Comparative Genomics of Rhodococcus equi Virulence Plasmids Indicates Host-Driven Evolution of the vap Pathogenicity Island.

Science.gov (United States)

MacArthur, Iain; Anastasi, Elisa; Alvarez, Sonsiray; Scortti, Mariela; Vázquez-Boland, José A

2017-05-01

The conjugative virulence plasmid is a key component of the Rhodococcus equi accessory genome essential for pathogenesis. Three host-associated virulence plasmid types have been identified the equine pVAPA and porcine pVAPB circular variants, and the linear pVAPN found in bovine (ruminant) isolates. We recently characterized the R. equi pangenome (Anastasi E, et al. 2016. Pangenome and phylogenomic analysis of the pathogenic actinobacterium Rhodococcus equi. Genome Biol Evol. 8:3140-3148.) and we report here the comparative analysis of the virulence plasmid genomes. Plasmids within each host-associated type were highly similar despite their diverse origins. Variation was accounted for by scattered single nucleotide polymorphisms and short nucleotide indels, while larger indels-mostly in the plasticity region near the vap pathogencity island (PAI)-defined plasmid genomic subtypes. Only one of the plasmids analyzed, of pVAPN type, was exceptionally divergent due to accumulation of indels in the housekeeping backbone. Each host-associated plasmid type carried a unique PAI differing in vap gene complement, suggesting animal host-specific evolution of the vap multigene family. Complete conservation of the vap PAI was observed within each host-associated plasmid type. Both diversity of host-associated plasmid types and clonality of specific chromosomal-plasmid genomic type combinations were observed within the same R. equi phylogenomic subclade. Our data indicate that the overall strong conservation of the R. equi host-associated virulence plasmids is the combined result of host-driven selection, lateral transfer between strains, and geographical spread due to international livestock exchanges. © The Author(s) 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Product Variant Master as a Means to Handle Variant Design

DEFF Research Database (Denmark)

Hildre, Hans Petter; Mortensen, Niels Henrik; Andreasen, Mogens Myrup

1996-01-01

be implemented in the CAD system I-DEAS. A precondition for high degree of computer support is identification of a product variant master from which new variants can be derived. This class platform defines how a product build up fit certain production methods and rules governing determination of modules...

An LL-diaminopimelate aminotransferase defines a novel variant of the lysine biosynthesis pathway in plants.

Science.gov (United States)

Hudson, André O; Singh, Bijay K; Leustek, Thomas; Gilvarg, Charles

2006-01-01

Although lysine (Lys) biosynthesis in plants is known to occur by way of a pathway that utilizes diaminopimelic acid (DAP) as a central intermediate, the available evidence suggests that none of the known DAP-pathway variants found in nature occur in plants. A new Lys biosynthesis pathway has been identified in Arabidopsis (Arabidopsis thaliana) that utilizes a novel transaminase that specifically catalyzes the interconversion of tetrahydrodipicolinate and LL-diaminopimelate, a reaction requiring three enzymes in the DAP-pathway variant found in Escherichia coli. The LL-DAP aminotransferase encoded by locus At4g33680 was able to complement the dapD and dapE mutants of E. coli. This result, in conjunction with the kinetic properties and substrate specificity of the enzyme, indicated that LL-DAP aminotransferase functions in the Lys biosynthetic direction under in vivo conditions. Orthologs of At4g33680 were identified in all the cyanobacterial species whose genomes have been sequenced. The Synechocystis sp. ortholog encoded by locus sll0480 showed the same functional properties as At4g33680. These results demonstrate that the Lys biosynthesis pathway in plants and cyanobacteria is distinct from the pathways that have so far been defined in microorganisms.

Evolution and Virulence of Influenza A Virus Protein PB1-F2

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Ram P. Kamal

2017-12-01

Full Text Available PB1-F2 is an accessory protein of most human, avian, swine, equine, and canine influenza A viruses (IAVs. Although it is dispensable for virus replication and growth, it plays significant roles in pathogenesis by interfering with the host innate immune response, inducing death in immune and epithelial cells, altering inflammatory responses, and promoting secondary bacterial pneumonia. The effects of PB1-F2 differ between virus strains and host species. This can at least partially be explained by the presence of multiple PB1-F2 sequence variants, including premature stop codons that lead to the expression of truncated PB1-F2 proteins of different lengths and specific virulence-associated residues that enhance susceptibility to bacterial superinfection. Although there has been a tendency for human seasonal IAV to gradually reduce the number of virulence-associated residues, zoonotic IAVs contain a reservoir of PB1-F2 proteins with full length, virulence-associated sequences. Here, we review the molecular mechanisms by which PB1-F2 may affect influenza virulence, and factors associated with the evolution and selection of this protein.

Stress conditions triggering mucoid morphotype variation in Burkholderia species and effect on virulence in Galleria mellonella and biofilm formation in vitro.

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Inês N Silva

Full Text Available Burkholderia cepacia complex (Bcc bacteria are opportunistic pathogens causing chronic respiratory infections particularly among cystic fibrosis patients. During these chronic infections, mucoid-to-nonmucoid morphotype variation occurs, with the two morphotypes exhibiting different phenotypic properties. Here we show that in vitro, the mucoid clinical isolate Burkholderia multivorans D2095 gives rise to stable nonmucoid variants in response to prolonged stationary phase, presence of antibiotics, and osmotic and oxidative stresses. Furthermore, in vitro colony morphotype variation within other members of the Burkholderia genus occurred in Bcc and non-Bcc strains, irrespectively of their clinical or environmental origin. Survival to starvation and iron limitation was comparable for the mucoid parental isolate and the respective nonmucoid variant, while susceptibility to antibiotics and to oxidative stress was increased in the nonmucoid variants. Acute infection of Galleria mellonella larvae showed that, in general, the nonmucoid variants were less virulent than the respective parental mucoid isolate, suggesting a role for the exopolysaccharide in virulence. In addition, most of the tested nonmucoid variants produced more biofilm biomass than their respective mucoid parental isolate. As biofilms are often associated with increased persistence of pathogens in the CF lungs and are an indicative of different cell-to-cell interactions, it is possible that the nonmucoid variants are better adapted to persist in this host environment.

The virulence regulator PrfA promotes biofilm formation by Listeria monocytogenes.

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

2010-08-01

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

Comparative genomics and transcriptomics of Escherichia coli isolates carrying virulence factors of both enteropathogenic and enterotoxigenic E. coli.

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Hazen, Tracy H; Michalski, Jane; Luo, Qingwei; Shetty, Amol C; Daugherty, Sean C; Fleckenstein, James M; Rasko, David A

2017-06-14

Escherichia coli that are capable of causing human disease are often classified into pathogenic variants (pathovars) based on their virulence gene content. However, disease-associated hybrid E. coli, containing unique combinations of multiple canonical virulence factors have also been described. Such was the case of the E. coli O104:H4 outbreak in 2011, which caused significant morbidity and mortality. Among the pathovars of diarrheagenic E. coli that cause significant human disease are the enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC). In the current study we use comparative genomics, transcriptomics, and functional studies to characterize isolates that contain virulence factors of both EPEC and ETEC. Based on phylogenomic analysis, these hybrid isolates are more genomically-related to EPEC, but appear to have acquired ETEC virulence genes. Global transcriptional analysis using RNA sequencing, demonstrated that the EPEC and ETEC virulence genes of these hybrid isolates were differentially-expressed under virulence-inducing laboratory conditions, similar to reference isolates. Immunoblot assays further verified that the virulence gene products were produced and that the T3SS effector EspB of EPEC, and heat-labile toxin of ETEC were secreted. These findings document the existence and virulence potential of an E. coli pathovar hybrid that blurs the distinction between E. coli pathovars.

Host age modulates parasite infectivity, virulence and reproduction.

Science.gov (United States)

Izhar, Rony; Ben-Ami, Frida

2015-07-01

Host age is one of the most striking differences among hosts within most populations, but there is very little data on how age-dependent effects impact ecological and evolutionary dynamics of both the host and the parasite. Here, we examined the influence of host age (juveniles, young and old adults) at parasite exposure on host susceptibility, fecundity and survival as well as parasite transmission, using two clones of the water flea Daphnia magna and two clones of its bacterial parasite Pasteuria ramosa. Younger D. magna were more susceptible to infection than older ones, regardless of host or parasite clone. Also, younger-infected D. magna became castrated faster than older hosts, but host and parasite clone effects contributed to this trait as well. Furthermore, the early-infected D. magna produced considerably more parasite transmission stages than late-infected ones, while host age at exposure did not affect virulence as it is defined in models (host mortality). When virulence is defined more broadly as the negative effects of infection on host fitness, by integrating the parasitic effects on host fecundity and mortality, then host age at exposure seems to slide along a negative relationship between host and parasite fitness. Thus, the virulence-transmission trade-off differs strongly among age classes, which in turn affects predictions of optimal virulence. Age-dependent effects on host susceptibility, virulence and parasite transmission could pose an important challenge for experimental and theoretical studies of infectious disease dynamics and disease ecology. Our results present a call for a more explicit stage-structured theory for disease, which will incorporate age-dependent epidemiological parameters. © 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.

Systems analysis of multiple regulator perturbations allows discovery of virulence factors in Salmonella

Energy Technology Data Exchange (ETDEWEB)

Yoon, Hyunjin; Ansong, Charles; McDermott, Jason E.; Gritsenko, Marina A.; Smith, Richard D.; Heffron, Fred; Adkins, Joshua N.

2011-06-28

Background: Systemic bacterial infections are highly regulated and complex processes that are orchestrated by numerous virulence factors. Genes that are coordinately controlled by the set of regulators required for systemic infection are potentially required for pathogenicity. Results: In this study we present a systems biology approach in which sample-matched multi-omic measurements of fourteen virulence-essential regulator mutants were coupled with computational network analysis to efficiently identify Salmonella virulence factors. Immunoblot experiments verified network-predicted virulence factors and a subset was determined to be secreted into the host cytoplasm, suggesting that they are virulence factors directly interacting with host cellular components. Two of these, SrfN and PagK2, were required for full mouse virulence and were shown to be translocated independent of either of the type III secretion systems in Salmonella or the type III injectisome-related flagellar mechanism. Conclusions: Integrating multi-omic datasets from Salmonella mutants lacking virulence regulators not only identified novel virulence factors but also defined a new class of translocated effectors involved in pathogenesis. The success of this strategy at discovery of known and novel virulence factors suggests that the approach may have applicability for other bacterial pathogens.

Expression of virulence factors by Staphylococcus aureus grown in serum.

Science.gov (United States)

Oogai, Yuichi; Matsuo, Miki; Hashimoto, Masahito; Kato, Fuminori; Sugai, Motoyuki; Komatsuzawa, Hitoshi

2011-11-01

Staphylococcus aureus produces many virulence factors, including toxins, immune-modulatory factors, and exoenzymes. Previous studies involving the analysis of virulence expression were mainly performed by in vitro experiments using bacterial medium. However, when S. aureus infects a host, the bacterial growth conditions are quite different from those in a medium, which may be related to the different expression of virulence factors in the host. In this study, we investigated the expression of virulence factors in S. aureus grown in calf serum. The expression of many virulence factors, including hemolysins, enterotoxins, proteases, and iron acquisition factors, was significantly increased compared with that in bacterial medium. In addition, the expression of RNA III, a global regulon for virulence expression, was significantly increased. This effect was partially restored by the addition of 300 μM FeCl₃ into serum, suggesting that iron depletion is associated with the increased expression of virulence factors in serum. In chemically defined medium without iron, a similar effect was observed. In a mutant with agr inactivated grown in serum, the expression of RNA III, psm, and sec4 was not increased, while other factors were still induced in the mutant, suggesting that another regulatory factor(s) is involved. In addition, we found that serum albumin is a major factor for the capture of free iron to prevent the supply of iron to bacteria grown in serum. These results indicate that S. aureus expresses virulence factors in adaptation to the host environment.

An Aphid Effector Targets Trafficking Protein VPS52 in a Host-Specific Manner to Promote Virulence.

Science.gov (United States)

Rodriguez, Patricia A; Escudero-Martinez, Carmen; Bos, Jorunn I B

2017-03-01

Plant- and animal-feeding insects secrete saliva inside their hosts, containing effectors, which may promote nutrient release and suppress immunity. Although for plant pathogenic microbes it is well established that effectors target host proteins to modulate host cell processes and promote disease, the host cell targets of herbivorous insects remain elusive. Here, we show that the existing plant pathogenic microbe effector paradigm can be extended to herbivorous insects in that effector-target interactions inside host cells modify critical host processes to promote plant susceptibility. We showed that the effector Mp1 from Myzus persicae associates with the host Vacuolar Protein Sorting Associated Protein52 (VPS52). Using natural variants, we provide a strong link between effector virulence activity and association with VPS52, and show that the association is highly specific to M persicae -host interactions. Also, coexpression of Mp1, but not Mp1-like variants, specifically with host VPS52s resulted in effector relocalization to vesicle-like structures that associate with prevacuolar compartments. We show that high VPS52 levels negatively impact virulence, and that aphids are able to reduce VPS52 levels during infestation, indicating that VPS52 is an important virulence target. Our work is an important step forward in understanding, at the molecular level, how a major agricultural pest promotes susceptibility during infestation of crop plants. We give evidence that an herbivorous insect employs effectors that interact with host proteins as part of an effective virulence strategy, and that these effectors likely function in a species-specific manner. © 2017 American Society of Plant Biologists. All Rights Reserved.

Experimental evaluation of the relationship between lethal or non-lethal virulence and transmission success in malaria parasite infections

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Nithiuthai S

2004-09-01

Full Text Available Abstract Background Evolutionary theory suggests that the selection pressure on parasites to maximize their transmission determines their optimal host exploitation strategies and thus their virulence. Establishing the adaptive basis to parasite life history traits has important consequences for predicting parasite responses to public health interventions. In this study we examine the extent to which malaria parasites conform to the predicted adaptive trade-off between transmission and virulence, as defined by mortality. The majority of natural infections, however, result in sub-lethal virulent effects (e.g. anaemia and are often composed of many strains. Both sub-lethal effects and pathogen population structure have been theoretically shown to have important consequences for virulence evolution. Thus, we additionally examine the relationship between anaemia and transmission in single and mixed clone infections. Results Whereas there was a trade-off between transmission success and virulence as defined by host mortality, contradictory clone-specific patterns occurred when defining virulence by anaemia. A negative relationship between anaemia and transmission success was found for one of the parasite clones, whereas there was no relationship for the other. Notably the two parasite clones also differed in a transmission phenotype (gametocyte sex ratio that has previously been shown to respond adaptively to a changing blood environment. In addition, as predicted by evolutionary theory, mixed infections resulted in increased anaemia. The increased anaemia was, however, not correlated with any discernable parasite trait (e.g. parasite density or with increased transmission. Conclusions We found some evidence supporting the hypothesis that there is an adaptive basis correlating virulence (as defined by host mortality and transmission success in malaria parasites. This confirms the validity of applying evolutionary virulence theory to biomedical

A virulent strain of deformed wing virus (DWV of honeybees (Apis mellifera prevails after Varroa destructor-mediated, or in vitro, transmission.

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Eugene V Ryabov

2014-06-01

Full Text Available The globally distributed ectoparasite Varroa destructor is a vector for viral pathogens of the Western honeybee (Apis mellifera, in particular the Iflavirus Deformed Wing Virus (DWV. In the absence of Varroa low levels DWV occur, generally causing asymptomatic infections. Conversely, Varroa-infested colonies show markedly elevated virus levels, increased overwintering colony losses, with impairment of pupal development and symptomatic workers. To determine whether changes in the virus population were due Varroa amplifying and introducing virulent virus strains and/or suppressing the host immune responses, we exposed Varroa-naïve larvae to oral and Varroa-transmitted DWV. We monitored virus levels and diversity in developing pupae and associated Varroa, the resulting RNAi response and transcriptome changes in the host. Exposed pupae were stratified by Varroa association (presence/absence and virus levels (low/high into three groups. Varroa-free pupae all exhibited low levels of a highly diverse DWV population, with those exposed per os (group NV exhibiting changes in the population composition. Varroa-associated pupae exhibited either low levels of a diverse DWV population (group VL or high levels of a near-clonal virulent variant of DWV (group VH. These groups and unexposed controls (C could be also discriminated by principal component analysis of the transcriptome changes observed, which included several genes involved in development and the immune response. All Varroa tested contained a diverse replicating DWV population implying the virulent variant present in group VH, and predominating in RNA-seq analysis of temporally and geographically separate Varroa-infested colonies, was selected upon transmission from Varroa, a conclusion supported by direct injection of pupae in vitro with mixed virus populations. Identification of a virulent variant of DWV, the role of Varroa in its transmission and the resulting host transcriptome changes furthers

An Aphid Effector Targets Trafficking Protein VPS52 in a Host-Specific Manner to Promote Virulence1[OPEN

Science.gov (United States)

2017-01-01

Plant- and animal-feeding insects secrete saliva inside their hosts, containing effectors, which may promote nutrient release and suppress immunity. Although for plant pathogenic microbes it is well established that effectors target host proteins to modulate host cell processes and promote disease, the host cell targets of herbivorous insects remain elusive. Here, we show that the existing plant pathogenic microbe effector paradigm can be extended to herbivorous insects in that effector-target interactions inside host cells modify critical host processes to promote plant susceptibility. We showed that the effector Mp1 from Myzus persicae associates with the host Vacuolar Protein Sorting Associated Protein52 (VPS52). Using natural variants, we provide a strong link between effector virulence activity and association with VPS52, and show that the association is highly specific to M. persicae-host interactions. Also, coexpression of Mp1, but not Mp1-like variants, specifically with host VPS52s resulted in effector relocalization to vesicle-like structures that associate with prevacuolar compartments. We show that high VPS52 levels negatively impact virulence, and that aphids are able to reduce VPS52 levels during infestation, indicating that VPS52 is an important virulence target. Our work is an important step forward in understanding, at the molecular level, how a major agricultural pest promotes susceptibility during infestation of crop plants. We give evidence that an herbivorous insect employs effectors that interact with host proteins as part of an effective virulence strategy, and that these effectors likely function in a species-specific manner. PMID:28100451

Allelic diversity of the Plasmodium falciparum erythrocyte membrane protein 1 entails variant-specific red cell surface epitopes.

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Inès Vigan-Womas

Full Text Available The clonally variant Plasmodium falciparum PfEMP1 adhesin is a virulence factor and a prime target of humoral immunity. It is encoded by a repertoire of functionally differentiated var genes, which display architectural diversity and allelic polymorphism. Their serological relationship is key to understanding the evolutionary constraints on this gene family and rational vaccine design. Here, we investigated the Palo Alto/VarO and IT4/R29 and 3D7/PF13_003 parasites lines. VarO and R29 form rosettes with uninfected erythrocytes, a phenotype associated with severe malaria. They express an allelic Cys2/group A NTS-DBL1α(1 PfEMP1 domain implicated in rosetting, whose 3D7 ortholog is encoded by PF13_0003. Using these three recombinant NTS-DBL1α(1 domains, we elicited antibodies in mice that were used to develop monovariant cultures by panning selection. The 3D7/PF13_0003 parasites formed rosettes, revealing a correlation between sequence identity and virulence phenotype. The antibodies cross-reacted with the allelic domains in ELISA but only minimally with the Cys4/group B/C PFL1955w NTS-DBL1α. By contrast, they were variant-specific in surface seroreactivity of the monovariant-infected red cells by FACS analysis and in rosette-disruption assays. Thus, while ELISA can differentiate serogroups, surface reactivity assays define the more restrictive serotypes. Irrespective of cumulated exposure to infection, antibodies acquired by humans living in a malaria-endemic area also displayed a variant-specific surface reactivity. Although seroprevalence exceeded 90% for each rosetting line, the kinetics of acquisition of surface-reactive antibodies differed in the younger age groups. These data indicate that humans acquire an antibody repertoire to non-overlapping serotypes within a serogroup, consistent with an antibody-driven diversification pressure at the population level. In addition, the data provide important information for vaccine design, as

Evaluation of North American isolates of Soybean mosaic virus for gain of virulence on Rsv-genotype soybeans with special emphasis on resistance-breaking determinants on Rsv4.

Science.gov (United States)

Khatabi, B; Fajolu, O L; Wen, R-H; Hajimorad, M R

2012-12-01

Resistance to Soybean mosaic virus (SMV) in soybean is conferred by three dominant genes: Rsv1, Rsv3 and Rsv4. Over the years, scientists in the USA have utilized a set of standard pathotypes, SMV-G1 to SMV-G7, to study interaction with Rsv-genotype soybeans. However, these pathotypes were isolated from a collection of imported soybean germplasm over 30 years ago. In this study, 35 SMV field isolates collected in recent years from 11 states were evaluated for gain of virulence on soybean genotypes containing individual Rsv genes. All isolates were avirulent on L78-379 (Rsv1), whereas 19 were virulent on L29 (Rsv3). On PI88788 (Rsv4), 14 of 15 isolates tested were virulent; however, only one was capable of systemically infecting all of the inoculated V94-5152 (Rsv4). Nevertheless, virulent variants from 11 other field isolates were rapidly selected on initial inoculation onto V94-5152 (Rsv4). The P3 cistrons of the original isolates and their variants on Rsv4-genotype soybeans were sequenced. Analysis showed that virulence on PI88788 (Rsv4) was not associated, in general, with selection of any new amino acid, whereas Q1033K and G1054R substitutions were consistently selected on V94-5152 (Rsv4). The role of Q1033K and G1054R substitutions, individually or in combination, in virulence on V94-5152 (Rsv4) was confirmed on reconstruction in the P3 cistron of avirulent SMV-N, followed by biolistic inoculation. Collectively, our data demonstrate that SMV has evolved virulence towards Rsv3 and Rsv4, but not Rsv1, in the USA. Furthermore, they confirm that SMV virulence determinants on V94-5152 (Rsv4) reside on P3. © 2012 THE AUTHORS. MOLECULAR PLANT PATHOLOGY © 2012 BSPP AND BLACKWELL PUBLISHING LTD.

Chlamydial variants differ in ability to ascend the genital tract in the guinea pig model of chlamydial genital infection.

Science.gov (United States)

Yeruva, Laxmi; Bowlin, Anne K; Spencer, Nicole; Maurelli, Anthony T; Rank, Roger G

2015-08-01

An important question in the study of chlamydial genital tract disease is why some women develop severe upper tract disease while others have mild or even "silent" infections with or without pathology. Animal studies suggest that the pathological outcome of an infection is dependent upon both the composition of the infecting chlamydial population and the genotype of the host, along with host physiological effects, such as the cyclical production of reproductive hormones and even the size of the infecting inoculum or the number of repeated infections. In this study, we compared two variants of Chlamydia caviae, contrasting in virulence, with respect to their abilities to ascend the guinea pig genital tract. We then determined the effect of combining the two variants on the course of infection and on the bacterial loads of the two variants in the genital tract. Although the variants individually had similar infection kinetics in the cervix, SP6, the virulent variant, could be isolated from the oviducts more often and in greater numbers than the attenuated variant, AZ2. SP6 also elicited higher levels of interleukin 8 (IL-8) in the lower genital tract and increased leukocyte infiltration in the cervix and uterus compared to AZ2. When the two variants were combined in a mixed infection, SP6 outcompeted AZ2 in the lower genital tract; however, AZ2 was able to ascend the genital tract as readily as SP6. These data suggest that the ability of SP6 to elicit an inflammatory response in the lower genital tract facilitates the spread of both variants to the oviducts. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Type 1 fimbrial expression enhances Escherichia coli virulence for the urinary tract.

OpenAIRE

Connell, I; Agace, W; Klemm, P; Schembri, M; Mărild, S; Svanborg, C

1996-01-01

Type 1 fimbriae are adhesion organelles expressed by many Gram-negative bacteria. They facilitate adherence to mucosal surfaces and inflammatory cells in vitro, but their contribution to virulence has not been defined. This study presents evidence that type 1 fimbriae increase the virulence of Escherichia coli for the urinary tract by promoting bacterial persistence and enhancing the inflammatory response to infection. In a clinical study, we observed that disease severity was greater in chil...

Association between virulence and triazole tolerance in the phytopathogenic fungus Mycosphaerella graminicola.

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Lina Yang

Full Text Available Host resistance and synthetic antimicrobials such as fungicides are two of the main approaches used to control plant diseases in conventional agriculture. Although pathogens often evolve to overcome host resistance and antimicrobials, the majority of reports have involved qualitative host - pathogen interactions or antimicrobials targeting a single pathogen protein or metabolic pathway. Studies that consider jointly the evolution of virulence, defined as the degree of damage caused to a host by parasite infection, and antimicrobial resistance are rare. Here we compared virulence and fungicide tolerance in the fungal pathogen Mycosphaerella graminicola sampled from wheat fields across three continents and found a positive correlation between virulence and tolerance to a triazole fungicide. We also found that quantitative host resistance selected for higher pathogen virulence. The possible mechanisms responsible for these observations and their consequences for sustainable disease management are discussed.

An ll-Diaminopimelate Aminotransferase Defines a Novel Variant of the Lysine Biosynthesis Pathway in Plants1[W

Science.gov (United States)

Hudson, André O.; Singh, Bijay K.; Leustek, Thomas; Gilvarg, Charles

2006-01-01

Although lysine (Lys) biosynthesis in plants is known to occur by way of a pathway that utilizes diaminopimelic acid (DAP) as a central intermediate, the available evidence suggests that none of the known DAP-pathway variants found in nature occur in plants. A new Lys biosynthesis pathway has been identified in Arabidopsis (Arabidopsis thaliana) that utilizes a novel transaminase that specifically catalyzes the interconversion of tetrahydrodipicolinate and ll-diaminopimelate, a reaction requiring three enzymes in the DAP-pathway variant found in Escherichia coli. The ll-DAP aminotransferase encoded by locus At4g33680 was able to complement the dapD and dapE mutants of E. coli. This result, in conjunction with the kinetic properties and substrate specificity of the enzyme, indicated that ll-DAP aminotransferase functions in the Lys biosynthetic direction under in vivo conditions. Orthologs of At4g33680 were identified in all the cyanobacterial species whose genomes have been sequenced. The Synechocystis sp. ortholog encoded by locus sll0480 showed the same functional properties as At4g33680. These results demonstrate that the Lys biosynthesis pathway in plants and cyanobacteria is distinct from the pathways that have so far been defined in microorganisms. PMID:16361515

Identification of point mutations in clinical Staphylococcus aureus strains that produce small-colony variants auxotrophic for menadione.

Science.gov (United States)

Dean, Melissa A; Olsen, Randall J; Long, S Wesley; Rosato, Adriana E; Musser, James M

2014-04-01

Staphylococcus aureus small-colony variants (SCVs) are implicated in chronic and relapsing infections that are difficult to diagnose and treat. Despite many years of study, the underlying molecular mechanisms and virulence effect of the small-colony phenotype remain incompletely understood. We sequenced the genomes of five S. aureus SCV strains recovered from human patients and discovered previously unidentified nonsynonymous point mutations in three genes encoding proteins in the menadione biosynthesis pathway. Analysis of genetic revertants and complementation with wild-type alleles confirmed that these mutations caused the SCV phenotype and decreased virulence for mice.

Automated 5 ' nuclease assay for detection of virulence factors in porcine Escherichia coli

DEFF Research Database (Denmark)

Frydendahl, K.; Imberechts, H.; Lehmann, S.

2001-01-01

(STa, STb, EAST1) and heat labile LT) enterotoxins and the verocytotoxin variant 2e (VT2e). To correctly identify false negative results, an endogenous internal control targeting the E. coil 16S rRNA gene was incorporated in each test tube. The assay was evaluated using a collection of E. coil...... reference strains which have previously been examined with phenotypical assays or DNA hybridization. Furthermore, the assay was evaluated by testing porcine E. coil field strains, previously characterized. The 5' nuclease assay correctly detected the presence of virulence genes in all reference strains....... When testing field strains there was generally excellent agreement with results obtained by laboratories in Belgium and Germany. In conclusion, the 5' nuclease assay developed is a fast and specific tool for detection of E. coli virulence genes in the veterinary diagnostic laboratory....

Clonality, virulence and antimicrobial resistance of enteroaggregative Escherichia coli from Mirzapur, Bangladesh.

Science.gov (United States)

Chattaway, Marie Anne; Day, Michaela; Mtwale, Julia; White, Emma; Rogers, James; Day, Martin; Powell, David; Ahmad, Marwa; Harris, Ross; Talukder, Kaisar Ali; Wain, John; Jenkins, Claire; Cravioto, Alejandro

2017-10-01

This study investigates the virulence and antimicrobial resistance in association with common clonal complexes (CCs) of enteroaggregative Escherichia coli (EAEC) isolated from Bangladesh. The aim was to determine whether specific CCs were more likely to be associated with putative virulence genes and/or antimicrobial resistance. The presence of 15 virulence genes (by PCR) and susceptibility to 18 antibiotics were determined for 151 EAEC isolated from cases and controls during an intestinal infectious disease study carried out between 2007-2011 in the rural setting of Mirzapur, Bangladesh (Kotloff KL, Blackwelder WC, Nasrin D, Nataro JP, Farag TH et al.Clin Infect Dis 2012;55:S232-S245). These data were then analysed in the context of previously determined serotypes and clonal complexes defined by multi-locus sequence typing. Overall there was no association between the presence of virulence or antimicrobial resistance genes in isolates of EAEC from cases versus controls. However, when stratified by clonal complex (CC) one CC associated with cases harboured more virulence factors (CC40) and one CC harboured more resistance genes (CC38) than the average. There was no direct link between the virulence gene content and antibiotic resistance. Strains within a single CC had variable virulence and resistance gene content indicating independent and multiple gene acquisitions over time. In Bangladesh, there are multiple clonal complexes of EAEC harbouring a variety of virulence and resistance genes. The emergence of two of the most successful clones appeared to be linked to either increased virulence (CC40) or antimicrobial resistance (CC38), but increased resistance and virulence were not found in the same clonal complexes.

Plasmid transferability of KPC into a virulent K2 serotype Klebsiella pneumoniae.

Science.gov (United States)

Siu, Leung-Kei Kristopher; Huang, David B; Chiang, Tom

2014-03-31

KPC-producing carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are associated with high mortality; however, their virulence determinants are not well defined. We investigated the virulence and plasmid transferability among KPC-containing K. pneumoniae isolates. KPC-2 and -3 were successfully conjugated and retained by a virulent K2 K. pneumoniae recipient isolate. Antimicrobial susceptibility testing showed KPC-2 and -3 donor strains were resistant to more than four classes of antibiotics while the K2 isolate was only initially resistant to ampicillin. After conjugation of KPC-2 and -3, the K2 K. pneumoniae transconjugants became resistant to all beta-lactams. Additionally, the KPC K2 K. pneumoniae transconjugants continued to retain its high serum resistance and murine lethality. Conjugation and retainment of KPC by virulent K2 K. pneumoniae and the ability of the tranconjugants to maintain its high serum resistance and murine lethality after conjugation was demonstrated in this study. These findings are concerning for the potential of KPC-like genes to disseminate among virulent K. pneumoniae isolates.

Virulence differences among Francisella tularensis subsp. tularensis clades in mice.

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Claudia R Molins

Full Text Available Francisella tularensis subspecies tularensis (type A and holarctica (type B are of clinical importance in causing tularemia. Molecular typing methods have further separated type A strains into three genetically distinct clades, A1a, A1b and A2. Epidemiological analyses of human infections in the United States suggest that A1b infections are associated with a significantly higher mortality rate as compared to infections caused by A1a, A2 and type B. To determine if genetic differences as defined by molecular typing directly correlate with differences in virulence, A1a, A1b, A2 and type B strains were compared in C57BL/6 mice. Here we demonstrate significant differences between survival curves for infections caused by A1b versus A1a, A2 and type B, with A1b infected mice dying earlier than mice infected with A1a, A2 or type B; these results were conserved among multiple strains. Differences were also detected among type A clades as well as between type A clades and type B with respect to bacterial burdens, and gross anatomy in infected mice. Our results indicate that clades defined within F. tularensis subsp. tularensis by molecular typing methods correlate with virulence differences, with A1b strains more virulent than A1a, A2 and type B strains. These findings indicate type A strains are not equivalent with respect to virulence and have important implications for public health as well as basic research programs.

Rapid acquisition adaptive amino acid substitutions involved in the virulence enhancement of an H1N2 avian influenza virus in mice.

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Yu, Zhijun; Sun, Weiyang; Zhang, Xinghai; Cheng, Kaihui; Zhao, Chuqi; Xia, Xianzhu; Gao, Yuwei

2017-08-01

Although H1N2 avian influenza virus (AIV) only infect birds, documented cases of swine infection with H1N2 influenza viruses suggest this subtype AIV may pose a potential threat to mammals. Here, we generated mouse-adapted variants of a H1N2 AIV to identify adaptive changes that increased virulence in mammals. MLD 50 of the variants were reduced >1000-fold compared to the parental virus. Variants displayed enhanced replication in vitro and in vivo, and replicate in extrapulmonary organs. These data show that enhanced replication capacity and expanded tissue tropism may increase the virulence of H1N2 AIV in mice. Sequence analysis revealed multiple amino acid substitutions in the PB2 (L134H, I647L, and D701N), HA (G228S), and M1 (D231N) proteins. These results indicate that H1N2 AIV can rapidly acquire adaptive amino acid substitutions in mammalian hosts, and these amino acid substitutions collaboratively enhance the ability of H1N2 AIV to replicate and cause severe disease in mammals. Copyright © 2017 Elsevier B.V. All rights reserved.

The OmpA-like protein Loa22 is essential for leptospiral virulence.

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Paula Ristow

2007-07-01

Full Text Available Pathogenic mechanisms of Leptospira interrogans, the causal agent of leptospirosis, remain largely unknown. This is mainly due to the lack of tools for genetic manipulations of pathogenic species. In this study, we characterized a mutant obtained by insertion of the transposon Himar1 into a gene encoding a putative lipoprotein, Loa22, which has a predicted OmpA domain based on sequence identity. The resulting mutant did not express Loa22 and was attenuated in virulence in the guinea pig and hamster models of leptospirosis, whereas the genetically complemented strain was restored in Loa22 expression and virulence. Our results show that Loa22 was expressed during host infection and exposed on the cell surface. Loa22 is therefore necessary for virulence of L. interrogans in the animal model and represents, to our knowledge, the first genetically defined virulence factor in Leptospira species.

