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Sample records for monocytogenes viable counts

  1. 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

    Listeria monocytogenes has a remarkable ability to survive and persist in food production environments. The purpose of the present study was to determine if cells in a population of L. monocytogenes differ in sensitivity to disinfection agents as this could be a factor explaining persistence...... 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...... 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

  2. 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...... that a population of L. monocytogenes cells, whether planktonic or attached, is homogenous with respect to sensitivity to an acidic disinfectant studied on the single-cell level. Hence a major subpopulation more tolerant to disinfectants, and hence more persistent, does not appear to be present....

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

    Directory of Open Access Journals (Sweden)

    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.

  4. Metabolic activity of bacterial cells enumerated by direct viable count

    Energy Technology Data Exchange (ETDEWEB)

    Roszak, D.B.; Colwell, R.R.

    1987-12-01

    The direct viable count (DVC) method was modified by incorporating radiolabeled substrates in microautoradiographic analyses to assess bacterial survival in controlled laboratory microcosms. The DVC method, which permits enumeration of culturable and nonculturable cells, discriminates those cells that are responsive to added nutrients but in which division is inhibited by the addition of nalidixic acid. The resulting elongated cells represent all viable cells; this includes those that are culturable on routine media and those that are not. Escherichia coli and Salmonella enteritidis were employed in the microcosm studies, and radiolabeled substrates included (methyl-tritium thymidine or (Uranium-Carbon 14) glutamic acid. Samples taken at selected intervals during the survival experiments were examined by epifluorescence microscopy to enumerate cells by the DVC and acridine orange direct count methods, as well as by culture methods. Good correlation was obtained for cell-associated metabolic activity, measured by microautoradiography and substrate responsiveness (by the DVC method) at various stages of survival. Of the cells responsive to nutrients by the DVC method, ca 90% were metabolically active by the microautoradiographic method. No significant difference was observed between DVC enumerations with or without added radiolabeled substrate.

  5. Eradication of high viable loads of Listeria monocytogenes contaminating food-contact surfaces

    Directory of Open Access Journals (Sweden)

    Silvia ede Candia

    2015-07-01

    Full Text Available This study demonstrates the efficacy of cold gaseous ozone treatments at low concentrations in the eradication of high Listeria monocytogenes viable cell loads from glass, polypropylene, stainless steel and expanded polystyrene food-contact surfaces. Using a step by step approach, involving the selection of the most resistant strain-surface combinations, 11 Listeria spp. strains resulted inactivated by a continuous ozone flow at 1.07 mg m-3 after 24 or 48 h of cold incubation, depending on both strain and surface evaluated. Increasing the inoculum level to 9 log CFU coupon-1, the best inactivation rate was obtained after 48h of treatment at 3.21 mg m-3 ozone concentration when cells were deposited onto stainless steel and expanded polystyrene coupons, resulted the most resistant food-contact surfaces in the previous assays.The addition of naturally microbiologically contaminated meat extract to a high load of L. monocytogenes LMG 23775 cells, the most resistant strain out of the 11 assayed Listeria spp. strains, led to its complete inactivation after four days of treatment.To the best of our knowledge, this is the first report describing the survival of L. monocytogenes and the effect of ozone treatment under cold storage conditions on expanded polystyrene, a commonly-used material in food packaging. These results could be useful for reducing pathogen cross-contamination phenomena during cold food storage.

  6. Viable spore counts in biological controls pre-sterilization.

    Science.gov (United States)

    Brusca, María I; Bernat, María I; Turcot, Liliana; Nastri, Natalia; Nastri, Maria; Rosa, Alcira

    2005-01-01

    The aim of the present study was to evaluate the total count of viable spores in standardized inoculated carriers pre-sterilization. Samples of "Bacterial Spore Sterilization Strip" (R Biological Laboratories) (well before their expiry date) were divided into Group A (B. subtilis) and Group B (B. stearothermophylus). Twenty-four strips were tested per group. The strips were minced in groups of three, placed in chilled sterile water and vortexed for 5 minutes to obtain a homogenous suspension. Ten ml of the homogenous suspension were transferred to two sterile jars, i.e. one jar per group. The samples were then heated in a water bath at 95 degrees C (Group A) or 80 degrees C (Group B) for 15 minutes and cooled rapidly in an ice bath at 0- 4 degrees C during 15 minutes. Successive dilutions were performed until a final aliquot of 30 to 300 colony-forming units (CFU) was obtained. The inoculums were placed in Petri dishes with culture medium (soy extract, casein agar adapted for spores, melted and cooled to 45-50 degrees C) and incubated at 55 degrees C or 37 degrees C. Statistical analysis of the data was performed. A larger number of spores were found at 48 hours than at 24 hours. However, this finding did not hold true for all the groups. The present results show that monitoring viable spores pre-sterilization would guarantee the accuracy of the data. Total spore counts must be within 50 and 300% of the number of spores indicated in the biological control. The procedure is essential to guarantee the efficacy of the biological control.

  7. Detection of viable and dead Listeria monocytogenes on gouda-like cheeses by real-time PCR.

    Science.gov (United States)

    Rudi, K; Naterstad, K; Drømtorp, S M; Holo, H

    2005-01-01

    Surface contamination by Listeria monocytogenes of gouda-like cheeses during processing represents a potential public health problem. The aim of this work was to develop novel real-time PCR diagnostics to detect the presence of viable, dead or viable but not culturable (VBNC) cells on gouda-like cheeses. We used ethidium monoazide bromide (EMA)-PCR for direct quantification of viable and dead cells, while semiquantitative detection of culturable cells below the PCR detection limit (c. 100 CFU g(-1)) was obtained by combining growth and real-time PCR. We were able to quantify the fraction of >0.5% viable cells in a background of dead cells by EMA-PCR, given that the viable cell concentration was above the PCR detection limit. The combined growth and real-time PCR complemented the EMA-PCR, and enabled semiquantitative detection of low levels of culturable cells (10 and 100 CFU g(-1)). The significance of this work is that we have developed a novel concept for detection of viable and potentially infectious L. monocytogenes.

  8. Aerobic plate counts and ATP levels correlate with Listeria monocytogenes detection in retail delis.

    Science.gov (United States)

    Hammons, Susan R; Stasiewicz, Matthew J; Roof, Sherry; Oliver, Haley F

    2015-04-01

    Listeria monocytogenes is a foodborne pathogen that causes an estimated 1,591 cases of illness and 255 deaths annually in the United States, the majority of which are attributed to ready-to-eat deli meats processed in retail delis. Because retail delis distribute product directly to consumers, rapid methods to validate cleaning and sanitation are needed to improve retail food safety. This study investigated the relationships among ATP levels, standard aerobic plate count (APC), and L. monocytogenes presence in fully operational delis. Fifteen full-service delis were concurrently sampled for ATP, APC, and L. monocytogenes during preoperational hours once monthly for 3 months. Fifteen additional delis were recruited for 6 months of operational sampling (n = 30). A 1-log increase in APC was equivalent to a 3.3-fold increase in the odds of detecting L. monocytogenes (P < 0.001) and a 1.9-log increase in L monocytogenes population (P = 0.03). An ATP level increase of 1 log relative light unit correlated to a 0.22-log increase in APC (P < 0.001). A preoperational ATP level mean increase by 1 log relative light unit increased the odds of detecting L. monocytogenes concurrently fourfold. A 0.5-log increase in mean ATP level during preoperational sampling corresponded to a 2% increase in the predicted L. monocytogenes prevalence during operation (P < 0.01). Additionally, 10 statistically representative sites were identified and recommended for use in sanitation monitoring programs. Our data support the use of ATP as a rapid method to validate effective cleaning and sanitation to reduce L. monocytogenes in retail delis.

  9. Detection and enumeration of viable Listeria monocytogenes cells from ready-to-eat and processed vegetable foods by culture and DVC-FISH

    OpenAIRE

    Moreno Trigos, Mª Yolanda; SÁNCHEZ CONTRERAS, JAVIER; Montes Estellés, Rosa Mª; García Hernández, Jorge.; Ballesteros, Lorena; Ferrús Pérez, Mª Antonia

    2012-01-01

    Listeria monocytogenes is an important agent of foodborne disease, showing low prevalence but high mortality. There is evidence that vegetables are important vehicles of transmission, especially those minimally processed (fresh, fresh-cut vegetables under modified atmosphere packaging (MAP) or frozen) and directly exposed to consumers. The aim of this work was to detect and enumerate viable . L. . monocytogenes cells by culture and molecular methods from vegetable foods.A total of 191 vegetab...

  10. Detection of the total viable counts in chicken based on visible/near-infrared spectroscopy

    Science.gov (United States)

    Jiang, Fachao; Long, Yuan; Tang, Xiuying; Zhao, Linlin; Peng, Yankun; Wang, Caiping

    2014-05-01

    The viable counts in chicken have significant effects on food safety. Exceeding standard index can have negative influence to the public. Visible-near infrared spectra have had rapid development in food safety recently. The objective of this study was to detect the total viable counts in chicken breast fillets.36 chicken breast fillets used in the study were stored in a refrigerator at 4°C for 9 days. Each day four samples were taken and Vis/NIR spectra were collected from each sample before detecting their total viable counts by standard method. The original data was processed in four main steps: Savitzky-Golay smoothing method, standard normalized variate (SNV), model calibrating and model validating. Prediction model was established using partial least squares regression (PLSR) method. Several statistical indicators such as root mean squared errors and coefficients were calculated for determination of calibration and validation accuracy respectively. As a result, the Rc, SEC, Rv and SEV, of the best model were obtained to be 0.8854, 0.7455, 0.9070 and 0.6045 respectively, which demonstrate that visible-near infrared spectra is a potential technique to detect the total viable counts(TVC) in chicken and the best wavelengths for the establishment of the calibration model are near 449nm.

  11. The determination of viable counts in probiotic cultures microencapsulated by spray-coating.

    Science.gov (United States)

    Champagne, Claude P; Raymond, Yves; Tompkins, Thomas A

    2010-12-01

    An assessment of various methods to determine viable counts (CFU) in freeze-dried and dried microencapsulated (ME) probiotic cultures was carried out. Microencapsulation was done by spray-coating of dried Lactobacillus rhamnosus R0011 or Bifidobacterium longum ATCC 15708 cultures with fat. Rehydration of the ME powders was incomplete when they were added to water and gently agitated. As a result analytical methods based on vortexing of rehydrated ME cultures and which did not incorporate a high-shear homogenization (HSH) step underestimated the viable counts. The CFU of ME cultures were identical when methods using either blender or generator probes high-shear homogenization (HSH) were carried out. Furthermore HSH reduced the variability of the CFU results of both free-cell and ME cultures by a factor of three. The addition of an emulsifier (Tween 80) in the rehydrating medium to dissolve fat did not improve CFU counts when generator probes were used for HSH. The presence of fat in the ME product, or when added to the rehydration medium, improved CFU counts of B. longum but not of L. rhamnosus. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

  12. Total viable bacterial count using a real time all-fibre spectroscopic system.

    Science.gov (United States)

    Bogomolny, E; Swift, S; Vanholsbeeck, F

    2013-07-21

    Rapid, accurate and sensitive enumeration of bacterial populations in the natural environment is an essential task for many research fields. Widely used standard methods for counting bacteria such as heterotrophic plate count require 1 to 8 days of incubation time for limited accuracy, while more accurate and rapid techniques are often expensive and may require bulky equipment. In the present study, we have developed a computerized optical prototype for bacterial detection. The goal of this research was to estimate the potential of this optical system for Total Viable Bacterial Count in water. For this purpose, we tested water batches with different microbiological content. Bacterial detection was based on fluorescence enhanced by nucleic acid staining. High sensitivity was achieved by a stable diode pumped solid state laser, sensitive CCD spectrometer and in situ excitation and signal collection. The results have shown that the bacterial count from different water origins using our optical setup along with multivariate analysis presents a higher accuracy and a shorter detection time compared to standard methods. For example, in a case where the fluorescence signal is calibrated to the water batch regression line, the relative standard deviation of the optical system enumeration varies between 21 and 36%, while that of the heterotropic plate count counterpart varies between 41 and 59%. In summary, we conclude that the all-fibre optical system may offer the following advantages over conventional methods: near real time examinations, portability, sensitivity, accuracy and ability to detect 10(2) to 10(8) CFU per ml bacterial concentrations.

  13. ATP bioluminescence rapid detection of total viable count in soy sauce.

    Science.gov (United States)

    Yan, Shou-Lei; Miao, Su-Na; Deng, Shao-Ya; Zou, Min-Juan; Zhong, Fo-Sheng; Huang, Wen-Biao; Pan, Si-Yi; Wang, Qing-Zhang

    2012-01-01

    The adenosine triphosphate (ATP) bioluminescence rapid determination method may be useful for enumerating the total viable count (TVC) in soy sauce, as it has been previously used in food and beverages for sanitation with good precision. However, many factors interfere with the correlation between total aerobic plate counts and ATP bioluminescence. This study investigated these interfering factors, including ingredients of soy sauce and bacteria at different physiological stages. Using the ATP bioluminescence method, TVC was obtained within 4 h, compared to 48 h required for the conventional aerobic plate count (APC) method. Our results also indicated a high correlation coefficient (r = 0.90) between total aerobic plate counts and ATP bioluminescence after filtration and resuscitation with special medium. The limit of quantification of the novel detection method is 100 CFU/mL; there is a good linear correlation between the bioluminescence intensity and TVC in soy sauce in the range 1 × 10(2) -3 × 10(4) CFU/mL and even wider. The method employed a luminescence recorder (Tristar LB-941) and 96-well plates and could analyse 50-100 samples simultaneously at low cost. In this study, we evaluated and eliminated the interfering factors and made the ATP bioluminescence rapid method available for enumerating TVC in soy sauce.

  14. Short communication: appropriate and alternative methods to determine viable bacterial counts in cow milk samples.

    Science.gov (United States)

    Loss, G; Apprich, S; Kneifel, W; von Mutius, E; Genuneit, J; Braun-Fahrländer, C

    2012-06-01

    Farm milk consumption is reported to be inversely related to the development of asthma and atopy in children and it has been hypothesized that microorganisms in milk might contribute to this protective effect. The GABRIEL study was designed to investigate this hypothesis in a large population of European children, calling for a rapid alternative to classical culture techniques to determine bacteriological properties of milk samples. One objective was to evaluate 2 different rapid methods to determine bacteriological properties in a large number of cow milk samples collected under field conditions. BactoScan (Foss Analytical, Hillerød, Denmark), an automated standard flow cytometric method utilized for routine testing of milk quality, and TEMPO (bioMérieux, Marcy l'Etoile, France), an automated most-probable-number method, were used to assess the total viable bacterial count in farm and commercial milk samples. Both methods were compared with standard plate count method and each other. Measurements based on the TEMPO method were in good agreement with the standard plate count method and showed reliable results, whereas BactoScan results did not correlate with standard plate count measurements and yielded higher bacteria counts in heat-treated milk samples compared with raw milk samples. Most likely, these discrepant results were due to inferences with staining reactions and detection of bacteria in heat-treated milk samples. We conclude that, in contrast to the routinely used BactoScan method, the TEMPO method is an inexpensive and rapid alternative to standard culture methods suitable to assess total bacterial counts in processed and raw milk samples.

  15. Metabolic activity of bacterial cell enumerated by direct viable count. [Escherichia coli; Salmonella enteritidis

    Energy Technology Data Exchange (ETDEWEB)

    Roszak, D.B.; Colwell, R.R.

    1987-12-01

    The direct viable count (DVC) method was modified by incorporation radiolabeled substrates in microautoradiographic analyses to assess bacterial survival in controlled laboratory microcosms. The DVC method, which permits enumeration of culturable and nonculturable cells, discriminates those cells that are responsive to added nutrients but in which division is inhibited by the addition of nalidixic acid. The resulting elongated cells represent all viable cells; this includes those that are culturable on routine media and those that are not. Escherichia coli and Salmonella enteritidis were employed in the microcosm studies, and radiolabeled substrates included (methyl-/sup 3/H) thymidine or (U-/sup 14/C) glutamic acid. Samples taken at selected intervals during the survival experiments were examined by epifluorescence microscopy to enumerate cells by the DVC and acridine orange direct count methods, as well as by culture methods. Good correlation was obtained for cell-associated metabolic activity, measured by microautoradiography and substrate responsiveness (by the DVC method) at various stages of survival. Of the cells responsive to nutrients by the DVC method, ca. 90% were metabolically active by the microautoradiographic method. No significant difference was observed between DVC enumerations with or without added radiolabeled substrate.

  16. EVALUATION OF THE USE OF DIFFERENT ANTIBIOTICS IN THE DIRECT VIABLE COUNT METHOD TO DETECT FECAL ENTEROCOCCI

    Science.gov (United States)

    The detection of fecal pollution is performed via culturing methods in spite of the fact that culturable counts can severely underestimate the densities of fecal microorganisms. One approach that has been used to enumerate bacteria is the direct viable count method (DVC). The ob...

  17. Establishment of PMA-LAMP for detection of viable Listeria monocytogenes%PMA-LAMP检测单增李斯特活菌方法白勺建立

    Institute of Scientific and Technical Information of China (English)

    蒋亚男; 满朝新; 赵凤; 刘颖; 薛玉清; 胡惠秩; 李博; 姜毓君

    2011-01-01

    建立一种将荧光染料Propidium Monoazide(PMA)与环介导等温扩增(LAMP)相结合的检测方法,用于高效检测活的单核细胞增多性李斯特氏菌(简称单增李斯特菌).利用PMA抑制单增李斯特死菌后进行LAMP扩增实验、并研究了PMA-LAMP方法检测单增李斯特活菌的灵敏度,同时与PMA-PCR方法灵敏度进行比较.结果表明,50μmol/L的PMA处理浓度为5×108cfu/mL单增李斯特死菌,能够完全抑制LAMP扩增.PMA-LAMP方法检测单增李斯特活菌的检出限为4.9×10-1cfu/mL,其灵敏度是PMA-PCR方法的10倍.该方法可以作为一种快速检测单增李斯特活菌的新技术.%In order to effectively detect viable Listeria monocytogenes, a new method was developed by combination of propidium monoazide (PMA) and loop-mediated isothermal amplification (LAMP).The dead Listeria monocytogenes of LAMP amplification were inhibited by PMA treated, the detection sensitivity of PMA - LAMP method for viable Listeria monocytogenes was analyzed.This method was compared with the PMA-PCR method. Treated with 50 μmoL PMA,LAMP amplification were inhibited.The determination limit of PMA-LAMP method was 4.9×101 cfu/mL for viable Listeria monocytogenes. It' s sensitivity was 10 times than the PMA - PCR method. Therefore PMA-LAMP method was an effective technology with high specificity and sensitivity to detect viable Listeria monocytogenes.

  18. 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.

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

    Science.gov (United States)

    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.

  20. Improving prediction of total viable counts in pork based on hyperspectral scattering technique

    Science.gov (United States)

    Tao, Feifei; Peng, Yankun; Song, Yulin; Guo, Hui; Chao, Kuanglin

    2012-05-01

    A hyperspectral scattering technique was investigated for predicting the total viable counts (TVC) of pork in the article. Fresh pork was purchased from a local market and stored at 4°C for 1-15 days. Totally 35 samples were used in the experiment and 2-4 samples were taken out randomly each day for collecting hyperspectral images and reference microbiological tests. Gompertz function was applied to fit the scattering profiles of pork and Teflon, and the fitting results were pretty good in the spectral range of 470-1010 nm. Both individual parameters and integrated parameters were explored to develop the multi-linear regression models for predicting pork TVC, and the results indicated that individual Gompertz parameter α was superior to other individual parameters, while the integrated parameters can perform better. The best result for predicting pork TVC was achieved by the form of (α, β, ɛ), with the RCV of 0.963. The study demonstrated that hyperspectral scattering technique combined with Gompertz function was potential for rapid determination of pork TVC, and would be a valid tool for monitoring the quality and safety attributes of meat in the future.

  1. Combined action of nisin and carvacrol on Bacillus cereus and Listeria monocytogenes

    NARCIS (Netherlands)

    Pol, I.E.; Smid, E.J.

    1999-01-01

    Nisin, a small antimicrobial protein, was tested for its bactericidal action against Listeria monocytogenes and Bacillus cereus and a typical biphasic reduction of the viable count was observed. The reduction was most fast during the first 10 min of exposure, while the viable count remained stable i

  2. 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.

  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. Rapid Detection of Viable Microorganisms Based on a Plate Count Technique Using Arrayed Microelectrodes

    Directory of Open Access Journals (Sweden)

    Behraad Bahreyni

    2013-06-01

    Full Text Available Development of a miniaturized biosensor system that can be used for rapid detection and counting of microorganisms in food or water samples is described. The developed microsystem employs a highly sensitive impedimetric array of biosensors to monitor the growth of bacterial colonies that are dispersed across an agar growth medium. To use the system, a sample containing the bacteria is cultured above the agar layer. Using a multiplexing network, the electrical properties of the medium at different locations are continuously measured, recorded, and compared against a baseline signal. Variations of signals from different biosensors are used to reveal the presence of bacteria in the sample, as well as the locations of bacterial colonies across the biochip. This technique forms the basis for a label-free bacterial detection for rapid analysis of food samples, reducing the detection time by at least a factor of four compared to the current required incubation times of 24 to 72 hours for plate count techniques. The developed microsystem has the potential for miniaturization to a stage where it could be deployed for rapid analysis of food samples at commercial scale at laboratories, food processing facilities, and retailers.

  5. Research on the Forecast Model of Total Viable Count on Bacon Based on Hyper spectral Imaging Technique

    Directory of Open Access Journals (Sweden)

    Zhao Junhua

    2016-01-01

    Full Text Available The total viable count (TVC in bacon overweight can cause serious damage to human health. In order to find a rapid and nondestructive method of TVC, hyper spectral imaging technique was applied to quantitatively analysis of TVC on bacon. Comprehensively comparing the pretreatment method of multiple scattering, derivative method and so on finally the multiple scattering for pretreatment was used. And the interval optimization method of least squares model was set up to predict, and get a good prediction results. The correlation coefficient of the calibration and predictions respectively was 0.808 and 0.808, interactive authentication root mean square error was 0.115 and 0.198 respectively. Therefore, hyper spectral imaging technique combining iPLS can be used for the rapid detection of TVC on bacon.

  6. The survival of Listeria monocytogenes during long term desiccation is facilitated by sodium chloride and organic material

    DEFF Research Database (Denmark)

    Vogel, Birte Fonnesbech; Hansen, Lisbeth Truelstrup; Mordhorst, Hanne

    2010-01-01

    One specific DNA-subtype, as determined by RAPD, of Listeria monocytogenes persisted in a fish slaughterhouse for years, even during months with no production where the plant was cleaned and kept dry. We hypothesised that tolerance to desiccation could be a factor in explaining the persistence of L...... monocytogenes in food processing environments and the purpose of the present study was to determine ability of L monocytogenes to survive desiccation on stainless steel under simulated food processing conditions. Viable counts of eight different L. monocytogenes strains exposed to different soils and relative...... humidities (RHs) during desiccation decreased significantly (p...

  7. A Nondestructive Real-Time Detection Method of Total Viable Count in Pork by Hyperspectral Imaging Technique

    Directory of Open Access Journals (Sweden)

    Xiaochun Zheng

    2017-02-01

    Full Text Available A nondestructive method was developed for assessing total viable count (TVC in pork during refrigerated storage by using hyperspectral imaging technique in this study. The hyperspectral images in the visible/near-infrared (VIS/NIR region of 400–1100 nm were acquired for fifty pork samples, and their VIS/NIR diffuse reflectance spectra were extracted from the images. The reference values of TVC in pork samples were determined by classical microbiological plating method. Both partial least square regression (PLSR model and support vector machine regression model (SVR of TVC were built for comparative analysis to achieve better results. Different transformation methods and filtering methods were applied to improve the models. The results show that both the optimized PLSR model and SVR model can predict the TVC very well, while the SVR model based on second derivation was better, which achieved with RP (correlation coefficient of prediction set = 0.94 and SEP (standard error of prediction set = 0.4570 log CFU/g in the prediction set. An image processing algorithm was then developed to transfer the prediction model to every pixel of the image of the entire sample; the visualizing map of TVC would be displayed in real-time during the detection process due to the simplicity of the model. The results demonstrated that hyperspectral imaging is a potential reliable approach for non-destructive and real-time prediction of TVC in pork.

  8. Magnetic nano-beads based separation combined with propidium monoazide treatment and multiplex PCR assay for simultaneous detection of viable Salmonella Typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes in food products.

    Science.gov (United States)

    Yang, Youjun; Xu, Feng; Xu, Hengyi; Aguilar, Zoraida P; Niu, Ruijiang; Yuan, Yong; Sun, Jichang; You, Xingyong; Lai, Weihua; Xiong, Yonghua; Wan, Cuixiang; Wei, Hua

    2013-06-01

    We developed a rapid and reliable technique for simultaneous detection of Salmonella Typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes that can be used in food products. Magnetic nano-beads (MNBs) based immunomagnetic separation (IMS) was used to separate the target bacterial cells while multiplex PCR (mPCR) was used to amplify the target genes. To detect only the viable bacteria, propidium monoazide (PMA) was applied to selectively suppress the DNA detection from dead cells. The results showed the detection limit of IMS-PMA-mPCR assay was about 10(2) CFU/ml (1.2 × 10(2) CFU/ml for S. Typhimurium, 4.0 × 10(2) CFU/ml for E. coli O157:H7 and 5.4 × 10(2) CFU/ml for L. monocytogenes) in pure culture and 10(3) CFU/g (5.1 × 10(3) CFU/g for S. Typhimurium, 7.5 × 10(3) CFU/g for E. coli O157:H7 and 8.4 × 10(3) CFU/g for L. monocytogenes) in spiking food products samples (lettuce, tomato and ground beef). This report has demonstrated for the first time, the effective use of rapid and reliable IMS combined with PMA treatment and mPCR assay for simultaneous detection of viable S. Typhimurium, E. coli O157:H7 and L. monocytogenes in spiked food samples. It is anticipated that the present approach will be applicable to simultaneous detection of the three target microorganisms for practical use.

  9. Influence of addition of different antibiotics in semen diluent on viable bacterial count and spermatozoal viability of Awassi ram semen

    Directory of Open Access Journals (Sweden)

    O I Azawi

    2012-04-01

    Full Text Available The objectives of the present study were to determine the effects of six different antibiotics in controlling the growth of semen contaminating bacteria and if these antibiotics have any adverse effect on Awassi ram spermatozoa. Semen samples from six mature Awassi rams were used in this study. A total number of 120 ejaculates were collected from the rams using an artificial vagina once a week. Semen ejaculates were evaluated for volume, sperm concentration, mass motility, individual motility, percentage live sperm, sperm abnormalities, and viable bacterial count. Semen samples were diluted by sodium citrate-fructose-egg yolk. The diluted semen sample was divided into 7 parts. Six types of antibiotics were added to the semen diluent parts including; penicillin G 1000 IU ml-1 with streptomycin 1 mg ml-1, gentamicin sulphate 250 mg ml-1, tetracycline 0.5 mg ml-1, lincomycin 1 mg ml-1, cefoperazone sodium 1mg ml-1, cefdinir 1 mg ml-1 and the seventh part considered as a control group without antibiotic addition. The diluted semen samples were cooled and preserved at 5 Co for 5 days. Cooled diluted semen samples were examined for individual motility, percent of live sperm, sperm abnormalities, acrosomal defects and bacterial count every 24 h until 5 days. Comparing with the control, all the antibiotics examined were effective in controlling bacterial growth (P<0.05 from 24 h to 96 h of preservation at 5 Co. Cefdinir and cefoperazone sodium proved to be significantly (P<0.05 effective than other antibiotics in controlling bacterial growth at 96 h of preservation as the bacterial count were 23.3 ± 3.7 x 103 / ml and 25.4 ± 6.2 x 103 / ml, respectively. Lincomycin, gentamicin sulphate and tetracycline proved ineffective in controlling bacterial growth at 96 h of preservation as the bacterial count were 57.1 ± 20.1 x 103 / ml, 52.5 ± 29.4 x 103 / ml and 46.5 ± 8.8 x 103 / ml, respectively. The addition of tetracycline to diluted ram semen

  10. [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

  11. Detection and identification of viable Listeria monocytogenes by real-time PCR%实时荧光RT-PCR检测活性单核细胞增生李斯特菌方法的建立

    Institute of Scientific and Technical Information of China (English)

    金大智; 曹际娟; 张政; 谢明杰; 朱水荣

    2008-01-01

    目的 采用逆转录结合实时荧光定量PCR技术,建立一种快速、准确、特异甄别单核细胞增生李斯特菌(Listeria monocytogenes,简称单增李氏菌)死活状态的定量方法.方法 根据单增李氏菌hlyA基因序列设计引物和探针;对实时荧光PCR反应体系进行优化后,提取菌体mRNA,通过随机引物进行逆转录反应;产生的cDNA通过实时荧光定量PCR进行鉴定.进一步评价逆转录结合实时荧光定量PCR方法的特异性、灵敏度、重复性后,对20份模拟双盲样本进行检测.结果 本实验所建立的逆转录结合实时荧光定量PCR方法可准确、特异地检测单增李氏菌,其他菌株和失活的单增李氏菌均无阳性结果出现;该方法检测纯菌和模拟样本的灵敏度分别可达到10 CFU/ml和1000CFU/ml;定量检测的批间和批内的变异系数均小于5%;对20份模拟样本进行检测,其中10份含有活性单增李氏菌样本的检测结果均为阳性,其他含有失活单增李氏菌的5份样本和其他致病菌的5份样本检测结果为阴性.结论 本文建立的检测活性单增李氏菌实时荧光定量PCR方法快速、准确,结果可靠,实用性强,可进行定量分析,为食品安全监测和现场流行病学调查提供较好的分析手段和完整的数据.%Objective To establish a rapid,sensitive and specific assay based on real-time PCR combined with reverse transcription for detecting and identifying viable Listeria monocytogenes.Methods The hlyA gene of Listeria monocytogenes was chosen as target,and then the primers and TaqMan probe were designed.Both ends of probe were modified with two different fluorescence groups.The PCR reaction was optimized systematically.The mRNA of Listeria monocytogenes was extracted,and then reverse transcription was performed through random primer.The cDNA Was detected by real-time PCR.Then the specificity,sensitivity and reproducibility of real-time PCR were estimated.In final,real-time PCR

  12. Rapid Detection and Discrimination Viable Cell of Listeria monocytogenes by EMA-LAMP Assay%EMA-LAMP方法快速鉴别检测单增李斯特菌

    Institute of Scientific and Technical Information of China (English)

    吕淑霞; 徐彬; 于晓丹; 金雪花; 林英

    2012-01-01

    作者建立一种将叠氮溴化乙锭(ethidium bromide monoazide,EMA)结合环介导等温扩增(loop-mediated isothermal amplification,LAMP)的新分析方法(EMA-LAMP),快速鉴别检测单增李斯特菌.通过对单增李斯特菌hly基因的六个区域设计4条LAMP特异性引物,EMA-LAMP在63℃下反应lh,检测单增李斯特菌的死活细胞.结果表明,在浓度为2.0×108 CFU/mL的单增李斯特死菌悬液中,使EMA激活光解进入死细胞中且与DNA结合的最佳曝光时间至少为20 min,不抑制活菌细胞DNA的LAMP扩增的最大EMA质量浓度为10μg/mL,而抑制死菌细胞DNA的LAMP扩增的最小EMA质量浓度为4.0 μg/mL;活菌细胞的检出限为20 CFU/mL.%Viable cells of Listeria monocytogenes could be selectively discriminated from dead cells by applying Ethidium bromide monoazide (EMA) cooperated into loop -mediated isothermal amplification (LAMP) assay. The EMA-LAMP method was used for the rapid detection and identification of foodborne pathogene Listeria monocytogenes. The amplification can be obtained in an hour under the isothermal condition at 63℃ by designing four LAMP specifically primers from the six different sequences on the hly gene. The EMA-LAMP assay discriminated the viable and dead cells of Listeria monocytogenes. The result showed that the optimized light exposure time to achieve cross-linking of DNA by the EMA in dead cells and to photolyse the free EMA in solution was at least 20 min,and the use of 10 μg/ml or less of EMA did not inhibit the LAMP amplification of DNA derived from viable cells,but the minimum concentration of EMA to completely inhibit the LAMP amplification of DNA derived from dead cells was 4.0 μg/ml; a detection limit of the assay for the viable cells was 20 CFU/ml.

  13. Change in viable bacterial count during preservation of milk derived from dairy cows with subclinical mastitis and its relationship with antimicrobial components in milk

    Science.gov (United States)

    HISAEDA, Keiichi; KOSHIISHI, Tomoko; WATANABE, Masako; MIYAKE, Hajime; YOSHIMURA, Yukinori; ISOBE, Naoki

    2016-01-01

    The objectives of the present study were to investigate the change in the number of viable pathogens during preservation of milk obtained from cows with subclinical mastitis and the association between the decreasing ratio of viable bacteria during preservation and the somatic cell count (SCC) and the values of lingual antimicrobial peptide (LAP), lactoferrin (LF) and lactoperoxidase (LPO). After preservation of milk at room temperature for 0, 0.5, 1, 2, 3, 4 and 5 hr, the bacterial colonies in the milk were counted to determine the number of colony forming units (CFUs). Fresh skim milk was used to determine the values of LAP, LPO and LF. Bacteria were not detected in 19.4% of milk samples, and this percentage increased up to 30% after 5 hr of preservation. The number of Staphylococcus aureus and Streptococcus uberis in milk did not change significantly during the 5-hr incubation, whereas significant decreases were observed in the number of coliforms, coagulase-negative staphylococci, yeasts and Corynebacterium bovis. High SCC significantly decreased CFUs of S. aureus and yeast after preservation of milk for 4 to 5 hr. High LF concentration in milk was associated with decrease in CFU of S. aureus during 4-hr preservation. These results suggest that the viable counts of some pathogens in milk decreased during preservation at room temperature after collection, which may be attributed to the leukocytes and antimicrobial components present in milk. PMID:27109069

  14. 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.

  15. Microbial quality of lamb carcasses during processing and the acridine orange direct count technique (a modified DEFT) for rapid enumeration of total viable counts.

    Science.gov (United States)

    Sierra, M L; Sheridan, J J; McGuire, L

    1997-04-29

    This study was designed to set up a hazard analysis and critical control points (HACCP) system for sheep slaughtering operations at four different plants in Ireland and to determine the differences between plants in terms of microbial contamination. A single carcass area, the abdomen, was examined by swabbing and a microbiological profile was determined at different stages along the slaughter line. The level of contamination was assessed from the total bacteria counts, Enterobacteriaceae and Listeria spp. For the total counts, a modified direct epifluorescent filter technique (acridine orange direct count technique (AODC)) was developed and tested. No significant differences were found among plants in the levels of bacterial contamination. This was observed for all groups of organisms. The rapid direct technique (AODC) was found to be very successful. A correlation coefficient of 0.87 was obtained for this method and the standard plate count. Each test could be carried out in about 10-15 min and could be used to predict the standard plate count.

  16. 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 o

  17. Counting

    Institute of Scientific and Technical Information of China (English)

    许有国

    2005-01-01

    Most people began to count in tens because they had ten fingers on their hands. But in some countries, people counted on one hand and used the three parts of their four fingers. So they counted in twelves, not in tens.

  18. 环丙沙星作DNA抑制剂应用于活菌直接计数%Ciprofloxacin Used as DNA Inhibitor in Direct Viable Count

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Four bacteria including two G+ bacteria-Corynebacteri um pekinense and Bacillus subtilis and two G- bacteria-Vibrio cholerae and Es cherichia coli O157:H7 were treated with different concentrations of Ciprofloxac in lactate resulted in larger and longer bacteria than normal.The viable bacteri al count recorded by Ciprofloxacin lactate acting as inhibitor of cell divesion was similar to that of Nalidixic acid method.It was also found that viable G+ bacteria counted in this way showed a better result than the conventional plate couting method.%参照Isabel方法用不同浓度的环丙沙星(Ciprofl oxacin),处理两株革兰氏阳性菌;北京棒状杆菌(Corynebacterium pakinense);枯草芽 孢杆菌(Bacillus subtilis)和两株革兰氏阴性菌:霍乱弧菌(Vibrio cholerae)和大肠杆 菌 O157:H7(Escherichia coli O157:H7)。结果发现经乳酸环丙沙星处理后的细菌形 态均变长变大,计数结果表明环丙沙星处理的细菌的活菌直接计数与用萘啶酮酸(Nalidixic acid)处理的活菌直接计数法(DVC)结果相似,高于平板菌落计数结果,而且对部分革兰氏 阳性菌也可应用此法进行活菌直接计数。

  19. Inhibition of Listeria monocytogenes in cold-smoked salmon by Carnobacterium piscicola CS526 isolated from frozen surimi.

    Science.gov (United States)

    Yamazaki, Koji; Suzuki, Minako; Kawai, Yuji; Inoue, Norio; Montville, Thomas J

    2003-08-01

    Strain CS526 was isolated from frozen surimi and identified as a bacteriocin producer that had strong inhibitory activity against Listeria monocytogenes. Strain CS526 was identified as Carnobacterium piscicola by partial 16S rDNA sequence similarity. The ability of this bacteriocinogenic strain and nonbacteriocinogenic C. piscicola JCM5348 to inhibit the growth of L. monocytogenes was examined in culture broth incubated at 12 degrees C and cold-smoked salmon stored at 4, 12, and 20 degrees C. L. monocytogenes viable counts in the culture broth rapidly declined from 10(6) colony-forming units per ml to less than 10 colony-forming units per ml within 1 day at 12 degrees C in the presence of C. piscicola CS526. At 4 and 12 degrees C, inhibition of L. monocytogenes on salmon depended on the initial inoculum level of C. piscicola CS526. However, C. piscicola CS526 was bactericidal to L. monocytogenes within 21 and 12 days at 4 and 12 degrees C in cold-smoked salmon, respectively, even when the initial inoculum levels were low. C. piscicola CS526 suppressed the maximum cell number of L. monocytogenes by two and three log cycles, even at 20 degrees C. However, C. piscicola JCM5348 did not prevent the growth of the pathogen, except at 4 degrees C. Bacteriocin was detected in the samples coinoculated with C. piscicola CS526. The study shows that C. piscicola CS526 might have potential for biopreservation of refrigerated foods against L. monocytogenes.

  20. Efficacy of activated alginate-based nanocomposite films to control Listeria monocytogenes and spoilage flora in rainbow trout slice.

    Science.gov (United States)

    Alboofetileh, Mehdi; Rezaei, Masoud; Hosseini, Hedayat; Abdollahi, Mehdi

    2016-01-01

    Essential oils of clove, coriander, caraway, marjoram, cinnamon, and cumin were tested for their antilisterial activity by application of agar diffusion assay (experiment 1). Marjoram essential oil (MEO) showed the highest inhibitory effect, followed by clove and cinnamon. Subsequently, these essential oils were incorporated to alginate/clay nanocomposite films and antilisterial effectiveness of the films was studied in a model solid food system during 12 days at 10 °C (experiment 2). The results revealed that the films with MEO were more effective against Listeria monocytogenes in the model step. Finally, alginate-clay film incorporating 1 % MEO was applied to inoculated trout slices during refrigerated storage (4 °C) for 15 days (experiment 3). The control and the wrapped fish samples were analyzed periodically for microbiological (L. monocytogenes, total viable count, psychrotrophic count) and chemical (TVB-N) properties. The results demonstrated that alginate-clay films enriched with 1 % MEO significantly delayed the growth of L. monocytogenes during the 15-day storage with final counts reaching 6.23 log CFU/g while the counts in control samples were significantly higher reaching 7.38 log CFU/g (p < 0.05). Furthermore, active films efficiently reduced total viable count and psychrotrophic count as well as TVB-N in the fish slice during refrigerated storage.

  1. Antimicrobial Activity of Chitosan Films With Essential Oils Against Listeria monocytogenes on Cabbage

    Science.gov (United States)

    Jovanovic, Gordana D.; Klaus, Anita S.; P. Niksic, Miomir

    2016-01-01

    Background The highest incidence of listeriosis, due to consumption of ready-to-eat foods and fresh, shredded, minimally processed vegetables, occurs among pregnant women and the elderly. In order to reduce the prevalence of listeriosis among consumers, better protective measures are recommended. Chitosan films, with or without added essential oils, represent a modern, safe method of preserving the quality of such vegetables and significantly reducing the incidence of Listeria monocytogenes in these foods. Objectives The present study was conducted to evaluate the antimicrobial properties of composite chitosan-gelatin films with and without essential oils against two strains of L. monocytogenes, ATCC 19115 and ATCC 19112, in fresh shredded cabbage. Methods Shredded cabbage was inoculated with L. monocytogenes and packed between two layers of the chitosan composite film, then placed in Petri dishes. The prepared samples were stored at 4°C then analyzed for total viable count on PALCAM agar while incubated at 37°C, every 24 hours for 7 days. Results Average L. monocytogenes content ranged from 4.2 - 5.4 log CFU/g, reaching values of 7.2 - 8.6 log CFU/g in samples of untreated cabbage. A complete reduction of L. monocytogenes ATCC 19115 on cabbage was achieved after 120 hours in the presence of 0.5% chitosan film, whereas reduction of L. monocytogenes ATCC 19112 was achieved after 144 hours. In the presence of 1% chitosan film, the bacteria withered more quickly and complete reduction of both species of L. monocytogenes was achieved after 96 hours. Conclusions All tested formulations of chitosan films exhibited strong antimicrobial activity on the growth of both strains of L. monocytogenes on cabbage. The best effect was achieved with a 1% chitosan concentration. The addition of essential oils increased the antimicrobial activity of all tested films. PMID:27800143

  2. The survival of Listeria monocytogenes during long term desiccation is facilitated by sodium chloride and organic material.

    Science.gov (United States)

    Vogel, Birte Fonnesbech; Hansen, Lisbeth Truelstrup; Mordhorst, Hanne; Gram, Lone

    2010-06-15

    One specific DNA-subtype, as determined by RAPD, of Listeria monocytogenes persisted in a fish slaughterhouse for years, even during months with no production where the plant was cleaned and kept dry. We hypothesised that tolerance to desiccation could be a factor in explaining the persistence of L. monocytogenes in food processing environments and the purpose of the present study was to determine ability of L. monocytogenes to survive desiccation on stainless steel under simulated food processing conditions. Viable counts of eight different L. monocytogenes strains exposed to different soils and relative humidities (RHs) during desiccation decreased significantly (pDesiccation in physiological peptone saline (PPS) reduced survivors by 3-5 log units whereas bacterial cells suspended in bacteriological growth substrates (tryptone soy broth with 1% glucose, TSB-glu) or PPS with 5% NaCl only were reduced by 1-3 log units. At RHs of 2, 43 and 75%, surfaces were visibly dry after 1, 3 and 5days of incubation, respectively. The lowest RH resulted in the most significant loss of viability, however, 10(3)-10(4)CFU/cm(2) remained viable regardless of the desiccation treatment (i.e., presence of TSB-glu and/or salt). At 75% RH, the bacterial counts remained almost constant when desiccated in TSB-glu. When bacteria were grown and desiccated (15 degrees C, 43% RH) in salmon or smoked salmon juice, survivors decreased slowly resulting in low numbers (10(2)-10(3)CFU/cm(2)) from all eight strains remaining viable after 3months. Whilst conditions during desiccation had a pronounced influence on inactivation kinetics and the number of survivors, persistent L. monocytogenes were not more tolerant to desiccation than presumed non-persistent isolates. Our study shows that the ability to survive for months during desiccated conditions may be a factor explaining the ability of L. monocytogenes to persist in food processing environments. Copyright 2010 Elsevier B.V. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    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.

  4. On the relations between viable bacteria counts and absorbency of fermented liquid of lactobacillus%乳酸菌培养液中活菌数与吸光度的关系研究

    Institute of Scientific and Technical Information of China (English)

    严佩峰; 张孔海; 李建芳

    2012-01-01

    This test studied on relations between viable bacteria counts and corresponding absorbency of fermented liquid using skim milk as culture medium.The result showed that the relation between viable bacteria counts and its absorbency is linear correlation while taking skim milk as culture medium in the fermented course.So we can infer viable bacteria counts in the fermented dairy products through determining its absorbency in the fermented course.%通过平板计数法测定脱脂乳为培养基的发酵液中乳酸菌的活菌数,并测其对应的吸光度,研究两者之间的相关关系。结果表明:在发酵过程中以脱脂乳为培养基的发酵液中乳酸菌的活菌数与吸光度之间呈线性相关关系。因此,通过测定发酵液的吸光度可以评定发酵乳制品中乳酸菌的活菌数。

  5. Control of Listeria monocytogenes growth in soft cheeses by bacteriophage P100

    Directory of Open Access Journals (Sweden)

    Elaine Nóbrega Gibson Silva

    2014-01-01

    Full Text Available The purpose of this study was to determine the effect of bacteriophage P100 on strains of Listeria monocytogenes in artificially inoculated soft cheeses. A mix of L. monocytogenes 1/2a and Scott A was inoculated in Minas Frescal and Coalho cheeses (approximately 10(5 cfu/g with the bacteriophage added thereafter (8.3 x 10(7 PFU/g. Samples were analyzed immediately, and then stored at 10 ºC for seven days. At time zero, 30 min post-infection, the bacteriophage P100 reduced L. monocytogenes counts by 2.3 log units in Minas Frescal cheese and by 2.1 log units in Coalho cheese, compared to controls without bacteriophage. However, in samples stored under refrigeration for seven days, the bacteriophage P100 was only weakly antilisterial, with the lowest decimal reduction (DR for the cheeses: 1.0 log unit for Minas Frescal and 0.8 log units for Coalho cheese. The treatment produced a statistically significant decrease in the counts of viable cells (p < 0.05 and in all assays performed, we observed an increase of approximately one log cycle in the number of viable cells of L. monocytogenes in the samples under refrigeration for seven days. Moreover, a smaller effect of phages was observed. These results, along with other published data, indicate that the effectiveness of the phage treatment depends on the initial concentration of L. monocytogenes, and that a high concentration of phages per unit area is required to ensure sustained inactivation of target pathogens on food surfaces.

  6. 凝乳工艺对功能性低脂干酪中活菌数的影响%Effects of curd process on viable count of functional low-fat cheese

    Institute of Scientific and Technical Information of China (English)

    杨玉红; 郝慧敏

    2012-01-01

    The viable count is an important indexes of functional low-fat cheese. This paper curd process low-fat cheese to functional The viable count was studied, aims to control curd process parameters and make cheese the viable count reach final functional food standards. Through to the single factor experiment and the orthogonal experiment research and analysis, and the results show that: the curd enzyme adding amount of 0.01%, curd 35 °C temperature, pH value of 6.2 curd, CaCl2 adding amount of 0.03%, cheese living bacterium number all can reach 107 mL"1, accord with functional low-fat cheese living bacterium number of requirement, and can obtain a relatively ideal experimental results.%活菌数是功能性低脂干酪的重要指标,本文就凝乳工艺过程对功能性低脂干酪活菌数的影响进行了研究,旨在通过控制凝乳工艺过程参数而使干酪最终活菌数达到功能性食品的标准.通过对单因素实验和正交实验研究与分析,结果表明:凝乳酶添加量0.01%,凝乳温度35℃,凝乳pH值为6.2,CaCl2添加量0.03%,干酪活菌数均能达到107 mL-1,符合功能性低脂干酪的活菌数要求,能够获得较为理想的实验效果.

  7. Effects of Curd Process on Viable Count of Functional Low-Fat Cheese%凝乳工艺对功能性低脂干酪中活菌数的影响

    Institute of Scientific and Technical Information of China (English)

    栗红生

    2012-01-01

    The viable count was the most important target of functional low-fat cheese.It great effected by cheese processing program,and the aim was to get a standard viable count in cheese by controlling the processing parameters.The single-factor tests,the orthogonal test,the range and the variance analysis were used.The result showed that: the rennet addition 0.01%,the curd temperature 35 ℃,the curd pH 6.2,the CaCl2 addition 0.03%,the viable count in cheese was achieve 107 CFU/mL,this consequence could consistent with the standard of functional low-fat cheese.%活菌数是功能性低脂干酪的重要指标,就凝乳工艺过程对功能性低脂干酪活菌数的影响进行了研究,旨在通过控制凝乳工艺过程参数而使干酪最终活菌数达到功能性食品的标准。通过对单因素试验和正交试验研究与分析,结果表明:凝乳酶添加量0.01%,凝乳温度35℃,凝乳pH 6.2,CaCl2添加量0.03%,干酪活菌数均能达到107CFU/mL,符合功能性低脂干酪的活菌数要求,能够获得较为理想的试验效果。

  8. Insufficient differentiation of live and dead Campylobacter jejuni and Listeria monocytogenes cells by ethidium monoazide (EMA) compromises EMA/real-time PCR.

    Science.gov (United States)

    Flekna, Gabriele; Stefanic, Polonca; Wagner, Martin; Smulders, Frans J M; Mozina, Sonja Smole; Hein, Ingeborg

    2007-06-01

    Recently, ethidium monoazide (EMA) has been proposed as a means of reducing the real-time PCR signal originating from free DNA and dead bacterial cells by selectively entering damaged cells and blocking the DNA for PCR amplification via photoactivation. The present study investigated the effect of EMA on viable and dead bacterial cells using real-time PCR, plate count method and microscopy. The foodborne pathogens Campylobacter jejuni and Listeria monocytogenes were used as a Gram-negative and a Gram-positive model organism, respectively. EMA/real-time PCR analysis of heat-treated cultures of C. jejuni and L. monocytogenes containing 2.6x10(5) and 4x10(5) viable and 3x10(6) and 2x10(6) dead cells/ml, respectively, yielded 2x10(3) and 5.2x10(4) bacterial cell equivalents/ml after EMA treatment, thus underestimating the viable cell count in the samples. Similar results were obtained when analyzing late exponential phase cultures of C. jejuni and L. monocytogenes. Inhibition of growth by EMA was observed. It depended on the concentration of the bacterial cells present in the sample and the EMA concentration used (100-1 microg/ml). An EMA concentration at which dead cells would stain brightly and viable cells would not stain at all or would be very pale was not identified, as revealed by comparison with the results of a commercial live/dead stain. The results suggest that EMA influences not only dead but also viable cells of C. jejuni and L. monocytogenes. Thus EMA/real-time PCR is a poor indicator of cell viability.

