mL reduction) by 7d in camel yogurt made with LAB and stored at either temperature. Although camel milk contains high concentrations of natural antimicrobials, L. monocytogenes was able to tolerate these compounds in camel yogurt stored at refrigerator temperatures. Therefore, appropriate care should be taken during production of yogurt from camel milk to minimize the potential for postprocess contamination by this and other foodborne pathogens. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  14. HrcA and DnaK are important for static and continuous flow biofilm formation and disinfectant resistance in Listeria monocytogenes

    NARCIS (Netherlands)

    Veen, van der S.; Abee, T.

    2010-01-01

    The food-borne pathogen Listeria monocytogenes is able to form biofilms in food processing environments. Since biofilms are generally difficult to eradicate during clean-up procedures, they pose a major risk for the food industry. Stress resistance mechanisms involved in L. monocytogenes biofilm

  15. How a routine checking of Escherichia coli in retailed food of animal origin can protect consumers against exposition to Campylobacter spp. and Listeria monocytogenes?

    Directory of Open Access Journals (Sweden)

    Trajković-Pavlović Ljiljana

    2010-01-01

    Full Text Available Background/Aim. According to the literature that has been published over the last two decades Campylobacter spp i Listeria monocitogens can be identified as causes of numerous diseases derived by consuming food of animal origin. The purpose of this paper was to find out how established national microbiological criteria of the Republic of Serbia on food safety in retailed food of animal origin could contribute to consumer's protection against exposition to foodborne pathogens such as Campylobacter spp. and Listeria monocytogenes. Methods. During a routine microbiological safety control of randomly selected 60 samples of fresh poultry meat, 30 samples of other fresh meat readymade for grilling, 30 samples of sausage products, 37 samples of heattreated meat, 39 samples of toppings for fast food of animal origin and 31 samples of dairy products a national food safety criteria (Escherichia coli, aerobic plate count, Salmonella spp., coagulasa positive Staphylococcus, Proteus spp., sulphitoreducting Clostridia were applied and, as well as, testing to Campylobacter spp. and Listeria monocitogens. In determination of Campylobacter spp. and Listeria monocytogenes, food quality control methods of the Food and Agriculture Organization (FAO were applied, while in determination of the other above motioned bacteria, national provisions on microbiological methods were applied who are adjusted to the FAO ones. Results. Related to the national criteria on microbiological food safety, 88 (38.8% samples, out of the total 227 tested, were rejected. When to these results, the results of laboratory tests on Listeria monocytogens were added, a terminal number of rejected samples were not changed. When to these results, the results of Campylobacter spp. testing were added, 91 (40.1% out of the 227 samples were unsatisfied. Results of logistic regression model with occurrence of Escherichia coli as dependent variable indicated that Escherichia coli was 4.5 times likely

  16. How a routine checking of Escherichia coli in retailed food of animal origin can protect consumers against exposition to Campylobacter spp. and Listeria monocytogenes?

    Science.gov (United States)

    Trajković-Pavlović, Ljiljana; Novaković, Budimka; Martinov-Cvejin, Mirjana; Gusman, Vera; Bijelović, Sanja; Dragnić, Natasa; Balać, Dragana