Isolation of Shiga toxin-producing Escherichia coli harboring variant Shiga toxin genes from seafood

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Sreepriya Prakasan

2018-03-01

Full Text Available Background and Aim: Shiga toxin-producing Escherichia coli (STEC are important pathogens of global significance. STEC are responsible for numerous food-borne outbreaks worldwide and their presence in food is a potential health hazard. The objective of the present study was to determine the incidence of STEC in fresh seafood in Mumbai, India, and to characterize STEC with respect to their virulence determinants. Materials and Methods: A total of 368 E. coli were isolated from 39 fresh seafood samples (18 finfish and 21 shellfish using culture-based methods. The isolates were screened by polymerase chain reaction (PCR for the genes commonly associated with STEC. The variant Shiga toxin genes were confirmed by Southern blotting and hybridization followed by DNA sequencing. Results: One or more Shiga toxins genes were detected in 61 isolates. Of 39 samples analyzed, 10 (25.64% samples harbored STEC. Other virulence genes, namely, eaeA (coding for an intimin and hlyA (hemolysin A were detected in 43 and 15 seafood isolates, respectively. The variant stx1 genes from 6 isolates were sequenced, five of which were found to be stx1d variants, while one sequence varied considerably from known stx1 sequences. Southern hybridization and DNA sequence analysis suggested putative Shiga toxin variant genes (stx2 in at least 3 other isolates. Conclusion: The results of this study showed the occurrence of STEC in seafood harboring one or more Shiga toxin genes. The detection of STEC by PCR may be hampered due to the presence of variant genes such as the stx1d in STEC. This is the first report of stx1d gene in STEC isolated from Indian seafood.

Transient virulence of emerging pathogens.

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Bolker, Benjamin M; Nanda, Arjun; Shah, Dharmini

2010-05-06

Should emerging pathogens be unusually virulent? If so, why? Existing theories of virulence evolution based on a tradeoff between high transmission rates and long infectious periods imply that epidemic growth conditions will select for higher virulence, possibly leading to a transient peak in virulence near the beginning of an epidemic. This transient selection could lead to high virulence in emerging pathogens. Using a simple model of the epidemiological and evolutionary dynamics of emerging pathogens, along with rough estimates of parameters for pathogens such as severe acute respiratory syndrome, West Nile virus and myxomatosis, we estimated the potential magnitude and timing of such transient virulence peaks. Pathogens that are moderately evolvable, highly transmissible, and highly virulent at equilibrium could briefly double their virulence during an epidemic; thus, epidemic-phase selection could contribute significantly to the virulence of emerging pathogens. In order to further assess the potential significance of this mechanism, we bring together data from the literature for the shapes of tradeoff curves for several pathogens (myxomatosis, HIV, and a parasite of Daphnia) and the level of genetic variation for virulence for one (myxomatosis). We discuss the need for better data on tradeoff curves and genetic variance in order to evaluate the plausibility of various scenarios of virulence evolution.

Developing consistent pronunciation models for phonemic variants

CSIR Research Space (South Africa)

Davel, M

2006-09-01

Full Text Available Pronunciation lexicons often contain pronunciation variants. This can create two problems: It can be difficult to define these variants in an internally consistent way and it can also be difficult to extract generalised grapheme-to-phoneme rule sets...

Deletion mutant defines DQ beta variants with DR4 positive DQw3 positive haplotypes

International Nuclear Information System (INIS)

Nepom, B.S.; Kim, S.J.; Nepom, G.T.

1986-01-01

We describe the production of an HLA deletion mutation by radiation mutagenesis of a DR4- and DQw3-homozygous, Dw4- and Dw14-heterozygous cell line designed to analyze polymorphisms associated with DR4 and DQw3. Southern blot analysis confirms a deletion of class I and class II genes on one haplotype. Variation in DQ beta alleles associated with DQw3 was previously described by characteristic RFLP patterns for a DQ beta bene. One pattern, which correlated precisely with A-10-83 monoclonal antibody reactivity (TA10), defined an allele which we call DQ''3.1''. The mutant cell line has lost the polymorphic bands on Southern blots corresponding to the DQ''3.1'' allele, while the intact Dw14 haplotype retains the alternate allele at DQ beta which is DQw-3 positive. TA10-negative. These data demonstrate the segregation of two DQw3 positive DQ beta allelic variants, both associated with DR4, which can be distinguished on the basis of both RFLP and monoclonal antibody reactivity

Exploring potential virulence regulators in Paracoccidioides brasiliensis isolates of varying virulence through quantitative proteomics.

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Castilho, Daniele G; Chaves, Alison F A; Xander, Patricia; Zelanis, André; Kitano, Eduardo S; Serrano, Solange M T; Tashima, Alexandre K; Batista, Wagner L

2014-10-03

Few virulence factors have been identified for Paracoccidioides brasiliensis, the agent of paracoccidioidomycosis. In this study, we quantitatively evaluated the protein composition of P. brasiliensis in the yeast phase using minimal and rich media to obtain a better understanding of its virulence and to gain new insights into pathogen adaptation strategies. This analysis was performed on two isolates of the Pb18 strain showing distinct infection profiles in B10.A mice. Using liquid chromatography/tandem mass spectrometry (LC-MS/MS) analysis, we identified and quantified 316 proteins in minimal medium, 29 of which were overexpressed in virulent Pb18. In rich medium, 29 out of 295 proteins were overexpressed in the virulent fungus. Three proteins were found to be up-regulated in both media, suggesting the potential roles of these proteins in virulence regulation in P. brasiliensis. Moreover, genes up-regulated in virulent Pb18 showed an increase in its expression after the recovery of virulence of attenuated Pb18. Proteins up-regulated in both isolates were grouped according to their functional categories. Virulent Pb18 undergoes metabolic reorganization and increased expression of proteins involved in fermentative respiration. This approach allowed us to identify potential virulence regulators and provided a foundation for achieving a molecular understanding of how Paracoccidioides modulates the host-pathogen interaction to its advantage.

Phages can constrain protist predation-driven attenuation of Pseudomonas aeruginosa virulence in multienemy communities

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Friman, Ville-Petri; Buckling, Angus

2014-01-01

The coincidental theory of virulence predicts that bacterial pathogenicity could be a by-product of selection by natural enemies in environmental reservoirs. However, current results are ambiguous and the simultaneous impact of multiple ubiquitous enemies, protists and phages on virulence evolution has not been investigated previously. Here we tested experimentally how Tetrahymena thermophila protist predation and PNM phage parasitism (bacteria-specific virus) alone and together affect the evolution of Pseudomonas aeruginosa PAO1 virulence, measured in wax moth larvae. Protist predation selected for small colony types, both in the absence and presence of phage, which showed decreased edibility to protists, reduced growth in the absence of enemies and attenuated virulence. Although phage selection alone did not affect the bacterial phenotype, it weakened protist-driven antipredatory defence (biofilm formation), its associated pleiotropic growth cost and the correlated reduction in virulence. These results suggest that protist selection can be a strong coincidental driver of attenuated bacterial virulence, and that phages can constrain this effect owing to effects on population dynamics and conflicting selection pressures. Attempting to define causal links such as these might help us to predict the cold and hot spots of coincidental virulence evolution on the basis of microbial community composition of environmental reservoirs. PMID:24671085

Virulence regulation in Staphylococcus aureus: the need for in vivo analysis of virulence factor regulation.

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Pragman, Alexa A; Schlievert, Patrick M

2004-10-01

Staphylococcus aureus is a pathogenic microorganism that is responsible for a wide variety of clinical infections. These infections can be relatively mild, but serious, life-threatening infections may result from the expression of staphylococcal virulence factors that are coordinated by virulence regulators. Much work has been done to characterize the actions of staphylococcal virulence regulators in broth culture. Recently, several laboratories showed that transcriptional analyses of virulence regulators in in vivo animal models or in human infection did not correlate with transcriptional analyses accomplished in vitro. In describing the differences between in vitro and in vivo transcription of staphylococcal virulence regulators, we hope to encourage investigators to study virulence regulators using infection models whenever possible.

Role of bacterial virulence proteins in Agrobacterium-mediated transformation of Aspergillus awamori

NARCIS (Netherlands)

Michielse, C.B.; Ram, A.F.J.; Hooykaas, P.J.J.; Hondel, C.A.M.J.J. van den

2004-01-01

The Agrobacterium-mediated transformation of Aspergillus awamori was optimized using defined co-cultivation conditions, which resulted in a reproducible and efficient transformation system. Optimal co-cultivation conditions were used to study the role of Agrobacterium tumefaciens virulence proteins

Staphylococcus aureus requires less virulence to establish an infection in diabetic hosts.

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Tuchscherr, Lorena; Korpos, Èva; van de Vyver, Hélène; Findeisen, Clais; Kherkheulidze, Salome; Siegmund, Anke; Deinhardt-Emmer, Stefanie; Bach, Olaf; Rindert, Martin; Mellmann, Alexander; Sunderkötter, Cord; Peters, Georg; Sorokin, Lydia; Löffler, Bettina

2018-05-22

Staphylococcus aureus is the most frequent pathogen causing diabetic foot infections. Here, we investigated the degree of bacterial virulence required to establish invasive tissue infections in diabetic organisms. Staphylococcal isolates from diabetic and non-diabetic foot ulcers were tested for their virulence in in vitro functional assays of host cell invasion and cytotoxicity. Isolates from diabetes mellitus type I/II patients exhibited less virulence than isolates from non-diabetic patients, but were nevertheless able to establish severe infections. In some cases, non-invasive isolates were detected deep within diabetic wounds, even though the strains were non-pathogenic in cell culture models. Testing of defined isolates in murine footpad injection models revealed that both low- and high-virulent bacterial strains persisted in higher numbers in diabetic compared to non-diabetic hosts, suggesting that hyperglycemia favors bacterial survival. Additionally, the bacterial load was higher in NOD mice, which have a compromised immune system, compared to C57Bl/6 mice. Our results reveal that high as well as low-virulent staphylococcal strains are able to cause soft tissue infections and to persist in diabetic humans and mice, suggesting a reason for the frequent and endangering infections in patients with diabetes. Copyright © 2018 Elsevier GmbH. All rights reserved.

Influence of population diversity on neurovirulence potential of plaque purified L-Zagreb variants.

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Ivancic-Jelecki, Jelena; Forcic, Dubravko; Jagusic, Maja; Kosutic-Gulija, Tanja; Mazuran, Renata; Balija, Maja Lang; Isakov, Ofer; Shomron, Noam

2016-04-29

Despite continuing research efforts, determinants of mumps virus virulence are still largely unknown. One of consequences of this is difficulty in striking a balance between efficacy and safety of live attenuated mumps vaccines. Among mumps vaccine strains associated with occurrence of postvaccinal aseptic meningitis is L-Zagreb, developed by further attenuation of vaccine strain L-3. Starting from an archived L-Zagreb sample with suboptimal neuroattenuation score, we isolated different viral variants and compared their genetic and phenotypic properties, in investigation of neurovirulence markers. Six different L-Zagreb variants were isolated by plaque purification. Their neurovirulent status was determined by rat-based neurovirulence test; population structure was determined by deep sequencing. We isolated one well neuroattenuated viral variant, two marginally neuroattenuated, and three insufficiently neuroattenuated. No genetic markers of neurovirulence could be identified. None of variants had detectable amounts of defective interfering particles. Two characteristics set insufficiently neuroattenuated variants apart from less-neurovirulent ones: elevated variability level in regions 1293-3314, 5363-7773 and 9382-11657, and/or elevated number of mutations present in frequencies ≥ 1%. The most neurovirulent variants possessed both of these features. Distinctive heterogeneity profiles were obtained for insufficiently neuroattenuated L-Zagreb variants. No markers that would discriminate between marginally and well neuroattenuated variants were identified. The findings of this study may serve as a guideline during development of an improved L3/L-Zagreb vaccine strain. Copyright © 2016 Elsevier Ltd. All rights reserved.

Antimicrobial medium- and long-chain free fatty acids prevent PrfA-dependent activation of virulence genes in Listeria monocytogenes.

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Sternkopf Lillebæk, Eva Maria; Lambert Nielsen, Stine; Scheel Thomasen, Rikke; Færgeman, Nils J; Kallipolitis, Birgitte H

The foodborne pathogen Listeria monocytogenes is the causative agent of the invasive disease listeriosis. Infection by L. monocytogenes involves bacterial crossing of the intestinal barrier and intracellular replication in a variety of host cells. The PrfA protein is the master regulator of virulence factors required for bacterial entry, intracellular replication and cell-to-cell spread. PrfA-dependent activation of virulence genes occurs primarily in the blood and during intracellular infection. In contrast, PrfA does not play a significant role in regulation of virulence gene expression in the intestinal environment. In the gastrointestinal phase of infection, the bacterium encounters a variety of antimicrobial agents, including medium- and long-chain free fatty acids that are commonly found in our diet and as active components of bile. Here we show that subinhibitory concentrations of specific antimicrobial free fatty acids act to downregulate transcription of PrfA-activated virulence genes. Interestingly, the inhibitory effect is also evident in cells encoding a constitutively active variant of PrfA. Collectively, our data suggest that antimicrobial medium- and long-chain free fatty acids may act as signals to prevent PrfA-mediated activation of virulence genes in environments where PrfA activation is not required, such as in food and the gastrointestinal tract. Copyright © 2017 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Structure and interactions of a dimeric variant of sHIP, a novel virulence determinant of Streptococcus pyogenes

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Carl eDiehl

2016-02-01

Full Text Available Streptococcus pyogenes is one of the most significant bacterial pathogens in the human population mostly causing superficial and uncomplicated infections (pharyngitis and impetigo but also invasive and life-threatening disease. We have previously identified a virulence determinant, protein sHIP, which is secreted at higher levels by an invasive compared to a non-invasive strain of S. pyogenes. The present work presents a further characterization of the structural and functional properties of this bacterial protein. Biophysical and structural studies have shown that protein sHIP forms stable tetramers both in the crystal and in solution. The tetramers are composed of four helix-loop-helix motifs with the loop regions connecting the helices displaying a high degree of flexibility. Owing to interactions at the tetramer interface, the observed tetramer can be described as a dimer of dimers. We identified three residues at the tetramer interface (Leu84, Leu88, Tyr95, which due to largely non-polar side-chains, could be important determinants for protein oligomerization. Based on these observations, we produced a sHIP variant in which these residues were mutated to alanines. Biophysical experiments clearly indicated that the sHIP mutant appear only as dimers in solution confirming the importance of the interfacial residues for protein oligomerisation. Furthermore, we could show that the sHIP mutant interacts with intact histidine-rich glycoprotein (HRG and the histidine-rich repeats in HRG, and inhibits their antibacterial activity to the same or even higher extent as compared to the wild type protein sHIP. We determined the crystal structure of the sHIP mutant, which, as a result of the high quality of the data, allowed us to improve the existing structural model of the protein. Finally, by employing NMR spectroscopy in solution, we generated a model for the complex between the sHIP mutant and an HRG-derived heparin-binding peptide, providing further

The effect of mutation on Rhodococcus equi virulence plasmid gene expression and mouse virulence.

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Ren, Jun; Prescott, John F

2004-11-15

An 81 kb virulence plasmid containing a pathogenicity island (PI) plays a crucial role in the pathogenesis of Rhodococcus equi pneumonia in foals but its specific function in virulence and regulation of plasmid-encoded virulence genes is unclear. Using a LacZ selection marker developed for R. equi in this study, in combination with an apramycin resistance gene, an efficient two-stage homologous recombination targeted gene mutation procedure was used to mutate three virulence plasmid genes, a LysR regulatory gene homologue (ORF4), a ResD-like two-component response regulator homologue (ORF8), and a gene (ORF10) of unknown function that is highly expressed by R. equi inside macrophages, as well as the chromosomal gene operon, phoPR. Virulence testing by liver clearance after intravenous injection in mice showed that the ORF4 and ORF8 mutants were fully attenuated, that the phoPR mutant was hypervirulent, and that virulence of the ORF10 mutant remained unchanged. A virulence plasmid DNA microarray was used to compare the plasmid gene expression profile of each of the four gene-targeted mutants against the parental R. equi strain. Changes were limited to PI genes and gene induction was observed for all mutants, suggesting that expression of virulence plasmid genes is dominated by a negative regulatory network. The finding of attenuation of ORF4 and ORF8 mutants despite enhanced transcription of vapA suggests that factors other than VapA are important for full expression of virulence. ORF1, a putative Lsr antigen gene, was strongly and similarly induced in all mutants, implying a common regulatory pathway affecting this gene for all four mutated genes. ORF8 is apparently the centre of this common pathway. Two distinct highly correlated gene induction patterns were observed, that of the ORF4 and ORF8 mutants, and that of the ORF10 and phoPR mutants. The gene induction pattern distinguishing these two groups paralleled their virulence in mice.

Infectious salmon anaemia virus (ISAV) in Chilean Atlantic salmon (Salmo salar) aquaculture: emergence of low pathogenic ISAV-HPR0 and re-emergence of virulent ISAV-HPR∆: HPR3 and HPR14

Science.gov (United States)

2013-01-01

Abstact Infectious salmon anaemia (ISA) is a serious disease of marine-farmed Atlantic salmon (Salmo salar) caused by ISA virus (ISAV), which belongs to the genus Isavirus, family Orthomyxoviridae. ISA is caused by virulent ISAV strains with deletions in a highly polymorphic region (HPR) of the hemagglutinin-esterase (HE) protein (designated virulent ISAV-HPR∆). This study shows the historic dynamics of ISAV-HPR∆ and ISAV-HPR0 in Chile, the genetic relationship among ISAV-HPR0 reported worldwide and between ISAV-HPR0 and ISAV-HPR∆ in Chile, and reports the 2013 ISA outbreak in Chile. The first ISA outbreak in Chile occurred from mid-June 2007 to 2010 and involved the virulent ISAV-HPR7b, which was then replaced by a low pathogenic ISAV-HPR0 variant. We analyzed this variant in 66 laboratory-confirmed ISAV-HPR0 cases in Chile in comparison to virulent ISAV-HPR∆ that caused two new ISA outbreaks in April 2013. Multiple alignment and phylogenetic analysis of HE sequences from all ISAV-HPR0 viruses allowed us to identify three genomic clusters, which correlated with three residue patterns of ISAV-HPR0 (360PST362, 360PAN362 and 360PAT362) in HPR. The virus responsible for the 2013 ISAV-HPR∆ cases in Chile belonged to ISAV-HPR3 and ISAV-HPR14, and in phylogenetic analyses, both clustered with the ISAV-HPR0 found in Chile. The ISAV-HPR14 had the ISAV-HPR0 residue pattern 360PAT362, which is the only type of ISAV-HPR0 variant found in Chile. This suggested to us that the 2013 ISAV-HPR∆ re-emerged from ISAV-HPR0 that is enzootic in Chilean salmon aquaculture and were not new introductions of virulent ISAV-HPR∆ to Chile. The clinical presentations and diagnostic evidence of the 2013 ISA cases indicated a mixed infection of ISAV with the ectoparasite Caligus rogercresseyi and the bacterium Piscirickettsia salmonis, which underscores the need for active ISAV surveillance in areas where ISAV-HPR0 is enzootic, to ensure early detection and control of new ISA

Dataset of mitochondrial genome variants in oncocytic tumors

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Lihua Lyu

2018-04-01

Full Text Available This dataset presents the mitochondrial genome variants associated with oncocytic tumors. These data were obtained by Sanger sequencing of the whole mitochondrial genomes of oncocytic tumors and the adjacent normal tissues from 32 patients. The mtDNA variants are identified after compared with the revised Cambridge sequence, excluding those defining haplogroups of our patients. The pathogenic prediction for the novel missense variants found in this study was performed with the Mitimpact 2 program.

Analysis of antimicrobial susceptibility and virulence factors in Helicobacter pylori clinical isolates

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Mendonça Sergio

2003-08-01

Full Text Available Abstract Background In this study, we evaluated the prevalence of primary resistance of Brazilian H. pylori isolates to metronidazole, clarithromycin, amoxicillin, tetracycline, and furazolidone. In addition, the vacA, iceA, cagA and cagE genotypes of strains isolated from Brazilian patients were determined and associated with clinical data in an effort to correlate these four virulence markers and antibiotic resistance. Methods H. pylori was cultured in 155 H. pylori-positive patients and MICs for metronidazole, clarithromycin, amoxicillin, tetracycline, and furazolidone were determined by the agar dilution method. Genomic DNA was extracted, and allelic variants of vacA, iceA, cagA and cagE were identified by the polymerase chain reaction. Results There was a strong association between the vacA s1/cagA -positive genotype and peptic ulcer disease (OR = 5.42, 95% CI 2.6–11.3, p = 0.0006. Additionally, infection by more virulent strains may protect against GERD, since logistic regression showed a negative association between the more virulent strain, vacA s1/cagA-positive genotype and GERD (OR = 0.26, 95% CI 0.08–0.8, p = 0.03. Resistance to metronidazole was detected in 75 patients (55%, to amoxicillin in 54 individuals (38%, to clarithromycin in 23 patients (16%, to tetracycline in 13 patients (9%, and to furazolidone in 19 individuals (13%. No significant correlation between pathogenicity and resistance or susceptibility was detected when MIC values for each antibiotic were compared with different vacA, iceA, cagA and cagE genotypes. Conclusion The analysis of virulence genes revealed a specific association between H. pylori strains and clinical outcome, furthermore, no significant association was detected among pathogenicity and resistance or susceptibility.

Genomic resources for a unique, low-virulence Babesia taxon from China

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Guiquan Guan

2016-10-01

Full Text Available Abstract Background Babesiosis is a socioeconomically important tick-borne disease of animals (including humans caused by haemoprotozoan parasites. The severity of babesiosis relates to host and parasite factors, particularly virulence/pathogenicity. Although Babesia bovis is a particularly pathogenic species of cattle, there are species of Babesia of ruminants that have limited pathogenicity. For instance, the operational taxonomic unit Babesia sp. Xinjiang (abbreviated here as Bx of sheep from China is substantially less virulent/pathogenic than B. bovis is in cattle. Although the reason for this distinctiveness is presently unknown, it is possible that Bx has a reduced ability to adhere to cells or evade/suppress immune responses, which might relate to particular proteins, such as the variant erythrocyte surface antigens (VESAs. Results We sequenced and annotated the 8.4 Mb nuclear draft genome of Bx and compared it with those of B. bovis and B. bigemina by synteny analysis; we also investigated the genetic relationship of Bx with selected Babesia species and related apicomplexans for which genomic datasets are available, and explored the VESA complement in Bx. Conclusions The availability of the Bx genome now provides unique opportunities to elucidate aspects of the molecular biology, biochemistry and physiology of Bx, and to explore the reason(s for its limited virulence and/or apparent ability to evade immune attack by the host animal. Moreover, the present genomic resource and an in vitro culture system for Bx raises the prospect of establishing a functional genomic platform to explore essential genes as new intervention targets against babesiosis.

Genomic resources for a unique, low-virulence Babesia taxon from China.

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Guan, Guiquan; Korhonen, Pasi K; Young, Neil D; Koehler, Anson V; Wang, Tao; Li, Youquan; Liu, Zhijie; Luo, Jianxun; Yin, Hong; Gasser, Robin B

2016-10-27

Babesiosis is a socioeconomically important tick-borne disease of animals (including humans) caused by haemoprotozoan parasites. The severity of babesiosis relates to host and parasite factors, particularly virulence/pathogenicity. Although Babesia bovis is a particularly pathogenic species of cattle, there are species of Babesia of ruminants that have limited pathogenicity. For instance, the operational taxonomic unit Babesia sp. Xinjiang (abbreviated here as Bx) of sheep from China is substantially less virulent/pathogenic than B. bovis is in cattle. Although the reason for this distinctiveness is presently unknown, it is possible that Bx has a reduced ability to adhere to cells or evade/suppress immune responses, which might relate to particular proteins, such as the variant erythrocyte surface antigens (VESAs). We sequenced and annotated the 8.4 Mb nuclear draft genome of Bx and compared it with those of B. bovis and B. bigemina by synteny analysis; we also investigated the genetic relationship of Bx with selected Babesia species and related apicomplexans for which genomic datasets are available, and explored the VESA complement in Bx. The availability of the Bx genome now provides unique opportunities to elucidate aspects of the molecular biology, biochemistry and physiology of Bx, and to explore the reason(s) for its limited virulence and/or apparent ability to evade immune attack by the host animal. Moreover, the present genomic resource and an in vitro culture system for Bx raises the prospect of establishing a functional genomic platform to explore essential genes as new intervention targets against babesiosis.

Evolution of viral virulence: empirical studies

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Kurath, Gael; Wargo, Andrew R.

2016-01-01

The concept of virulence as a pathogen trait that can evolve in response to selection has led to a large body of virulence evolution theory developed in the 1980-1990s. Various aspects of this theory predict increased or decreased virulence in response to a complex array of selection pressures including mode of transmission, changes in host, mixed infection, vector-borne transmission, environmental changes, host vaccination, host resistance, and co-evolution of virus and host. A fundamental concept is prediction of trade-offs between the costs and benefits associated with higher virulence, leading to selection of optimal virulence levels. Through a combination of observational and experimental studies, including experimental evolution of viruses during serial passage, many of these predictions have now been explored in systems ranging from bacteriophage to viruses of plants, invertebrates, and vertebrate hosts. This chapter summarizes empirical studies of viral virulence evolution in numerous diverse systems, including the classic models myxomavirus in rabbits, Marek's disease virus in chickens, and HIV in humans. Collectively these studies support some aspects of virulence evolution theory, suggest modifications for other aspects, and show that predictions may apply in some virus:host interactions but not in others. Finally, we consider how virulence evolution theory applies to disease management in the field.

Phylogenetic assessment reveals continuous evolution and circulation of pigeon-derived virulent avian avulaviruses 1 in Eastern Europe, Asia, and Africa.

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Sabra, Mahmoud; Dimitrov, Kiril M; Goraichuk, Iryna V; Wajid, Abdul; Sharma, Poonam; Williams-Coplin, Dawn; Basharat, Asma; Rehmani, Shafqat F; Muzyka, Denys V; Miller, Patti J; Afonso, Claudio L

2017-09-26

The remarkable diversity and mobility of Newcastle disease viruses (NDV) includes virulent viruses of genotype VI. These viruses are often referred to as pigeon paramyxoviruses 1 because they are normally isolated and cause clinical disease in birds from the Columbidae family. Genotype VI viruses occasionally infect, and may also cause clinical disease in poultry. Thus, the evolution, current spread and detection of these viruses are relevant to avian health. Here, we describe the isolation and genomic characterization of six Egyptian (2015), four Pakistani (2015), and two Ukrainian (2007, 2013) recent pigeon-derived NDV isolates of sub-genotype VIg. These viruses are closely related to isolates from Kazakhstan, Nigeria and Russia. In addition, eight genetically related NDV isolates from Pakistan (2014-2016) that define a new sub-genotype (VIm) are described. All of these viruses, and the ancestral Bulgarian (n = 2) and South Korean (n = 2) viruses described here, have predicted virulent cleavage sites of the fusion protein, and those selected for further characterization have intracerebral pathogenicity index assay values characteristic of NDV of genotype VI (1.31 to 1.48). A validated matrix gene real-time RT-PCR (rRT-PCR) NDV test detect all tested isolates. However, the validated rRT-PCR test that is normally used to identify the virulent fusion gene fails to detect the Egyptian and Ukrainian viruses due to mismatches in primers and probe. A new rapid rRT-PCR test to determine the presence of virulent cleavage sites for viruses from sub-genotypes VIg was developed and evaluated on these and other viruses. We describe the almost simultaneous circulation and continuous evolution of genotype VI Newcastle disease viruses in distant locations, suggesting epidemiological connections among three continents. As pigeons are not migratory, this study suggests the need to understand the possible role of human activity in the dispersal of these viruses. Complete

Identification and characterization of an operon, msaABCR, that controls virulence and biofilm development in Staphylococcus aureus.

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Sahukhal, Gyan S; Elasri, Mohamed O

2014-06-11

Community-acquired, methicillin-resistant Staphylococcus aureus strains often cause localized infections in immunocompromised hosts, but some strains show enhanced virulence leading to severe infections even among healthy individuals with no predisposing risk factors. The genetic basis for this enhanced virulence has yet to be determined. S. aureus possesses a wide variety of virulence factors, the expression of which is carefully coordinated by a variety of regulators. Several virulence regulators have been well characterized, but others have yet to be thoroughly investigated. Previously, we identified the msa gene as a regulator of several virulence genes, biofilm development, and antibiotic resistance. We also found evidence of the involvement of upstream genes in msa function. To investigate the mechanism of regulation of the msa gene (renamed msaC), we examined the upstream genes whose expression was affected by its deletion. We showed that msaC is part of a newly defined four-gene operon (msaABCR), in which msaC is a non-protein-coding RNA that is essential for the function of the operon. Furthermore, we found that an antisense RNA (msaR) is complementary to the 5' end of the msaB gene and is expressed in a growth phase-dependent manner suggesting that it is involved in regulation of the operon. These findings allow us to define a new operon that regulates fundamental phenotypes in S. aureus such as biofilm development and virulence. Characterization of the msaABCR operon will allow us to investigate the mechanism of function of this operon and the role of the individual genes in regulation and interaction with its targets. This study identifies a new element in the complex regulatory circuits in S. aureus, and our findings may be therapeutically relevant.

Type IV pili in Francisella – A virulence trait in an intracellular pathogen

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Emelie eNäslund Salomonsson

2011-02-01

Full Text Available Francisella tularensis is a highly virulent intracellular human pathogen that is capable of rapid proliferation in the infected host. Mutants affected in intracellular survival and growth are highly attenuated which highlights the importance of the intracellular phase of the infection. Genomic analysis has revealed that Francisella encodes all genes required for expression of functional type IV pili (Tfp, and in this focused review we summarise recent findings regarding this system in the pathogenesis of tularemia. Tfp are dynamic adhesive structures that have been identified as major virulence determinants in several human pathogens, but it is not obvious what role these structures could have in an intracellular pathogen like Francisella. In the human pathogenic strains, genes required for secretion and assembly of Tfp and one pilin, PilA, have shown to be required for full virulence. Importantly, specific genetic differences have been identified between the different Francisella subspecies where in the most pathogenic type A variants all genes are intact while several Tfp genes are pseudogenes in the less pathogenic type B strains. This suggests that there has been a selection for expression of Tfp with different properties in the different subspecies. There is also a possibility that the genetic differences reflect adaption to different environmental niches of the subspecies and plays a role in transmission of tularemia. This is also in line with recent findings where Tfp pilins are found to be glycosylated which could reflect a role for Tfp in the environment to promote survival and transmission. We are still far from understanding the role of Tfp in virulence and transmission of tularemia, but with the genomic information and genetic tools available we are in a good position to address these issues in the future.

Genome-wide identification of Pseudomonas aeruginosa virulence-related genes using a Caenorhabditis elegans infection model.

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Rhonda L Feinbaum

Full Text Available Pseudomonas aeruginosa strain PA14 is an opportunistic human pathogen capable of infecting a wide range of organisms including the nematode Caenorhabditis elegans. We used a non-redundant transposon mutant library consisting of 5,850 clones corresponding to 75% of the total and approximately 80% of the non-essential PA14 ORFs to carry out a genome-wide screen for attenuation of PA14 virulence in C. elegans. We defined a functionally diverse 180 mutant set (representing 170 unique genes necessary for normal levels of virulence that included both known and novel virulence factors. Seven previously uncharacterized virulence genes (ABC transporters PchH and PchI, aminopeptidase PepP, ATPase/molecular chaperone ClpA, cold shock domain protein PA0456, putative enoyl-CoA hydratase/isomerase PA0745, and putative transcriptional regulator PA14_27700 were characterized with respect to pigment production and motility and all but one of these mutants exhibited pleiotropic defects in addition to their avirulent phenotype. We examined the collection of genes required for normal levels of PA14 virulence with respect to occurrence in P. aeruginosa strain-specific genomic regions, location on putative and known genomic islands, and phylogenetic distribution across prokaryotes. Genes predominantly contributing to virulence in C. elegans showed neither a bias for strain-specific regions of the P. aeruginosa genome nor for putatively horizontally transferred genomic islands. Instead, within the collection of virulence-related PA14 genes, there was an overrepresentation of genes with a broad phylogenetic distribution that also occur with high frequency in many prokaryotic clades, suggesting that in aggregate the genes required for PA14 virulence in C. elegans are biased towards evolutionarily conserved genes.

Genome-wide identification of Pseudomonas aeruginosa virulence-related genes using a Caenorhabditis elegans infection model.

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Feinbaum, Rhonda L; Urbach, Jonathan M; Liberati, Nicole T; Djonovic, Slavica; Adonizio, Allison; Carvunis, Anne-Ruxandra; Ausubel, Frederick M

2012-01-01

Pseudomonas aeruginosa strain PA14 is an opportunistic human pathogen capable of infecting a wide range of organisms including the nematode Caenorhabditis elegans. We used a non-redundant transposon mutant library consisting of 5,850 clones corresponding to 75% of the total and approximately 80% of the non-essential PA14 ORFs to carry out a genome-wide screen for attenuation of PA14 virulence in C. elegans. We defined a functionally diverse 180 mutant set (representing 170 unique genes) necessary for normal levels of virulence that included both known and novel virulence factors. Seven previously uncharacterized virulence genes (ABC transporters PchH and PchI, aminopeptidase PepP, ATPase/molecular chaperone ClpA, cold shock domain protein PA0456, putative enoyl-CoA hydratase/isomerase PA0745, and putative transcriptional regulator PA14_27700) were characterized with respect to pigment production and motility and all but one of these mutants exhibited pleiotropic defects in addition to their avirulent phenotype. We examined the collection of genes required for normal levels of PA14 virulence with respect to occurrence in P. aeruginosa strain-specific genomic regions, location on putative and known genomic islands, and phylogenetic distribution across prokaryotes. Genes predominantly contributing to virulence in C. elegans showed neither a bias for strain-specific regions of the P. aeruginosa genome nor for putatively horizontally transferred genomic islands. Instead, within the collection of virulence-related PA14 genes, there was an overrepresentation of genes with a broad phylogenetic distribution that also occur with high frequency in many prokaryotic clades, suggesting that in aggregate the genes required for PA14 virulence in C. elegans are biased towards evolutionarily conserved genes.