  9. Microwave oven heating for inactivation of Listeria monocytogenes on frankfurters before consumption.

    Science.gov (United States)

    Rodríguez-Marval, Mawill; Geornaras, Ifigenia; Kendall, Patricia A; Scanga, John A; Belk, Keith E; Sofos, John N

    2009-10-01

    Microwave oven heating was evaluated for inactivation of Listeria monocytogenes on inoculated and stored frankfurters. Frankfurters formulated without/with 1.5% potassium lactate and 0.1% sodium diacetate were inoculated with L. monocytogenes (1.9 +/- 0.2 log CFU/cm(2)), vacuum-packaged, and stored (4 degrees C) to simulate conditions prior to purchase by consumers. At storage days 18, 36, and 54, packages were opened and placed at 7 degrees C, simulating aerobic storage in a household refrigerator. At 0, 3, and 7 d of aerobic storage, 2 frankfurters were placed in a bowl with water (250 mL) and treated in a household microwave oven at high (1100 W) power for 30, 45, 60, or 75 s, or medium (550 W) power for 60 or 75 s. Frankfurters and the heating water were analyzed for total microbial counts and L. monocytogenes populations. Exposure to high power for 75 s reduced pathogen levels (0.7 +/- 0.0 to 1.0 +/- 0.1 log CFU/cm(2)) to below the detection limit ( 1.5 and 5.9 log CFU/cm(2) from control levels of 1.5 +/- 0.1 to 7.2 +/- 0.5 log CFU/cm(2). Depending on treatment and storage time, the water used to reheat the frankfurters had viable L. monocytogenes counts of microwave oven at high power for 75 s to inactivate up to 3.7 log CFU/cm(2) of L. monocytogenes contamination.

  10. Listeria monocytogenes virulence factor Listeriolysin O favors bacterial growth in co-culture with the ciliate Tetrahymena pyriformis, causes protozoan encystment and promotes bacterial survival inside cysts

    Directory of Open Access Journals (Sweden)

    Ermolaeva Svetlana A

    2010-01-01

    Full Text Available Abstract Background The gram-positive pathogenic bacterium Listeria monocytogenes is widely spread in the nature. L. monocytogenes was reported to be isolated from soil, water, sewage and sludge. Listeriolysin O (LLO is a L. monocytogenes major virulence factor. In the course of infection in mammals, LLO is required for intracellular survival and apoptosis induction in lymphocytes. In this study, we explored the potential of LLO to promote interactions between L. monocytogenes and the ubiquitous inhabitant of natural ecosystems bacteriovorous free-living ciliate Tetrahymena pyriformis. Results Wild type L. monocytogenes reduced T. pyriformis trophozoite counts and stimulated encystment. The effects were observed starting from 48 h of co-incubation. On the day 14, trophozoites were eliminated from the co-culture while about 5 × 104 cells/ml remained in the axenic T. pyriformis culture. The deficient in the LLO-encoding hly gene L. monocytogenes strain failed to cause mortality among protozoa and to trigger protozoan encystment. Replenishment of the hly gene in the mutant strain restored toxicity towards protozoa and induction of protozoan encystment. The saprophytic non-haemolytic species L. innocua transformed with the LLO-expressing plasmid caused extensive mortality and encystment in ciliates. During the first week of co-incubation, LLO-producing L. monocytogenes demonstrated higher growth rates in association with T. pyriformis than the LLO-deficient isogenic strain. At latter stages of co-incubation bacterial counts were similar for both strains. T. pyriformis cysts infected with wild type L. monocytogenes caused listerial infection in guinea pigs upon ocular and oral inoculation. The infection was proved by bacterial plating from the internal organs. Conclusions The L. monocytogenes virulence factor LLO promotes bacterial survival and growth in the presence of bacteriovorous ciliate T. pyriformis. LLO is responsible for L. monocytogenes

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

    Directory of Open Access Journals (Sweden)

    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.

  12. 四唑鎓盐法快速检测布鲁杆菌疫苗活菌含量的建立%XTT(Tetrazolium salt)assay for rapid determination of Viable count of Brucella vaccine

    Institute of Scientific and Technical Information of China (English)

    刘景福; 李恪梅; 余菲菲; 王国治

    2011-01-01

    Objective To measure the live bacteria content of Brucella vaccine by XTT assay, and discuss the possibility that XTT would be a quick and simple method of detecting live bacteria content of Brucella vaccine. Methods XTT method was employed for Brucella vaccine. A linear regression was made between the absorbance of XTT and different concentrations of standard Brucella vaccine. The linear equation was used to read out the viable count of unknown samples by absorbance. Then the results were compared with the conventional viable count of the same samples. Results The optimum time of detecting Brucella vaccine was about 4 hours. The regression coefficient R2 might reach 0.997. The data of viable count of 10 lots of Brucella vaccine by the XTT assay and colony forming unit ( CFU ) demonstrated apositive correlation with correlation coefficient, r = 0. 879, P = 0.001. Conclusions The method XTT could show different concentrations of Brucella vaccine in a certain range. The assay can be applied for rapid determination of viable count of Brucella vaccine.%目的 通过四唑鎓盐(XTT)法检测布鲁杆菌疫苗的活菌含量,探讨XTT法快速检测布鲁杆菌活菌含量的可行性.方法 将XTT法运用于布鲁杆菌疫苗活菌含量的检测,通过已知活菌浓度的布鲁杆菌液,制备XTT法的吸光值与布鲁杆菌苗活菌含量的关系参比曲线,并根据制备的参比曲线同样运用XTT法检测未知浓度的104M菌液的活菌量,比较传统活菌集落计数(CFU)法与XTT法两者检测布鲁杆菌活菌含量的相关性.结果 XTT法检测布鲁杆菌疫苗的最佳时间应在4 h左右,在一定范围内XTF法所测得的吸光值与细菌活菌含量有较好的相关性,相关系数r=0.997.运用10瓶布鲁杆菌疫苗,通过XTT法与CFU法检测其活菌含量,两者结果相关性较好,Spearman相关系数为0.879,P=0.001.结论 XTT法能在一定活菌浓度范围反应布鲁杆菌疫苗活菌含量,可为快速检测布鲁杆菌活

  13. 高活菌数复合益生菌发酵乳工艺优化%Optimization of fermentation conditions of milk with blend probiotic strains based on high viable count

    Institute of Scientific and Technical Information of China (English)

    刘成国; 易文芝; 周辉

    2013-01-01

      The viable probiotic count is the key factor to functionality of fermented milk. It is very important for the milk industry to improve the number of viable bacteria in its final products. Lactobacillus casei and Bifidobacterium were blended using them as a starter culture for fermented milk to achieve a high viable probiotic count. Lactobacillus casei and Bifidobacterium were studied and a high density culture technology of Lactobacillus was applied to increase the number of viable bacteria in the fermentation system. Determination of the absorbance method was used to assess the viable count of probiotics in fermented milk in which the calcium ion would combine with salt under alkaline conditions to make fermented milk dispersed evenly in a solution state. Ethylenediamine Tetraacetic Acid (EDTA) was selected as a chelating agent to chelate the calcium ion in the fermented milk, and to make the solution clarify. The OD value of the bacteria did not change significantly after entering the stable phase, and the number of viable probiotics count in the fermented milk achieved the maximum. The OD value of fermented milk in this study did not change significantly from the second day of fermentation. On this basis, OD value was measured for three consecutive days from the second day, and the average OD value was used as indicator of the viable probiotic count.%  益生菌发酵乳中的活菌数是保证其功能特性的关键因素,为提高益生菌发酵乳中的活菌总数,以干酪乳杆菌和双歧杆菌复合菌种为试验对象,以发酵过程中的 pH 值和吸光度平均值OD值为试验指标,在单因素试验的基础上,利用 Box-Benhnken 中心组合试验和响应面分析法研究了接种量、益生菌接种比例、发酵温度、葡萄糖添加量以及大豆多肽添加量对发酵乳 pH 值和活菌数的影响,并建立了复合益生菌发酵模型。响应面优化试验结果表明复合益生菌发酵的最佳工艺

  14. A Method for Assessing the Total Viable Count of Fresh Meat Based on Hyperspectral Scattering Technique%光学扩散特征的生鲜肉细菌总数的无损检测方法

    Institute of Scientific and Technical Information of China (English)

    宋育霖; 彭彦昆; 郭辉; 张雷蕾; 赵娟

    2014-01-01

    The objective of this study is to develop a hyperspectral imaging system to predict the bacteria total viable count in fresh pork .The hyperspectral scattering data were curvefitted by different fitting methods ,and correlation differences of models were compared based on the bacteria total viable count of fresh pork ,thus providing modeling basis of device for future study . Total 63 fresh pork samples which was used in the experiment were stored at 4 ℃ in the refrigerator of constant temperature . Experiment was performed everyday for 15 days .4 or 5 random samples were used each day for the experiment .Hyperspectral scattering images and spectral scattering optical data in the wavelength region of 400 to 1 100 nm were acquired from the surface of all of the pork samples .Lorentz and Gompertz function and the modified function was applied to fit the scattering profiles of pork samples .Different parameters could be obtained by Lorentz and Gompertz fitting and the modified function fitting .The dif-ferent parameters could represent the optical characteristic of the scattering profiles .The standard values of the bacteria total vi-able count of pork were obtained by classical microbiological plating methods .Because the standard value of the bacteria total via-ble count was big ,log10 of the bacteria total viable count obtained by classical microbiological plating was used to simplify the calculation .Both individual parameters and integrated parameters were explored to develop the models .The multi-linear regres-sion statistical approach was used to establish the models for predicting pork the bacteria total viable count .Both Lorentz and Gompertz function and the modified function included three and four parameters formula .The results showed that correlation co-efficient of the models is higher with Lorentz three parameters combination ,Lorentz four parameters combination and Gompertz four parameters combination than the individual parameters and other two or

  15. The surfactant application of sodium deoxycholate in the EMA-PCR discrimination of viable and dead cells of Listeria monocytogenes%表面活性剂脱氧胆酸钠在单增李斯特菌死活细胞EMA-PCR鉴别中的应用

    Institute of Scientific and Technical Information of China (English)

    郝乐友; 吕淑霞; 张超; 于晓丹; 马镝; 曹慧颖

    2013-01-01

    通过脱氧胆酸钠(sodium deoxycholate,SD)结合染料叠氮溴乙锭(ethidium bromide monoazide,EMA)与PCR反应体系相结合,建立纯培养条件下区分单增李斯特菌死活细胞的方法,即SD-EMA-PCR鉴别单增李斯特菌死活细胞检测法.结果表明:向浓度为2.0×108 CFU/mL的单增李斯特死菌悬液中加入终浓度为1.5 mg/mL的表面活性剂脱氧胆酸钠后,EMA激活光解最佳曝光时间为25 min.SD-EMA-PCR检测体系中,对死菌细胞DNA的PCR扩增抑制的EMA最小浓度为1.6 μg/mL;而对活菌细胞DNA的PCR扩增不抑制的EMA最大浓度为9 μg/mL,活菌细胞的最低检出限为20 CFU/mL.SD-EMA-PCR检测法能够减小EMA-PCR漏检死菌细胞给检测结果带来假阳性的可能,降低了检测的成本,为单增李斯特菌的快速检测提供了一种新的有效途径.%Through the treatment of the sodium deoxycholate to the cells,Ethidium bromide monoazide was utilized to selectively allow the PCR amplification of a targeted DNA sequence in viable but not dead cells of Listeria monocytogenes,namely SD-EMA-PCR.The optimal concentration of sodium deoxycholate incorporating into the PCR system could enhance the discrimination of viable and dead cells.The results showed that:with the treatment of the Sodium deoxycholate,the optimized light exposure time to achieve cross-linking of DNA by the EMA in dead cells and to photolyse the free EMA in solution was at least 25 min,and the maximum concentration of EMA which did not inhibit the PCR amplification of DNA extracted from viable cells was 9 μg/mL.but the minimum concentration of EMA which completely inhibited the PCR amplification of DNA extracted from dead cells was 1.6 μg/mL; a detection limit of the assay for the viable cells was 20 CFU/mL.SD-EMA-PCR could minimize the possibility of the false-positive by the way of EMA-PCR and reduce the cost of detection.It is a new efficient approach for the rapid detection of the isolate of Listeria monocytogenes.

  16. The fate of Listeria monocytogenes in brine and on Gouda cheese following artificial contamination during brining

    NARCIS (Netherlands)

    Wemmenhove, E.; Beumer, R.R.; Hooijdonk, van A.C.M.; Zwietering, M.H.; Wells-Bennik, M.H.J.

    2014-01-01

    The fate of 3 different Listeria monocytogenes strains (Scott A, 2F and 6E) was studied independently in brine and on factory-scale Gouda cheeses that had been submerged in brine that was artificially contaminated with these individual strains. Viable numbers of L. monocytogenes in the brine

  17. Efficacy of preprocedural mouth rinse containing chlorine dioxide in reduction of viable bacterial count in dental aerosols during ultrasonic scaling: A double-blind, placebo-controlled clinical trial

    Directory of Open Access Journals (Sweden)

    Rajiv Saini

    2015-01-01

    Full Text Available Background: The risk to dentists, dental assistants, and patients of infectious diseases through aerosols has long been recognized. The aim of this study was to evaluate and compare the efficacy of commercially available preprocedural mouthrinses containing 0.2% chlorhexidine (CHX gluconate, chlorine dioxide (ClO 2 mouthwash, and water in reducing the levels of viable bacteria in aerosols. Materials and Methods: This single-center, double-blind, placebo-controlled, three-group parallel-designed study was conducted over a period of 4 months. One hundred twenty patients with chronic periodontitis were divided randomly into three groups (A, B, and C of 40 patients each to receive the ClO 2 mouthwash, water, and 0.2% CHX gluconate respectively as preprocedural rinse. The aerosol produced by the ultrasonic unit was collected at five standardized locations with respect to the reference point, i.e., the mouth of the patient. The blood agar plates were incubated at 37°C for 48 h, and the total number of colony-forming units (CFUs was counted and statistically analyzed. Results: The results showed that CFUs in groups A and C were significantly reduced compared to group B, and P 0.05. The numbers of CFUs were the highest at the patient′s chest area and lowest at the patient′s front i.e., the 6 o′clock position. Conclusion: This study proves that a regular preprocedural mouthrinse could significantly eliminate the majority of aerosols generated by the use of an ultrasonic unit, and that ClO 2 mouthrinse was found to be statistically equally effective in reducing the aerosol contamination to 0.2% CHX gluconate.

  18. Influence of salt, smoke, and high pressure on growth of Listeria monocytogenes and spoilage microflora in cold-smoked dolphinfish (Coryphaena hippurus).

    Science.gov (United States)

    Montero, P; Gómez-Estaca, J; Gómez-Guillén, M C

    2007-02-01

    The effects of different salting and smoking conditions on the growth of Listeria monocytogenes in cold-smoked dolphinfish (Coryphaena hippurus) fillets were evaluated. High concentrations of phenol (72.47 ppm) and salt (3.25%) in muscle inhibited L. monocytogenes growth in smoked fish stored at 20 degrees C for 4 days. The antibacterial effect of high pressure in cold-smoked dolphinfish during long-term chilled (5 degrees C) storage was evaluated in fillets prepared according to two different sets of salting and smoking conditions. Combining the milder salting and smoking conditions (1.97% salt and 42 ppm phenol) with a high pressure treatment of 300 MPa at 20 degrees C for 15 min sufficed to exert a bacteriostatic effect on the total viable bacteria, total lactic acid bacteria, and L. monocytogenes. However, in fillets prepared using the more severe salting and smoking conditions (2.93% salt and 82 ppm phenol), pressurization kept L. monocytogenes counts under the detection limit throughout 100 days of storage. A similar effect was obtained by dosing the fillets with nisin. No luminescent bacteria, hydrogen sulfide-producing bacteria, or Enterobacteriaceae were found in any of the fillets produced using either of the two sets of processing conditions.

  19. Effects of Two Application Methods of Plantaricin BM-1 on Control of Listeria monocytogenes and Background Spoilage Bacteria in Sliced Vacuum-Packaged Cooked Ham Stored at 4°C.

    Science.gov (United States)

    Zhou, Huimin; Xie, Yuanhong; Liu, Hui; Jin, Junhua; Duan, Huixia; Zhang, Hongxing

    2015-10-01

    Two application methods were used to investigate the effect of plantaricin BM-1 on the control of Listeria monocytogenes and background spoilage bacteria in sliced vacuum-packaged cooked ham without the addition of any chemical preservatives, including sodium nitrite, during 35 days of storage at 4°C. Regardless of the application method, plantaricin BM-1 treatment (320, 640, or 1,280 arbitrary units [AU]/g of sliced cooked ham) significantly (P < 0.05) reduced the survival of L. monocytogenes (inoculated at 4 log CFU/g of sliced ham) compared with its survival in the control during the first 21 days of storage at 4°C. The inhibitory effect of plantaricin applied to the surface of the ham was significantly better than the same concentration of plantaricin incorporated into the cooked ham (P < 0.0001) during storage. Even 320 AU/g plantaricin applied to the surface exhibited greater inhibition of L. monocytogenes than 1,280 AU/g plantaricin incorporated into the cooked ham on days 1, 14, and 28. A level of 1,280 AU/g plantaricin applied to the surface of the ham reduced L. monocytogenes counts to below the detection limit from the 1st to the 21st day of storage at 4°C. Afterwards, L. monocytogenes was able to regrow, and the viable counts of L. monocytogenes at the end of storage reached 2.76 log CFU/g (6.11 log CFU/g lower than in the control). In the control ham, the counts of background spoilage bacteria increased gradually and surpassed the microbiological spoilage limitation level on the 21st day of storage. However, plantaricin BM-1 treatment significantly (P < 0.05) reduced the survival of background spoilage bacteria in ham compared with their survival in the control from day 21 to 35 of storage at 4°C. A level of 1,280 AU/g plantaricin incorporated into cooked ham was the most effective, reducing the count of background spoilage bacteria count from an initial 2.0 log CFU/g to 1.5 log CFU/g on day 7. This was then maintained for another 14 days and

  20. 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.

  1. 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 aw 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/aw 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

  2. 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.

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

    Science.gov (United States)

    Furtado, Danielle N; Todorov, Svetoslav D; Landgraf, Mariza; Destro, Maria T; Franco, Bernadette D G M

    2015-03-01

    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.

  4. 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)....

  5. 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.

  6. 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 (Palginate coating solutions containing nisin, cinnamon, and rosemary EOs as natural preservatives is recommended in meat products especially in chicken meats. Copyright © 2016. Published by Elsevier B.V.

  7. The effect of sodium reduction with and without potassium chloride on the survival of Listeria monocytogenes in Cheddar cheese.

    Science.gov (United States)

    Hystead, E; Diez-Gonzalez, F; Schoenfuss, T C

    2013-10-01

    Sodium chloride (NaCl) in cheese contributes to flavor and texture directly and by its effect on microbial and enzymatic activity. The salt-to-moisture ratio (S/M) is used to gauge if conditions for producing good-quality cheese have been met. Reductions in salt that deviate from the ideal S/M range could result in changing culture acidification profiles during cheese making. Lactococcus lactis ssp. lactis or Lc. lactis ssp. cremoris are both used as cultures in Cheddar cheese manufacture, but Lc. lactis ssp. lactis has a higher salt and pH tolerance than Lc. lactis ssp. cremoris. Both salt and pH are used to control growth and survival of Listeria monocytogenes and salts such as KCl are commonly used to replace the effects of NaCl in food when NaCl is reduced. The objectives of this project were to determine the effects of sodium reduction, KCl use, and the subspecies of Lc. lactis used on L. monocytogenes survival in stirred-curd Cheddar cheese. Cheese was manufactured with either Lc. lactis ssp. lactis or Lc. lactis ssp. cremoris. At the salting step, curd was divided and salted with a concentration targeted to produce a final cheese with 600 mg of sodium/100 g (control), 25% reduced sodium (450 mg of sodium/100 g; both with and without KCl), and low sodium (53% sodium reduction or 280 mg of sodium/100 g; both with and without KCl). Potassium chloride was added on a molar equivalent to the NaCl it replaced to maintain an equivalent S/M. Cheese was inoculated with a 5-strain cocktail of L. monocytogenes at different times during aging to simulate postprocessing contamination, and counts were monitored over 27 or 50 d, depending on incubation temperature (12 or 5 °C, respectively). In cheese inoculated with 4 log₁₀ cfu of L. monocytogenes/g 2 wk after manufacture, viable counts declined by more than 3 log₁₀ cfu/g in all treatments over 60 d. When inoculated with 5 log₁₀ cfu/g at 3mo of cheese age, L. monocytogenes counts in Cheddar cheese were also

  8. Evidence of metabolically active but non-culturable Listeria monocytogenes in long-term growth at 10 °C.

    Science.gov (United States)

    Gurresch, Anna; Gerner, Wilhelm; Pin, Carmen; Wagner, Martin; Hein, Ingeborg

    2016-05-01

    Cultures of Listeria monocytogenes at low temperatures (10 °C) in a broth model revealed long-term survival at about 0.04% cell density in relation to the log phase. In contrast, direct viable counts and PMA real-time PCR data suggested that 50% and 1% of the population retain membrane integrity, respectively. To elucidate the observed difference, the metabolic activity of the bacterial population was investigated by multiparametric flow cytometry, including the assessment of membrane integrity, reductase activity, as well as forward and side scatter properties. These analyses were complemented by 16S rRNA real-time PCR. The majority of the cells retained their membrane integrity and reductase activity until day 29. On day 42, 48.00 ± 4.00% (L. monocytogenes strain 3251) and 68.67 ± 3.74% (L. monocytogenes strain 535) of the cells had intact membranes, whereas 57.23 ± 1.85% (strain 3251) and 74.97 ± 3.01% (strain 535) exhibited high reductase activity. On day 42, mean 16S rRNA copy numbers of 3.98 ± 1.37 (membrane integrity) and 3.86 ± 1.32 (reductase activity) remained per intact or active cell. Our data suggest the transition of L. monocytogenes into a state of metabolic dormancy during long-term culture at low temperature. Copyright © 2016. Published by Elsevier Masson SAS.

  9. 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

  10. Listeria monocytogenes endocarditis.

    Science.gov (United States)

    Sheinman, B D; Evans, T; Sage, R

    1985-01-01

    A fatal case of endocarditis due to Listeria monocytogenes is reported. Case reports of endocarditis due to this organism are rare but indicate a higher mortality than with many other causes of bacterial endocarditis. The size of the problem may be underestimated because the organism has a "diphtheroid' appearance and may be incorrectly dismissed as a contaminant.

  11. 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  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.

  12. The prevalence of Listeria monocytogenes and Staphylococcus aureus and their virulence genes in bulk tank milk in Kosovo.

    Science.gov (United States)

    Mehmeti, Ibrahim; Bytyqi, Hysen; Muji, Skender; Nes, Ingolf F; Diep, Dzung B

    2017-03-31

    Milk is considered to be a healthy, nutritious food product. Microbiological quality is an important aspect in evaluating the quality of milk. A total of 603 bulk tank milk samples from 221 farms distributed across ten different regions were collected for milk quality assessment. Quality was judged by total viable count, and the prevalence of two foodborne pathogens (Listeria monocytogenes and Staphylococcus aureus) by using selective media and 16S rRNA gene sequencing. The presence of virulence genes was detected by polymerase chain reaction (PCR) using specific primers. Milk from only 7% (15/221) of farms were found to comply with the European Union standard. Interestingly, the microbiological quality of milk from the larger herd size farms (more than 10 cows) was better than in smaller herds. L. monocytogenes was found in 2.7% (6/221) of farms, and all the examined L. monocytogenes isolates were positive with respect to the virulence genes prfA, actA, and hlyA. S. aureus was found in 39.8% (88/221) of the farms. In total, 30.7% (27/88) of the staphylococci were positive for enterotoxin production. The enterotoxins identified were toxin B (40.7%), toxin D (33.4%), toxin C (18.5%), and toxin A (7.4%). The total number of bacteria in milk was very high. The presence of two foodborne pathogens in raw milk represents a great health risk to consumers. To improve the microbial quality of milk in Kosovo, important measures to improve hygiene, including better information, guidance, and control, are needed.

  13. Evaluation of lactic acid bacterium fermentation products and food-grade chemicals to control Listeria monocytogenes in blue crab (Callinectes sapidus) meat.

    Science.gov (United States)

    Degnan, A J; Kaspar, C W; Otwell, W S; Tamplin, M L; Luchansky, J B

    1994-01-01

    Fresh blue crab (Callinectes sapidus) meat was obtained from retail markets in Florida and sampled for viable Listeria monocytogenes. The pathogen was found in crabmeat in three of four different lots tested by enrichment and at levels of 75 CFU/g in one of the same four lots by direct plating. Next, crabmeat was steam sterilized, inoculated with a three-strain mixture of L. monocytogenes (ca. 5.5 log10 CFU/g), washed with various lactic acid bacterium fermentation products (2,000 to 20,000 arbitrary units [AU]/ml of wash) or food-grade chemicals (0.25 to 4 M), and stored at 4 degrees C. Counts of the pathogen remained relatively constant in control samples during storage for 6 days, whereas in crabmeat washed with Perlac 1911 or MicroGard (10,000 to 20,000 AU), numbers initially decreased (0.5 to 1.0 log10 unit/g) but recovered to original levels within 6 days. Numbers of L. monocytogenes cells decreased 1.5 to 2.7 log10 units/g of crabmeat within 0.04 day when washed with 10,000 to 20,000 AU of Alta 2341, enterocin 1083, or Nisin per ml. Thereafter, counts increased 0.5 to 1.6 log10 units within 6 days. After washing with food-grade chemicals, modest reductions (0.4 to 0.8 log10 unit/g) were observed with sodium acetate (4 M), sodium diacetate (0.5 or 1 M), sodium lactate (1 M), or sodium nitrite (1.5 M). However, Listeria counts in crabmeat washed with 2 M sodium diacetate decreased 2.6 log10 units/g within 6 days. In addition, trisodium phosphate reduced L. monocytogenes counts from 1.7 (0.25 M) to > 4.6 (1 M) log10 units/g within 6 days.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7944362

  14. 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.

  15. Fate of Listeria monocytogenes in Gouda microcheese: No growth, and substantial inactivation after extended ripening times

    NARCIS (Netherlands)

    Wemmenhove, E.; Stampelou, I.; Hooijdonk, van A.C.M.; Zwietering, M.H.; Wells-Bennik, M.H.J.

    2013-01-01

    This challenge study demonstrates that Listeria monocytogenes does not grow in Gouda cheese: during the first 8 weeks of ripening no growth was observed and between 8 and 52 weeks viable numbers declined significantly in a well-established Gouda microcheese system. Cheese milk was artificially conta

  16. Fate of Listeria monocytogenes in Gouda microcheese: No growth, and substantial inactivation after extended ripening times

    NARCIS (Netherlands)

    Wemmenhove, E.; Stampelou, I.; Hooijdonk, van A.C.M.; Zwietering, M.H.; Wells-Bennik, M.H.J.

    2013-01-01

    This challenge study demonstrates that Listeria monocytogenes does not grow in Gouda cheese: during the first 8 weeks of ripening no growth was observed and between 8 and 52 weeks viable numbers declined significantly in a well-established Gouda microcheese system. Cheese milk was artificially

  17. [Listeria monocytogenes in food].

    Science.gov (United States)

    Mícková, V

    1992-12-01

    As in recent years laboratory diagnostics of listeria has become part of food microbiology, the frequency of occurrence of the bacteria Listeria monocytogenes has been followed in various kinds of foods for a year. A total of 51 strains of L. monocytogenes (7.2%) was isolated from 700 kinds of samples (raw milk, pasteurized milk, meat surface, poultry, cheeses, thermally not treated meat products, food--industry machinery). As can be seen in Tab. I, the highest number of strains was isolated from meat surfaces (13.5%), followed by meat--industry machinery (12.72%), poultry (10%) and cheeses (5%). The lower numbers of strains were found out in thermally not treated meat products (3.8%) and in raw milk (3.3%). Pasteurized milk did not contain any strains. Our findings in raw milk (3.3%) and in pasteurized milk (0) are in agreement with the data cited e. g. by authors from the USA (Lovett et al., 1987), who mention the value of 4.2% in raw milk and the zero value in pasteurized milk. The percentage of strains monitored in cheeses (5%) can be evaluated as low as the assortment of investigated cheeses was small (all strains were isolated from soft ripening cheeses). German authors (Tham et al., 1988) speak about the 2.5% percentage of L. monocytogenes strains; this is in keeping with our findings. The findings in thermally not treated meat products (3.8%) can be evaluated as low although the number of strains found in raw meat was high.(ABSTRACT TRUNCATED AT 250 WORDS)

  18. Ecosystem Viable Yields

    CERN Document Server

    De Lara, Michel; Oliveros-Ramos, Ricardo; Tam, Jorge

    2011-01-01

    The World Summit on Sustainable Development (Johannesburg, 2002) encouraged the application of the ecosystem approach by 2010. However, at the same Summit, the signatory States undertook to restore and exploit their stocks at maximum sustainable yield (MSY), a concept and practice without ecosystemic dimension, since MSY is computed species by species, on the basis of a monospecific model. Acknowledging this gap, we propose a definition of "ecosystem viable yields" (EVY) as yields compatible i) with biological viability levels for all time and ii) with an ecosystem dynamics. To the difference of MSY, this notion is not based on equilibrium, but on viability theory, which offers advantages for robustness. For a generic class of multispecies models with harvesting, we provide explicit expressions for the EVY. We apply our approach to the anchovy--hake couple in the Peruvian upwelling ecosystem between the years 1971 and 1981.

  19. The fate of two Listeria monocytogenes serotypes in "cig kofte" at different storage temperatures.

    Science.gov (United States)

    Durmaz, Hisamettin; Sagun, Emrullah; Sancak, Hakan; Sagdic, Osman

    2007-05-01

    Cig kofte is a traditional Turkish food prepared from minced beef, bulgur, onions, garlic and varieties of spices. It is generally consumed within a few hours. However, leftovers can be kept in refrigerator or in room temperature up to 24h until they are consumed. In this study, survival and growth of two Listeria monocytogenes serotypes were investigated in cig kofte during the storage. For this purpose, the prepared samples were separately contaminated with serotypes 1/2b or 4b of L. monocytogenes at the level of 10(4)CFU/g and stored at 4°C and 21°C. L. monocytogenes colonies were counted at the beginning, 3rd, 6th, 12th and 24th hours of the storage. At 4°C, L. monocytogenes 4b significantly increased (P0.05) during the storage period. At 21°C, both L. monocytogenes 1/2b and 4b increased significantly (Pcig kofte did not inhibit the growths of L. monocytogenes serotypes during the storage. These results indicated that L. monocytogenes was able to survive and grow in cig kofte at the both storage temperatures of 4°C and 21°C and cig kofte seemed to be a suitable medium for this pathogen.

  20. Evaluation of Listeria monocytogenes survival in ice cream mixes flavored with herbal tea using Taguchi method.

    Science.gov (United States)

    Ozturk, Ismet; Golec, Adem; Karaman, Safa; Sagdic, Osman; Kayacier, Ahmed

    2010-10-01

    In this study, the effects of the incorporation of some herbal teas at different concentrations into the ice cream mix on the population of Listeria monocytogenes were studied using Taguchi method. The ice cream mix samples flavored with herbal teas were prepared using green tea and sage at different concentrations. Afterward, fresh culture of L. monocytogenes was inoculated into the samples and the L. monocytogenes was counted at different storage periods. Taguchi method was used for experimental design and analysis. In addition, some physicochemical properties of samples were examined. Results suggested that there was some effect, although little, on the population of L. monocytogenes when herbal tea was incorporated into the ice cream mix. Additionally, the use of herbal tea caused a decrease in the pH values of the samples and significant changes in the color values.

  1. Effects of essential oil from mint (Mentha piperita) on Salmonella enteritidis and Listeria monocytogenes in model food systems at 4 degrees and 10 degrees C.

    Science.gov (United States)

    Tassou, C C; Drosinos, E H; Nychas, G J

    1995-06-01

    The effect of mint (Mentha piperita) essential oil (0.5, 1.0, 1.5 and 2.0%, v/w) on Salmonella enteritidis and Listeria monocytogenes in a culture medium and three model foods; tzatziki (pH 4.5), taramosalata (pH 5.0) and pâté (pH 6.8), inoculated at 10(7) cfu g-1, at 4 degrees and 10 degrees C for ca 1 week was studied. In the culture medium supplemented with the essential oil, no growth was observed over 2 d at 30 degrees C determined by a conductance method with a Malthus 2000 growth analyser. Salmonella enteritidis died in tzatziki in all treatments and declined in the other foods except for pâté at 10 degrees C as judged with viable counts. Listeria monocytogenes populations showed a declining trend towards the end of the storage period but was increased in pâté. Mint essential oil antibacterial action depended mainly on its concentration, food pH, composition, storage temperature and the nature of the micro-organism.

  2. The Viable Violinist.

    Science.gov (United States)

    Hawking, Michael

    2016-06-01

    In the aftermath of the Kermit Gosnell trial and Giubilini and Minerva's article 'After-birth abortion', abortion-rights advocates have been pressured to provide an account of the moral difference between abortion, particularly late-term abortion, and infanticide. In response, some scholars have defended a moral distinction by appealing to an argument developed by Judith Jarvis Thomson in A defense of abortion. However, once Thomson's analogy is refined to account for the morally relevant features of late-term pregnancy, rather than distinguishing between late-term abortion and infanticide, it reinforces their moral similarity. This is because late-term abortion requires more than detachment - it requires an act of feticide to ensure the death of the viable fetus. As such, a Thomsonian account cannot be deployed successfully as a response to Giubilini and Minerva. Those wishing to defend late-term abortion while rejecting the permissibility of infanticide will need to provide an alternative account of the difference, or else accept Giubilini and Minerva's conclusion.

  3. Biotic and abiotic soil properties influence survival of Listeria monocytogenes in soil.

    Directory of Open Access Journals (Sweden)

    Aude Locatelli

    Full Text Available Listeria monocytogenes is a food-borne pathogen responsible for the potentially fatal disease listeriosis and terrestrial ecosystems have been hypothesized to be its natural reservoir. Therefore, identifying the key edaphic factors that influence its survival in soil is critical. We measured the survival of L. monocytogenes in a set of 100 soil samples belonging to the French Soil Quality Monitoring Network. This soil collection is meant to be representative of the pedology and land use of the whole French territory. The population of L. monocytogenes in inoculated microcosms was enumerated by plate count after 7, 14 and 84 days of incubation. Analysis of survival profiles showed that L. monocytogenes was able to survive up to 84 days in 71% of the soils tested, in the other soils (29% only a short-term survival (up to 7 to 14 days was observed. Using variance partitioning techniques, we showed that about 65% of the short-term survival ratio of L. monocytogenes in soils was explained by the soil chemical properties, amongst which the basic cation saturation ratio seems to be the main driver. On the other hand, while explaining a lower amount of survival ratio variance (11%, soil texture and especially clay content was the main driver of long-term survival of L. monocytogenes in soils. In order to assess the effect of the endogenous soils microbiota on L. monocytogenes survival, sterilized versus non-sterilized soils microcosms were compared in a subset of 9 soils. We found that the endogenous soil microbiota could limit L. monocytogenes survival especially when soil pH was greater than 7, whereas in acidic soils, survival ratios in sterilized and unsterilized microcosms were not statistically different. These results point out the critical role played by both the endogenous microbiota and the soil physic-chemical properties in determining the survival of L. monocytogenes in soils.

  4. A note on challenge trials to determine the growth of Listeria monocytogenes on mushrooms (Agaricus bisporus

    Directory of Open Access Journals (Sweden)

    Leong Dara

    2015-12-01

    Full Text Available In the EU, food is considered safe with regard to Listeria monocytogenes if the number of micro-organisms does not exceed 100 colony forming units (cfu/g throughout its shelf-life. Therefore, it is important to determine if a food supports growth of L. monocytogenes. Guidelines for conducting challenge tests for growth assessment of L. monocytogenes on foods were published by the European Union Reference Laboratory (EURL in 2014. The aim of this study was to use these guidelines to determine if refrigerated, fresh, whole, closed-cap, prepackaged mushrooms (Agaricus bisporus support the growth of L. monocytogenes. Three batches of mushrooms were artificially inoculated at approximately 100 cfu/g with a three-strain mix of L. monocytogenes and incubated for 2 days at 8°C followed by 4 days at 12°C. L. monocytogenes numbers were determined (in triplicate for each batch on days 0, 2 and 6. Water activity, pH and total bacterial counts were also determined. There was no increase in the number of L. monocytogenes above the threshold of 0.5 log cfu/g in any of the replicates. In 8 of 9 replicates, the numbers decreased indicating that A. bisporus do not support the growth of L. monocytogenes. As the EU regulations allow < 100 cfu/g if the food cannot support growth of L. monocytogenes, the significance of this study is that mushrooms with < 100 cfu/g may be within the regulations and therefore, quantitative rather than qualitative determination may be required.

  5. Efficacy of Acetic Acid against Listeria monocytogenes Attached to Poultry Skin during Refrigerated Storage.

    Science.gov (United States)

    Gonzalez-Fandos, Elena; Herrera, Barbara

    2014-09-11

    This work evaluates the effect of acetic acid dipping on the growth of L. monocytogenes on poultry legs stored at 4 °C for eight days. Fresh inoculated chicken legs were dipped into either a 1% or 2% acetic acid solution (v/v) or distilled water (control). Changes in mesophiles, psychrotrophs, Enterobacteriaceae counts and sensorial characteristics (odor, color, texture and overall appearance) were also evaluated. The shelf life of the samples washed with acetic acid was extended by at least two days over the control samples washed with distilled water. L. monocytogenes counts before decontamination were 5.57 log UFC/g, and after treatment with 2% acetic acid (Day 0), L. monocytogenes counts were 4.47 log UFC/g. Legs washed with 2% acetic acid showed a significant (p acetic acid. This study demonstrates that while acetic acid did reduce populations of L. monocytogenes on meat, it did not completely inactivate the pathogen. The application of acetic acid may be used as an additional hurdle contributing to extend the shelf life of raw poultry and reducing populations of L. monocytogenes.

  6. 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

    2001-05-01

    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.

  7. [Hematometra & Listeria monocytogenes].

    Science.gov (United States)

    Gómez Arzapalo, E; Pérez Mendizábal, A; Herrera Avalos, I; Gorozpe Calvillo, J I

    2001-05-01

    The hematometra is a nosological entity that may not always be attributed to an embryonic defect of the paramesonefros; cervical-vaginal infections such as etiological possibilities due to Listeria monocytogenes (Lm), cervix malignant neoplasias, iatrogenias due to endometrial ablation with Lasser, traumatic bloody uterine curetage and because of cervical cryocoagulation or electrocoagulation are also mentioned. The case to be reported is from a woman in reproductive stage, who is 32 years old, and had menarca at the age of 13, starting her sexual life at 31, not using any method to control her fertility. When having an eight-week amenorrhea after 8 months of marriage, she visited the doctor for assumed pregnancy, within the prenatal analysis a pelvic echographic study was requested, finding out images that we concluded as hematometra, having been drained and demonstrated the presence of LM by anti-Lm antibodies, being administered Azitromicina and Espiramicina.

  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. The quorum sensing luxS gene is induced in Lactobacillus acidophilus NCFM in response to Listeria monocytogenes.

    Science.gov (United States)

    Moslehi-Jenabian, Saloomeh; Vogensen, Finn Kvist; Jespersen, Lene

    2011-10-03

    The luxS gene involved in quorum sensing has been shown to control different behaviour of probiotic lactobacilli. In this study we investigated if luxS in Lactobacillus acidophilus NCFM was up-regulated in response to Listeria monocytogenes EGD-e. The two bacterial strains were grown in mono- and co-culture and the growth of both bacteria and the transcriptional level of luxS in L. acidophilus cells were monitored. Contrary to L. acidophilus, the growth of L. monocytogenes was significantly affected by co-cultivation. Transcriptional analysis showed that the expression of luxS increased during exponential growth in L. acidophilus cells with the highest level in the late-exponential growth phase, decreasing in the stationary phase. Following co-cultivation with L. monocytogenes, the transcriptional level of luxS increased significantly in mid-exponential growing cells of L. acidophilus after incubation with viable L. monocytogenes cells and by addition of cell-free culture supernatant of L. monocytogenes, whereas incubation with heat killed cells of L. monocytogenes had no effect on the transcriptional level. This could indicate that the up-regulation of luxS is due to a response to a secreted compound produced by L. monocytogenes cells.

  10. Counting carbohydrates

    Science.gov (United States)

    Carb counting; Carbohydrate-controlled diet; Diabetic diet; Diabetes-counting carbohydrates ... Many foods contain carbohydrates (carbs), including: Fruit and fruit juice Cereal, bread, pasta, and rice Milk and milk products, soy milk Beans, legumes, ...

  11. Seal Counts

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Database of seal counts from aerial photography. Counts by image, site, species, and date are stored in the database along with information on entanglements and...

  12. Platelet Count

    Science.gov (United States)

    ... their spleen removed surgically Use of birth control pills (oral contraceptives) Some conditions may cause a temporary (transitory) increased ... increased platelet counts include estrogen and birth control pills (oral contraceptives). Mildly decreased platelet counts may be seen in ...

  13. Efficacy of a Sonicating Swab for Removal and Capture of Listeria monocytogenes in Biofilm on Stainless Steel.

    Science.gov (United States)

    Branck, Tobyn A; Hurley, Matthew J; Prata, Gianna N; Crivello, Christina A; Marek, Patrick J

    2017-03-17

    Listeria monocytogenes is of great concern in food processing facilities because it persists in biofilms, potentiating biotransfer. Stainless steel is commonly used for food contact surfaces and transport containers. L. monocytogenes biofilm on stainless steel served as a model system for surface sampling to test the performance of a sonicating swab in comparison to a standard cotton swab. Swab performance and consistency were determined using total viable counts. Stainless steel coupons sampled with both swabs were examined with SEM to visualize biofilms and surface structures (i.e. polishing grooves and scratches). LSCM was used to image and quantitate the percent area of remaining biofilm after sampling with each swab type. The total viable count was significantly higher (P ≤ 0.05) for the sonicating swab in comparison to the standard swab within each trial. The sonicating swab was more consistent in cell recovery than standard swab having lower CVs ranging from 8.9% to 12.3% and 7.1% to 37.6% respectively. SEM imaging showed biofilm remaining in the polished grooves of the coupons sampled with the standard swab but were noticeably absent for the sonicating swab. Percent area measurement of biofilm remaining on stainless steel coupons showed significantly (P ≤ 0.05) less biofilm remained when using the sonicating swab (median 1.1%) in comparison to the standard swab (median 70.4%). The sonicating swab provided a higher recovery of cells with more consistency than the standard swab and is the first swabbing device to employ: sonication, suction, and scrubbing.IMPORTANCE Inadequate surface sampling can result in food borne illness outbreaks from biotransfer since verification of sanitization protocols relies on surface sampling and recovery of microorganisms for detection and enumeration. Swabbing is a standard method for microbiological sampling of surfaces. Although swabbing offers portability and ease of use, there are limitations, such as high user

  14. Formation and resuscitation of viable but nonculturable Salmonella typhi.

    Science.gov (United States)

    Zeng, Bin; Zhao, Guozhong; Cao, Xiaohong; Yang, Zhen; Wang, Chunling; Hou, Lihua

    2013-01-01

    Salmonella typhi is a pathogen that causes the human disease of typhoid fever. The aim of this study was to investigate the viable but nonculturable (VBNC) state of S. typhi. Some samples were stimulated at 4°C or -20°C, while others were induced by different concentrations of CuSO4. Total cell counts remained constant throughout several days by acridine orange direct counting; however, plate counts declined to undetectable levels within 48 hours by plate counting at -20°C. The direct viable counts remained fairly constant at this level by direct viable counting. Carbon and nitrogen materials slowly decreased which indicated that a large population of cells existed in the VBNC state and entered the VBNC state in response to exposure to 0.01 or 0.015 mmol/L CuSO4 for more than 14 or 12 days, respectively. Adding 3% Tween 20 or 1% catalase enabled cells to become culturable again, with resuscitation times of 48 h and 24 h, respectively. The atomic force microscope results showed that cells gradually changed in shape from short rods to coccoids, and decreased in size when they entered the VBNC state. Further animal experiments suggested that resuscitated cells might regain pathogenicity.

  15. Effect of monolaurin and lactic acid on Listeria monocytogenes attached to catfish fillets.

    Science.gov (United States)

    Verhaegh, E G; Marshall, D L; Oh, D H

    1996-04-01

    The purpose of this study was to determine the effects of monolaurin and lactic acid, singly or combined, on Listeria monocytogenes attached to catfish fillets. Skinless catfish fillets were inoculated with L. monocytogenes and dip treated in monolaurin and/or lactic acid solution for various time periods. Results showed that monolaurin up to 400 micrograms/ml had no influence on counts. Conversely, lactic acid-treated fillets had reduced counts compared to controls. Dipping in 0.85, 1.70, or 2.55% lactic acid for 30 min reduced counts by 0.9, 1.4, or 1.3 logs, respectively. Extending the dipping time to 60 min resulted in little additional decrease in counts. Combining monolaurin with lactic acid yielded results similar to lactic acid alone. Hence, population reduction ability resides with lactic acid and not monolaurin.

  16. Cross-contamination between processing equipment and deli meats by Listeria monocytogenes.

    Science.gov (United States)

    Lin, Chia-Min; Takeuchi, Kazue; Zhang, Lei; Dohm, Cynthia B; Meyer, Joseph D; Hall, Paul A; Doyle, Michael P

    2006-01-01

    compared, 12, 8, and 2 L. monocytogenes-positive samples were detected by both the enrichment culture and BAX-PCR, BAX-PCR only, and enrichment culture only assays, respectively. The number of L. monocytogenes-positive samples and L. monocytogenes counts increased during storage of turkey meat but decreased for salami and bologna. Significantly more turkey samples were L. monocytogenes positive when the contents of the entire package were sampled than when 25 g was sampled. Our results indicate that L. monocytogenes can be transferred from a contaminated slicer onto meats and can survive or grow better on uncured oven-roasted turkey than on salami or bologna with preservatives. Higher L. monocytogenes cell numbers inoculated on the slicer blade resulted in more L. monocytogenes-positive sliced meat samples. In addition, the BAX-PCR assay was better than the enrichment culture assay at detecting L. monocytogenes on turkey meat (P < 0.05).

  17. EFSA Panel on Biological Hazards (BIOHAZ); Scientific Opinion on the evaluation of the safety and efficacy of ListexTM P100 for the removal of Listeria monocytogenes surface contamination of raw fish

    DEFF Research Database (Denmark)

    Hald, Tine

    in reducing L. monocytogenes counts on raw fish nor on its impact on L. monocytogenes contamination levels in finished product. It was not possible to estimate the potential listeriosis risk reduction by treating raw fish with Listex™ P100. The data were not adequate to allow firm conclusions on persistence...

  18. Removal of Listeria monocytogenes dual-species biofilms using combined enzyme-benzalkonium chloride treatments.

    Science.gov (United States)

    Rodríguez-López, Pedro; Carballo-Justo, Alba; Draper, Lorraine A; Cabo, Marta L

    2017-01-01

    The effects of pronase (PRN), cellulase (CEL) or DNaseI alone or combined with benzalkonium chloride (BAC) against Listeria monocytogenes-carrying biofilms were assayed. The best removal activity against L. monocytogenes-Escherichia coli biofilms was obtained using DNaseI followed by PRN and CEL. Subsequently, a modified logistic model was used to quantify the combined effects of PRN or DNaseI with BAC. A better BAC performance after PRN compared to DNaseI eradicating L. monocytogenes was observed. In E. coli the effects were the opposite. Finally, effects of DNaseI and DNaseI-BAC treatments were compared against two different L. monocytogenes-carrying biofilms. DNaseI-BAC was more effective against L. monocytogenes when co-cultured with E. coli. Nonetheless, comparing the removal effects after BAC addition, these were higher in mixed-biofilms with Pseudomonas fluorescens. However, a high number of released viable cells was observed after combined treatments. These results open new perspectives of enzymes as an anti-biofilm strategy for environmental pathogen control.

  19. Acidified sodium chlorite treatment for inhibition of Listeria monocytogenes growth on the surface of cooked roast beef.

    Science.gov (United States)

    Beverly, Richelle L; Janes, Marlene E; Oliver, Grady

    2006-02-01

    The effects of acidified sodium chlorite (ASC) against Listeria monocytogenes on the surface of cooked roast beef were investigated. L. monocytogenes, strain V7, serotype 1/2a, was inoculated at numbers of 6.0 log CFU/g onto 5-g cubes of cooked regular or spicy roast beef. The samples were allowed to air dry for 1 h. The cooked roast beef samples were dipped into ASC or sprayed with ASC solutions of 250, 500, 750, or 1,000 ppm, then placed in bags with or without a vacuum and refrigerated at 4 degrees C. L. monocytogenes counts were determined after 0, 7, 14, 21, and 28 days of storage by spread plating roast beef samples onto Oxford agar plates that were incubated at 37 degrees C for 48 h. At day 28, the number of L. monocytogenes on the > or = 500 ppm ASC-treated spicy roast beef samples had count reductions that were >4.0 log CFU/g, whereas the same concentrations of ASC-treated regular roast beef samples had approximately a 2.5 log CFU/g reduction in L. monocytogenes counts when compared with the untreated samples. No significant differences (P > 0.05) were observed in L. monocytogenes counts between the vacuum- or nonvacuum-packaged ASC-treated cooked roast beef samples. Sensory evaluation showed no significant differences (P > 0.05) between ASC-treated and untreated roast beef. ASC can be used as a processing aid in the form of a dip or spray treatment to control L. monocytogenes on the surface of cooked roast beef.

  20. Neuroinfections due to Listeria monocytogenes.

    Science.gov (United States)

    Streharova, A; Babjakova, A; Moravcikova, A; Harnicarova, A; Holeckova, K; Lesnakova, A; Sladeckova, V; Seckova, S; Kisac, P; Beno, P

    2007-11-01

    Listeria monocytogenes is not a rare pathogen causing meningitis, mainly in small children and in close contacts to livestock. The pathogen is naturally resistant to cephalosporins and some glycopeptides as well, therefore despite of syndromologic diagnosis of meningitis and initial therapy with 3rd generation cephalosporins according to the guidelines therapeutic failures with clinical consequences may occur.

  1. Rapid quantitative detection of, Listeria monocytogenes in salmon products: evaluation of pre-real-time PCR strategies.

    Science.gov (United States)

    Rodríguez-Lázaro, David; Jofré, Anna; Aymerich, Teresa; Garriga, Margarita; Pla, Maria

    2005-07-01

    The spread and persistence of Listeria monocytogenes in smoked fish products and seafood processing factories are big concerns. Thus, the corresponding quality assurance programs must include adequate microbiological control measures. We evaluated eight different pre-PCR sample processing strategies to be coupled with a previously developed real-time PCR assay for the quantitative detection of L. monocytogenes in salmon products. The optimal pre-PCR procedure involved filtration and DNA purification with the use of a commercial kit. This strategy could detect 10 CFU of L. monocytogenes per g of smoked salmon and could quantify 1,000 CFU/g with excellent accuracy compared with the standard plate count method. Thus, this method could be a promising alternative for the quantitative detection of L. monocytogenes in smoked fish products and processing factories. This method could also detect the bacterium in raw salmon.