    2010-08-01

    According to the literature that has been published over the last two decades Campylobacter spp i Listeria monocitogens can be identified as causes of numerous diseases derived by consuming food of animal origin. The purpose of this paper was to find out how established national microbiological criteria of the Republic of Serbia on food safety in retailed food of animal origin could contribute to consumer's protection against exposition to foodborne pathogens such as Campylobacter spp. and Listeria monocytogenes. During a routine microbiological safety control of randomly selected 60 samples of fresh poultry meat, 30 samples of other fresh meat readymade for grilling, 30 samples of sausage products, 37 samples of heat-treated meat, 39 samples of toppings for fast food of animal origin and 31 samples of dairy products a national food safety criteria (Escherichia coli, aerobic plate count, Salmonella spp., coagulasa positive Staphylococcus, Proteus spp., sulphito-reducting Clostridia) were applied and, as well as, testing to Campylobacter spp. and Listeria monocitogens. In determination of Campylobacter spp. and Listeria monocytogenes, food quality control methods of the Food and Agriculture Organization (FAO) were applied, while in determination of the other above motioned bacteria, national provisions on microbiological methods were applied who are adjusted to the FAO ones. Related to the national criteria on microbiological food safety, 88 (38.8%) samples, out of the total 227 tested, were rejected. When to these results, the results of laboratory tests on Listeria monocytogens were added, a terminal number of rejected samples were not changed. When to these results, the results of Campylobacter spp. testing were added, 91 (40.1%) out of the 227 samples were unsatisfied. Results of logistic regression model with occurrence of Escherichia coli as dependent variable indicated that Escherichia coli was 4.5 times likely to occur among samples with Campylobacter spp

  17. Patogénesis de Listeria monocytogenes, microorganismo zoonotico emergente

    Directory of Open Access Journals (Sweden)

    Kirvis Torres

    2005-05-01

    Full Text Available Listeria monocytogenes además de ser un paradigma para la investigación inmunológica se ha convertidoen sistema modelo apropiado para el análisis de los mecanismos moleculares del parasitismo intracelularde otras bacterias. Investigadores en el área de la inmunología se interesaron en este microorganismocuando se reconoció el riesgo que representaba para la salud pública y la seguridad en la industria dealimentos. Desde mediados de los años 80’s se ha investigado la biología molecular de los marcadores devirulencia de este microorganismo, la biología celular de las interacciones de los marcadores de virulenciacon los receptores de la célula hospedero, el citoesqueleto, las vías de transducción de señales y losmecanismos de inmunidad mediada por células del hospedero. El propósito de esta revisión es describiralgunas características taxonómicas y filogenéticas de Listeria monocytogenes , la incidencia humana yanimal de varios serotipos, la fisiopatología de la infección , modelos animales y de cultivo celular utilizadospara estudios de virulencia, las poblaciones de riesgo, manifestaciones clínicas de listeriosis humana yanimal, el tratamiento, la organización genética y evolución de los determinantes de virulencia, losmecanismos empleados para interactuar con la célula hospedera, y los mecanismos para escapar de losprocesos de muerte celular y pasar de una célula infectada a otra. La información recopilada resulta degran importancia para el personal de salud, industria, consumidores y población de riesgo; razón por lacual Listeria monocytogenes es un patógeno que representa una amenaza para la salud pública mundial.

  18. Detection of Listeria spp. in liquid egg products and in the egg breaking plants environment and tracking of Listeria monocytogenes by PFGE.

    Science.gov (United States)

    Rivoal, Katell; Fablet, Aurore; Courtillon, Céline; Bougeard, Stéphanie; Chemaly, Marianne; Protais, Jocelyne

    2013-08-16

    Human listeriosis, caused by Listeria monocytogenes, is a severe bacterial infection that can lead to meningitis, cerebromeningitis, bacteremia or septicemia, with acute lethality and potentially leading to death. A study has shown that 29.5% of the caged laying hens in France are contaminated by L. monocytogenes (Chemaly et al., 2008). However, very little information regarding egg and egg product contamination is currently available. The objective of this study is to determine the sanitary status of egg products and egg breaking plants in France regarding Listeria spp. and L. monocytogenes contaminations. The sampling scheme performed in five egg breaking plants in Western France during one year have revealed that 8.5% of raw egg products were contaminated by L. monocytogenes. No pasteurized egg products have been shown to be contaminated by L. monocytogenes. However, a high level of contamination by Listeria spp., and particularly by L. innocua, has been shown with 26.2% and 1.8% of raw and pasteurized egg products contaminated, respectively. This work has also revealed the presence of Listeria spp. and L. monocytogenes in the environment of egg breaking plants with 65.1% and 8.0% of contaminated samples, respectively. The typing of 253 isolates of L. monocytogenes by PFGE using ApaI and AscI enzymes has revealed a high diversity with 46 different pulsotypes and has shown that the raw material is a source of contamination of egg breaking plants. One L. monocytogenes cluster was dominant in the 5 egg-breaking plants during the four seasons studied. The issue of which strains are better adapted to egg products must be considered and studied in depth by comparing them to pulsotypes from strains of other chains. However, the traceability of L. monocytogenes in plants during the various seasons has also made it possible to highlight the presence of strains that are specific to egg breaking plants. The study of cleaning and disinfection methods in these plants as well