Helicobacter pylori virulence and cancer pathogenesis.

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Yamaoka, Yoshio; Graham, David Y

2014-06-01

Helicobacter pylori is human gastric pathogen that causes chronic and progressive gastric mucosal inflammation and is responsible for the gastric inflammation-associated diseases, gastric cancer and peptic ulcer disease. Specific outcomes reflect the interplay between host-, environmental- and bacterial-specific factors. Progress in understanding putative virulence factors in disease pathogenesis has been limited and many false leads have consumed scarce resources. Few in vitro-in vivo correlations or translational applications have proved clinically relevant. Reported virulence factor-related outcomes reflect differences in relative risk of disease rather than specificity for any specific outcome. Studies of individual virulence factor associations have provided conflicting results. Since virulence factors are linked, studies of groups of putative virulence factors are needed to provide clinically useful information. Here, the authors discuss the progress made in understanding the role of H. pylori virulence factors CagA, vacuolating cytotoxin, OipA and DupA in disease pathogenesis and provide suggestions for future studies.

Sequence analysis-based characterization and identification of neurovirulence-associated variants of 36 EV71 strains from China.

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Xu, Jun; Wang, Fang; Zhao, Desheng; Liu, Jiang; Su, Hong; Wang, Baolong

2018-03-30

Enterovirus 71 (EV71) is the main pathogen of hand-foot-mouth disease (HFMD) and causes several neurological complications. As new strains of EV71 are constantly discovered, it is important to understand the genomic characteristics of the viruses and the mechanism of virulence. Herein, we isolated five strains of EV71 from HFMD patients with or without neurovirulence and sequenced their whole genomes. We then performed whole genome sequence analysis of totally 36 EV71 strains. The phylogenetic analysis of the VP1 region revealed all five isolated strains are clustered into C4a of C4 subgenotype. In addition, by comparing the complete genome sequences of 36 strains, 253 variable amino acid positions were found, 14 of which were identified to be associated with neurovirulence (P < 0.05). Moreover, a similar pattern of amino acid variants combination was identified in four strains without neurovirulence, indicating this type of variant pattern might be associated with avirulence. The strains with neurovirulence appeared to be distinguished from those without neurovirulence by the variants in VP1 and P2 regions, implying VP1 and P2 are the important regions associated with neurovirulence. Indeed, 3-D modeling of VP1 and P2 regions of non-neurovirulent and neurovirulent strains revealed that the different variants resulted in different protein structures and amino acid composition of ligand binding site, which might account for their difference in neurovirulence. In summary, our study reveals 14 variable amino acid positions of VP1, P2 and P3 regions are related to the virulence and that mutations in the capsid proteins of EV71 might contribute to neurovirulence. © 2018 Wiley Periodicals, Inc.

De Novo Synthesis of Phosphorylated Triblock Copolymers with Pathogen Virulence-Suppressing Properties That Prevent Infection-Related Mortality

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Mao, Jun; Zaborin, Alexander; Poroyko, Valeriy; Goldfeld, David; Lynd, Nathaniel A. [McKetta; Chen, Wei [Institute; Tirrell, Matthew V. [Institute; Zaborina, Olga; Alverdy, John C.

2017-07-31

Phosphate is a key and universal "cue" in response to which bacteria either enhance their virulence when local phosphate is scarce or downregulate it when phosphate is adundant. Phosphate becomes depleted in the mammalian gut following physiologic stress and serves as a major trigger for colonizing bacteria to express virulence. This process cannot be reversed with oral supplementation of inorganic phosphate because it is nearly completely absorbed in the proximal small intestine. In the present study, we describe the de novo synthesis of phosphorylated polyethylene glycol compounds with three defined ABA (hydrophilic/-phobic/-philic) structures, ABA-PEG10k-Pi10, ABA-PEG16k-Pi14, and ABA-PEG20k-Pi20, and linear polymer PEG20k-Pi20 absent of the hydrophobic block. The 10k, 16k, and 20k demonstrate the molecular weights of the poly(ethylene glycol) block, and Pi10, Pi14, and Pi20 represent the repeating units of phosphate. Polymers were tested for their efficacy against Pseudomonas aeruginosa virulence in vitro and in vivo by assessing the expression of the phosphate sensing protein PstS, the production of key virulence factor pyocyanin, and Caenorhabditis elegans killing assays. Results indicate that all phosphorylated polymers suppressed phosphate sensing, virulence expression, and lethality in P. aeruginosa. Among all of the phosphorylated polymers, ABA-PEG20kPi20 displayed the greatest degree of protection against P. aeruginosa. To define the role of the hydrophobic core in ABA-PEG20k-Pi20 in the above response, we synthesized PEG20k-Pi20 in which the hydrophobic core is absent. Results indicate that the hypdrophobic core of ABA-PEG20k-Pi20 is a key structure in its protective effect against P. aeruginosa, in part due to its ability to coat the surface of bacteria. Taken together, the synthesis of novel polymers with defined structures and levels of phosphorylation may elucidate their antivirulence action against clinically important and lethal pathogens such as

The subtilisin-like protease AprV2 is required for virulence and uses a novel disulphide-tethered exosite to bind substrates.

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Ruth M Kennan

Full Text Available Many bacterial pathogens produce extracellular proteases that degrade the extracellular matrix of the host and therefore are involved in disease pathogenesis. Dichelobacter nodosus is the causative agent of ovine footrot, a highly contagious disease that is characterized by the separation of the hoof from the underlying tissue. D. nodosus secretes three subtilisin-like proteases whose analysis forms the basis of diagnostic tests that differentiate between virulent and benign strains and have been postulated to play a role in virulence. We have constructed protease mutants of D. nodosus; their analysis in a sheep virulence model revealed that one of these enzymes, AprV2, was required for virulence. These studies challenge the previous hypothesis that the elastase activity of AprV2 is important for disease progression, since aprV2 mutants were virulent when complemented with aprB2, which encodes a variant that has impaired elastase activity. We have determined the crystal structures of both AprV2 and AprB2 and characterized the biological activity of these enzymes. These data reveal that an unusual extended disulphide-tethered loop functions as an exosite, mediating effective enzyme-substrate interactions. The disulphide bond and Tyr92, which was located at the exposed end of the loop, were functionally important. Bioinformatic analyses suggested that other pathogenic bacteria may have proteases that utilize a similar mechanism. In conclusion, we have used an integrated multidisciplinary combination of bacterial genetics, whole animal virulence trials in the original host, biochemical studies, and comprehensive analysis of crystal structures to provide the first definitive evidence that the extracellular secreted proteases produced by D. nodosus are required for virulence and to elucidate the molecular mechanism by which these proteases bind to their natural substrates. We postulate that this exosite mechanism may be used by proteases produced by

Calcineurin Targets Involved in Stress Survival and Fungal Virulence.

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Hee-Soo Park

2016-09-01

to be characterized as calcineurin targets in other organisms. These findings further highlight C. neoformans as an outstanding model to define calcineurin-responsive virulence networks as targets for antifungal therapy.

Sample pooling for real-time PCR detection and virulence determination of the footrot pathogen Dichelobacter nodosus.

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Frosth, Sara; König, Ulrika; Nyman, Ann-Kristin; Aspán, Anna

2017-09-01

Dichelobacter nodosus is the principal cause of ovine footrot and strain virulence is an important factor in disease severity. Therefore, detection and virulence determination of D. nodosus is important for proper diagnosis of the disease. Today this is possible by real-time PCR analysis. Analysis of large numbers of samples is costly and laborious; therefore, pooling of individual samples is common in surveillance programs. However, pooling can reduce the sensitivity of the method. The aim of this study was to develop a pooling method for real-time PCR analysis that would allow sensitive detection and simultaneous virulence determination of D. nodosus. A total of 225 sheep from 17 flocks were sampled using ESwabs within the Swedish Footrot Control Program in 2014. Samples were first analysed individually and then in pools of five by real-time PCR assays targeting the 16S rRNA and aprV2/B2 genes of D. nodosus. Each pool consisted of four negative and one positive D. nodosus samples with varying amounts of the bacterium. In the individual analysis, 61 (27.1%) samples were positive in the 16S rRNA and the aprV2/B2 PCR assays and 164 (72.9%) samples were negative. All samples positive in the aprV2/B2 PCR-assay were of aprB2 variant. The pooled analysis showed that all 41 pools were also positive for D. nodosus 16S rRNA and the aprB2 variant. The diagnostic sensitivity for pooled and individual samples was therefore similar. Our method includes concentration of the bacteria before DNA-extraction. This may account for the maintenance of diagnostic sensitivity. Diagnostic sensitivity in the real-time PCR assays of the pooled samples were comparable to the sensitivity obtained for individually analysed samples. Even sub-clinical infections were able to be detected in the pooled PCR samples which is important for control of the disease. This method may therefore be implemented in footrot control programs where it can replace analysis of individual samples.

Integrative genomic analysis identifies isoleucine and CodY as regulators of Listeria monocytogenes virulence.

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Lior Lobel

2012-09-01

Full Text Available Intracellular bacterial pathogens are metabolically adapted to grow within mammalian cells. While these adaptations are fundamental to the ability to cause disease, we know little about the relationship between the pathogen's metabolism and virulence. Here we used an integrative Metabolic Analysis Tool that combines transcriptome data with genome-scale metabolic models to define the metabolic requirements of Listeria monocytogenes during infection. Twelve metabolic pathways were identified as differentially active during L. monocytogenes growth in macrophage cells. Intracellular replication requires de novo synthesis of histidine, arginine, purine, and branch chain amino acids (BCAAs, as well as catabolism of L-rhamnose and glycerol. The importance of each metabolic pathway during infection was confirmed by generation of gene knockout mutants in the respective pathways. Next, we investigated the association of these metabolic requirements in the regulation of L. monocytogenes virulence. Here we show that limiting BCAA concentrations, primarily isoleucine, results in robust induction of the master virulence activator gene, prfA, and the PrfA-regulated genes. This response was specific and required the nutrient responsive regulator CodY, which is known to bind isoleucine. Further analysis demonstrated that CodY is involved in prfA regulation, playing a role in prfA activation under limiting conditions of BCAAs. This study evidences an additional regulatory mechanism underlying L. monocytogenes virulence, placing CodY at the crossroads of metabolism and virulence.

A gacS deletion in Pseudomonas aeruginosa cystic fibrosis isolate CHA shapes its virulence.

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Khady Mayebine Sall

Full Text Available Pseudomonas aeruginosa, a human opportunistic pathogen, is capable of provoking acute and chronic infections that are associated with defined sets of virulence factors. During chronic infections, the bacterium accumulates mutations that silence some and activate other genes. Here we show that the cystic fibrosis isolate CHA exhibits a unique virulence phenotype featuring a mucoid morphology, an active Type III Secretion System (T3SS, hallmark of acute infections, and no Type VI Secretion System (H1-T6SS. This virulence profile is due to a 426 bp deletion in the 3' end of the gacS gene encoding an essential regulatory protein. The absence of GacS disturbs the Gac/Rsm pathway leading to depletion of the small regulatory RNAs RsmY/RsmZ and, in consequence, to expression of T3SS, while switching off the expression of H1-T6SS and Pel polysaccharides. The CHA isolate also exhibits full ability to swim and twitch, due to active flagellum and Type IVa pili. Thus, unlike the classical scheme of balance between virulence factors, clinical strains may adapt to a local niche by expressing both alginate exopolysaccharide, a hallmark of membrane stress that protects from antibiotic action, host defences and phagocytosis, and efficient T3S machinery that is considered as an aggressive virulence factor.

Interplay among Resistance Profiles, High-Risk Clones, and Virulence in the Caenorhabditis elegans Pseudomonas aeruginosa Infection Model.

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Sánchez-Diener, Irina; Zamorano, Laura; López-Causapé, Carla; Cabot, Gabriel; Mulet, Xavier; Peña, Carmen; Del Campo, Rosa; Cantón, Rafael; Doménech-Sánchez, Antonio; Martínez-Martínez, Luis; Arcos, Susana C; Navas, Alfonso; Oliver, Antonio

2017-12-01

The increasing prevalence of nosocomial infections produced by multidrug-resistant (MDR) or extensively drug-resistant (XDR) Pseudomonas aeruginosa is frequently linked to widespread international strains designated high-risk clones. In this work, we attempted to decipher the interplay between resistance profiles, high-risk clones, and virulence, testing a large ( n = 140) collection of well-characterized P. aeruginosa isolates from different sources (bloodstream infections, nosocomial outbreaks, cystic fibrosis, and the environment) in a Caenorhabditis elegans infection model. Consistent with previous data, we documented a clear inverse correlation between antimicrobial resistance and virulence in the C. elegans model. Indeed, the lowest virulence was linked to XDR profiles, which were typically linked to defined high-risk clones. However, virulence varied broadly depending on the involved high-risk clone; it was high for sequence type 111 (ST111) and ST235 but very low for ST175. The highest virulence of ST235 could be attributed to its exoU + type III secretion system (TTSS) genotype, which was found to be linked with higher virulence in our C. elegans model. Other markers, such as motility or pigment production, were not essential for virulence in the C. elegans model but seemed to be related with the higher values of the statistical normalized data. In contrast to ST235, the ST175 high-risk clone, which is widespread in Spain and France, seems to be associated with a particularly low virulence in the C. elegans model. Moreover, the previously described G154R AmpR mutation, prevalent in ST175, was found to contribute to the reduced virulence, although it was not the only factor involved. Altogether, our results provide a major step forward for understanding the interplay between P. aeruginosa resistance profiles, high-risk clones, and virulence. Copyright © 2017 American Society for Microbiology.

PfSETvs methylation of histone H3K36 represses virulence genes in Plasmodium falciparum

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Jiang, Lubin; Mu, Jianbing; Zhang, Qingfeng

2013-01-01

The variant antigen Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), which is expressed on the surface of P. falciparum-infected red blood cells, is a critical virulence factor for malaria. Each parasite has 60 antigenically distinct var genes that each code for a different PfEMP1...... parasite nuclei and their expression as proteins on the surface of individual infected red blood cells. PfSETvs-dependent H3K36me3 is present along the entire gene body, including the transcription start site, to silence var genes. With low occupancy of PfSETvs at both the transcription start site of var...... protein. During infection the clonal parasite population expresses only one gene at a time before switching to the expression of a new variant antigen as an immune-evasion mechanism to avoid the host antibody response. The mechanism by which 59 of the 60 var genes are silenced remains largely unknown...

Sample collection of virulent and non-virulent B. anthracis and Y. pestis for bioforensics analysis

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Hong-geller, Elizabeth [Los Alamos National Laboratory; Valdez, Yolanda E [Los Alamos National Laboratory; Shou, Yulin [Los Alamos National Laboratory; Yoshida, Thomas M [Los Alamos National Laboratory; Marrone, Babetta L [Los Alamos National Laboratory; Dunbar, John [Los Alamos National Laboratory

2009-01-01

Validated sample collection methods are needed for recovery of microbial evidence in the event of accidental or intentional release of biological agents into the environment. To address this need, we evaluated the sample recovery efficiencies of two collection methods -- swabs and wipes -- for both non-virulent and virulent strains of B. anthracis and Y. pestis from four types of non-porous surfaces: two hydrophilic surfaces, stainless steel and glass, and two hydrophobic surfaces, vinyl and plastic. Sample recovery was quantified using Real-time qPCR to assay for intact DNA signatures. We found no consistent difference in collection efficiency between swabs or wipes. Furthermore, collection efficiency was more surface-dependent for virulent strains than non-virulent strains. For the two non-virulent strains, B. anthracis Sterne and Y. pestis A1122, collection efficiency was approximately 100% and 1 %, respectively, from all four surfaces. In contrast, recovery of B. anthracis Ames spores and Y. pestis C092 from vinyl and plastic was generally lower compared to collection from glass or stainless steel, suggesting that surface hydrophobicity may playa role in the strength of pathogen adhesion. The surface-dependent collection efficiencies observed with the virulent strains may arise from strain-specific expression of capsular material or other cell surface receptors that alter cell adhesion to specific surfaces. These findings contribute to validation of standard bioforensics procedures and emphasize the importance of specific strain and surface interactions in pathogen detection.

Acidic pH and divalent cation sensing by PhoQ are dispensable for systemic salmonellae virulence.

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Hicks, Kevin G; Delbecq, Scott P; Sancho-Vaello, Enea; Blanc, Marie-Pierre; Dove, Katja K; Prost, Lynne R; Daley, Margaret E; Zeth, Kornelius; Klevit, Rachel E; Miller, Samuel I

2015-05-23

Salmonella PhoQ is a histidine kinase with a periplasmic sensor domain (PD) that promotes virulence by detecting the macrophage phagosome. PhoQ activity is repressed by divalent cations and induced in environments of acidic pH, limited divalent cations, and cationic antimicrobial peptides (CAMP). Previously, it was unclear which signals are sensed by salmonellae to promote PhoQ-mediated virulence. We defined conformational changes produced in the PhoQ PD on exposure to acidic pH that indicate structural flexibility is induced in α-helices 4 and 5, suggesting this region contributes to pH sensing. Therefore, we engineered a disulfide bond between W104C and A128C in the PhoQ PD that restrains conformational flexibility in α-helices 4 and 5. PhoQ(W104C-A128C) is responsive to CAMP, but is inhibited for activation by acidic pH and divalent cation limitation. phoQ(W104C-A128C) Salmonella enterica Typhimurium is virulent in mice, indicating that acidic pH and divalent cation sensing by PhoQ are dispensable for virulence.

Differential expression of hemoglobin receptor, HmbR, between carriage and invasive isolates of Neisseria meningitidis contributes to virulence: lessons from a clonal outbreak.

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Sevestre, Julien; Diene, Seydina M; Aouiti-Trabelsi, Myriam; Deghmane, Ala-Eddine; Tournier, Isabelle; François, Patrice; Caron, François; Taha, Muhamed-Kheir

2018-04-11

Carriage and invasion balance in the pathogenesis of Neisseria meningitidis was analyzed during a recent clonal outbreak of meningococcal B in Normandy, France, that offered the opportunity to compare six isolates undistinguable by conventional typing (B:P1.7,16:F3-3/ST-32) isolated from invasive disease or pharyngeal asymptomatic carriage. Data from animal model (transgenic mice rendered susceptible to N. meningitidis infection) showed an absence of virulence for two non-capsulated carriage isolates, an intermediate virulence for two capsulated carriage isolates and a marked virulence for two capsulated invasive isolates. This differential pathogenesis well correlated with whole genome sequencing analysis that clustered together both isolates of each group together, forming their own arm within the Norman cluster. Gene-by-gene analysis specified that genes involved in iron acquisition were among the elements differentially represented in cluster of invasive isolates compared to cluster of capsulated carriage isolates. The hemoglobin receptor encoding gene hmbR was in an ON-phase in the capsulated invasive isolates while carriage capsulated isolates were in an OFF-phase. An ON-phase variant of a capsulated carriage isolate showed enhanced virulence. These data underline the role of phase variation (ON/OFF) of HmbR in the balance between disease isolates/carriage isolates.

Crystal structure of Bacillus anthracis virulence regulator AtxA and effects of phosphorylated histidines on multimerization and activity.

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Hammerstrom, Troy G; Horton, Lori B; Swick, Michelle C; Joachimiak, Andrzej; Osipiuk, Jerzy; Koehler, Theresa M

2015-02-01

The Bacillus anthracis virulence regulator AtxA controls transcription of the anthrax toxin genes and capsule biosynthetic operon. AtxA activity is elevated during growth in media containing glucose and CO(2)/bicarbonate, and there is a positive correlation between the CO(2)/bicarbonate signal, AtxA activity and homomultimerization. AtxA activity is also affected by phosphorylation at specific histidines. We show that AtxA crystallizes as a dimer. Distinct folds associated with predicted DNA-binding domains (HTH1 and HTH2) and phosphoenolpyruvate: carbohydrate phosphotransferase system-regulated domains (PRD1 and PRD2) are apparent. We tested AtxA variants containing single and double phosphomimetic (His→Asp) and phosphoablative (His→Ala) amino acid changes for activity in B. anthracis cultures and for protein-protein interactions in cell lysates. Reduced activity of AtxA H199A, lack of multimerization and activity of AtxAH379D variants, and predicted structural changes associated with phosphorylation support a model for control of AtxA function. We propose that (i) in the AtxA dimer, phosphorylation of H199 in PRD1 affects HTH2 positioning, influencing DNA-binding; and (ii) phosphorylation of H379 in PRD2 disrupts dimer formation. The AtxA structure is the first reported high-resolution full-length structure of a PRD-containing regulator, and can serve as a model for proteins of this family, especially those that link virulence to bacterial metabolism. © 2014 John Wiley & Sons Ltd.

Plasmid-Mediated Antibiotic Resistance and Virulence in Gram-negatives: the Klebsiella pneumoniae Paradigm.

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Ramirez, Maria S; Traglia, German M; Lin, David L; Tran, Tung; Tolmasky, Marcelo E

Plasmids harbor genes coding for specific functions including virulence factors and antibiotic resistance that permit bacteria to survive the hostile environment found in the host and resist treatment. Together with other genetic elements such as integrons and transposons, and using a variety of mechanisms, plasmids participate in the dissemination of these traits resulting in the virtual elimination of barriers among different kinds of bacteria. In this article we review the current information about physiology and role in virulence and antibiotic resistance of plasmids from the gram-negative opportunistic pathogen Klebsiella pneumoniae . This bacterium has acquired multidrug resistance and is the causative agent of serious communityand hospital-acquired infections. It is also included in the recently defined ESKAPE group of bacteria that cause most of US hospital infections.

Differential protein accumulations in isolates of the strawberry wilt pathogen Fusarium oxysporum f. sp. fragariae differing in virulence.

Science.gov (United States)

Fang, Xiangling; Barbetti, Martin J

2014-08-28

This study was conducted to define differences in Fusarium oxysporum f. sp. fragariae (Fof) isolates with different virulence efficiency to strawberry at the proteome level, in combination with their differences in mycelial growth, conidial production and germination. Comparative proteome analyses revealed substantial differences in mycelial proteomes between Fof isolates, where the 54 differentially accumulated protein spots were consistently over-accumulated or exclusively in the highly virulent isolate. These protein spots were identified through MALDI-TOF/TOF mass spectrometry analyses, and the identified proteins were mainly related to primary and protein metabolism, antioxidation, electron transport, cell cycle and transcription based on their putative functions. Proteins of great potential as Fof virulence factors were those involved in ubiquitin/proteasome-mediated protein degradation and reactive oxygen species detoxification; the hydrolysis-related protein haloacid dehalogenase superfamily hydrolase; 3,4-dihydroxy-2-butanone 4-phosphate synthase associated with riboflavin biosynthesis; and those exclusive to the highly virulent isolate. In addition, post-translational modifications may also make an important contribution to Fof virulence. F. oxysporum f. sp. fragariae (Fof), the causal agent of Fusarium wilt in strawberry, is a serious threat to commercial strawberry production worldwide. However, factors and mechanisms contributing to Fof virulence remained unknown. This study provides knowledge of the molecular basis for the differential expression of virulence in Fof, allowing new possibilities towards developing alternative and more effective strategies to manage Fusarium wilt. Copyright © 2014 Elsevier B.V. All rights reserved.

Microsatellite Instability Use in Mismatch Repair Gene Sequence Variant Classification

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Bryony A. Thompson

2015-03-01

Full Text Available Inherited mutations in the DNA mismatch repair genes (MMR can cause MMR deficiency and increased susceptibility to colorectal and endometrial cancer. Microsatellite instability (MSI is the defining molecular signature of MMR deficiency. The clinical classification of identified MMR gene sequence variants has a direct impact on the management of patients and their families. For a significant proportion of cases sequence variants of uncertain clinical significance (also known as unclassified variants are identified, constituting a challenge for genetic counselling and clinical management of families. The effect on protein function of these variants is difficult to interpret. The presence or absence of MSI in tumours can aid in determining the pathogenicity of associated unclassified MMR gene variants. However, there are some considerations that need to be taken into account when using MSI for variant interpretation. The use of MSI and other tumour characteristics in MMR gene sequence variant classification will be explored in this review.

Pathogenesis of virulent and attenuated foot-and-mouth disease virus in cattle.

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Arzt, Jonathan; Pacheco, Juan M; Stenfeldt, Carolina; Rodriguez, Luis L

2017-05-02

Understanding the mechanisms of attenuation and virulence of foot-and-mouth disease virus (FMDV) in the natural host species is critical for development of next-generation countermeasures such as live-attenuated vaccines. Functional genomics analyses of FMDV have identified few virulence factors of which the leader proteinase (L pro ) is the most thoroughly investigated. Previous work from our laboratory has characterized host factors in cattle inoculated with virulent FMDV and attenuated mutant strains with transposon insertions within L pro . In the current study, the characteristics defining virulence of FMDV in cattle were further investigated by comparing the pathogenesis of a mutant, attenuated strain (FMDV-Mut) to the parental, virulent virus from which the mutant was derived (FMDV-WT). The only difference between the two viruses was an insertion mutation in the inter-AUG region of the leader proteinase of FMDV-Mut. All cattle were infected by simulated-natural, aerosol inoculation. Both viruses were demonstrated to establish primary infection in the nasopharyngeal mucosa with subsequent dissemination to the lungs. Immunomicroscopic localization of FMDV antigens indicated that both viruses infected superficial epithelial cells of the nasopharynx and lungs. The critical differences between the two viruses were a more rapid establishment of infection by FMDV-WT and quantitatively greater virus loads in secretions and infected tissues compared to FMDV-Mut. The slower replicating FMDV-Mut established a subclinical infection that was limited to respiratory epithelial sites, whereas the faster replication of FMDV-WT facilitated establishment of viremia, systemic dissemination of infection, and clinical disease. The mutant FMDV was capable of achieving all the same early pathogenesis landmarks as FMDV-WT, but was unable to establish systemic infection. The precise mechanism of attenuation remains undetermined; but current data suggests that the impaired replication

A global evolutionary and metabolic analysis of human obesity gene risk variants.

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Castillo, Joseph J; Hazlett, Zachary S; Orlando, Robert A; Garver, William S

2017-09-05

It is generally accepted that the selection of gene variants during human evolution optimized energy metabolism that now interacts with our obesogenic environment to increase the prevalence of obesity. The purpose of this study was to perform a global evolutionary and metabolic analysis of human obesity gene risk variants (110 human obesity genes with 127 nearest gene risk variants) identified using genome-wide association studies (GWAS) to enhance our knowledge of early and late genotypes. As a result of determining the mean frequency of these obesity gene risk variants in 13 available populations from around the world our results provide evidence for the early selection of ancestral risk variants (defined as selection before migration from Africa) and late selection of derived risk variants (defined as selection after migration from Africa). Our results also provide novel information for association of these obesity genes or encoded proteins with diverse metabolic pathways and other human diseases. The overall results indicate a significant differential evolutionary pattern for the selection of obesity gene ancestral and derived risk variants proposed to optimize energy metabolism in varying global environments and complex association with metabolic pathways and other human diseases. These results are consistent with obesity genes that encode proteins possessing a fundamental role in maintaining energy metabolism and survival during the course of human evolution. Copyright © 2017. Published by Elsevier B.V.

Recombinant hybrid infectious hematopoietic necrosis virus (IHNV) carrying viral haemorrhagic septicaemia virus (VHSV) G or NV genes show different virulence properities

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Einer-Jensen, Katja; Biacchesi, S.; Stegmann, Anders

. By a reverse genetics approach using the related novirrhabdovirus infectious hematopoietic necrosis virus (IHNV) as basis, four hybrid IHNV-VHSV variants were generated. These chimeric variants included substitution of the IHNV glyco(G) or nonstrutrual (Nv) protein with the corresponding G or Nv-protein from......Viral haemorrhagic septicaemia virus (VHSV) is the economically most important viral disease in European rainbow trout farming. The virus was introduced to fresh water farms in the 1950ies from a reservoir of VHSV in the marine environment. Isolates from wild marine fish and fresh water farms...... are difficult to distinguish serologically but they show different virulence profiles: marine isolates typically cause little or no mortality in rainbow trout fry following experimental waterborne challenge, while freshwater isolates often kill the majority of the fish. Genetic analysis reveal that the change...

Metabolic Genetic Screens Reveal Multidimensional Regulation of Virulence Gene Expression in Listeria monocytogenes and an Aminopeptidase That Is Critical for PrfA Protein Activation.

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Friedman, Sivan; Linsky, Marika; Lobel, Lior; Rabinovich, Lev; Sigal, Nadejda; Herskovits, Anat A

2017-06-01

Listeria monocytogenes is an environmental saprophyte and intracellular bacterial pathogen. Upon invading mammalian cells, the bacterium senses abrupt changes in its metabolic environment, which are rapidly transduced to regulation of virulence gene expression. To explore the relationship between L. monocytogenes metabolism and virulence, we monitored virulence gene expression dynamics across a library of genetic mutants grown under two metabolic conditions known to activate the virulent state: charcoal-treated rich medium containing glucose-1-phosphate and minimal defined medium containing limiting concentrations of branched-chain amino acids (BCAAs). We identified over 100 distinct mutants that exhibit aberrant virulence gene expression profiles, the majority of which mapped to nonessential metabolic genes. Mutants displayed enhanced, decreased, and early and late virulence gene expression profiles, as well as persistent levels, demonstrating a high plasticity in virulence gene regulation. Among the mutants, one was noteworthy for its particularly low virulence gene expression level and mapped to an X-prolyl aminopeptidase (PepP). We show that this peptidase plays a role in posttranslational activation of the major virulence regulator, PrfA. Specifically, PepP mediates recruitment of PrfA to the cytoplasmic membrane, a step identified as critical for PrfA protein activation. This study establishes a novel step in the complex mechanism of PrfA activation and further highlights the cross regulation of metabolism and virulence. Copyright © 2017 American Society for Microbiology.

Impaired Interoceptive Accuracy in Semantic Variant Primary Progressive Aphasia

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Charles R. Marshall

2017-11-01

Full Text Available BackgroundInteroception (the perception of internal bodily sensations is strongly linked to emotional experience and sensitivity to the emotions of others in healthy subjects. Interoceptive impairment may contribute to the profound socioemotional symptoms that characterize frontotemporal dementia (FTD syndromes, but remains poorly defined.MethodsPatients representing all major FTD syndromes and healthy age-matched controls performed a heartbeat counting task as a measure of interoceptive accuracy. In addition, patients had volumetric MRI for voxel-based morphometric analysis, and their caregivers completed a questionnaire assessing patients’ daily-life sensitivity to the emotions of others.ResultsInteroceptive accuracy was impaired in patients with semantic variant primary progressive aphasia relative to healthy age-matched individuals, but not in behavioral variant frontotemporal dementia and nonfluent variant primary progressive aphasia. Impaired interoceptive accuracy correlated with reduced daily-life emotional sensitivity across the patient cohort, and with atrophy of right insula, cingulate, and amygdala on voxel-based morphometry in the impaired semantic variant group, delineating a network previously shown to support interoceptive processing in the healthy brain.ConclusionInteroception is a promising novel paradigm for defining mechanisms of reduced emotional reactivity, empathy, and self-awareness in neurodegenerative syndromes and may yield objective measures for these complex symptoms.

The Central Metabolism Regulator EIIAGlc Switches Salmonella from Growth Arrest to Acute Virulence through Activation of Virulence Factor Secretion

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Alain Mazé

2014-06-01

Full Text Available The ability of Salmonella to cause disease depends on metabolic activities and virulence factors. Here, we show that a key metabolic protein, EIIAGlc, is absolutely essential for acute infection, but not for Salmonella survival, in a mouse typhoid fever model. Surprisingly, phosphorylation-dependent EIIAGlc functions, including carbohydrate transport and activation of adenylate cyclase for global regulation, do not explain this virulence phenotype. Instead, biochemical studies, in vitro secretion and translocation assays, and in vivo genetic epistasis experiments suggest that EIIAGlc binds to the type three secretion system 2 (TTSS-2 involved in systemic virulence, stabilizes its cytoplasmic part including the crucial TTSS-2 ATPase, and activates virulence factor secretion. This unexpected role of EIIAGlc reveals a striking direct link between central Salmonella metabolism and a crucial virulence mechanism.

[Approach to diagnosis and management of myeloproliferative neoplasm variants].

Science.gov (United States)

Mitsumori, Toru; Kirito, Keita

2015-08-01

Myeloproliferative neoplasm (MPN) variants are defined as relatively uncommon myeloid neoplasms which do not meet the criteria for either classical MPN or myelodysplastic syndrome. Due to the lack of specific markers, it has been challenging to accurately diagnose these malignant diseases. Recent studies have revealed new genetic abnormalities in MPN variants. These research advances are anticipated to open new approaches to not only achieving accurate diagnosis but also novel therapeutic options for these diseases.

A Burkholderia pseudomallei colony variant necessary for gastric colonization.