  2. 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.

  3. Reducing levels of Listeria monocytogenes contamination on raw salmon with acidified sodium chlorite.

    Science.gov (United States)

    Su, Yi-Cheng; Morrissey, Michael T

    2003-05-01

    The antimicrobial activity of acidified sodium chlorite (ASC) against Listeria monocytogenes in salmon was studied. Raw salmon (whole fish and fillets) inoculated with L. monocytogenes (10(3) CFU/cm2 or 10(4) CFU/g) were washed with ASC solution (50 ppm) for 1 min and stored at -18 degrees C for 1 month (whole salmon) or in ice for 7 days (fillets). L. monocytogenes populations were determined for whole salmon after frozen storage and for fillets on days 1, 3, 5, and 7 of storage. A wash with ASC solution followed by ASC glazing did not reduce L. monocytogenes on the skin of whole salmon during frozen storage. However, the wash resulted in an L. monocytogenes reduction of 0.5 log CFU/g for salmon fillets. The populations of L. monocytogenes in fillets increased slowly during ice storage, but the growth of these populations was retarded by ASC ice. By day 7, the populations were 0.25 log units smaller in fillets stored in ASC ice and 0.62 log units smaller in fillets that had been washed with ASC solution and stored in ASC ice than in control fillets. Treatment with ASC also reduced total plate counts (TPCs) by 0.43 log CFU/cm2 on the skin of whole salmon and by 0.31 log CFU/g in fillets. The TPCs for skin decreased during frozen storage but increased gradually for fillets stored at 5 degrees C or in ice. However, TPCs of ASC-treated samples were lower than those for controls at any point during the study. Washing with ASC solution significantly (P < 0.05) reduced TPCs on the skin of whole salmon and in fillets, as well as L. monocytogenes in fillets. The antimicrobial activity of ASC was enhanced when salmon was washed with ASC solution and stored in ASC ice.

  4. 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.

  5. Rapid detection of Listeria monocytogenes by real-time PCR in processed meat and dairy products.

    Science.gov (United States)

    Heo, Eun Jeong; Song, Bo Ra; Park, Hyun Jung; Kim, Young Jo; Moon, Jin San; Wee, Sung Hwan; Kim, Jin-Seok; Yoon, Yohan

    2014-03-01

    The objectives of this study were to evaluate the detection of Listeria monocytogenes in different ready-to-eat foods using real-time PCR (RT-PCR). Various concentrations (10(0) to 10(5) CFU/ml) of L. monocytogenes ATCC 19115 were inoculated into ham, sausage, ground meat, processed milk, cheese, and infant formula. L. monocytogenes ATCC 19115 in the samples was then enumerated on Oxford agar, and DNA was extracted from the samples before and after incubation at 36°C for 4 h. A set of primers and hybridization probe designed in this study was then used to detect the pathogen. The standard curve was then prepared by plotting cycle threshold values for each dilution versus L. monocytogenes cell counts (log CFU). The specificity of the set of primers and hybridization probe was appropriate. A 4-h incubation at 36°C before DNA extraction produced optimum standard curves in comparison to the results for a 0-h incubation. Thus, a 4-h incubation at 36°C was applied for monitoring L. monocytogenes in collected food samples. To monitor L. monocytogenes in foods, 533 samples (ham, 129; sausage, 226; ground meat, 72; processed cheese, 54; processed milk, 42; and infant formula, 10) were collected from retail markets and from the step before pasteurization in plants. Of all 533 samples, 4 samples (0.8%) showed positive signals in RT-PCR. Two samples from hams (1.6%) and two samples from sausages (0.9%) were determined to be positive for L. monocytogenes at processed meat and milk products.

  6. Control of Listeria monocytogenes in fresh cheese using protective lactic acid bacteria.

    Science.gov (United States)

    Coelho, M C; Silva, C C G; Ribeiro, S C; Dapkevicius, M L N E; Rosa, H J D

    2014-11-17

    In the past years, there has been a particular focus on the application of bacteriocins produced by lactic acid bacteria (LAB) in controlling the growth of pathogenic bacteria in foods. The aim of this study was to select LAB strains with antimicrobial activity, previously isolated from a traditional Azorean artisanal cheese (Pico cheese), in order to identify those with the greatest potential in reducing Listeria monocytogenes in fresh cheese. Eight bacteriocin producer strains identified as Lactococcus lactis (1) and Enterococcus faecalis (7) were tested. In general, the bacteriocin-producing strains presented a moderate growth in fresh cheese at refrigeration temperatures (4 °C), increasing one log count in three days. They exhibited slow acidification capacity, despite the increased production of lactic acid displayed by some strains after 24h. Bacteriocin activity was only detected in the whey of fresh cheese inoculated with two Enterococcus strains, but all cheeses made with bacteriocin-producing strains inhibited L. monocytogenes growth in the agar diffusion bioassay. No significant differences were found in overall sensory evaluation made by a non-trained panel of 50-52 tasters using the isolates as adjunct culture in fresh cheese, with the exception of one Enterococcus strain. To test the effect of in situ bacteriocin production against L. monocytogenes, fresh cheese was made from pasteurized cows' milk inoculated with bacteriocin-producing LAB and artificially contaminated with approximately 10(6) CFU/mL of L. monocytogenes. The numbers of L. monocytogenes were monitored during storage of fresh cheese at refrigeration temperature (4 °C) for up to 15 days. All strains controlled the growth of L. monocytogenes, although some Enterococcus were more effective in reducing the pathogen counts. After 7 days, this reduction was of approximately 4 log units compared to the positive control. In comparison, an increase of 4 log CFU/mL in pathogen numbers was

  7. Fat content increases the lethality of ultra-high-pressure homogenization on Listeria monocytogenes in milk.

    Science.gov (United States)

    Roig-Sagués, A X; Velázquez, R M; Montealegre-Agramont, P; López-Pedemonte, T J; Briñez-Zambrano, W J; Guamis-López, B; Hernandez-Herrero, M M

    2009-11-01

    Listeria monocytogenes CCUG 15526 was inoculated at a concentration of approximately 7.0 log(10) cfu/mL in milk samples with 0.3, 3.6, 10, and 15% fat contents. Milk samples with 0.3 and 3.6% fat content were also inoculated with a lower load of approximately 3.0 log(10) cfu/mL. Inoculated milk samples were subjected to a single cycle of ultra-high-pressure homogenization (UHPH) treatment at 200, 300, and 400 MPa. Microbiological analyses were performed 2 h after the UHPH treatments and after 5, 8, and 15 d of storage at 4 degrees C. Maximum lethality values were observed in samples treated at 400 MPa with 15 and 10% fat (7.95 and 7.46 log(10) cfu/mL), respectively. However, in skimmed and 3.6% fat milk samples, complete inactivation was not achieved and, during the subsequent 15 d of storage at 4 degrees C, L. monocytogenes was able to recover and replicate until achieving initial counts. In milk samples with 10 and 15% fat, L. monocytogenes recovered to the level of initial counts only in the milk samples treated at 200 MPa but not in the milk samples treated at 300 and 400 MPa. When the load of L. monocytogenes was approximately 3.0 log(10) cfu/mL in milk samples with 0.3 and 3.6% fat, complete inactivation was not achieved and L. monocytogenes was able to recover and grow during the subsequent cold storage. Fat content increased the maximum temperature reached during UHPH treatment; this could have contributed to the lethal effect achieved, but the amount of fat of the milk had a stronger effect than the temperature on obtaining a higher death rate of L. monocytogenes.

  8. Multiplicity Counting

    Energy Technology Data Exchange (ETDEWEB)

    Geist, William H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-12-01

    This set of slides begins by giving background and a review of neutron counting; three attributes of a verification item are discussed: 240Pueff mass; α, the ratio of (α,n) neutrons to spontaneous fission neutrons; and leakage multiplication. It then takes up neutron detector systems – theory & concepts (coincidence counting, moderation, die-away time); detector systems – some important details (deadtime, corrections); introduction to multiplicity counting; multiplicity electronics and example distributions; singles, doubles, and triples from measured multiplicity distributions; and the point model: multiplicity mathematics.

  9. 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.

  10. Detection of Listeria monocytogenes by direct colony hybridization on hydrophobic grid-membrane filters by using a chromogen-labeled DNA probe.

    Science.gov (United States)

    Peterkin, P I; Idziak, E S; Sharpe, A N

    1991-02-01

    A DNA probe specific for Listeria monocytogenes was isolated from a beta-hemolytic recombinant clone of an L. monocytogenes gene bank. It was labeled with horseradish peroxidase and used in a direct colony hybridization method on hydrophobic grid-membrane filters for the detection of the organism. Following color development of the chromogen, a commercial counter (HGMF Interpreter) was able to detect and count the organisms electronically. The method gave a positive reaction with 70 L. monocytogenes strains, while showing a negative reaction with 10 strains of other Listeria spp. and with 20 organisms of other genera.

  11. Loss of viability of Listeria monocytogenes in contaminated processed cheese during storage at 4, 12 and 22 degrees C.

    Science.gov (United States)

    Angelidis, Apostolos S; Boutsiouki, Paraskevi; Papageorgiou, Demetrios K

    2010-09-01

    The behaviour of Listeria monocytogenes in a processed cheese product was evaluated over time by inoculating the product with three different L. monocytogenes strains (Scott A, CA and a strain isolated from processed cheese) at three different inoculation levels (ca. 6x10(5), ca. 6x10(3) and 10(2)CFU/g of cheese or less) and after storage of the contaminated products at 4, 12 or 22 degrees C. Growth of L. monocytogenes was not observed in any of the experimental trials (experiments involving different combinations of strain, inoculum level and storage temperature) throughout the storage period. L. monocytogenes populations decreased over time with a rate that was strain- and storage temperature-dependent. Nonetheless, for cheeses that had been inoculated with the higher inoculum and stored at 4 degrees C viable populations of L. monocytogenes could be detected for up to nine months post-inoculation. The L. monocytogenes survival curves obtained from the different trials were characterised by a post-inoculation phase during which the populations remained essentially unchanged (lag phase) followed by a phase of logarithmic decline. The duration of the lag phase and the rate of inactivation of L. monocytogenes in the different trials were estimated based on data from the linear descending portions of the survival curves. In addition, a non-linear Weibull-type equation was fitted to the data from each survival curve with satisfactory results. The results of the present study emphasize that, according to the definition laid down in the European Union Regulation 1441/2007, the processed cheese product tested in this work should be considered and classified as one that does not support the growth of L. monocytogenes under reasonable foreseeable conditions of distribution and storage. However, post-processing contamination of the product should be austerely avoided as the pathogen can survive in the product for extended periods of time, particularly under refrigerated

  12. Reticulocyte count

    Science.gov (United States)

    ... radiation therapy, or infection) Cirrhosis of the liver Anemia caused by low iron levels, or low levels of vitamin B12 or folate Chronic kidney disease Reticulocyte count may be higher during pregnancy.

  13. 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...

  14. 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...

  15. 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 Listeria sp. and L. monocytogenes were isolated from cooked dumplings with fruits (strawberries or blueberries).

  16. Antimicrobial Tolerance in Listeria monocytogenes

    DEFF Research Database (Denmark)

    Curtis, Thomas Darwin

    There are two ways in which bacteria survive killing by antibiotics. The most well-known, is antibiotic resistance, which results from the acquisition of a resistance gene or mutation that allows bacteria to grow and divide in the presence of antibiotic concentrations that would normally kill other...... that are completely refractory to antibiotics due to the inactivity of cellular processes. Persister cells have been linked to treatment failures in several bacterial infections including Mycobacterium tuberculosis, Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli. Preceding the start of this Ph......D project, Listeria monocytogenes was observed to form these antibiotic tolerant persister cells. L. monocytogenes is a Gram-positive, foodborne pathogen that causes listeriosis, a rare, but often lethal disease, even with antibiotic treatment. It typically affects pregnant women, neonates, the elderly...

  17. A Viable Systems Engineering Approach

    Science.gov (United States)

    2010-04-01

    methodology was not meeting the needs of the sponsors • The Agile approach Scrum was selected as the only viable solution for managing project...Self-organized teams Slide 11 Source: Agile Alliance (http://www.agilealliance.org/) Scrum Applied to Systems Engineering • Scrum is a framework for...ceremonies • A Scrum project is a series of iterations or Sprints where every 2-4 weeks produces fully developed requirements, functional analyses, and

  18. Selection of fluorescent probes for flow cytometric viability assessment of Listeria monocytogenes exposed to membrane-active and oxidizing disinfectants

    NARCIS (Netherlands)

    Luppens, S.B.I.; Barbaras, B.; Breeuwer, P.; Rombouts, F.M.; Abee, T.

    2003-01-01

    The aim of this study was to select fluorescence methods for use as alternatives to plate counting to assess the viability of Listeria monocytogenes cells exposed to benzalkonium chloride (BAC) and hydrogen peroxide, two disinfectants with different mechanisms of action. A further aim of this study

  19. Understanding Blood Counts

    Science.gov (United States)

    ... Lab and Imaging Tests Understanding Blood Counts Understanding Blood Counts Understanding Blood Counts SHARE: Print Glossary Blood cell counts give ... your blood that's occupied by red cells. Normal Blood Counts Normal blood counts fall within a range ...

  20. White Blood Cell Count

    Science.gov (United States)

    ... limited. Home Visit Global Sites Search Help? White Blood Cell Count Share this page: Was this page helpful? ... Count; Leukocyte Count; White Count Formal name: White Blood Cell Count Related tests: Complete Blood Count , Blood Smear , ...

  1. 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.

  2. Counting Penguins.

    Science.gov (United States)

    Perry, Mike; Kader, Gary

    1998-01-01

    Presents an activity on the simplification of penguin counting by employing the basic ideas and principles of sampling to teach students to understand and recognize its role in statistical claims. Emphasizes estimation, data analysis and interpretation, and central limit theorem. Includes a list of items for classroom discussion. (ASK)

  3. Counting Populations

    Science.gov (United States)

    Damonte, Kathleen

    2004-01-01

    Scientists use sampling to get an estimate of things they cannot easily count. A population is made up of all the organisms of one species living together in one place at the same time. All of the people living together in one town are considered a population. All of the grasshoppers living in a field are a population. Scientists keep track of the…

  4. 21 CFR 1210.16 - Method of bacterial count.

    Science.gov (United States)

    2010-04-01

    ... FEDERAL IMPORT MILK ACT Inspection and Testing § 1210.16 Method of bacterial count. The bacterial count of milk and cream refers to the number of viable bacteria as determined by the standard plate method of... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Method of bacterial count. 1210.16 Section...

  5. Listeria monocytogenes en comidas preparadas

    OpenAIRE

    Vila Brugalla, Montserrat

    2013-01-01

    Tradicionalmente Listeria monocytogenes no era considerado como un importante patógeno transmitido a través de los alimentos y, en consecuencia, no había recibido mucha atención por parte de la industria alimentaria. Los índices de listeriosis en la población humana siempre habían estado enormemente ensombrecidos por otras enfermedades transmitidas por los alimentos como la salmonelosis o la campilobacterosis, y la confirmación de brotes era poco frecuente. Sin embargo, los brotes de listerio...

  6. 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.

  7. Use of antimicrobial biodegradable packaging to control Listeria monocytogenes during storage of cooked ham.

    Science.gov (United States)

    Marcos, Begonya; Aymerich, Teresa; Monfort, Josep M; Garriga, Margarita

    2007-11-30

    The antimicrobial effect against L. monocytogenes of biodegradable films (alginate, zein and polyvinyl alcohol) containing enterocins was investigated. Survival of the pathogen was studied by means of challenge tests performed at 6 degrees C during 8 and 29 days, for air-packed and vacuum-packed sliced cooked ham, respectively. Air packaging was tested with two concentrations of enterocins (200 and 2000 AU/cm2). Control air-packed cooked ham showed an increase of L. monocytogenes from 10(4) to 10(7) CFU/g after 8 days. By contrast, packaging with antimicrobial films effectively slowed down the pathogen's growth, leading to final counts lower than in control lots. Air-packaging with alginate films containing 2000 AU/cm2 of enterocins effectively controlled L. monocytogenes for 8 days. An increase of only 1 log unit was observed in zein and polyvinyl alcohol lots at the same enterocin concentration. Vacuum packaging with films containing enterocins (2000 AU/cm2) also delayed the growth of the pathogen. No increase from inoculated levels was observed during 15 days in antimicrobial alginate films. After 29 days of storage, the lowest counts were obtained in samples packed with zein and alginate films containing enterocins, as well as with zein control films. The most effective treatment for controlling L. monocytogenes during 6 degrees C storage was vacuum-packaging of sliced cooked ham with alginate films containing 2000 AU/cm2 of enterocins. From the results obtained it can concluded that antimicrobial packaging can improve the safety of sliced cooked ham by delaying and reducing the growth of L. monocytogenes.

  8. Hygiene and Safety in the Meat Processing Environment from Butcher Shops: Microbiological Contamination and Listeria monocytogenes.

    Science.gov (United States)

    Silva, Danilo Augusto Lopes da; Dias, Mariane Rezende; Cossi, Marcus Vinícius Coutinho; Castilho, Natália Parma Augusto de; Camargo, Anderson Carlos; Nero, Lúis Augusto

    2016-04-01

    The quality and safety of meat products can be estimated by assessing their contamination by hygiene indicator microorganisms and some foodborne pathogens, with Listeria monocytogenes as a major concern. To identify the main sources of microbiological contamination in the processing environment of three butcher shops, surface samples were obtained from the hands of employees, tables, knives, inside butcher displays, grinders, and meat tenderizers (24 samples per point). All samples were subjected to enumeration of hygiene indicator microorganisms and detection of L. monocytogenes, and the obtained isolates were characterized by their serogroups and virulence genes. The results demonstrated the absence of relevant differences in the levels of microbiological contamination among butcher shops; samples with counts higher than reference values indicated inefficiency in adopted hygiene procedures. A total of 87 samples were positive for Listeria spp. (60.4%): 22 from tables, 20 from grinders, 16 from knives, 13 from hands, 9 from meat tenderizers, and 7 from butcher shop displays. Thirty-one samples (21.5%) were positive for L. monocytogenes, indicating the presence of the pathogen in meat processing environments. Seventy-four L. monocytogenes isolates were identified, with 52 from serogroups 1/2c or 3c and 22 from serogroups 4b, 4d, 4a, or 4c. All 74 isolates were positive for hlyA, iap, plcA, actA, and internalins (inlA, inlB, inlC, and inlJ). The establishment of appropriate procedures to reduce microbial counts and control the spread of L. monocytogenes in the final steps of the meat production chain is of utmost importance, with obvious effects on the quality and safety of meat products for human consumption.

  9. Listeriaphages and coagulin C23 act synergistically to kill Listeria monocytogenes in milk under refrigeration conditions.

    Science.gov (United States)

    Rodríguez-Rubio, Lorena; García, Pilar; Rodríguez, Ana; Billington, Craig; Hudson, J Andrew; Martínez, Beatriz

    2015-07-16

    Bacteriophages and bacteriocins are promising biocontrol tools in food. In this work, two Listeria bacteriophages, FWLLm1 and FWLLm3, were assessed in combination with the bacteriocin coagulin C23 to inhibit Listeria monocytogenes. Preliminary results under laboratory conditions demonstrated that both antimicrobials act synergistically when they were applied in suboptimal concentrations. The combined approach was further assessed in milk contaminated with 5×10(4) CFU/ml L. monocytogenes 2000/47 and stored at 4 °C for 10 days. When used alone, phage FWLLm1 added at 5×10(6) PFU/ml, FWLLm3 at 5×10(5) PFU/ml and coagulin C23 at 584 AU/ml kept L. monocytogenes 2000/47 counts lower than the untreated control throughout storage. However, when used in combination, inhibition was enhanced and in the presence of FWLLm1 and coagulin C23, L. monocytogenes 2000/47 counts were under the detection limits (less than 10 CFU/ml) from day 4 until the end of the experiment. Resistant mutants towards phages and coagulin C23 could be obtained, but cross-resistance was not detected. Mutants resistant to FWLLm3 and coagulin C23 were also recovered from surviving colonies after cold storage in milk which may explain the failure of this combination to inhibit L. monocytogenes. Remarkably, the fraction of resistant mutants isolated from the combined treatment was lower than that from each antimicrobial alone, suggesting that synergy between bacteriocins and phages could be due to a lower rate of resistance development and the absence of cross-resistance. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Point of care nucleic acid detection of viable pathogenic bacteria with isothermal RNA amplification based paper biosensor

    Science.gov (United States)

    Liu, Hongxing; Xing, Da; Zhou, Xiaoming

    2014-09-01

    Food-borne pathogens such as Listeria monocytogenes have been recognized as a major cause of human infections worldwide, leading to substantial health problems. Food-borne pathogen identification needs to be simpler, cheaper and more reliable than the current traditional methods. Here, we have constructed a low-cost paper biosensor for the detection of viable pathogenic bacteria with the naked eye. In this study, an effective isothermal amplification method was used to amplify the hlyA mRNA gene, a specific RNA marker in Listeria monocytogenes. The amplification products were applied to the paper biosensor to perform a visual test, in which endpoint detection was performed using sandwich hybridization assays. When the RNA products migrated along the paper biosensor by capillary action, the gold nanoparticles accumulated at the designated Test line and Control line. Under optimized experimental conditions, as little as 0.5 pg/μL genomic RNA from Listeria monocytogenes could be detected. The whole assay process, including RNA extraction, amplification, and visualization, can be completed within several hours. The developed method is suitable for point-of-care applications to detect food-borne pathogens, as it can effectively overcome the false-positive results caused by amplifying nonviable Listeria monocytogenes.

  11. Growth Potential of Listeria Monocytogenes in Sliced Turkey Bresaola Packed in Modified Atmosphere

    Science.gov (United States)

    Cosciani-Cunico, Elena; D’Amico, Stefano; Sfameni, Chiara; Bertasi, Barbara; Losio, Marina N.; Serraino, Andrea; Daminelli, Paolo

    2014-01-01

    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. PMID:27800323

  12. Counting Possibilia

    Directory of Open Access Journals (Sweden)

    Alfredo Tomasetta

    2010-06-01

    Full Text Available Timothy Williamson supports the thesis that every possible entity necessarily exists and so he needs to explain how a possible son of Wittgenstein’s, for example, exists in our world:he exists as a merely possible object (MPO, a pure locus of potential. Williamson presents a short argument for the existence of MPOs: how many knives can be made by fitting together two blades and two handles? Four: at the most two are concrete objects, the others being merely possible knives and merely possible objects. This paper defends the idea that one can avoid reference and ontological commitment to MPOs. My proposal is that MPOs can be dispensed with by using the notion of rules of knife-making. I first present a solution according to which we count lists of instructions - selected by the rules - describing physical combinations between components. This account, however, has its own difficulties and I eventually suggest that one can find a way out by admitting possible worlds, entities which are more commonly accepted - at least by philosophers - than MPOs. I maintain that, in answering Williamson’s questions, we count classes of physically possible worlds in which the same instance of a general rule is applied.

  13. Antibiotic therapy for Listeria monocytogenes bacteremia.

    Science.gov (United States)

    Hung, C C; Chang, S C; Chen, Y C; Hsieh, W C; Luh, K T

    1995-01-01

    Listeria monocytogenes has been recognized as an important pathogen in immunocompromised patients, but it has been rarely reported in Taiwan. We reviewed 13 cases of L. monocytogenes bacteremia at National Taiwan University Hospital over a 12-year period. All of the patients had underlying diseases. Fever was the most common presenting symptom, and neurologic signs were found in 6 patients. Most of the patients received penicillin G, ampicillin or piperacillin with an aminoglycoside. Corticosteroids were used in 9 of 13 patients. The overall mortality directly due to L. monocytogenes bacteremia was 31%. However, patients treated with cephalosporins or oxacillin had higher mortality than those treated with penicillin G, ampicillin or piperacillin (p = 0.05). Given the increasing number of immunosuppressed patients in Taiwan, it is likely that more cases will be encountered. Physicians in Taiwan should be aware of L. monocytogenes bacteremia and its treatment.

  14. Further Evidence of How Unbuffered Starvation at 4°C Influences Listeria monocytogenes EGD-e, HCC23, F2365, and Scott A.

    Science.gov (United States)

    Jarvis, Nathan A; O'Bryan, Corliss A; Martin, Elizabeth M; Ricke, Steven C; Johnson, Michael G; Crandall, Philip G

    2017-10-01

    The soilborne pathogen Listeria monocytogenes frequently contaminates food products and food processing environments and is able to survive desiccation, high osmotic pressures, and starvation. However, little is known about how this pathogen survives starvation at 4°C. This study provides evidence that L. monocytogenes is able to survive total nutrient starvation for 4 weeks. L. monocytogenes strains EGD-e, Scott A, F2365, and HCC23 were starved individually in sterile water. Colony counts declined over 4 weeks, with Scott A declining the most rapidly. Transmission electron microscopy images revealed degradation of starving cell membranes and altered cytosols. Starving cells were subjected to the metabolic inhibitors fluoride, arsenite, 2,4-dinitrophenol, iodoacetate, and cyanide individually. Iodoacetate, which inhibits glyceraldehyde-3-phosphate dehydrogenase, completely reduced cultivable counts below the level of detection compared with the control starving cells; 2,4-dinitrophenol, which dissipates proton motive force, almost completely reduced cultivable counts. These results suggest that L. monocytogenes strains EGD-e, Scott A, F2365, and HCC23 are actively using part of the glycolysis pathway while starving. These results suggest that starving L. monocytogenes cells retain aspects of active metabolism.

  15. Prevalence of Listeria monocytogenes in European cheeses

    DEFF Research Database (Denmark)

    Martinez Rios, Veronica; Dalgaard, Paw

    2017-01-01

    Both in Europe and worldwide cheese has caused important outbreaks of listeriosis and can be a vehicle for transmission of Listeria monocytogenes to consumers. A systematic review and meta-analysis were conducted using scientific literature and European Food Safety Authority (EFSA) reports...... understanding of L. monocytogenes prevalence in different types of cheeses and provided results that can be useful as input for quantitative microbiological risk assessment modelling....

  16. Internalization of Listeria monocytogenes in Whole Avocado.

    Science.gov (United States)

    Chen, Yi; Evans, Peter; Hammack, Thomas S; Brown, Eric W; Macarisin, Dumitru

    2016-08-01

    In recent years, tree fruits have emerged as a new concern for Listeria monocytogenes contamination. The objective of the current study was to evaluate the potential internalization of L. monocytogenes from the surface of avocados into the edible portions of the fruit during certain postharvest practices simulated in a laboratory setting. One set of intact avocados was spot inoculated with L. monocytogenes on the stem scar, and the second set was hydrocooled in water contaminated with L. monocytogenes. Under these experimental conditions, L. monocytogenes internalized into the avocado pulp through the stem or stem scar after both spot inoculation and hydrocooling. In avocados spot inoculated with 50, 130, 500, and 1,300 CFU per fruit, bacteria were detected in the edible portion adjacent to the stem scar within 15 days postinoculation during storage at 4°C. In avocados hydrocooled in water containing L. monocytogenes at 10(6) and 10(8) CFU/ml, bacteria reached the bottom end of the fruit, and the populations in the edible portion adjacent to the stem scar reached up to 5.90 to 7.19 log CFU/g within 10 to 15 days during storage at 4°C. Dye mixed with inoculum was useful for guiding subsequent sampling, but dye penetration patterns were not always consistent with bacterial penetration.

  17. [Analysis of the microbiological quality and potential presence of Listeria monocytogenes in custard apple (Annona muricata), mango (Mangifera indica) and passion fruit (Passiflora edulis) pulps from Costa Rica].

    Science.gov (United States)

    von Breymann, Juliana; Chaves, Carolina; Arias, María Laura

    2013-03-01

    The objective of this work was to determine some of the indicators associated to shelf life, hygiene, process and storage conditions for some of custard apple, mango and passion fruit pulps distributed by the main supermarket chains of the Metropolitan Area of San José, Costa Rica, as well as to examine the potential presence of Listeria monocytogenes in them. Sixty fruit pulp samples were analyzed. Tests included pH determination, total aerobic plate count, yeasts and mold count, lactic bacteria count, total and fecal most probable number and the presence/absence of Listeria monocytogenes in 25 g of the product. Fruit pulp's pH ranged between 3,1 and 3,9, and the microbiological counts obtained were relatively low except for one industry. None of the samples analyzed presented total or fecal coliforms. The presence of Listeria monocytogenes was confirmed in three samples, all of them coming from industry C. Low microbiological counts obtained may be due to the addition of preserving substances and to the pasteurization of some of the products; lack of these two elements may allow the presence of dangerous bacteria such as Listeria monocytogenes.

  18. Viable Syntax: Rethinking Minimalist Architecture

    Directory of Open Access Journals (Sweden)

    Ken Safir

    2010-03-01

    Full Text Available Hauser et al. (2002 suggest that the human language faculty emerged as a genetic innovation in the form of what is called here a ‘keystone factor’—a single, simple, formal mental capability that, interacting with the pre-existing faculties of hominid ancestors, caused a cascade of effects resulting in the language faculty in modern humans. They take Merge to be the keystone factor, but instead it is posited here that Merge is the pre-existing mechanism of thought made viable by a principle that permits relations interpretable at the interfaces to be mapped onto c-command. The simplified minimalist architecture proposed here respects the keystone factor as closely as possible, but is justified on the basis of linguistic analyses it makes available, including a relativized intervention theory applicable across Case, scope, agreement, selection and linearization, a derivation of the A/A’-distinction from Case theory, and predictions such as why in situ wh-interpretation is island-insensitive, but susceptible to intervention effects.

  19. Physiological damages of Listeria monocytogenes treated by high hydrostatic pressure.

    Science.gov (United States)

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

    2002-11-15

    High hydrostatic pressure is a new food preservation technology known for its capacity to inactivate spoilage and pathogenic microorganisms. This study investigated the damages 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 (SEM) revealed that cellular morphology was not really affected. Measuring propidium iodide (PI) staining followed by flow cytometry demonstrated that membrane integrity was damaged in a small part of the population, although the membrane potential evaluated by oxonol fluorescence or measured by analytical methods was reduced from - 86 to - 5 mV. These results for the first time showed that such combined methods as fluorescent dyes monitored by flow cytometry and physiological activity measurements provide valuable indications on cellular viability.

  20. 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.

    upon inocu- lation and again on day 1, 2, 3, 5, 7, 10, 15, 21, 31, 45 and 62. Additional volumes of samples were removed for determin- ation of plate counts by a membrane filtration method, in which cells from 5 ml or 10 ml volumes were collected... on membrane filters, which were placed on agar plates to assay for low counts of culturable cells that might occur. Also, samples were drawn on day 81 to determine direct viable counts (DVC), and nucleoid-containing cell counts (NUCC), and culturable cells...

  1. 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.

  2. 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.

  3. 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

  4. A THUMBNAIL HISTORY OF HETEROTROPHIC PLATE COUNT (HPC) METHODOLOGY IN THE UNITED STATES

    Science.gov (United States)

    Over the past 100 years, the method of determining the number of bacteria in water, foods or other materials has been termed variously as: bacterial plate count, total plate count, total viable plate count, aerobic plate count, standard plate cound and more recently, heterotrophi...

  5. Effects of CO2 on the resuscitation of Listeria monocytogenes injured by various bactericidal treatments.

    Science.gov (United States)

    Van Houteghem, Nancy; Devlieghere, Frank; Rajkovic, Andreja; Gómez, Sandra Maria Osés; Uyttendaele, Mieke; Debevere, Johan

    2008-03-31

    To assure the microbiological safety and quality of a food product, a combination of preservation hurdles is often used. Therefore, the effects of carbon dioxide at concentrations of 0, 20, 40 and 60% in modified atmospheres on the resuscitation of Listeria monocytogenes cells injured by mild bactericidal treatments during storage at 7 degrees C were examined. The bactericidal treatments were intense light pulses (ILP), chlorine dioxide (ClO(2)), lactic acid (LA) and heat. The results indicated additional bactericidal effects of CO(2) on cultures treated with LA, ClO(2) and ILP, with additional reductions in viable L. monocytogenes of 0.5-1.0 log cfu/ml. Lag phase duration was significantly different between the different treatments, with non-treated cells having the shortest lag phase, followed by that of heat, intense light pulses, lactic acid and finally ClO(2) treated cells. Maximum growth rate was also estimated and results showed a negative correlation with increasing CO(2) concentrations. A relationship was found between the amount of sub-lethally damaged cells after a mild inactivation treatment and the lag phase duration in the CO(2) environment. Current findings demonstrate the possibility that combining mild decontamination treatments and packaging in a CO(2) enriched environment could reduce the risk of L. monocytogenes infections in food due to an extension of the lag phase.

  6. Effect of mayonnaise pH and storage temperature on the behavior of Listeria monocytogenes in ham salad and potato salad.

    Science.gov (United States)

    Hwang, Cheng-An

    2005-08-01

    This study examined and modeled the behavior of Listeria monocytogenes in ham salad and potato salad as affected by the pH of mayonnaise and storage temperature. An eight-strain cocktail of L. monocytogenes was inoculated on the surface of diced cooked ham or potato. The inoculated ham or potato was then mixed with regular mayonnaise (pH 3.8) or mayonnaise that was adjusted with NaOH to pH 4.2 or 4.6. The cell counts of L. monocytogenes in the salads during storage at 4, 8, or 12 degrees C were enumerated and used to model the behavior of L. monocytogenes in ham salad or potato salad. At each of the storage temperatures, L. monocytogenes was able to grow in ham salad, whereas L. monocytogenes was inactivated in potato salad. The growth rate (log CFU per hour) in ham salad or the inactivation rate (log CFU per hour) in potato salad increased as the storage temperature increased. The duration before growth in ham salad or inactivation in potato salad increased as storage temperature decreased. The mayonnaise pH showed no consistent effect on the growth rate or inactivation rate and duration before growth or inactivation occurred. Mathematical equations that described the growth rate or inactivation rate of L. monocytogenes in both salads as a function of mayonnaise pH and storage temperature were generated and shown to be satisfactory in describing the growth rate or inactivation rate of L. monocytogenes in the ham salad or potato salad.

  7. 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.

  8. 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...

  9. 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...

  10. Listeria monocytogenes survival in refrigerator dill pickles.

    Science.gov (United States)

    Kim, Jin Kyung; D'Sa, Elaine M; Harrison, Mark A; Harrison, Judy A; Andress, Elizabeth L

    2005-11-01

    Listeria monocytogenes can survive and grow in refrigerated foods with pH values of approximately 4.0 to 5.0 and salt concentrations of 3 to 4%. Home-fermented refrigerator dill pickles fit this description. Contamination of this product with L. monocytogenes could cause serious problems because these items are not heated prior to consumption. L. monocytogenes survival and growth patterns were investigated in refrigerator dill pickles at 1.3, 3.8, and 7.6% salt concentrations. Pickling cucumbers were dipped into an inoculum of L. monocytogenes, brine mixtures were added, and cucumbers were held at room temperature for 1 week and then refrigerated for up to 3 months. The pH, NaCl percentage, titratable acidity percentage, and total populations of Listeria and aerobic, psychrotrophic, and lactic acid bacteria were measured at the addition of brine, after 2, 4, and 7 days of storage at room temperature, and then weekly during refrigerated storage. The initial Listeria population was 5.4 to 5.6 log CFU/cm2 on cucumber surfaces and 3.9 to 4.6 log CFU/g internally. There was an approximate 0.3- to 1-log increase during room temperature fermentation followed by a population decline during refrigerator storage, with a greater decrease in the brines with the highest NaCl concentration. Up to 49 days, the internal tissue of pickles with 1.3, 3.8, or 7.6% salt concentrations were presumptively positive for L. monocytogenes by the enrichment method, and at 91 days the surfaces of such pickles were still positive for L. monocytogenes. Populations of total aerobes and lactic acid bacteria increased during room temperature storage and decreased gradually during refrigerated storage.

  11. Automatic counting and classification of bacterial colonies using hyperspectral imaging

    Science.gov (United States)

    Detection and counting of bacterial colonies on agar plates is a routine microbiology practice to get a rough estimate of the number of viable cells in a sample. There have been a variety of different automatic colony counting systems and software algorithms mainly based on color or gray-scale pictu...

  12. 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.

  13. [Evaluation of the activity of probiotic cultures over Listeria monocytogenes during the production and storage of yogurt].

    Science.gov (United States)

    Berrocal, Darling; Arias, María Laura; Henderson, Marjorie; Wong, Eric

    2002-12-01

    The effect of probiotic cultures over Listeria monocytogenes during the production and storage of yogurt was evaluated. A yogurt mixture (10.6% non-fat solid liquids, 3% fat and 0.3% gelatin) was prepared, homogenized and pasteurized. Yogurt was inoculated with 0, 10(2), 10(4) and 10(6) CFU/mL of L. monocytogenes and 0.02% of traditional lactic culture YC 180 (Streptococcus thermophilus and Lactobacillus bulgaricus) and probiotic culture ABY-1 (Bifidobacterium longum, B. bifidum, B, infantis, Lactobacillus acidophilus, Streptococcus thermophilus y Lactobacillus delbrueckii subsp. bulgaricus). It was incubated for 3 h at 43 degrees C until pH reached an approximate value of 4.8, followed by refrigeration at 5 degrees C for 21 days. During fermentation, samples were taken every hour, and during storage every 3 days, analyzing pH and lactic, bifidobacteria and pathogen count for each time. It was demonstrated that there was no significant simple effect for the type of culture used (ABY-1 and YC 180) (p = 0.684) over the amount of L. monocytogenes present in yogurt during the fermentation and storage periods. The presence of bifidobacteria in the ABY-1 culture did not present a significant effect over L. monocytogenes. Neither the effect of time presented a significant effect over L. monocytogenes (p = 0.448). In this case, the ABY-1 and YC 180 cultures present a bacteriostatic effect over the pathogen. The probiotic cultures had a bacteriostatic but not bactericidal effect over L. monocytogenes. This is not related to the protective effect of these cultures in bowel, since in-vivo conditions favor the production of antimicrobial substances, such as bacteriocins that act over pathogens.

  14. Growth control of Listeria monocytogenes on cold-smoked salmon using a competitive lactic acid bacteria flora.

    Science.gov (United States)

    Nilsson, L; Gram, L; Huss, H H

    1999-04-01

    A Lactobacillus sake strain LKE5 and four strains of Carnobacterium piscicola were evaluated as biopreservation cultures to control the growth of Listeria monocytogenes on vacuum-packed, cold-smoked salmon stored at 5 degrees C. All five strains were antilisterial as live cultures in an agar diffusion assay. Cell-free supernatants of two strains of C. piscicola and L. sake LKE5 were also antilisterial because of the production of bacteriocins. The presence of high cell numbers of strains of C. piscicola had no influence on the sensory quality of cold-smoked salmon stored at 5 degrees C, but L. sake LKE5 caused strong sulfurous off-flavors and was rejected as a culture for biopreservation of cold-smoked salmon. A bacteriocin-producing strain of C. piscicola (A9b) initially caused a 7-day lag phase of L. monocytogenes, followed by a reduction in numbers of L. monocytogenes from 10(3) CFU/ml to below 10 CFU/ml after 32 days of incubation, coinciding with the detection of antilisterial compounds. The presence of a nonbacteriocin-producing strain of C. piscicola (A10a) prevented the growth of L. monocytogenes during the 32-day incubation. The growth of L. monocytogenes was strongly repressed on cold-smoked salmon in the presence of C. piscicola A9b and A 10a, respectively. The initial cell numbers of L. monocytogenes that were found on Oxford plates incubated at 25 degrees C reached low maximum cell counts of 10(4) and 2 x 10(3) after 14 and 20 days of storage in mixed culture with C. piscicola A9b and A10a.

  15. Listeria monocytogenes serotype 1/2b and 4b isolates from human clinical cases and foods show differences in tolerance to refrigeration and salt stress.

    Science.gov (United States)

    Ribeiro, V B; Destro, M T

    2014-09-01

    Control of Listeria monocytogenes in food processing facilities is a difficult issue because of the ability of this microorganism to form biofilms and adapt to adverse environmental conditions. Survival at high concentrations of sodium chloride and growth at refrigeration temperatures are two other important characteristics of L. monocytogenes isolates. The aim of this study was to compare the growth characteristics under stress conditions at different temperatures of L. monocytogenes serotypes responsible for the majority of clinical cases from different sources. Twenty-two L. monocytogenes isolates, 12 from clinical cases (8 serotype 4b and 4 serotype 1/2a) and 10 from food (6 serotype 4b and 4 serotype 1/2a), and an L. monocytogenes Scott A (serotype 4b) reference strain were analyzed for the ability to grow in brain heart infusion broth plus 1.9 M NaCl (11%) at 4, 10, and 25°C for 73, 42, and 15 days, respectively. The majority of L. monocytogenes strains was viable or even grew at 4°C and under the high osmotic conditions usually used to control pathogens in the food industry. At 10°C, most strains could adapt and grow; however, no significant difference (P > 0.05) was found for lag-phase duration, maximum growth rate, and maximum cell density. At 25°C, all strains were able to grow, and populations increased by up 5 log CFU/ml. Clinical strains had a significantly longer lag phase and lower maximum cell density (P food strains. Regarding virulence potential, no significant differences in hemolytic activity were found among serotypes; however, serotype 4b strains were more invasive in Caco-2 cells than were serotype 1/2a strains (P processed foods for health reasons may facilitate L. monocytogenes survival and growth in these products. Therefore, food companies must consider additional microbial growth barriers to assure product safety.

  16. MICROORGANISMS COUNTING OF VIABLE MESOPHILIC AEROBIC BACTERIA IN NATURAL SALTED CASINGS FROM BOVINE USED IN SAUSAGE ENUMERAÇÃO DE MICROORGANISMOS AERÓBIOS MESÓFILOS VIÁVEIS EM ENVOLTÓRIOS NATURAIS SALGADOS DE BOVINOS EMPREGADOS EM EMBUTIDOS

    Directory of Open Access Journals (Sweden)

    Cláudio Armando Jürgensen

    2007-09-01

    Full Text Available

    Thirty-five samples of natural salted bovine casings, collected in federal inspected meat processing plants, located in the municipality of Goiânia, Goiás, were examined. The bacteria count of mesophilic aerobic bacteria encountered varied between 3.0 x 10³ UFC/g and 1.4 x 10^6 UFC/g.

    Foram examinadas bacteriologicamente 35 amostras de envoltório natural salgado de bovino (intestino delgado, intestino grosso, ceco e bexiga, colhidas em frigoríficos com Inspeção Federal, localizados no município de Goiânia -GO. Avaliou-se, através do grau de contaminação, até que ponto o processamento industrial e o método empregado no preparo das tripas naturais são eficientes na eliminação da microbiota bacteriana presente, encontrando-se enumerações de bactérias aeróbias mesófilas, em todas as amostras examinadas, variações entre 3,0 x 10³ UFC/g e 1,4 x 10^6 UFC/g de tripa.

  17. Survival of Listeria monocytogenes, and other food spoilage microbes in vacuum packaged West African soft cheese 'wara'.

    Science.gov (United States)

    Adetunji, V O

    2012-12-01

    'Wara' soft cheese is traditionally produced in Nigeria and has a poor microbial quality. This study assessed the survivability of Listeria monocytogenes and other food spoilage microbes (enterobacteriacea, molds and yeasts) in vacuum packaged soft cheese treated independently with Carica papaya (Vcpc), Terminalia cattapa (Vtcc) crude extracts, nisin (Vnc), and the combination of these three treatments (V+3) stored at 15 degrees C and 28 degrees C for a three week storage period. Vacuum packaging did not suppress Listeria monocytogenes, and there were no significant differences in the L. monocytogenes counts throughout the storage weeks (P > 0.05). The enterobacteriacea counts were suppressed to undetectable levels at 15 degrees C storage temperature by the third week of storage in all treatments except the Vnc and V+3. Molds and yeasts were undetectable in all treatments throughout the storage weeks. Significant differences occurred in the microbial count at the two storage temperatures and storage weeks (P Vacuum packaging and addition of crude extracts (Carica papaya, Terminalia cattapa) in soft cheese storage can suppress enterobacteriacea, molds and yeasts. Food technologists developing industrialized 'wara should consider including these extracts and vacuum packaging in their production. Therefore, their use in extension of the shelf-life of soft cheese is recommended.

  18. 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...

  19. 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,

  20. 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.

  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. Interaction between Food-borne Pathogens (Campylobacter jejuni, Salmonella Typhimurium and Listeria monocytogenes) and a Common Soil Flagellate (Cercomonas sp.)

    DEFF Research Database (Denmark)

    Bui, Thanh Xuan; Wolff, Anders; Madsen, Mogens

    2012-01-01

    Free-living protozoa may harbor, protect, and disperse bacteria, including those ingested and passed in viable form in feces. The flagellates are very important predators on bacteria in soil, but their role in the survival of food-borne pathogens associated with fruits and vegetables is not well...... understood. In this study, we investigated the interactions between a common soil flagellate, Cercomonas sp., and three different bacterial pathogens (Campylobacter jejuni, Salmonella Typhimurium, and Listeria monocytogenes). Rapid growth of flagellates was observed in co-culture with C. jejuni and S....... Typhimurium over the time course of 15 days. In contrast, the number of Cercomonas sp. cells decreased when grown with or without L. monocytogenes for 9 days of co-culture. Interestingly, we observed that C. jejuni and S. Typhimurium survived better when co-cultured with flagellates than when cultured alone...

  3. Mechanism involved in phagocytosis and killing of Listeria monocytogenes by Acanthamoeba polyphaga.

    Science.gov (United States)

    Akya, Alisha; Pointon, Andrew; Thomas, Connor

    2009-10-01

    Intra-cellular pathogen, Listeria monocytogenes, is capable of invasion and survival within mammalian cells. However, Acanthamoeba polyphaga trophozoites phagocytose and rapidly degrade Listeria cells. In order to provide more information on amoeba phagocytosis and killing mechanisms, this study used several inhibitor agents known to affect the phagocytosis and killing of bacteria by eukaryotes. Amoebae were pre-treated with mannose, cytochalasin D, wortmannin, suramin, ammonium chloride, bafilomycin A and monensin followed by co-culture with bacteria. Phagocytosis and killing of bacterial cells by amoeba trophozoites was assessed using plate counting methods and microscopy. The data presented indicates that actin polymerisation and cytoskeletal rearrangement are involved in phagocytosis of L. monocytogenes cells by A. polyphaga trophozoites. Further, both phagosomal acidification and phagosome-lysosome fusion are involved in killing and degradation of L. monocytogenes cells by A. polyphaga. However, the mannose-binding protein receptor does not play an important role in uptake of bacteria by amoeba trophozoites. In conclusion, this data reveals the similar principles of molecular mechanisms used by different types of eukaryotes in uptake and killing of bacteria.

  4. VIDAS Listeria monocytogenes II (LMO2).

    Science.gov (United States)

    Johnson, Ronald; Mills, John

    2013-01-01

    This AOAC GovVal study compared the VIDAS Listeria monocytogenes II (LMO2) to the Health Products and Food Branch MFHPB-30 reference method for detection of L. monocytogenes in ready-to-eat (RTE) meats. The VIDAS LMO2 test is an automated enzyme-linked fluorescent immunoassay for the detection of L. monocytogenes in foods. The LMO2 test, following the enrichment procedure from the MFLP-33 method, also included use of the chromogenic media, chromID Ottaviani Agosti Agar (OAA) and chromID Lmono for confirmation of LMO2 presumptive results. In previous AOAC validation studies comparing the VIDAS LMO2 method to the U.S. Food and Drug Administration Bacteriological Analytical Manual and U.S. Department of Agriculture-Food Safety and Inspection Service reference methods, LMO2 was approved as AOAC Official Method 2004.02 for the detection of L. monocytogenes in dairy products, vegetables, seafood, raw meats and poultry, and processed meats and poultry. The GovVal comparative study included 20 replicate test portions, each at two contamination levels for each matrix, where fractionally positive results (5-15 positive results/20 replicate portions tested) were obtained by at least one method at one level. Five uncontaminated controls were included. Chi-square analysis of the comparative data in this study indicates no statistical differences between the VIDAS LMO2 and the MFHPB-30 standard methods at the 5% level of significance. Confirmation of presumptive LMO2 results with the chromogenic OAA and Lmono media was shown to be equivalent to the appropriate reference method agars. The data demonstrate that the VIDAS LMO2 method is an acceptable alternative method to the MFHPB-30 standard culture method for the detection of L. monocytogenes in RTE meats, including liver paté, hot dogs, raw fermented sausage, sliced deli turkey, and sliced deli ham.

  5. High-pressure processing and antimicrobial biodegradable packaging to control Listeria monocytogenes during storage of cooked ham.

    Science.gov (United States)

    Marcos, Begonya; Aymerich, Teresa; Monfort, Josep M; Garriga, Margarita

    2008-02-01

    The efficiency of combining high-pressure processing (HPP) and active packaging technologies to control Listeria monocytogenes growth during the shelf life of artificially inoculated cooked ham was assessed. Three lots of cooked ham were prepared: control, packaging with alginate films, and packaging with antimicrobial alginate films containing enterocins. After packaging, half of the samples were pressurized. Sliced cooked ham stored at 6 degrees C experienced a quick growth of L. monocytogenes. Both antimicrobial packaging and pressurization delayed the growth of the pathogen. However, at 6 degrees C the combination of antimicrobial packaging and HPP was necessary to achieve a reduction of inoculated levels without recovery during 60 days of storage. Further storage at 6 degrees C of pressurized antimicrobial packed cooked ham resulted in L. monocytogenes levels below the detection limit (day 90). On the other hand, storage at 1 degrees C controlled the growth of the pathogen until day 39 in non-pressurized ham, while antimicrobial packaging and storage at 1 degrees C exerted a bacteriostatic effect for 60 days. All HPP lots stored at 1 degrees C led to counts <100CFU/g at day 60. Similar results were observed when combining both technologies. After a cold chain break no growth of L. monocytogenes was observed in pressurized ham packed with antimicrobial films, showing the efficiency of combining both technologies.

  6. MudPIT analysis of alkaline tolerance by Listeria monocytogenes strains recovered as persistent food factory contaminants.

    Science.gov (United States)

    Nilsson, Rolf E; Latham, Roger; Mellefont, Lyndal; Ross, Tom; Bowman, John P

    2012-05-01

    Alkaline solutions are used to clean food production environments but the role of alkaline resistance in persistent food factory contamination by Listeria monocytogenes is unknown. We used shotgun proteomics to characterise alkaline adapted L. monocytogenes recovered as persistent and transient food factory contaminants. Three unrelated strains were studied including two persistent and a transient food factory contaminant determined using multilocus sequence typing (MLST). The strains were adapted to growth at pH 8.5 and harvested in exponential phase. Protein extracts were analysed using multidimensional protein identification technology (MudPIT) and protein abundance compared by spectra counting. The strains elicited core responses to alkaline growth including modulation of intracellular pH, stabilisation of cellular processes and reduced cell-division, independent to lineage, MLST or whether the strains were transient or persistent contaminants. Alkaline adaptation by all strains corresponded to that expected in stringent-response induced cells, with protein expression supporting metabolic shifts concordant with elevated alarmone production and indicating that the alkaline-stringent response results from energy rather than nutrient limitation. We believe this is the first report describing induction of a stringent response in different L. monocytogenes strains by alkaline pH under non-limiting growth conditions. The work emphasises the need for early intervention to avoid persistent food factory contamination by L. monocytogenes.