  19. Salmonella enterica serovar Enteritidis and Listeria monocytogenes in mango (Mangifera indica L.) pulp: growth, survival and cross-contamination.

    Science.gov (United States)

    Penteado, Ana L; de Castro, M Fernanda P M; Rezende, Ana C B

    2014-10-01

    This study examined the ability of Salmonella enterica serovar Enteritidis and Listeria monocytogenes to grow or survive in mango pulp stored at -20°C, 4°C, 10°C and 25°C, as well as to cross-contaminate mangoes by means of a knife contaminated with different levels of these pathogens. At 25°C lag phase durations of 19 h and 7.2 h and generation times of 0.66 and 1.44 were obtained, respectively, for S. Enteritidis and L. monocytogenes. At 10°C only the growth of L. monocytogenes was observed. At 4°C both bacteria survived for 8 days. At -20°C S. Enteritidis was able to survive for 5 months while L. monocytogenes survived for 8 months. Cross-contamination was observed for knives contaminated with 10⁶, 10⁵ and 10⁴ CFU mL⁻¹ of S. Enteritidis and 10⁶ and 10⁵ CFU mL⁻¹ of L. monocytogenes. Both microorganisms can grow well in mango pulp at 25°C, thus lower temperatures for the maintenance of the pulps are crucial to avoid growth of these microorganisms. A refrigeration temperature of 10°C will avoid only the growth of S. Enteritidis. Thus good handling practices should be rigidly enforced to avoid any contamination as even at refrigeration and freezing temperatures survival of these pathogens may occur. © 2014 Society of Chemical Industry.

  20. Prevalence and risk factors for Listeria monocytogenes in broiler flocks in Shiraz, southern Iran.

    Science.gov (United States)

    Hosseinzadeh, Saeid; Shekarforoush, Seyed Shahram; Ansari-Lari, Maryam; EsalatPanah-Fard Jahromi, Mehdi; Berizi, Enayat; Abdollahi, Mostafa

    2012-06-01

    Listeria monocytogenes has been identified as an important foodborne pathogen in recent years. In humans, it most commonly affects pregnant women, neonates, children, elderly people, and persons with a suppressed immune system. It could contaminate both raw and cooked meat and poultry products. Studies regarding prevalence and risk factors of L. monocytogenes in broilers flocks are limited. Therefore, the present study was conducted to determine the prevalence and risk factors for L. monocytogenes in poultry flocks in Shiraz, southern Iran. During August to September 2009, in total, 100 broiler flocks were selected at slaughter, and 21 specimens were collected from cloacal samples from each flock. Polymerase chain reaction (PCR) was performed on the samples enriched in buffered Listeria enrichment broth (BLEB), using specific primers. Furthermore, enriched samples in BLEB and/or BLEB treated with 5% KOH were subcultured on Palcam medium. Data about farm and flocks were collected using a structured questionnaire. The prevalence of L. monocytogenes was 7% (95% CI, 2-12%) and 1% using PCR and culture, respectively. Results showed that using antibiotics during rearing period was dramatically reduced the rate of isolation (odds ratio [OR]=0.07, p=0.03), whereas house capacity of more than 10,000 birds (OR=24.03, p=0.04) and number of houses (OR=2, p=0.02) significantly increased the prevalence. The correlation between poor management of large poultry flocks and increasing the risk of contamination was more likely due to the recontamination of cooked poultry/undercooking or cross-contamination of other ready-to-eat foods.