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Austin, C R; Goodyear, A W; Bartek, I L; Stewart, A; Sutherland, M D; Silva, E B; Zweifel, A; Vitko, N P; Tuanyok, A; Highnam, G; Mittelman, D; Keim, P; Schweizer, H P; Vázquez-Torres, A; Dow, S W C; Voskuil, M I

2015-02-03

Diverse colony morphologies are a hallmark of Burkholderia pseudomallei recovered from infected patients. We observed that stresses that inhibit aerobic respiration shifted populations of B. pseudomallei from the canonical white colony morphotype toward two distinct, reversible, yet relatively stable yellow colony variants (YA and YB). As accumulating evidence supports the importance of B. pseudomallei enteric infection and gastric colonization, we tested the response of yellow variants to hypoxia, acidity, and stomach colonization. Yellow variants exhibited a competitive advantage under hypoxic and acidic conditions and alkalized culture media. The YB variant, although highly attenuated in acute virulence, was the only form capable of colonization and persistence in the murine stomach. The accumulation of extracellular DNA (eDNA) was a characteristic of YB as observed by 4',6-diamidino-2-phenylindole (DAPI) staining of gastric tissues, as well as in an in vitro stomach model where large amounts of eDNA were produced without cell lysis. Transposon mutagenesis identified a transcriptional regulator (BPSL1887, designated YelR) that when overexpressed produced the yellow phenotype. Deletion of yelR blocked a shift from white to the yellow forms. These data demonstrate that YB is a unique B. pseudomallei pathovariant controlled by YelR that is specifically adapted to the harsh gastric environment and necessary for persistent stomach colonization. Seemingly uniform populations of bacteria often contain subpopulations that are genetically identical but display unique characteristics which offer advantages when the population is faced with infrequent but predictable stresses. The pathogen Burkholderia pseudomallei is capable of forming several reversible colony types, and it interconverted between one white type and two yellow types under certain environmental stresses. The two yellow forms exhibited distinct advantages in low-oxygen and acidic environments. One yellow

Intracellularly Induced Cyclophilins Play an Important Role in Stress Adaptation and Virulence of Brucella abortus

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García Fernández, Lucía; DelVecchio, Vito G.; Briones, Gabriel

2013-01-01

Brucella is an intracellular bacterial pathogen that causes the worldwide zoonotic disease brucellosis. Brucella virulence relies on its ability to transition to an intracellular lifestyle within host cells. Thus, this pathogen must sense its intracellular localization and then reprogram gene expression for survival within the host cell. A comparative proteomic investigation was performed to identify differentially expressed proteins potentially relevant for Brucella intracellular adaptation. Two proteins identified as cyclophilins (CypA and CypB) were overexpressed in the intracellular environment of the host cell in comparison to laboratory-grown Brucella. To define the potential role of cyclophilins in Brucella virulence, a double-deletion mutant was constructed and its resulting phenotype was characterized. The Brucella abortus ΔcypAB mutant displayed increased sensitivity to environmental stressors, such as oxidative stress, pH, and detergents. In addition, the B. abortus ΔcypAB mutant strain had a reduced growth rate at lower temperature, a phenotype associated with defective expression of cyclophilins in other microorganisms. The B. abortus ΔcypAB mutant also displays reduced virulence in BALB/c mice and defective intracellular survival in HeLa cells. These findings suggest that cyclophilins are important for Brucella virulence and survival in the host cells. PMID:23230297

A Precise Temperature-Responsive Bistable Switch Controlling Yersinia Virulence.

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Nuss, Aaron Mischa; Schuster, Franziska; Roselius, Louisa; Klein, Johannes; Bücker, René; Herbst, Katharina; Heroven, Ann Kathrin; Pisano, Fabio; Wittmann, Christoph; Münch, Richard; Müller, Johannes; Jahn, Dieter; Dersch, Petra

2016-12-01

Different biomolecules have been identified in bacterial pathogens that sense changes in temperature and trigger expression of virulence programs upon host entry. However, the dynamics and quantitative outcome of this response in individual cells of a population, and how this influences pathogenicity are unknown. Here, we address these questions using a thermosensing virulence regulator of an intestinal pathogen (RovA of Yersinia pseudotuberculosis) as a model. We reveal that this regulator is part of a novel thermoresponsive bistable switch, which leads to high- and low-invasive subpopulations within a narrow temperature range. The temperature range in which bistability is observed is defined by the degradation and synthesis rate of the regulator, and is further adjustable via a nutrient-responsive regulator. The thermoresponsive switch is also characterized by a hysteretic behavior in which activation and deactivation occurred on vastly different time scales. Mathematical modeling accurately mirrored the experimental behavior and predicted that the thermoresponsiveness of this sophisticated bistable switch is mainly determined by the thermo-triggered increase of RovA proteolysis. We further observed RovA ON and OFF subpopulations of Y. pseudotuberculosis in the Peyer's patches and caecum of infected mice, and that changes in the RovA ON/OFF cell ratio reduce tissue colonization and overall virulence. This points to a bet-hedging strategy in which the thermoresponsive bistable switch plays a key role in adapting the bacteria to the fluctuating conditions encountered as they pass through the host's intestinal epithelium and suggests novel strategies for the development of antimicrobial therapies.

A Precise Temperature-Responsive Bistable Switch Controlling Yersinia Virulence.

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Aaron Mischa Nuss

2016-12-01

Full Text Available Different biomolecules have been identified in bacterial pathogens that sense changes in temperature and trigger expression of virulence programs upon host entry. However, the dynamics and quantitative outcome of this response in individual cells of a population, and how this influences pathogenicity are unknown. Here, we address these questions using a thermosensing virulence regulator of an intestinal pathogen (RovA of Yersinia pseudotuberculosis as a model. We reveal that this regulator is part of a novel thermoresponsive bistable switch, which leads to high- and low-invasive subpopulations within a narrow temperature range. The temperature range in which bistability is observed is defined by the degradation and synthesis rate of the regulator, and is further adjustable via a nutrient-responsive regulator. The thermoresponsive switch is also characterized by a hysteretic behavior in which activation and deactivation occurred on vastly different time scales. Mathematical modeling accurately mirrored the experimental behavior and predicted that the thermoresponsiveness of this sophisticated bistable switch is mainly determined by the thermo-triggered increase of RovA proteolysis. We further observed RovA ON and OFF subpopulations of Y. pseudotuberculosis in the Peyer's patches and caecum of infected mice, and that changes in the RovA ON/OFF cell ratio reduce tissue colonization and overall virulence. This points to a bet-hedging strategy in which the thermoresponsive bistable switch plays a key role in adapting the bacteria to the fluctuating conditions encountered as they pass through the host's intestinal epithelium and suggests novel strategies for the development of antimicrobial therapies.

Glucose starvation boosts Entamoeba histolytica virulence.

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Ayala Tovy

2011-08-01

Full Text Available The unicellular parasite, Entamoeba histolytica, is exposed to numerous adverse conditions, such as nutrient deprivation, during its life cycle stages in the human host. In the present study, we examined whether the parasite virulence could be influenced by glucose starvation (GS. The migratory behaviour of the parasite and its capability to kill mammalian cells and to lyse erythrocytes is strongly enhanced following GS. In order to gain insights into the mechanism underlying the GS boosting effects on virulence, we analyzed differences in protein expression levels in control and glucose-starved trophozoites, by quantitative proteomic analysis. We observed that upstream regulatory element 3-binding protein (URE3-BP, a transcription factor that modulates E.histolytica virulence, and the lysine-rich protein 1 (KRiP1 which is induced during liver abscess development, are upregulated by GS. We also analyzed E. histolytica membrane fractions and noticed that the Gal/GalNAc lectin light subunit LgL1 is up-regulated by GS. Surprisingly, amoebapore A (Ap-A and cysteine proteinase A5 (CP-A5, two important E. histolytica virulence factors, were strongly down-regulated by GS. While the boosting effect of GS on E. histolytica virulence was conserved in strains silenced for Ap-A and CP-A5, it was lost in LgL1 and in KRiP1 down-regulated strains. These data emphasize the unexpected role of GS in the modulation of E.histolytica virulence and the involvement of KRiP1 and Lgl1 in this phenomenon.

Ophthalmoplegic and lower cranial nerve variants merge into each other and into classical Guillain-Barre syndrome

NARCIS (Netherlands)

ter Bruggen, JP; van der Meche, FGA; de Jager, AEJ; Polman, CH

We delineated the place of cranial nerve variants within the concept of clinically defined Guillain-Barre syndrome (GBS), In the ophthalmoplegic variant (n = 7) the oculomotor nerves were early involved, In a lower cranial nerve variant (n = 9) the cranial nerves IX, X, and XI were early involved.

Anaerobiosis induced virulence of Salmonella typhi

DEFF Research Database (Denmark)

Kapoor, Sarika; Singh, R D; Sharma, P C

2002-01-01

, we examined the effect of anaerobiosis on the virulence of Salmonella Typhi, a Gram negative bacteria which invades through the gut mucosa and is responsible for typhoid fever. METHODS: Salmonella Typhi (ty2) was cultured in aerobic and anaerobic conditions to compare its virulence by rabbit ileal...

Virulence Types of Magnaporthe oryzae to Hybrid Rice in Sichuan, China

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Yu-lian BAI

2012-12-01

Full Text Available A total of 638 isolates of rice blast (Magnaporthe oryzae were isolated in 2002–2009 from different rice varieties in different regions of Sichuan, China and inoculated onto seven rice varieties (Lijiangxintuanheigu, IR24, Minghui 63, Duohui 1, Chenghui 448, Neihui 99-14 and RHR-1 to differentiate the virulence types of the fungus and trace the changes. The virulence to the seven varieties was respectively scored at 1, 2, 4, 8, 16, 32 and 64. The total scores of individual M. grisea isolates which were the sum of scores infecting differential varieties could, in turn, be used for the nomenclature of the virulence types due to their accordance to the special virulence patterns. The 638 tested isolates were then differentiated into 56 different virulence types. Type 15 virulent to Lijiangxintuanheigu, IR24 and Minghui 63, and Type 127 virulent to all of the seven varieties were the most dominant virulence types respectively with the occurrence frequencies of 15.99% and 15.83%. Type 19 and other seven virulence types were not monitored during 2002–2009. Type 15 was the predominant virulence type in 2002, 2003, 2004 and 2007, whereas Type 127 had been the most dominant virulence type after 2005 except for the year 2007 when the province underwent severe drought. Five hundred and seven out of the 638 tested isolates were virulent to Minghui 63, and 89.58% of the 384 isolates virulent to either Duohui 1, Chenghui 448 or Neihui 99-14 were virulent to Minghui 63, which indicated the impact of the extensive plantation of hybrid rice Minghui 63 as the restorer line on the virulence evolution of M. oryzae in Sichuan. The virulence pattern of the dominant virulence types suggested that the acquiring of virulence to all the major resistant restorer lines was the main routes of the evolution in virulence of M. oryzae to hybrid rice in Sichuan. The virulence frequencies of the 638 tested isolates to IR24, Minghui 63, Duohui 1, Chenghui 448, Neihui 99

Two Isoforms of Yersinia pestis Plasminogen Activator Pla: Intraspecies Distribution, Intrinsic Disorder Propensity, and Contribution to Virulence.

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Dentovskaya, Svetlana V; Platonov, Mikhail E; Svetoch, Tat'yana E; Kopylov, Pavel Kh; Kombarova, Tat'yana I; Ivanov, Sergey A; Shaikhutdinova, Rima Z; Kolombet, Lyubov' V; Chauhan, Sadhana; Ablamunits, Vitaly G; Motin, Vladimir L; Uversky, Vladimir N; Anisimov, Andrey P

2016-01-01

It has been shown previously that several endemic Y. pestis isolates with limited virulence contained the I259 isoform of the outer membrane protease Pla, while the epidemic highly virulent strains possessed only the T259 Pla isoform. Our sequence analysis of the pla gene from 118 Y. pestis subsp. microtus strains revealed that the I259 isoform was present exclusively in the endemic strains providing a convictive evidence of more ancestral origin of this isoform. Analysis of the effects of the I259T polymorphism on the intrinsic disorder propensity of Pla revealed that the I259T mutation slightly increases the intrinsic disorder propensity of the C-terminal tail of Pla and makes this protein slightly more prone for disorder-based protein-protein interactions, suggesting that the T259 Pla could be functionally more active than the I259 Pla. This assumption was proven experimentally by assessing the coagulase and fibrinolytic activities of the two Pla isoforms in human plasma, as well as in a direct fluorometric assay with the Pla peptide substrate. The virulence testing of Pla-negative or expressing the I259 and T259 Pla isoforms Y. pestis subsp. microtus and subsp. pestis strains did not reveal any significant difference in LD50 values and dose-dependent survival assays between them by using a subcutaneous route of challenge of mice and guinea pigs or intradermal challenge of mice. However, a significant decrease in time-to-death was observed in animals infected with the epidemic T259 Pla-producing strains as compared to the parent Pla-negative variants. Survival curves of the endemic I259 Pla+ strains fit between them, but significant difference in mean time to death post infection between the Pla-strains and their I259 Pla+ variants could be seen only in the isogenic set of subsp. pestis strains. These findings suggest an essential role for the outer membrane protease Pla evolution in Y. pestis bubonic infection exacerbation that is necessary for intensification

Within-host competition does not select for virulence in malaria parasites; studies with Plasmodium yoelii.

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Hussein M Abkallo

2015-02-01

Full Text Available In endemic areas with high transmission intensities, malaria infections are very often composed of multiple genetically distinct strains of malaria parasites. It has been hypothesised that this leads to intra-host competition, in which parasite strains compete for resources such as space and nutrients. This competition may have repercussions for the host, the parasite, and the vector in terms of disease severity, vector fitness, and parasite transmission potential and fitness. It has also been argued that within-host competition could lead to selection for more virulent parasites. Here we use the rodent malaria parasite Plasmodium yoelii to assess the consequences of mixed strain infections on disease severity and parasite fitness. Three isogenic strains with dramatically different growth rates (and hence virulence were maintained in mice in single infections or in mixed strain infections with a genetically distinct strain. We compared the virulence (defined as harm to the mammalian host of mixed strain infections with that of single infections, and assessed whether competition impacted on parasite fitness, assessed by transmission potential. We found that mixed infections were associated with a higher degree of disease severity and a prolonged infection time. In the mixed infections, the strain with the slower growth rate was often responsible for the competitive exclusion of the faster growing strain, presumably through host immune-mediated mechanisms. Importantly, and in contrast to previous work conducted with Plasmodium chabaudi, we found no correlation between parasite virulence and transmission potential to mosquitoes, suggesting that within-host competition would not drive the evolution of parasite virulence in P. yoelii.

Cystic fibrosis-niche adaptation of Pseudomonas aeruginosa reduces virulence in multiple infection hosts.

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Nicola Ivan Lorè

Full Text Available The opportunistic pathogen Pseudomonas aeruginosa is able to thrive in diverse ecological niches and to cause serious human infection. P. aeruginosa environmental strains are producing various virulence factors that are required for establishing acute infections in several host organisms; however, the P. aeruginosa phenotypic variants favour long-term persistence in the cystic fibrosis (CF airways. Whether P. aeruginosa strains, which have adapted to the CF-niche, have lost their competitive fitness in the other environment remains to be investigated. In this paper, three P. aeruginosa clonal lineages, including early strains isolated at the onset of infection, and late strains, isolated after several years of chronic lung infection from patients with CF, were analysed in multi-host model systems of acute infection. P. aeruginosa early isolates caused lethality in the three non-mammalian hosts, namely Caenorhabditis elegans, Galleria mellonella, and Drosophila melanogaster, while late adapted clonal isolates were attenuated in acute virulence. When two different mouse genetic background strains, namely C57Bl/6NCrl and Balb/cAnNCrl, were used as acute infection models, early P. aeruginosa CF isolates were lethal, while late isolates exhibited reduced or abolished acute virulence. Severe histopathological lesions, including high leukocytes recruitment and bacterial load, were detected in the lungs of mice infected with P. aeruginosa CF early isolates, while late isolates were progressively cleared. In addition, systemic bacterial spread and invasion of epithelial cells, which were detected for P. aeruginosa CF early strains, were not observed with late strains. Our findings indicate that niche-specific selection in P. aeruginosa reduced its ability to cause acute infections across a broad range of hosts while maintaining the capacity for chronic infection in the CF host.

The expression and evolution of virulence in multiple infections: the role of specificity, relative virulence and relative dose.

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Ben-Ami, Frida; Routtu, Jarkko

2013-05-03

Multiple infections of the same host by different strains of the same microparasite species are believed to play a crucial role during the evolution of parasite virulence. We investigated the role of specificity, relative virulence and relative dose in determining the competitive outcome of multiple infections in the Daphnia magna-Pasteuria ramosa host-parasite system. We found that infections by P. ramosa clones (single genotype) were less virulent and produced more spores than infections by P. ramosa isolates (possibly containing multiple genotypes). We also found that two similarly virulent isolates of P. ramosa differed considerably in their within-host competitiveness and their effects on host offspring production when faced with coinfecting P. ramosa isolates and clones. Although the relative virulence of a P. ramosa isolate/clone appears to be a good indicator of its competitiveness during multiple infections, the relative dose may alter the competitive outcome. Moreover, spore counts on day 20 post-infection indicate that the competitive outcome is largely decided early in the parasite's growth phase, possibly mediated by direct interference or apparent competition. Our results emphasize the importance of epidemiology as well as of various parasite traits in determining the outcome of within-host competition. Incorporating realistic epidemiological and ecological conditions when testing theoretical models of multiple infections, as well as using a wider range of host and parasite genotypes, will enable us to better understand the course of virulence evolution.

Salmonella-secreted Virulence Factors

Energy Technology Data Exchange (ETDEWEB)

Heffron, Fred; Niemann, George; Yoon, Hyunjin; Kidwai, Afshan S.; Brown, Roslyn N.; McDermott, Jason E.; Smith, Richard D.; Adkins, Joshua N.

2011-05-01

In this short review we discuss secreted virulence factors of Salmonella, which directly affect Salmonella interaction with its host. Salmonella secretes protein to subvert host defenses but also, as discussed, to reduce virulence thereby permitting the bacteria to persist longer and more successfully disperse. The type III secretion system (TTSS) is the best known and well studied of the mechanisms that enable secretion from the bacterial cytoplasm to the host cell cytoplasm. Other secretion systems include outer membrane vesicles, which are present in all Gram-negative bacteria examined to date, two-partner secretion, and type VI secretion will also be addressed. Excellent reviews of Salmonella secreted effectors have focused on themes such as actin rearrangements, vesicular trafficking, ubiquitination, and the activities of the virulence factors themselves. This short review is based on S. Typhimurium infection of mice because it is a model of typhoid like disease in humans. We have organized effectors in terms of events that happen during the infection cycle and how secreted effectors may be involved.

Toxin-independent virulence of Bacillus anthracis in rabbits.

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Haim Levy

Full Text Available The accepted paradigm states that anthrax is both an invasive and toxinogenic disease and that the toxins play a major role in pathogenicity. In the guinea pig (GP model we have previously shown that deletion of all three toxin components results in a relatively moderate attenuation in virulence, indicating that B. anthracis possesses an additional toxin-independent virulence mechanism. To characterize this toxin-independent mechanism in anthrax disease, we developed a new rabbit model by intravenous injection (IV of B. anthracis encapsulated vegetative cells, artificially creating bacteremia. Using this model we were able to demonstrate that also in rabbits, B. anthracis mutants lacking the toxins are capable of killing the host within 24 hours. This virulent trait depends on the activity of AtxA in the presence of pXO2, as, in the absence of the toxin genes, deletion of either component abolishes virulence. Furthermore, this IV virulence depends mainly on AtxA rather than the whole pXO1. A similar pattern was shown in the GP model using subcutaneous (SC administration of spores of the mutant strains, demonstrating the generality of the phenomenon. The virulent strains showed higher bacteremia levels and more efficient tissue dissemination; however our interpretation is that tissue dissemination per se is not the main determinant of virulence whose exact nature requires further elucidation.

Biofilm formation in a hydrodynamic environment by novel FimH variants and ramifications for virulence

DEFF Research Database (Denmark)

Schembri, Mark; Klemm, Per

2001-01-01

to mannose inhibition and represent novel phenotypes not previously identified in naturally occurring isolates. Characterization of our enriched clones revealed some similarities to amino acid alterations that occur in urinary tract infection (UTI) strains. Subsequent screening of a selection of UTI Fim...... in adherence and invasion, we have now demonstrated its function in biofilm formation on abiotic surfaces subjected to HDF conditions. The study indicates that UTI FimH variants possess adaptations that enhance biofilm formation and suggests a novel role for FimH in UTIs associated with medical implants...

Virulence Factors of Streptococcus mutans.

Science.gov (United States)

1986-08-01

763512/715242 Final Report U VIRULENCE FACTORS OF STREPTOCOCCUS MUTANS U Samuel Rosen Department of Oral Biology For the Period April 1, 1983 - June 30...00 FINAL REPORT VIRULENCE FACTORS OF STREPTOCOCCUS MUTANS Sam Rosen, Irving Shklair, E. X. Beck and F. M. Beck Ohio State University Columbus,Oh and...206-212. Johnson CP, Gorss S, Hillman JD (1978). Cariogenic properties of LDH deficient mutants of streptococcus mutans . J Dent Res 57, Special Issue

Diverse Genetic Regulon of the Virulence-Associated Transcriptional Regulator MucR in Brucella abortus 2308

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Caswell, Clayton C.; Elhassanny, Ahmed E. M.; Planchin, Emilie E.; Roux, Christelle M.; Weeks-Gorospe, Jenni N.; Ficht, Thomas A.; Dunman, Paul M.

2013-01-01

The Ros-type regulator MucR is one of the few transcriptional regulators that have been linked to virulence in Brucella. Here, we show that a Brucella abortus in-frame mucR deletion strain exhibits a pronounced growth defect during in vitro cultivation and, more importantly, that the mucR mutant is attenuated in cultured macrophages and in mice. The genetic basis for the attenuation of Brucella mucR mutants has not been defined previously, but in the present study the genes regulated by MucR in B. abortus have been elucidated using microarray analysis and real-time reverse transcription-PCR (RT-PCR). In B. abortus 2308, MucR regulates a wide variety of genes whose products may function in establishing and maintaining cell envelope integrity, polysaccharide biosynthesis, iron homeostasis, genome plasticity, and transcriptional regulation. Particularly notable among the MucR-regulated genes identified is arsR6 (nolR), which encodes a transcriptional regulator previously linked to virulence in Brucella melitensis 16 M. Importantly, electrophoretic mobility shift assays (EMSAs) determined that a recombinant MucR protein binds directly to the promoter regions of several genes repressed by MucR (including arsR6 [nolR]), and in Brucella, as in other alphaproteobacteria, MucR binds to its own promoter to repress expression of the gene that encodes it. Overall, these studies have uncovered the diverse genetic regulon of MucR in Brucella, and in doing so this work has begun to define the MucR-controlled genetic circuitry whose misregulation contributes to the virulence defect of Brucella mucR mutants. PMID:23319565

Limiting opportunities for cheating stabilizes virulence in insect parasitic nematodes.

Science.gov (United States)

Shapiro-Ilan, David; Raymond, Ben

2016-03-01

Cooperative secretion of virulence factors by pathogens can lead to social conflict when cheating mutants exploit collective secretion, but do not contribute to it. If cheats outcompete cooperators within hosts, this can cause loss of virulence. Insect parasitic nematodes are important biocontrol tools that secrete a range of significant virulence factors. Critically, effective nematodes are hard to maintain without live passage, which can lead to virulence attenuation. Using experimental evolution, we tested whether social cheating might explain unstable virulence in the nematode Heterorhabditis floridensis by manipulating relatedness via multiplicity of infection (MOI), and the scale of competition. Passage at high MOI, which should reduce relatedness, led to loss of fitness: virulence and reproductive rate declined together and all eight independent lines suffered premature extinction. As theory predicts, relatedness treatments had more impact under stronger global competition. In contrast, low MOI passage led to more stable virulence and increased reproduction. Moreover, low MOI lineages showed a trade-off between virulence and reproduction, particularly for lines under stronger between-host competition. Overall, this study indicates that evolution of virulence theory is valuable for the culture of biocontrol agents: effective nematodes can be improved and maintained if passage methods mitigate possible social conflicts.

Production Of Some Virulence Factors Under Different Growth ...

African Journals Online (AJOL)

Production Of Some Virulence Factors Under Different Growth Conditions And Antibiotic Susceptibility Pattern Of ... Animal Research International ... Keywords: Virulence, Haemolytic activity, Susceptibility, Antibiotics, Aeromonas hydrophila

Molecular determinants of Ebola virus virulence in mice.

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Hideki Ebihara

2006-07-01

Full Text Available Zaire ebolavirus (ZEBOV causes severe hemorrhagic fever in humans and nonhuman primates, with fatality rates in humans of up to 90%. The molecular basis for the extreme virulence of ZEBOV remains elusive. While adult mice resist ZEBOV infection, the Mayinga strain of the virus has been adapted to cause lethal infection in these animals. To understand the pathogenesis underlying the extreme virulence of Ebola virus (EBOV, here we identified the mutations responsible for the acquisition of the high virulence of the adapted Mayinga strain in mice, by using reverse genetics. We found that mutations in viral protein 24 and in the nucleoprotein were primarily responsible for the acquisition of high virulence. Moreover, the role of these proteins in virulence correlated with their ability to evade type I interferon-stimulated antiviral responses. These findings suggest a critical role for overcoming the interferon-induced antiviral state in the pathogenicity of EBOV and offer new insights into the pathogenesis of EBOV infection.

Recombinant Gallid herpesvirus 2 with interrupted meq genes confers safe and efficacious protection against virulent field strains.

Science.gov (United States)

Zhang, Yanping; Liu, Changjun; Yan, Fuhai; Liu, Ailing; Cheng, Yun; Li, Zhijie; Sun, Guorong; Lv, Hongchao; Wang, Xiaomei

2017-08-24

Gallid herpesvirus 2 (GaHV-2) continuously evolves, which reduces the effectiveness of existing vaccines. To construct new GaHV-2 candidate vaccines, LMS, which is a virulent GaHV-2 field strain isolated from diseased chicken flocks in Southwest China in 2007, was modified such that both copies of its meq oncogene were partially deleted. The resulting virus, i.e., rMSΔmeq, was characterized using PCR and sequencing. To evaluate the safety and protective efficacy of rMSΔmeq, specific pathogen-free (SPF) chickens were inoculated with 2000 plaque forming units (pfu) and 20,000pfu of rMSΔmeq immediately after hatching. All birds grew well during the experimental period, and none of the challenged chickens developed Marek's disease-associated lymphoma. In addition, the rMSΔmeq- and CVI988/Rispens-vaccinated SPF chickens were challenged with 1000 pfu and 5000 pfu of the representative virulent GaHV-2 Md5 strain and 1000 pfu of the variant GaHV-2 strains LCC or LTS. The results showed that the rMSΔmeq strain provided complete protection, which was similar to that provided by the CVI988/Rispens vaccine (protective index (PI) of 95.5) when challenged with a conventional dose of the Md5 strain. However, rMSΔmeq provided a PI of 90.9 when challenged with 5000 pfu of the Md5 strain, which was significantly higher than that provided by the CVI988/Rispens vaccine (54.5). rMSΔmeq provided a PI of 86.4 against LCC, which was equal to that provided by the CVI988/Rispens vaccine (81.8). In addition, rMSΔmeq provided a PI of 100 against LTS, which was significantly higher than that provided by the CVI988/Rispens vaccine (68.2). Altogether, the rMSΔmeq virus provided efficient protection against representative and variant GaHV-2 strains. In conclusion, the rMSΔmeq virus is a safe and effective vaccine candidate for the prevention of Marek's disease and is effective against the Chinese variant GaHV-2 strains. Copyright © 2017. Published by Elsevier Ltd.

The metabolic regulator CodY links L. monocytogenes metabolism to virulence by directly activating the virulence regulatory gene, prfA

Science.gov (United States)

Lobel, Lior; Sigal, Nadejda; Borovok, Ilya; Belitsky, Boris R.; Sonenshein, Abraham L.; Herskovits, Anat A.

2015-01-01

Summary Metabolic adaptations are critical to the ability of bacterial pathogens to grow within host cells and are normally preceded by sensing of host-specific metabolic signals, which in turn can influence the pathogen's virulence state. Previously, we reported that the intracellular bacterial pathogen Listeria monocytogenes responds to low availability of branched-chain amino acids (BCAA) within mammalian cells by up-regulating both BCAA biosynthesis and virulence genes. The induction of virulence genes required the BCAA-responsive transcription regulator, CodY, but the molecular mechanism governing this mode of regulation was unclear. In this report, we demonstrate that CodY directly binds the coding sequence of the L. monocytogenes master virulence activator gene, prfA, 15 nt downstream of its start codon, and that this binding results in up-regulation of prfA transcription specifically under low concentrations of BCAA. Mutating this site abolished CodY binding and reduced prfA transcription in macrophages, and attenuated bacterial virulence in mice. Notably, the mutated binding site did not alter prfA transcription or PrfA activity under other conditions that are known to activate PrfA, such as during growth in the presence of glucose-1-phosphate. This study highlights the tight crosstalk between L. monocytogenes metabolism and virulence' while revealing novel features of CodY-mediated regulation. PMID:25430920

Computational Approach to Annotating Variants of Unknown Significance in Clinical Next Generation Sequencing.

Science.gov (United States)

Schulz, Wade L; Tormey, Christopher A; Torres, Richard

2015-01-01

Next generation sequencing (NGS) has become a common technology in the clinical laboratory, particularly for the analysis of malignant neoplasms. However, most mutations identified by NGS are variants of unknown clinical significance (VOUS). Although the approach to define these variants differs by institution, software algorithms that predict variant effect on protein function may be used. However, these algorithms commonly generate conflicting results, potentially adding uncertainty to interpretation. In this review, we examine several computational tools used to predict whether a variant has clinical significance. In addition to describing the role of these tools in clinical diagnostics, we assess their efficacy in analyzing known pathogenic and benign variants in hematologic malignancies. Copyright© by the American Society for Clinical Pathology (ASCP).

Virulence Factors IN Fungi OF Systemic Mycoses

Directory of Open Access Journals (Sweden)

KUROKAWA Cilmery Suemi

1998-01-01

Full Text Available Pathogenic fungi that cause systemic mycoses retain several factors which allow their growth in adverse conditions provided by the host, leading to the establishment of the parasitic relationship and contributing to disease development. These factors are known as virulence factors which favor the infection process and the pathogenesis of the mycoses. The present study evaluates the virulence factors of pathogenic fungi such as Blastomyces dermatitidis, Coccidioides immitis, Cryptococcus neoformans, Histoplasma capsulatum and Paracoccidioides brasiliensis in terms of thermotolerance, dimorphism, capsule or cell wall components as well as enzyme production. Virulence factors favor fungal adhesion, colonization, dissemination and the ability to survive in hostile environments and elude the immune response mechanisms of the host. Both the virulence factors presented by different fungi and the defense mechanisms provided by the host require action and interaction of complex processes whose knowledge allows a better understanding of the pathogenesis of systemic mycoses.

Mutations within ICP4 acquired during in vitro attenuation do not alter virulence of recombinant Marek's disease viruses in vivo

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Evin Hildebrandt

2015-12-01

Full Text Available Marek's disease (MD is a T-cell lymphoma of chickens caused by the oncogenic Marek's disease virus (MDV. MD is primarily controlled by live-attenuated vaccines generated by repeated in vitro serial passage. Previous efforts to characterize attenuated MDVs identified numerous mutations, particularly a convergence of high-frequency mutations around amino acids 60–63 within ICP4 (RS1, therefore, ICP4 was considered a candidate gene deserving further characterization. Recombinant MDVs were generated containing a single Q63H mutation or double Q63H + S1630P mutations. Despite the repetitive nature of mutations within ICP4, neither recombinant virus decreased virulence, although one mutant reduced in vivo replication and failed to transmit horizontally. Our results indicate that these mutations are insufficient to reduce disease incidence in infected birds, and suggest that variants in ICP4 do not directly alter virulence, but rather may enhance MDV replication rates in vitro, offering an explanation for the widespread occurrence of ICP4 mutations in a variety of attenuated herpesviruses.

Plasma membrane lipids and their role in fungal virulence.

Science.gov (United States)

Rella, Antonella; Farnoud, Amir M; Del Poeta, Maurizio

2016-01-01

There has been considerable evidence in recent years suggesting that plasma membrane lipids are important regulators of fungal pathogenicity. Various glycolipids have been shown to impart virulent properties in several fungal species, while others have been shown to play a role in host defense. In addition to their role as virulence factors, lipids also contribute to other virulence mechanisms such as drug resistance, biofilm formation, and release of extracellular vesicles. In addition, lipids also affect the mechanical properties of the plasma membrane through the formation of packed microdomains composed mainly of sphingolipids and sterols. Changes in the composition of lipid microdomains have been shown to disrupt the localization of virulence factors and affect fungal pathogenicity. This review gathers evidence on the various roles of plasma membrane lipids in fungal virulence and how lipids might contribute to the different processes that occur during infection and treatment. Insight into the role of lipids in fungal virulence can lead to an improved understanding of the process of fungal pathogenesis and the development of new lipid-mediated therapeutic strategies. Published by Elsevier Ltd.

Virulence patterns in a murine sepsis model of ST131 Escherichia coli clinical isolates belonging to serotypes O25b:H4 and O16:H5 are associated to specific virotypes.

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Azucena Mora

Full Text Available Escherichia coli sequence type (ST131 is an emerging disseminated public health threat implicated in multidrug-resistant extraintestinal infections worldwide. Although the majority of ST131 isolates belong to O25b:H4 serotype, new variants with different serotypes, STs using the discriminative multilocus sequence typing scheme of Pasteur Institute, and virulence-gene profiles (virotypes have been reported with unknown implications on the pattern of spread, persistence and virulence. The aim of the present study was to compare virulence in a mouse subcutaneous sepsis model of representative ST131 clinical isolates belonging to 2 serotypes (O25b:H4, O16:H5 and nine virotypes and subtypes (A, B, C, D1, D2, D3, D4, D5 and E. Fourteen out of the 23 ST131 isolates tested (61% killed 90 to 100% of mice challenged, and 18 of 23 (78% at least 50%. Interestingly, different virulence patterns in association with virotypes were observed, from highly rapid lethality (death in less than 24 h to low final lethality (death at 7 days but with presence of an acute inflammation. This is the first study to assess virulence of ST131 isolates belonging to serotype O16:H5, which exhibited virotype C. In spite of their low virulence-gene score, O16:H5 isolates did not show significant differences in final lethality compared with highly virulent O25b:H4 isolates of virotypes A, B and C, but killed mice less rapidly. Significant differences were found, however, between virotypes A, B, C (final lethality ≥80% of mice challenged and virotypes D, E. Particularly unexpected was the low lethality of the newly assigned virotype E taking into account that it exhibited high virulence-gene score, and the same clonotype H30 as highly virulent O25b:H4 isolates of virotypes A, B and C. In vivo virulence diversity reported in this study would reflect the genetic variability within ST131 clonal group evidenced by molecular typing.