  7. Comparison of different application strategies of divergicin M35 for inactivation of Listeria monocytogenes in cold-smoked wild salmon.

    Science.gov (United States)

    Tahiri, I; Desbiens, M; Kheadr, E; Lacroix, C; Fliss, I

    2009-12-01

    Cold-smoked salmon treated with divergicin M35-producing Carnobacterium divergens M35, C. divergens ATCC 35677 (a non-producer of bacteriocin), purified divergicin M35 or supernatants of C. divergens M35 culture in snow crab hepatopancreas (SCH) medium or MRS broth was challenged with Listeria monocytogenes (up to 10(3) CFU/g). Samples were stored at 4 degrees C for up to four weeks. L. monocytogenes, total bacterial and lactic acid bacterial counts were determined along with changes in total volatile base nitrogen (TVBN) and biogenic amine production as well as texture, color and odor. A 2.6 log CFU/g reduction in L. monocytogenes was obtained for up to 10 days of storage in samples treated with C. divergens M35. Purified divergicin M35 (50 microg/g), SCH supernatant or MRS supernatant brought reductions of 1 log CFU/g at the beginning of storage. However, the anti-listerial activity of the supernatants lasted for 15 days compared to 3 days for purified divergicin M35. Color and texture were affected little in samples containing C. divergens M35 compared to un-inoculated samples. TVBN and biogenic amine production, particularly tyramine, remained below the maximum acceptable level in fish appreciation. These results clearly show the potential of C. divergens M35 culture as well as divergicin M35 bio-ingredient for application to the inactivation of L. monocytogenes in ready-to-eat seafood.

  8. Behavior of Listeria monocytogenes in Sliced Ready-to-Eat Meat Products Packaged under Vacuum or Modified Atmosphere Conditions.

    Science.gov (United States)

    Menéndez, Rosa Ana; Rendueles, Eugenia; Sanz, José Javier; Capita, Rosa; García-Fernández, Camino

    2015-10-01

    The objective of this research was to determine the behavior of Listeria monocytogenes in three types of sliced ready-to-eat meat products packaged under vacuum or modified atmosphere conditions and stored at three temperatures. Slices of about 25 g of chorizo (a fermented dry pork sausage), jamón (cured ham), and cecina (a salted, dried beef product) were inoculated with L. monocytogenes NCTC 11994. Slices were packaged in a vacuum or in a modified atmosphere (20% CO2, 80% N2). After packaging, samples were stored for 6 months at three temperatures: 3, 11, or 20°C. Microbiological analyses were performed after 0, 1, 7, 15, 30, 45, 90, and 180 days of storage. The type of meat product, the type of packaging, the temperature, and the day of storage all influenced microbial levels (P cecina samples, counts of L. monocytogenes increased from day 0 to day 1 of storage and then remained constant until day 90 of the study. These results may be of use for enhancing the safety of these ready-to-eat meat product types. Additional evaluation of the behavior of L. monocytogenes in cecina is needed.

  9. Control of Listeria monocytogenes on frankfurters by dipping in hops beta acids solutions.

    Science.gov (United States)

    Shen, Cangliang; Geornaras, Ifigenia; Kendall, Patricia A; Sofos, John N

    2009-04-01

    Hops beta acids (HBA) are parts of hops flowers used in beer brewing and have shown antilisterial activity in bacteriological broth. The U.S. Department of Agriculture, Food Safety and Inspection Service has approved HBA for use to control Listeria monocytogenes on ready-to-eat meat products. This study evaluated the effects of HBA as dipping solutions to control L. monocytogenes during storage of frankfurters. Frankfurters (two replicates and three samples each) were inoculated (1.9 +/- 0.1 log CFU/cm2) with L. monocytogenes (10-strain mixture), dipped (2 min, 25 +/- 2 degrees C) in HBA solutions (0.03, 0.06, and 0.10%) or distilled water, and then vacuum packaged and stored at 4 or 10 degrees C for up to 90 and 48 days, respectively. Samples were periodically analyzed for microbial survival and growth on tryptic soy agar plus 0.6% yeast extract and PALCAM agar. Dipping in HBA solutions caused immediate L. monocytogenes reductions (P < 0.05) of 1.3 to 1.6 log CFU/cm2, whereas distilled water reduced counts by 1.0 log CFU/cm2. Pathogen growth was completely suppressed (P < 0.05) for 30 to 50 (4 degrees C) or 20 to 28 (10 degrees C) days on frankfurters dipped in HBA solutions, with antilisterial effects increasing with higher concentrations (0.03 to 0.10%). Fitting the data with the Baranyi model confirmed that the lag-phase duration of the pathogen was extended, and the growth rate was decreased on samples dipped in HBA solutions. Therefore, HBA may be considered for use to improve the microbial safety of ready-to-eat meat products, provided that future studies show no adverse effects on sensory qualities and that their use is economically feasible.

  10. 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-organisms<0.4 log CFU/cm(2)). Peracetic acid was the most effective disinfectant, eliminating the multi-species biofilms under all tested conditions (counts of the all microorganisms <0.4 log CFU/cm(2)). In contrast, biguanide was the least effective disinfectant, failing to eliminate biofilms under all the test conditions.

  11. Persistence and Potential Viable but Non-culturable State of Pathogenic Bacteria during Storage of Digestates from Agricultural Biogas Plants

    Science.gov (United States)

    Maynaud, Geraldine; Pourcher, Anne-Marie; Ziebal, Christine; Cuny, Anais; Druilhe, Céline; Steyer, Jean-Philippe; Wéry, Nathalie

    2016-01-01

    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 the storage of

  12. 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

  13. Inhibition of Listeria monocytogenes by Buffered Dry Vinegar in Reduced-Sodium Ready-to-Eat Uncured Turkey Stored at 4°C.

    Science.gov (United States)

    Badvela, Mani K; Dickson, James S; Sebranek, Joseph G; Schroeder, William D

    2016-08-01

    A reduced-sodium ready-to-eat (RTE) uncured turkey was manufactured with buffered dry vinegar treatments to validate the inhibition of Listeria monocytogenes and spoilage microflora and to determine the effects on sensory and quality attributes. Samples were stored at 4°C for 12 weeks, and the study was independently replicated three times. Two different five-strain inocula of L. monocytogenes obtained from different sources were used for evaluating the efficacy of the buffered dry vinegar treatments. The results showed that 0.6 and 0.8% buffered dry vinegar with a sodium base (BDV-SB) and buffered dry vinegar with a potassium base (BDV-PB) at 0.7 and 0.9% controlled L. monocytogenes for 12 weeks. The untreated control product containing no buffered dry vinegar showed >1 log increase in L. monocytogenes populations counts at the end of 2 weeks. Statistical analysis confirmed that the dry vinegar treatments inhibited (P > 0.05) the growth of L. monocytogenes compared with the untreated control. No significant differences (P > 0.05) were seen in the inhibition of L. monocytogenes between the two different five-strain inocula. Instrumental color results showed no significant differences between the treatments. Purge loss results showed no significant differences between the dry vinegar treatments, but significant differences were seen between the untreated control and dry vinegar treatments at a few testing intervals. The overall results indicated that the dry vinegar ingredients (6.66 to 8.83 mM acetic acid in the finished product) were effective in inhibiting L. monocytogenes obtained from multiple sources in reduced-sodium RTE uncured turkey stored at 4°C without adversely impacting the quality attributes.

  14. Effect of salt types and concentrations on the high-pressure inactivation of Listeria monocytogenes in ground chicken.

    Science.gov (United States)

    Balamurugan, S; Ahmed, Rafath; Chibeu, Andrew; Gao, Anli; Koutchma, Tatiana; Strange, Phil

    2016-02-01

    National and international health agencies have recommended a significant reduction in daily intake of sodium by reducing the amount of NaCl in foods, specifically processed meats. However, sodium reduction could increase the risk of survival and growth of spoilage and pathogenic microorganisms on these products. Therefore, alternate processing technologies to improve safety of sodium reduced foods are necessary. This study examined the effects of three different salt types and concentrations on high-pressure inactivation of Listeria monocytogenes in pre-blended ground chicken formulations. Ground chicken formulated with three salt types (NaCl, KCl, CaCl2), at three concentrations (0, 1.5, 2.5%) and inoculated with a four strain cocktail of L. monocytogenes (10(8) CFU g(-1)) were subjected to four pressure treatments (0, 100, 300, 600 MPa) and two durations (60, 180 s) in an experiment with factorial design. Surviving cells were enumerated by plating on Oxford agar and analysed by factorial ANOVA. Pressure treatments at 100 or 300 MPa did not significantly (P=0.19-050) reduce L. monocytogenes populations. Neither salt type nor concentration had a significant effect on L. monocytogenes populations at these pressure levels. At 600 MPa, salt types, concentrations and duration of pressure treatment all had a significant effect on L. monocytogenes populations. Formulations with increasing concentrations of NaCl or KCl showed significantly lower reduction in L. monocytogenes, while increase in CaCl2 concentration resulted in a significantly higher L. monocytogenes reduction. For instance, increase in NaCl concentration from 0 to 1.5 or 2.5% resulted in a log reduction of 6.16, 2.49 and 1.29, respectively, when exposed to 600 MPa for 60s. In the case of CaCl2, increase from 0 to 1.5 or 2.5% resulted in a log reduction of 6.16, 7.28 and 7.47, respectively. These results demonstrate that high-pressure processing is a viable process to improve microbial safety of sodium

  15. Determination of Listeria monocytogenes Growth during Mushroom Production and Distribution

    Directory of Open Access Journals (Sweden)

    Dara Leong

    2013-11-01

    Full Text Available In the EU, food is considered safe with regard to Listeria monocytogenes if its numbers do not exceed 100 CFU/g throughout the shelf-life of the food. Therefore, it is important to determine if a food supports growth of L. monocytogenes. Challenge studies to determine the ability of a food to support growth of L. monocytogenes are essential as predictive modelling often overestimates the growth ability of L. monocytogenes. The aim of this study was to determine if growth of L. monocytogenes was supported during the production and distribution of mushrooms. A three-strain mixture of L. monocytogenes was inoculated onto three independent batches of whole mushrooms, sliced mushrooms, mushroom casing and mushroom substrate at a concentration of about 100–1000 CFU/g. The batches were incubated at potential abuse temperatures, as a worst case scenario, and at intervals during storage L. monocytogenes numbers, % moisture and pH were determined. The results showed that the sliced and whole mushrooms had the ability to support growth, while mushroom casing allowed survival but did not support growth. Mushroom substrate showed a rich background microflora that grew on Listeria selective media and this hindered enumeration of L. monocytogenes. In the case of this study, Combase predictions were not always accurate, indicating that challenge studies may be a necessary part of growth determination of L. monocytogenes.

  16. Autofluorescence of viable cultured mammalian cells.

    Science.gov (United States)

    Aubin, J E

    1979-01-01

    The autofluorescence other than intrinsic protein emission of viable cultured mammalian cells has been investigated. The fluorescence was found to originate in discrete cytoplasmic vesicle-like regions and to be absent from the nucleus. Excitation and emission spectra of viable cells revealed at least two distinct fluorescent species. Comparison of cell spectra with spectra of known cellular metabolites suggested that most, if not all, of the fluorescence arises from intracellular nicotinamide adenine dinucleotide (NADH) and riboflavin and flavin coenzymes. Various changes in culture conditions did not affect the observed autofluorescence intensity. A multiparameter flow system (MACCS) was used to compare the fluorescence intensities of numerous cultured mammalian cells.

  17. Production of viable cultures of Flavobacterium psychrophilum: approach and control.

    Science.gov (United States)

    Michel, C; Antonio, D; Hedrick, R P

    1999-06-01

    Although the fish pathogen Flavobacterium psychrophilum is a major source of concern in salmonid hatcheries, few studies have been conducted on its pathogenicity. Difficulties are often experienced when trying to control or quantify standard procedures for in vitro culture of the bacterium. Plate enumeration and counting chamber enumeration combined with epifluorescent microscopy with fluorescent dyes determined that no more than 25% of the bacterial cells present in the cultures were able to produce colonies on agar media. This was strongly dependent upon different medium components. Tryptone-enriched Anacker and Ordal medium proved more suitable than tryptone-yeast extract-salts with skimmed milk. Adding horse serum and trace elements in controlled proportions offered the most reproducible results. Viable but nonculturable forms were apparently not responsible for the difficulties in production of F. psychrophilum, but the cells were highly susceptible to osmotic conditions. Improvements in the media and careful handling of the bacteria in isotonic suspension media resulted in predictable production of viable bacteria and allowed an absorbance/colony-forming-units relation curve to be established.

  18. Behaviour of Listeria monocytogenes during the manufacture and ripening of Manchego and Chihuahua Mexican cheeses.

    Science.gov (United States)

    Solano-López, C; Hernández-Sánchez, H

    2000-12-05

    The ability of Listeria monocytogenes to survive the Mexican Manchego and Chihuahua cheese-making processes and its persistence during the ripening stages of both cheeses was examined. Commercial pasteurized and homogenized whole milk was inoculated with Listeria monocytogenes (strain ATCC 19114) to a level between 2 x 10(6) and 9 x 10(6) CFU/ml. The milk was used to make Mexican Manchego and Chihuahua cheeses in a 25-l vat. Mexican Manchego cheese was ripened for 5 days and Chihuahua cheese for 6 weeks at 12 degrees C and 85% RH. Listeria present in the cheese was enumerated by diluting samples in sterile 0.1% peptone water and plating on Oxford agar. Duplicate samples were taken at each step of the manufacturing process. During the first week of ripening samples were taken daily from both cheeses. For Chihuahua cheese, samples were taken weekly after the first week of the ripening stage. During the manufacture of Mexican Manchego cheese, Listeria counts remained relatively constant at 10(6) CFU/ml, while with Chihuahua cheese there was a one log decrease in numbers (10(6) to 10(5) CFU/ml). After pressing both curds overnight, numbers of bacteria decreased in Mexican Manchego cheese to 8.2 x 10(5) but increased in Chihuahua cheese from 1.7 x 10(5) to 1.2 x 10(6) CFU/ml. During the ripening stage, counts of Listeria remained constant in both cheeses. However, since the Chihuahua cheese ripening stage is about 6 weeks, the number of bacteria decreased from 2 x 10(6) to 4 x 10(4) CFU/g. The results show that Listeria monocytogenes is able to survive the manufacture and ripening processes of both Mexican cheeses.

  19. Colovesical fistula presenting as Listeria monocytogenes bacteraemia.

    Science.gov (United States)

    Hobbs, Mark

    2015-03-31

    We present a case of colovesical fistula presenting with a clinical syndrome of urosepsis subsequently demonstrated to be due to Listeria monocytogenes bacteraemia. The patient had a history of previous rectal cancer with a low anterior resection and a covering ileostomy that had been reversed 6 months prior to this presentation. L. monocytogenes was also isolated among mixed enteric organisms on urine culture. There were no symptoms or signs of acute gastrointestinal listeriosis or meningoencephalitis. This unusual scenario prompted concern regarding the possibility of communication between bowel and bladder, which was subsequently confirmed with CT and a contrast enema. The patient recovered well with intravenous amoxicillin and to date has declined surgical management of his colovesical fistula. This case illustrates the importance of considering bowel pathology when enteric organisms such as Listeria are isolated from unusual sites.

  20. Adenovirus-based vaccine against Listeria monocytogenes

    DEFF Research Database (Denmark)

    Jensen, Søren; Steffensen, Maria Abildgaard; Jensen, Benjamin Anderschou Holbech

    2013-01-01

    The use of replication-deficient adenoviruses as vehicles for transfer of foreign genes offers many advantages in a vaccine setting, eliciting strong cellular immune responses involving both CD8(+) and CD4(+) T cells. Further improving the immunogenicity, tethering of the inserted target Ag to MHC...... class II-associated invariant chain (Ii) greatly enhances both the presentation of most target Ags, as well as overall protection against viral infection, such as lymphocytic choriomeningitis virus (LCMV). The present study extends this vaccination concept to include protection against intracellular...... bacteria, using Listeria monocytogenes as a model organism. Protection in C57BL/6 mice against recombinant L. monocytogenes expressing an immunodominant epitope of the LCMV glycoprotein (GP33) was greatly accelerated, augmented, and prolonged following vaccination with an adenoviral vaccine encoding GP...

  1. Effect of salts of organic acids on Listeria monocytogenes, shelf life, meat quality, and consumer acceptability of beef frankfurters.

    Science.gov (United States)

    Morey, Amit; Bowers, Jordan W J; Bauermeister, Laura J; Singh, Manpreet; Huang, Tung-Shi; McKee, Shelly R

    2014-01-01

    The objective of this study was to evaluate anti-listerial efficacy of salts of organic acids, and their impact on the quality of frankfurters. Beef frankfurters were manufactured by incorporating organic acids in 5 different combinations: (1) control (no marinade addition; C); (2) sodium lactate (2% wt/wt; SL); (3) potassium lactate (2% wt/wt; PL); (4) sodium citrate (0.75% wt/wt; SC); and (5) sodium lactate (2% wt/wt)/sodium diacetate (0.25% wt/wt; SL/SD). Cooked frankfurters were inoculated with streptomycin-resistant (1500 μg/mL) L. monocytogenes (7 log₁₀ CFU/frank). Inoculated and noninoculated frankfurters were vacuum packaged and stored at 4 °C. Samples were taken weekly up to 10 wk for estimation of L. monocytogenes as well as aerobic plate count (APC) and psychrotrophs (PSY), respectively. Total of 2 independent trials of the entire experiment were conducted. Noninoculated beef frankfurters were evaluated weekly by untrained sensory panelists for 7 wk. SL, PL, and SC treatments did not (P > 0.05) adversely affect consumer acceptability through 8 wk although, SL/SD treatment was significantly (P ≤ 0.05) less preferred across all sensory attributes. SL/SD treatment negatively affected product quality, but was able to control APC, PSY, and L. monocytogenes levels. SC performed similar to the control throughout the 8, 9, and 10 wk storage periods, providing no benefit for inhibiting L. monocytogenes (increasing from 7 logs CFU/frank to 10 logs CFU/frank throughout storage) or extending shelf life of the beef frankfurters. In conclusion, 2% SL and PL, and 2% SL/0.25% SD may be effective L. monocytogenes inhibitors (maintaining inoculation levels of 7 logs CFU/frank during storage), but changes in SL/SD treatment formulation should be studied to improve product quality.

  2. 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.

  3. 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.

  4. [Immunomodulatory role of dietary lipids in an immunosuppressed mouse model and infected with listeria monocytogenes].

    Science.gov (United States)

    Cerón Rodríguez, José María; Puertollano Vacas, M Ángeles; Puertollano Vacas, M Elena; Alvarez de Cienfuegos López, Gerardo

    2014-10-01

    Introducción: La capacidad inmunomoduladora de los ácidos grasos de la dieta en situaciones de inmunosupresión puede diferir de acuerdo con el tipo de ácido graso presente. Objetivo: Analizar el efecto de diferentes tipos de dietas lipídicas, en la resistencia de animales inmunosuprimidos o no, frente a una infección experimental con Listeria monocytogenes. Métodos: Ratones Balb/c fueron divididos en cuatro grupos experimentales, según su tratamiento inmunosupresor: control (PBS), Ciclofosfamida (CPA), GK 1.5 y RB6-8C5. Cada grupo fue subdividido en cuatro subgrupos según la dieta lipídica utilizada: control con aceite de maíz 5% (BG); aceite de oliva 20% (AO); aceite de pescado 20% (AP) y aceite de girasol 20% (AG). Los animales se alimentaron durante un mes antes del tratamiento y posteriormente infectados con L. monocytogenes. Resultados: Mostramos incrementos en el número de bacterias viables en bazo e hígado, y bajos porcentajes de supervivencia en todos los grupos de ratones inmunosuprimidos y también en el grupo PBS alimentado con AP. Además, se observaron incrementos en la linfoproliferación, de bazos de ratones alimentados con AO y tratados con CPA. Discusión: La dieta AP, produce una disminución en la resistencia del hospedador en situaciones de inmunosupresión. Por el contrario, las dietas AO y AG muestran mayor eficacia en la eliminación de L. monocytogenes y mayores ventajas en animales inmunosuprimidos. El tratamiento con RB6-8C5, produce una reducción en la supervivencia de los ratones de los grupos estudiados, lo que induce a establecer que los granulocitos juegan un papel fundamental en el control de la infección.

  5. 78 FR 23901 - Interagency Risk Assessment-Listeria monocytogenes

    Science.gov (United States)

    2013-04-23

    ... Food Safety and Inspection Service Interagency Risk Assessment--Listeria monocytogenes in Retail... risk assessment (QRA), ``Interagency Risk Assessment--Listeria monocytogenes in Retail Delicatessens... and on the FSIS Web site at http://www.fsis.usda.gov/PDF/Listeria-Transcript_062309.pdf ). II....

  6. 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...

  7. 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...

  8. Application Progress of Recombinant Attenuated Listeria monocytogenes in Tumor Immunotherapy

    Institute of Scientific and Technical Information of China (English)

    Yin Xiaojiao; Bai Lin; Yang Xu

    2015-01-01

    Much progress of application of bacterial vaccine in treatment and prevention of tumor was acquired,which showed broad prospect in clinical study of animals and humans. Listeria monocytogenes( L. monocytogenes) was considered much important by virtue of its special characteristic of biology and immunology.L. monocytogenes was ingested by professional or part-time phagocytes,survived and proliferated in the phagocytes under synergism of toxic factor secreted by itself,meanwhile,the cellular and humoral immune response was induced. Antigenic gene of specific tumor was loaded in the attenuated L. monocytogenes,which can enhance immune response of host cells. Effective cell targeted to enter tumor tissue and acted on tumor cells to induce apoptosis of tumor cells. Tumor degenerated not easy to reappear. Therefore,recombinant attenuated L. monocytogenes was a safe and effective anti-cancer vaccine vector. Now the work of researchers mainly focuses on solving practical problem in clinical application. Biological characteristics of L. monocytogenes,feasibility and superiority of L. monocytogenes as targeted vaccine vector,problem and prospect of L. monocytogenes in clinical application of anti-tumor were reviewed in this paper.

  9. 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 concer

  10. 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 ...

  11. 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...

  12. 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.

  13. The Big Pumpkin Count.

    Science.gov (United States)

    Coplestone-Loomis, Lenny

    1981-01-01

    Pumpkin seeds are counted after students convert pumpkins to jack-o-lanterns. Among the activities involved, pupils learn to count by 10s, make estimates, and to construct a visual representation of 1,000. (MP)

  14. Short communication : Appropriate and alternative methods to determine viable bacterial counts in cow milk samples

    NARCIS (Netherlands)

    Loss, G.; Apprich, S.; Kneifel, W.; von Mutius, E.; Genuneit, J.; Braun-Fahrlaender, C.

    2012-01-01

    Farm milk consumption is reported to be inversely related to the development of asthma and atopy in children and it has been hypothesized that microorganisms in milk might contribute to this protective effect. The GABRIEL study was designed to investigate this hypothesis in a large population of Eur

  15. Marine environmental pollution stress detection through direct viable counts of bacteria

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaiah, N.; Kenkre, V.D.; Verlecar, X.N.

    are direct indices of potential bacterial metabolic activity, reliable for sensing metabolic stress experienced by bacterial communities in situ and can be useful for evaluating risks in marine environment through human (industrial) activities....

  16. Comparison of Limulus assay, standard plate count, and total coliform count for microbiological assessment of renovated wastewater.

    Science.gov (United States)

    Jorgensen, J H; Lee, J C; Alexander, G A; Wolf, H W

    1979-05-01

    The Limulus endotoxin assay was compared to the standard plate count and total coliform count for assessment of the bacteriological quality of reclaimed wastewater. A total of 48 water samples from an advanced waste treatment plant in Dallas, Tex. were examined by the three techniques. Limulus assays were technically simpler to perform and provided results much sooner than conventional culture methods. However, the endotoxin values did not correlate extremely well with determinations of viable bacterial numbers. This lack of correlation may have been due to alterations in the normal ratio of viable gram-negative cells to endotoxin caused by water reclamation procedures.

  17. 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.

  18. Effect of soy and milk protein-related compounds on Listeria monocytogenes infection in human enterocyte Caco-2 cells and A/J mice.

    Science.gov (United States)

    Kuda, Takashi; Nakamura, Shinsuke; An, Choa; Takahashi, Hajime; Kimura, Bon

    2012-10-15

    Listeria monocytogenes causes listeriosis in humans, mainly through the consumption of ready-to-eat foods such as cheese. Immunocompromised persons, the elderly, and pregnant women and their fetuses or newborns are at the highest risk for the infection. We examined the effects of dietary milk-casein (MC) and soy-protein (SP), and their digested compounds tryptone (TP) and phytone peptone (PP), respectively, on L. monocytogenes invasion and infection in human enterocyte-like Caco-2 cells and A/J mice. Invasion into Caco-2 cells tended to be high with TP. In A/J mice orally infected with L. monocytogenes, viable numbers in the liver and spleen showed a tendency of decreasing with the 20% SP diet compared to the 20% MC diet. SP suppressed the inflammation marker tumour necrosis factor-α in spleen tissue. Furthermore, bacteria lipopolysaccharide (LPS)-stimulated nitric oxide (NO) secretion from murine macrophage RAW 264.7 cells was suppressed by PP more than TP. These results suggest that major dietary proteins might affect infection and inflammation by L. monocytogenes.

  19. Monotone viable trajectories for functional differential inclusions

    Science.gov (United States)

    Haddad, Georges

    This paper is a study on functional differential inclusions with memory which represent the multivalued version of retarded functional differential equations. The main result gives a necessary and sufficient equations. The main result gives a necessary and sufficient condition ensuring the existence of viable trajectories; that means trajectories remaining in a given nonempty closed convex set defined by given constraints the system must satisfy to be viable. Some motivations for this paper can be found in control theory where F( t, φ) = { f( t, φ, u)} uɛU is the set of possible velocities of the system at time t, depending on the past history represented by the function φ and on a control u ranging over a set U of controls. Other motivations can be found in planning procedures in microeconomics and in biological evolutions where problems with memory do effectively appear in a multivalued version. All these models require viability constraints represented by a closed convex set.

  20. Prevalence of Listeria monocytogenes in Idiazabal cheese Prevalencia de Listeria monocytogenes en queso Idiazabal

    Directory of Open Access Journals (Sweden)

    E. Arrese

    2012-12-01

    Full Text Available Introduction: Raw-milk cheese has been identified in risk assessment as a food of greater concern to public health due to listeriosis. Objective: To determine the prevalence and levels of Listeria monocytogenes in semi-hard Idiazabal cheese manufactured by different producers in the Basque Country at consumer level. Methodology: A total of 51 Idiazabal cheese samples were obtained from 10 separate retail establishments, chosen by stratified random sampling. Samples were tested using the official standard ISO procedure 11290-1 for detection and enumeration methods. Results and conclusion: All cheese samples tested negative for L. monocytogenes. However, 9.8% tested positive for Listeria spp., different from L. monocytogenes. Positive samples came from two brands, two were natural and three were smoked. The presence of Listeria spss. suggests that the cheese making process and the hygiene whether at milking or during cheese making could be insufficient.Introducción: Listeria monocytogenes se ha asociado a quesos elaborados a partir de leche cruda, lo que supone un importante riesgo de salud pública debido a la listeriosis. Objetivo: Estudiar la prevalencia y los niveles de L. monocytogenes en quesos Idiazabal semi-curados de distintos productores del País Vasco, a nivel de consumidor. Metodología: Se analizaron 51 muestras de queso Idiazabal procedentes de 10 establecimientos de venta al público; el muestreo fue aleatorio y estratificado. Los análisis se hicieron según el método de detección y de enumeración del procedimiento estandarizado ISO 11290-1. Resultados y conclusión: Todas las muestras dieron negativo para L. monocytogenes. Sin embargo, el 9,8% dio positivo para Listeria spp., distinta de L. monocytogenes. Las muestras positivas procedían de dos marcas, dos eran quesos naturales y tres ahumados. La presencia de Listeria spss. sugiere que el procesado del queso y la higiene durante el ordeño o durante la fabricación podr

  1. Regulation of Viable and Optimal Cohorts

    Energy Technology Data Exchange (ETDEWEB)

    Aubin, Jean-Pierre, E-mail: aubin.jp@gmail.com [VIMADES (Viabilité, Marchés, Automatique, Décisions) (France)

    2015-10-15

    This study deals with the evolution of (scalar) attributes (resources or income in evolutionary demography or economics, position in traffic management, etc.) of a population of “mobiles” (economic agents, vehicles, etc.). The set of mobiles sharing the same attributes is regarded as an instantaneous cohort described by the number of its elements. The union of instantaneous cohorts during a mobile window between two attributes is a cohort. Given a measure defining the number of instantaneous cohorts, the accumulation of the mobile attributes on a evolving mobile window is the measure of the cohort on this temporal mobile window. Imposing accumulation constraints and departure conditions, this study is devoted to the regulation of the evolutions of the attributes which are1.viable in the sense that the accumulations constraints are satisfied at each instant;2.and, among them, optimal, in the sense that both the duration of the temporal mobile window is maximum and that the accumulation on this temporal mobile window is the largest viable one. This value is the “accumulation valuation” function. Viable and optimal evolutions under accumulation constraints are regulated by an “implicit Volterra integro-differential inclusion” built from the accumulation valuation function, solution to an Hamilton–Jacobi–Bellman partial differential equation under constraints which is constructed for this purpose.

  2. Controlling attachment and growth of Listeria monocytogenes in polyvinyl chloride model floor drains using a peroxide chemical, chitosan-arginine, or heat.

    Science.gov (United States)

    Berrang, Mark E; Hofacre, Charles L; Frank, Joseph F

    2014-12-01

    Listeria monocytogenes can colonize a poultry processing plant as a resident in floor drains. Limiting growth and attachment to drain surfaces may help lessen the potential for cross-contamination of product. The objective of this study was to compare a hydrogen peroxide-peroxyacetic acid-based chemical to chitosan-arginine or heat to prevent attachment of or destroy existing L. monocytogenes on the inner surface of model floor drains. L. monocytogenes was introduced to result in about 10(9) planktonic and attached cells within untreated polyvinyl chloride model drain pipes. Treatments (0.13 % peroxide-based sanitizer, 0.1 % chitosan-arginine, or 15 s of hot water at 95 to 100°C) were applied immediately after inoculation or after 24 h of incubation. Following treatment, all pipes were incubated for an additional 24 h; planktonic and attached cells were enumerated by plate count. All treatments significantly (P < 0.05) lowered numbers of planktonic and attached cells recovered. Chitosan-arginine resulted in approximately a 6-log reduction in planktonic cells when applied prior to incubation and a 3-log reduction after the inoculum had a chance to grow. Both heat and peroxide significantly outperformed chitosan-arginine (8- to 9-log reduction) and were equally effective before and after incubation. Heat was the only treatment that eliminated planktonic L. monocytogenes. All treatments were less effective against attached cells. Chitosan-arginine provided about a 4.5-log decrease in attached cells when applied before incubation and no significant decrease when applied after growth. Like with planktonic cells, peroxide-peroxyacetic acid and heat were equally effective before or after incubation, causing decreases ranging from 7 to 8.5 log for attached L. monocytogenes. Applied at the most efficacious time, any of these techniques may lessen the potential for L. monocytogenes to remain as a long-term resident in processing plant floor drains.

  3. Effect of native microflora, waiting period, and storage temperature on Listeria monocytogenes serovars transferred from cantaloupe rind to fresh-cut pieces during preparation.

    Science.gov (United States)

    Ukuku, Dike O; Olanya, Modesto; Geveke, David J; Sommers, Christopher H

    2012-11-01

    The most recent outbreak of listeriosis linked to consumption of fresh-cut cantaloupes indicates the need to investigate the behavior of Listeria monocytogenes in the presence of native microflora of cantaloupe pieces during storage. Whole cantaloupes were inoculated with L. monocytogenes (10(8)-CFU/ml suspension) for 10 min and air dried in a biosafety cabinet for 1 h and then treated (unwashed, water washed, and 2.5% hydrogen peroxide washed). Fresh-cut pieces (∼3 cm) prepared from these melons were left at 5 and 10°C for 72 h and room temperature (20°C) for 48 h. Some fresh-cut pieces were left at 20°C for 2 and 4 h and then refrigerated at 5°C. Microbial populations of fresh-cut pieces were determined by the plate count method or enrichment method immediately after preparation. Aerobic mesophilic bacteria, yeast and mold of whole melon, and inoculated populations of L. monocytogenes on cantaloupe rind surfaces averaged 6.4, 3.3, and 4.6 log CFU/cm(2), respectively. Only H(2)O(2) (2.5%) treatment reduced the aerobic mesophilic bacteria, yeast and mold, and L. monocytogenes populations to 3.8, 0.9, and 1.8 log CFU/cm(2), respectively. The populations of L. monocytogenes transferred from melon rinds to fresh-cut pieces were below detection but were present by enrichment. Increased storage temperatures enhanced the lag phases and growth of L. monocytogenes. The results of this study confirmed the need to store fresh-cut cantaloupes at 5°C immediately after preparation to enhance the microbial safety of the fruit.

  4. ATP as a biomarker of viable microorganisms in clean-room facilities

    Science.gov (United States)

    Venkateswaran, Kasthuri; Hattori, Noriaki; La Duc, Myron T.; Kern, Roger

    2003-01-01

    A new firefly luciferase bioluminescence assay method that differentiates free extracellular ATP (dead cells, etc.) from intracellular ATP (viable microbes) was used to determine the viable microbial cleanliness of various clean-room facilities. For comparison, samples were taken from both clean-rooms, where the air was filtered to remove particles >0.5 microm, and ordinary rooms with unfiltered air. The intracellular ATP was determined after enzymatically degrading the sample's free ATP. Also for comparison, cultivable microbial populations were counted on nutrient-rich trypticase soy agar (TSA) plates. Both the cultivable and ATP-based determinations indicate that the microbial burden was lower in clean-room facilities than in ordinary rooms. However, there was no direct correlation between the two sets of measurements because the two assays measured very different populations. A large fraction of the samples yielded no colony formers on TSA, but were positive for intracellular ATP. Subsequently, genomic DNA was isolated directly from selected samples and 16S rDNA fragments were cloned and sequenced, identifying nearest neighbors, many of which are known to be noncultivable in the media employed. It was concluded that viable microbial contamination can be reliably monitored by measurement of intracellular ATP, and that this method may be considered superior to cultivable colony counts due to its speed and its ability to report the presence of viable but noncultivable organisms. When the detection of nonviable microbes is of interest, the ATP assay can be supplemented with DNA analysis.

  5. ATP as a biomarker of viable microorganisms in clean-room facilities

    Science.gov (United States)

    Venkateswaran, Kasthuri; Hattori, Noriaki; La Duc, Myron T.; Kern, Roger

    2003-01-01

    A new firefly luciferase bioluminescence assay method that differentiates free extracellular ATP (dead cells, etc.) from intracellular ATP (viable microbes) was used to determine the viable microbial cleanliness of various clean-room facilities. For comparison, samples were taken from both clean-rooms, where the air was filtered to remove particles >0.5 microm, and ordinary rooms with unfiltered air. The intracellular ATP was determined after enzymatically degrading the sample's free ATP. Also for comparison, cultivable microbial populations were counted on nutrient-rich trypticase soy agar (TSA) plates. Both the cultivable and ATP-based determinations indicate that the microbial burden was lower in clean-room facilities than in ordinary rooms. However, there was no direct correlation between the two sets of measurements because the two assays measured very different populations. A large fraction of the samples yielded no colony formers on TSA, but were positive for intracellular ATP. Subsequently, genomic DNA was isolated directly from selected samples and 16S rDNA fragments were cloned and sequenced, identifying nearest neighbors, many of which are known to be noncultivable in the media employed. It was concluded that viable microbial contamination can be reliably monitored by measurement of intracellular ATP, and that this method may be considered superior to cultivable colony counts due to its speed and its ability to report the presence of viable but noncultivable organisms. When the detection of nonviable microbes is of interest, the ATP assay can be supplemented with DNA analysis.

  6. Antagonistic activity against Listeria monocytogenes and Escherichia coli from lactic acid bacteria isolated from raw milkAtividade antagonista contra Listeria monocytogenes e Escherichia coli de bactérias ácido láticas isoladas de leite cru

    Directory of Open Access Journals (Sweden)

    Ronaldo Tamanini

    2012-10-01

    Full Text Available Lactic Acid Bacteria (LAB are naturally detected in several foods and can be important on pathogens control. Through production of numerous antimicrobial substances, LAB can inhibit microorganisms such as Listeria monocytogenes and Escherichia coli. Aiming to verify the presence of L. monocytogenes, enumerate E. coli and LAB, and verify the antagonistic activity of isolated LAB against L. monocytogenes and E. coli, samples of raw milk were collected from 45 dairy farms from Agreste region of Pernambuco. For L. monocytogenes detection VIDAS Listeria (bioMeriex system was used while E. coli was enumerated by PetrifilmTM EC (3M after incubation at 35oC for 48 hours. For LAB enumeration, samples were diluted in MRS broth, distributed in PetrifilmTM AC (3M plates and incubated at 30°C for 72 hours in microaerophilic conditions. Antagonism of 671 LAB isolates was determined through spot-on-the-lawn modified methodology using L. monocytogenes ATCC 7644 and E. coli ATCC 25922 as targets. L. monocytogenes was not detected in any milk sample. E. coli counts varied from Bactérias Ácido Láticas (BAL são naturalmente encontradas em vários alimentos e podem ser importantes no controle de patógenos. Por meio da produção de diversas substâncias antimicrobianas, BAL podem inibir microrganismos como Listeria monocytogenes e Escherichia coli. Com o objetivo de verificar a presença de L. monocytogenes, enumerar E. coli e BAL, e verificar a atividade antagonista das BAL isoladas em relação a L. monocytogenes e E. coli foram coletadas amostras de leite cru de 45 propriedades leiteiras da região agreste de Pernambuco. Para detecção de L. monocytogenes foi utilizado o sistema VIDAS Listeria (bioMeriex enquanto E. coli foi enumerada pelo PetrifilmTM EC (3M, após incubação a 35°C por 48 horas. Para contagem de BAL as amostras foram diluídas em caldo MRS, semeadas em placas de PetrifilmTM AC (3M e incubadas a 30°C por 72 horas em microaerofilia. O

  7. PATOGENESIS DE Listeria monocytogenes, MICROORGANISMO ZOONOTICO EMERGENTE.

    OpenAIRE

    Torres, Kirvis; Sierra, Sara; Potou, Raul; Carrascal, Ana; Mercado, Marcela

    2005-01-01

    Listeria monocytogenes además de ser un paradigma para la investigación inmunológica se ha convertido en sistema modelo apropiado para el análisis de los mecanismos moleculares del parasitismo intracelular de otras bacterias. Investigadores en el área de la inmunología se interesaron en este microorganismo cuando se reconoció el riesgo que representaba para la salud pública y la seguridad en la industria de alimentos. Desde mediados de los años 80’s se ha investigado la biología molecular de ...

  8. 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 (p<0.05). Counts of lactic acid bacteria were higher in vegetables 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.

  9. Inhibition of Listeria monocytogenes by Enterococcus mundtii isolated from soil.

    Science.gov (United States)

    Bigwood, T; Hudson, J A; Cooney, J; McIntyre, L; Billington, C; Heinemann, J A; Wall, F

    2012-12-01

    Two bacterial isolates with inhibitory activity against Listeria monocytogenes and Enterococcus faecalis were obtained from soil. Genotypic and phenotypic characterization identified them as Enterococcus mundtii, a species whose ability to compete with L. monocytogenes is relatively unexplored compared to other members of the genus. The thermal stability of the inhibitory factor and its sensitivity to proteolytic enzymes indicate that it is most likely a bacteriocin. Both isolates grew at comparable rates to L. monocytogenes at 5 °C and 10 °C in vitro. One isolate killed L. monocytogenes when it reached concentrations of 10(6)-10(8) CFU ml(-1). Minimum inocula of 10(6) and 10(5) CFU ml(-1) of E. mundtii were required to reduce and maintain L. monocytogenes concentrations beneath the level of detection at 5 °C and 10 °C, respectively. In situ experiments at 5 °C showed that E. mundtii inhibited the growth of L. monocytogenes on vacuum-packed cold smoked salmon during its four week shelf life. E. mundtii could, therefore, control the growth of L. monocytogenes at low temperatures, indicating a potential application in controlling this pathogen in chilled foods. To control growth of Listeria, the concentration of E. mundtii needs to be high, but it is possible that a purified bacteriocin could be used to achieve the same effect.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Natural transfer of viable microbes in space.

    Science.gov (United States)

    Mileikowsky, C; Cucinotta, F A; Wilson, J W; Gladman, B; Horneck, G; Lindegren, L; Melosh, J; Rickman, H; Valtonen, M; Zheng, J Q

    2000-06-01

    The possibility and probability of natural transfer of viable microbes from Mars to Earth and Earth to Mars traveling in meteoroids during the first 0.5 Ga and the following 4 Ga are investigated, including: --radiation protection against the galactic cosmic ray nuclei and the solar rays, dose rates as a function of the meteorite's radial column mass (radius x density), combined with dose rates generated by natural radioactivity within the meteorite; and survival curves for some bacterial species using NASA's HZETRN transport code --other factors affecting microbe survival: vacuum; central meteorite temperatures at launch, orbiting, and arrival; pressure and acceleration at launch; spontaneous DNA decay; metal ion migration --mean sizes and numbers of unshocked meteorites ejected and percentage falling on Earth, using current semiempirical results --viable flight times for the microbe species Bacillus subtilis and Deinococcus radiodurans R1 --the approximate fraction of microbes (with properties like the two species studied) viably arriving on Earth out of those ejected from Mars during the period 4 Ga BP to the present time, and during the 700 Ma from 4.5 to 3.8 Ga. Similarly, from Earth to Mars. The conclusion is that if microbes existed or exist on Mars, viable transfer to Earth is not only possible but also highly probable, due to microbes' impressive resistance to the dangers of space transfer and to the dense traffic of billions of martian meteorites which have fallen on Earth since the dawn of our planetary system. Earth-to-Mars transfer is also possible but at a much lower frequency.

  15. Parejas viables que perduran en el tiempo

    OpenAIRE

    Juan José Cuervo Rodríguez

    2013-01-01

    El presente artículo científico presenta resultados del proceso llevado a cabo en el proyecto de investigación docente "Mecanismos de autorregulación en parejas viables que perduran en el tiempo". Se soporta en una mirada compleja de la psicología basada en una epistemología de la construcción. En el ámbito metodológico, se inscribe en los estudios de terapia familiar desde una perspectiva de la comunicación humana como un todo integrado. Participaron nueve parejas. Los criterios de inclusión...

  16. Commercially viable strategies for enhancing coal quality

    Energy Technology Data Exchange (ETDEWEB)

    A. Patwardhan; Y.P. Chugh [Southern Illinois University, Carbondale, IL (United States). Department of Mining and Mineral Resources Engineering

    2005-12-01

    The focus of this research is on coal quality enhancement, which includes reduction in the sulfur content and increase in heating value through simple, innovative, and commercially viable coal cleaning strategies. These strategies involve fine coal cleaning, plant optimization, partial coarse coal liberation, and multiple product generation. Evaluations on five mines in Illinois have indicated a potential to reduce the sulfur dioxide emission potential of these coals by up to 20%, while increasing the product heating value by up to 250 kcal/kg (450 BTU/lb). In addition, increases in coal yield by 2-6% are predicted depending on the specific conditions at the evaluated mine.

  17. Health Physics counting room

    CERN Multimedia

    1970-01-01

    The Health Physics counting room, where the quantity of induced radioactivity in materials is determined. This information is used to evaluate possible radiation hazards from the material investigated.

  18. LACTIC FLORA-LISTERIA MONOCYTOGENES INTERACTION

    Directory of Open Access Journals (Sweden)

    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.

  19. 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.

  20. Reduced growth of Listeria monocytogenes in two model cheese microcosms is not associated with individual microbial strains.

    Science.gov (United States)

    Imran, Muhammad; Bré, Jean-Michel; Guéguen, Marielle; Vernoux, Jean-Paul; Desmasures, Nathalie

    2013-02-01

    Two model antilisterial microbial communities consisting of two yeasts, two Gram positive and two Gram negative bacteria, and originating from Livarot cheese smear were previously designed. They were used in the present study to analyse the impact of microbial population dynamics on growth of Listeria monocytogenes in cheese microcosm. Specific culture media and PCR primers were developed for simultaneous culture-dependent and real-time PCR quantification of strains belonging to Marinomonas sp., Paenibacillus sp., Staphylococcus equorum, Arthrobacter arilaitensis, Pseudomonas putida, Serratia liquefaciens, Candida natalensis, and Geotrichum candidum, in cheese microcosms. All strains were enumerated after 3, 5, 8 and 14 days at 15 °C. They established well at high counts in all cheese microcosms. Growth dynamics for all strains in presence of L. monocytogenes WSLC 1685 were compared to those of microbial communities obtained by omitting in turn one of the six members of the initial community. The growth of the microbial strains was neither markedly disturbed by Listeria presence nor by the removal of each strain in turn. Furthermore, these communities had a significant reducing effect on growth of L. monocytogenes independently of pH, as confirmed by mathematical modelling. A barrier effect was observed, that could be explained by specific competition for nutrients.

  1. High hydrostatic pressure and biopreservation of dry-cured ham to meet the Food Safety Objectives for Listeria monocytogenes.

    Science.gov (United States)

    Hereu, Anna; Bover-Cid, Sara; Garriga, Margarita; Aymerich, Teresa

    2012-03-15

    This work aimed to evaluate the effect of nisin application (biopreservation) combined with high hydrostatic pressure processing (HHP) on the behavior of Listeria monocytogenes CTC1034 intentionally inoculated (at ca. 10(7)cells/g) onto the surface of ready-to-eat (RTE) sliced dry-cured ham. Two types of dry-cured ham, which had different water activities and fat contents were studied (a(w) of 0.92 and 14.25% fat and a(w) of 0.88 and 33.26% fat). Three batches were prepared for each type of product: (C) control, without nisin; (N) nisin directly applied (200 AU/cm(2)) and (F) nisin applied through active packaging, polyvinyl alcohol films with 200 AU/cm(2). Half of the samples were pressurized at 600 MPa for 5min. Counts of L. monocytogenes were periodically monitored throughout 60 days of storage at 8°C. The physico-chemical characteristics of the products enabled the survival of L. monocytogenes, but it was significantly reduced by the presence of nisin. The effect of biopreservation was greater when applied directly to the surface and in the product with lower water activity in comparison with the active packaging and the high water activity products, respectively. The immediate inactivation of L. monocytogenes by HHP ranged from 1.82 to 3.85 Log units, depending on the type of dry-cured ham. The lower the water activity, the less was the inactivation induced by HHP, both immediately and during storage. The reduction of L. monocytogenes immediately after HHP and during storage was more evident in batches with nisin applied directly to the surface of the product. The pathogen was not detected in some samples from day 5 of storage in the product with higher water activity. The effect of nisin applied through active packaging was lower than the direct application. The results of the present study indicated that HHP, as post-processing listericidal treatment, is more effective (both immediately and long term) than the use of nisin as an antimicrobial measure

  2. HYGIENIC EVALUATIONS AND LISTERIA MONOCYTOGENES BEHAVIOUR IN THE PRODUCTION OF ‘NDUJA DI SPILINGA

    Directory of Open Access Journals (Sweden)

    F. Giarratana

    2011-01-01

    Full Text Available The aim of this work was to study the hygienic and qualitative parameters of a traditional meat product from Calabria, named ‘Nduja di Spilinga, characterised by an high amount in fat (50% and chilli pepper (25%. In this regard, 30 products, weight 500g, were prepared with and without chilli pepper (respectively, p-series: 15 products and np-series:15 products and analysed for the count of Enterobacteria (Ent, Lactic Acid Bacteria (LAB, Gram+Catalase+Cocci (GCC+ and Yeasts. Furthermore pH, aw and Free Fatty Acids (FFA, expressed as percentage of oleic acid on 100g of total fat (TF, were evaluated. Finally, in order to estimate the potential compliance with the Regulation (EC 2073/05 and further modifications, a challenge test for Listeria monocytogenes was carried out. Obtained data show a high decrease, during the seasoning, of Enterobacteria and L. monocytogenes especially in samples of pseries, according to their lower pH values than np-series samples. With regard to the microflora of technological interest, Yeast were the only population which significantly increases during the seasoning of p-series products, presumably influencing the increase of FFA which reached the highest concentration (5.75% oleic acid/TF at the same time in which Yeasts reached maximum population density (17th day.

  3. Monolaurin and acetic acid inactivation of Listeria monocytogenes attached to stainless steel.

    Science.gov (United States)

    Oh, D H; Marshall, D L

    1996-03-01

    Individual and combined antimicrobial effects of monolaurin and acetic acid on Listeria monocytogenes planktonic cells or stainless-steel-adherent cells were determined in order to evaluate cell viability during a 25-min exposure period at 25 degrees C. A 10(7)-colony-forming units (CFU)/ml population of planktonic cells was completely inactivated by the synergistic combination of 1% acetic acid with 50 or 100 microg/ml of monolaurin within 25 or 20 min, respectively. Either compound alone caused partial but incomplete inactivation within the same time periods. A population of 10(5) CFU/cm2 of 1-day adherent cells on stainless steel was completely inactivated within 25 min, but with the highest concentrations of the combined chemicals, i.e., 1% acetic acid and 100 microg/ml of monolaurin. The combined chemical treatment again synergistically produced greater inhibition. A 10(6)-CFU/cm2 population of 7-day adherent cells was not completely inactivated within 25 min of exposure, although counts did decline. The results demonstrate increased resistance of attached L. monocytogenes to acetic acid and monolaurin and show that resistance increased with culture age. Combinations of organic acids and monolaurin might be considered as sanitizers of food contact surfaces, but activities of such combinations are likely to be less than other commonly used sanitizers.

  4. Association between a case study of asymptomatic ovine listerial mastitis and the contamination of soft cheese and cheese processing environment with Listeria monocytogenes in Portugal.

    Science.gov (United States)

    Pintado, Cristina M B S; Grant, Kathie A; Halford-Maw, Robin; Hampton, Mike D; Ferreira, Maria A S S; McLauchlin, Jim

    2009-06-01

    For 5 months, the udders of milking ewes, raw ewe's milk, cheese, and the plant and environment of a cheese manufacturer in Portugal were investigated using standard methods for the presence of Listeria spp. An association between subclinical mastitis and Listeria monocytogenes in a single lactating sheep was investigated by visual inspection of udders for signs of inflammation, application of somatic cell counts, the California mastitis test, pH measurement to milk, and culture of L. monocytogenes and Staphylococcus spp. To track the routes of contamination by L. monocytogenes, 103 isolates were characterized by molecular serotyping and amplified fragment length polymorphism, and a selection was further tested by pulsed-field gel electrophoresis. This study provides molecular and epidemiological evidence tracking the persistence of a single L. monocytogenes strain causing a subclinical udder infection without obvious inflammation in a single ewe. This infection was the likely source of contamination of raw milk that was subsequently used to produce unpasteurised milk cheese and resulted in a single strain of this bacterium colonizing the processing environment and the final cheese product.

  5. [Evaluation of the effect of probiotic cultures added to commercial yogurt over a known population of Listeria monocytogenes and Escherichia coli O157:H7].

    Science.gov (United States)

    Barrantes, Xinia; Railey, Dylana; Arias, María Laura; Chaves, Carolina

    2004-09-01

    The effect of probiotic cultures over Listeria monocytogenes and Escherichia coli O157:H7 during yogurt storage was evaluated. Two different yogurt brands, one with additional probiotic cultures (Lactobacillus casei and L. acidophilus) were inoculated with known populations (106 UFC/g) of either L. monocytogenes or E. coli O157:H7 in three different times and stored for 32 days at 5 degrees C. Every four days the count of lactic bacteria, the added pathogens and pH was evaluated, according to the methodology described in the Bacteriological Analytical Manual. The pH and lactic bacteria population were constant during the testing period. Yogurt with additional probiotic cultures reduced the population of L. monocytogenes in 8 days, the population of E. coli O157:H7 in 16; yogurt with no additional probiotics took 20 days to reduce L. monocytogenes to non-detectable levels and even after 28 days of storage, E. coli O157:H7 was cultured. In this work, the beneficial effects of additional probiotic cultures in yogurt is confirmed again.

  6. Anarthria impairs subvocal counting.

    Science.gov (United States)

    Cubelli, R; Nichelli, P; Pentore, R

    1993-12-01

    We studied subvocal counting in two pure anarthric patients. Analysis showed that they performed definitively worse than normal subjects free to articulate subvocally and their scores were in the lower bounds of the performances of subjects suppressing articulation. These results suggest that subvocal counting is impaired after anarthria.

  7. EcoCount

    Directory of Open Access Journals (Sweden)

    Phillip P. Allen

    2014-05-01

    Full Text Available Techniques that analyze biological remains from sediment sequences for environmental reconstructions are well established and widely used. Yet, identifying, counting, and recording biological evidence such as pollen grains remain a highly skilled, demanding, and time-consuming task. Standard procedure requires the classification and recording of between 300 and 500 pollen grains from each representative sample. Recording the data from a pollen count requires significant effort and focused resources from the palynologist. However, when an adaptation to the recording procedure is utilized, efficiency and time economy improve. We describe EcoCount, which represents a development in environmental data recording procedure. EcoCount is a voice activated fully customizable digital count sheet that allows the investigator to continuously interact with a field of view during the data recording. Continuous viewing allows the palynologist the opportunity to remain engaged with the essential task, identification, for longer, making pollen counting more efficient and economical. EcoCount is a versatile software package that can be used to record a variety of environmental evidence and can be installed onto different computer platforms, making the adoption by users and laboratories simple and inexpensive. The user-friendly format of EcoCount allows any novice to be competent and functional in a very short time.

  8. A Look inside the Listeria monocytogenes Biofilms Extracellular Matrix

    Directory of Open Access Journals (Sweden)

    Angelo Colagiorgi

    2016-07-01

    Full Text Available Listeria monocytogenes is a foodborne pathogen able to persist in food industry and is responsible for a severe illness called listeriosis. The ability of L. monocytogenes to persist in environments is due to its capacity to form biofilms that are a sessile community of microorganisms embedded in a self-produced matrix of extracellular polymeric substances (EPS’s. In this review, we summarized recent efforts performed in order to better characterize the polymeric substances that compose the extracellular matrix (ECM of L. monocytogenes biofilms. EPS extraction and analysis led to the identification of polysaccharides, proteins, extracellular DNA, and other molecules within the listerial ECM. All this knowledge will be useful for increasing food protection, suggesting effective strategies for the minimization of persistence of L. monocytogenes in food industry environments.

  9. FDA Bacteriological Analytical Manual, Chapter 10, 2003: Listeria monocytogenes

    Science.gov (United States)

    FDA Bacteriological Analytical Manual, Chapter 10 describes procedures for analysis of food samples and may be adapted for assessment of solid, particulate, aerosol, liquid and water samples containing Listeria monocytogenes.

  10. 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...

  11. Pyelonephritis with bacteremia caused by Listeria monocytogenes: A case report.

    Science.gov (United States)

    Uno, Shunsuke; Hase, Ryota; Toguchi, Akihiro; Otsuka, Yoshihito; Hosokawa, Naoto

    2017-02-01

    Listeria monocytogenes is a well-known cause of meningitis, colitis, and bacteremia; however, obstructive pyelonephritis caused by L. monocytogenes has never been reported. We herein report on a 90-year-old Japanese woman with obstructive pyelonephritis and bacteremia due to uterus carcinoma invading the ureter. She was admitted to our hospital complaining of fever and chills, and her physical examination revealed left costovertebral angle tenderness. Computed tomography showed hydronephrosis and complete ureteral obstruction due to tumor invasion. Blood and urine cultures upon nephrostomy revealed the growth of L. monocytogenes. We treated the patient with two weeks of intravenous ampicillin and an additional one-week treatment of oral sulfamethoxazole/trimethoprim. This case shows the importance to recognize L. monocytogenes as a potential causative agent of urinary tract infection. Copyright © 2016 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

  12. Reverse transcriptase real-time PCR for detection and quantification of viable Campylobacter jejuni directly from poultry faecal samples

    DEFF Research Database (Denmark)

    Bui, Thanh Xuan; Wolff, Anders; Madsen, Mogens

    2012-01-01

    and quantification of viable Campylobacter jejuni directly from chicken faecal samples. The results of this method anda DNA-based quantitative real-time PCR (qPCR) method were compared with those of a bacterial culture method. Using bacterial culture andRT-qPCR methods, viable C. jejuni cells could be detected......Campylobacter spp. is the most common cause of bacterial diarrhoea in humans worldwide. Therefore, rapid and reliable methods fordetection and quantification of this pathogen are required. In this study, we have developed a reverse transcription quantitative real-time PCR(RT-qPCR) for detection...... for up to 5 days in both the C. jejuni spiked and the naturally contaminated faecalsamples. We found that no RT-qPCR signals were obtained when viable C. jejuni cells could not be counted by the culture method. In contrast,using a DNA-based qPCR method, dead or non-viable Campylobacter cells were...

  13. Roots of success: cultivating viable community forestry

    Energy Technology Data Exchange (ETDEWEB)

    MacQueen, Duncan

    2009-05-15

    Is community forestry emerging from the shadows? The evidence shows that locally controlled enterprises can be economically viable, and often build on stronger social and environmental foundations than the big private-sector players. Certainly this is an industry in need of a shakeup. Many forests have become flashpoints where agro-industry, large-scale logging concerns and conservation interests clash, while forest-dependent communities are left out in the cold. Meanwhile, governments – driven by concerns over the climate impacts of deforestation – are having to gear up for legal, sustainable forestry production. Community forestry could be crucial to solving many of these challenges. By building on local core capabilities and developing strategic partnerships, they are forging key new business models that could transform the sector.

  14. Viable harvest of monotone bioeconomic models

    CERN Document Server

    De Lara, Michel; Cabrera, Hector Ramirez

    2009-01-01

    Some monospecies age class models, as well as specific multi-species models (with so-called technical interactions), exhibit useful monotonicity properties. This paper deals with discrete time monotone bioeconomics dynamics in the presence of state and control constraints. In practice, these latter ``acceptable configurations'' represent production and preservation requirements to be satisfied for all time, and they also possess monotonicity properties. A state $\\state$ is said to belong to the viability kernel if there exists a trajectory, of states and controls, starting from $\\state$ and satisfying the constraints. Under monotonicity assumptions, we present upper and lower estimates of the viability kernel. This helps delineating domains where a viable management is possible. Numerical examples, in the context of fisheries management, for the Chilean sea bass (\\emph{Dissostichus eleginoides}) and Alfonsino (\\emph{Beryx splendens}) are given.

  15. Caratterizzazione biomolecolare di listeria monocytogenes in suini regolarmente macellati

    OpenAIRE

    Santoro, Cristina

    2009-01-01

    Listeria monocytogenes è un batterio patogeno responsabile di una malattia potenzialmente molto grave per l’uomo. L’infezione avviene soprattutto tramite l’ingestione di alimenti di origine animale contaminati, e può propagarsi per via transplacentare al feto. Il potenziale patogeno di L. monocytogenes è dovuto soprattutto a caratteristici fattori di virulenza con i quali alcuni ceppi sono in grado di attaccare la cellula dell’organismo ospite potendo aderire, invadere, moltiplicare e prop...

  16. 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®

  17. Polymerase chain reaction-based discrimination of viable from non-viable Mycoplasma gallisepticum

    Directory of Open Access Journals (Sweden)

    Ching Giap Tan

    2014-02-01

    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.

  18. 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.

  19. Isolation and Identification of Listeria monocytogenes from Retail

    Directory of Open Access Journals (Sweden)

    A.D.I. Alsheikh

    2013-02-01

    Full Text Available Listeria species are widely distributed in environment and L. monocytogenes are the causal agent of Listeriosis, the disease that can be serious and fatal to human and animals. The objectives of this study were to detect, isolate and identify Listeria monocytogenes from retail broiler chicken ready to eat meat products in restaurants-Khartoum state, Sudan. A total of 250 retail broiler chicken ready to eat meat products were collected from restaurants in Khartoum State, 50 sample from frozen chicken burger, 50 sample from frozen chicken sausages, 50 sample from frozen chicken meat balls (kofta, 50 sample from chicken shawerma and 50 sample from chicken mortedella, Listeria spp. were isolated by the conventional International Organization for Standardization method and L. monocytogenes identified by biochemical test. The results showed that out of total 250 samples, 95 (38% were found to be contaminated with Listeria spp. the isolation rate was as follows: L. monocytogenes (13.6%, L. ivanovi (20.8%, L. grayi (1.6%, L. seeligeri (0.8% and L. welshimeri (1.2%. The results presented in this study indicate the contamination of retail broiler chicken ready to eat meat products with L. monocytogenes. This study reported the occurrence and distribution of L. monocytogenes and other Listeria species in retail meat products (frozen chicken burger, frozen chicken sausages, frozen chicken meat balls (kofta, chicken shawerma and chicken mortedella, purchased from restaurants in Khartoum state Sudan.

  20. Listeria monocytogenes does not survive ingestion by Acanthamoeba polyphaga.

    Science.gov (United States)

    Akya, Alisha; Pointon, Andrew; Thomas, Connor

    2010-03-01

    Listeria monocytogenes is a ubiquitous bacterium capable of infecting humans, particularly pregnant women and immunocompromised individuals. Although the intracellular invasion and pathogenesis of listeriosis in mammalian tissues has been well studied, little is known about the ecology of L. monocytogenes , and in particular the environmental reservoir for this bacterium has not been identified. This study used short-term co-culture at 15, 22 and 37 degrees C to examine the interaction of L. monocytogenes strains with Acanthamoeba polyphaga ACO12. Survival of L. monocytogenes cells phagocytosed by monolayers of trophozoites was assessed by culture techniques and microscopy. A. polyphaga trophozoites eliminated bacterial cells within a few hours post-phagocytosis, irrespective of the incubation temperature used. Wild-type L. monocytogenes and a phenotypic listeriolysin O mutant were unable to either multiply or survive within trophozoites. By contrast, Salmonella enterica serovar Typhimurium C5 cells used as controls were able to survive and multiply within A. polyphaga trophozoites. The data presented indicate that A. polyphaga ACO12 is unlikely to harbour L. monocytogenes, or act as an environmental reservoir for this bacterium.

  1. 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.

  2. 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.

  3. Evolutionary dynamics of the accessory genome of Listeria monocytogenes.

    Directory of Open Access Journals (Sweden)

    Henk C den Bakker

    Full Text Available Listeria monocytogenes, a foodborne bacterial pathogen, is comprised of four phylogenetic lineages that vary with regard to their serotypes and distribution among sources. In order to characterize lineage-specific genomic diversity within L. monocytogenes, we sequenced the genomes of eight strains from several lineages and serotypes, and characterized the accessory genome, which was hypothesized to contribute to phenotypic differences across lineages. The eight L. monocytogenes genomes sequenced range in size from 2.85-3.14 Mb, encode 2,822-3,187 genes, and include the first publicly available sequenced representatives of serotypes 1/2c, 3a and 4c. Mapping of the distribution of accessory genes revealed two distinct regions of the L. monocytogenes chromosome: an accessory-rich region in the first 65° adjacent to the origin of replication and a more stable region in the remaining 295°. This pattern of genome organization is distinct from that of related bacteria Staphylococcus aureus and Bacillus cereus. The accessory genome of all lineages is enriched for cell surface-related genes and phosphotransferase systems, and transcriptional regulators, highlighting the selective pressures faced by contemporary strains from their hosts, other microbes, and their environment. Phylogenetic analysis of O-antigen genes and gene clusters predicts that serotype 4 was ancestral in L. monocytogenes and serotype 1/2 associated gene clusters were putatively introduced through horizontal gene transfer in the ancestral population of L. monocytogenes lineage I and II.

  4. Listeria monocytogenes a pathogen down-to-earth

    Directory of Open Access Journals (Sweden)

    Anne-Laure eVivant

    2013-11-01

    Full Text Available Listeria monocytogenes is the causative agent of the food-borne life threatening disease listeriosis. This pathogenic bacterium received much attention in the endeavour 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.

  5. 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.

  6. Sublattice Counting and Orbifolds

    CERN Document Server

    Hanany, Amihay; Reffert, Susanne

    2010-01-01

    Abelian orbifolds of C^3 are known to be encoded by hexagonal brane tilings. To date it is not known how to count all such orbifolds. We fill this gap by employing number theoretic techniques from crystallography, and by making use of Polya's Enumeration Theorem. The results turn out to be beautifully encoded in terms of partition functions and Dirichlet Series. The same methods apply to counting orbifolds of any toric non-compact Calabi-Yau singularity. As additional examples, we count the orbifolds of the conifold, of the L^{aba} theories, and of C^4.

  7. Modulation of the immune response to Listeria monocytogenes by benzene inhalation.

    Science.gov (United States)

    Rosenthal, G J; Snyder, C A

    1985-09-30

    Benzene is a potent bone marrow toxicant. While all blood cell types are targets for benzene poisoning, lymphocytes are particularly sensitive. The immunotoxic consequences of benzene or its metabolites have been demonstrated in a number of in vitro studies; however, little data exist regarding the effects of benzene on host resistance to infectious agents. This investigation examined the effects of benzene on murine resistance to an infectious agent, Listeria monocytogenes. Four concentrations of benzene were employed, 10, 30, 100, and 300 ppm. To determine recovery from the effects of benzene, two exposure regimens were employed: 5 days prior to infection (preexposure), or 5 days prior to and 7 days during infection (continuous exposure). Appropriate air controls were maintained. Splenic bacterial counts and immune responsive cell populations were determined from mice killed at Days 1, 4, and 7 of infection. Preexposure to benzene produced increased bacterial numbers at Day 4 of the infection only at the highest benzene concentration (300 ppm). In contrast, continuous exposure produced increased bacterial numbers at Day 4 of infection at all but the lowest benzene concentration (10 ppm). Bacteria counts were not increased in any benzene-treated group at Day 1 or Day 7 of infection. The increased bacterial numbers at Day 4 suggest an effect on cell-mediated immune responses. Both T and B lymphocytes were particularly sensitive to benzene exhibiting reductions at all concentrations greater than or equal to 30 ppm for both exposure regimens. Esterase-positive cells, however, were relatively resistant to benzenes effects. The results point to a benzene-induced delay in the immune response to L. monocytogenes.

  8. 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…

  9. 1996 : Track Count Protocol

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The goal of St. Vincent National Wildlife Refuge's Track Count Protocol is to provide an index to the population size of game animals inhabiting St. Vincent Island.

  10. Blood Count Tests

    Science.gov (United States)

    Your blood contains red blood cells (RBC), white blood cells (WBC), and platelets. Blood count tests measure the number and types of cells in your blood. This helps doctors check on your overall health. ...

  11. Counting Belief Propagation

    CERN Document Server

    Kersting, Kristian; Natarajan, Sriraam

    2012-01-01

    A major benefit of graphical models is that most knowledge is captured in the model structure. Many models, however, produce inference problems with a lot of symmetries not reflected in the graphical structure and hence not exploitable by efficient inference techniques such as belief propagation (BP). In this paper, we present a new and simple BP algorithm, called counting BP, that exploits such additional symmetries. Starting from a given factor graph, counting BP first constructs a compressed factor graph of clusternodes and clusterfactors, corresponding to sets of nodes and factors that are indistinguishable given the evidence. Then it runs a modified BP algorithm on the compressed graph that is equivalent to running BP on the original factor graph. Our experiments show that counting BP is applicable to a variety of important AI tasks such as (dynamic) relational models and boolean model counting, and that significant efficiency gains are obtainable, often by orders of magnitude.

  12. Analog multivariate counting analyzers

    CERN Document Server

    Nikitin, A V; Armstrong, T P

    2003-01-01

    Characterizing rates of occurrence of various features of a signal is of great importance in numerous types of physical measurements. Such signal features can be defined as certain discrete coincidence events, e.g. crossings of a signal with a given threshold, or occurrence of extrema of a certain amplitude. We describe measuring rates of such events by means of analog multivariate counting analyzers. Given a continuous scalar or multicomponent (vector) input signal, an analog counting analyzer outputs a continuous signal with the instantaneous magnitude equal to the rate of occurrence of certain coincidence events. The analog nature of the proposed analyzers allows us to reformulate many problems of the traditional counting measurements, and cast them in a form which is readily addressed by methods of differential calculus rather than by algebraic or logical means of digital signal processing. Analog counting analyzers can be easily implemented in discrete or integrated electronic circuits, do not suffer fro...

  13. Housing Inventory Count

    Data.gov (United States)

    Department of Housing and Urban Development — This report displays the data communities reported to HUD about the nature of their dedicated homeless inventory, referred to as their Housing Inventory Count (HIC)....

  14. Allegheny County Traffic Counts

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — Traffic sensors at over 1,200 locations in Allegheny County collect vehicle counts for the Pennsylvania Department of Transportation. Data included in the Health...

  15. 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

  16. Effectiveness of electrolyzed acidic water in killing Escherichia coli O157:H7, Salmonella enteritidis, and Listeria monocytogenes on the surfaces of tomatoes.

    Science.gov (United States)

    Bari, M L; Sabina, Y; Isobe, S; Uemura, T; Isshiki, K

    2003-04-01

    A study was conducted to evaluate the efficacy of electrolyzed acidic water, 200-ppm chlorine water, and sterile distilled water in killing Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes on the surfaces of spot-inoculated tomatoes. Inoculated tomatoes were sprayed with electrolyzed acidic water, 200-ppm chlorine water, and sterile distilled water (control) and rubbed by hand for 40 s. Populations of E. coli O157:H7, Salmonella, and L. monocytogenes in the rinse water and in the peptone wash solution were determined. Treatment with 200-ppm chlorine water and electrolyzed acidic water resulted in 4.87- and 7.85-log10 reductions, respectively, in Escherichia coli O157:H7 counts and 4.69- and 7.46-log10 reductions, respectively, in Salmonella counts. Treatment with 200-ppm chlorine water and electrolyzed acidic water reduced the number of L. monocytogenes by 4.76 and 7.54 log10 CFU per tomato, respectively. This study's findings suggest that electrolyzed acidic water could be useful in controlling pathogenic microorganisms on fresh produce.

  17. Liquid Scintillation Counting

    OpenAIRE

    Carlsson, Sten

    1993-01-01

    In liquid scintillation counting (LSC) we use the process of luminescense to detect ionising radiation emit$ed from a radionuclide. Luminescense is emission of visible light of nonthermal origin. 1t was early found that certain organic molecules have luminescent properties and such molecules are used in LSC. Today LSC is the mostwidespread method to detect pure beta-ernitters like tritium and carbon-14. 1t has unique properties in its efficient counting geometry, deteetability and the lack of...

  18. Counting curves on surfaces

    OpenAIRE

    2015-01-01

    In this paper we consider an elementary, and largely unexplored, combinatorial problem in low-dimensional topology. Consider a real 2-dimensional compact surface $S$, and fix a number of points $F$ on its boundary. We ask: how many configurations of disjoint arcs are there on $S$ whose boundary is $F$? We find that this enumerative problem, counting curves on surfaces, has a rich structure. For instance, we show that the curve counts obey an effective recursion, in the general framework of to...

  19. Counting RG flows

    OpenAIRE

    Gukov, Sergei

    2016-01-01

    Interpreting renormalization group flows as solitons interpolating between different fixed points, we ask various questions that are normally asked in soliton physics but not in renormalization theory. Can one count RG flows? Are there different "topological sectors" for RG flows? What is the moduli space of an RG flow, and how does it compare to familiar moduli spaces of (supersymmetric) dowain walls? Analyzing these questions in a wide variety of contexts --- from counting RG walls to AdS/C...

  20. Evaluation and comparison of SYBR Green I Real-Time PCR and TaqMan Real-Time PCR methods for quantitative assay of Listeria monocytogenes in nutrient broth and milk

    OpenAIRE

    Karatzas, Kimon Andreas G.

    2012-01-01

    Specific traditional plate count method and real-time PCR systems based on SYBR Green I and TaqMan technologies using a specific primer pair and probe for amplification of iap-gene were used for quantitative assay of Listeria monocytogenes in seven decimal serial dilution series of nutrient broth and milk samples containing 1.58 to 1.58×107 cfu /ml and the real-time PCR methods were compared with the plate count method with respect to accuracy and sensitivity. In this study, the plate count m...

  1. Neutron counting with cameras

    Energy Technology Data Exchange (ETDEWEB)

    Van Esch, Patrick; Crisanti, Marta; Mutti, Paolo [Institut Laue Langevin, Grenoble (France)

    2015-07-01

    A research project is presented in which we aim at counting individual neutrons with CCD-like cameras. We explore theoretically a technique that allows us to use imaging detectors as counting detectors at lower counting rates, and transits smoothly to continuous imaging at higher counting rates. As such, the hope is to combine the good background rejection properties of standard neutron counting detectors with the absence of dead time of integrating neutron imaging cameras as well as their very good spatial resolution. Compared to Xray detection, the essence of thermal neutron detection is the nuclear conversion reaction. The released energies involved are of the order of a few MeV, while X-ray detection releases energies of the order of the photon energy, which is in the 10 KeV range. Thanks to advances in camera technology which have resulted in increased quantum efficiency, lower noise, as well as increased frame rate up to 100 fps for CMOS-type cameras, this more than 100-fold higher available detection energy implies that the individual neutron detection light signal can be significantly above the noise level, as such allowing for discrimination and individual counting, which is hard to achieve with X-rays. The time scale of CMOS-type cameras doesn't allow one to consider time-of-flight measurements, but kinetic experiments in the 10 ms range are possible. The theory is next confronted to the first experimental results. (authors)

  2. Developing Viable Financing Models for Space Tourism

    Science.gov (United States)

    Eilingsfeld, F.; Schaetzler, D.

    2002-01-01

    Increasing commercialization of space services and the impending release of government's control of space access promise to make space ventures more attractive. Still, many investors shy away from going into the space tourism market as long as they do not feel secure that their return expectations will be met. First and foremost, attracting investors from the capital markets requires qualifying financing models. Based on earlier research on the cost of capital for space tourism, this paper gives a brief run-through of commercial, technical and financial due diligence aspects. After that, a closer look is taken at different valuation techniques as well as alternative ways of streamlining financials. Experience from earlier ventures has shown that the high cost of capital represents a significant challenge. Thus, the sophistication and professionalism of business plans and financial models needs to be very high. Special emphasis is given to the optimization of the debt-to-equity ratio over time. The different roles of equity and debt over a venture's life cycle are explained. Based on the latter, guidelines for the design of an optimized loan structure are given. These are then applied to simulating the financial performance of a typical space tourism venture over time, including the calculation of Weighted Average Cost of Capital (WACC) and Net Present Value (NPV). Based on a concluding sensitivity analysis, the lessons learned are presented. If applied properly, these will help to make space tourism economically viable.

  3. Economically viable large-scale hydrogen liquefaction

    Science.gov (United States)

    Cardella, U.; Decker, L.; Klein, H.

    2017-02-01

    The liquid hydrogen demand, particularly driven by clean energy applications, will rise in the near future. As industrial large scale liquefiers will play a major role within the hydrogen supply chain, production capacity will have to increase by a multiple of today’s typical sizes. The main goal is to reduce the total cost of ownership for these plants by increasing energy efficiency with innovative and simple process designs, optimized in capital expenditure. New concepts must ensure a manageable plant complexity and flexible operability. In the phase of process development and selection, a dimensioning of key equipment for large scale liquefiers, such as turbines and compressors as well as heat exchangers, must be performed iteratively to ensure technological feasibility and maturity. Further critical aspects related to hydrogen liquefaction, e.g. fluid properties, ortho-para hydrogen conversion, and coldbox configuration, must be analysed in detail. This paper provides an overview on the approach, challenges and preliminary results in the development of efficient as well as economically viable concepts for large-scale hydrogen liquefaction.

  4. Deletion of ultraconserved elements yields viable mice

    Energy Technology Data Exchange (ETDEWEB)

    Ahituv, Nadav; Zhu, Yiwen; Visel, Axel; Holt, Amy; Afzal, Veena; Pennacchio, Len A.; Rubin, Edward M.

    2007-07-15

    Ultraconserved elements have been suggested to retainextended perfect sequence identity between the human, mouse, and ratgenomes due to essential functional properties. To investigate thenecessities of these elements in vivo, we removed four non-codingultraconserved elements (ranging in length from 222 to 731 base pairs)from the mouse genome. To maximize the likelihood of observing aphenotype, we chose to delete elements that function as enhancers in amouse transgenic assay and that are near genes that exhibit markedphenotypes both when completely inactivated in the mouse as well as whentheir expression is altered due to other genomic modifications.Remarkably, all four resulting lines of mice lacking these ultraconservedelements were viable and fertile, and failed to reveal any criticalabnormalities when assayed for a variety of phenotypes including growth,longevity, pathology and metabolism. In addition more targeted screens,informed by the abnormalities observed in mice where genes in proximityto the investigated elements had been altered, also failed to revealnotable abnormalities. These results, while not inclusive of all thepossible phenotypic impact of the deleted sequences, indicate thatextreme sequence constraint does not necessarily reflect crucialfunctions required for viability.

  5. 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 monocytogenes , levels ranged from monocytogenes prevalence ranged from 0.11% (0.03, 0.34) for sprouts (prepackaged) to 1.01% (0.58, 1.74) for raw cut vegetables (prepackaged).

  6. Listeria monocytogenes survival of UV-C radiation is enhanced by presence of sodium chloride, organic food material and by bacterial biofilm formation

    DEFF Research Database (Denmark)

    Bernbom, Nete; Vogel, Birte Fonnesbech; Gram, Lone

    2011-01-01

    a biofilm for 7days before exposure. It is not known if this enhanced survival is due to physiological changes in the attached bacterial cells, a physical protection of the cells in the food matrix or a combination. In conclusion, we demonstrate that UV-C light is a useful extra bacteriocidal step......The bactericidal effect on food processing surfaces of ceiling-mounted UV-C light (wavelength 254nm) was determined in a fish smoke house after the routine cleaning and disinfection procedure. The total aerobic counts were reduced during UV-C light exposure (48h) and the number of Listeria...... monocytogenes positive samples went from 30 (of 68) before exposure to 8 (of 68). We therefore in a laboratory model determined the L. monocytogenes reduction kinetics by UV-C light with the purpose of evaluating the influence of food production environmental variables, such as presence of NaCl, organic...

  7. Parejas viables que perduran en el tiempo

    Directory of Open Access Journals (Sweden)

    Juan José Cuervo Rodríguez

    2013-01-01

    Full Text Available El presente artículo científico presenta resultados del proceso llevado a cabo en el proyecto de investigación docente "Mecanismos de autorregulación en parejas viables que perduran en el tiempo". Se soporta en una mirada compleja de la psicología basada en una epistemología de la construcción. En el ámbito metodológico, se inscribe en los estudios de terapia familiar desde una perspectiva de la comunicación humana como un todo integrado. Participaron nueve parejas. Los criterios de inclusión fueron: cinco o más años de convivencia, participación voluntaria, no presentar (ni haber presentado problemáticas especiales que ameriten intervención psicoterapéutica y la obtención de un porcentaje significativo en el uso de estrategias de comunicación asertiva en la resolución de conflictos. El método general utilizado fue el análisis de la comunicación en tarea de conversación. Los principales hallazgos señalan una estrecha relación entre el contexto de desarrollo de las parejas, la emergencia de códigos comunicacionales propios y la posibilidad de perdurar en el tiempo; también, se resalta el tipo de comunicación asertiva o constructiva, la construcción de valores como el respeto y la aceptación de las diferencias, y el deseo por vivir y construir bienestar común, como elementos constitutivos de su identidad como pareja.

  8. 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

  9. [Blood Count Specimen].

    Science.gov (United States)

    Tamura, Takako

    2015-12-01

    The circulating blood volume accounts for 8% of the body weight, of which 45% comprises cellular components (blood cells) and 55% liquid components. We can measure the number and morphological features of blood cells (leukocytes, red blood cells, platelets), or count the amount of hemoglobin in a complete blood count: (CBC). Blood counts are often used to detect inflammatory diseases such as infection, anemia, a bleeding tendency, and abnormal cell screening of blood disease. This count is widely used as a basic data item of health examination. In recent years, clinical tests before consultation have become common among outpatient clinics, and the influence of laboratory values on consultation has grown. CBC, which is intended to count the number of raw cells and to check morphological features, is easily influenced by the environment, techniques, etc., during specimen collection procedures and transportation. Therefore, special attention is necessary to read laboratory data. Providing correct test values that accurately reflect a patient's condition from the laboratory to clinical side is crucial. Inappropriate medical treatment caused by erroneous values resulting from altered specimens should be avoided. In order to provide correct test values, the daily management of devices is a matter of course, and comprehending data variables and positively providing information to the clinical side are important. In this chapter, concerning sampling collection, blood collection tubes, dealing with specimens, transportation, and storage, I will discuss their effects on CBC, along with management or handling methods.

  10. Papel inmunomodulador de las dietas lipídicas en un modelo murino inmunosuprimido e infectado con Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    José María Cerón Rodríguez

    Full Text Available Introducción: La capacidad inmunomoduladora de los ácidos grasos de la dieta en situaciones de inmunosupresión puede diferir de acuerdo con el tipo de ácido graso presente. Objetivo: Analizar el efecto de diferentes tipos de dietas lipídicas, en la resistencia de animales inmunosuprimidos o no, frente a una infección experimental con Listeria monocytogenes. Métodos: Ratones Balb/c fueron divididos en cuatro grupos experimentales, según su tratamiento inmunosupresor: control (PBS, Ciclofosfamida (CPA, GK 1.5 y RB6-8C5. Cada grupo fue subdividido en cuatro subgrupos según la dieta lipídica utilizada: control con aceite de maíz 5% (BG; aceite de oliva 20% (AO; aceite de pescado 20% (AP y aceite de girasol 20% (AG. Los animales se alimentaron durante un mes antes del tratamiento y posteriormente infectados con L. monocytogenes. Resultados: Mostramos incrementos en el número de bacterias viables en bazo e hígado, y bajos porcentajes de supervivencia en todos los grupos de ratones inmunosuprimidos y también en el grupo PBS alimentado con AP. Además, se observaron incrementos en la linfoproliferación, de bazos de ratones alimentados con AO y tratados con CPA. Discusión: La dieta AP, produce una disminución en la resistencia del hospedador en situaciones de inmunosupresión. Por el contrario, las dietas AO y AG muestran mayor eficacia en la eliminación de L. monocytogenes y mayores ventajas en animales inmunosuprimidos. El tratamiento con RB6-8C5, produce una reducción en la supervivencia de los ratones de los grupos estudiados, lo que induce a establecer que los granulocitos juegan un papel fundamental en el control de la infección.

  11. 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.

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

    Science.gov (United States)

    Zhu, Qi; Gooneratne, Ravi; Hussain, Malik Altaf

    2017-01-01

    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. PMID:28282938

  13. 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 (concentration was estimated at 14-17 CFU/kg. Validation showed good agreement between observed and predicted prevalence (error = -2.17%). The results showed that all 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

  14. Photon counting digital holography

    Science.gov (United States)

    Demoli, Nazif; Skenderović, Hrvoje; Stipčević, Mario; Pavičić, Mladen

    2016-05-01

    Digital holography uses electronic sensors for hologram recording and numerical method for hologram reconstruction enabling thus the development of advanced holography applications. However, in some cases, the useful information is concealed in a very wide dynamic range of illumination intensities and successful recording requires an appropriate dynamic range of the sensor. An effective solution to this problem is the use of a photon-counting detector. Such detectors possess counting rates of the order of tens to hundreds of millions counts per second, but conditions of recording holograms have to be investigated in greater detail. Here, we summarize our main findings on this problem. First, conditions for optimum recording of digital holograms for detecting a signal significantly below detector's noise are analyzed in terms of the most important holographic measures. Second, for time-averaged digital holograms, optimum recordings were investigated for exposures shorter than the vibration cycle. In both cases, these conditions are studied by simulations and experiments.

  15. Rainflow counting revisited

    Energy Technology Data Exchange (ETDEWEB)

    Soeker, H. [Deutsches Windenergie-Institut (Germany)

    1996-09-01

    As state of the art method the rainflow counting technique is presently applied everywhere in fatigue analysis. However, the author feels that the potential of the technique is not fully recognized in wind energy industries as it is used, most of the times, as a mere data reduction technique disregarding some of the inherent information of the rainflow counting results. The ideas described in the following aim at exploitation of this information and making it available for use in the design and verification process. (au)

  16. Listeria monocytogenes in renal transplant recipients Listeria monocytogenes em pacientes pós-transplante renal

    Directory of Open Access Journals (Sweden)

    Cristina Barroso HOFER

    1999-11-01

    Full Text Available Five cases of Listeria monocytogenes bacteriemia were observed from April to December 1985, among renal transplant recipients from the same hospital in São Paulo, Brazil. The patients were adults (mean age: 40.6 years, and the basic complain was fever, with no report of meningeal syndrome. Laboratory tests revealed the presence of two serovars, 1/2a and 4b, which were classified into three lysotypes. The four strains of serovar 4b showed the same antibiotype, with resistance to cefoxitin, clindamycin, oxacillin and penicillin.No período de abril a dezembro de 1985, foram observados cinco casos de listeriose em transplantados renais num mesmo hospital de São Paulo, SP. Os pacientes eram adultos (média de 40,6 anos tendo como queixa básica a febre. Laboratorialmente, em todos foram reconhecidos Listeria monocytogenes, caracterizada por dois sorovares 1/2a e 4b e três lisotipos distintos. As amostras do sorovar 4b apresentaram o mesmo antibiotipo: resistentes à cefoxitina, clindamicina, oxacilina e penicilina.

  17. 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.

  18. 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.

  19. 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...

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

    DEFF Research Database (Denmark)

    Harmsen, Morten; Lappann, Martin; Knøchel, S

    2010-01-01

    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...... (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...... 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...

  1. Case of Contamination by Listeria Monocytogenes in Mozzarella Cheese

    Science.gov (United States)

    Tolli, Rita; Bossù, Teresa; Rodas, Eda Maria Flores; Di Giamberardino, Fabiola; Di Sirio, Alessandro; Vita, Silvia; De Angelis, Veronica; Bilei, Stefano; Sonnessa, Michele; Gattuso, Antonietta; Lanni, Luigi

    2014-01-01

    Following a Listeria monocytogenes detection in a mozzarella cheese sampled at a dairy plant in Lazio Region, further investigations have been conducted both by the competent Authority and the food business operatordairy factory (as a part of dairy factory HACCP control). In total, 90 dairy products, 7 brine and 64 environmental samples have been tested. The prevalence of Listeria monocytogenes was 24.4% in mozzarella cheese, and 9.4% in environmental samples, while brines were all negatives. Forty-seven strains of L. monocytogenes have been isolated, all belonging to 4b/4e serotype. In 12 of these, the macrorestriction profile has been determined by means of pulsed field gel electrophoresis. The profiles obtained with AscI enzyme showed a 100% similarity while those obtained with ApaI a 96.78% similarity. These characteristics of the isolated strains jointly with the production process of mozzarella cheese has allowed to hypothesise an environmental contamination. PMID:27800317

  2. Rhombencephalitis caused by Listeria monocytogenes in a pastured bull.

    Science.gov (United States)

    Matto, Carolina; Varela, Gustavo; Mota, María Inés; Gianneechini, Ruben; Rivero, Rodolfo

    2017-03-01

    A pastured 2-y-old cross-breed bull developed brainstem encephalitis (rhombencephalitis); Listeria monocytogenes was isolated from the brain. In the brainstem, there was perivascular cuffing, multiple microabscesses, and positive immunostaining for L. monocytogenes. Samples of bovine feces, water, feedstuffs, milking parlor soil, and bulk tank milk were collected from the dairy farm. Seven isolates of the genus Listeria were obtained, 6 of L. innocua and 1 of L. monocytogenes, which was found in the pasture where the bull grazed. Both isolates belonged to serotype 4b and were positive for internalins A, C, and J. According to the DNA fragment patterns of pulsed-field gel electrophoresis, the isolates were closely related. The source of infection was the pasture, implying that listeriosis should not be discounted in cases with compatible clinical signs but the absence of silage feeding.

  3. Evaluating the growth of Listeria monocytogenes in refrigerated ready-to-eat frankfurters: influence of strain, temperature, packaging, lactate and diacetate, and background microflora.

    Science.gov (United States)

    Pal, Amit; Labuza, Theodore P; Diez-Gonzalez, Francisco

    2008-09-01

    This research was conducted to study the growth of Listeria monocytogenes inoculated on frankfurters stored at different conditions as a basis for a safety-based consume by shelf life date label. Three L. monocytogenes strains were separately inoculated at 10 to 20 CFU/cm2 onto frankfurters that were previously formulated with or without high pressure and with or without added 2% potassium lactate (PL) and 0.2% sodium diacetate (SD). Inoculated frankfurters were air or vacuum packaged; stored at 4, 8, or 12 degrees C; and L. monocytogenes and psychrotrophic plate counts were determined for 90, 60, and 45 days, respectively, or until the stationary phase was reached. The data (log CFU per square centimeter versus time) were fitted using the Baranyi-Roberts model to determine maximum growth rates and lag-phase time. The maximum growth rates and the lag time under each growth condition were used to calculate the time to reach 100-fold the initial Listeria population. In frankfurters lacking PL and SD, the count of all strains increased by 2 log after 18 to 50 days at 4 degrees C and 4 to 13 days at 8 degrees C. The growth was inhibited at 4 and 8 degrees C in frankfurters containing PL and SD, but one ribotype was capable of growing, with the time to reach 100-fold the initial Listeria population ranging from 19 to 35 days at 12 degrees C. In most cases, the time to reach 100-fold the initial Listeria population of L. monocytogenes was significantly longer in vacuum-packaged frankfurters as compared with air-packaged samples. Inclusion of PL and SD also inhibited the growth of psychrotrophs, but at all temperatures the psychrotrophic plate counts were greater than 4 log CFU/cm2 at the end of the experiments. These results indicated that despite the use of antimicrobials, certain L. monocytogenes strains could be capable of growing under storage-abuse conditions. Growth kinetics data could be useful for establishing a shelf life date label protocol under different

  4. What Counts as Evidence?

    Science.gov (United States)

    Dougherty Stahl, Katherine A.

    2014-01-01

    Each disciplinary community has its own criteria for determining what counts as evidence of knowledge in their academic field. The criteria influence the ways that a community's knowledge is created, communicated, and evaluated. Situating reading, writing, and language instruction within the content areas enables teachers to explicitly…

  5. Reticulocyte Count Test

    Science.gov (United States)

    ... may be ordered when: CBC results show a decreased RBC count and/or a decreased hemoglobin and hematocrit A healthcare practitioner wants to ... and hematocrit, to help determine the degree and rate of overproduction of RBCs ... during pregnancy . Newborns have a higher percentage of reticulocytes, but ...

  6. What Counts as Prostitution?

    Directory of Open Access Journals (Sweden)

    Stuart P. Green

    2016-08-01

    Full Text Available What counts, or should count, as prostitution? In the criminal law today, prostitution is understood to involve the provision of sexual services in exchange for money or other benefits. But what exactly is a ‘sexual service’? And what exactly is the nature of the required ‘exchange’? The key to answering these questions is to recognize that how we choose to define prostitution will inevitably depend on why we believe one or more aspects of prostitution are wrong or harmful, or should be criminalized or otherwise deterred, in the first place. These judgements, in turn, will often depend on an assessment of the contested empirical evidence on which they rest. This article describes a variety of real-world contexts in which the ‘what counts as prostitution’ question has arisen, surveys a range of leading rationales for deterring prostitution, and demonstrates how the answer to the definition question depends on the answer to the normative question. The article concludes with some preliminary thoughts on how analogous questions about what should count as sexual conduct arise in the context of consensual offences such as adultery and incest, as well as non-consensual offences such as sexual assault.

  7. Keberadaan Bakteri Listeria monocytogenes pada Keju Gouda Produksi Lokal dan Impor (PRESENCE OF LISTERIA MONOCYTOGENES IN LOCAL AND IMPORTED GOUDA CHEESES)

    OpenAIRE

    Debby Fadhilah Pazra; Trioso Purnawarman; Denny Widaya Lukman

    2014-01-01

    Listeria monocytogenes is included in the foodborne pathogen, which has been associated with severaloutbreaks of human listeriosis especially in high risk groups. Listeria monocytogenes could be found inGouda cheeses because of poor hygienic and sanitation practices. In addition, this bacteria could surviveduring the making of cheese and cheese ripening process. The purpose of this study was to identify thepresence of L. monocytogenes in local and imported Gouda cheeses and how the safety lev...

  8. Diversity and distribution of Listeria monocytogenes in meat processing plants.

    Science.gov (United States)

    Martín, Belén; Perich, Adriana; Gómez, Diego; Yangüela, Javier; Rodríguez, Alicia; Garriga, Margarita; Aymerich, Teresa

    2014-12-01

    Listeria monocytogenes is a major concern for the meat processing industry because many listeriosis outbreaks have been linked to meat product consumption. The aim of this study was to elucidate L. monocytogenes diversity and distribution across different Spanish meat processing plants. L. monocytogenes isolates (N = 106) collected from food contact surfaces of meat processing plants and meat products were serotyped and then characterised by multilocus sequence typing (MLST). The isolates were serotyped as 1/2a (36.8%), 1/2c (34%), 1/2b (17.9%) and 4b (11.3%). MLST identified ST9 as the most predominant allelic profile (33% of isolates) followed by ST121 (16%), both of which were detected from several processing plants and meat products sampled in different years, suggesting that those STs are highly adapted to the meat processing environment. Food contact surfaces during processing were established as an important source of L. monocytogenes in meat products because the same STs were obtained in isolates recovered from surfaces and products. L. monocytogenes was recovered after cleaning and disinfection procedures in two processing plants, highlighting the importance of thorough cleaning and disinfection procedures. Epidemic clone (EC) marker ECI was identified in 8.5%, ECIII was identified in 2.8%, and ECV was identified in 7.5% of the 106 isolates. Furthermore, a selection of presumably unrelated ST9 isolates was analysed by multi-virulence-locus sequence typing (MVLST). Most ST9 isolates had the same virulence type (VT11), confirming the clonal origin of ST9 isolates; however, one ST9 isolate was assigned to a new VT (VT95). Consequently, MLST is a reliable tool for identification of contamination routes and niches in processing plants, and MVLST clearly differentiates EC strains, which both contribute to the improvement of L. monocytogenes control programs in the meat industry. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Analytical bioconjugates, aptamers, enable specific quantitative detection of Listeria monocytogenes.

    Science.gov (United States)

    Lee, Sang-Hee; Ahn, Ji-Young; Lee, Kyeong-Ah; Um, Hyun-Ju; Sekhon, Simranjeet Singh; Sun Park, Tae; Min, Jiho; Kim, Yang-Hoon

    2015-06-15

    As a major human pathogen in the Listeria genus, Listeria monocytogenes causes the bacterial disease listeriosis, which is a serious infection caused by eating food contaminated with the bacteria. We have developed an aptamer-based sandwich assay (ABSA) platform that demonstrates a promising potential for use in pathogen detection using aptamers as analytical bioconjugates. The whole-bacteria SELEX (WB-SELEX) strategy was adopted to generate aptamers with high affinity and specificity against live L. monocytogenes. Of the 35 aptamer candidates tested, LMCA2 and LMCA26 reacted to L. monocytogenes with high binding, and were consequently chosen as sensing probes. The ABSA platform can significantly enhance the sensitivity by employing a very specific aptamer pair for the sandwich complex. The ABSA platform exhibited a linear response over a wide concentration range of L. monocytogenes from 20 to 2×10(6) CFU per mL and was closely correlated with the following relationship: y=9533.3x+1542.3 (R(2)=0.99). Our proposed ABSA platform also provided excellent specificity for the tests to distinguish L. monocytogenes from other Listeria species and other bacterial genera (3 Listeria spp., 4 Salmonella spp., 2 Vibrio spp., 3 Escherichia coli and 3 Shigella spp.). Improvements in the sensitivity and specificity have not only facilitated the reliable detection of L. monocytogenes at extremely low concentrations, but also allowed for the development of a 96-well plate-based routine assay platform for multivalent diagnostics. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Transferable tetracycline resistance in Listeria monocytogenes from food in Italy.

    Science.gov (United States)

    Pourshaban, Manoocheher; Ferrini, Anna Maria; Mannoni, Veruscka; Oliva, Brunello; Aureli, Paolo

    2002-07-01

    Mechanisms of tetracycline resistance were investigated in two recent Listeria monocytogenes isolates from food, with L. innocua 52P tet(r) as a control. Tetracycline resistance was transferred conjugatively from all three strains to L. ivanovii and from one isolate and the control to Enterococcus faecalis. Molecular analysis demonstrated a chromosomal location for the tet determinant, which was identified as tetM in all cases. These studies are the first to show that L. monocytogenes from food could be a source of tetracycline resistance genes able to spread to other micro-organisms.

  11. 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....

  12. Nalaz bakterije Listeria monocytogenes u ribi i ribljim proizvodima

    OpenAIRE

    Rožman, Jelena; Njari, dr. sc. Bela; Kozačinski, dr. sc. Lidija

    2016-01-01

    Listerioza je bolest koja se prenosi hranom a bakterija Listeria monocytogenes je jedan od najznačajnijih javnozdravstvenih problema i uvjet prometa hrane u svijetu. Prije svega povezana je s konzumacijom gotovih proizvoda. U ovom radu je pretražena svježa riba (brancin) i riblji proizvodi (dimljena i marinirana riba, orada i brancin) na nalaz bakterije L. monocytogenes. Također, pretraženi su uzorci brisova uzeti s radnih površina i ruku djelatnika u pogonima prerade morske ribe. Bakterija L...

  13. 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...... 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-component...

  14. 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

  15. Heat resistance of viable but non-culturable Escherichia coli cells determined by differential scanning calorimetry.

    Science.gov (United States)

    Castro-Rosas, Javier; Gómez-Aldapa, Carlos Alberto; Villagómez Ibarra, José Roberto; Santos-López, Eva María; Rangel-Vargas, Esmeralda

    2017-10-16

    Several reports have suggested that the viable but non-culturable (VBNC) state is a resistant form of bacterial cells that allows them to remain in a dormant form in the environment. Nevertheless, studies on the resistance of VBNC bacterial cells to ecological factors are limited, mainly because techniques that allow this type of evaluation are lacking. Differential scanning calorimetry (DSC) has been used to study the thermal resistance of culturable bacteria but has never been used to study VBNC cells. In this work, the heat resistance of Escherichia coli cells in the VBNC state was studied using the DSC technique. The VBNC state was induced in E. coli ATCC 25922 by suspending bacterial cells in artificial sea water, followed by storage at 3 ± 2°C for 110 days. Periodically, the behaviour of E. coli cells was monitored by plate counts, direct viable counts and DSC. The entire bacterial population entered the VBNC state after 110 days of storage. The results obtained with DSC suggest that the VBNC state does not confer thermal resistance to E. coli cells in the temperature range analysed here. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  16. Uncaria tomentosa extract increases the number of myeloid progenitor cells in the bone marrow of mice infected with Listeria monocytogenes.

    Science.gov (United States)

    Eberlin, Samara; dos Santos, Leonilda M B; Queiroz, Mary L S

    2005-07-01

    In this study, we demonstrated that Uncaria tomentosa extract (UTE) protects mice from a lethal dose of Listeria monocytogenes when administered prophylactically at 50, 100, 150 and 200 mg/kg for 7 days, with survival rates up to 35%. These doses also prevented the myelosuppression and the splenomegaly caused by a sublethal infection with L. monocytogenes, due to increased numbers of granulocyte-macrophage progenitors (CFU-GM) in the bone marrow. Non-infected mice treated with 100 mg/kg UTE also presented higher numbers of CFU-GM in the bone marrow than the controls. Investigation of the production of colony-stimulating factors revealed increased colony-stimulating activity (CSA) in the serum of normal and infected mice pre-treated with UTE. Moreover, stimulation of myelopoiesis and CSA occurred in a dose-dependent manner, a plateaux being reached with the dose of 100 mg/kg. Further studies to investigate the levels of factors such as IL-1 and IL-6 were undertaken. We observed increases in the levels of IL-1 and IL-6 in mice infected with L. monocytogenes and treated with 100 mg/kg of UTE. White blood cells (WBC) and differential counting were also performed, and our results demonstrated no significant changes in these data, when infected mice were pre-treated with 100 mg/kg of UTE. All together, our results suggest that UTE indirectly modulates immune activity and probably disengages Listeria-induced supression of these responses by inducing a higher reserve of myeloid progenitors in the bone marrow in consequence of biologically active cytokine release (CSFs, IL-1 and IL-6).

  17. 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.

  18. 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.