Virulence-associated gene profiling of Streptococcus suis isolates by PCR

NARCIS (Netherlands)

Silva, L.M.G.; Baums, C.G.; Rehm, T.; Wisselink, H.J.; Goethe, R.; Valentin-Weigand, P.

2006-01-01

Definition of virulent Streptococcus suis strains is controversial. One successful approach for identification of virulent European strains is differentiation of capsular serotypes (or the corresponding cps types) and subsequent detection of virulence-associated factors, namely the extracellular

[Virulent gene prevalence of foodborne Listeria monocytogenes in China in 2005].

Science.gov (United States)

Yang, Yang; Fu, Ping; Guo, Yun-Chang; Pei, Xiao-Yan; Liu, Xiu-Mei

2010-12-01

To study the virulent gene prevalence of foodborne Listeria monocytogenes (LM) isolated from China. 78 LM isolates derived from raw meat, cooked food, aquatic products and vegetables of 13 provinces and cities.LM isolates were investigated for prevalence of virulence genes (LIPI-1 (prfA, plcA, hly, mpl, actA, plcB); LIPI-2 (inlA, inlB), and iap) by PCR method. 87.2% (68/78) of the isolates were prfA positive, 98.7% (77/78) of the isolates were plcA, actA and plcB positive, 97.4% (76/78) of the isolates were hly positive, 87.2% (68/78) of the isolates were mpl positive, 92.3% (72/78) of the isolates were inlA positive, 100% (78/78) of the isolates were inlB positive, 98.7% (77/78) of the isolates were iap positive. Among 21 virulent gene negative isolates, there was 7 isolates lack of two or more virulence genes. The rate of virulence genes deletion isolates from cooked meat was 31.3% (10/32), the rate of virulence genes deletion isolates from raw meat was 16.1% (5/31), the rate of virulence genes deletion isolates from vegetables was 36.4% (4/11) and rate of virulence genes deletion isolates from seafood was 50% (2/4). No significant difference was found (χ(2) = 3.721, P > 0.05). The virulence gene array-1 strains were dominant among these isolates. Among 78 LM isolates, prevalent of virulent genes were different except inlB, virulence genes of LIP-1 were deleted prevalently among isolates, virulence gene deletion patterns were diverse.

Efflux inhibitor suppresses Streptococcus mutans virulence properties.

Science.gov (United States)

Zeng, Huihui; Liu, Jia; Ling, Junqi

2017-04-01

It is well established that efflux pumps play important roles in bacterial pathogenicity and efflux inhibitors (EIs) have been proved to be effective in suppressing bacterial virulence properties. However, little is known regarding the EI of Streptococcus mutans, a well-known caries-inducing bacterium. In this study, we identified the EI of S. mutans through ethidium bromide efflux assay and investigated how EI affected S. mutans virulence regarding the cariogenicity and stress response. Results indicated that reserpine, the identified EI, suppressed acid tolerance, mutacin production and transformation efficiency of S. mutans, and modified biofilm architecture and extracellular polysaccharide distribution. Suppressed glycosyltransferase activity was also noted after reserpine exposure. The data from quantitative real-time-PCR demonstrated that reserpine significantly altered the expression profile of quorum-sensing and virulence-associated genes. These findings suggest that reserpine represents a promising adjunct anticariogenic agent in that it suppresses virulence properties of S. mutans. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

[Virulence and its relationship to antibiotic resistance].

Science.gov (United States)

Joly-Guillou, M L

1998-12-01

PATHOGENIC ISLANDS: Certain DNA blocks inserted into the chromosome of most Gram negative bacteria originated in pathogens found in plants. VIRULENCE-ANTIBIOTIC INTERACTIONS: During the invasive phase, the bacterial cell covers itself with adhesins which facilitate its adherence to tissues. The bacterial cell produces a fibronectin which protects its defense systems. Antibiotics favor bacterial resistance by increasing the expression of surface adhesins and fibronectin production. PENICILLIN RESISTANT PNEUMOCOCCI: Experimental models have demonstrated that mortality in mice and host resistance to pneumococcal infection are related to the type of capsule and not to antibiotic resistance. QUORUM SENSING: The bacterial inoculum regulates the production of virulence factors in vivo via quorum sensing. This regulation can play an important role in Pseudomonas aeruginosa infections. ACINETOBACTER BAUMANNI VIRULENCE: Long poorly understood, factors favoring A. baumanni virulence appear to result from bacterial production of IROMPs in the extracellular growth medium in response to iron depletion during the exponential growth phase.

Virulence, serotype and phylogenetic groups of diarrhoeagenic ...

African Journals Online (AJOL)

Dr DADIE Thomas

2014-02-17

Feb 17, 2014 ... The virulence, serotype and phylogenetic traits of diarrhoeagenic Escherichia coli were detected in 502 strains isolated during digestive infections. Molecular detection of the target virulence genes, rfb gene of operon O and phylogenetic grouping genes Chua, yjaA and TSPE4.C2 was performed.

Molecular typing and virulence analysis of serotype K1 Klebsiella pneumoniae strains isolated from liver abscess patients and stool samples from noninfectious subjects in Hong Kong, Singapore, and Taiwan.

Science.gov (United States)

Siu, L Kristopher; Fung, Chang-Phone; Chang, Feng-Yee; Lee, Nelson; Yeh, Kuo-Ming; Koh, Tse Hsien; Ip, Margaret

2011-11-01

Serotype K1 Klebsiella pneumoniae with multilocus sequence type 23 (ST23) has been strongly associated with liver abscess in Taiwan. Few data regarding the strain types and virulence of this serotype from other Asian countries are available. Serotype K1 K. pneumoniae strains isolated from liver abscess and stool samples from subjects hospitalized in Hong Kong, Singapore, and Taiwan hospitals were examined. Forty-seven serotype K1 isolates were identified: 26 from liver abscess samples and 21 from stool samples. MLST revealed 7 sequence types: 85.1% (40 of 47 isolates) belonged to ST23, 1 isolate belonged to ST163 (a single-locus variant of ST23), and 2 isolates were ST249 (a 3-locus variant of ST23). New STs, namely, ST367, ST425, and ST426, were allocated to 3 of 4 isolates from stool samples. The virulence of these strains was determined by neutrophil phagocytosis and mouse infection models. Except for two ST23 isolates, all Klebsiella pneumoniae isolates were resistant to phagocytosis. Resistance to serum killing varied in isolates of ST23, while all non-ST23 strains were susceptible to serum killing except one with ST249 from a liver abscess. All hypervirulent isolates with a 50% lethal dose of serum killing, and also carried both virulence-associated genes, rmpA and aerobactin. Multilocus sequence typing genotype 23 was the most prevalent sequence type among serotype K1 K. pneumoniae isolates from both liver abscess and stool samples in the Asia Pacific region. Serotype K1 K. pneumoniae isolates with capsule expression leading to phagocytic resistance and with the aerobactin gene were associated with hypervirulence.

Virulence evolution at the front line of spreading epidemics.

Science.gov (United States)

Griette, Quentin; Raoul, Gaël; Gandon, Sylvain

2015-11-01

Understanding and predicting the spatial spread of emerging pathogens is a major challenge for the public health management of infectious diseases. Theoretical epidemiology shows that the speed of an epidemic is governed by the life-history characteristics of the pathogen and its ability to disperse. Rapid evolution of these traits during the invasion may thus affect the speed of epidemics. Here we study the influence of virulence evolution on the spatial spread of an epidemic. At the edge of the invasion front, we show that more virulent and transmissible genotypes are expected to win the competition with other pathogens. Behind the front line, however, more prudent exploitation strategies outcompete virulent pathogens. Crucially, even when the presence of the virulent mutant is limited to the edge of the front, the invasion speed can be dramatically altered by pathogen evolution. We support our analysis with individual-based simulations and we discuss the additional effects of demographic stochasticity taking place at the front line on virulence evolution. We confirm that an increase of virulence can occur at the front, but only if the carrying capacity of the invading pathogen is large enough. These results are discussed in the light of recent empirical studies examining virulence evolution at the edge of spreading epidemics. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

Effect of Negative Pressure on Proliferation, Virulence Factor Secretion, Biofilm Formation, and Virulence-Regulated Gene Expression of Pseudomonas aeruginosa In Vitro

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Guo-Qi Wang

2016-01-01

Full Text Available Objective. To investigate the effect of negative pressure conditions induced by NPWT on P. aeruginosa. Methods. P. aeruginosa was cultured in a Luria–Bertani medium at negative pressure of −125 mmHg for 24 h in the experimental group and at atmospheric pressure in the control group. The diameters of the colonies of P. aeruginosa were measured after 24 h. ELISA kit, orcinol method, and elastin-Congo red assay were used to quantify the virulence factors. Biofilm formation was observed by staining with Alexa Fluor® 647 conjugate of concanavalin A (Con A. Virulence-regulated genes were determined by quantitative RT-PCR. Results. As compared with the control group, growth of P. aeruginosa was inhibited by negative pressure. The colony size under negative pressure was significantly smaller in the experimental group than that in the controls (p<0.01. Besides, reductions in the total amount of virulence factors were observed in the negative pressure group, including exotoxin A, rhamnolipid, and elastase. RT-PCR results revealed a significant inhibition in the expression level of virulence-regulated genes. Conclusion. Negative pressure could significantly inhibit the growth of P. aeruginosa. It led to a decrease in the virulence factor secretion, biofilm formation, and a reduction in the expression level of virulence-regulated genes.

Virulence Factors Associated with Enterococcus Faecalis Infective Endocarditis

DEFF Research Database (Denmark)

Madsen, Kristian T; Skov, Marianne N; Gill, Sabine

2017-01-01

INTRODUCTION: The enterococci are accountable for up to 20% of all cases of infective endocarditis, with Enterococcus faecalis being the primary causative isolate. Infective endocarditis is a life-threatening infection of the endocardium that results in the formation of vegetations. Based...... on a literature review, this paper provides an overview of the virulence factors associated with E. faecalis infective endocarditis. Furthermore, it reports the effects of active or passive immunization against some of these involved factors. INDIVIDUAL VIRULENCE FACTORS: Nine virulence factors have in particular...... been associated with E. faecalis infective endocarditis. Absence of these factors entailed attenuation of strains in both mixed- and mono-bacterial infection endocarditis models as well as in in vitro and ex vivo assays when compared to their virulence factor expressing parental strains. PATHOGENESIS...

RNAi-Based Functional Genomics Identifies New Virulence Determinants in Mucormycosis.

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Trung Anh Trieu

2017-01-01

Full Text Available Mucorales are an emerging group of human pathogens that are responsible for the lethal disease mucormycosis. Unfortunately, functional studies on the genetic factors behind the virulence of these organisms are hampered by their limited genetic tractability, since they are reluctant to classical genetic tools like transposable elements or gene mapping. Here, we describe an RNAi-based functional genomic platform that allows the identification of new virulence factors through a forward genetic approach firstly described in Mucorales. This platform contains a whole-genome collection of Mucor circinelloides silenced transformants that presented a broad assortment of phenotypes related to the main physiological processes in fungi, including virulence, hyphae morphology, mycelial and yeast growth, carotenogenesis and asexual sporulation. Selection of transformants with reduced virulence allowed the identification of mcplD, which encodes a Phospholipase D, and mcmyo5, encoding a probably essential cargo transporter of the Myosin V family, as required for a fully virulent phenotype of M. circinelloides. Knock-out mutants for those genes showed reduced virulence in both Galleria mellonella and Mus musculus models, probably due to a delayed germination and polarized growth within macrophages. This study provides a robust approach to study virulence in Mucorales and as a proof of concept identified new virulence determinants in M. circinelloides that could represent promising targets for future antifungal therapies.

Development of a High Resolution Virulence Allelic Profiling (HReVAP) Approach Based on the Accessory Genome of Escherichia coli to Characterize Shiga-Toxin Producing E. coli (STEC)

Science.gov (United States)

Michelacci, Valeria; Orsini, Massimiliano; Knijn, Arnold; Delannoy, Sabine; Fach, Patrick; Caprioli, Alfredo; Morabito, Stefano

2016-01-01

Shiga-toxin producing Escherichia coli (STEC) strains possess a large accessory genome composed of virulence genes existing in multiple allelic variants, which sometimes segregate with specific STEC subpopulations. We analyzed the allelic variability of 91 virulence genes of STEC by Real Time PCR followed by melting curves analysis in 713 E. coli strains including 358 STEC. The 91 genes investigated were located on the locus of enterocyte effacement (LEE), OI-57, and OI-122 pathogenicity islands and displayed a total of 476 alleles in the study population. The combinations of the 91 alleles of each strain were termed allelic signatures and used to perform cluster analyses. We termed such an approach High Resolution Virulence Allelic Profiling (HReVAP) and used it to investigate the phylogeny of STEC of multiple serogroups. The dendrograms obtained identified groups of STEC segregating approximately with the serogroups and allowed the identification of subpopulations within the single groups. The study of the allelic signatures provided further evidence of the coevolution of the LEE and OI-122, reflecting the occurrence of their acquisition through a single event. The HReVAP analysis represents a sensitive tool for studying the evolution of LEE-positive STEC. PMID:26941726

pyAmpli: an amplicon-based variant filter pipeline for targeted resequencing data.

Science.gov (United States)

Beyens, Matthias; Boeckx, Nele; Van Camp, Guy; Op de Beeck, Ken; Vandeweyer, Geert

2017-12-14

Haloplex targeted resequencing is a popular method to analyze both germline and somatic variants in gene panels. However, involved wet-lab procedures may introduce false positives that need to be considered in subsequent data-analysis. No variant filtering rationale addressing amplicon enrichment related systematic errors, in the form of an all-in-one package, exists to our knowledge. We present pyAmpli, a platform independent parallelized Python package that implements an amplicon-based germline and somatic variant filtering strategy for Haloplex data. pyAmpli can filter variants for systematic errors by user pre-defined criteria. We show that pyAmpli significantly increases specificity, without reducing sensitivity, essential for reporting true positive clinical relevant mutations in gene panel data. pyAmpli is an easy-to-use software tool which increases the true positive variant call rate in targeted resequencing data. It specifically reduces errors related to PCR-based enrichment of targeted regions.

Relevance of Peptide Uptake Systems to the Physiology and Virulence of Streptococcus agalactiae

OpenAIRE

Samen, Ulrike; Gottschalk, Birgit; Eikmanns, Bernhard J.; Reinscheid, Dieter J.

2004-01-01

Streptococcus agalactiae is a major cause of invasive infections in human newborns. To satisfy its growth requirements, S. agalactiae takes up 9 of the 20 proteinogenic amino acids from the environment. Defined S. agalactiae mutants in one or several of four putative peptide permease systems were constructed and tested for peptide uptake, growth in various media, and expression of virulence traits. Oligopeptide uptake by S. agalactiae was shown to be mediated by the ABC transporter OppA1-F, w...

Cytopathogenic effects in enterocytelike Caco-2 cells differentiate virulent from avirulent Listeria strains.

OpenAIRE

Pine, L; Kathariou, S; Quinn, F; George, V; Wenger, J D; Weaver, R E

1991-01-01

We have developed a simple test that differentiates between virulent and avirulent Listeria species as defined by the mouse 50% lethal doses (LD50S). The assay is based on trypan blue-revealed cytopathogenic effects that are produced during the infection of the human enterocytelike cell line Caco-2. These effects were elicited only by Listeria strains that had an intraperitoneal mouse LD50 less than 10(8) and were not produced by nonhemolytic, avirulent strains of Listeria monocytogenes gener...

Non-avian animal reservoirs present a source of influenza A PB1-F2 proteins with novel virulence-enhancing markers.

Science.gov (United States)

Alymova, Irina V; York, Ian A; McCullers, Jonathan A

2014-01-01

PB1-F2 protein, expressed from an alternative reading frame of most influenza A virus (IAV) PB1 segments, may possess specific residues associated with enhanced inflammation (L62, R75, R79, and L82) and cytotoxicity (I68, L69, and V70). These residues were shown to increase the pathogenicity of primary viral and secondary bacterial infections in a mouse model. In contrast to human seasonal influenza strains, virulence-associated residues are present in PB1-F2 proteins from pandemic H1N1 1918, H2N2 1957, and H3N2 1968, and highly pathogenic H5N1 strains, suggesting their contribution to viruses' pathogenic phenotypes. Non-human influenza strains may act as donors of virulent PB1-F2 proteins. Previously, avian influenza strains were identified as a potential source of inflammatory, but not cytotoxic, PB1-F2 residues. Here, we analyze the frequency of virulence-associated residues in PB1-F2 sequences from IAVs circulating in mammalian species in close contact with humans: pigs, horses, and dogs. All four inflammatory residues were found in PB1-F2 proteins from these viruses. Among cytotoxic residues, I68 was the most common and was especially prevalent in equine and canine IAVs. Historically, PB1-F2 from equine (about 75%) and canine (about 20%) IAVs were most likely to have combinations of the highest numbers of residues associated with inflammation and cytotoxicity, compared to about 7% of swine IAVs. Our analyses show that, in addition to birds, pigs, horses, and dogs are potentially important sources of pathogenic PB1-F2 variants. There is a need for surveillance of IAVs with genetic markers of virulence that may be emerging from these reservoirs in order to improve pandemic preparedness and response.

Mutations induced by ultraviolet radiation affecting virulence in Puccinia striiformis

International Nuclear Information System (INIS)

Shang Hongsheng; Jing Jinxue; Li Zhenqi

1994-01-01

Uredospores of parent culture, cy 29-1, were treated by ultraviolet radiation and mutations to virulent were tested on resistant wheat cultivars inoculated with treated spores. 7 mutant cultures virulent to the test cultivars were developed with estimated mutation rate 10~6~10~4. The virulence of mutant cultures was different from the all known races of stripe rust. Resistance segregation to mutant cultures was detected in two test cultivars. The results suggested that mutation was important mechanism of virulence variation operative in asexual population of rust fungi

Multi-virulence-locus sequence typing of Staphylococcus lugdunensis generates results consistent with a clonal population structure and is reliable for epidemiological typing.

Science.gov (United States)

Didi, Jennifer; Lemée, Ludovic; Gibert, Laure; Pons, Jean-Louis; Pestel-Caron, Martine

2014-10-01

Staphylococcus lugdunensis is an emergent virulent coagulase-negative staphylococcus responsible for severe infections similar to those caused by Staphylococcus aureus. To understand its potentially pathogenic capacity and have further detailed knowledge of the molecular traits of this organism, 93 isolates from various geographic origins were analyzed by multi-virulence-locus sequence typing (MVLST), targeting seven known or putative virulence-associated loci (atlLR2, atlLR3, hlb, isdJ, SLUG_09050, SLUG_16930, and vwbl). The polymorphisms of the putative virulence-associated loci were moderate and comparable to those of the housekeeping genes analyzed by multilocus sequence typing (MLST). However, the MVLST scheme generated 43 virulence types (VTs) compared to 20 sequence types (STs) based on MLST, indicating that MVLST was significantly more discriminating (Simpson's index [D], 0.943). No hypervirulent lineage or cluster specific to carriage strains was defined. The results of multilocus sequence analysis of known and putative virulence-associated loci are consistent with a clonal population structure for S. lugdunensis, suggesting a coevolution of these genes with housekeeping genes. Indeed, the nonsynonymous to synonymous evolutionary substitutions (dN/dS) ratio, the Tajima's D test, and Single-likelihood ancestor counting (SLAC) analysis suggest that all virulence-associated loci were under negative selection, even atlLR2 (AtlL protein) and SLUG_16930 (FbpA homologue), for which the dN/dS ratios were higher. In addition, this analysis of virulence-associated loci allowed us to propose a trilocus sequence typing scheme based on the intragenic regions of atlLR3, isdJ, and SLUG_16930, which is more discriminant than MLST for studying short-term epidemiology and further characterizing the lineages of the rare but highly pathogenic S. lugdunensis. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Accurate genotyping across variant classes and lengths using variant graphs

DEFF Research Database (Denmark)

Sibbesen, Jonas Andreas; Maretty, Lasse; Jensen, Jacob Malte

2018-01-01

of read k-mers to a graph representation of the reference and variants to efficiently perform unbiased, probabilistic genotyping across the variation spectrum. We demonstrate that BayesTyper generally provides superior variant sensitivity and genotyping accuracy relative to existing methods when used...... collecting a set of candidate variants across discovery methods, individuals and databases, and then realigning the reads to the variants and reference simultaneously. However, this realignment problem has proved computationally difficult. Here, we present a new method (BayesTyper) that uses exact alignment...... to integrate variants across discovery approaches and individuals. Finally, we demonstrate that including a ‘variation-prior’ database containing already known variants significantly improves sensitivity....

Impact of High-Level Daptomycin Resistance in the Streptococcus mitis Group on Virulence and Survivability during Daptomycin Treatment in Experimental Infective Endocarditis

Science.gov (United States)

Garcia-de-la-Maria, C.; Xiong, Y. Q.; Pericas, J. M.; Armero, Y.; Moreno, A.; Mishra, N. N.; Rybak, M. J.; Tran, T. T.; Arias, C. A.; Sullam, P. M.; Bayer, A. S.

2017-01-01

ABSTRACT Among the viridans group streptococci, the Streptococcus mitis group is the most common cause of infective endocarditis. These bacteria have a propensity to be β-lactam resistant, as well as to rapidly develop high-level and durable resistance to daptomycin (DAP). We compared a parental, daptomycin-susceptible (DAPs) S. mitis/S. oralis strain and its daptomycin-resistant (DAPr) variant in a model of experimental endocarditis in terms of (i) their relative fitness in multiple target organs in this model (vegetations, kidneys, spleen) when animals were challenged individually and in a coinfection strategy and (ii) their survivability during therapy with daptomycin-gentamicin (an in vitro combination synergistic against the parental strain). The DAPr variant was initially isolated from the cardiac vegetations of animals with experimental endocarditis caused by the parental DAPs strain following treatment with daptomycin. The parental strain and the DAPr variant were comparably virulent when animals were individually challenged. In contrast, in the coinfection model without daptomycin therapy, at both the 106- and 107-CFU/ml challenge inocula, the parental strain outcompeted the DAPr variant in all target organs, especially the kidneys and spleen. When the animals in the coinfection model of endocarditis were treated with DAP-gentamicin, the DAPs strain was completely eliminated, while the DAPr variant persisted in all target tissues. These data underscore that the acquisition of DAPr in S. mitis/S. oralis does come at an intrinsic fitness cost, although this resistance phenotype is completely protective against therapy with a potentially synergistic DAP regimen. PMID:28264848

Virulence of Rhodococcus equi Isolated from Cats and Dogs

OpenAIRE

Takai, Shinji; Martens, Ronald J.; Julian, Alan; Garcia Ribeiro, Márcio; Rodrigues de Farias, Marconi; Sasaki, Yukako; Inuzuka, Kazuho; Kakuda, Tsutomu; Tsubaki, Shiro; Prescott, John F.

2003-01-01

Nine cat isolates and nine dog isolates of Rhodococcus equi from clinical material were investigated for the presence of the virulence-associated antigens (VapA and VapB) and virulence plasmids. Five of the cat isolates and one dog isolate were VapA positive and contained an 85-kb type I or an 87-kb type I plasmid. The remaining 12 isolates were avirulent R. equi strains and contained no virulence plasmids.

Pathogenesis comparison between the United States porcine epidemic diarrhoea virus prototype and S-INDEL-variant strains in conventional neonatal piglets.

Science.gov (United States)

Chen, Qi; Gauger, Phillip C; Stafne, Molly R; Thomas, Joseph T; Madson, Darin M; Huang, Haiyan; Zheng, Ying; Li, Ganwu; Zhang, Jianqiang

2016-05-01

At least two genetically different porcine epidemic diarrhoea virus (PEDV) strains have been identified in the USA: US PEDV prototype and S-INDEL-variant strains. The objective of this study was to compare the pathogenicity differences of the US PEDV prototype and S-INDEL-variant strains in conventional neonatal piglets under experimental infections. Fifty PEDV-negative 5-day-old pigs were divided into five groups of ten pigs each and were inoculated orogastrically with three US PEDV prototype isolates (IN19338/2013, NC35140/2013 and NC49469/2013), an S-INDEL-variant isolate (IL20697/2014), and virus-negative culture medium, respectively, with virus titres of 104 TCID50 ml- 1, 10 ml per pig. All three PEDV prototype isolates tested in this study, regardless of their phylogenetic clades, had similar pathogenicity and caused severe enteric disease in 5-day-old pigs as evidenced by clinical signs, faecal virus shedding, and gross and histopathological lesions. Compared with pigs inoculated with the three US PEDV prototype isolates, pigs inoculated with the S-INDEL-variant isolate had significantly diminished clinical signs, virus shedding in faeces, gross lesions in small intestines, caeca and colons, histopathological lesions in small intestines, and immunohistochemistry staining in ileum. However, the US PEDV prototype and the S-INDEL-variant strains induced similar viraemia levels in inoculated pigs. Whole genome sequences of the PEDV prototype and S-INDEL-variant strains were determined, but the molecular basis of virulence differences between these PEDV strains remains to be elucidated using a reverse genetics approach.

Annotating DNA variants is the next major goal for human genetics.

Science.gov (United States)

Cutting, Garry R

2014-01-02

Clinical genetic testing has undergone a dramatic transformation in the past two decades. Diagnostic laboratories that previously tested for well-established disease-causing DNA variants in a handful of genes have evolved into sequencing factories identifying thousands of variants of known and unknown medical consequence. Sorting out what does and does not cause disease in our genomes is the next great challenge in making genetics a central feature of healthcare. I propose that closing the gap in our ability to interpret variation responsible for Mendelian disorders provides a grand and unprecedented opportunity for geneticists. Human geneticists are well placed to coordinate a systematic evaluation of variants in collaboration with basic scientists and clinicians. Sharing of knowledge, data, methods, and tools will aid both researchers and healthcare workers in achieving their common goal of defining the pathogenic potential of variants. Generation of variant annotations will inform genetic testing and will deepen our understanding of gene and protein function, thereby aiding the search for molecular targeted therapies. Copyright © 2014 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

Potential drivers of virulence evolution in aquaculture

Science.gov (United States)

Kennedy, David A.; Kurath, Gael; Brito, Ilana L.; Purcell, Maureen K.; Read, Andrew F.; Winton, James R.; Wargo, Andrew R.

2016-01-01

Infectious diseases are economically detrimental to aquaculture, and with continued expansion and intensification of aquaculture, the importance of managing infectious diseases will likely increase in the future. Here, we use evolution of virulence theory, along with examples, to identify aquaculture practices that might lead to the evolution of increased pathogen virulence. We identify eight practices common in aquaculture that theory predicts may favor evolution toward higher pathogen virulence. Four are related to intensive aquaculture operations, and four others are related specifically to infectious disease control. Our intention is to make aquaculture managers aware of these risks, such that with increased vigilance, they might be able to detect and prevent the emergence and spread of increasingly troublesome pathogen strains in the future.

A theoretical model of the evolution of virulence in sexually transmitted HIV/AIDS Modelo teórico da evolucão da virulência do HIV/AIDS transmitido sexualmente

Directory of Open Access Journals (Sweden)

FAB Coutinho

1999-08-01

Full Text Available INTRODUCTION: The evolution of virulence in host-parasite relationships has been the subject of several publications. In the case of HIV virulence, some authors suggest that the evolution of HIV virulence correlates with the rate of acquisition of new sexual partners. In contrast some other authors argue that the level of HIV virulence is independent of the sexual activity of the host population. METHODS: Provide a mathematical model for the study of the potential influence of human sexual behaviour on the evolution of virulence of HIV is provided. RESULTS: The results indicated that, when the probability of acquisition of infection is a function both of the sexual activity and of the virulence level of HIV strains, the evolution of HIV virulence correlates positively with the rate of acquisition of new sexual partners. CONCLUSION: It is concluded that in the case of a host population with a low (high rate of exchange of sexual partners the evolution of HIV virulence is such that the less (more virulent strain prevails.INTRODUÇÃO: A evolução da virulência na relação hospedeiro-parasita tem sido objeto de várias publicações. No caso do HIV, alguns autores sugerem que a evolução da virulência do HIV correlaciona-se com a taxa de aquisição de novos parceiros sexuais. Por outro lado, outros autores argumentam que o nível de virulência do HIV é independente da atividade sexual da população hospedeira. MÉTODOS: Propõe-se um modelo matemático para estudar a influência potencial que o comportamento sexual humano possa ter na evolução da virulência do HIV. RESULTADOS: Os resultados indicam que, quando a probabilidade de aquisição da infecção pelo HIV é uma função tanto da atividade sexual da população humana quanto da virulência das cepas de HIV, a evolução da virulência do HIV correlaciona-se positivamente com a taxa de aquisição de novos parceiros sexuais. CONCLUSÃO: Concluiu-se que no caso de uma popula

Genome sequence of the endosymbiont Rickettsia peacockii and comparison with virulent Rickettsia rickettsii: identification of virulence factors.

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Roderick F Felsheim

2009-12-01

Full Text Available Rickettsia peacockii, also known as the East Side Agent, is a non-pathogenic obligate intracellular bacterium found as an endosymbiont in Dermacentor andersoni ticks in the western USA and Canada. Its presence in ticks is correlated with reduced prevalence of Rickettsia rickettsii, the agent of Rocky Mountain Spotted Fever. It has been proposed that a virulent SFG rickettsia underwent changes to become the East Side Agent. We determined the genome sequence of R. peacockii and provide a comparison to a closely related virulent R. rickettsii. The presence of 42 chromosomal copies of the ISRpe1 transposon in the genome of R. peacockii is associated with a lack of synteny with the genome of R. rickettsii and numerous deletions via recombination between transposon copies. The plasmid contains a number of genes from distantly related organisms, such as part of the glycosylation island of Pseudomonas aeruginosa. Genes deleted or mutated in R. peacockii which may relate to loss of virulence include those coding for an ankyrin repeat containing protein, DsbA, RickA, protease II, OmpA, ScaI, and a putative phosphoethanolamine transferase. The gene coding for the ankyrin repeat containing protein is especially implicated as it is mutated in R. rickettsii strain Iowa, which has attenuated virulence. Presence of numerous copies of the ISRpe1 transposon, likely acquired by lateral transfer from a Cardinium species, are associated with extensive genomic reorganization and deletions. The deletion and mutation of genes possibly involved in loss of virulence have been identified by this genomic comparison. It also illustrates that the introduction of a transposon into the genome can have varied effects; either correlating with an increase in pathogenicity as in Francisella tularensis or a loss of pathogenicity as in R. peacockii and the recombination enabled by multiple transposon copies can cause significant deletions in some genomes while not in others.

A Standardized DNA Variant Scoring System for Pathogenicity Assessments in Mendelian Disorders.

Science.gov (United States)

Karbassi, Izabela; Maston, Glenn A; Love, Angela; DiVincenzo, Christina; Braastad, Corey D; Elzinga, Christopher D; Bright, Alison R; Previte, Domenic; Zhang, Ke; Rowland, Charles M; McCarthy, Michele; Lapierre, Jennifer L; Dubois, Felicita; Medeiros, Katelyn A; Batish, Sat Dev; Jones, Jeffrey; Liaquat, Khalida; Hoffman, Carol A; Jaremko, Malgorzata; Wang, Zhenyuan; Sun, Weimin; Buller-Burckle, Arlene; Strom, Charles M; Keiles, Steven B; Higgins, Joseph J

2016-01-01

We developed a rules-based scoring system to classify DNA variants into five categories including pathogenic, likely pathogenic, variant of uncertain significance (VUS), likely benign, and benign. Over 16,500 pathogenicity assessments on 11,894 variants from 338 genes were analyzed for pathogenicity based on prediction tools, population frequency, co-occurrence, segregation, and functional studies collected from internal and external sources. Scores were calculated by trained scientists using a quantitative framework that assigned differential weighting to these five types of data. We performed descriptive and comparative statistics on the dataset and tested interobserver concordance among the trained scientists. Private variants defined as variants found within single families (n = 5,182), were either VUS (80.5%; n = 4,169) or likely pathogenic (19.5%; n = 1,013). The remaining variants (n = 6,712) were VUS (38.4%; n = 2,577) or likely benign/benign (34.7%; n = 2,327) or likely pathogenic/pathogenic (26.9%, n = 1,808). Exact agreement between the trained scientists on the final variant score was 98.5% [95% confidence interval (CI) (98.0, 98.9)] with an interobserver consistency of 97% [95% CI (91.5, 99.4)]. Variant scores were stable and showed increasing odds of being in agreement with new data when re-evaluated periodically. This carefully curated, standardized variant pathogenicity scoring system provides reliable pathogenicity scores for DNA variants encountered in a clinical laboratory setting. © 2015 The Authors. **Human Mutation published by Wiley Periodicals, Inc.

Empirical support for optimal virulence in a castrating parasite.