  19. 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. PMID:24294222

  20. Assessment of viable bacteria and bacterial DNA in blood and bloodstain specimens stored under various conditions.

    Science.gov (United States)

    Hosokawa-Muto, Junji; Fujinami, Yoshihito; Mizuno, Natsuko

    2013-11-01

    Microbial forensic specimens that are collected at biocrime and bioterrorism scenes include blood, tissue, cloths containing biological fluids, swabs, water, soil, and aerosols. It is preferable that pathogens in such specimens are alive and kept in a steady state. Specimens may be stored for a prolonged period before analysis; therefore, it is important to understand the effect of the storage conditions on the pathogens contained within the specimens. In this study, we prepared blood and bloodstain specimens containing Gram-negative or -positive bacteria, stored the samples for 482 days under various conditions, and measured viable bacterial counts and total bacterial contents in the samples. Viable bacteria were preserved well in the samples stored at -30 and -80 °C, but were diminished or undetectable in the samples stored at 4 °C and room temperature. The total bacterial content was maintained in the blood samples stored at -30 and -80 °C and in the bloodstain samples stored under all temperature conditions, but decreased in the blood samples stored at 4 °C and room temperature. This study showed that the storage conditions affected viable bacteria and bacterial DNA and that freezing and drying were significant for their long-term storage. We provide important information for the storage of microbial forensic specimens.

  1. Real-time quantification of viable bacteria in liquid medium using infrared thermography

    Science.gov (United States)

    Salaimeh, Ahmad A.; Campion, Jeffrey J.; Gharaibeh, Belal Y.; Evans, Martin E.; Saito, Kozo

    2011-11-01

    Quantifying viable bacteria in liquids is important in environmental, food processing, manufacturing, and medical applications. Since vegetative bacteria generate heat as a result of biochemical reactions associated with cellular functions, thermal sensing techniques, including infrared thermography (IRT), have been used to detect viable cells in biologic samples. We developed a novel method that extends the dynamic range and improves the sensitivity of bacterial quantification by IRT. The approach uses IRT video, thermodynamics laws, and heat transfer mechanisms to directly measure, in real-time, the amount of energy lost as heat from the surface of a liquid sample containing bacteria when the specimen cools to a lower temperature over 2 min. We show that the Energy Content ( EC) of liquid media containing as few as 120 colony-forming units (CFU) of Escherichia coli per ml was significantly higher than that of sterile media ( P < 0.0001), and that EC and viable counts were strongly positively correlated ( r = 0.986) over a range of 120 to approximately 5 × 10 8 CFU/ml. Our IRT approach is a unique non-contact method that provides real-time bacterial enumeration over a wide dynamic range without the need for sample concentration, modification, or destruction. The approach could be adapted to quantify other living cells in a liquid milieu and has the potential for automation and high throughput.

  2. The importance of the viable but non-culturable state in human bacterial pathogens

    Directory of Open Access Journals (Sweden)

    Laam eLi

    2014-06-01

    Full Text Available Many bacterial species have been found to exist in a viable but non-culturable (VBNC state since its discovery in 1982. VBNC cells are characterized by a loss of culturability on routine agar, which impairs their detection by conventional plate count techniques. This leads to an underestimation of total viable cells in environmental or clinical samples, and thus poses a risk to public health. In this review, we present recent findings on the VBNC state of human bacterial pathogens. The characteristics of VBNC cells, including the similarities and differences to viable, culturable cells and dead cells, and different detection methods are discussed. Exposure to various stresses can induce the VBNC state, and VBNC cells may be resuscitated back to culturable cells under suitable stimuli. The conditions that trigger the induction of the VBNC state and resuscitation from it are summarized and the mechanisms underlying these two processes are discussed. Last but not least, the significance of VBNC cells and their potential influence on human health are also reviewed.

  3. 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.

  4. 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...

  5. Growth of Listeria monocytogenes in Salmon Roe - a kinetic analysis

    Science.gov (United States)

    The objective of this study was to investigate the growth kinetics of Listeria monocytogenes in unsalted and salted (3%) salmon roe. Growth curves, developed using inoculated samples incubated at constant temperatures between 5 and 30 degrees C, were analyzed by curve-fitting to the Huang and Baran...

  6. LISTERIA MONOCYTOGENES IN THE CONTEXT OF THE NEW COMMUNITY REGULATIONS

    Directory of Open Access Journals (Sweden)

    A. Bragagnolo

    2008-02-01

    Full Text Available In recent years in the countries of the European Union have occurred profound and radical changes regarding the safety and hygiene of foodstuffs. The aim of this work is to highlight the significant changes made by the recent legislation in the control of Listeria monocytogenes.

  7. Studies on the risk assessment of Listeria monocytogenes

    NARCIS (Netherlands)

    Notermans, S.; Dufrenne, J.; Teunis, P.; Chackraborty, T.

    1998-01-01

    Humans are frequently exposed to Listeria monocytogenes, and high numbers may be ingested during consumption of certain types of food. However, epidemiological investigations show that listeriosis is a rare disease. Risk assessment studies using an animal mouse model indicate that almost all L. mono

  8. 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

  9. Neonatal infection with Listeria monocytogenes: Rare, but serious

    NARCIS (Netherlands)

    Van Stuijvenberg, M.; Spanjaard, L.; Bergman, K.A.

    2006-01-01

    Between 1993 and 2003, three infants, two girls and a boy, were found to have an invasive infection with Listeria monocytogenes. They received intensive care including respiratory and circulatory support, antibiotics, and treatment of the neurological complications when possible. One of the girls

  10. Listeria monocytogenes and hemolytic Listeria innocua in poultry.

    Science.gov (United States)

    Milillo, S R; Stout, J C; Hanning, I B; Clement, A; Fortes, E D; den Bakker, H C; Wiedmann, M; Ricke, S C

    2012-09-01

    Listeria monocytogenes is a ubiquitous, saprophytic, Gram-positive bacterium and occasional food-borne pathogen, often associated with ready-to-eat meat products. Because of the increased consumer interest in organic, all natural, and free range poultry products, it is important to understand L. monocytogenes in the context of such systems. Pasture-reared poultry were surveyed over the course of two 8-wk rearing periods. Cecal, soil, and grass samples were collected for Listeria isolation and characterization. Seven of 399 cecal samples (or 1.75%) were Listeria-positive. All positive cecal samples were obtained from broilers sampled at 2 wk of age. Grass and soil samples were collected from the pasture both before and after introduction of the poultry. Environmental samples collected after introduction of poultry were significantly more likely to contain Listeria (P Listeria, sigB allelic typing, and hlyA PCR tests found that both L. monocytogenes and L. innocua, including hemolytic L. innocua, were recovered from the cecal and environmental (grass/soil) samples. The sigB allelic typing also revealed that (1) positive samples could be composed of 2 or more allelic types; (2) allelic types found in cecal samples could also be found in the environment; and (3) allelic types could persist through the 2 rearing periods. Our data indicate that both pasture-reared poultry and their environment can be contaminated with L. monocytogenes and hemolytic L. innocua.

  11. Presence of Listeria monocytogenes in silage products of Shahrekord city

    Directory of Open Access Journals (Sweden)

    Ali Sharifzadeh

    2015-06-01

    Full Text Available Objective: To investigate the presence of Listeria monocytogenes in the silage samples. Methods: Silage samples obtained from 150 different farms in Shahrekord city (Iran and after DNA extraction, all samples were analyzed by PCR technique using one pair of primers for presence of this pathogen. The amplified products were detected on 1.5% agarose gel electrophoresis. Results: Listeria monocytogenes was isolated in 4 (2% of the 150 samples. The detection of this bacterium from silage samples in Shahrekord city indicated that these products could create a serious risk in public health of animal and human. The findings showed that in positive silage samples for Listeria monocytogenes, the pH value was about five and it was due to bacterial activity in these products. Conclusions: The quality of silage and hygiene parameters and good herd health management play an important role in the microbiological quality of herd and farm. Considering the high specificity and sensitivity of the employed PCR technique, it is recommended to be useful technique for identification of Listeria monocytogenes.

  12. Listeria monocytogenes : the nature, public health aspects and ...

    African Journals Online (AJOL)

    Animal Production Research Advances ... New food borne infectious diseases have continued to emerge world over in the food industries. ... Its' public health importance cannot be over emphasized as L. monocytogenes causes huge economic ... It is therefore, suggested that proper control strategies, good quality control ...

  13. Quantifying strain variability in modeling growth of Listeria monocytogenes

    NARCIS (Netherlands)

    Aryani, D.; Besten, den H.M.W.; Hazeleger, W.C.; Zwietering, M.H.

    2015-01-01

    Prediction of microbial growth kinetics can differ from the actual behavior of the target microorganisms. In the present study, the impact of strain variability on maximum specific growth rate (µmax) (h- 1) was quantified using twenty Listeria monocytogenes strains. The µmax was determined as functi

  14. Genome sequesnce of lineage III Listeria monocytogenes strain HCC23

    Science.gov (United States)

    More than 98% of reported human listeriosis cases are caused by Listeria monocytogenes serotypes within lineages I and II. Serotypes within lineage III (4a and 4c) are commonly isolated from environmental and food specimens. We report the first complete genome sequence of a lineage III isolate, HCC2...

  15. Inhibition of Listeria monocytogenes by fatty acids and monoglycerides.

    Science.gov (United States)

    Wang, L L; Johnson, E A

    1992-02-01

    Fatty acids and monoglycerides were evaluated in brain heart infusion broth and in milk for antimicrobial activity against the Scott A strain of Listeria monocytogenes. C12:0, C18:3, and glyceryl monolaurate (monolaurin) had the strongest activity in brain heart infusion broth and were bactericidal at 10 to 20 micrograms/ml, whereas potassium (K)-conjugated linoleic acids and C18:2 were bactericidal at 50 to 200 micrograms/ml. C14:0, C16:0, C18:0, C18:1, glyceryl monomyristate, and glyceryl monopalmitate were not inhibitory at 200 micrograms/ml. The bactericidal activity in brain heart infusion broth was higher at pH 5 than at pH 6. In whole milk and skim milk, K-conjugated linoleic acid was bacteriostatic and prolonged the lag phase especially at 4 degrees C. Monolaurin inactivated L. monocytogenes in skim milk at 4 degrees C, but was less inhibitory at 23 degrees C. Monolaurin did not inhibit L. monocytogenes in whole milk because of the higher fat content. Other fatty acids tested were not effective in whole or skim milk. Our results suggest that K-conjugated linoleic acids or monolaurin could be used as an inhibitory agent against L. monocytogenes in dairy foods.

  16. The Continuous Challenge of Characterizing the Foodborne Pathogen Listeria monocytogenes.

    Science.gov (United States)

    Camargo, Anderson Carlos; Woodward, Joshua John; Nero, Luís Augusto

    2016-08-01

    Listeria monocytogenes is an important foodborne pathogen commonly isolated from food processing environments and food products. This organism can multiply at refrigeration temperatures, form biofilms on different materials and under various conditions, resist a range of environmental stresses, and contaminate food products by cross-contamination. L. monocytogenes is recognized as the causative agent of listeriosis, a serious disease that affects mainly individuals from high-risk groups, such as pregnant women, newborns, the elderly, and immunocompromised individuals. Listeriosis can be considered a disease that has emerged along with changing eating habits and large-scale industrial food processing. This disease causes losses of billions of dollars every year with recalls of contaminated foods and patient medical treatment expenses. In addition to the immune status of the host and the infecting dose, the virulence potential of each strain is crucial for the development of disease symptoms. While many isolates are naturally virulent, other isolates are avirulent and unable to cause disease; this may vary according to the presence of molecular determinants associated with virulence. In the last decade, the characterization of genetic profiles through the use of molecular methods has helped track and demonstrate the genetic diversity among L. monocytogenes isolates obtained from various sources. The purposes of this review were to summarize the main methods used for isolation, identification, and typing of L. monocytogenes and also describe its most relevant virulence characteristics.

  17. 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

  18. Whole genome sequence-based serogrouping of Listeria monocytogenes isolates.

    Science.gov (United States)

    Hyden, Patrick; Pietzka, Ariane; Lennkh, Anna; Murer, Andrea; Springer, Burkhard; Blaschitz, Marion; Indra, Alexander; Huhulescu, Steliana; Allerberger, Franz; Ruppitsch, Werner; Sensen, Christoph W

    2016-10-10

    Whole genome sequencing (WGS) is currently becoming the method of choice for characterization of Listeria monocytogenes isolates in national reference laboratories (NRLs). WGS is superior with regards to accuracy, resolution and analysis speed in comparison to several other methods including serotyping, PCR, pulsed field gel electrophoresis (PFGE), multilocus sequence typing (MLST), multilocus variable number tandem repeat analysis (MLVA), and multivirulence-locus sequence typing (MVLST), which have been used thus far for the characterization of bacterial isolates (and are still important tools in reference laboratories today) to control and prevent listeriosis, one of the major sources of foodborne diseases for humans. Backward compatibility of WGS to former methods can be maintained by extraction of the respective information from WGS data. Serotyping was the first subtyping method for L. monocytogenes capable of differentiating 12 serovars and national reference laboratories still perform serotyping and PCR-based serogrouping as a first level classification method for Listeria monocytogenes surveillance. Whole genome sequence based core genome MLST analysis of a L. monocytogenes collection comprising 172 isolates spanning all 12 serotypes was performed for serogroup determination. These isolates clustered according to their serotypes and it was possible to group them either into the IIa, IIc, IVb or IIb clusters, respectively, which were generated by minimum spanning tree (MST) and neighbor joining (NJ) tree data analysis, demonstrating the power of the new approach. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  19. 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...

  20. Studies on the risk assessment of Listeria monocytogenes

    NARCIS (Netherlands)

    Notermans, S.; Dufrenne, J.; Teunis, P.; Chackraborty, T.

    1998-01-01

    Humans are frequently exposed to Listeria monocytogenes, and high numbers may be ingested during consumption of certain types of food. However, epidemiological investigations show that listeriosis is a rare disease. Risk assessment studies using an animal mouse model indicate that almost all L.

  1. Microbiological quality and safety of raw milk and soft cheese and detection of autochthonous lactic acid bacteria with antagonistic activity against Listeria monocytogenes, Salmonella Spp., and Staphylococcus aureus.

    Science.gov (United States)

    Ortolani, Maria Beatriz Tassinari; Yamazi, Anderson Keizo; Moraes, Paula Mendonça; Viçosa, Gabriela Nogueira; Nero, Luís Augusto

    2010-02-01

    This study aimed to characterize the microbiological quality and safety of raw milk and soft cheese, verifying possible associations between microbial populations, and the detection of lactic acid bacteria (LAB) with antagonistic activity against foodborne pathogens. Raw milk (n = 36) and soft cheese (n = 18) samples were collected and submitted for the analysis of mesophilic aerobes, total coliforms, Escherichia coli, LAB, coagulase-positive Staphylococcus (CPS), Listeria monocytogenes, and Salmonella spp. In all, 389 LAB isolates were randomly selected and submitted for antagonistic tests against L. monocytogenes, St. aureus, Salmonella Typhimurium, and Lactobacillus sakei. The samples presented high counts of mesophilic aerobes, total coliforms, and LAB, and also high and significant correlation indices between these populations. Low levels of CPS and E. coli were observed, as well as an absence of Salmonella spp. and L. monocytogenes. A substantial portion of the analyzed samples presented LAB cultures with antagonistic activity, but not against Salmonella Typhimurium. The obtained results indicate the antimicrobial potential of the autochthonous microbiota of raw milk and soft cheese. Despite the spoilage potential, the LAB present in the studied food products can be isolated and properly characterized as antagonistic cultures, to be used in bioconservation studies for pathogen control in foods.

  2. Behaviour of Listeria monocytogenes and Escherichia coli O157:H7 during the cheese making of traditional raw-milk cheeses from Italian Alps

    Directory of Open Access Journals (Sweden)

    Elena Cosciani-Cunico

    2015-09-01

    Full Text Available The behaviour of Listeria monocytogenes and Escherichia coli O157:H7 was studied during the manufacture and ripening of two traditional Italian Alps cheeses. Each cheese type was manufactured in a pilot plan from raw cow milk (without the addition of starter cultures artificially inoculated with L. monocytogenes and E. coli O157:H7 to a final concentration of about 4 log CFU/mL. The pathogens were enumerated throughout the cheese making and ripening processes to study their behaviour. When the milk was inoculated with 4 Log CFU/mL, the pathogens counts increased in the first time during the manufacturing process and then remained constant, until the end of ripening, or decreased significantly. Results indicate that the environment and nature of food borne pathogens affected the concentration of the bacteria during the manufacturing and ripening process. Thus, the presence of low cells numbers of L. monocytogenes and E. coli O157:H7 in milk destined for the production of raw milk cheeses characterized by a cooking of the curd less than 48°C can constitute a hazard for the consumer.

  3. Efficacies of nisin A and nisin V semipurified preparations alone and in combination with plant essential oils for controlling Listeria monocytogenes.

    Science.gov (United States)

    Field, Des; Daly, Karen; O'Connor, Paula M; Cotter, Paul D; Hill, Colin; Ross, R Paul

    2015-04-01

    The food-borne pathogenic bacterium Listeria is known for relatively low morbidity and high mortality rates, reaching up to 25 to 30%. Listeria is a hardy organism, and its control in foods represents a significant challenge. Many naturally occurring compounds, including the bacteriocin nisin and a number of plant essential oils, have been widely studied and are reported to be effective as antimicrobial agents against spoilage and pathogenic microorganisms. The aim of this study was to investigate the ability of semipurified preparations (SPP) containing either nisin A or an enhanced bioengineered derivative, nisin V, alone and in combination with low concentrations of the essential oils thymol, carvacrol, and trans-cinnamaldehyde, to control Listeria monocytogenes in both laboratory media and model food systems. Combinations of nisin V-containing SPP (25 μg/ml) with thymol (0.02%), carvacrol (0.02%), or cinnamaldehyde (0.02%) produced a significantly longer lag phase than any of the essential oil-nisin A combinations. In addition, the log reduction in cell counts achieved by the nisin V-carvacrol or nisin V-cinnamaldehyde combinations was twice that of the equivalent nisin A-essential oil treatment. Significantly, this enhanced activity was validated in model food systems against L. monocytogenes strains of food origin. We conclude that the fermentate form of nisin V in combination with carvacrol and cinnamaldehyde offers significant advantages as a novel, natural, and effective means to enhance food safety by inhibiting food-borne pathogens such as L. monocytogenes.

  4. Análisis de la resistencia inmune en un modelo murino experimental alimentado con dietas lipídicas e infectado con Listeria monocytogenes Analysis of the immune resistance in an experimental murine model fed dietary lipids and infected with Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    M.ª A. Puertollano

    2004-11-01

    Full Text Available Algunas dietas lipídicas están implicadas en la reducción de ciertas funciones inmunes. Sin embargo, la acción inmunosupresora de estas dietas puede tener efectos adversos sobre la resistencia inmune del individuo frente a enfermedades de naturaleza infecciosa. En el presente estudio tratamos de valorar el estado inmune de ratones alimentados con dietas lipídicas e infectados experimentalmente con una cepa virulenta de Listeria monocytogenes. Ratones de la raza Balb/c fueron divididos en cuatro grupos alimentados cada uno de ellos con su respectiva dieta: dieta baja en lípidos (control, 2,5%, dieta rica en aceite de oliva (AO, 20%, dieta rica en aceite de pescado (AP, 20% y dieta rica aceite de coco (AC, 20%. Los animales fueron alimentados durante un mes y posteriormente infectados con L. monocytogenes por vía endovenosa. Los resultados han mostrado una reducción de la supervivencia en animales alimentados con AP, así como un incremento significativo en el número de bacterias viables aisladas a partir de bazo. Además hemos podido observar un aumento de la capacidad bactericida de células peritoneales procedentes de ratones alimentados con AO, aunque la invasividad de L. monocytogenes en este grupo fue mayor que en el resto. Finalmente, una reducción significativa de la linfoproliferación fue observada en el grupo alimentado con AP, mientras que la actividad de células natural killer (NK no se ha visto modificada. Estos resultados indican que dietas lipídicas constituidas por ácidos grasos poliinsaturados de la serie n-3 reducen la resistencia inmune de los ratones, mientras que una dieta constituida por AO no produce un efecto inmusupresor tan relevante y por consiguiente no reduce drásticamente la resistencia inmune siendo más eficiente en la eliminación de L. monocytogenes.Several dietary lipids are capable of exerting an immunosupressor effect. This action may have undiserable effects on the host immune resistance to

  5. Reduction of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes with electrolyzed oxidizing water on inoculated hass avocados (Persea americana var. Hass).

    Science.gov (United States)

    Rodríguez-Garcia, O; González-Romero, V M; Fernández-Escartín, E

    2011-09-01

    This study was intended to evaluate the bactericidal effect of electrolyzed oxidizing water (EOW) and chlorinated water on populations of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes inoculated on avocados (Persea americana var. Hass). In the first experiment, inoculated avocados were treated with a water wash applied by spraying tap water containing 1 mg/liter free chlorine for 15 s (WW); WW treatment and then spraying sodium hypochlorite in water containing 75 mg/liter free chlorine for 15 s (Cl75); WW treatment and then spraying alkaline EOW for 30 s (AkEW) and then spraying acid EOW (AcEW) for 15 s; and spraying AkEW and then AcEW. In another experiment, the inoculated avocados were treated by spraying AkEW and then AcEW for 15, 30, 60, or 90 s. All three pathogen populations were lowered between 3.6 and 3.8 log cycles after WW treatment. The application of Cl75 did not produce any further reduction in counts, whereas AkEW and then AcEW treatment resulted in significantly lower bacterial counts for L. monocytogenes and E. coli O157:H7 but not for Salmonella. Treatments with AkEW and then AcEW produced a significant decrease in L. monocytogenes, Salmonella, and E. coli O157:H7 populations, with estimated log reductions of 3.9 to 5.2, 5.1 to 5.9, and 4.2 to 4.9 log CFU/cm², respectively. Spraying AcEW for more than 15 s did not produce any further decrease in counts of Salmonella or E. coli O157:H7, whereas L. monocytogenes counts were significantly lower after spraying AcEW for 60 s. Applying AkEW and then AcEW for 15 or 30 s seems to be an effective alternative to reduce bacterial pathogens on avocado surfaces.

  6. The right to count does not always count

    DEFF Research Database (Denmark)

    Sodemann, Morten

    2013-01-01

    The best prescription against illness is learning to read and to count. People who are unable to count have a harder time learning to read. People who have difficulty counting make poorer decisions, are less able to combine information and are less likely to have a strategy for life...

  7. 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%).

  8. Differential fluorescent staining of Listeria monocytogenes and a whey food soil for quantitative analysis of surface hygiene.

    Science.gov (United States)

    Whitehead, Kathryn A; Benson, Paul; Verran, Joanna

    2009-09-30

    The accurate monitoring of surface cleanliness in terms of bacterial contamination is usually carried out using methods such as plate counts or replica plating. However these methods take at least eighteen hours to obtain results and do not determine the presence or amount of residual organic material on a surface, which may interfere with cleaning and disinfection. This work describes the application of fluorescent stains to cells (Listeria monocytogenes) and food soil (solubilized whey) to optimize a dual staining method that can be used in the quantitative analysis of surface cleanability. Seven different stains were tested at a range of concentrations (0.3%-0.001 mg/ml) and application methods. The best stain combination for differential staining of L. monocytogenes and whey food soil was 0.1 mg/ml rhodamine B with 0.1 g/ml DAPI. Differential staining of the cells and soil occurred regardless of the application method. This method has been successfully used to demonstrate the hygienic status of surfaces in an industrial situation. This novel work enables quantitative assessment of soils and cells on surfaces.

  9. CalCOFI Egg Counts

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Fish egg counts and standardized counts for eggs captured in CalCOFI icthyoplankton nets (primarily vertical [Calvet or Pairovet], oblique [bongo or ring nets], and...

  10. High Red Blood Cell Count

    Science.gov (United States)

    Symptoms High red blood cell count By Mayo Clinic Staff A high red blood cell count is an increase in oxygen-carrying cells in your bloodstream. Red blood cells transport oxygen from your lungs to tissues throughout ...

  11. Counting and Topological Order

    Institute of Scientific and Technical Information of China (English)

    陈阳军

    1997-01-01

    The counting method is a simple and efficient method for processing linear recursive datalog queries.Its time complexity is bounded by O(n,e)where n and e denote the numbers the numbers of nodes and edges,respectively,in the graph representing the input.relations.In this paper,the concepts of heritage appearance function and heritage selection function are introduced,and an evaluation algorithm based on the computation of such functions in topological order is developed .This new algorithm requires only linear time in the case of non-cyclic data.

  12. Natural Antibacterial Activity of Thai Red Curry Paste in Coconut Milk based Curry; Kang-Kati, Model on Salmonella sp. and Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Chuchod SAPABGUY

    2014-10-01

    Full Text Available Since 2006, Salmonella sp. and Listeria monocytogenes outbreaks have occurred frequently in a variety food types all over the world. Thai red curry paste is composed of 7 herbs which have been investigated for their antimicrobial activity in different independent laboratories. The investigation aimed to study the antibacterial activity of Thai red curry paste in a coconut milk based curry; Kang-Kati, as a real food model against S. enteric Enteritidis (human and L. monocytogenes 10403S. The standard plate count method as CFU/ml was used to evaluate the Thai red curry paste’s in vitro antibacterial activity every hour for 6 h at room temperature. The Thai red curry paste was extracted according to the traditional Thai home cooking as Kang-Kati. The log CFU/ml of S. enteric Enteritidis (human level was significantly lower (P < 0.05 in the Kang-Kati model than in nutrient broth (NB as control at only 3rd and 4th h; 3rd h; 5.53±0.027 and 5.65±0.019, and at 4th h; 5.62±0.07 and 5.80±0.03 log CFU/ml, respectively. While the log CFU/ml of the L. monocytogenes level was also significantly lower (P < 0.05 in Kang-Kati than in NB at 3rd and 4th h; 3rd h; 5.49±0.01 and 5.61±0.02, and at 4th h 5.63±0.02 and 5.70±0.04 for log CFU/ml, respectively. The Thai red curry paste in Kang-Kati as a real food model showed promising natural antibacterial activity against the food borne pathogens, enteric Enteritidis (human and L. monocytogenes 104003S.

  13. Listeria monocytogenes survival of UV-C radiation is enhanced by presence of sodium chloride, organic food material and by bacterial biofilm formation.

    Science.gov (United States)

    Bernbom, N; Vogel, B F; Gram, L

    2011-05-14

    The bactericidal effect on food processing surfaces of ceiling-mounted UV-C light (wavelength 254 nm) was determined in a fish smoke house after the routine cleaning and disinfection procedure. The total aerobic counts were reduced during UV-C light exposure (48 h) and the number of Listeria monocytogenes positive samples went from 30 (of 68) before exposure to 8 (of 68). We therefore in a laboratory model determined the L. monocytogenes reduction kinetics by UV-C light with the purpose of evaluating the influence of food production environmental variables, such as presence of NaCl, organic material and the time L. monocytogenes was allowed to adhere to steel before exposure. L. monocytogenes grown and attached in tryptone soy broth (TSB) with glucose were rapidly killed (after 2 min) by UV-C light. However, bacteria grown and adhered in TSB with glucose and 5% NaCl were more resistant and numbers declined with 4-5 log units during exposure of 8-10 min. Bacteria grown in juice prepared from cold-smoked salmon were protected and numbers were reduced with 2-3 log when UV-C light was used immediately after attachment whereas numbers did not change at all if bacteria had been allowed to form a biofilm for 7 days before exposure. It is not known if this enhanced survival is due to physiological changes in the attached bacterial cells, a physical protection of the cells in the food matrix or a combination. In conclusion, we demonstrate that UV-C light is a useful extra bacteriocidal step and that it, as all disinfecting procedures, is hampered by the presence of organic material.

  14. Phantom crossing in viable $f(R)$ theories

    CERN Document Server

    Bamba, Kazuharu; Lee, Chung-Chi

    2011-01-01

    We review the equation of state for dark energy in modified gravity theories. In particular, we summarize the generic feature of the phantom divide crossing in the past and future in viable $f(R)$ gravity models.

  15. 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.

  16. Characterization of Listeria monocytogenes from three countries and antibiotic resistance differences among countries and Listeria monocytogenes serogroups.

    Science.gov (United States)

    Obaidat, M M; Bani Salman, A E; Lafi, S Q; Al-Abboodi, A R

    2015-06-01

    A total of 104 Listeria monocytogenes isolates from 330 fish samples from three countries were characterized by multiplex PCR for serogrouping and virulence markers determination and tested for antibiotics resistance. A 53·8% of the isolates belonged to serogroup 1/2a, 3a; 32% belonged to 1/2b, 3b, 7; 14·4% belonged to 4b, 4d, 4e and 1% belonged to 1/2c, 3c. All isolates exhibited resistance to at least one antibiotic but the resistance rates varied among countries. The isolates exhibited high resistance to penicillin, rifampicin, clindamycin, erythromycin and tetracycline, but low resistance to amoxicillin-clavulanic acid, streptomycin, sulfamethoxazole-trimethoprim, gentamicin, chloramphenicol and kanamycin. When comparing countries, the resistance rate for rifampicin, clindamycin, erythromycin, tetracycline, amoxicillin-clavulanic acid varied among countries. When comparing serogroup, 1/2a, 3a exhibited the highest resistance to clindamycin, erythromycin, tetracycline and vancomycin while serogroup 4b, 4d, 4e exhibited the highest resistance to amoxicillin-clavulanic acid. All isolates carried inlA, inlC, inlJ and lmo2672. Listeriolysin S was carried by 42 and 30% of 4b and 1/2b isolates respectively. Significance and impact of the study: This is one of few studies to correlate antibiotic resistance with Listeria monocytogenes serogroups. The study also compared the antibiotic resistance and serogroups of L. monocytogenes isolates from three countries in one single study. The findings of this study will be helpful in improving data on the antibiotics resistance of L. monocytogenes in developing countries and enriches the epidemiological and public health studies of L. monocytogenes. © 2015 The Society for Applied Microbiology.

  17. Effect of octenidine hydrochloride on planktonic cells and biofilms of Listeria monocytogenes.

    Science.gov (United States)

    Amalaradjou, Mary Anne Roshni; Norris, Carol E; Venkitanarayanan, Kumar

    2009-06-01

    Listeria monocytogenes is a food-borne pathogen capable of forming biofilms and persisting in food processing environments for extended periods of time, thereby potentially contaminating foods. The efficacy of octenidine hydrochloride (OH) for inactivating planktonic cells and preformed biofilms of L. monocytogenes was investigated at 37, 21, 8, and 4 degrees C in the presence and absence of organic matter (rehydrated nonfat dry milk). OH rapidly killed planktonic cells and biofilms of L. monocytogenes at all four temperatures. Moreover, OH was equally effective in killing L. monocytogenes biofilms on polystyrene and stainless steel matrices in the presence and absence of organic matter. The results underscore OH's ability to prevent establishment of L. monocytogenes biofilms by rapidly killing planktonic cells and to eliminate preformed biofilms, thus suggesting that it could be used as a disinfectant to prevent L. monocytogenes from persisting in food processing environments.

  18. Inhibition of listeriolysin O oligomerization by lutein prevents Listeria monocytogenes infection.

    Science.gov (United States)

    Liu, Bowen; Teng, Zihao; Wang, Jianfeng; Lu, Gejin; Deng, Xuming; Li, Li

    2017-01-01

    The foodborne pathogenic bacterial species Listeria monocytogenes (L. monocytogenes) has caused incalculable damages to public health, and its successful infection requires various virulence factors, including Listeriolysin O (LLO). By forming pores in phagosomal membranes and even in some organelles, LLO plays an indispensable role in the ability of L. monocytogenes to escape from host immune attacks. Because of its critical role, LLO offers an appropriate therapeutic target against L. monocytogenes infection. Here, lutein, a natural small molecule existing widely in fruits and vegetables, is demonstrated as an effective inhibitor of LLO that works by blocking its oligomerization during invasion without showing significant bacteriostatic activity. Further assays applying lutein in cell culture models of invasion and in animal models showed that lutein could effectively inhibit L. monocytogenes infection. Overall, our results indicate that lutein may represent a promising and novel therapeutic agent against L. monocytogenes infection. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Detection of Listeria monocytogenes in CSF from Three Patients with Meningoencephalitis by Next-Generation Sequencing

    Science.gov (United States)

    Yao, Ming; Zhou, Jiali; Zhu, Yicheng; Zhang, Yinxin; Lv, Xia; Sun, Ruixue; Shen, Ao; Ren, Haitao; Cui, Liying

    2016-01-01

    Background and Purpose Encephalitis caused by Listeria monocytogenes (L. monocytogenes) is rare but sometimes fatal. Early diagnosis is difficult using routine cerebrospinal fluid (CSF) tests, while next-generation sequencing (NGS) is increasingly being used for the detection and characterization of pathogens. Methods This study set up and applied unbiased NGS to detect L. monocytogenes in CSF collected from three cases of clinically suspected listeria meningoencephalitis. Results Three cases of patients with acute/subacute meningoencephalitis are reported. Magnetic resonance imaging and blood cultures led to a suspected diagnosis of L. monocytogenes, while the CSF cultures were negative. Unbiased NGS of CSF identified and sequenced reads corresponding to L. monocytogenes in all three cases. Conclusions This is the first report highlighting the feasibility of applying NGS of CSF as a diagnostic method for central nervous system (CNS) L. monocytogenes infection. Routine application of this technology in clinical microbiology will significantly improve diagnostic methods for CNS infectious diseases.

  20. 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

  1. Oral Immunization with Recombinant Listeria monocytogenes Controls Virus Load after Vaginal Challenge with Feline Immunodeficiency Virus

    OpenAIRE

    Stevens, Rosemary; Howard, Kristina E.; Nordone, Sushila; Burkhard, MaryJo; Dean, Gregg A

    2004-01-01

    Recombinant Listeria monocytogenes has many attractive characteristics as a vaccine vector against human immunodeficiency virus (HIV). Wild-type and attenuated Listeria strains expressing HIV Gag have been shown to induce long-lived mucosal and systemic T-cell responses in mice. Using the feline immunodeficiency virus (FIV) model of HIV we evaluated recombinant L. monocytogenes in a challenge system. Five cats were immunized with recombinant L. monocytogenes that expresses the FIV Gag and del...

  2. Lineage specific recombination rates and microevolution in Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    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

  3. Inflammasome-Mediated Inhibition of Listeria monocytogenes-Stimulated Immunity Is Independent of Myelomonocytic Function

    Science.gov (United States)

    Williams, Cassandra R.; Dustin, Michael L.; Sauer, John-Demian

    2013-01-01

    Activation of the Nlrc4 inflammasome results in the secretion of IL-1β and IL-18 through caspase-1 and induction of pyroptosis. L. monocytogenes engineered to activate Nlrc4 by expression of Legionella pneumophilia flagellin (L. monocytogenes L.p.FlaA) are less immunogenic for CD8+ T cell responses than wt L. monocytogenes. It is also known that IL-1β orchestrates recruitment of myelomonocytic cells (MMC), which have been shown to interfere with T cell-dendritic cells (DC) interactions in splenic white pulp (WP), limiting T cell priming and protective immunity. We have further analyzed the role of MMCs in the immunogenicity of L. monocytogenes L.p.FlaA. We confirmed that MMCs infiltrate the WP between 24–48 hours in response to wt L. monocytogenes infection and that depletion of MMCs enhances CD8+ T cell priming and protective memory. L. monocytogenes L.p.FlaA elicited accelerated recruitment of MMCs into the WP. While MMCs contribute to control of L. monocytogenes L.p.FlaA, MMC depletion did not increase immunogenicity of L.p.FlaA expressing strains. There was a significant decrease in L. monocytogenes L.p.FlaA in CD8α+ DCs independent of MMCs. These findings suggest that limiting inflammasome activation is important for bacterial accumulation in CD8α+ DCs, which are known to be critical for T cell response to L. monocytogenes. PMID:24349458

  4. 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...

  5. 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.

  6. 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.

  7. Spontaneous bacterial peritonitis due to Listeria monocytogenes: importance of enrichment culture.

    Science.gov (United States)

    Jayasinghe, Saroj; Connor, Martin; Donaldson, Shona; Austin, Hannah; Foster, Adele

    2010-09-01

    A case of Listeria monocytogenes induced spontaneous bacterial peritonitis (SBP) is reported in a patient with primary biliary cirrhosis. It is an indolent illness and may not show a neutrophil reaction in peritoneal fluid. Enrichment broth was required to isolate L monocytogenes in the patient. This is not routinely used in the UK and therefore isolates may be missed. L monocytogenes remains sensitive to ampicillin, penicillin and gentamicin, but is resistant to cephalosporin antibiotics. The rising incidence of listeriosis in the population suggests that the incidence of SBP from L monocytogenes is likely to increase.

  8. Inflammasome-mediated inhibition of Listeria monocytogenes-stimulated immunity is independent of myelomonocytic function.

    Directory of Open Access Journals (Sweden)

    Cassandra R Williams

    Full Text Available Activation of the Nlrc4 inflammasome results in the secretion of IL-1β and IL-18 through caspase-1 and induction of pyroptosis. L. monocytogenes engineered to activate Nlrc4 by expression of Legionella pneumophilia flagellin (L. monocytogenes L.p.FlaA are less immunogenic for CD8(+ T cell responses than wt L. monocytogenes. It is also known that IL-1β orchestrates recruitment of myelomonocytic cells (MMC, which have been shown to interfere with T cell-dendritic cells (DC interactions in splenic white pulp (WP, limiting T cell priming and protective immunity. We have further analyzed the role of MMCs in the immunogenicity of L. monocytogenes L.p.FlaA. We confirmed that MMCs infiltrate the WP between 24-48 hours in response to wt L. monocytogenes infection and that depletion of MMCs enhances CD8(+ T cell priming and protective memory. L. monocytogenes L.p.FlaA elicited accelerated recruitment of MMCs into the WP. While MMCs contribute to control of L. monocytogenes L.p.FlaA, MMC depletion did not increase immunogenicity of L.p.FlaA expressing strains. There was a significant decrease in L. monocytogenes L.p.FlaA in CD8α(+ DCs independent of MMCs. These findings suggest that limiting inflammasome activation is important for bacterial accumulation in CD8α(+ DCs, which are known to be critical for T cell response to L. monocytogenes.

  9. Counting coalescent histories.

    Science.gov (United States)

    Rosenberg, Noah A

    2007-04-01

    Given a species tree and a gene tree, a valid coalescent history is a list of the branches of the species tree on which coalescences in the gene tree take place. I develop a recursion for the number of valid coalescent histories that exist for an arbitrary gene tree/species tree pair, when one gene lineage is studied per species. The result is obtained by defining a concept of m-extended coalescent histories, enumerating and counting these histories, and taking the special case of m = 1. As a sum over valid coalescent histories appears in a formula for the probability that a random gene tree evolving along the branches of a fixed species tree has a specified labeled topology, the enumeration of valid coalescent histories can considerably reduce the effort required for evaluating this formula.

  10. Oscillations in counting statistics

    CERN Document Server

    Wilk, Grzegorz

    2016-01-01

    The very large transverse momenta and large multiplicities available in present LHC experiments on pp collisions allow a much closer look at the corresponding distributions. Some time ago we discussed a possible physical meaning of apparent log-periodic oscillations showing up in p_T distributions (suggesting that the exponent of the observed power-like behavior is complex). In this talk we concentrate on another example of oscillations, this time connected with multiplicity distributions P(N). We argue that some combinations of the experimentally measured values of P(N) (satisfying the recurrence relations used in the description of cascade-stochastic processes in quantum optics) exhibit distinct oscillatory behavior, not observed in the usual Negative Binomial Distributions used to fit data. These oscillations provide yet another example of oscillations seen in counting statistics in many different, apparently very disparate branches of physics further demonstrating the universality of this phenomenon.

  11. PELÍCULA ANTIMICROBIANA A BASE DE PROTEÍNA DE SUERO LÁCTEO, INCORPORADA CON BACTERIAS LÁCTICAS COMO CONTROLADOR DE Listeria monocytogenes, APLICADA SOBRE SALMÓN AHUMADO FILM ANTIMICROBIAL BASED WHEY PROTEIN, LACTIC ACID BACTERIA INCORPORATED AS CONTROLLER Listeria monocytogenes APPLIED TO SMOKED SALMON

    Directory of Open Access Journals (Sweden)

    DEYCI RODRÍGUEZ

    2009-12-01

    Full Text Available El concentrado de proteína de suero lácteo (CPS posee propiedades funcionales apropiadas para la elaboración de películas biopreservantes, siendo factible la incorporación de bacterias ácido lácticas (BAL productoras de sustancias tipo bacteriocina (STB y así, lograr un efecto controlador sobre Listeria monocytogenes al ser utilizada como cobertura sobre salmón ahumado. Las condiciones para la formación de la película fueron: CPS 12% p/v, glicerol 18% v/v, pH en solución formadora de película 7,0 y 8,0, y secado a 30°C por 16 horas. La actividad inhibitoria de la película incorporada con las cepas lácticas fue evaluada usando el método de difusión frente a un césped de L. monocytogenes y mediante el recuento en placa, obteniendo: la combinación de dos cepas BAL aumentó la actividad controladora sobre L. monocytogenes logrando reducir hasta 2,1 ciclos logarítmicos el crecimiento de este patógeno, bajo condiciones de refrigeración durante 15 días.The Whey protein concentrated (WPC has functional properties suitable for developing films biopreservantes. Thanks to the functional properties of its components, was feasible the incorporation of lactic acid bacteria (LAB producing substances type bacteriocins (STB and thus achieve and effective control Listeria monocytogenes to be applied on smoked salmon. The conditions for the formation of the film were: CPS 12% w/v, glycerol 18% v/v, pH of film-forming solution 7.0 and 8.0, and dried at 30°C for 16 hours. The study of inhibitory activity of the film incorporated with lactic strains was evaluated using the diffusion method against a lawn of L. monocytogenes and by plate counting, getting the combination BAL-A + B, increases the activity of controlling L. monocytogenes achieving 2.1 log units to reduce the growth of this pathogen under refrigeration for 15 days.

  12. 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

  13. 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, <0.3 to 1.2 log MPN/100 ml). On bell pepper analyzed during the study, populations (median) of APC, coliforms, and molds were 5.4, 3.6, and 5.8 log CFU per 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.

  14. Bacteriocin like substance production by Carnobacterium piscicola in a continuous system with three culture broths. Study of antagonism against Listeria monocytogenes on vacuum packaged salmon Produção de substâncias semelhantes à bacteriocinas por C. piscicola em um sistema contínuo com três meios de cultura e seu antagonismo contra L. monocytogenes em salmão embalado a vácuo

    Directory of Open Access Journals (Sweden)

    Renate P. Schöbitz

    2006-03-01

    Full Text Available Three culture media were studied for the bacteriocin like substance (BLS production from Carnobacterium piscicola L 103 in a batch and continuous culture system. The efficacy of the antagonistic substance against Listeria monocytogenes was tested on vacuum packaged salmon. BLS was produced in a 1.0 L bioreactor by batch and continuous culture using D-MRS, mod. D-MRS and APT as nutrient broths. Salmon fillets were inoculated with BLS (200 AU mL-1 and 800 AU mL-1 and 8.0 x 10¹ cfu cm-2 of L. monocytogenes and stored at 4ºC. The growth of L. monocytogenes was determined every 5 days during 15 days. After 12 h of batch culture the stationary growth phase of C. piscicola L 103 started, with a BLS activity of 800 AU mL-1 in D-MRS and mod. D-MRS broth, and of 400 AU mL-1 in APT broth. During continuous culture BLS activity increased to 6400 AU mL-1 in both types of MRS broths, while in APT the activity decreased to 50 AU mL-1, indicating a clear advantage of the first two culture media and also of the continuous culture system. BLS had a bacteriostatic effect on L. monocytogenes when inoculated on salmon, with counts of 6.0 x 10³ cfu cm-2 after 15 days. No significant differences were found between the two BLS activities used. In the control without BLS, L. monocytogenes counts increased to 1.0 x 10(6 cfu cm-2 after 15 days of storage.Três meios de cultura foram avaliados quanto a produção de substâncias semelhantes a bacteriocinas (SSB por Carnobacterium piscicola L 103, utilizando um sistema contínuo de cultura. A eficácia da substância antagonista contra Listeria monocytogenes foi testada em salmão embalado a vácuo. As SSB foram produzidas em bioreator de 1.0 L, em cultura contínua e em cultura estacionária, utilizando D-MRS, mod. D-MRS e APT como meios de cultivo. Filés de salmão foram inoculados com SSB (200 AU mL-1 e 800 AU mL-1 e L. monocytogenes (8.0 x 10¹ ufc cm-2 e mantidos a 4ºC. O crescimento de L. monocytogenes foi

  15. Listeria monocytogenes: survival and adaptation in the gastrointestinal tract

    Directory of Open Access Journals (Sweden)

    Cormac G.M. Gahan

    2014-02-01

    Full Text Available The foodborne pathogen Listeria monocytogenes has the capacity to survive and grow in a diverse range of natural environments. The transition from a food environment to the gastrointestinal tract begins a process of adaptation that may culminate in invasive systemic disease. Here we describe recent advances in our understanding of how L. monocytogenes adapts to the gastrointestinal environment prior to initiating systemic infection. We will discuss mechanisms used by the pathogen to survive encounters with acidic environments (which include the glutamate decarboxylase and arginine deiminase systems, and those which enable the organism to cope with bile acids (including bile salt hydrolase and competition with the resident microbiota. An increased understanding of how the pathogen survives in this environment is likely to inform the future design of novel prophylactic approaches that exploit specific pharmabiotics; including probiotics, prebiotics or phages.

  16. Keberadaan Bakteri Listeria monocytogenes pada Keju Gouda Produksi Lokal dan Impor (PRESENCE OF LISTERIA MONOCYTOGENES IN LOCAL AND IMPORTED GOUDA CHEESES

    Directory of Open Access Journals (Sweden)

    Debby Fadhilah Pazra

    2014-08-01

    Full Text Available Listeria monocytogenes is included in the foodborne pathogen, which has been associated with severaloutbreaks of human listeriosis especially in high risk groups. Listeria monocytogenes could be found inGouda cheeses because of poor hygienic and sanitation practices. In addition, this bacteria could surviveduring the making of cheese and cheese ripening process. The purpose of this study was to identify thepresence of L. monocytogenes in local and imported Gouda cheeses and how the safety level of the Goudacheese against contamination of L. monocytogenes. This study used the conventional method in accordancewith the Bacteriological Analytical Manual, US Food and Drug Administration and Bergey’s Manual ofDeterminative Bacteriology to detect the presence of L. monocytogenes at 15 samples of local Gouda cheeseand 15 samples of imported Gouda cheese sold in supermarkets in Jakarta and Bogor. The results of thisstudy showed that was not found L. monocytogenes in local and imported Gouda cheese. It could be concludedthat is Gouda cheese relatively safe from L. monocytogenes and meets Indonesian National Standard.

  17. Transcriptional and phenotypic responses of Listeria monocytogenes to chlorine dioxide.

    Science.gov (United States)

    Pleitner, Aaron M; Trinetta, Valentina; Morgan, Mark T; Linton, Richard L; Oliver, Haley F

    2014-05-01

    Significant food-borne disease outbreaks have occurred from consumption of ready-to-eat foods, including produce, contaminated with Listeria monocytogenes. Challenging food matrices (e.g., cantaloupe, sprouts) with limited processing steps postharvest to reduce pathogen loads have underscored a need for new mitigation strategies. Chlorine dioxide (ClO2) is increasingly being used in produce and other food systems to reduce food-borne pathogen levels. The goal of this study was to characterize the transcriptional response and survival of L. monocytogenes 10403S exposed to ClO2. The transcriptional profile of log-phase cells exposed to 300 mg/liter ClO2 for 15 min was defined by whole-genome microarray. A total of 340 genes were significantly differentially expressed. Among the differentially expressed genes, 223 were upregulated (fold change ≥ 1.5; adjusted P value < 0.05) in role categories responsible for protein fate, cellular processes, and energy metabolism. There were 113 and 16 genes differentially expressed belonging to regulatory networks of σ(B) and CtsR, respectively. We assessed L. monocytogenes 10403S survival after exposure to 100, 300, and 500 mg/liter aqueous ClO2 in brain heart infusion (BHI) broth; there was a significant difference between cells exposed to 500 mg/liter ClO2 and those exposed to all other conditions over time (P value < 0.05). Isogenic ΔsigB and ΔctsR mutants exposed to 300 mg/liter ClO2 were more sensitive to ClO2 than the wild type under the same conditions. These results provide an initial insight into the mechanisms that L. monocytogenes employs to survive sublethal ClO2 and further our understanding of the inactivation mechanisms of this increasingly used sanitizer.

  18. How Listeria monocytogenes organizes its surface for virulence

    Directory of Open Access Journals (Sweden)

    Filipe eCarvalho

    2014-04-01

    Full Text Available 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 are 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.

  19. 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

  20. Targeting of the central nervous system by Listeria monocytogenes.

    OpenAIRE

    Disson, Olivier; Lecuit, Marc

    2012-01-01

    Among bacteria that reach the central nervous system (CNS), Listeria monocytogenes (Lm) is one of deadliest, in human and ruminant. This facultative intracellular bacterium has the particularity to induce meningitis, meningoencephalitis and rhombencephalitis. Mechanisms by which Lm accesses the CNS remain poorly understood, but two major routes of infection have been proposed, based on clinical, in vitro and in vivo observations. A retrograde neural route is likely to occur in ruminants upon ...

  1. Hoechst fluorescence intensity can be used to separate viable bromodeoxyuridine-labeled cells from viable non-bromodeoxyuridine-labeled cells

    Science.gov (United States)

    Mozdziak, P. E.; Pulvermacher, P. M.; Schultz, E.; Schell, K.

    2000-01-01

    BACKGROUND: 5-Bromo-2'-deoxyuridine (BrdU) is a powerful compound to study the mitotic activity of a cell. Most techniques that identify BrdU-labeled cells require conditions that kill the cells. However, the fluorescence intensity of the membrane-permeable Hoechst dyes is reduced by the incorporation of BrdU into DNA, allowing the separation of viable BrdU positive (BrdU+) cells from viable BrdU negative (BrdU-) cells. METHODS: Cultures of proliferating cells were supplemented with BrdU for 48 h and other cultures of proliferating cells were maintained without BrdU. Mixtures of viable BrdU+ and viable BrdU- cells from the two proliferating cultures were stained with Hoechst 33342. The viable BrdU+ and BrdU- cells were sorted into different fractions from a mixture of BrdU+ and BrdU- cells based on Hoechst fluorescence intensity and the ability to exclude the vital dye, propidium iodide. Subsequently, samples from the original mixture, the sorted BrdU+ cell population, and the sorted BrdU- cell population were immunostained using an anti-BrdU monoclonal antibody and evaluated using flow cytometry. RESULTS: Two mixtures consisting of approximately 55% and 69% BrdU+ cells were sorted into fractions consisting of greater than 93% BrdU+ cells and 92% BrdU- cells. The separated cell populations were maintained in vitro after sorting to demonstrate their viability. CONCLUSIONS: Hoechst fluorescence intensity in combination with cell sorting is an effective tool to separate viable BrdU+ from viable BrdU- cells for further study. The separated cell populations were maintained in vitro after sorting to demonstrate their viability. Copyright 2000 Wiley-Liss, Inc.

  2. Towards a systemic understanding of Listeria monocytogenes metabolism during infection

    Directory of Open Access Journals (Sweden)

    Thilo M Fuchs

    2012-02-01

    Full Text Available Listeria monocytogenes is a foodborne human pathogen that can cause invasive infection in susceptible animals and humans. For proliferation within hosts, this facultative intracellular pathogen uses a reservoir of specific metabolic pathways, transporter and enzymatic functions whose expression requires the coordinated activity of a complex regulatory network. The highly adapted metabolism of L. monocytogenes strongly depends on the nutrient composition of various milieus encountered during infection. Transcriptomic and proteomic studies revealed the spatial-temporal dynamic of gene expression of this pathogen during replication within cultured cells or in vivo. Metabolic clues are the utilization of unusual C2- and C3-bodies, the metabolism of pyruvate, thiamine availability, the uptake of peptides, the acquisition or biosynthesis of certain amino acids, and the degradation of glucose-phosphate via the pentose phosphate pathway. These examples illustrate the interference of in vivo conditions with energy, carbon and nitrogen metabolism, thus affecting listerial growth. The exploitation, analysis and modelling of the available data sets served as a first attempt to a systemic understanding of listerial metabolism during infection. L. monocytogenes might serve as a model organism for systems biology of a Gram-positive, facultative intracellular bacterium.

  3. 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.

  4. Recombinant Probiotic Expressing Listeria Adhesion Protein Attenuates Listeria monocytogenes Virulence In Vitro

    Science.gov (United States)

    Koo, Ok Kyung; Amalaradjou, Mary Anne Roshni; Bhunia, Arun K.

    2012-01-01

    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 (LbpLAP) 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 LbpLAP for 1, 4, 15, or 24 h significantly (Pmonocytogenes in Caco-2 cells, whereas pre-exposure to parental Lb. paracasei had no significant effect. Similarly, LbpLAP pre-exposure reduced L. monocytogenes translocation by as much as 46% after 24 h. LbpLAP also prevented L. monocytogenes-mediated cell damage and compromise of tight junction integrity. Furthermore, LbpLAP 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, LbpLAP blocked adhesion, invasion, and translocation of L. monocytogenes by interacting with host cell receptor Hsp60, thereby protecting cells from infection. These data show promise for the use of recombinant probiotics in preventing L. monocytogenes infection in high

  5. A survey of iceberg lettuce for the presence of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in Japan.

    Science.gov (United States)

    Koseki, Shigenobu; Mizuno, Yasuko; Kawasaki, Susumu; Yamamoto, Kazutaka

    2011-09-01

    No information has been available on the prevalence of pathogens in fresh produce in Japan. In the present study, information was collected on the occurrence of contamination by Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in iceberg lettuce in a Japanese retail store. A total of 419 samples of lettuce that had been harvested in different districts and/or by different producers from July 2008 to March 2009 were examined. A multiplex PCR method was used to simultaneously identify the three bacterial pathogens. No pathogenic bacteria, including Salmonella, E. coli O157:H7, and L. monocytogenes, were detected from any of the samples with this highly sensitive and validated procedure. The aerobic bacteria plate counts and coliform bacteria counts in lettuce throughout the examination period did not show any seasonal trends, and the numbers were comparable to those reported by others from around the world. Based on the results of this study, we concluded that none of the three major pathogens were present in this limited survey of iceberg lettuce sold by a retailer in Japan.

  6. Resolved SZE Cluster Count

    Institute of Scientific and Technical Information of China (English)

    Jia-Yu Tang; Zu-Hui Fan

    2003-01-01

    We study the counts of resolved SZE (Sunyaev-Zel'dovich effect) clus-ters expected from an interferometric survey in different cosmological models underdifferent conditions. The self-similar universal gas model and Press-Schechter massfunction are used. We take the observing frequency to be 90 GHz, and consider twodish diameters, 1.2 m and 2.5 m. We calculate the number density of the galaxyclusters dN/(dΩdz) at a high flux limit Slimv = 100mJy and at a relative lowSlimv = 10 mJy. The total numbers of SZE clusters N in two low-Ω0 models arecompared. The results show that the influence of the resolved effect depends notonly on D, but also on Slimv: at a given D, the effect is more significant for a highthan for a low Slim Also, the resolved effect for a flat universe is more impressivethan that for an open universe. For D = 1.2m and Slimv= 10mJy, the resolvedeffect is very weak. Considering the designed interferometers which will be used tosurvey SZE clusters, we find that the resolved effect is insignificant when estimatingthe expected yield of the SZE cluster surveys.

  7. Multivariate ultrametric root counting

    CERN Document Server

    Avendano, Martin

    2011-01-01

    Let $K$ be a field, complete with respect to a discrete non-archimedian valuation and let $k$ be the residue field. Consider a system $F$ of $n$ polynomial equations in $K\\vars$. Our first result is a reformulation of the classical Hensel's Lemma in the language of tropical geometry: we show sufficient conditions (semiregularity at $w$) that guarantee that the first digit map $\\delta:(K^\\ast)^n\\to(k^\\ast)^n$ is a one to one correspondence between the solutions of $F$ in $(K^\\ast)^n$ with valuation $w$ and the solutions in $(k^\\ast)^n$ of the initial form system ${\\rm in}_w(F)$. Using this result, we provide an explicit formula for the number of solutions in $(K^\\ast)^n$ of a certain class of systems of polynomial equations (called regular), characterized by having finite tropical prevariety, by having initial forms consisting only of binomials, and by being semiregular at any point in the tropical prevariety. Finally, as a consequence of the root counting formula, we obtain the expected number of roots in $(K...

  8. Making environmental DNA count.

    Science.gov (United States)

    Kelly, Ryan P

    2016-01-01

    The arc of reception for a new technology or method--like the reception of new information itself--can pass through predictable stages, with audiences' responses evolving from 'I don't believe it', through 'well, maybe' to 'yes, everyone knows that' to, finally, 'old news'. The idea that one can sample a volume of water, sequence DNA out of it, and report what species are living nearby has experienced roughly this series of responses among biologists, beginning with the microbial biologists who developed genetic techniques to reveal the unseen microbiome. 'Macrobial' biologists and ecologists--those accustomed to dealing with species they can see and count--have been slower to adopt such molecular survey techniques, in part because of the uncertain relationship between the number of recovered DNA sequences and the abundance of whole organisms in the sampled environment. In this issue of Molecular Ecology Resources, Evans et al. (2015) quantify this relationship for a suite of nine vertebrate species consisting of eight fish and one amphibian. Having detected all of the species present with a molecular toolbox of six primer sets, they consistently find DNA abundances are associated with species' biomasses. The strength and slope of this association vary for each species and each primer set--further evidence that there is no universal parameter linking recovered DNA to species abundance--but Evans and colleagues take a significant step towards being able to answer the next question audiences tend to ask: 'Yes, but how many are there?'

  9. LAWRENCE RADIATION LABORATORY COUNTING HANDBOOK

    Energy Technology Data Exchange (ETDEWEB)

    Group, Nuclear Instrumentation

    1966-10-01

    The Counting Handbook is a compilation of operational techniques and performance specifications on counting equipment in use at the Lawrence Radiation Laboratory, Berkeley. Counting notes have been written from the viewpoint of the user rather than that of the designer or maintenance man. The only maintenance instructions that have been included are those that can easily be performed by the experimenter to assure that the equipment is operating properly.

  10. Counting Frequencies from Zotero Items

    Directory of Open Access Journals (Sweden)

    Spencer Roberts

    2013-04-01

    Full Text Available In Counting Frequencies you learned how to count the frequency of specific words in a list using python. In this lesson, we will expand on that topic by showing you how to get information from Zotero HTML items, save the content from those items, and count the frequencies of words. It may be beneficial to look over the previous lesson before we begin.

  11. SUMS Counts-Related Projects

    Data.gov (United States)

    Social Security Administration — Staging Instance for all SUMs Counts related projects including: Redeterminations/Limited Issue, Continuing Disability Resolution, CDR Performance Measures, Initial...

  12. SURVIVAL, INDUCTION AND RESUSCITATION OF Vibrio cholerae FROM THE VIABLE BUT NON-CULTURABLE STATE IN THE SOUTHERN CARIBBEAN SEA

    Directory of Open Access Journals (Sweden)

    Milagro Fernández-Delgado

    2015-02-01

    Full Text Available The causative agent of cholera, Vibrio cholerae, can enter into a viable but non-culturable (VBNC state in response to unfavorable conditions. The aim of this study was to evaluate the in situ survival of V. cholerae in an aquatic environment of the Southern Caribbean Sea, and its induction and resuscitation from the VBNC state. V. cholerae non-O1, non-O139 was inoculated into diffusion chambers placed at the Cuare Wildlife Refuge, Venezuela, and monitored for plate, total and viable cells counts. At 119 days of exposure to the environment, the colony count was < 10 CFU/mL and a portion of the bacterial population entered the VBNC state. Additionally, the viability decreased two orders of magnitude and morphological changes occurred from rod to coccoid cells. Among the aquatic environmental variables, the salinity had negative correlation with the colony counts in the dry season. Resuscitation studies showed significant recovery of cell cultivability with spent media addition (p < 0.05. These results suggest that V. cholerae can persist in the VBNC state in this Caribbean environment and revert to a cultivable form under favorable conditions. The VBNC state might represent a critical step in cholera transmission in susceptible areas.

  13. SURVIVAL, INDUCTION AND RESUSCITATION OF Vibrio cholerae FROM THE VIABLE BUT NON-CULTURABLE STATE IN THE SOUTHERN CARIBBEAN SEA

    Science.gov (United States)

    Fernández-Delgado, Milagro; García-Amado, María Alexandra; Contreras, Monica; Incani, Renzo Nino; Chirinos, Humberto; Rojas, Héctor; Suárez, Paula

    2015-01-01

    The causative agent of cholera, Vibrio cholerae, can enter into a viable but non-culturable (VBNC) state in response to unfavorable conditions. The aim of this study was to evaluate the in situ survival of V. cholerae in an aquatic environment of the Southern Caribbean Sea, and its induction and resuscitation from the VBNC state. V. cholerae non-O1, non-O139 was inoculated into diffusion chambers placed at the Cuare Wildlife Refuge, Venezuela, and monitored for plate, total and viable cells counts. At 119 days of exposure to the environment, the colony count was < 10 CFU/mL and a portion of the bacterial population entered the VBNC state. Additionally, the viability decreased two orders of magnitude and morphological changes occurred from rod to coccoid cells. Among the aquatic environmental variables, the salinity had negative correlation with the colony counts in the dry season. Resuscitation studies showed significant recovery of cell cultivability with spent media addition (p < 0.05). These results suggest that V. cholerae can persist in the VBNC state in this Caribbean environment and revert to a cultivable form under favorable conditions. The VBNC state might represent a critical step in cholera transmission in susceptible areas. PMID:25651322

  14. Listeria monocytogenes and the inflammasome: from cytosolic bacteriolysis to tumor immunotherapy

    Science.gov (United States)

    Theisen, Erin; Sauer, John-Demian

    2016-01-01

    Inflammasomes are cytosolic innate immune surveillance systems that recognize a variety of danger signals, including those from pathogens. Listeria monocytogenes is a Gram-positive intracellular bacterium evolved to live within the harsh environment of the host cytosol. Further, L. monocytogenes can activate a robust cell-mediated immune response that is being harnessed as an immunotherapeutic platform. Access to the cytosol is critical for both causing disease and for inducing a protective immune response, and it is hypothesized that the cytosolic innate immune system, including the inflammasome, is critical for both host protection and induction of long term immunity. L. monocytogenes can activate a variety of inflammasomes via its pore-forming toxin Listeriolysin-O, flagellin, or DNA released through bacteriolysis; however, inflammasome activation attenuates L. monocytogenes, and as such, L. monocytogenes has evolved a variety of ways to limit inflammasome activation. Surprisingly, inflammasome activation also impairs the host cell-mediated immune response. Thus understanding how L. monocytogenes activates or avoids detection by the inflammasome is critical to understand the pathogenesis of L. monocytogenes and improve the cell-mediated immune response generated to L. monocytogenes for more effective immunotherapies. PMID:27460808

  15. Stability of sublethal acid stress adaptaion and induced cross protection against lauric arginate in Listeria monocytogenes

    Science.gov (United States)

    The stability of acid stress adaptation in Listeria monocytogenes and its induced cross protection effect against GRAS (generally recognized as safe) antimicrobial compounds has never been investigated before. In the present study, the acid stress adaptation in L. monocytogenes was initially induced...

  16. Listeria monocytogenes DNA glycosylase AdiP affects flagellar motility, biofilm formation, virulence, and stress responses

    Science.gov (United States)

    The temperature-dependent alteration of flagellar motility gene expression is critical for the foodborne pathogen Listeria monocytogenes to respond to a changing environment. In this study, a genetic determinant, L. monocytogenes f2365_0220 (lmof2365_0220), encoding a putative protein that is struct...

  17. 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.

  18. Influence of temperature on acid-stress adaptation in Listeria monocytogenes

    Science.gov (United States)

    Several factors play critical roles in controlling the induction of acid-stress adaptation in L. monocytogenes. Our findings show that temperature plays a significant role in the induction of acid-stress adaptation in Listeria monocytogenes and two distinct patterns were observed: (I) Presence of su...

  19. Listeria monocytogenes detection and behaviour in food and in the environment.

    NARCIS (Netherlands)

    Beumer, R.R.

    1997-01-01

    In this thesis, Listeria monocytogenes, a bacterial pathogen was studied, with emphasis on the detection and behaviour in food and environment.Epidemics of foodborne listeriosis have raised concern about the incidence of L. monocytogenes in foods. In the past 10-15 years listeriosis has emerged as a

  20. 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 wer

  1. 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...

  2. Betaine and L-carnitine transport by Listeria monocytogenes Scott A in response to osmotic signals

    NARCIS (Netherlands)

    Verheul, Annette; Glaasker, Erwin; Poolman, Bert; Abee, Tjakko

    1997-01-01

    The naturally occurring compatible solutes betaine and L-carnitine allow the food-borne pathogen Listeria monocytogenes to adjust to environments of high osmotic strength. Previously, it was demonstrated that L. monocytogenes possesses an ATP-dependent L-carnitine transporter. The present study reve

  3. 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...

  4. Determination of thermal inactivation kinetics of Listeria monocytogenes in chicken meat by isothermal and dynamic methods

    Science.gov (United States)

    The objective of this research is to determine the thermal inactivation kinetics of Listeria monocytogenes in chicken breast meat using both isothermal and dynamic conditions. A four-strain cocktail of L. monocytogenes was inoculated to chicken breast meat. Isothermal studies were performed by sub...

  5. Performance of stress resistant variants of Listeria monocytogenes in mixed species biofilms with Lactobacillus plantarum

    NARCIS (Netherlands)

    Metselaar, K.I.; Saa Ibusquiza, P.; Ortiz Camargo, A.R.; Krieg, M.; Zwietering, M.H.; Besten, den H.M.W.; Abee, T.

    2015-01-01

    Population diversity and the ability to adapt to changing environments allow Listeria monocytogenes to grow and survive under a wide range of environmental conditions. In this study, we aimed to evaluate the performance of a set of acid resistant L. monocytogenes variants in mixed-species biofilms w

  6. Surface attachment of Listeria monocytogenes is induced by sublethal concentrations of alcohol at low temperatures.

    Science.gov (United States)

    Gravesen, Anne; Lekkas, Charidimos; Knøchel, Susanne

    2005-09-01

    Sublethal concentrations of ethanol or isopropanol increased attachment of Listeria monocytogenes at 10, 20, or 30 degrees C; no induction occurred at 37 degrees C. The alcohol induction phenotype was retained in sigB and cesRK mutants; however, the degree of induction was affected. These results suggest that alcohol may contribute to the persistence of L. monocytogenes.

  7. Physiology of Listeria monocytogenes in relation to food components and biopreservation.

    NARCIS (Netherlands)

    Verheul, A.

    1997-01-01

    Listeria monocytogenes is an important foodborne pathogen that has been responsible for severe infections in humans. The ubiquitous distribution of L. monocytogenes in the environment and its ability to grow at refrigeration temperature and at high osmolarity are of paramount importance for its haz

  8. 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.

  9. Betaine and L-carnitine transport by Listeria monocytogenes Scott A in response to osmotic signals

    NARCIS (Netherlands)

    Verheul, Annette; Glaasker, Erwin; Poolman, Bert; Abee, Tjakko

    1997-01-01

    The naturally occurring compatible solutes betaine and L-carnitine allow the food-borne pathogen Listeria monocytogenes to adjust to environments of high osmotic strength. Previously, it was demonstrated that L. monocytogenes possesses an ATP-dependent L-carnitine transporter. The present study

  10. 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

  11. 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. m...

  12. Modeling the growth of Listeria monocytogenes on cut cantaloupe, honeydew and watermelon.

    Science.gov (United States)

    Danyluk, Michelle D; Friedrich, Loretta M; Schaffner, Donald W

    2014-04-01

    A recent outbreak linked to whole cantaloupes underscores the importance of understanding growth kinetics of Listeria monocytogenes in cut melons at different temperatures. Whole cantaloupe, watermelon, and honeydew purchased from a local supermarket were cut into 10 ± 1 g cubes. A four-strain cocktail of L. monocytogenes from food related outbreaks was used to inoculate fruit, resulting in ~10(3) CFU/10 g. Samples were stored at 4, 10, 15, 20, or 25 °C and L. monocytogenes were enumerated at appropriate time intervals. The square root model was used to describe L. monocytogenes growth rate as a function of temperature. The model was compared to prior models for Salmonella and Escherichia coli O157:H7 growth on cut melon, as well as models for L. monocytogenes on cantaloupe and L. monocytogenes ComBase models. The current model predicts faster growth of L. monocytogenes vs. Salmonella and E. coli O157:H7 at temperatures below 20 °C, and agrees with estimates from ComBase Predictor, and a corrected published model for L. monocytogenes on cut cantaloupe. The model predicts ~4 log CFU increase following 15 days at 5 °C, and ∼1 log CFU increase following 6 days at 4 °C. The model can also be used in subsequent quantitative microbial risk assessments.

  13. 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.

  14. Reference counting for reversible languages

    DEFF Research Database (Denmark)

    Mogensen, Torben Ægidius

    2014-01-01

    deallocation. This requires the language to be linear: A pointer can not be copied and it can only be eliminated by deallocating the node to which it points. We overcome this limitation by adding reference counts to nodes: Copying a pointer to a node increases the reference count of the node and eliminating...

  15. Coinductive counting with weighted automata

    NARCIS (Netherlands)

    Rutten, J.J.M.M.

    2002-01-01

    A general methodology is developed to compute the solution of a wide variety of basic counting problems in a uniform way: (1) the objects to be counted are enumerated by means of an infinite weighted automaton; (2) the automaton is reduced by means of the quantitative notion of stream bisimulation;

  16. Low White Blood Cell Count

    Science.gov (United States)

    Symptoms Low white blood cell count By Mayo Clinic Staff A low white blood cell count (leukopenia) is a decrease in disease-fighting cells ( ... a decrease in a certain type of white blood cell (neutrophil). The definition of low white blood cell ...

  17. A commercially viable route to polymerization grade phenylterephthalic acid

    Energy Technology Data Exchange (ETDEWEB)

    Koshel, G.N.; Koshel, S.G.; Rudkovsky, E.K. [Yaroslav, Yaroslav State Technical University (Russian Federation). Dept. of Inorganic and Physical Chemistry; Poli, G.; Vitolo, S.; Magagnini, P. [Pisa, Univ. (Italy). Dip. di Ingegneria Chimica, Chimica Industriale e Scienza dei materiali

    1998-03-01

    Phenylterephthalic acid (PTA) has a potential as comonomer for the production of high performance liquid-crystalline polyesters. The available synthetic routes to PTA are reviewed, and a new, commercially viable process based on the use of cheap raw materials, such as p-xylene and cyclohexene, is described.

  18. Singularity phenomena in viable f(R) gravity

    CERN Document Server

    Lee, Chung-Chi; Yang, Louis

    2012-01-01

    The curvature singularity in viable f(R) gravity models is examined when the background density is dense. This singularity could be eliminated by adding the $R^{2}$ term in the Lagrangian. Some of cosmological consequences, in particular the source for the scalar mode of gravitational waves, are discussed.

  19. A METHOD TO DETECT VIABLE HELICOBACTER PYLORI BACTERIA IN GROUNDWATER

    Science.gov (United States)

    The inability to detect the presence of viable Helicobacter pylori bacteria in environmental waters has hindered the public health community in assessing the role water may playin the transmission of this pathogen. This work describes a cultural enrichment method coupled with an...

  20. 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...

  1. Hanford whole body counting manual

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, H.E.; Brim, C.P.; Rieksts, G.A.; Rhoads, M.C.

    1987-05-01

    This document, a reprint of the Whole Body Counting Manual, was compiled to train personnel, document operation procedures, and outline quality assurance procedures. The current manual contains information on: the location, availability, and scope of services of Hanford's whole body counting facilities; the administrative aspect of the whole body counting operation; Hanford's whole body counting facilities; the step-by-step procedure involved in the different types of in vivo measurements; the detectors, preamplifiers and amplifiers, and spectroscopy equipment; the quality assurance aspect of equipment calibration and recordkeeping; data processing, record storage, results verification, report preparation, count summaries, and unit cost accounting; and the topics of minimum detectable amount and measurement accuracy and precision. 12 refs., 13 tabs.

  2. Short communication: Latin-style fresh cheese enhances lactic acid bacteria survival but not Listeria monocytogenes resistance under in vitro simulated gastrointestinal conditions.

    Science.gov (United States)

    Silva, C C G; Domingos-Lopes, M F P; Magalhães, V A F; Freitas, D A S R; Coelho, M C; Rosa, H J D; Dapkevicius, M L N E

    2015-07-01

    Different studies in humans have provided evidence about the health benefits of probiotics. However, most probiotic strains do not maintain good viability in the harsh conditions of the gastrointestinal tract (GIT). In the present study, Latin-style fresh cheese produced with potential probiotic bacteria was tested to evaluate this cheese type as a food carrier for the delivery of viable microorganisms after exposure to simulated GIT conditions. The resistance of 28 lactic acid bacteria (LAB) strains and Listeria monocytogenes upon exposure to acidic conditions (pH 2.5) and bile and pancreatic enzymes (0.3% of bile salts and 0.1% of pancreatin) was evaluated in vitro. When compared with fresh cultures, fresh cheese greatly improved LAB survival to simulated GIT conditions, as no loss of viability was observed in either acidic conditions (pH 2.5) or bile salts and pancreatin environment over a 3-h period. In opposition, L. monocytogenes did not survive after 1h under acidic conditions. These data demonstrated that Latin-style fresh cheese could play an important role in probiotic protection against gastrointestinal juices, enhancing delivery within the gut and thereby maximizing potential health benefits of LAB.

  3. Phage display-derived binders able to distinguish Listeria monocytogenes from other Listeria species.

    Directory of Open Access Journals (Sweden)

    Josephine Morton

    Full Text Available The objective of this study was to produce phage display-derived binders with the ability to distinguish Listeria monocytogenes from other Listeria spp., which may have potential utility to enhance detection of Listeria monocytogenes. To obtain binders with the desired binding specificity a series of surface and solution phage-display biopannings were performed. Initially, three rounds of surface biopanning against gamma-irradiated L. monocytogenes serovar 4b cells were performed followed by an additional surface biopanning round against L. monocytogenes 4b which included prior subtraction biopanning against gamma-irradiated L. innocua cells. In an attempt to further enhance binder specificity for L. monocytogenes 4b two rounds of solution biopanning were performed, both rounds included initial subtraction solution biopanning against L. innocua. Subsequent evaluations were performed on the phage clones by phage binding ELISA. All phage clones tested from the second round of solution biopanning had higher specificity for L. monocytogenes 4b than for L. innocua and three other foodborne pathogens (Salmonella spp., Escherichia coli and Campylobacter jejuni. Further evaluation with five other Listeria spp. revealed that one phage clone in particular, expressing peptide GRIADLPPLKPN, was highly specific for L. monocytogenes with at least 43-fold more binding capability to L. monocytogenes 4b than to any other Listeria sp. This proof-of-principle study demonstrates how a combination of surface, solution and subtractive biopanning was used to maximise binder specificity. L. monocytogenes-specific binders were obtained which could have potential application in novel detection tests for L. monocytogenes, benefiting both the food and medical industries.

  4. Phage display-derived binders able to distinguish Listeria monocytogenes from other Listeria species.

    Science.gov (United States)

    Morton, Josephine; Karoonuthaisiri, Nitsara; Charlermroj, Ratthaphol; Stewart, Linda D; Elliott, Christopher T; Grant, Irene R

    2013-01-01

    The objective of this study was to produce phage display-derived binders with the ability to distinguish Listeria monocytogenes from other Listeria spp., which may have potential utility to enhance detection of Listeria monocytogenes. To obtain binders with the desired binding specificity a series of surface and solution phage-display biopannings were performed. Initially, three rounds of surface biopanning against gamma-irradiated L. monocytogenes serovar 4b cells were performed followed by an additional surface biopanning round against L. monocytogenes 4b which included prior subtraction biopanning against gamma-irradiated L. innocua cells. In an attempt to further enhance binder specificity for L. monocytogenes 4b two rounds of solution biopanning were performed, both rounds included initial subtraction solution biopanning against L. innocua. Subsequent evaluations were performed on the phage clones by phage binding ELISA. All phage clones tested from the second round of solution biopanning had higher specificity for L. monocytogenes 4b than for L. innocua and three other foodborne pathogens (Salmonella spp., Escherichia coli and Campylobacter jejuni). Further evaluation with five other Listeria spp. revealed that one phage clone in particular, expressing peptide GRIADLPPLKPN, was highly specific for L. monocytogenes with at least 43-fold more binding capability to L. monocytogenes 4b than to any other Listeria sp. This proof-of-principle study demonstrates how a combination of surface, solution and subtractive biopanning was used to maximise binder specificity. L. monocytogenes-specific binders were obtained which could have potential application in novel detection tests for L. monocytogenes, benefiting both the food and medical industries.

  5. Mathematical modelling of growth of Listeria  monocytogenes in raw chilled pork.

    Science.gov (United States)

    Ye, K; Wang, K; Liu, M; Liu, J; Zhu, L; Zhou, G

    2017-04-01

    The aim of this study was to analyse the growth kinetics of Listeria monocytogenes in naturally contaminated chilled pork. A cocktail of 26 meat-borne L. monocytogenes was inoculated to raw or sterile chilled pork to observe its growth at 4, 10, 16, 22 and 28°C respectively. The growth data were fitted by the Baranyi model and Ratkowsky square-root model. Results showed that the Baranyi model and Ratkowsky square-root model could describe the growth characteristics of L. monocytogenes at different temperatures reasonably well in raw chilled pork (1·0 ≤ Bf ≤ Af ≤ 1·1). Compared with the growth of L. monocytogenes in sterile chilled pork, the background microflora had no impact on the growth parameters of L. monocytogenes, except for the lag phase at low temperature storage. The microbial predictive models developed in this study can be used to predict the growth of L. monocytogenes during natural spoilage, and construct quantitative risk assessments in chilled pork. This study simulated the actual growth of Listeria monocytogenes in chilled pork to the maximum extent, and described its growth characteristics of L. monocytogenes during natural spoilage. This study showed that the background microflora had no impact on the growth parameters of L. monocytogenes, except for the lag phase at low temperature storage. The models developed in this study can be used to predict the growth of L. monocytogenes during refrigerated storage. © 2017 The Society for Applied Microbiology.

  6. The origins of counting algorithms.

    Science.gov (United States)

    Cantlon, Jessica F; Piantadosi, Steven T; Ferrigno, Stephen; Hughes, Kelly D; Barnard, Allison M

    2015-06-01

    Humans' ability to count by verbally labeling discrete quantities is unique in animal cognition. The evolutionary origins of counting algorithms are not understood. We report that nonhuman primates exhibit a cognitive ability that is algorithmically and logically similar to human counting. Monkeys were given the task of choosing between two food caches. First, they saw one cache baited with some number of food items, one item at a time. Then, a second cache was baited with food items, one at a time. At the point when the second set was approximately equal to the first set, the monkeys spontaneously moved to choose the second set even before that cache was completely baited. Using a novel Bayesian analysis, we show that the monkeys used an approximate counting algorithm for comparing quantities in sequence that is incremental, iterative, and condition controlled. This proto-counting algorithm is structurally similar to formal counting in humans and thus may have been an important evolutionary precursor to human counting. © The Author(s) 2015.

  7. High Count Rate Single Photon Counting Detector Array Project

    Data.gov (United States)

    National Aeronautics and Space Administration — An optical communications receiver requires efficient and high-rate photon-counting capability so that the information from every photon, received at the aperture,...

  8. Vote Counting as Mathematical Proof

    DEFF Research Database (Denmark)

    Schürmann, Carsten; Pattinson, Dirk

    2015-01-01

    Trust in the correctness of an election outcome requires proof of the correctness of vote counting. By formalising particular voting protocols as rules, correctness of vote counting amounts to verifying that all rules have been applied correctly. A proof of the outcome of any particular election......-based formalisation of voting protocols inside a theorem prover, we synthesise vote counting programs that are not only provably correct, but also produce independently verifiable certificates. These programs are generated from a (formal) proof that every initial set of ballots allows to decide the election winner...

  9. White blood cell counting system

    Science.gov (United States)

    1972-01-01

    The design, fabrication, and tests of a prototype white blood cell counting system for use in the Skylab IMSS are presented. The counting system consists of a sample collection subsystem, sample dilution and fluid containment subsystem, and a cell counter. Preliminary test results show the sample collection and the dilution subsystems are functional and fulfill design goals. Results for the fluid containment subsystem show the handling bags cause counting errors due to: (1) adsorption of cells to the walls of the container, and (2) inadequate cleaning of the plastic bag material before fabrication. It was recommended that another bag material be selected.

  10. 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.

  11. 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.

  12. Gamma radiation used as hygienization technique for foods does not induce viable but non-culturable state (VBNC) in Salmonella enterica subsp. enterica serovar Typhimurium.

    Science.gov (United States)

    Saroj, Sunil; Shashidhar, R; Bandekar, Jayant

    2009-10-01

    Gamma radiation has been widely used for hygienization of food products. Whether gamma radiation stress induces VBNC state in Salmonella is of great concern. Therefore, the study was carried out to determine whether gamma radiation exposure induces VBNC state in Salmonella enterica subsp. enterica serovar Typhimurium (S. typhimurium). The parameters tested were culturability on agar medium, transcriptional activity by RT-PCR, cytoplasmic membrane integrity, and direct viable count using LIVE/DEAD BacLight bacterial viability kit. The LIVE/DEAD BacLight counts for S. typhimurium cells treated with 0.5 and 1.0 kGy radiation dose were 0.8 and 0.1% of the control, respectively. Plate counts for S. typhimurium cells treated with 0.5 and 1.0 kGy radiation dose were 0.7 and 0.05% of the control, respectively. No viable cells of S. typhimurium were detected by both plate count and LIVE/DEAD BacLight after radiation treatment with 2 kGy. No transcriptional activity was detected in cells treated with 2 kGy radiation dose. If there were VBNC cells present, then significant differences in the counts between the LIVE/DEAD BacLight microscopic counts and plate agar counts must be observed. No significant difference (P > 0.05) in the counts were observed. Thus, it can be concluded that treatment with 2 kGy results in complete killing and does not induce VBNC state in S. typhimurium.

  13. Carbon dioxide and nisin act synergistically on Listeria monocytogenes

    DEFF Research Database (Denmark)

    Nilsson, Lilian; Chen, Y.H.; Chikindas, M.L.

    2000-01-01

    This paper examines the synergistic action of carbon dioxide and nisin on Listeria monocytogenes Scott A wild-type and nisin-resistant (Nis(r)) cells grown in broth at 4 degrees C. Carbon dioxide extended the lag phase and decreased the specific growth rate of both strains, but to a greater degree...... for cultures in CO2. This synergism between nisin and CO2 was examined mechanistically by following the leakage of carboxyfluorescein (CF) from listerial liposomes. Carbon dioxide enhanced nisin-induced CF leakage, indicating that the synergistic action of CO2 and nisin occurs at the cytoplasmic membrane...

  14. Inhibition of Listeria monocytogenes by fatty acids and monoglycerides.

    OpenAIRE

    Wang, L. L.; Johnson, E. A.

    1992-01-01

    Fatty acids and monoglycerides were evaluated in brain heart infusion broth and in milk for antimicrobial activity against the Scott A strain of Listeria monocytogenes. C12:0, C18:3, and glyceryl monolaurate (monolaurin) had the strongest activity in brain heart infusion broth and were bactericidal at 10 to 20 micrograms/ml, whereas potassium (K)-conjugated linoleic acids and C18:2 were bactericidal at 50 to 200 micrograms/ml. C14:0, C16:0, C18:0, C18:1, glyceryl monomyristate, and glyceryl m...

  15. Genetic dissection of DivIVA functions in Listeria monocytogenes.

    Science.gov (United States)

    Kaval, Karan Gautam; Hauf, Samuel; Rismondo, Jeanine; Hahn, Birgitt; Halbedel, Sven

    2017-10-02

    DivIVA is a membrane binding protein that clusters at curved membrane regions such as the cell poles and the membrane invaginations occurring during cell division. DivIVA proteins recruit many other proteins to these subcellular sites through direct protein-protein interactions. DivIVA-dependent functions are typically associated with cell growth and division, even though species-specific differences in the spectrum of DivIVA functions and their causative interaction partners exist. DivIVA from the Gram-positive human pathogen Listeria monocytogenes has at least three different functions. In this bacterium, DivIVA is required for precise positioning of the septum at mid-cell, it contributes to secretion of autolysins required for breakdown of peptidoglycan at the septum after completion of cell division, and it is essential for flagellar motility. While the DivIVA interaction partners for control of division site selection are well-established, the proteins connecting DivIVA with autolysin secretion or swarming motility are completely unknown. We set out to identify divIVA alleles, in which these three DivIVA functions could be separated, since the question of the degree to which the three functions of L. monocytogenes DivIVA are interlinked could not be answered before. Here, we identify such alleles, and our results show that division site selection, autolysin secretion, and swarming represent three discrete pathways that are independently influenced by DivIVA. These findings provide the required basis for the identification of DivIVA interaction partners controlling autolysin secretion and swarming in the future.IMPORTANCE DivIVA of the pathogenic bacterium Listeria monocytogenes is a central scaffold protein that influences at least three different cellular processes, namely cell division, protein secretion and bacterial motility. How DivIVA coordinates these rather unrelated processes is not known. We here identify variants of L. monocytogenes DivIVA, in which

  16. Listeria monocytogenes HAZARD MANAGEMENT IN A TYPICAL PRODUCT: THE CIAUSCOLO

    Directory of Open Access Journals (Sweden)

    S Fisichella

    2013-02-01

    Full Text Available The aim of the present study is to investigate operative procedures that allow to minimize Listeria monocytogenes (L. m. hazard in the main traditional sausage of the internal areas of Marche (Italy: the Ciauscolo, that has received the quality trademark PGI. It is made from lean cuts of well mature pork that is finely minced, adding fat which give the salami his characteristic softness and flavour. It is characterized by having a very little maturing period that determine high aw levels and, for this peculiarity, it allows L. m development.

  17. Patogénesis de Listeria monocytogenes, microorganismo zoonotico emergente

    OpenAIRE

    Kirvis Torres; Sara Sierra; Raúl Poutou; Ana Carrascal; Marcela Mercado

    2005-01-01

    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 ...

  18. Removal of viable bacteria and endotoxins by Electro Deionization (EDI).

    Science.gov (United States)

    Harada, Norimitsu; Otomo, Teruo; Watabe, Tomoichi; Ase, Tomonobu; Takemura, Takuto; Sato, Toshio

    2011-09-01

    Viable bacteria and endotoxins in water sometimes cause problems for human health. Endotoxins are major components of the outer cell wall of gram-negative bacteria (lipopolysaccharides). In medical procedures, especially haemodialysis (HD) and related therapies (haemodiafiltration (HDF), haemofiltration (HF)), endotoxins in the water for haemodialysis can permeate through the haemodialysis membrane and cause microinflammation or various haemodialysis-related illnesses. To decrease such a biological risk, RO and UF membranes are generally used. Also, hot water disinfection or the chemical disinfection is regularly executed to kill bacteria which produce endotoxins. However, simple treatment methods and equipment may be able to decrease the biological risk more efficiently. In our experiments, we confirmed that viable bacteria and endotoxins were removed by Electro Deionization (EDI) technology and also clarified the desorption mechanisms.

  19. Effectiveness of washing procedures in reducing Salmonella enterica and Listeria monocytogenes on a raw leafy green vegetable (Eruca vescicaria.

    Directory of Open Access Journals (Sweden)

    Alessandra Pezzuto

    2016-10-01

    Full Text Available Vegetables are an important source of nutrients, but they can host a large microbial population, particularly bacteria. Vegetables are an important source of nutrients, but they can host a large microbial population, particularly bacteria. Foodborne pathogens can contaminate raw vegetables at any stage of their production process with a potential for human infection. Appropriate washing can mitigate the risk of foodborne illness consequent to vegetable consumption by reducing pathogen levels, but few data are available to assess the efficacy of different practices. In the present work, six different washing methods, in the presence or absence of sanitisers (peracetic acid and percitric acid, sodium bicarbonate, sodium hypochlorite and vinegar, were tested for their effectiveness in reducing Salmonella and Listeria counts after artificial contamination of raw rocket (Eruca vescicaria. Results showed that washing with sodium hypochlorite (200 mg/L was the only method able to produce a significant 2 Log reduction of Salmonella counts, but only in the case of high initial contamination (7 Log CFU/g, suggesting potential harmful effects for consumers could occur. In the case of Listeria monocytogenes, all the examined washing methods were effective, with 200 mg/L sodium hypochlorite solution and a solution of peracetic and percitric acids displaying the best performances (2 and 1.5 Log reductions, respectively. This highlights the importance of targeting consumers on fit for purpose and safe washing practices to circumvent vegetable contamination by foodborne pathogens.

  20. Viable Options a Shipper has in Using Different Logistic Solutions

    OpenAIRE

    Grevesmühl, Vasco; Chehreh, Reza

    2013-01-01

    The research question explores the viable options a shipper has in using different logistic solutions. An investigation was conducted by first understanding the different provider levels based on their activities and then differentiate the logistic solutions based on attributes that are important for a shipper in their supply chain. These attributes were; organization, information technology (IT), flexibility and transportation quality aspects. Once the investigation was done, it was applied ...

  1. Viable Legionella Pneumophila Not Detectable by Culture on Agar Media

    Science.gov (United States)

    1987-09-01

    UNIT ELEMENT NO. NO. NO. ACCESSION NO. , N/A 1 1. TITLE (JIncJuue Security Ciaisuicarlon) Viable Legionella Pneumophila not Detectable by Culture on...106 cells-𔄁. Legionella have others. To study this loss of culturability, been sliown to vary in an tigenic composition, virulence L. pneumophila ...COSATICODES 18. SUBJECT TERMS (Continue on reverse if necessary and identify by block number) GROUP SUB-GROUP LEGIONELLA FLUORESCENT ANTIBODY

  2. A New Class of Cosmologically `Viable' $f(R)$ Models

    CERN Document Server

    Kumar, Rohin

    2016-01-01

    Instead of assuming a form of gravity and demand cosmology fit with $\\Lambda CDM$, a potentially `viable' $f(R)$ gravity model is derived assuming an alternative model of cosmology. Taking the `designer' approach to $f(R)$, a new class of solutions are derived starting with linear coasting cosmology in which scale factor linearly increases with time during matter domination. The derived forms of $f(R)$ are presented as result.

  3. Make My Trip Count 2015

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — The Make My Trip Count (MMTC) commuter survey, conducted in September and October 2015 by GBA, the Pittsburgh 2030 District, and 10 other regional transportation...

  4. Potential Bio-Control Agent from Rhodomyrtus tomentosa against Listeria monocytogenes

    Directory of Open Access Journals (Sweden)

    Grace Fiyinfoluwa Odedina

    2015-09-01

    Full Text Available Listeria monocytogenes is an important foodborne pathogen implicated in many outbreaks of listeriosis. This study aimed at screening for the potential use of Rhodomyrtus tomentosa ethanolic leaf extract as a bio-control agent against L. monocytogenes. Twenty-two L. monocytogenes isolates were checked with 16 commercial antibiotics and isolates displayed resistance to 10 antibiotics. All the tested isolates were sensitive to the extract with inhibition zones ranging from 14 to 16 mm. Minimum inhibitory concentration (MIC and minimum bactericidal concentration (MBC values ranged from 16 to 32 µg/mL and 128 to 512 µg/mL, respectively. Time-kill assay showed that the extract had remarkable bactericidal effects on L. monocytogenes. The extract at a concentration of 16 µg/mL reduced tolerance to 10% NaCl in L. monocytogenes in 4 h. Stationary phase L. monocytogenes cells were rapidly inactivated by greater than 3-log units within 30 min of contact time with R. tomentosa extract at 128 µg/mL. Electron microscopy revealed fragmentary bacteria with changes in the physical and morphological properties. Our study demonstrates the potential of the extract for further development into a bio-control agent in food to prevent the incidence of L. monocytogenes contamination.

  5. 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.

  6. Ultra deep sequencing of Listeria monocytogenes sRNA transcriptome revealed new antisense RNAs.

    Directory of Open Access Journals (Sweden)

    Sebastian Behrens

    Full Text Available Listeria monocytogenes, a gram-positive pathogen, and causative agent of listeriosis, has become a widely used model organism for intracellular infections. Recent studies have identified small non-coding RNAs (sRNAs as important factors for regulating gene expression and pathogenicity of L. monocytogenes. Increased speed and reduced costs of high throughput sequencing (HTS techniques have made RNA sequencing (RNA-Seq the state-of-the-art method to study bacterial transcriptomes. We created a large transcriptome dataset of L. monocytogenes containing a total of 21 million reads, using the SOLiD sequencing technology. The dataset contained cDNA sequences generated from L. monocytogenes RNA collected under intracellular and extracellular condition and additionally was size fractioned into three different size ranges from 150 nt. We report here, the identification of nine new sRNAs candidates of L. monocytogenes and a reevaluation of known sRNAs of L. monocytogenes EGD-e. Automatic comparison to known sRNAs revealed a high recovery rate of 55%, which was increased to 90% by manual revision of the data. Moreover, thorough classification of known sRNAs shed further light on their possible biological functions. Interestingly among the newly identified sRNA candidates are antisense RNAs (asRNAs associated to the housekeeping genes purA, fumC and pgi and potentially their regulation, emphasizing the significance of sRNAs for metabolic adaptation in L. monocytogenes.

  7. Ultra Deep Sequencing of Listeria monocytogenes sRNA Transcriptome Revealed New Antisense RNAs

    Science.gov (United States)

    Behrens, Sebastian; Widder, Stefanie; Mannala, Gopala Krishna; Qing, Xiaoxing; Madhugiri, Ramakanth; Kefer, Nathalie; Mraheil, Mobarak Abu; Rattei, Thomas; Hain, Torsten

    2014-01-01

    Listeria monocytogenes, a gram-positive pathogen, and causative agent of listeriosis, has become a widely used model organism for intracellular infections. Recent studies have identified small non-coding RNAs (sRNAs) as important factors for regulating gene expression and pathogenicity of L. monocytogenes. Increased speed and reduced costs of high throughput sequencing (HTS) techniques have made RNA sequencing (RNA-Seq) the state-of-the-art method to study bacterial transcriptomes. We created a large transcriptome dataset of L. monocytogenes containing a total of 21 million reads, using the SOLiD sequencing technology. The dataset contained cDNA sequences generated from L. monocytogenes RNA collected under intracellular and extracellular condition and additionally was size fractioned into three different size ranges from 150 nt. We report here, the identification of nine new sRNAs candidates of L. monocytogenes and a reevaluation of known sRNAs of L. monocytogenes EGD-e. Automatic comparison to known sRNAs revealed a high recovery rate of 55%, which was increased to 90% by manual revision of the data. Moreover, thorough classification of known sRNAs shed further light on their possible biological functions. Interestingly among the newly identified sRNA candidates are antisense RNAs (asRNAs) associated to the housekeeping genes purA, fumC and pgi and potentially their regulation, emphasizing the significance of sRNAs for metabolic adaptation in L. monocytogenes. PMID:24498259

  8. Gravitational Waves in Viable f(R) Models

    CERN Document Server

    Yang, Louis; Geng, Chao-Qiang

    2011-01-01

    We study gravitational waves in viable $f(R)$ theories under a non-zero background curvature. In general, an $f(R)$ theory contains an extra scalar degree of freedom corresponding to a massive scalar mode of gravitational wave. For viable $f(R)$ models, since there always exits a de-Sitter point where the background curvature in vacuum is non-zero, the mass squared of the scalar mode of gravitational wave is about the de-Sitter point curvature $R_{d}\\sim10^{-66}eV^{2}$. We illustrate our results in two types of viable $f(R)$ models: the exponential gravity and Starobinsky models. In both cases, the mass will be in the order of $10^{-33}eV$ when it propagates in vacuum. However, in the presence of matter density in galaxy, the scalar mode can be heavy. Explicitly, in the exponential gravity model, the mass becomes almost infinity, implying the disappearance of the scalar mode of gravitational wave, while the Starobinsky model gives the lowest mass around $10^{-24}eV$, corresponding to the lowest frequency of $...

  9. Gravitational waves in viable f(R) models

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Louis; Lee, Chung-Chi; Geng, Chao-Qiang, E-mail: louis.lineage@msa.hinet.net, E-mail: geng@phys.nthu.edu.tw, E-mail: g9522545@oz.nthu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu 300, Taiwan (China)

    2011-08-01

    We study gravitational waves in viable f(R) theories under a non-zero background curvature. In general, an f(R) theory contains an extra scalar degree of freedom corresponding to a massive scalar mode of gravitational wave. For viable f(R) models, since there always exits a de-Sitter point where the background curvature in vacuum is non-zero, the mass squared of the scalar mode of gravitational wave is about the de-Sitter point curvature R{sub d} ∼ 10{sup −66}eV{sup 2}. We illustrate our results in two types of viable f(R) models: the exponential gravity and Starobinsky models. In both cases, the mass will be in the order of 10{sup −33}eV when it propagates in vacuum. However, in the presence of matter density in galaxy, the scalar mode can be heavy. Explicitly, in the exponential gravity model, the mass becomes almost infinity, implying the disappearance of the scalar mode of gravitational wave, while the Starobinsky model gives the lowest mass around 10{sup −24}eV, corresponding to the lowest frequency of 10{sup −9} Hz, which may be detected by the current and future gravitational wave probes, such as LISA and ASTROD-GW.

  10. A new viable region of the inert doublet model

    CERN Document Server

    Lopez-Honorez, Laura

    2010-01-01

    The inert doublet model, a minimal extension of the Standard Model by a second Higgs doublet, is one of the simplest and most attractive scenarios that can explain the dark matter. In this paper, we demonstrate the existence of a new viable region of the inert doublet model featuring dark matter masses between Mw and about 160 GeV. Along this previously overlooked region of the parameter space, the correct relic density is obtained thanks to cancellations between different diagrams contributing to dark matter annihilation into gauge bosons (W+W- and ZZ). First, we explain how these cancellations come about and show several examples illustrating the effect of the parameters of the model on the cancellations themselves and on the predicted relic density. Then, we perform a full scan of the new viable region and analyze it in detail by projecting it onto several two-dimensional planes. Finally, the prospects for the direct and the indirect detection of inert Higgs dark matter within this new viable region are st...

  11. Detecting and measuring small numbers of viable Coxiella burnetii.

    Science.gov (United States)

    Lockhart, Michelle; Islam, Aminul; Graves, Stephen; Fenwick, Stan; Stenos, John

    2012-02-01

    Coxiella burnetii is an acidophilic, intracellular bacterium that causes the human disease Q fever. In some studies, it is important to distinguish between viable and nonviable C. burnetii. We compared four methods for detecting and measuring viable C. burnetii in biological samples as follows: growth in two different cell culture lines, infection of severe combined immunodeficient (SCID) mice (leading to death) and infection of SCID mice with detection of C. burnetii in their spleen (after euthanasia at day 50 postinfection). Two isolates of C. burnetii were used ('Henzerling' and 'Arandale'). Our in-house qPCR assay for C. burnetii DNA was used as a control. SCID mouse inoculation was more sensitive than cell culture. The assay that detected C. burnetii in SCID mouse spleens was slightly more sensitive than SCID mice deaths alone. Approximately one viable C. burnetii cell could be detected by this method, making it suitable for determining the viability of C. burnetii in a sample. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

  12. The Mayan Long Count Calendar

    OpenAIRE

    Chanier, Thomas

    2015-01-01

    The Maya were known for their astronomical proficiency. This is demonstrated in the Mayan codices where ritual practices were related to astronomical events/predictions. Whereas Mayan mathematics were based on a vigesimal system, they used a different base when dealing with long periods of time, the Long Count Calendar (LCC), composed of different Long Count Periods: the Tun of 360 days, the Katun of 7200 days and the Baktun of 144000 days. There were two other calendars used in addition to t...

  13. Counting Word Frequencies with Python

    Directory of Open Access Journals (Sweden)

    William J. Turkel

    2012-07-01

    Full Text Available Your list is now clean enough that you can begin analyzing its contents in meaningful ways. Counting the frequency of specific words in the list can provide illustrative data. Python has an easy way to count frequencies, but it requires the use of a new type of variable: the dictionary. Before you begin working with a dictionary, consider the processes used to calculate frequencies in a list.