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Knut Helge Jensen

2006-07-01

Full Text Available The trade-off hypothesis for the evolution of virulence predicts that parasite transmission stage production and host exploitation are balanced such that lifetime transmission success (LTS is maximised. However, the experimental evidence for this prediction is weak, mainly because LTS, which indicates parasite fitness, has been difficult to measure. For castrating parasites, this simple model has been modified to take into account that parasites convert host reproductive resources into transmission stages. Parasites that kill the host too early will hardly benefit from these resources, while postponing the killing of the host results in diminished returns. As predicted from optimality models, a parasite inducing castration should therefore castrate early, but show intermediate levels of virulence, where virulence is measured as time to host killing. We studied virulence in an experimental system where a bacterial parasite castrates its host and produces spores that are not released until after host death. This permits estimating the LTS of the parasite, which can then be related to its virulence. We exposed replicate individual Daphnia magna (Crustacea of one host clone to the same amount of bacterial spores and followed individuals until their death. We found that the parasite shows strong variation in the time to kill its host and that transmission stage production peaks at an intermediate level of virulence. A further experiment tested for the genetic basis of variation in virulence by comparing survival curves of daphniids infected with parasite spores obtained from early killing versus late killing infections. Hosts infected with early killer spores had a significantly higher death rate as compared to those infected with late killers, indicating that variation in time to death was at least in part caused by genetic differences among parasites. We speculate that the clear peak in lifetime reproductive success at intermediate killing times

The Botrytis cinerea xylanase Xyn11A contributes to virulence with its necrotizing activity, not with its catalytic activity

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González Celedonio

2010-02-01

Full Text Available Abstract Background The Botrytis cinerea xylanase Xyn11A has been previously shown to be required for full virulence of this organism despite its poor contribution to the secreted xylanase activity and the low xylan content of B. cinerea hosts. Intriguingly, xylanases from other fungi have been shown to have the property, independent of the xylan degrading activity, to induce necrosis when applied to plant tissues, so we decided to test the hypothesis that secreted Xyn11A contributes to virulence by promoting the necrosis of the plant tissue surrounding the infection, therefore facilitating the growth of this necrotroph. Results We show here that Xyn11A has necrotizing activity on plants and that this capacity is conserved in site-directed mutants of the protein lacking the catalytic activity. Besides, Xyn11A contributes to the infection process with the necrotizing and not with the xylan hydrolyzing activity, as the catalytically-impaired Xyn11A variants were able to complement the lower virulence of the xyn11A mutant. The necrotizing activity was mapped to a 30-amino acids peptide in the protein surface, and this region was also shown to mediate binding to tobacco spheroplasts by itself. Conclusions The main contribution of the xylanase Xyn11A to the infection process of B. cinerea is to induce necrosis of the infected plant tissue. A conserved 30-amino acids region on the enzyme surface, away from the xylanase active site, is responsible for this effect and mediates binding to plant cells.

Streptococcus agalactiae vaginitis: nonhemolytic variant on the Liofilchem® Chromatic StreptoB.

Science.gov (United States)

Savini, Vincenzo; Marrollo, Roberta; D'Antonio, Marianna; D'Amario, Claudio; Fazii, Paolo; D'Antonio, Domenico

2013-01-01

Streptococcus agalactiae (group B Streptococcus, GBS) vaginal pathogenicity is not uniformly acknowledged throughout the literature; accordingly, in women, genital itching and burning, along with leukorrhea are commonly and almost exclusively referred to bacterial vaginosis, candidiasis and trichomoniasis. Conversely, GBS virulence for vagina was recognized in the past, as the organism has been observed to potentially cause local inflammation and discharge, as well as lactobacilli rarefaction. We depict here a case where a nonhemolytic (γ-hemolytic) GBS strain was found to be the etiologic agent of vaginal infection. Such uncommon S. agalactiae phenotypes are hard to be recognized and may be therefore responsible for misdiagnosing and underestimation of GBS vaginitis prevalence; here, we had the support of the Liofilchem(®) Chromatic StreptoB medium, that successfully detected such an atypical variant.

Effects of contact structure on the transient evolution of HIV virulence.

Directory of Open Access Journals (Sweden)

Sang Woo Park

2017-03-01

Full Text Available Early in an epidemic, high densities of susceptible hosts select for relatively high parasite virulence; later in the epidemic, lower susceptible densities select for lower virulence. Thus over the course of a typical epidemic the average virulence of parasite strains increases initially, peaks partway through the epidemic, then declines again. However, precise quantitative outcomes, such as the peak virulence reached and its timing, may depend sensitively on epidemiological details. Fraser et al. proposed a model for the eco-evolutionary dynamics of HIV that incorporates the tradeoffs between transmission and virulence (mediated by set-point viral load, SPVL and their heritability between hosts. Their model used implicit equations to capture the effects of partnership dynamics that are at the core of epidemics of sexually transmitted diseases. Our models combine HIV virulence tradeoffs with a range of contact models, explicitly modeling partnership formation and dissolution and allowing for individuals to transmit disease outside of partnerships. We assess summary statistics such as the peak virulence (corresponding to the maximum value of population mean log10 SPVL achieved throughout the epidemic across models for a range of parameters applicable to the HIV epidemic in sub-Saharan Africa. Although virulence trajectories are broadly similar across models, the timing and magnitude of the virulence peak vary considerably. Previously developed implicit models predicted lower virulence and slower progression at the peak (a maximum of 3.5 log10 SPVL compared both to more realistic models and to simple random-mixing models with no partnership structure at all (both with a maximum of ≈ 4.7 log10 SPVL. In this range of models, the simplest random-mixing structure best approximates the most realistic model; this surprising outcome occurs because the dominance of extra-pair contact in the realistic model swamps the effects of partnership structure.

Cellulase variants

Science.gov (United States)

Blazej, Robert; Toriello, Nicholas; Emrich, Charles; Cohen, Richard N.; Koppel, Nitzan

2015-07-14

This invention provides novel variant cellulolytic enzymes having improved activity and/or stability. In certain embodiments the variant cellulotyic enzymes comprise a glycoside hydrolase with or comprising a substitution at one or more positions corresponding to one or more of residues F64, A226, and/or E246 in Thermobifida fusca Cel9A enzyme. In certain embodiments the glycoside hydrolase is a variant of a family 9 glycoside hydrolase. In certain embodiments the glycoside hydrolase is a variant of a theme B family 9 glycoside hydrolase.

Screening for spontaneous virulent mutants of barley powdery mildew (Erysiphe graminis DC)

International Nuclear Information System (INIS)

Torp, J.; Jensen, H.P.

1989-01-01

Full text: Seedlings of 4 barley lines possessing resistance genes M1-a6, M1-a12 or M1-g were inoculated with powdery mildew culture CR3, which is a-virulent to the 4 host lines. In total, 50 million conidia were screened for the occurrence of virulent mutants, 43 putative virulent mutants were found. They could be grouped into 5 genotypes according to the virulence spectrum. They might have originated by one of the following events: 1. admixture, 2. physiological events that allow a few conidia to establish colonies in spite of the presence of a functional gene for resistance, 3. mutation in a gene for specificity, 4. deletion or mutation in some kind of suppressing element in which case more than one virulence may be affected. Based upon the virulence spectra, mating type, biochemical tests and analysis of test crosses, 3 of the genotypes were clearly classified as not being of mutational origin. Of the two remaining genotypes one differed in 4 virulences, the other by two virulences and one avirulence. Based upon expectations from the gene-for-gene concept, it is concluded that both were not of mutational origin. If in fact there are derived from a mutation, the concept of gene-for-gene interactions would have to be revised. Assuming that no mutations for virulence were found in this experiment, the spontaneous mutation frequency from avirulence to virulence would be below 2x10 -8 . (author)

Investigating the ?Trojan Horse? Mechanism of Yersinia pestis Virulence

Energy Technology Data Exchange (ETDEWEB)

McCutchen-Maloney, S L; Fitch, J P

2005-02-08

Yersinia pestis, the etiological agent of plague, is a Gram-negative, highly communicable, enteric bacterium that has been responsible for three historic plague pandemics. Currently, several thousand cases of plague are reported worldwide annually, and Y. pestis remains a considerable threat from a biodefense perspective. Y. pestis infection can manifest in three forms: bubonic, septicemic, and pneumonic plague. Of these three forms, pneumonic plague has the highest fatality rate ({approx}100% if left untreated), the shortest intervention time ({approx}24 hours), and is highly contagious. Currently, there are no rapid, widely available vaccines for plague and though plague may be treated with antibiotics, the emergence of both naturally occurring and potentially engineered antibiotic resistant strains makes the search for more effective therapies and vaccines for plague of pressing concern. The virulence mechanism of this deadly bacterium involves induction of a Type III secretion system, a syringe-like apparatus that facilitates the injection of virulence factors, termed Yersinia outer membrane proteins (Yops), into the host cell. These virulence factors inhibit phagocytosis and cytokine secretion, and trigger apoptosis of the host cell. Y. pestis virulence factors and the Type III secretion system are induced thermally, when the bacterium enters the mammalian host from the flea vector, and through host cell contact (or conditions of low Ca{sup 2+} in vitro). Apart from the temperature increase from 26 C to 37 C and host cell contact (or low Ca{sup 2+} conditions), other molecular mechanisms that influence virulence induction in Y. pestis are largely uncharacterized. This project focused on characterizing two novel mechanisms that regulate virulence factor induction in Y. pestis, immunoglobulin G (IgG) binding and quorum sensing, using a real-time reporter system to monitor induction of virulence. Incorporating a better understanding of the mechanisms of virulence

Antibiotic Resistance and Virulence Properties in Escherichia coli ...

African Journals Online (AJOL)

This study determined E. coli resistance to commonly used antibiotics together with their virulence properties in Ile-Ife, Nigeria. A total of 137 E. coli isolates from cases of urinary tract infection were tested for their sensitivity to commonly used antibiotics and possession of virulence factors using standard methods.

Virulence Gene Pool Detected in Bovine Group C Streptococcus dysgalactiae subsp. dysgalactiae Isolates by Use of a Group A S. pyogenes Virulence Microarray ▿

Science.gov (United States)

Rato, Márcia G.; Nerlich, Andreas; Bergmann, René; Bexiga, Ricardo; Nunes, Sandro F.; Vilela, Cristina L.; Santos-Sanches, Ilda; Chhatwal, Gursharan S.

2011-01-01

A custom-designed microarray containing 220 virulence genes of Streptococcus pyogenes (group A Streptococcus [GAS]) was used to test group C Streptococcus dysgalactiae subsp. dysgalactiae (GCS) field strains causing bovine mastitis and group C or group G Streptococcus dysgalactiae subsp. equisimilis (GCS/GGS) isolates from human infections, with the latter being used for comparative purposes, for the presence of virulence genes. All bovine and all human isolates carried a fraction of the 220 genes (23% and 39%, respectively). The virulence genes encoding streptolysin S, glyceraldehyde-3-phosphate dehydrogenase, the plasminogen-binding M-like protein PAM, and the collagen-like protein SclB were detected in the majority of both bovine and human isolates (94 to 100%). Virulence factors, usually carried by human beta-hemolytic streptococcal pathogens, such as streptokinase, laminin-binding protein, and the C5a peptidase precursor, were detected in all human isolates but not in bovine isolates. Additionally, GAS bacteriophage-associated virulence genes encoding superantigens, DNase, and/or streptodornase were detected in bovine isolates (72%) but not in the human isolates. Determinants located in non-bacteriophage-related mobile elements, such as the gene encoding R28, were detected in all bovine and human isolates. Several virulence genes, including genes of bacteriophage origin, were shown to be expressed by reverse transcriptase PCR (RT-PCR). Phylogenetic analysis of superantigen gene sequences revealed a high level (>98%) of identity among genes of bovine GCS, of the horse pathogen Streptococcus equi subsp. equi, and of the human pathogen GAS. Our findings indicate that alpha-hemolytic bovine GCS, an important mastitis pathogen and considered to be a nonhuman pathogen, carries important virulence factors responsible for virulence and pathogenesis in humans. PMID:21525223

The TOR signaling pathway regulates vegetative development and virulence in Fusarium graminearum.

Science.gov (United States)

Yu, Fangwei; Gu, Qin; Yun, Yingzi; Yin, Yanni; Xu, Jin-Rong; Shim, Won-Bo; Ma, Zhonghua

2014-07-01

The target of rapamycin (TOR) signaling pathway plays critical roles in controlling cell growth in a variety of eukaryotes. However, the contribution of this pathway in regulating virulence of plant pathogenic fungi is unknown. We identified and characterized nine genes encoding components of the TOR pathway in Fusarium graminearum. Biological, genetic and biochemical functions of each component were investigated. The FgFkbp12-rapamycin complex binds to the FgTor kinase. The type 2A phosphatases FgPp2A, FgSit4 and FgPpg1 were found to interact with FgTap42, a downstream component of FgTor. Among these, we determined that FgPp2A is likely to be essential for F. graminearum survival, and FgSit4 and FgPpg1 play important roles in cell wall integrity by positively regulating the phosphorylation of FgMgv1, a key MAP kinase in the cell wall integrity pathway. In addition, the FgPpg1 interacting protein, FgTip41, is involved in regulating mycelial growth and virulence. Notably, FgTip41 does not interact with FgTap42 but with FgPpg1, suggesting the existence of FgTap42:FgPpg1:FgTip41 heterotrimer in F. graminearum, a complex not observed in the yeast model. Collectively, we defined a genetic regulatory framework that elucidates how the TOR pathway regulates virulence and vegetative development in F. graminearum. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Single amino acid substitutions on the needle tip protein IpaD increased Shigella virulence.

Science.gov (United States)

Meghraoui, Alaeddine; Schiavolin, Lionel; Allaoui, Abdelmounaaïm

2014-07-01

Infection of colonic epithelial cells by Shigella is associated with the type III secretion system, which serves as a molecular syringe to inject effectors into host cells. This system includes an extracellular needle used as a conduit for secreted proteins. Two of these proteins, IpaB and IpaD, dock at the needle tip to control secretion and are also involved in the insertion of a translocation pore into host cell membrane allowing effector delivery. To better understand the function of IpaD, we substituted thirteen residues conserved among homologous proteins in other bacterial species. Generated variants were tested for their ability to surface expose IpaB and IpaD, to control secretion, to insert the translocation pore, and to invade host cells. In addition to a first group of seven ipaD variants that behaved similarly to the wild-type strain, we identified a second group with mutations V314D and I319D that deregulated secretion of all effectors, but remained fully invasive. Moreover, we identified a third group with mutations Y153A, T161D, Q165L and Y276A, that exhibited increased levels of translocators secretion, pore formation, and cell entry. Altogether, our results offer a better understanding of the role of IpaD in the control of Shigella virulence. Copyright © 2014 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Virulence potential of Staphylococcus aureus isolates from Buruli ulcer patients.

Science.gov (United States)

Amissah, Nana Ama; Chlebowicz, Monika A; Ablordey, Anthony; Tetteh, Caitlin S; Prah, Isaac; van der Werf, Tjip S; Friedrich, Alex W; van Dijl, Jan Maarten; Stienstra, Ymkje; Rossen, John W

2017-06-01

Buruli ulcer (BU) is a necrotizing infection of the skin and subcutaneous tissue caused by Mycobacterium ulcerans. BU wounds may also be colonized with other microorganisms including Staphylococcus aureus. This study aimed to characterize the virulence factors of S. aureus isolated from BU patients. Previously sequenced genomes of 21 S. aureus isolates from BU patients were screened for the presence of virulence genes. The results show that all S. aureus isolates harbored on their core genomes genes for known virulence factors like α-hemolysin, and the α- and β-phenol soluble modulins. Besides the core genome virulence genes, mobile genetic elements (MGEs), i.e. prophages, genomic islands, pathogenicity islands and a Staphylococcal cassette chromosome (SCC) were found to carry different combinations of virulence factors, among them genes that are known to encode factors that promote immune evasion, superantigens and Panton-Valentine Leucocidin. The present observations imply that the S. aureus isolates from BU patients harbor a diverse repertoire of virulence genes that may enhance bacterial survival and persistence in the wound environment and potentially contribute to delayed wound healing. Copyright © 2017 The Authors. Published by Elsevier GmbH.. All rights reserved.

A theoretical model of the evolution of virulence in sexually transmitted HIV/AIDS

Directory of Open Access Journals (Sweden)

FAB Coutinho

1999-08-01

Full Text Available INTRODUCTION: The evolution of virulence in host-parasite relationships has been the subject of several publications. In the case of HIV virulence, some authors suggest that the evolution of HIV virulence correlates with the rate of acquisition of new sexual partners. In contrast some other authors argue that the level of HIV virulence is independent of the sexual activity of the host population. METHODS: Provide a mathematical model for the study of the potential influence of human sexual behaviour on the evolution of virulence of HIV is provided. RESULTS: The results indicated that, when the probability of acquisition of infection is a function both of the sexual activity and of the virulence level of HIV strains, the evolution of HIV virulence correlates positively with the rate of acquisition of new sexual partners. CONCLUSION: It is concluded that in the case of a host population with a low (high rate of exchange of sexual partners the evolution of HIV virulence is such that the less (more virulent strain prevails.

A theoretical model of the evolution of virulence in sexually transmitted HIV/AIDS

Directory of Open Access Journals (Sweden)

Coutinho FAB

1999-01-01

Full Text Available INTRODUCTION: The evolution of virulence in host-parasite relationships has been the subject of several publications. In the case of HIV virulence, some authors suggest that the evolution of HIV virulence correlates with the rate of acquisition of new sexual partners. In contrast some other authors argue that the level of HIV virulence is independent of the sexual activity of the host population. METHODS: Provide a mathematical model for the study of the potential influence of human sexual behaviour on the evolution of virulence of HIV is provided. RESULTS: The results indicated that, when the probability of acquisition of infection is a function both of the sexual activity and of the virulence level of HIV strains, the evolution of HIV virulence correlates positively with the rate of acquisition of new sexual partners. CONCLUSION: It is concluded that in the case of a host population with a low (high rate of exchange of sexual partners the evolution of HIV virulence is such that the less (more virulent strain prevails.

Variations in glycoprotein B contribute to immunogenic difference between PRV variant JS-2012 and Bartha-K61.

Science.gov (United States)

Yu, Zhi-Qing; Tong, Wu; Zheng, Hao; Li, Li-Wei; Li, Guo-Xin; Gao, Fei; Wang, Tao; Liang, Chao; Ye, Chao; Wu, Ji-Qiang; Huang, Qinfeng; Tong, Guang-Zhi

2017-09-01

A newly emerged pseudorabies virus (PRV) variant has been identified in many Bartha-K61-vaccinated pig farms. This variant has caused great economic losses to the swine industry in China since 2011. Sequence analysis demonstrated that the gB gene of the emerging PRV variant JS-2012 had multiple variations compared with the vaccine strain Bartha-K61. In the study, a specific CRISPR/Cas9 system combined with homologous recombination was used to construct two recombinant viruses, BJB (Bartha-K61+JS-2012gB) and JBJ (JS-2012-ΔgE/gI+Bartha-K61gB), by interchanging the full-length gB genes between Bartha-K61 and JS-2012-ΔgE/gI. The two recombinant viruses showed similar characteristics in growth kinetics in vitro and similar pathogenicity in mice, as compared to their parental strains. Immunization of mice with inactivated BJB or JBJ followed by challenge of JS-2012 showed that BJB could increase protective efficacy to 80%, compared to only 40% protection by the parental Bartha-K61 strain. JBJ had a decreased protective efficacy of 65%, as compared to 90% protection by its parental JS-2012-ΔgE/gI strain. Exchange of the gB gene markedly altered the immunogenicity of the recombinant PRV. These data suggest that variations in gB might play an important role in the virulence of the reemergent PRV variant in China. Our results demonstrate the importance of gB in protective immunity and suggest that the recombinant virus BJB could be a promising vaccine candidate for eradication of the PRV variant. Copyright © 2017 Elsevier B.V. All rights reserved.

The Role of Constitutional Copy Number Variants in Breast Cancer

Science.gov (United States)

Walker, Logan C.; Wiggins, George A.R.; Pearson, John F.

2015-01-01

Constitutional copy number variants (CNVs) include inherited and de novo deviations from a diploid state at a defined genomic region. These variants contribute significantly to genetic variation and disease in humans, including breast cancer susceptibility. Identification of genetic risk factors for breast cancer in recent years has been dominated by the use of genome-wide technologies, such as single nucleotide polymorphism (SNP)-arrays, with a significant focus on single nucleotide variants. To date, these large datasets have been underutilised for generating genome-wide CNV profiles despite offering a massive resource for assessing the contribution of these structural variants to breast cancer risk. Technical challenges remain in determining the location and distribution of CNVs across the human genome due to the accuracy of computational prediction algorithms and resolution of the array data. Moreover, better methods are required for interpreting the functional effect of newly discovered CNVs. In this review, we explore current and future application of SNP array technology to assess rare and common CNVs in association with breast cancer risk in humans. PMID:27600231

[Analysis of virulence factors of Porphyromonas endodontalis based on comparative proteomics technique].

Science.gov (United States)

Li, H; Ji, H; Wu, S S; Hou, B X

2016-12-09

Objective: To analyze the protein expression profile and the potential virulence factors of Porphyromonas endodontalis (Pe) via comparison with that of two strains of Porphyromonas gingivalis (Pg) with high and low virulences, respectively. Methods: Whole cell comparative proteomics of Pe ATCC35406 was examined and compared with that of high virulent strain Pg W83 andlow virulent strain Pg ATCC33277, respectively. Isobaric tags for relative and absolute quantitation (iTRAQ) combined with nano liquid chromatography-tandem mass spectrometry (Nano-LC-MS/MS) were adopted to identify and quantitate the proteins of Pe and two strains of Pg with various virulences by using the methods of isotopically labeled peptides, mass spectrometric detection and bioinformatics analysis. The biological functions of similar proteins expressed by Pe ATCC35406 and two strains of Pg were quantified and analyzed. Results: Totally 1 210 proteins were identified while Pe compared with Pg W83. There were 130 proteins (10.74% of the total proteins) expressed similarly, including 89 known functional proteins and 41 proteins of unknown functions. Totally 1 223 proteins were identified when Pe compared with Pg ATCC33277. There were 110 proteins (8.99% of the total proteins) expressed similarly, including 72 known functional proteins and 38 proteins of unknown functions. The similarly expressed proteins in Pe and Pg strains with various virulences mainly focused on catalytic activity and binding function, including recombination activation gene (RagA), lipoprotein, chaperonin Dnak, Clp family proteins (ClpC and ClpX) and various iron-binding proteins. They were involved in metabolism and cellular processes. In addition, the type and number of similar virulence proteins between Pe and high virulence Pg were higher than those between Pe and low virulence Pg. Conclusions: Lipoprotein, oxygen resistance protein, iron binding protein were probably the potential virulence factors of Pe ATCC35406. It was

Aureusimines in Staphylococcus aureus are not involved in virulence.

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Sun, Fei; Cho, Hoonsik; Jeong, Do-Won; Li, Chunling; He, Chuan; Bae, Taeok

2010-12-29

Recently, dipeptide aureusimines were reported to activate expression of staphylococcal virulence genes, such as alpha-hemolysin, and increase S. aureus virulence. Surprisingly, most of the virulence genes affected by aureusimines form part of the regulon of the SaeRS two component system (TCS), raising the possibility that SaeRS might be directly or indirectly involved in the aureusimine-dependent signaling process. Using HPLC analyses, we confirmed that a transposon mutant of ausA, the gene encoding the aureusimine dipeptide synthesis enzyme, does not produce dipeptides. However, the transposon mutant showed normal hemolysis activity and alpha-hemolysin/SaeP production. Furthermore, the P1 promoter of the sae operon, one of the targets of the SaeRS TCS, showed normal transcription activity. Moreover, in contrast to the original report, the ausA transposon mutant did not exhibit attenuated virulence in an animal infection model. DNA sequencing revealed that the ausA deletion mutant used in the original study has an 83 nt-duplication in saeS. Hemolysis activity of the original mutant was restored by a plasmid carrying the sae operon. A mutant of the sae operon showed elevated resistance to chloramphenicol and erythromycin, two antibiotics widely used during staphylococcal mutagenesis. At 43°C in the presence of erythromycin and aeration, the conditions typically employed for staphylococcal mutagenesis, an saeR transposon mutant grew much faster than a control mutant and the saeR mutant was highly enriched in a mixed culture experiment. Our results show that the previously reported roles of aureusimines in staphylococcal gene regulation and virulence were due to an unintended mutation in saeS, which was likely selected due to elevated resistance of the mutant to environmental stresses. Thus, there is no evidence indicating that the dipeptide aureusimines play a role in sae-mediated virulence factor production or contribute to staphylococcal virulence.

Aureusimines in Staphylococcus aureus are not involved in virulence.

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Fei Sun

2010-12-01

Full Text Available Recently, dipeptide aureusimines were reported to activate expression of staphylococcal virulence genes, such as alpha-hemolysin, and increase S. aureus virulence. Surprisingly, most of the virulence genes affected by aureusimines form part of the regulon of the SaeRS two component system (TCS, raising the possibility that SaeRS might be directly or indirectly involved in the aureusimine-dependent signaling process.Using HPLC analyses, we confirmed that a transposon mutant of ausA, the gene encoding the aureusimine dipeptide synthesis enzyme, does not produce dipeptides. However, the transposon mutant showed normal hemolysis activity and alpha-hemolysin/SaeP production. Furthermore, the P1 promoter of the sae operon, one of the targets of the SaeRS TCS, showed normal transcription activity. Moreover, in contrast to the original report, the ausA transposon mutant did not exhibit attenuated virulence in an animal infection model. DNA sequencing revealed that the ausA deletion mutant used in the original study has an 83 nt-duplication in saeS. Hemolysis activity of the original mutant was restored by a plasmid carrying the sae operon. A mutant of the sae operon showed elevated resistance to chloramphenicol and erythromycin, two antibiotics widely used during staphylococcal mutagenesis. At 43°C in the presence of erythromycin and aeration, the conditions typically employed for staphylococcal mutagenesis, an saeR transposon mutant grew much faster than a control mutant and the saeR mutant was highly enriched in a mixed culture experiment.Our results show that the previously reported roles of aureusimines in staphylococcal gene regulation and virulence were due to an unintended mutation in saeS, which was likely selected due to elevated resistance of the mutant to environmental stresses. Thus, there is no evidence indicating that the dipeptide aureusimines play a role in sae-mediated virulence factor production or contribute to staphylococcal

OrfX, a Nucleomodulin Required for Listeria monocytogenes Virulence

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Andrzej Prokop

2017-10-01

Full Text Available Listeria monocytogenes is a bacterial pathogen causing severe foodborne infections in humans and animals. Listeria can enter into host cells and survive and multiply therein, due to an arsenal of virulence determinants encoded in different loci on the chromosome. Several key Listeria virulence genes are clustered in Listeria pathogenicity island 1. This important locus also contains orfX (lmo0206, a gene of unknown function. Here, we found that OrfX is a small, secreted protein whose expression is positively regulated by PrfA, the major transcriptional activator of Listeria virulence genes. We provide evidence that OrfX is a virulence factor that dampens the oxidative response of infected macrophages, which contributes to intracellular survival of bacteria. OrfX is targeted to the nucleus and interacts with the regulatory protein RybP. We show that in macrophages, the expression of OrfX decreases the level of RybP, which controls cellular infection. Collectively, these data reveal that Listeria targets RybP and evades macrophage oxidative stress for efficient infection. Altogether, OrfX is after LntA, the second virulence factor acting directly in the nucleus.

MR imaging of the ankle: Normal variants

International Nuclear Information System (INIS)

Noto, A.M.; Cheung, Y.; Rosenberg, Z.S.; Norman, A.; Leeds, N.E.

1987-01-01

Thirty asymptomatic ankles were studied with high-resolution surface coil MR imaging. The thirty ankles were reviewed for identification or normal structures. The MR appearance of the deltoid and posterior to talo-fibular ligaments, peroneous brevis and longus tendons, and posterior aspect of the tibial-talar joint demonstrated several normal variants not previously described. These should not be misinterpreted as pathologic processes. The specific findings included (1) cortical irregularity of the posterior tibial-talar joint in 27 of 30 cases which should not be mistaken for osteonecrois; (2) normal posterior talo-fibular ligament with irregular and frayed inhomogeneity, which represents a normal variant in seven of ten cases; and (3) fluid in the shared peroneal tendons sheath which may be confused for a longitudinal tendon tear in three of 30 cases. Ankle imaging with the use of MR is still a relatively new procedure. Further investigation is needed to better define normal anatomy as well as normal variants. The authors described several structures that normally present with variable MR imaging appearances. This is clinically significant in order to maintain a high sensitivity and specificity in MR imaging interpretation

Helicobacter pylori virulence factors in development of gastric carcinoma.

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Wang, Ming-Yi; Liu, Xiao-Fei; Gao, Xiao-Zhong

2015-01-01

Helicobacter pylori plays a vital role in the pathogenesis of gastric carcinoma. However, only a relatively small proportion of individuals infected with H. pylori develop gastric carcinoma. Differences in the incidence of gastric carcinoma among infected individuals can be explained, at least partly, by the different genotypes of H. pylori virulence factors. Thus far, many virulence factors of H. pylori, such as Cag PAI, VacA, OMPs and DupA, have been reported to be involved in the development of gastric cancer. The risk of developing gastric cancer during H. pylori infection is affected by specific host-microbe interactions that are independent of H. pylori virulence factors. In this review, we discuss virulence factors of H. pylori and their role in the development of gastric carcinoma that will provide further understanding of the biological interactions of H. pylori with the host.

The Toxin and Virulence Database: A Resource for Signature Development and Analysis of Virulence

National Research Council Canada - National Science Library

Wolinsky, Murray A

2004-01-01

In this joint effort with the University of Alabama at Birmingham, Walter Reed, MITRE and USAMRIID, we are developing a comprehensive database for microbial toxins and virulence factors (www.tvfac.lanl.gov...

Virulence genes and subclone status as markers of experimental virulence in a murine sepsis model among Escherichia coli sequence type 131 clinical isolates from Spain.

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Irene Merino

Full Text Available To assess experimental virulence among sequence type 131 (ST131 Escherichia coli bloodstream isolates in relation to virulence genotype and subclone.We analysed 48 Spanish ST131 bloodstream isolates (2010 by PCR for ST131 subclone status (H30Rx, H30 non-Rx, or non-H30, virulence genes (VGs, and O-type. Then we compared these traits with virulence in a murine sepsis model, as measured by illness severity score (ISS and rapid lethality (mean ISS ≥ 4.Of the 48 study isolates, 65% were H30Rx, 21% H30 non-Rx, and 15% non-H30; 44% produced ESBLs, 98% were O25b, and 83% qualified as extraintestinal pathogenic E. coli (ExPEC. Of 49 VGs, ibeA and iss were associated significantly with non-H30 isolates, and sat, iha and malX with H30 isolates. Median VG scores differed by subclone, i.e., 12 (H30Rx, 10 (H30 non-Rx, and 11 (non-H30 (p < 0.01. Nearly 80% of isolates represented a described virotype. In mice, H30Rx and non-H30 isolates were more virulent than H30 non-Rx isolates (according to ISS [p = 0.03] and rapid lethality [p = 0.03], as were ExPEC isolates compared with non-ExPEC isolates (median ISS, 4.3 vs. 2.7: p = 0.03. In contrast, most individual VGs, VG scores, VG profiles, and virotypes were not associated with mouse virulence.ST131 subclone and ExPEC status, but not individual VGs, VG scores or profiles, or virotypes, predicted mouse virulence. Given the lower virulence of non-Rx H30 isolates, hypervirulence probably cannot explain the ST131-H30 clade's epidemic emergence.

Somatic cancer variant curation and harmonization through consensus minimum variant level data

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Deborah I. Ritter

2016-11-01

Full Text Available Abstract Background To truly achieve personalized medicine in oncology, it is critical to catalog and curate cancer sequence variants for their clinical relevance. The Somatic Working Group (WG of the Clinical Genome Resource (ClinGen, in cooperation with ClinVar and multiple cancer variant curation stakeholders, has developed a consensus set of minimal variant level data (MVLD. MVLD is a framework of standardized data elements to curate cancer variants for clinical utility. With implementation of MVLD standards, and in a working partnership with ClinVar, we aim to streamline the somatic variant curation efforts in the community and reduce redundancy and time burden for the interpretation of cancer variants in clinical practice. Methods We developed MVLD through a consensus approach by i reviewing clinical actionability interpretations from institutions participating in the WG, ii conducting extensive literature search of clinical somatic interpretation schemas, and iii survey of cancer variant web portals. A forthcoming guideline on cancer variant interpretation, from the Association of Molecular Pathology (AMP, can be incorporated into MVLD. Results Along with harmonizing standardized terminology for allele interpretive and descriptive fields that are collected by many databases, the MVLD includes unique fields for cancer variants such as Biomarker Class, Therapeutic Context and Effect. In addition, MVLD includes recommendations for controlled semantics and ontologies. The Somatic WG is collaborating with ClinVar to evaluate MVLD use for somatic variant submissions. ClinVar is an open and centralized repository where sequencing laboratories can report summary-level variant data with clinical significance, and ClinVar accepts cancer variant data. Conclusions We expect the use of the MVLD to streamline clinical interpretation of cancer variants, enhance interoperability among multiple redundant curation efforts, and increase submission of

Detection of virulence-associated genes in Brucella melitensis ...

African Journals Online (AJOL)

Ibrahim Eldaghayes

2018-03-20

Mar 20, 2018 ... isolated from goats. This discrepancies may indicate that B. melitensis field strains prevailing in Egypt are more virulent than the strains of B. melitensis isolated from caprines in Iran. As, it was emphasized that the. T4SS of Brucella encoded by the virB operon is a major virulence factor (Delrue et al., 2005).

Use of Metarhizium anisopliae Chitinase Genes for Genotyping and Virulence Characterization

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Saliou Niassy

2013-01-01

Full Text Available Virulence is the primary factor used for selection of entomopathogenic fungi (EPF for development as biopesticides. To understand the genetic mechanisms underlying differences in virulence of fungal isolates on various arthropod pests, we compared the chitinase genes, chi2 and chi4, of 8 isolates of Metarhizium anisopliae. The clustering of the isolates showed various groups depending on their virulence. However, the analysis of their chitinase DNA sequences chi2 and chi4 did not reveal major divergences. Although their protein translates have been implicated in fungal virulence, the predicted protein structure of chi2 was identical for all isolates. Despite the critical role of chitin digestion in fungal infection, we conclude that chi2 and chi4 genes cannot serve as molecular markers to characterize observed variations in virulence among M. anisopliae isolates as previously suggested. Nevertheless, processes controlling the efficient upregulation of chitinase expression might be responsible for different virulence characteristics. Further studies using comparative “in vitro” chitin digestion techniques would be more appropriate to compare the quality and the quantity of chitinase production between fungal isolates.