  14. Comparison of Widely Used Listeria monocytogenes Strains EGD, 10403S, and EGD-e Highlights Genomic Differences Underlying Variations in Pathogenicity

    Science.gov (United States)

    Bécavin, Christophe; Bouchier, Christiane; Lechat, Pierre; Archambaud, Cristel; Creno, Sophie; Gouin, Edith; Wu, Zongfu; Kühbacher, Andreas; Brisse, Sylvain; Pucciarelli, M. Graciela; García-del Portillo, Francisco; Hain, Torsten; Portnoy, Daniel A.; Chakraborty, Trinad; Lecuit, Marc; Pizarro-Cerdá, Javier; Moszer, Ivan; Bierne, Hélène; Cossart, Pascale

    2014-01-01

    ABSTRACT For nearly 3 decades, listeriologists and immunologists have used mainly three strains of the same serovar (1/2a) to analyze the virulence of the bacterial pathogen Listeria monocytogenes. The genomes of two of these strains, EGD-e and 10403S, were released in 2001 and 2008, respectively. Here we report the genome sequence of the third reference strain, EGD, and extensive genomic and phenotypic comparisons of the three strains. Strikingly, EGD-e is genetically highly distinct from EGD (29,016 single nucleotide polymorphisms [SNPs]) and 10403S (30,296 SNPs), and is more related to serovar 1/2c than 1/2a strains. We also found that while EGD and 10403S strains are genetically very close (317 SNPs), EGD has a point mutation in the transcriptional regulator PrfA (PrfA*), leading to constitutive expression of several major virulence genes. We generated an EGD-e PrfA* mutant and showed that EGD behaves like this strain in vitro, with slower growth in broth and higher invasiveness in human cells than those of EGD-e and 10403S. In contrast, bacterial counts in blood, liver, and spleen during infection in mice revealed that EGD and 10403S are less virulent than EGD-e, which is itself less virulent than EGD-e PrfA*. Thus, constitutive expression of PrfA-regulated virulence genes does not appear to provide a significant advantage to the EGD strain during infection in vivo, highlighting the fact that in vitro invasion assays are not sufficient for evaluating the pathogenic potential of L. monocytogenes strains. Together, our results pave the way for deciphering unexplained differences or discrepancies in experiments using different L. monocytogenes strains. PMID:24667708

  15. Growth kinetics of Listeria monocytogenes and spoilage microorganisms in fresh-cut cantaloupe.

    Science.gov (United States)

    Fang, Ting; Liu, Yanhong; Huang, Lihan

    2013-05-01

    The main objective of this study was to investigate the growth kinetics of Listeria monocytogenes and background microorganisms in fresh-cut cantaloupe. Fresh-cut cantaloupe samples, inoculated with three main serotypes (1/2a, 1/2b, and 4b) of L. monocytogenes, were incubated at different temperatures, ranging from 4 to 43 °C, to develop kinetic growth models. During storage studies, the population of both background microorganisms and L. monocytogenes began to increase almost immediately, with little or no lag phase for most growth curves. All growth curves, except for two growth curves of L. monocytogenes 1/2a at 4 °C, developed to full curves (containing exponential and stationary phases), and can be described by a 3-parameter logistic model. There was no significant difference (P = 0.28) in the growth behaviors and the specific growth rates of three different serotypes of L. monocytogenes inoculated to fresh-cut cantaloupe. The effect of temperature on the growth of L. monocytogenes and spoilage microorganisms was evaluated using three secondary models. For L. monocytogenes, the minimum and maximum growth temperatures were estimated by both the Ratkowsky square-root and Cardinal parameter models, and the optimum temperature and the optimum specific growth rate by the Cardinal parameter model. An Arrhenius-type model provided more accurate estimation of the specific growth rate of L. monocytogenes at temperatures <4 °C. The kinetic models developed in this study can be used by regulatory agencies and food processors for conducting risk assessment of L. monocytogenes in fresh-cut cantaloupe, and for estimating the shelf-life of fresh-cut products.

  16. Comparative evaluation of the VIDAS Listeria monocytogenes Xpress (LMX) for the detection of Listeria monocytogenes in a variety of foods.

    Science.gov (United States)

    Johnson, Ronald; Mills, John; Pittet, Jean-Louis; Hughes, Denise

    2013-01-01

    The VIDAS Listeria monocytogenes Xpress (LMX) test is an enzyme-linked fluorescent immunoassay designed for use with the automated VIDAS or mini-VIDAS instruments for the specific detection of L. monocytogenes using a 26 h proprietary enrichment broth. The VIDAS LMX method was validated according to harmonized AOAC Research Institute (RI) and Official Methods of Analysis guidelines in both the AOAC Performance Tested Method (PTM) and GovVal programs. In the PTM comparison studies, the VIDAS LMX method was compared to the U.S. Department of Agriculture-Food Safety and Inspection Service Microbiology Laboratory Guidebook, the U.S. Food and Drug Administration Bacteriological Analytical Manual, and AOAC Official Methods. The comparative food studies consisted of two main parts: internal testing and AOAC independent laboratory testing, which included seven food matrixes (deli ham, processed cheese, vanilla ice cream, cooked shrimp, smoked white fish, frozen spinach, and peanut butter). As part of the AOAC R1 GovVal program, the VIDAS LMX method was compared to the Health Canada MFHPB-30 method for the detection of L. monocytogenes in five ready-to-eat (RTE) meats (hot dogs, deli turkey, deli ham, fermented sausage, and liver paté). Twenty replicates of each inoculation level and five uninoculated controls were evaluated in each study. The LMX method also included the use ofchromogenic media, chromID Ottaviani Agosti agar and chromID L. mono. agar, for confirmation of LMX presumptive results. In both the PTM and GovVal evaluations, there were no significant differences in the Chi-square values for the LMX method when compared to reference methods. The additional parameters tested in the PTM evaluation (inclusivity, exclusivity, ruggedness, stability, and lot-to-lot) satisfied the AOAC RI performance requirements. In both the PTM and GovVal validation studies, the VIDAS LMX method demonstrated reliability as a rapid qualitative method for next-day detection of L

  17. 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.

  18. MHC class Jb-restricted cell responses to Listeria monocytogenes infection.

    Science.gov (United States)

    Kerksiek, K M; Pamer, E G

    1999-12-01

    Murine infection with Listeria monocytogenes induces CD8+ T cell responses specific for bacterial peptides that are presented on the infected cell surface by MHC class Ia and MHC class Ib molecules. We have used MHC tetramers to demonstrate that CD8+ T cells restricted by the H2-M3 MHC class Ib molecules constitute a substantial portion of the T cell response to L. monocytogenes infection. The in vivo size and kinetics of MHC class Ib-restricted T cell populations suggests that they play a prominent role in bacterial clearance following primary L. monocytogenes infection.

  19. 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

    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...... typing, pulsed-field gel electrophoresis and ribotyping revealed 62 different clones. Based upon typability and discriminatory power, DNA typing methods used were found equally suitable as epidemiological markers. Serotyping and phage typing were not found useful as epidemiological markers for poultry...

  20. Sigma B Contributes to PrfA-Mediated Virulence in Listeria monocytogenes

    OpenAIRE

    Nadon, Celine A.; Bowen, Barbara M.; Wiedmann, Martin; Boor, Kathryn J.

    2002-01-01

    Transcription of the Listeria monocytogenes positive regulatory factor A protein (PrfA) is initiated from either of two promoters immediately upstream of prfA (prfAp1 and prfAp2) or from the upstream plcA promoter. We demonstrate that prfAp2 is a functional σB-dependent promoter and that a sigB deletion mutation affects the virulence phenotype of L. monocytogenes. Thus, the alternative sigma factor σB contributes to virulence in L. monocytogenes.

  1. Incidence and characterization of Listeria monocytogenes in foods available in Taiwan.

    OpenAIRE

    Wong, H. C.; Chao, W L; Lee, S. J.

    1990-01-01

    A variety of foods were examined for the incidence of Listeria monocytogenes, and the bacterial isolates were further characterized. L. monocytogenes was selected on LiCl-phenylethanol-moxalactam agar after enrichments and identified by several biochemical, mobility, and CAMP tests. L. monocytogenes was isolated from 58.8% of pork samples, 50% of chicken carcasses, 38% of turkey parts, 34% of frozen semiready foods, 24% of beef steaks, 12.2% of vegetables, 10.5% of seafoods, and 4.4% of froze...

  2. Listeria monocytogenes Infection in a Sugar Glider (Petaurus breviceps) - New Mexico, 2011.

    Science.gov (United States)

    Nichols, M; Takacs, N; Ragsdale, J; Levenson, D; Marquez, C; Roache, K; Tarr, C L

    2015-06-01

    Listeria monocytogenes is a Gram-positive, facultative anaerobic, rod-shaped bacterium that can infect and cause disease in many species. In this case report, we describe a case of L. monocytogenes infection causing sepsis in a sugar glider (Petaurus breviceps). The sugar glider consumed a varied diet consisting of human food items, including cantaloupe. A nationwide outbreak of L. monocytogenes foodborne illness associated with cantaloupes occurred simultaneously with this incident case. In this case, the bacterial strains from the outbreak and glider were genetically distinct. Although rare, veterinarians should be aware of the emergence of foodborne pathogens' ability to infect exotic animals residing in domestic environments.

  3. Bacteriophage predation promotes serovar diversification in Listeria monocytogenes.

    Science.gov (United States)

    Eugster, Marcel R; Morax, Laurent S; Hüls, Vanessa J; Huwiler, Simona G; Leclercq, Alexandre; Lecuit, Marc; Loessner, Martin J

    2015-07-01

    Listeria monocytogenes is a bacterial pathogen classified into distinct serovars (SVs) based on somatic and flagellar antigens. To correlate phenotype with genetic variation, we analyzed the wall teichoic acid (WTA) glycosylation genes of SV 1/2, 3 and 7 strains, which differ in decoration of the ribitol-phosphate backbone with N-acetylglucosamine (GlcNAc) and/or rhamnose. Inactivation of lmo1080 or the dTDP-l-rhamnose biosynthesis genes rmlACBD (lmo1081-1084) resulted in loss of rhamnose, whereas disruption of lmo1079 led to GlcNAc deficiency. We found that all SV 3 and 7 strains actually originate from a SV 1/2 background, as a result of small mutations in WTA rhamnosylation and/or GlcNAcylation genes. Genetic complementation of different SV 3 and 7 isolates using intact alleles fully restored a characteristic SV 1/2 WTA carbohydrate pattern, including antisera reactions and phage adsorption. Intriguingly, phage-resistant L. monocytogenes EGDe (SV 1/2a) isolates featured the same glycosylation gene mutations and were serotyped as SV 3 or 7 respectively. Again, genetic complementation restored both carbohydrate antigens and phage susceptibility. Taken together, our data demonstrate that L. monocytogenes SV 3 and 7 originate from point mutations in glycosylation genes, and we show that phage predation represents a major driving force for serovar diversification and evolution of L. monocytogenes.

  4. Identification of Listeria monocytogenes on Green Mussels and Cockle Shell

    Directory of Open Access Journals (Sweden)

    Winiati Puji Rahayu

    2017-02-01

    Full Text Available AbstractGreen mussel (Perna viridis and cockle shell (Anadara granosa are one of many sources of animal protein which is many cultivated in Indonesia because their price is relatively affordable. This study was conducted to identify the presence of Listeria monocytogenes in 27 samples of green mussels and 3 samples of cockle shells using real-time Polymerase Chain Reaction (real-time PCR and biochemical methods. The target gene for amplification in real-time PCR was an hlyA gene because this gene was a determinant of virulence genes that produce listeriolysin O. Primers used in this study were forward primer DG69 (GTG CCG GGT AAA AGA CCA TA and reverse primer DG74 (CGC CAC TGA GAT ACT AT and fluorescence signals indicator using SYBR Green I. The results of analysis using real-time PCR were negative Listeria monocytogenes in all samples, while using biochemical methods there was one of 30 samples contaminated by Listeria welshimeri.

  5. Effects of bilimbi (Averrhoa bilimbi L.) and tamarind (Tamarindus indica L.) juice on Listeria monocytogenes Scott A and Salmonella Typhimurium ATCC 14028 and the sensory properties of raw shrimps.

    Science.gov (United States)

    Norhana, M N Wan; Azman, Mohd Nor A; Poole, Susan E; Deeth, Hilton C; Dykes, Gary A

    2009-11-30

    The potential of using juice of bilimbi (Averrhoa bilimbi L.) and tamarind (Tamarindus indica L.) to reduce Listeria monocytogenes Scott A and Salmonella Typhimurium ATCC 14028 populations on raw shrimps after washing and during storage (4 degrees C) was investigated. The uninoculated raw shrimps and those inoculated with approximately 9 log cfu/ml of L. monocytogenes Scott A and S. Typhimurium ATCC 14028 were washed (dipped or rubbed) in distilled water (SDW) (control), bilimbi or tamarind juice at 1:4 (w/v) concentrations for 10 and 5 min. Naturally occurring aerobic bacteria (APC), L. monocytogenes Scott A and S. Typhimurium ATCC 14028 counts, pH values and sensory analysis of washed shrimps were determined immediately after washing (day 0), and on days 3 and 7 of storage. Compared to SDW, bilimbi and tamarind juice significantly (p0.05) throughout the storage except for odour (plemony smell was noticed in bilimbi- and tamarind-washed shrimps and not in control shrimps.

  6. Molecular Serotyping and Pathogenic Potential of Listeria monocytogenes Isolated from Milk and Milk Products in Tamil Nadu, India.

    Science.gov (United States)

    Karthikeyan, Raman; Gunasekaran, Paramasamy; Rajendhran, Jeyaprakash

    2015-06-01

    Listeria monocytogenes, an important bacterial pathogen, is responsible for foodborne illnesses worldwide. Examination of food samples for the presence of L. monocytogenes and assessment of their pathogenicity is usually an effective strategy in the prevention of listeriosis. In the present study, we have tested 307 samples of milk and milk products from various places in Tamil Nadu, India for the presence of L. monocytogenes using ISO 11290 and U.S. Food and Drug Administration Bacteriological Analytical Manual methods. 16S rDNA sequencing and duplex polymerase chain reaction (PCR) analysis for prs and iap genes were used to identify L. monocytogenes at the species level. Fifteen of the 307 samples screen tested positive for L. monocytogenes. Molecular serotyping of the L. monocytogenes isolates by multiplex PCR revealed the predominance of the serogroups 1/2a and 4b. Fourteen of the 15 isolates contained all the virulence genes (inlA, inlB, hlyA, and plcA) screened for using multiplex PCR. Only one isolate of L. monocytogenes was negative for the plcA gene and in vitro phosphatidylinositol-phospholipase C activity. L. monocytogenes strains that belong to the serogroup 4b exhibited higher nematocidal activity against Caenorhabditis elegans than the serogroup 1/2a. Worms infected with L. monocytogenes were symptomatic with aberrant contraction of body muscles, loss of pharyngeal pumping, and decreased locomotion, which highlights the pathogenic potential of the L. monocytogenes isolates.

  7. The effects of X-ray radiation on Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri inoculated on whole Roma tomatoes.

    Science.gov (United States)

    Mahmoud, Barakat S M

    2010-12-01

    In the last two decades several foodborne disease outbreaks associated with produce were reported. Tomatoes, in particular, have been associated with several multi-state Salmonella outbreaks. Inactivation of inoculated Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri on whole Roma tomato surfaces by X-ray at 0.1, 0.5, 0.75, 1.0, and 1.5 kGy was studied. The main purpose of this study was to achieve a 5 log reduction in consistent with the recommendations of the National Advisory Committee on Microbiological Criteria for Foods. Moreover, the effect of X-ray on inherent microflora (mesophilic counts, psychrotrophic counts and yeast and mold counts) of untreated and treated Roma tomatoes, during storage at ambient temperature (22°C) for 20 days was also determined. Mixtures of three or two strains of each tested organism was spot inoculated (100 μl) onto the surface of Roma tomatoes (approximately 7-9 log per tomato), separately, and air-dried, followed by treatment with X-ray doses at 22°C and 55-60% relative humidity. Surviving bacterial populations on tomato surfaces were evaluated using a nonselective medium (tryptic soy agar) with a selective medium overlay for each bacteria; E. coli O157:H7 (CT-SMAC agar), L. monocytogenes (MOA), and S. enterica and S. flexneri (XLD). Treatment with X-ray significantly reduced the population of the tested pathogens on whole Roma tomato surfaces, compared with the control. Approximately 4.2, 2.3, 3.7 and 3.6 log CFU reduction of E. coli O157:H7, L. monocytogenes, S. enterica and S. flexneri per tomato were achieved by treatment with 0.75 kGy X-ray, respectively. More than a 5 log CFU reduction per tomato was achieved at 1.0 or 1.5 kGy X-ray for all tested pathogens. Furthermore, treatment with X-ray significantly reduced the inherent microflora on Roma tomatoes. Inherent levels were significantly (p<0.05) lower than the control sample throughout storage for 20 days.

  8. Enumeration of viable non-culturable Vibrio cholerae using propidium monoazide combined with quantitative PCR.

    Science.gov (United States)

    Wu, Bin; Liang, Weili; Kan, Biao

    2015-08-01

    The well-known human pathogenic bacterium, Vibrio cholerae, can enter a physiologically viable but non-culturable (VBNC) state under stress conditions. The differentiation of VBNC cells and nonviable cells is essential for both disease prevention and basic research. Among all the methods for detecting viability, propidium monoazide (PMA) combined with real-time PCR is popular because of its specificity, sensitivity, and speed. However, the effect of PMA treatment is not consistent and varies among different species and conditions. In this study, with an initial cell concentration of 1×10(8) CFU/ml, time and dose-effect relationships of different PMA treatments were evaluated via quantitative real-time PCR using live cell suspensions, dead cell suspensions and VBNC cell suspensions of V. cholerae O1 El Tor strain C6706. The results suggested that a PMA treatment of 20 μM PMA for 20 min was optimal under our conditions. This treatment maximized the suppression of the PCR signal from membrane-compromised dead cells but had little effect on the signal from membrane-intact live cells. In addition to the characteristics of PMA treatment itself, the initial concentration of the targeted bacteria showed a significant negative influence on the stability of PMA-PCR assay in this study. We developed a strategy that mimicked a 1×10(8) CFU/ml cell concentration with dead bacteria of a different bacterial species, the DNA of which cannot be amplified using the real time PCR primers. With this strategy, our optimal approach successfully overcame the impact of low cell density and generated stable and reliable results for counting viable cells of V. cholerae in the VBNC state. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. [Evaluation of the effect of Lactobacillus rhamnosus probiotic culture added to yogurt over Staphylococcus aureus, Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enteritidis populations].

    Science.gov (United States)

    Calderón, Oscar; Padilla, Carolina; Chaves, Carolina; Villalobos, Laura; Arias, María Laura

    2007-03-01

    The effect of different types of probiotics present in yogurt over known populations of Staphylococcus aureus, Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enteritidis was evaluated. The three types of yogurt used were: without added probiotics, with added probiotics (Lactobacillus casei CRL_431 and L. acidophilus CRL_730 CHR HANSEN) and another one with the same probiotics mentioned above and Lactobacillus rhamnosus (LR-35) culture. About 10(9) CFU/ mL of each potentially pathogenic bacteria was added to each type of yogurt tested, and kept in refrigeration at 4 degrees C during its shelf life, about 30 days. Bacterial count was done the initial day and every four days. Results obtained show that there is a difference in the inhibition between yogurts without added probiotics and the commercial yogurt with added probiotics; there is a clear inhibitory effect of the last one over S. aureus, E. coli O157:H7 and Listeria monocytogenes. The yogurt with added probiotics and L. rhamnosus did not show any additional inhibitory effect over the bacteria tested when compared with the yogurt with added probiotics. S. enteritidis could not be evaluated because it was not detectable in any yogurt samples evaluated four days after its inoculation. This study confirms the antagonic effect of probiotic cultures over potentially pathogenic bacteria for human beings and animals that may be present in food. Nevertheless, the use of L. rhamnosus did not produce any additional inhibitory effect.

  10. Hanford whole body counting manual

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, H.E.; Rieksts, G.A.; Lynch, T.P.

    1990-06-01

    This document describes the Hanford Whole Body Counting Program as it is administered by Pacific Northwest Laboratory (PNL) in support of the US Department of Energy--Richland Operations Office (DOE-RL) and its Hanford contractors. Program services include providing in vivo measurements of internally deposited radioactivity in Hanford employees (or visitors). Specific chapters of this manual deal with the following subjects: program operational charter, authority, administration, and practices, including interpreting applicable DOE Orders, regulations, and guidance into criteria for in vivo measurement frequency, etc., for the plant-wide whole body counting services; state-of-the-art facilities and equipment used to provide the best in vivo measurement results possible for the approximately 11,000 measurements made annually; procedures for performing the various in vivo measurements at the Whole Body Counter (WBC) and related facilities including whole body counts; operation and maintenance of counting equipment, quality assurance provisions of the program, WBC data processing functions, statistical aspects of in vivo measurements, and whole body counting records and associated guidance documents. 16 refs., 48 figs., 22 tabs.

  11. Implementation of classical, molecular biological and immunoenzymatic methods in isolation and detection of Listeria monocytogenes in food

    Directory of Open Access Journals (Sweden)

    Lakićević Brankica Z.

    2014-01-01

    Full Text Available Food borne pathogens and spoilage bacteria are influencing the safety and quality of food and animal feed and can result in serious adverse effects to human and animal health as well as to the food quality. Consequently, microbiological quality control in the food industry has become the priority of the food producers and it aims towards minimizing the risks related to food pathogens and spoilage bacteria. One of the most important pathogens in the food industry is Listeria monocytogenes. Listeriosis has a significant public health and economic impact because of its high hospitalization and mortality rate. Most people infected with Listeria are hospitalized and mortality is approximately 30 %. Therefore it is necessary to undertake efficient control measures, especially concerning the necessity of a rapid and accurate detection of this pathogen in the food industry as well as in retail food samples. Recently used conventional methods are often time consuming and require intensive work. However, obtained results can often be false considering the presence of viable but not cultivable microorganisms. Advances in biotechnology and bioinformatics have resulted in the development of novel testing technologies that enable tracking, more reliable and faster detection of food pathogens. Furthermore, molecular-biology methods, although still not applied routinely in everyday practice, are the promising alternative which can replace current reference methods in this area.

  12. Inkjet printing of viable human dental follicle stem cells

    Directory of Open Access Journals (Sweden)

    Mau Robert

    2015-09-01

    Full Text Available Inkjet printing technology has the potential to be used for seeding of viable cells for tissue engineering approaches. For this reason, a piezoelectrically actuated, drop-on-demand inkjet printing system was applied to deliver viable human dental follicle stem cells (hDFSC of sizes of about 15 μm up to 20 μm in diameter. The purpose of these investigations was to verify the stability of the printing process and to evaluate cell viability post printing. Using a Nanoplotter 2.1 (Gesim, Germany equipped with the piezoelectric printhead NanoTip HV (Gesim, Germany, a concentration of 6.6 ×106 cells ml−1 in DMEM with 10% fetal calf serum (FCS could be dispensed. The piezoelectric printhead has a nominal droplet volume of ~ 400 pl and was set to a voltage of 75 V and a pulse of 50 μs while dosing 50 000 droplets over a time of 100 seconds. The volume and trajectory of the droplet were checked by a stroboscope test right before and after the printing process. It was found that the droplet volume decreases significantly by 35% during printing process, while the trajectory of the droplets remains stable with only an insignificant number of degrees deviation from the vertical line. It is highly probable that some cell sedimentations or agglomerations affect the printing performance. The cell viability post printing was assessed by using the Trypan Blue dye exclusion test. The printing process was found to have no significant influence on cell survival. In conclusion, drop-on-demand inkjet printing can be a potent tool for the seeding of viable cells.

  13. Comparative Evaluation of Veriflow® Listeria monocytogenes to USDA and AOAC Culture Based Methods for the Detection of Listeria monocytogenes in Food.

    Science.gov (United States)

    Joelsson, Adam C; Brown, Ashley S; Puri, Amrita; Keough, Martin P; Gaudioso, Zara E; Siciliano, Nicholas A; Snook, Adam E

    2015-01-01

    Veriflow® Listeria monocytogenes (LM) is a molecular based assay for the presumptive detection of Listeria monocytogenes from environmental surfaces, dairy, and ready-to-eat (RTE) food matrixes (hot dogs and deli meat). The assay utilizes a PCR detection method coupled with a rapid, visual, flow-based assay that develops in 3 min post PCR amplification and requires only 24 h of enrichment for maximum sensitivity. The Veriflow LM system eliminates the need for sample purification, gel electrophoresis, or fluorophore-based detection of target amplification, and does not require complex data analysis. This Performance Tested Method(SM) validation study demonstrated the ability of the Veriflow LM method to detect low levels of artificially inoculated L. monocytogenes in seven distinct environmental and food matrixes. In each unpaired reference comparison study, probability of detection analysis indicated no significant difference between the Veriflow LM method and the U.S. Department of Agriculture, Food Safety and Inspection Service Microbiology Laboratory Guidebook 8.08 or AOAC 993.12 reference method. Fifty strains of L. monocytogenes were detected in the inclusivity study, while 39 nonspecific organisms were undetected in the exclusivity study. The study results show that Veriflow LM is a sensitive, selective, and robust assay for the presumptive detection of L. monocytogenes sampled from environmental, dairy, or RTE (hot dogs and deli meat) food matrixes.

  14. Chitinolytic activity in viable spores of encephalitozoon species

    Directory of Open Access Journals (Sweden)

    Schottelius J

    2000-01-01

    Full Text Available By employing 4-methylumbelliferyl-beta-D-NN',N"-triacetylchitotriose substrate in a semi quantitative assay, chitinolytic activity in viable spores of Encephalitozoon cuniculi and E. intestinalis was detected and dependence on reaction time, spore concentration, concentration of substrate and temperature were demonstrated. It was possible to block the chitinolytic activity by chitin hydrolysate. By incubation at 80°C for 10 min or at 55°C for 20 min the spores were loosing the chitinolytic activity. Incubation of the spores in trypsin reduced the chitinolytic activity. Cellulase activity could not be detected.

  15. Molar Pregnancy with a Co-Existing Viable Fetus

    Directory of Open Access Journals (Sweden)

    Ruya Deveer

    2014-03-01

    Full Text Available     The aim of this study was to report the clinical features, management, and outcome of a case of molar pregnancy with a coexisting viable fetus and to review the literature. In this article, we report a case of pregnancy with diffuse placental molar change and a normal fetus which presented with hyperemesis gravidarum and hyperthyroidism. Genetic amniocentesis showed normal fetal karyotype. A healthy full-term live male infant was delivered by cesarean section. In molar pregnancies with a normal karyotype fetus, with intensive maternal follow-up, continuation of pregnancy can be suggested.

  16. Kit Tests for Rapid Detection of Viable Bacteria and Viruses.

    Science.gov (United States)

    1980-10-01

    34 ®,, LEYE V TŘ CHEMICAL SYSTEMS LABORATORY CONTRACTOR REPORTo ARCSL-CR-80064 KIT TESTS FOR RAPID DETECTION OF VIABLE BACTERIA AND VIRUSES Final Report by R.H...they are converted from colorless, water-soluble compounds to brightly colored insoluble precipitates on reduction. The reduced form remains at the...per test) Observation 0 no obvious change in 30 minutes 5 x 14trace color in 30 minutes 2 x 10 s trace color in 17 minutes, distinct in 30 minutes 5 x

  17. NATURAL ATYPICAL LISTERIA INNOCUA STRAINS WITH LISTERIA MONOCYTOGENES PATHOGENICITY ISLAND 1 GENES

    Science.gov (United States)

    The detection of the human foodborne pathogen, Listeria monocytogenes, in food, environmental samples and clinical specimens associated with cases of listeriosis, a rare but high mortality-rate disease, requires distinguishing the pathogen from other Listeria species. Speciation...

  18. Heat resistance of an outbreak strain of Listeria monocytogenes in hot dog batter.

    Science.gov (United States)

    Mazzotta, A S; Gombas, D E

    2001-03-01

    The heat resistance of a strain of Listeria monocytogenes responsible for a listeriosis outbreak in hot dogs was not higher than the heat resistance of other L. monocytogenes strains when tested in tryptic soy broth and in laboratory-prepared hot dog batter. For the thermal death time experiments, the cells were grown to stationary phase or were starved in phosphate-buffered saline, pH 7, for 6 h at 30 degrees C. Starvation increased the heat resistance of L. monocytogenes in broth but not in hot dog batter. D-values in hot dog batter were higher than in broth. For the hot dog formulation used in this study, cooking the hot dog batter for 30 s at 71.1 degrees C (160 degrees F), or its equivalent using a z-value of 6 degrees C (11 degrees F), would inactivate 5 logs of L. monocytogenes.

  19. 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.

  20. Visualization of gold and platinum nanoparticles interacting with Salmonella enteritidis and Listeria monocytogenes

    DEFF Research Database (Denmark)

    Sawosz, Ewa; Chwalibog, André; Szeliga, Jacek

    2010-01-01

    -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...... 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...

  1. Characteristics of the biologically active 35-kDa metalloprotease virulence factor from Listeria monocytogenes

    NARCIS (Netherlands)

    Coffey, A; van den Burg, B; Veltman, R; Abee, T

    Listeria monocytogenes, a facultative intracellular pathogen, synthesizes an extracellular protease which is responsible for the maturation of phosphatidylcholine phospholipase C (lecithinase), a virulence factor involved in cell-to-cell spread. This work describes the environmental parameters

  2. 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......-transporter permease) presented in the sequenced strain L. monocytogenes str. 4b F2365. This disrupted gene, denoted lm.G_1771, encoded a protein with 10 transmembrane helixes. The revertant, LM-49RE, was obtained by replacing lm.G_1771::Tn917 with lm.G_1771 via homologous recombination. We found that LM-49RE formed...

  3. Effects of ultraviolet-B exposure on the resistance to Listeria monocytogenes in the rat

    NARCIS (Netherlands)

    Goettsch W; Garssen J; de Klerk A; Herremans MMPT; Dortant P; de Gruijl FR; van Loveren H; LPI; VIR; UU

    1996-01-01

    Een Listeria monocytogenes infectiemodel in de rat werd gebruikt om de immuunsuppressieve activiteit van ultraviolet-B straling (UVB) te onderzoeken. Ratten werden dagelijks blootgesteld aan suberythemale hoeveelheden UVB straling gedurende 5 of 7 opeenvolgende dagen. Twee verschillende UV bronnen

  4. 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....

  5. 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.

  6. NATURAL ATYPICAL LISTERIA INNOCUA STRAINS WITH LISTERIA MONOCYTOGENES PATHOGENICITY ISLAND 1 GENES

    Science.gov (United States)

    The detection of the human foodborne pathogen, Listeria monocytogenes, in food, environmental samples and clinical specimens associated with cases of listeriosis, a rare but high mortality-rate disease, requires distinguishing the pathogen from other Listeria species. Speciation...

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

    Science.gov (United States)

    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 pat...

  8. Heat resistance of Listeria monocytogenes in vegetables: evaluation of blanching processes.

    Science.gov (United States)

    Mazzotta, A S

    2001-03-01

    The heat resistance of a Listeria monocytogenes composite (serotypes 1/2a, 1/2b, and 4b) was determined in fresh broccoli florets, sweet green peppers, onions, mushrooms, and peas using an end-point procedure in polyester pouches. The heat resistance of L. monocytogenes was higher in peas (D(60 degrees C) = 1.0 min) and mushrooms (D(60 degrees C) = 0.7 min) than in other vegetables tested (D(60 degrees C) in onions = 0.2 min) and was highest when cells were subjected to starvation before the thermal death time experiments (D(60 degrees C) of starved L. monocytogenes in mushrooms = 1.6 min). The results showed that blanching can be used as an antilisterial treatment (inactivation of 5 logs of L. monocytogenes) when the cold spot of vegetables is treated for at least 10 s at 75 degrees C or instantaneously (<1 s) at temperatures above 82 degrees C.

  9. Thermal inactivation of Listeria monocytogenes during rapid and slow heating in sous vide cooked beef.

    Science.gov (United States)

    Hansen, T B; Knøchel, S

    1996-06-01

    Heating at slowly rising temperatures is suspected to enhance thermotolerance in Listeria monocytogenes and, since anaerobic environments have been shown to facilitate resuscitation of heat-injured cells of this micro-organism, concern may arise about the possibility of L. monocytogenes surviving in minimally preserved products. The effect of rapid ( > 10 degrees C min-1) and slow (0.3 and 0.6 degrees C min-1) heating on survival of L. monocytogenes in sous vide cooked beef was therefore examined at mild processing temperatures of 56 degrees, 60 degrees and 64 degrees C. No statistically significant difference (P = 0.70) was observed between the tested heating regimes. Since the average pH of beef was low (5.6), and little or no effect was observed, a pH-dependency of heat shock-induced thermotolerance in L. monocytogenes is suggested to account for this result.

  10. Listeria monocytogenes Prevalence and Characteristics in Retail Raw Foods in China

    National Research Council Canada - National Science Library

    Wu, Shi; Wu, Qingping; Zhang, Jumei; Chen, Moutong; Yan, Ze An; Hu, Huijuan

    2015-01-01

    The prevalence and levels of Listeria monocytogenes in retail raw foods covering most provincial capitals in China were studied with testing of 1036 samples of vegetables, edible mushrooms, raw meat...

  11. VersaCount: customizable manual tally software for cell counting

    Directory of Open Access Journals (Sweden)

    DeRisi Joseph L

    2010-01-01

    Full Text Available Abstract Background The manual counting of cells by microscopy is a commonly used technique across biological disciplines. Traditionally, hand tally counters have been used to track event counts. Although this method is adequate, there are a number of inefficiencies which arise when managing large numbers of samples or large sample sizes. Results We describe software that mimics a traditional multi-register tally counter. Full customizability allows operation on any computer with minimal hardware requirements. The efficiency of counting large numbers of samples and/or large sample sizes is improved through the use of a "multi-count" register that allows single keystrokes to correspond to multiple events. Automatically updated multi-parameter values are implemented as user-specified equations, reducing errors and time required for manual calculations. The user interface was optimized for use with a touch screen and numeric keypad, eliminating the need for a full keyboard and mouse. Conclusions Our software provides an inexpensive, flexible, and productivity-enhancing alternative to manual hand tally counters.

  12. 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

  13. The Origins of Counting Algorithms

    OpenAIRE

    Cantlon, Jessica F.; Piantadosi, Steven T.; Ferrigno, Stephen; Hughes, Kelly D.; Allison M Barnard

    2015-01-01

    Humans’ ability to ‘count’ by verbally labeling discrete quantities is unique in animal cognition. The evolutionary origins of counting algorithms are not understood. We report that non-human primates exhibit a cognitive ability that is algorithmically and logically similar to human counting. Monkeys were given the task of choosing between two food caches. Monkeys saw one cache baited with some number of food items, one item at a time. Then, a second cache was baited with food items, one at a...

  14. Tree modules and counting polynomials

    CERN Document Server

    Kinser, Ryan

    2011-01-01

    We give a formula for counting tree modules for the quiver S_g with g loops and one vertex in terms of tree modules on its universal cover. This formula, along with work of Helleloid and Rodriguez-Villegas, is used to show that the number of d-dimensional tree modules for S_g is polynomial in g with the same degree and leading coefficient as the counting polynomial A_{S_g}(d, q) for absolutely indecomposables over F_q, evaluated at q=1.

  15. 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...... that formation of backpacks is not specific for L.?monocytogenes, and independent of bacterial pathogenicity or virulence. Hence, backpacking appears to represent a unique and highly effective strategy of Acanthamoeba to trap and feed on motile bacteria....

  16. Inhibition of Listeria monocytogenes on cold-smoked salmon by nisin and carbon dioxide atmosphere

    DEFF Research Database (Denmark)

    Nilsson, Lilian; Huss, Hans Henrik; Gram, Lone

    1997-01-01

    of nisin to CO2 packed cold-smoked salmon resulted in a 1 to 2 log reduction of L. monocytogenes followed by a lag phase of 8 and 20 days in salmon with 500 and 1000 IU nisin/g, respectively. The levels of L. monocytogenes remained below 10(3) cfu/g during 27 days of storage at both concentrations of nisin...

  17. 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.

  18. Vascular Endograft Infection with Listeria monocytogenes reated with Surgical Debridement but without Graft Removal

    Directory of Open Access Journals (Sweden)

    Beate Tanner-Steinmann

    2011-01-01

    Full Text Available The awareness of Listeria monocytogenes as a pathogen in meningitis and bacteremia in immunosuppressed patients is high. We report a case of vascular graft infection due to Listeria monocytogenes as an example of a less well-known manifestation of listeriosis and focus on the possible treatment procedures emphasizing a management with surgical debridement but preservation of the endograft, in contrast to the gold standard treatment of vascular graft infections which consists of a removal of the graft.

  19. 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.

  20. 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.

  1. Functional impact of mutational activation on the Listeria monocytogenes central virulence regulator PrfA

    OpenAIRE

    Miner, Maurine D.; Port, Gary C.; Freitag, Nancy E.

    2008-01-01

    The transcriptional activator PrfA is required for the expression of virulence factors necessary for Listeria monocytogenes pathogenesis. PrfA is believed to become activated following L. monocytogenes entry into the cytosol of infected host cells resulting in the induction of target genes whose products are required for bacterial intracellular growth and cell-to-cell spread. Several mutations have been identified that appear to lock PrfA into its highly activated cytosolic form (known as prf...

  2. Growth Potential of Listeria Monocytogenes and Staphylococcus Aureus on Fresh-Cut Tropical Fruits.

    Science.gov (United States)

    Feng, Ke; Hu, Wenzhong; Jiang, Aili; Xu, Yongping; Sarengaowa; Li, Xiaobo; Bai, Xue

    2015-11-01

    The objective of this study was to evaluate the fate of Staphylococcus aureus, Listeria monocytogenes, and natural microbiota on fresh-cut tropical fruits (pitaya, mango, papaya and pineapple) with commercial PVC film at different storage temperature (5, 13, and 25 °C). The results showed that S. aureus, L. monocytogenes, and natural microbiota increased significantly on fresh-cut tropical fruits at 25 °C. Both pathogen and natural microbiota were able to grow on fresh-cut tropical fruits at 13 °C. The maximum population of L. monocytogenes was higher than that of S. aureus on fresh-cut tropical fruits. L. monocytogenes and S. aureus could survive without growth on fresh-cut pitaya, mango, and papaya at 5 °C. The population of L. monocytogenes declined significantly on fresh-cut pineapple at all temperature, indicating composition of fresh-cut pineapple could inhibit growth of L. monocytogenes. However, S. aureus was still able to grow on fresh-cut pineapple at storage temperature. Thus, this study suggests that 4 kinds of fresh-cut tropical fruits (pitaya, mango, papaya, and pineapple) should be stored at low temperature to extend shelf life as well as to ensure the safety of fresh-cut fruits. The data collected in this study demonstrated that L. monocytogenes and S. aureus were able to grow on fresh-cut tropical fruits at different temperatures. These results could be of interest in knowing the capacity of tropical fruits to support the growth of L. monocytogenes and S. aureus. This information may also be useful to local and state regulatory officials responsible for food safety.

  3. 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.

  4. 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

    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 ....... monocytogenes in dairies and retail products emphasize the need for continuous surveillance of this pathogen in the Brazilian dairy industry. (C) 2017 Elsevier Ltd. All rights reserved....

  5. In Vitro Evaluation of Bacteriocins Activity Against Listeria monocytogenes Biofilm Formation.

    Science.gov (United States)

    Camargo, Anderson Carlos; de Paula, Otávio Almeida Lino; Todorov, Svetoslav Dimitrov; Nero, Luís Augusto

    2016-03-01

    The present study aimed to assess the activity of cell-free supernatant (CFS) containing bacteriocins on the formation and maintenance of biofilms developed by Listeria monocytogenes, and the associated effect of bacteriocins and ethylene-diamine-tetra-acetic acid (EDTA) on the formed biofilm. CFS from 9 lactic acid bacteria (LAB) strains was tested for inhibitory activity against 85 L. monocytogenes isolates and 21 LAB strains. Then, 12 L. monocytogenes strains were selected based on genetic profiles and sensitivity to CFS and were subjected to an in vitro assay to assess biofilm formation in microtiter plates, considering different culture media and incubation conditions. Based on these results, 6 L. monocytogenes strains were subjected to the same in vitro procedure to assess biofilm formation, being co-inoculated with CFS. In addition, these strains were subjected to the same in vitro procedure, modified by adding the CFS after biofilm formation. Relevant decrease in biofilm formation was observed in the first experiment, but CFS added after biofilm formation did not eliminate them. CFS from Lactobacillus curvatus ET31 were selected due to its anti-biofilm activity, being associated to EDTA at different concentrations and tested for biofilm control of three strains of L. monocytogenes, using the same in vitro procedure described previously. Concentrated bacteriocin presented poor performance in eliminating formed biofilms, and EDTA concentration presented no evident interference on biofilm elimination. Twelve selected L. monocytogenes strains were positive for investigated virulence makers and negative for luxS gene, recognized as being involved in biofilm formation. Selected L. monocytogenes strains were able to produce biofilms under different conditions. CFSs have the potential to prevent biofilm formation, but they were not able to destroy already formed biofilms. Nevertheless, low concentrations of CFS combined with EDTA caused a relevant reduction in

  6. 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

  7. 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.

  8. Microglia engulf viable newborn cells in the epileptic dentate gyrus.

    Science.gov (United States)

    Luo, Cong; Koyama, Ryuta; Ikegaya, Yuji

    2016-09-01

    Microglia, which are the brain's resident immune cells, engulf dead neural progenitor cells during adult neurogenesis in the subgranular zone (SGZ) of the dentate gyrus (DG). The number of newborn cells in the SGZ increases significantly after status epilepticus (SE), but whether and how microglia regulate the number of newborn cells after SE remain unclear. Here, we show that microglia rapidly eliminate newborn cells after SE by primary phagocytosis, a process by which viable cells are engulfed, thereby regulating the number of newborn cells that are incorporated into the DG. The number of newborn cells in the DG was increased at 5 days after SE in the adult mouse brain but rapidly decreased to the control levels within a week. During this period, microglia in the DG were highly active and engulfed newborn cells. We found that the majority of engulfed newborn cells were caspase-negative viable cells. Finally, inactivation of microglia with minocycline maintained the increase in the number of newborn cells after SE. Furthermore, minocycline treatment after SE induced the emergence of hilar ectopic granule cells. Thus, our findings suggest that microglia may contribute to homeostasis of the dentate neurogenic niche by eliminating excess newborn cells after SE via primary phagocytosis. GLIA 2016;64:1508-1517.

  9. Free-floating planets: a viable option for panspermia

    CERN Document Server

    Durand-Manterola, Hector Javier

    2010-01-01

    Genomic complexity can be used as a clock with which the moment in which life originated can be measured. Some authors who have studied this problem have come to the conclusion that it is not possible that terrestrial life originated here and that, in reality, life originated giga-years ago, before the solar system existed. If we accept this conclusion there is no other option than to admit that panspermia is something viable.The goal of this study is to propose a viable hypothesis for the transport of SLF from one planetary system to another. During the formation period of a planetary system giant planets can eject planets the size of the Earth, or larger, turning them into free-floating planets in interstellar space. These free-floating planets have also been called free floaters. If a free floater, which has developed life, enters a lifeless planetary system, it can seed the worlds of this system with SLF dragged by the stellar wind from one planet to another or by great impacts on the free planet. To supp...

  10. Models with radiative neutrino masses and viable dark matter candidates

    CERN Document Server

    Restrepo, Diego; Yaguna, Carlos

    2013-01-01

    We provide a list of particle physics models at the TeV-scale that are compatible with neutrino masses and dark matter. In these models, the Standard Model particle content is extended with a small number (\\leq 4) of scalar and fermion fields transforming as singlets, doublets or triplets under SU(2), and neutrino masses are generated radiatively via 1-loop diagrams. The dark matter candidates are stabilized by a Z_2 symmetry and are in general mixtures of the neutral components of such new multiplets. We describe the particle content of each of these models and determine the conditions under which they are consistent with current data. We find a total of 35 viable models, most of which have not been previously studied in the literature. There is a great potential to test these models at the LHC not only due to the TeV-scale masses of the new fields but also because about half of the viable models contain particles with exotic electric charges, which give rise to background-free signals. Our results should se...

  11. Formas cocoides de Helicobacter pylori: viables o degenerativas

    Directory of Open Access Journals (Sweden)

    Felipe Cava

    2003-06-01

    Full Text Available De los trabajos presentados acerca de las formas cocoides de Helicobacter pylori se deduce una controversia mucho mayor que la resultante del mero estudio clínico de este microorganismo. Parece claro que existe una conversión tanto in vivo como in vitro de las formas espirales a las formas cocoides inducida por varios motivos, como cultivos prolongados, estrés físico y químico, y agentes antimicrobianos. En esta revisión repasamos los puntos de vista que han dividido a investigadores de esta área en dos grupos bien definidos: Los que consideran a estas formas cocoides como un producto no viable de degeneración celular y los que piensan que estas formas son estructuras viables,durmientes o de resistencia frente a condiciones ambientales adversas. Esta discrepancia conlleva a que interrogantes sobre la relación entre la transmisión de la enfermedad y estas formas cocoides permanezcan sin respuesta todavía.

  12. 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.

  13. Listeriosis outbreak in dairy cattle caused by an unusual Listeria monocytogenes serotype 4b strain.

    Science.gov (United States)

    Bundrant, Brittany N; Hutchins, Tony; den Bakker, Henk C; Fortes, Esther; Wiedmann, Martin

    2011-01-01

    A listeriosis outbreak, in dairy cattle, with a high case mortality and acute death after onset of symptoms was investigated using gross pathology and bacteriologic approaches, including molecular characterization of a clinical Listeria monocytogenes isolate. In a herd of 315 animals, 9 animals showed clinical symptoms consistent with listeriosis, including 3 animals that died within 2-4 days after acute onset of clinical signs, 4 animals that were euthanized, and 2 that survived. Initial EcoRI ribotyping and serotyping indicated that this outbreak was caused by an unusual L. monocytogenes serotype 4b strain, which was classified into lineage III. Further characterization of this isolate by DNA sequencing-based subtyping methods indicated that the strain responsible for this outbreak represented a unique genotype as supported by its classification into a new sigB allelic type, which has not been identified previously among >290 isolates, and by compelling phylogenetic evidence. While lineage III isolates are generally rare, they seem to be more common among L. monocytogenes isolates from animals with clinical signs of listeriosis. This is the first report of a particularly severe clinical course of disease associated with infection by a lineage III strain. The high prevalence of Listeria spp., including L. monocytogenes, in the farm environments may favor emergence and evolution of novel, and possibly more virulent, L. monocytogenes strains. Continued monitoring of animal listeriosis cases and outbreaks may not only improve animal health but also aid in the early discovery of newly emerging L. monocytogenes strains.

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

    Directory of Open Access Journals (Sweden)

    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.

  15. 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.

  16. Rapid and sensitive detection of Listeria monocytogenes by loop-mediated isothermal amplification.

    Science.gov (United States)

    Tang, Meng-Jun; Zhou, Sheng; Zhang, Xiao-Yan; Pu, Jun-Hua; Ge, Qing-Lian; Tang, Xiu-Jun; Gao, Yu-Shi

    2011-12-01

    Loop-mediated isothermal amplification (LAMP) was designed for detection of Listeria monocytogenes, which is an important food-borne kind of pathogenic bacteria causing human and animal disease. The primers set for the hlyA gene consist of six primers targeting eight regions on specific gene. The LAMP assay could be performed within 40 min at 65°C in a water bath. Amplification products were visualized by calcein and manganous ion and agarose gel electrophoresis. Sensitivity of the LAMP assay for detection of L. monocytogenes in pure cultures was 2.0 CFU per reaction. The LAMP assay was 100-fold higher sensitive than that of the conventional PCR assay. Taking this way, 60 chicken samples were investigated for L. monocytogenes. The accuracy of LAMP was shown to be 100% when compared to the "gold standard" culture-biotechnical, while the PCR assay failed to detect L. monocytogenes in two of the positive samples. It is shown that LAMP assay can be used as a sensitive, rapid, and simple detection tool for the detection of L. monocytogenes and will facilitate the surveillance for contamination of L. monocytogenes in food.

  17. 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.

  18. Characterization of a Mutant Listeria monocytogenes Strain Expressing Green Fluorescent Protein

    Institute of Scientific and Technical Information of China (English)

    Ling-Li JIANG; Hou-Hui SONG; Xue-Yan CHEN; Chun-Lin KE; Jing-Jing XU; Ning CHEN; Wei-Huan FANG

    2005-01-01

    To construct a recombinant strain of Listeria monocytogenes for the expression of heterologous genes, homologous recombination was utilized for insertional mutation, targeting its listeriolysin O gene(hly). The gene encoding green fluorescent protein (GFP) was used as the indicator of heterologous gene expression. The gene gfp was inserted into hly downstream from its promoter and signal sequence by an overlapping extension polymerase chain reaction, and was then cloned into the shuttle plasmid pKSV7 for allelic exchange with the L. monocytogenes chromosome. Homologous recombination was achieved by growing the electro-transformed L. monocytogenes cells on chloramphenicol plates at a non-permissive temperature.Sequencing analysis indicated correct insertion of the target gene in-frame with the signal sequence. The recombinant strain expressed GFP constitutively as revealed by fluorescence microscopy. The mutant strain L. monocytogenes hly-gfp lost its hemolytic activity as visualized on the blood agar or when analyzed with the culture supernatant samples. Such insertional mutation resulted in a reduced virulence of about 2 logs less than its parent strain L. monocytogenes 10403s as shown by the 50%-lethal-dose assays in the mouse and embryonated chicken egg models. These results thus demonstrate that mutated L. monocytogenes could be a potential carrier for the expression of heterologous passenger genes or could act as an indicator organism in the food industry.

  19. 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.

  20. Effect of honokiol on exotoxin proteins listeriolysin O and p60 secreted by Listeria monocytogenes.

    Science.gov (United States)

    Meng, Rizeng; Zhao, Ziwen; Guo, Na; Liu, Zonghui; Zhao, Xingchen; Li, Wenli; Li, Xiaoxu; Shi, Ce; Nie, Dandan; Wang, Weilin; Liu, Tao; Ma, Wenchen; Yu, Lu; Li, Juan

    2015-12-01

    Listeria monocytogenes is considered one of the most important foodborne pathogens. The virulence-related proteins listeriolysin O (LLO) and p60 are critical factors involved in Listeria pathogenesis. In the present study, we investigated the effect of honokiol on LLO and p60 secreted from L. monocytogenes. A listeriolysin assay was used to investigate the haemolytic activities of L. monocytogenes exposed to honokiol, and the secretion of LLO and p60 was detected by immunoblot analysis. Additionally, the influence of honokiol on the transcription of LLO and p60 genes (hly and iap, respectively) was analysed by real-time reverse transcription PCR. TNF-α release assays were performed to elucidate the biological relevance of changes in LLO and p60 secretion induced by honokiol. According to the data, honokiol showed good anti-L. monocytogenes activity, with MICs of 8-16 μg ml(-1), and the secretion of LLO and p60 was decreased by honokiol. In addition, the transcription of hly and iap was inhibited by honokiol. Our results indicate that TNF-α production by RAW264.7 cells stimulated with L. monocytogenes supernatants was inhibited by honokiol. Based on these data, we propose that honokiol could be used as a promising natural compound against L. monocytogenes and its virulence factors.