Heterozygous RTEL1 variants in bone marrow failure and myeloid neoplasms.

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Marsh, Judith C W; Gutierrez-Rodrigues, Fernanda; Cooper, James; Jiang, Jie; Gandhi, Shreyans; Kajigaya, Sachiko; Feng, Xingmin; Ibanez, Maria Del Pilar F; Donaires, Flávia S; Lopes da Silva, João P; Li, Zejuan; Das, Soma; Ibanez, Maria; Smith, Alexander E; Lea, Nicholas; Best, Steven; Ireland, Robin; Kulasekararaj, Austin G; McLornan, Donal P; Pagliuca, Anthony; Callebaut, Isabelle; Young, Neal S; Calado, Rodrigo T; Townsley, Danielle M; Mufti, Ghulam J

2018-01-09

Biallelic germline mutations in RTEL1 (regulator of telomere elongation helicase 1) result in pathologic telomere erosion and cause dyskeratosis congenita. However, the role of RTEL1 mutations in other bone marrow failure (BMF) syndromes and myeloid neoplasms, and the contribution of monoallelic RTEL1 mutations to disease development are not well defined. We screened 516 patients for germline mutations in telomere-associated genes by next-generation sequencing in 2 independent cohorts; one constituting unselected patients with idiopathic BMF, unexplained cytopenia, or myeloid neoplasms (n = 457) and a second cohort comprising selected patients on the basis of the suspicion of constitutional/familial BMF (n = 59). Twenty-three RTEL1 variants were identified in 27 unrelated patients from both cohorts: 7 variants were likely pathogenic, 13 were of uncertain significance, and 3 were likely benign. Likely pathogenic RTEL1 variants were identified in 9 unrelated patients (7 heterozygous and 2 biallelic). Most patients were suspected to have constitutional BMF, which included aplastic anemia (AA), unexplained cytopenia, hypoplastic myelodysplastic syndrome, and macrocytosis with hypocellular bone marrow. In the other 18 patients, RTEL1 variants were likely benign or of uncertain significance. Telomeres were short in 21 patients (78%), and 3' telomeric overhangs were significantly eroded in 4. In summary, heterozygous RTEL1 variants were associated with marrow failure, and telomere length measurement alone may not identify patients with telomere dysfunction carrying RTEL1 variants. Pathogenicity assessment of heterozygous RTEL1 variants relied on a combination of clinical, computational, and functional data required to avoid misinterpretation of common variants.

CDKL5 variants

Science.gov (United States)

Kalscheuer, Vera M.; Hennig, Friederike; Leonard, Helen; Downs, Jenny; Clarke, Angus; Benke, Tim A.; Armstrong, Judith; Pineda, Mercedes; Bailey, Mark E.S.; Cobb, Stuart R.

2017-01-01

Objective: To provide new insights into the interpretation of genetic variants in a rare neurologic disorder, CDKL5 deficiency, in the contexts of population sequencing data and an updated characterization of the CDKL5 gene. Methods: We analyzed all known potentially pathogenic CDKL5 variants by combining data from large-scale population sequencing studies with CDKL5 variants from new and all available clinical cohorts and combined this with computational methods to predict pathogenicity. Results: The study has identified several variants that can be reclassified as benign or likely benign. With the addition of novel CDKL5 variants, we confirm that pathogenic missense variants cluster in the catalytic domain of CDKL5 and reclassify a purported missense variant as having a splicing consequence. We provide further evidence that missense variants in the final 3 exons are likely to be benign and not important to disease pathology. We also describe benign splicing and nonsense variants within these exons, suggesting that isoform hCDKL5_5 is likely to have little or no neurologic significance. We also use the available data to make a preliminary estimate of minimum incidence of CDKL5 deficiency. Conclusions: These findings have implications for genetic diagnosis, providing evidence for the reclassification of specific variants previously thought to result in CDKL5 deficiency. Together, these analyses support the view that the predominant brain isoform in humans (hCDKL5_1) is crucial for normal neurodevelopment and that the catalytic domain is the primary functional domain. PMID:29264392

Regulators Involved in Dickeya solani Virulence, Genetic Conservation and Functional Variability.

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Potrykus, Marta; Golanowska, Małgorzata; Hugouvieux-Cotte-Pattat, Nicole; Lojkowska, Ewa

2015-01-01

Bacteria from the genus Dickeya (formerly Erwinia chrysanthemi) are plant pathogens causing severe diseases in many economically important crops. A majority of the strains responsible for potato disease in Europe belong to a newly identified Dickeya solani species. Although some ecological and epidemiological studies have been carried out, little is known about the regulation of D. solani virulence. The characterization of four D. solani strains indicates significant differences in their virulence on potato although they are genetically similar based on genomic fingerprinting profiles. A phenotypic examination included an analysis of virulence on potato, growth rate in culture, motility, Fe 3+ chelation, and pectate lyase, cellulase, protease, biosurfactant and blue pigment production. Mutants of four D. solani strains were constructed by inactivating the genes coding either for one of the main negative regulators of D. dadantii virulence (kdgR, pecS and pecT) or for the synthesis and perception of signaling molecules (expI and expR). Analysis of these mutants indicated that PecS, PecT and KdgR play a similar role in both species, repressing to different degrees the synthesis of virulence factors. The thermoregulator PecT seems to be a major regulator of D. solani virulence. This work also reveals the role of quorum sensing mediated by ExpI and ExpR in D. solani virulence on potato.

Rare variants in RTEL1 are associated with familial interstitial pneumonia.

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Cogan, Joy D; Kropski, Jonathan A; Zhao, Min; Mitchell, Daphne B; Rives, Lynette; Markin, Cheryl; Garnett, Errine T; Montgomery, Keri H; Mason, Wendi R; McKean, David F; Powers, Julia; Murphy, Elissa; Olson, Lana M; Choi, Leena; Cheng, Dong-Sheng; Blue, Elizabeth Marchani; Young, Lisa R; Lancaster, Lisa H; Steele, Mark P; Brown, Kevin K; Schwarz, Marvin I; Fingerlin, Tasha E; Schwartz, David A; Lawson, William E; Loyd, James E; Zhao, Zhongming; Phillips, John A; Blackwell, Timothy S

2015-03-15

Up to 20% of cases of idiopathic interstitial pneumonia cluster in families, comprising the syndrome of familial interstitial pneumonia (FIP); however, the genetic basis of FIP remains uncertain in most families. To determine if new disease-causing rare genetic variants could be identified using whole-exome sequencing of affected members from FIP families, providing additional insights into disease pathogenesis. Affected subjects from 25 kindreds were selected from an ongoing FIP registry for whole-exome sequencing from genomic DNA. Candidate rare variants were confirmed by Sanger sequencing, and cosegregation analysis was performed in families, followed by additional sequencing of affected individuals from another 163 kindreds. We identified a potentially damaging rare variant in the gene encoding for regulator of telomere elongation helicase 1 (RTEL1) that segregated with disease and was associated with very short telomeres in peripheral blood mononuclear cells in 1 of 25 families in our original whole-exome sequencing cohort. Evaluation of affected individuals in 163 additional kindreds revealed another eight families (4.7%) with heterozygous rare variants in RTEL1 that segregated with clinical FIP. Probands and unaffected carriers of these rare variants had short telomeres (RTEL1 function. Rare loss-of-function variants in RTEL1 represent a newly defined genetic predisposition for FIP, supporting the importance of telomere-related pathways in pulmonary fibrosis.

Genetically Engineered Virulent Phage Banks in the Detection and Control of Emergent Pathogenic Bacteria

Science.gov (United States)

Blois, Hélène; Iris, François

2010-01-01

Natural outbreaks of multidrug-resistant microorganisms can cause widespread devastation, and several can be used or engineered as agents of bioterrorism. From a biosecurity standpoint, the capacity to detect and then efficiently control, within hours, the spread and the potential pathological effects of an emergent outbreak, for which there may be no effective antibiotics or vaccines, become key challenges that must be met. We turned to phage engineering as a potentially highly flexible and effective means to both detect and eradicate threats originating from emergent (uncharacterized) bacterial strains. To this end, we developed technologies allowing us to (1) concurrently modify multiple regions within the coding sequence of a gene while conserving intact the remainder of the gene, (2) reversibly interrupt the lytic cycle of an obligate virulent phage (T4) within its host, (3) carry out efficient insertion, by homologous recombination, of any number of engineered genes into the deactivated genomes of a T4 wild-type phage population, and (4) reactivate the lytic cycle, leading to the production of engineered infective virulent recombinant progeny. This allows the production of very large, genetically engineered lytic phage banks containing, in an E. coli host, a very wide spectrum of variants for any chosen phage-associated function, including phage host-range. Screening of such a bank should allow the rapid isolation of recombinant T4 particles capable of detecting (ie, diagnosing), infecting, and destroying hosts belonging to gram-negative bacterial species far removed from the original E. coli host. PMID:20569057

Assessment of polymorphic variants in the melanocortin-1 receptor gene with cutaneous pigmentation using an evolutionary approach.

Science.gov (United States)

Kanetsky, Peter A; Ge, Fan; Najarian, Derek; Swoyer, Jennifer; Panossian, Saarene; Schuchter, Lynn; Holmes, Robin; Guerry, DuPont; Rebbeck, Timothy R

2004-05-01

The melanocortin-1 receptor gene (MC1R) encodes a membrane-bound receptor protein that is central to melanin synthesis. The coding region of MC1R is highly polymorphic and associations of variants with pigmentation phenotypes and risk for cutaneous neoplasms have been reported. We sought to determine the distribution and frequency of MC1R variants and their relationship to pigmentation characteristics in 179 Caucasian controls from the United States. One hundred thirty-five (75.4%) subjects carried one or more variants, and we determined that carriage of the previously designated "red hair color" (RHC) alleles, R151C, R160W, and D294H was strongly associated with fair pigmentation phenotypes including light hair and eye color, tendency to burn, decreased tendency to tan, and freckling. We used SIFT software to define MC1R protein positions that were predicted intolerant to amino acid substitutions; detected variants that corresponded to intolerant substitutions were D84E, R142H, R151C, I155T, R160W, and D294H. Carriage of one or more of these putative functionally important variants or the frameshift variant ins86A was significantly associated with fair pigmentation phenotypes. Analyses limited to carriage of ins86A and the three non-RHC alleles identified by SIFT were attenuated and no longer reached statistical significance. This is the first study to describe MC1R variants among control subjects from the U.S. Our results indicate that the frequency of variants is similar to that previously observed among non-U.S. Caucasians. Risk variants defined by either the published literature or by evolutionary criteria are strongly and significantly associated with all fair pigmentation phenotypes that were measured.

Proteomics Analysis Reveals Previously Uncharacterized Virulence Factors in Vibrio proteolyticus

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Ann Ray

2016-07-01

Full Text Available Members of the genus Vibrio include many pathogens of humans and marine animals that share genetic information via horizontal gene transfer. Hence, the Vibrio pan-genome carries the potential to establish new pathogenic strains by sharing virulence determinants, many of which have yet to be characterized. Here, we investigated the virulence properties of Vibrio proteolyticus, a Gram-negative marine bacterium previously identified as part of the Vibrio consortium isolated from diseased corals. We found that V. proteolyticus causes actin cytoskeleton rearrangements followed by cell lysis in HeLa cells in a contact-independent manner. In search of the responsible virulence factor involved, we determined the V. proteolyticus secretome. This proteomics approach revealed various putative virulence factors, including active type VI secretion systems and effectors with virulence toxin domains; however, these type VI secretion systems were not responsible for the observed cytotoxic effects. Further examination of the V. proteolyticus secretome led us to hypothesize and subsequently demonstrate that a secreted hemolysin, belonging to a previously uncharacterized clan of the leukocidin superfamily, was the toxin responsible for the V. proteolyticus-mediated cytotoxicity in both HeLa cells and macrophages. Clearly, there remains an armory of yet-to-be-discovered virulence factors in the Vibrio pan-genome that will undoubtedly provide a wealth of knowledge on how a pathogen can manipulate host cells.

Mechanisms of disease: Helicobacter pylori virulence factors.

Science.gov (United States)

Yamaoka, Yoshio

2010-11-01

Helicobacter pylori plays an essential role in the development of various gastroduodenal diseases; however, only a small proportion of people infected with H. pylori develop these diseases. Some populations that have a high prevalence of H. pylori infection also have a high incidence of gastric cancer (for example, in East Asia), whereas others do not (for example, in Africa and South Asia). Even within East Asia, the incidence of gastric cancer varies (decreasing in the south). H. pylori is a highly heterogeneous bacterium and its virulence varies geographically. Geographic differences in the incidence of gastric cancer can be explained, at least in part, by the presence of different types of H. pylori virulence factor, especially CagA, VacA and OipA. However, it is still unclear why the pathogenicity of H. pylori increased as it migrated from Africa to East Asia during the course of evolution. H. pylori infection is also thought to be involved in the development of duodenal ulcer, which is at the opposite end of the disease spectrum to gastric cancer. This discrepancy can be explained in part by the presence of H. pylori virulence factor DupA. Despite advances in our understanding of the development of H. pylori-related diseases, further work is required to clarify the roles of H. pylori virulence factors.

A machine learning model to determine the accuracy of variant calls in capture-based next generation sequencing.

Science.gov (United States)

van den Akker, Jeroen; Mishne, Gilad; Zimmer, Anjali D; Zhou, Alicia Y

2018-04-17

Next generation sequencing (NGS) has become a common technology for clinical genetic tests. The quality of NGS calls varies widely and is influenced by features like reference sequence characteristics, read depth, and mapping accuracy. With recent advances in NGS technology and software tools, the majority of variants called using NGS alone are in fact accurate and reliable. However, a small subset of difficult-to-call variants that still do require orthogonal confirmation exist. For this reason, many clinical laboratories confirm NGS results using orthogonal technologies such as Sanger sequencing. Here, we report the development of a deterministic machine-learning-based model to differentiate between these two types of variant calls: those that do not require confirmation using an orthogonal technology (high confidence), and those that require additional quality testing (low confidence). This approach allows reliable NGS-based calling in a clinical setting by identifying the few important variant calls that require orthogonal confirmation. We developed and tested the model using a set of 7179 variants identified by a targeted NGS panel and re-tested by Sanger sequencing. The model incorporated several signals of sequence characteristics and call quality to determine if a variant was identified at high or low confidence. The model was tuned to eliminate false positives, defined as variants that were called by NGS but not confirmed by Sanger sequencing. The model achieved very high accuracy: 99.4% (95% confidence interval: +/- 0.03%). It categorized 92.2% (6622/7179) of the variants as high confidence, and 100% of these were confirmed to be present by Sanger sequencing. Among the variants that were categorized as low confidence, defined as NGS calls of low quality that are likely to be artifacts, 92.1% (513/557) were found to be not present by Sanger sequencing. This work shows that NGS data contains sufficient characteristics for a machine-learning-based model to

Genetic and Virulent Difference Between Pigmented and Non-pigmented Staphylococcus aureus.

Science.gov (United States)

Zhang, Jing; Suo, Yujuan; Zhang, Daofeng; Jin, Fangning; Zhao, Hang; Shi, Chunlei

2018-01-01

Staphyloxanthin (STX), a golden carotenoid pigment produced by Staphylococcus aureus , is suggested to act as an important virulence factor due to its antioxidant properties. Restraining biosynthesis of STX was considered as an indicator of virulence decline in pigmented S. aureus isolates. However, it is not clear whether natural non-pigmented S. aureus isolates have less virulence than pigmented ones. In this study, it is aimed to compare the pigmented and non-pigmented S. aureus isolates to clarify the genetic and virulent differences between the two groups. Here, 132 S. aureus isolates were divided into two phenotype groups depending on the absorbance (OD 450 ) of the extracted carotenoids. Then, all isolates were subjected to spa typing and multilocus sequence typing (MLST), and then the detection of presence of 30 virulence factors and the gene integrity of crtN and crtM . Furthermore, 24 typical S. aureus isolates and 4 S. argenteus strains were selected for the murine infection assay of in vivo virulence, in which the histological observation and enumeration of CFUs were carried out. These isolates were distributed in 26 sequence types (STs) and 49 spa types. The pigmented isolates were scattered in 25 STs, while the non-pigmented isolates were more centralized, which mainly belonged to ST20 (59%) and ST25 (13%). Among the 54 non-pigmented isolates, about 20% carried intact crtN and crtM genes. The in vivo assay suggested that comparing with pigmented S. aureus , non-pigmented S. aureus and S. argenteus strains did not show a reduced virulence in murine sepsis models. Therefore, it suggested that there were no significant genetic and virulent differences between pigmented and non-pigmented S. aureus .

Detection of virulence factors and molecular typing of pathogenic Leptospira from capybara (Hydrochaeris hydrochaeris).

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Jorge, Sérgio; Monte, Leonardo G; Coimbra, Marco Antonio; Albano, Ana Paula; Hartwig, Daiane D; Lucas, Caroline; Seixas, Fabiana K; Dellagostin, Odir A; Hartleben, Cláudia P

2012-10-01

Leptospirosis is a globally prevalent zoonosis caused by pathogenic Leptospira spp.; several serologic variants have reservoirs in synanthropic rodents. The capybara is the largest living rodent in the world, and it has a wide geographical distribution in Central and South America. This rodent is a significant source of Leptospira since the agent is shed via urine into the environment and is a potential public health threat. In this study, we isolated and identified by molecular techniques a pathogenic Leptospira from capybara in southern Brazil. The isolated strain was characterized by partial rpoB gene sequencing and variable-number tandem-repeats analysis as L. interrogans, serogroup Icterohaemorrhagiae. In addition, to confirm the expression of virulence factors, the bacterial immunoglobulin-like proteins A and B expression was detected by indirect immunofluorescence using leptospiral specific monoclonal antibodies. This report identifies capybaras as an important source of infection and provides insight into the epidemiology of leptospirosis.

Definition of a virulence-related antigen of Neisseria gonorrhoeae with monoclonal antibodies and lectins.

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Demarco de Hormaeche, R; Bundell, C; Chong, H; Taylor, D W; Wildy, P

1986-03-01

Variants of one strain of Neisseria gonorrhoeae, grown in vivo or in vitro, that have been previously shown to differ in infectivity, serum resistance, and capsule production were compared with use of monoclonal antibodies and lectins. Monoclonal antibodies to virulent gonococci recognized an antigenic site of the lipopolysaccharide (LPS) produced in large amounts by gonococci grown in vivo but present only in a small proportion of in vitro-grown gonococci. This antigen (C-LPS) was found in all 85 different gonococcal isolates studied but not among nonpathogenic neisseriae. It was shared by group B and C meningococci but not by groups A and D. Enzyme-linked immunosorbent assay and Western blot analysis showed that N-acetylglucosamine and N-acetylgalactosamine form part of the epitope. The C-LPS antigen was shown by immunofluorescence to be present on the surface of the gonococci and also free as slime. This antigen appears to confer resistance to killing by normal sera.

[Virulence markers of Escherichia coli O1 strains].

Science.gov (United States)

Makarova, M A; Kaftyreva, L A; Grigor'eva, N S; Kicha, E V; Lipatova, L A

2011-01-01

To detect virulence genes in clinical isolates of Escherichia coli O1 using polymerase chain reaction (PCR). One hundred and twenty strains of E.coli O1 strains isolated from faeces of patients with acute diarrhea (n = 45) and healthy persons (n = 75) were studied. PCR with primers for rfb and fliC genes, which control synthesis of O- and H- antigens respectively, was used. Fourteen virulence genes (pap, aaf, sfa, afa, eaeA, bfpA, ial, hly, cnf, stx1, stx2, lt, st, and aer) were detected by PCR primers. K1-antigen was determined by Pastorex Meningo B/E. coli O1 kit (Bio-Rad). rfb gene controlling O-antigen synthesis in serogroup O1 as well as fliC gene controlling synthesis of H7 and K1 antigens were detected in all strains. Thus all E. coli strains had antigenic structure O1:K1 :H-:F7. Virulence genes aafl, sfa, afa, eaeA, bfpA, ial, hly, cnf, stx1, stx2, lt, and st were not detected. All strains owned pap and aer genes regardless of the presence of acute diarrhea symptoms. It was shown that E. coli O1:KI:H-:F7 strains do not have virulence genes which are characteristic for diarrhea-causing Escherichia. In accordance with the presence of pap and aer genes they could be attributed to uropathogenic Escherichia (UPEC) or avian-pathogenic Escherichia (APEC). It is necessary to detect virulence factors in order to determine E. coli as a cause of intestinal infection.

Virulence factors of the Mycobacterium tuberculosis complex

Science.gov (United States)

Forrellad, Marina A.; Klepp, Laura I.; Gioffré, Andrea; Sabio y García, Julia; Morbidoni, Hector R.; Santangelo, María de la Paz; Cataldi, Angel A.; Bigi, Fabiana

2013-01-01

The Mycobacterium tuberculosis complex (MTBC) consists of closely related species that cause tuberculosis in both humans and animals. This illness, still today, remains to be one of the leading causes of morbidity and mortality throughout the world. The mycobacteria enter the host by air, and, once in the lungs, are phagocytated by macrophages. This may lead to the rapid elimination of the bacillus or to the triggering of an active tuberculosis infection. A large number of different virulence factors have evolved in MTBC members as a response to the host immune reaction. The aim of this review is to describe the bacterial genes/proteins that are essential for the virulence of MTBC species, and that have been demonstrated in an in vivo model of infection. Knowledge of MTBC virulence factors is essential for the development of new vaccines and drugs to help manage the disease toward an increasingly more tuberculosis-free world. PMID:23076359

Natural Selection in Virulence Genes of Francisella tularensis.

Science.gov (United States)

Gunnell, Mark K; Robison, Richard A; Adams, Byron J

2016-06-01

A fundamental tenet of evolution is that alleles that are under negative selection are often deleterious and confer no evolutionary advantage. Negatively selected alleles are removed from the gene pool and are eventually extinguished from the population. Conversely, alleles under positive selection do confer an evolutionary advantage and lead to an increase in the overall fitness of the organism. These alleles increase in frequency until they eventually become fixed in the population. Francisella tularensis is a zoonotic pathogen and a potential biothreat agent. The most virulent type of F. tularensis, Type A, is distributed across North America with Type A.I occurring mainly in the east and Type A.II appearing mainly in the west. F. tularensis is thought to be a genome in decay (losing genes) because of the relatively large number of pseudogenes present in its genome. We hypothesized that the observed frequency of gene loss/pseudogenes may be an artifact of evolution in response to a changing environment, and that genes involved in virulence should be under strong positive selection. To test this hypothesis, we sequenced and compared whole genomes of Type A.I and A.II isolates. We analyzed a subset of virulence and housekeeping genes from several F. tularensis subspecies genomes to ascertain the presence and extent of positive selection. Eleven previously identified virulence genes were screened for positive selection along with 10 housekeeping genes. Analyses of selection yielded one housekeeping gene and 7 virulence genes which showed significant evidence of positive selection at loci implicated in cell surface structures and membrane proteins, metabolism and biosynthesis, transcription, translation and cell separation, and substrate binding and transport. Our results suggest that while the loss of functional genes through disuse could be accelerated by negative selection, the genome decay in Francisella could also be the byproduct of adaptive evolution

Crystal structure of B acillus anthracis virulence regulator AtxA and effects of phosphorylated histidines on multimerization and activity: AtxA multimerization, phosphorylation and activity

Energy Technology Data Exchange (ETDEWEB)

Hammerstrom, Troy G.; Lori, Horton B.; Swick, Michelle C.; Joachimiak, Andrzej; Osipiuk, Jerzy; Koehler, Theresa M.

2014-12-30

The Bacillus anthracis virulence regulator AtxA controls transcription of the anthrax toxin genes and capsule biosynthetic operon. AtxA activity is elevated during growth in media containing glucose and CO2/bicarbonate, and there is a positive correlation between the CO2/bicarbonate signal, AtxA activity and homomultimerization. AtxA activity is also affected by phosphorylation at specific histidines. We show that AtxA crystallizes as a dimer. Distinct folds associated with predicted DNA-binding domains (HTH1 and HTH2) and phosphoenolpyruvate: carbohydrate phosphotransferase system-regulated domains (PRD1 and PRD2) are apparent. We tested AtxA variants containing single and double phosphomimetic (HisAsp) and phosphoablative (HisAla) amino acid changes for activity in B.anthracis cultures and for protein-protein interactions in cell lysates. Reduced activity of AtxA H199A, lack of multimerization and activity of AtxAH379D variants, and predicted structural changes associated with phosphorylation support a model for control of AtxA function. We propose that (i) in the AtxA dimer, phosphorylation of H199 in PRD1 affects HTH2 positioning, influencing DNA-binding; and (ii) phosphorylation of H379 in PRD2 disrupts dimer formation. The AtxA structure is the first reported high-resolution full-length structure of a PRD-containing regulator, and can serve as a model for proteins of this family, especially those that link virulence to bacterial metabolism.

Sporangiospore size dimorphism is linked to virulence of Mucor circinelloides.

Science.gov (United States)

Li, Charles H; Cervantes, Maria; Springer, Deborah J; Boekhout, Teun; Ruiz-Vazquez, Rosa M; Torres-Martinez, Santiago R; Heitman, Joseph; Lee, Soo Chan

2011-06-01

Mucor circinelloides is a zygomycete fungus and an emerging opportunistic pathogen in immunocompromised patients, especially transplant recipients and in some cases otherwise healthy individuals. We have discovered a novel example of size dimorphism linked to virulence. M. circinelloides is a heterothallic fungus: (+) sex allele encodes SexP and (-) sex allele SexM, both of which are HMG domain protein sex determinants. M. circinelloides f. lusitanicus (Mcl) (-) mating type isolates produce larger asexual sporangiospores that are more virulent in the wax moth host compared to (+) isolates that produce smaller less virulent sporangiospores. The larger sporangiospores germinate inside and lyse macrophages, whereas the smaller sporangiospores do not. sexMΔ mutants are sterile and still produce larger virulent sporangiospores, suggesting that either the sex locus is not involved in virulence/spore size or the sexP allele plays an inhibitory role. Phylogenetic analysis supports that at least three extant subspecies populate the M. circinelloides complex in nature: Mcl, M. circinelloides f. griseocyanus, and M. circinelloides f. circinelloides (Mcc). Mcc was found to be more prevalent among clinical Mucor isolates, and more virulent than Mcl in a diabetic murine model in contrast to the wax moth host. The M. circinelloides sex locus encodes an HMG domain protein (SexP for plus and SexM for minus mating types) flanked by genes encoding triose phosphate transporter (TPT) and RNA helicase homologs. The borders of the sex locus between the three subspecies differ: the Mcg sex locus includes the promoters of both the TPT and the RNA helicase genes, whereas the Mcl and Mcc sex locus includes only the TPT gene promoter. Mating between subspecies was restricted compared to mating within subspecies. These findings demonstrate that spore size dimorphism is linked to virulence of M. circinelloides species and that plasticity of the sex locus and adaptations in pathogenicity have

Genetic and Virulent Difference Between Pigmented and Non-pigmented Staphylococcus aureus

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Jing Zhang

2018-04-01

Full Text Available Staphyloxanthin (STX, a golden carotenoid pigment produced by Staphylococcus aureus, is suggested to act as an important virulence factor due to its antioxidant properties. Restraining biosynthesis of STX was considered as an indicator of virulence decline in pigmented S. aureus isolates. However, it is not clear whether natural non-pigmented S. aureus isolates have less virulence than pigmented ones. In this study, it is aimed to compare the pigmented and non-pigmented S. aureus isolates to clarify the genetic and virulent differences between the two groups. Here, 132 S. aureus isolates were divided into two phenotype groups depending on the absorbance (OD450 of the extracted carotenoids. Then, all isolates were subjected to spa typing and multilocus sequence typing (MLST, and then the detection of presence of 30 virulence factors and the gene integrity of crtN and crtM. Furthermore, 24 typical S. aureus isolates and 4 S. argenteus strains were selected for the murine infection assay of in vivo virulence, in which the histological observation and enumeration of CFUs were carried out. These isolates were distributed in 26 sequence types (STs and 49 spa types. The pigmented isolates were scattered in 25 STs, while the non-pigmented isolates were more centralized, which mainly belonged to ST20 (59% and ST25 (13%. Among the 54 non-pigmented isolates, about 20% carried intact crtN and crtM genes. The in vivo assay suggested that comparing with pigmented S. aureus, non-pigmented S. aureus and S. argenteus strains did not show a reduced virulence in murine sepsis models. Therefore, it suggested that there were no significant genetic and virulent differences between pigmented and non-pigmented S. aureus.

Comparative genomics of Beauveria bassiana: uncovering signatures of virulence against mosquitoes.

Science.gov (United States)

Valero-Jiménez, Claudio A; Faino, Luigi; Spring In't Veld, Daphne; Smit, Sandra; Zwaan, Bas J; van Kan, Jan A L

2016-12-01

Entomopathogenic fungi such as Beauveria bassiana are promising biological agents for control of malaria mosquitoes. Indeed, infection with B. bassiana reduces the lifespan of mosquitoes in the laboratory and in the field. Natural isolates of B. bassiana show up to 10-fold differences in virulence between the most and the least virulent isolate. In this study, we sequenced the genomes of five isolates representing the extremes of low/high virulence and three RNA libraries, and applied a genome comparison approach to uncover genetic mechanisms underpinning virulence. A high-quality, near-complete genome assembly was achieved for the highly virulent isolate Bb8028, which was compared to the assemblies of the four other isolates. Whole genome analysis showed a high level of genetic diversity between the five isolates (2.85-16.8 SNPs/kb), which grouped into two distinct phylogenetic clusters. Mating type gene analysis revealed the presence of either the MAT1-1-1 or the MAT1-2-1 gene. Moreover, a putative new MAT gene (MAT1-2-8) was detected in the MAT1-2 locus. Comparative genome analysis revealed that Bb8028 contains 163 genes exclusive for this isolate. These unique genes have a tendency to cluster in the genome and to be often located near the telomeres. Among the genes unique to Bb8028 are a Non-Ribosomal Peptide Synthetase (NRPS) secondary metabolite gene cluster, a polyketide synthase (PKS) gene, and five genes with homology to bacterial toxins. A survey of candidate virulence genes for B. bassiana is presented. Our results indicate several genes and molecular processes that may underpin virulence towards mosquitoes. Thus, the genome sequences of five isolates of B. bassiana provide a better understanding of the natural variation in virulence and will offer a major resource for future research on this important biological control agent.

Screening of virulence genes in Staphylococcus aureus isolates from rabbits

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David Viana Martín

2015-09-01

Full Text Available Staphylococcus aureus is a versatile pathogen able to cause disease in both humans and animals. In rabbits, this bacterium infects animals of different ages, producing several purulent lesions. The ability of S. aureus to cause disease depends on a combination of virulence factors. The aim of this study was therefore to investigate the distribution of bacterial virulence determinants in 69 S. aureus isolates from rabbits. Some virulence factors (7 adhesins, 1 toxin and 1 protease were positive in all rabbit S. aureus isolates analysed, while others (1 adhesin and 10 toxins were always negative. The remaining virulence factors were more variable among isolates. An association between genotype and the different profiles of virulence factors was observed, but not with the type of lesion (P<0.05. One strain of each genotype was further analysed by multilocus sequence typing, generating ST121, ST96 and ST2951, determining a greater number of enterotoxins in ST121 isolates compared to ST96 and ST2951 isolates, which could justify the different pathogenicity between strains. 

Genetic Regulation of Virulence and Antibiotic Resistance in Acinetobacter baumannii

Science.gov (United States)

Kröger, Carsten; Kary, Stefani C.; Schauer, Kristina; Cameron, Andrew D. S.

2016-01-01

Multidrug resistant microorganisms are forecast to become the single biggest challenge to medical care in the 21st century. Over the last decades, members of the genus Acinetobacter have emerged as bacterial opportunistic pathogens, in particular as challenging nosocomial pathogens because of the rapid evolution of antimicrobial resistances. Although we lack fundamental biological insight into virulence mechanisms, an increasing number of researchers are working to identify virulence factors and to study antibiotic resistance. Here, we review current knowledge regarding the regulation of virulence genes and antibiotic resistance in Acinetobacter baumannii. A survey of the two-component systems AdeRS, BaeSR, GacSA and PmrAB explains how each contributes to antibiotic resistance and virulence gene expression, while BfmRS regulates cell envelope structures important for pathogen persistence. A. baumannii uses the transcription factors Fur and Zur to sense iron or zinc depletion and upregulate genes for metal scavenging as a critical survival tool in an animal host. Quorum sensing, nucleoid-associated proteins, and non-classical transcription factors such as AtfA and small regulatory RNAs are discussed in the context of virulence and antibiotic resistance. PMID:28036056

[Clinical and morphological variants of diverticular disease in colon].

Science.gov (United States)

Levchenko, S V; Lazebnik, L B; Potapova, V B; Rogozina, V A

2013-01-01

Our own results of two-stage research are presented in the article. The first stage contains the retrospective analysis of 3682 X-ray examining of large bowel which were conducted in 2002-2004 to define the structure of colon disease and to determine gender differences. The second stage is prospective research which took place from 2003 to 2012 and 486 patients with diverticular disease were regularly observed. Following parameters were estimated: dynamics of complaints, life quality, clinical symptoms. Multiple X-ray and endoscopic examining were done with estimation of quantity and size of diverticula, changes of colon mucosa, comparison of X-ray and endoscopic methods in prognosis of complications. Two basic clinical morphological variants of diverticular disease (DD) of colon are made out as a result of our research. There are IBD-like and DD with ischemic component. The variants differ by pain characteristics, presence of accompanying diseases, life quality parameters and description of colon mucosa morphological research. We suppose that different ethiopathogenetic factors of development of both variants mentioned above influence the disease prognosis and selection of treatment.

Carriage of extended-spectrum beta-lactamase-plasmids does not reduce fitness but enhances virulence in some strains of pandemic E. coli lineages

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Katharina eSchaufler

2016-03-01

Full Text Available Pathogenic ESBL-producing E. coli lineages occur frequently worldwide, not only in a human health context but in animals and the environment, also in settings with low antimicrobial pressures. This study investigated the fitness costs of ESBL-plasmids and their influence on chromosomally encoded features associated with virulence, such as those involved in the planktonic and sessile behaviors of ST131 and ST648 E. coli. ESBL-plasmid-carrying wild-type E. coli strains, their corresponding ESBL-plasmid-cured variants (PCV, and complementary ESBL-carrying transformants were comparatively analyzed using growth curves, Omnilog® phenotype microarray (PM assays, macrocolony and biofilm formation, swimming motility, and RNA sequence analysis. Growth curves and PM results pointed towards similar growth and metabolic behaviors among the strains. Phenotypic differences in some strains were detected, including enhanced curli fimbriae and/or cellulose production as well as a reduced swimming capacity of some ESBL-carrying strains, as compared to their respective PCVs. RNA sequencing mostly confirmed the phenotypic results, suggesting that the chromosomally encoded csgD pathway is a key factor involved. These results contradict the hypothesis that ESBL-plasmid-carriage leads to a fitness loss in ESBL-carrying strains. Instead, the results indicate an influence of some ESBL-plasmids on chromosomally encoded features associated with virulence in some E. coli strains. In conclusion, apart from antibiotic resistance selective advantages, ESBL-plasmid-carriage may also lead to enhanced virulence or adaption to specific habitats in some strains of pandemic ESBL-producing E. coli lineages.

Clonality, virulence and antimicrobial resistance of enteroaggregative Escherichia coli from Mirzapur, Bangladesh

DEFF Research Database (Denmark)

Chattaway, Marie Anne; Day, Michaela; Mtwale, Julia

2017-01-01

Purpose. This study investigates the virulence and antimicrobial resistance in association with common clonal complexes (CCs) of enteroaggregative Escherichia coli (EAEC) isolated from Bangladesh. The aim was to determine whether specific CCs were more likely to be associated with putative...... virulence genes and/or antimicrobial resistance.Methodology. The presence of 15 virulence genes (by PCR) and susceptibility to 18 antibiotics were determined for 151 EAEC isolated from cases and controls during an intestinal infectious disease study carried out between 2007-2011 in the rural setting...... between the presence of virulence or antimicrobial resistance genes in isolates of EAEC from cases versus controls. However, when stratified by clonal complex (CC) one CC associated with cases harboured more virulence factors (CC40) and one CC harboured more resistance genes (CC38) than the average...

Polyamines Are Required for Virulence in Salmonella enterica Serovar Typhimurium

DEFF Research Database (Denmark)

Jelsbak, Lotte; Thomsen, Line Elnif; Wallrodt, Inke

2012-01-01

for studying typhoid fever. Central to its virulence are two major virulence loci Salmonella Pathogenicity Island 1 and 2 (SPI1 and SPI2). SPI1 promotes invasion of epithelial cells, whereas SPI2 enables S. Typhimurium to survive and proliferate within specialized compartments inside host cells. In this study......, we show that an S. Typhimurium polyamine mutant is defective for invasion, intracellular survival, killing of the nematode Caenorhabditis elegans and systemic infection of the mouse model of typhoid fever. Virulence of the mutant could be restored by genetic complementation, and invasion...

Determination of virulence factors and biofilm formation among isolates of vulvovaginal candidiasis

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Tapan Majumdar

2016-01-01

Full Text Available Context: Under morphogenesis-inducing conditions, Candida spp. begins to undergo yeast-to-hypha switch. This shift from commensal to pathogenic state is dependent on several virulence factors. Aim: To find out whether the isolated Candida spp. were pathogens causing vulvovaginal candidiasis or mere bystanders. Settings and Design: Cross-sectional observational study conducted on 275 symptomatic hospital patients in Tripura between August 2012 and April 2015. Subjects and Methods: Discharge was collected from patients and identified by Grams staining and wet mount test. Culturing was done in Sabouraud dextrose agar followed by speciation. To test for virulence factors, assays for adherence, plasma coagulase, phospholipase, lipase, protease, hemolysin, and biofilm formation were carried out. Statistical Analysis Used: Significance between two groups was compared using one-way analysis of variance along with Tukey test, and Chi-square 2 × 2 contingency table at 95% confidence interval. Results: Fifty-six Candida spp. could be isolated in the study which was used for further virulence tests. One hundred percent of isolates expressed adherence. Among other virulence factors, maximum virulence 25 (45% was shown through protease production. Hemolysin production and biofilm formation were the second most 22 (39% expressed virulence factors. In a comparison of virulence factors between biofilm-forming isolates and planktonic cells, significant difference was seen for plasma coagulase and hemolysin production. Conclusions: All the isolates expressed one or more virulence factors. Adherence was expressed in all isolates but highest number was observed for Candida albicans. Furthermore, C. albicans strain number was highest for protease, hemolysin and coagulase expression and biofilm formation. Candida krusei isolates were the least in number for expressing any of the virulence factors. Significantly higher number of biofilm forming isolates produced

Identification of copy number variants defining genomic differences among major human groups.

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Lluís Armengol

Full Text Available BACKGROUND: Understanding the genetic contribution to phenotype variation of human groups is necessary to elucidate differences in disease predisposition and response to pharmaceutical treatments in different human populations. METHODOLOGY/PRINCIPAL FINDINGS: We have investigated the genome-wide profile of structural variation on pooled samples from the three populations studied in the HapMap project by comparative genome hybridization (CGH in different array platforms. We have identified and experimentally validated 33 genomic loci that show significant copy number differences from one population to the other. Interestingly, we found an enrichment of genes related to environment adaptation (immune response, lipid metabolism and extracellular space within these regions and the study of expression data revealed that more than half of the copy number variants (CNVs translate into gene-expression differences among populations, suggesting that they could have functional consequences. In addition, the identification of single nucleotide polymorphisms (SNPs that are in linkage disequilibrium with the copy number alleles allowed us to detect evidences of population differentiation and recent selection at the nucleotide variation level. CONCLUSIONS: Overall, our results provide a comprehensive view of relevant copy number changes that might play a role in phenotypic differences among major human populations, and generate a list of interesting candidates for future studies.

Expression of Virulence Factors by Staphylococcus aureus Grown in Serum▿†

OpenAIRE

Oogai, Yuichi; Matsuo, Miki; Hashimoto, Masahito; Kato, Fuminori; Sugai, Motoyuki; Komatsuzawa, Hitoshi

2011-01-01

Staphylococcus aureus produces many virulence factors, including toxins, immune-modulatory factors, and exoenzymes. Previous studies involving the analysis of virulence expression were mainly performed by in vitro experiments using bacterial medium. However, when S. aureus infects a host, the bacterial growth conditions are quite different from those in a medium, which may be related to the different expression of virulence factors in the host. In this study, we investigated the expression of...

Galleria mellonella model identifies highly virulent strains among all major molecular types of Cryptococcus gattii.

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Carolina Firacative

Full Text Available Cryptococcosis is mainly caused by Cryptococcus neoformans. However, the number of cases due to C. gattii is increasing, affecting mainly immunocompetent hosts. C. gattii is divided into four major molecular types, VGI to VGIV, which differ in their host range, epidemiology, antifungal susceptibility and geographic distribution. Besides studies on the Vancouver Island outbreak strains, which showed that the subtype VGIIa is highly virulent compared to the subtype VGIIb, little is known about the virulence of the other major molecular types. To elucidate the virulence potential of the major molecular types of C. gattii, Galleria mellonella larvae were inoculated with ten globally selected strains per molecular type. Survival rates were recorded and known virulence factors were studied. One VGII, one VGIII and one VGIV strain were more virulent (p 0.05, 21 (five VGI, five VGII, four VGIII and seven VGIV were less virulent (p <0.05 while one strain of each molecular type were avirulent. Cell and capsule size of all strains increased markedly during larvae infection (p <0.001. No differences in growth rate at 37°C were observed. Melanin synthesis was directly related with the level of virulence: more virulent strains produced more melanin than less virulent strains (p <0.05. The results indicate that all C. gattii major molecular types exhibit a range of virulence, with some strains having the potential to be more virulent. The study highlights the necessity to further investigate the genetic background of more and less virulent strains in order to recognize critical features, other than the known virulence factors (capsule, melanin and growth at mammalian body temperature, that maybe crucial for the development and progression of cryptococcosis.

Reconstruction of the metabolic network of Pseudomonas aeruginosa to interrogate virulence factor synthesis

DEFF Research Database (Denmark)

Bartell, Jennifer; Blazier, Anna S; Yen, Phillip

2017-01-01

Virulence-linked pathways in opportunistic pathogens are putative therapeutic targets that may be associated with less potential for resistance than targets in growth-essential pathways. However, efficacy of virulence-linked targets may be affected by the contribution of virulence-related genes t...

Invasion thresholds and the evolution of nonequilibrium virulence

OpenAIRE

Bull, J. J.; Ebert, D.

2008-01-01

Abstract The enterprise of virulence management attempts to predict how social practices and other factors affect the evolution of parasite virulence. These predictions are often based on parasite optima or evolutionary equilibria derived from models of host-parasite dynamics. Yet even when such models accurately capture the parasite optima, newly invading parasites will typically not be at their optima. Here we show that parasite invasion of a host population can occur despite highly nonopti...

Nigribactin, a Novel Siderophore from Vibrio nigripulchritudo, Modulates Staphylococcus aureus Virulence Gene Expression

DEFF Research Database (Denmark)

Nielsen, Anita; Månsson, Maria; Wietz, Matthias

2012-01-01

Staphylococcus aureus is a serious human pathogen that employs a number of virulence factors as part of its pathogenesis. The purpose of the present study was to explore marine bacteria as a source of compounds that modulate virulence gene expression in S. aureus. During the global marine Galathea...... 3 expedition, a strain collection was established comprising bacteria that express antimicrobial activity against Vibrio anguillarum and/or Staphylococcus aureus. Within this collection we searched colony material, culture supernatants, and cell extracts for virulence modulating activity showing......, enterobactin, failed to influence S. aureus virulence gene expression. This study shows that marine microorganisms produce compounds with potential use in therapeutic strategies targeting virulence rather than viability of human pathogens....

Inhibitors of Mycobacterium marinum virulence identified in a Dictyostelium discoideum host model.

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Hajer Ouertatani-Sakouhi

Full Text Available Tuberculosis remains one of the major threats to public health worldwide. Given the prevalence of multi drug resistance (MDR in Mycobacterium tuberculosis strains, there is a strong need to develop new anti-mycobacterial drugs with modes of action distinct from classical antibiotics. Inhibitors of mycobacterial virulence might target new molecular processes and may represent a potential new therapeutic alternative. In this study, we used a Dictyostelium discoideum host model to assess virulence of Mycobacterium marinum and to identify compounds inhibiting mycobacterial virulence. Among 9995 chemical compounds, we selected 12 inhibitors of mycobacterial virulence that do not inhibit mycobacterial growth in synthetic medium. Further analyses revealed that 8 of them perturbed functions requiring an intact mycobacterial cell wall such as sliding motility, bacterial aggregation or cell wall permeability. Chemical analogs of two compounds were analyzed. Chemical modifications altered concomitantly their effect on sliding motility and on mycobacterial virulence, suggesting that the alteration of the mycobacterial cell wall caused the loss of virulence. We characterized further one of the selected compounds and found that it inhibited the ability of mycobacteria to replicate in infected cells. Together these results identify new antimycobacterial compounds that represent new tools to unravel the molecular mechanisms controlling mycobacterial pathogenicity. The isolation of compounds with anti-virulence activity is the first step towards developing new antibacterial treatments.

Comparison of acute infection of calves exposed to a high-virulence or low-virulence bovine viral diarrhea virus or a HoBi-like virus

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The objective of this research was to compare clinical presentation following acute infection of cattle with either a high virulence (HV) BVDV or a low virulence (LV) BVDV to clinical presentation following infection with a viral strain that belongs to an emerging species of pestivirus. The viral st...

Contribution of the nos-pdt operon to virulence phenotypes in methicillin-sensitive Staphylococcus aureus.

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April M Sapp

Full Text Available Nitric oxide (NO is emerging as an important regulator of bacterial stress resistance, biofilm development, and virulence. One potential source of endogenous NO production in the pathogen Staphylococcus aureus is its NO-synthase (saNOS enzyme, encoded by the nos gene. Although a role for saNOS in oxidative stress resistance, antibiotic resistance, and virulence has been recently-described, insights into the regulation of nos expression and saNOS enzyme activity remain elusive. To this end, transcriptional analysis of the nos gene in S. aureus strain UAMS-1 was performed, which revealed that nos expression increases during low-oxygen growth and is growth-phase dependent. Furthermore, nos is co-transcribed with a downstream gene, designated pdt, which encodes a prephenate dehydratase (PDT enzyme involved in phenylalanine biosynthesis. Deletion of pdt significantly impaired the ability of UAMS-1 to grow in chemically-defined media lacking phenylalanine, confirming the function of this enzyme. Bioinformatics analysis revealed that the operon organization of nos-pdt appears to be unique to the staphylococci. As described for other S. aureus nos mutants, inactivation of nos in UAMS-1 conferred sensitivity to oxidative stress, while deletion of pdt did not affect this phenotype. The nos mutant also displayed reduced virulence in a murine sepsis infection model, and increased carotenoid pigmentation when cultured on agar plates, both previously-undescribed nos mutant phenotypes. Utilizing the fluorescent stain 4-Amino-5-Methylamino-2',7'-Difluorofluorescein (DAF-FM diacetate, decreased levels of intracellular NO/reactive nitrogen species (RNS were detected in the nos mutant on agar plates. These results reinforce the important role of saNOS in S. aureus physiology and virulence, and have identified an in vitro growth condition under which saNOS activity appears to be upregulated. However, the significance of the operon organization of nos-pdt and

Role of dupA in virulence of Helicobacter pylori.

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Talebi Bezmin Abadi, Amin; Perez-Perez, Guillermo

2016-12-14

Helicobacter pylori ( H. pylori ) is a gastric human pathogen associated with acute and chronic gastritis, 70% of all gastric ulcers, 85% of all duodenal ulcers, and both forms of stomach cancer, mucosal-associated lymphoid tissue (MALT) lymphoma and adenocarcinoma. Recently, attention has focused on possible relationship between presence of certain virulence factor and H. pylori -associated diseases. Some contradictory data between this bacterium and related disorders has been observed since not all the colonized individuals develop to severe disease. The reported diseases plausibility related to H. pylori specific virulence factors became an interesting story about this organism. Although a number of putative virulence factors have been identified including cytotoxin-associated gene a ( cagA ) and vacA , there are conflicting data about their actual participation as specific risk factor for H. pylori -related diseases. Duodenal ulcer promoting gene a ( dupA ) is a virulence factor of H. pylori that is highly associated with duodenal ulcer development and reduced risk of gastric cancer. The prevalence of dupA in H. pylori strains isolated from western countries is relatively higher than in H. pylori strains from Asian countries. Current confusing epidemiological reports will continue unless future sophisticated and molecular studies provide data on functional and complete dupA cluster in H. pylori infected individuals. This paper elucidates available knowledge concerning role of dupA in virulence of H. pylori after a decade of its discovery.

Genetic and Virulent Difference Between Pigmented and Non-pigmented Staphylococcus aureus

OpenAIRE

Jing Zhang; Yujuan Suo; Daofeng Zhang; Fangning Jin; Hang Zhao; Chunlei Shi

2018-01-01

Staphyloxanthin (STX), a golden carotenoid pigment produced by Staphylococcus aureus, is suggested to act as an important virulence factor due to its antioxidant properties. Restraining biosynthesis of STX was considered as an indicator of virulence decline in pigmented S. aureus isolates. However, it is not clear whether natural non-pigmented S. aureus isolates have less virulence than pigmented ones. In this study, it is aimed to compare the pigmented and non-pigmented S. aureus isolates to...

Virulence assessment of Portuguese isolates of potato cyst nematodes (Globodera spp.

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Maria José M. DA CUNHA

2012-05-01

Full Text Available Identification of species and virulence groups of potato cyst nematodes (PCN, Globodera pallida and G. rostochiensis, present in field populations is important in the control of these nematodes by means of resistant cultivars. In order to characterize the virulence of Globodera spp. isolates from Portugal, 43 G. rostochiensis and three G. pallida isolates were evaluated by measuring their multiplication rates on a susceptible potato cultivar and five differential potato genotypes in a growth chamber pot experiment. Principal Component Analysis and Hierarchical Cluster Analysis showed that the reproduction rates were different in terms of both the numbers of eggs and the numbers of cysts produced. Portuguese isolates of PCN were more virulent on genotypes derived from Solanum vernei than on genotypes derived from other Solanum resistance sources, and there was a significant nematode isolate × host genotype interaction. The virulence bioassay clearly distinguished the two PCN species but failed to differentiate isolates into pathotypes. There was a wide and continuous range of virulence to the resistant genotypes, especially in G. rostochiensis isolates.

The Role of Antibiotics in Modulating Virulence in Staphylococcus aureus.

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Hodille, Elisabeth; Rose, Warren; Diep, Binh An; Goutelle, Sylvain; Lina, Gerard; Dumitrescu, Oana

2017-10-01

Staphylococcus aureus is often involved in severe infections, in which the effects of bacterial virulence factors have great importance. Antistaphylococcal regimens should take into account the different effects of antibacterial agents on the expression of virulence factors and on the host's immune response. A PubMed literature search was performed to select relevant articles on the effects of antibiotics on staphylococcal toxin production and on the host immune response. Information was sorted according to the methods used for data acquisition (bacterial strains, growth models, and antibiotic concentrations) and the assays used for readout generation. The reported mechanisms underlying S. aureus virulence modulation by antibiotics were reviewed. The relevance of in vitro observations is discussed in relation to animal model data and to clinical evidence extracted from case reports and recommendations on the management of toxin-related staphylococcal diseases. Most in vitro data point to a decreased level of virulence expression upon treatment with ribosomally active antibiotics (linezolid and clindamycin), while cell wall-active antibiotics (beta-lactams) mainly increase exotoxin production. In vivo studies confirmed the suppressive effect of clindamycin and linezolid on virulence expression, supporting their utilization as a valuable management strategy to improve patient outcomes in cases of toxin-associated staphylococcal disease. Copyright © 2017 American Society for Microbiology.

Cough-variant asthma: a diagnostic dilemma in the occupational setting.

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Lipińska-Ojrzanowska, A; Wiszniewska, M; Walusiak-Skorupa, J

2015-03-01

Cough-variant asthma (Corrao's syndrome) is defined as the presence of chronic non-productive cough in patients with bronchial hyperresponsiveness (BHR) and response to bronchodilator therapy. This variant of asthma may present a diagnostic problem in occupational medicine. To describe additional evaluation of cough-variant asthma in a cyanoacrylate-exposed worker in whom standard diagnostic testing was negative. A female beautician was evaluated for suspected occupational allergic rhinitis and asthma. A specific inhalation challenge test (SICT) was performed with cyanoacrylate glues used for applying artificial eyelashes and nails. Spirometry and peak expiratory flow (PEF) measurements were recorded hourly for 24h; methacholine challenge testing was performed and nasal lavage (NL) samples were analysed for eosinophilia. After SICT, the patient developed sneezing, nasal airflow obstruction and cough. Declines in forced expiratory volume in 1 s and PEF were not observed. Eosinophil proportions in NL fluid increased markedly at 4 and 24h after SICT. A significant increase in BHR also occurred 24h after SICT. Clinical symptoms, post-challenge BHR and increased NL eosinophil counts confirmed a positive response to SICT and validated the diagnosis of cough-variant occupational asthma. SICT may be useful in cases where history and clinical data suggest cough-variant asthma and spirometric indices are negative. © The Author 2014. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Virulence Factors of Erwinia amylovora: A Review

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Núria Piqué

2015-06-01

Full Text Available Erwinia amylovora, a Gram negative bacteria of the Enterobacteriaceae family, is the causal agent of fire blight, a devastating plant disease affecting a wide range of host species within Rosaceae and a major global threat to commercial apple and pear production. Among the limited number of control options currently available, prophylactic application of antibiotics during the bloom period appears the most effective. Pathogen cells enter plants through the nectarthodes of flowers and other natural openings, such as wounds, and are capable of rapid movement within plants and the establishment of systemic infections. Many virulence determinants of E. amylovora have been characterized, including the Type III secretion system (T3SS, the exopolysaccharide (EPS amylovoran, biofilm formation, and motility. To successfully establish an infection, E. amylovora uses a complex regulatory network to sense the relevant environmental signals and coordinate the expression of early and late stage virulence factors involving two component signal transduction systems, bis-(3′-5′-cyclic di-GMP (c-di-GMP and quorum sensing. The LPS biosynthetic gene cluster is one of the relatively few genetic differences observed between Rubus- and Spiraeoideae-infecting genotypes of E. amylovora. Other differential factors, such as the presence and composition of an integrative conjugative element associated with the Hrp T3SS (hrp genes encoding the T3SS apparatus, have been recently described. In the present review, we present the recent findings on virulence factors research, focusing on their role in bacterial pathogenesis and indicating other virulence factors that deserve future research to characterize them.

An attemp at reversibility and increase of the virulence of axenic strains of Entamoeba histolytica Tentativa de reversibilidade e aumento de virulência de cepas axônicas de Entamoeba histolytica

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Maria Aparecida Gomes

1993-12-01

Full Text Available In this study we have tried to verify whether the interaction "in vitro" with bacteria or small pieces of normal hamster liver would modify the pathogenic behavior of axenic strains of E. histolytica: avirulent ones (ICB-32 and ICB-RPS, of attenuated virulence (ICB-CSP and HM1 and of mean virulence (ICB-462. Every attempt to render virulent, recover or increase the virulence of axenic strains of E. histolytica has failedNeste trabalho procuramos verificar se a interação "in vitro" com bactérias e fragmentos de fígado de hamster normal, modificaria o comportamento patogênico de cepas axênicas de E. histolytica avirulentas (ICB-32 e ICB-RPS; virulentas, porém atenuadas (ICB-CSP e HM1 e de média virulência (ICB-462. Todas as tentativas de tornar virulentas, restabelecer ou aumentar a virulência das cepas axênicas de E. histolytica utilizadas fracassaram

How Listeria monocytogenes organizes its surface for virulence

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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

Effect of salt and acidic pH on the stability of virulence plasmid (pYV) in Yersinia enterocolitica and expression of virulence-associated characteristics

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The stability of the Yersinia enterocolitica virulence plasmid (pYV) under different NaCl concentrations and under acidic pH conditions was investigated. Exposure of five strains representing five serotypes of pYV-bearing virulent Y. enterocolitica to 0.5, 2 and 5% NaCl and under conditions of pH 4...

Genotypes and pathogenicity of cellulitis isolates reveal traits that modulate APEC virulence.

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Nicolle Lima Barbieri

Full Text Available We characterized 144 Escherichia coli isolates from severe cellulitis lesions in broiler chickens from South Brazil. Analysis of susceptibility to 15 antimicrobials revealed frequencies of resistance of less than 30% for most antimicrobials except tetracycline (70% and sulphonamides (60%. The genotyping of 34 virulence-associated genes revealed that all the isolates harbored virulence factors related to adhesion, iron acquisition and serum resistance, which are characteristic of the avian pathogenic E. coli (APEC pathotype. ColV plasmid-associated genes (cvi/cva, iroN, iss, iucD, sitD, traT, tsh were especially frequent among the isolates (from 66.6% to 89.6%. According to the Clermont method of ECOR phylogenetic typing, isolates belonged to group D (47.2%, to group A (27.8%, to group B2 (17.4% and to group B1 (7.6%; the group B2 isolates contained the highest number of virulence-associated genes. Clonal relationship analysis using the ARDRA method revealed a similarity level of 57% or higher among isolates, but no endemic clone. The virulence of the isolates was confirmed in vivo in one-day-old chicks. Most isolates (72.9% killed all infected chicks within 7 days, and 65 isolates (38.1% killed most of them within 24 hours. In order to analyze differences in virulence among the APEC isolates, we created a pathogenicity score by combining the times of death with the clinical symptoms noted. By looking for significant associations between the presence of virulence-associated genes and the pathogenicity score, we found that the presence of genes for invasins ibeA and gimB and for group II capsule KpsMTII increased virulence, while the presence of pic decreased virulence. The fact that ibeA, gimB and KpsMTII are characteristic of neonatal meningitis E. coli (NMEC suggests that genes of NMEC in APEC increase virulence of strains.

Limiting opportunities for cheating stabilizes virulence in insect parasitic nematodes

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Cooperative secretion of virulence factors by pathogens can often lead to social conflict as cheating mutants that benefit from collective action, but do not contribute to it, can arise and locally outcompete cooperators within hosts, leading to loss of virulence. There is a wide range of in vivo st...

Type VI Secretion is a Major Virulence Determinant in Burkholderia Mallei

National Research Council Canada - National Science Library

Schell, Mark A; Ulrich, Ricky L; Ribot, Wilson J; Brueggemann, Ernst E; Hines, Harry B; Chen, Dan; Lipscomb, Lyla; Kim, H. S; Mrazek, Jan; Nierman, William C; DeShazer, David

2007-01-01

Burkholderia mallei is a host-adapted pathogen and a category B biothreat agent. Although the B. mallei VirAG two-component regulatory system is required for virulence in hamsters, the virulence genes it regulates are unknown...

Diversities in virulence, antifungal activity, pigmentation and DNA fingerprint among strains of Burkholderia glumae.

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Karki, Hari S; Shrestha, Bishnu K; Han, Jae Woo; Groth, Donald E; Barphagha, Inderjit K; Rush, Milton C; Melanson, Rebecca A; Kim, Beom Seok; Ham, Jong Hyun

2012-01-01

Burkholderia glumae is the primary causal agent of bacterial panicle blight of rice. In this study, 11 naturally avirulent and nine virulent strains of B. glumae native to the southern United States were characterized in terms of virulence in rice and onion, toxofalvin production, antifungal activity, pigmentation and genomic structure. Virulence of B. glumae strains on rice panicles was highly correlated to virulence on onion bulb scales, suggesting that onion bulb can be a convenient alternative host system to efficiently determine the virulence of B. glumae strains. Production of toxoflavin, the phytotoxin that functions as a major virulence factor, was closely associated with the virulence phenotypes of B. glumae strains in rice. Some strains of B. glumae showed various levels of antifungal activity against Rhizoctonia solani, the causal agent of sheath blight, and pigmentation phenotypes on casamino acid-peptone-glucose (CPG) agar plates regardless of their virulence traits. Purple and yellow-green pigments were partially purified from a pigmenting strain of B. glumae, 411gr-6, and the purple pigment fraction showed a strong antifungal activity against Collectotrichum orbiculare. Genetic variations were detected among the B. glumae strains from DNA fingerprinting analyses by repetitive element sequence-based PCR (rep-PCR) for BOX-A1R-based repetitive extragenic palindromic (BOX) or enterobacterial repetitive intergenic consensus (ERIC) sequences of bacteria; and close genetic relatedness among virulent but pigment-deficient strains were revealed by clustering analyses of DNA fingerprints from BOX-and ERIC-PCR.

Life history trade-offs and relaxed selection can decrease bacterial virulence in environmental reservoirs.

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Lauri Mikonranta

Full Text Available Pathogen virulence is usually thought to evolve in reciprocal selection with the host. While this might be true for obligate pathogens, the life histories of opportunistic pathogens typically alternate between within-host and outside-host environments during the infection-transmission cycle. As a result, opportunistic pathogens are likely to experience conflicting selection pressures across different environments, and this could affect their virulence through life-history trait correlations. We studied these correlations experimentally by exposing an opportunistic bacterial pathogen Serratia marcescens to its natural protist predator Tetrahymena thermophila for 13 weeks, after which we measured changes in bacterial traits related to both anti-predator defence and virulence. We found that anti-predator adaptation (producing predator-resistant biofilm caused a correlative attenuation in virulence. Even though the direct mechanism was not found, reduction in virulence was most clearly connected to a predator-driven loss of a red bacterial pigment, prodigiosin. Moreover, life-history trait evolution was more divergent among replicate populations in the absence of predation, leading also to lowered virulence in some of the 'predator absent' selection lines. Together these findings suggest that the virulence of non-obligatory, opportunistic bacterial pathogens can decrease in environmental reservoirs through life history trade-offs, or random accumulation of mutations that impair virulence traits under relaxed selection.

Evaluating virulence of waterborne and clinical Aeromonas isolates using gene expression and mortality in neonatal mice followed by assessing cell culture’s ability to predict virulence based on transcriptional response

Energy Technology Data Exchange (ETDEWEB)

Hayes, S L; Rodgers, M R; Lye, D J; Stelma, G N; McKinstry, Craig A.; Malard, Joel M.; Vesper, Sephen J.

2007-10-01

Aims: To assess the virulence of Aeromonas spp. using two models, a neonatal mouse assay and a mouse intestinal cell culture. Methods and Results: After artificial infection with a variety of Aeromonas spp., mRNA extracts from the two models were processed and hydridized to murine microarrays to determine host gene response. Definition of virulence was determined based on host mRNA production in murine neonatal intestinal tissue and mortality of infected animals. Infections of mouse intestinal cell cultures were then performed to determine whether this simpler model system’s mRNA responses correlated to neonatal results and therefore be predictive of virulence of Aeromonas spp. Virulent aeromonads up-regulated transcripts in both models including multiple host defense gene products (chemokines, regulation of transcription and apoptosis and cell signalling). Avirulent species exhibited little or no host response in neonates. Mortality results correlated well with both bacterial dose and average fold change of up-regulated transcripts in the neonatal mice. Conclusions: Cell culture results were less discriminating but showed promise as potentially being able to be predictive of virulence. Jun oncogene up-regulation in murine cell culture is potentially predictive of Aeromonas virulence. Significance and Impact of the Study: Having the ability to determine virulence of waterborne pathogens quickly would potentially assist public health officials to rapidly assess exposure risks.

Haemophilus ducreyi Hfq contributes to virulence gene regulation as cells enter stationary phase.

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Gangaiah, Dharanesh; Labandeira-Rey, Maria; Zhang, Xinjun; Fortney, Kate R; Ellinger, Sheila; Zwickl, Beth; Baker, Beth; Liu, Yunlong; Janowicz, Diane M; Katz, Barry P; Brautigam, Chad A; Munson, Robert S; Hansen, Eric J; Spinola, Stanley M

2014-02-11

To adapt to stresses encountered in stationary phase, Gram-negative bacteria utilize the alternative sigma factor RpoS. However, some species lack RpoS; thus, it is unclear how stationary-phase adaptation is regulated in these organisms. Here we defined the growth-phase-dependent transcriptomes of Haemophilus ducreyi, which lacks an RpoS homolog. Compared to mid-log-phase organisms, cells harvested from the stationary phase upregulated genes encoding several virulence determinants and a homolog of hfq. Insertional inactivation of hfq altered the expression of ~16% of the H. ducreyi genes. Importantly, there were a significant overlap and an inverse correlation in the transcript levels of genes differentially expressed in the hfq inactivation mutant relative to its parent and the genes differentially expressed in stationary phase relative to mid-log phase in the parent. Inactivation of hfq downregulated genes in the flp-tad and lspB-lspA2 operons, which encode several virulence determinants. To comply with FDA guidelines for human inoculation experiments, an unmarked hfq deletion mutant was constructed and was fully attenuated for virulence in humans. Inactivation or deletion of hfq downregulated Flp1 and impaired the ability of H. ducreyi to form microcolonies, downregulated DsrA and rendered H. ducreyi serum susceptible, and downregulated LspB and LspA2, which allow H. ducreyi to resist phagocytosis. We propose that, in the absence of an RpoS homolog, Hfq serves as a major contributor of H. ducreyi stationary-phase and virulence gene regulation. The contribution of Hfq to stationary-phase gene regulation may have broad implications for other organisms that lack an RpoS homolog. Pathogenic bacteria encounter a wide range of stresses in their hosts, including nutrient limitation; the ability to sense and respond to such stresses is crucial for bacterial pathogens to successfully establish an infection. Gram-negative bacteria frequently utilize the alternative sigma

cipC is important for Aspergillus fumigatus virulence.

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Canela, Heliara Maria Spina; Takami, Luciano Akira; da Silva Ferreira, Márcia Eliana

2017-02-01

Aspergillus fumigatus is the main causative agent of invasive aspergillosis, a disease that affects immunocompromised patients and has a high mortality rate. We previously observed that the transcription of a cipC-like gene was increased when A. fumigatus encountered an increased CO 2 concentration, as occurs during the infection process. CipC is a protein of unknown function that might be associated with fungal pathogenicity. In this study, the cipC gene was disrupted in A. fumigatus to evaluate its importance for fungal pathogenicity. The gene was replaced, and the germination, growth phenotype, stress responses, and virulence of the resultant mutant were assessed. Although cipC was not essential, its deletion attenuated A. fumigatus virulence in a low-dose murine infection model, suggesting the involvement of the cipC gene in the virulence of this fungus. This study is the first to disrupt the cipC gene in A. fumigatus. © 2017 APMIS. Published by John Wiley & Sons Ltd.

Cell Density Control of Staphylococcal Virulence Mediated by an Octapeptide Pheromone

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Ji, Guangyong; Beavis, Ronald C.; Novick, Richard P.

1995-12-01

Some bacterial pathogens elaborate and secrete virulence factors in response to environmental signals, others in response to a specific host product, and still others in response to no discernible cue. In this study, we have demonstrated that the synthesis of Staphylococcus aureus virulence factors is controlled by a density-sensing system that utilizes an octapeptide produced by the organism itself. The octapeptide activates expression of the agr locus, a global regulator of the virulence response. This response involves the reciprocal regulation of genes encoding surface proteins and those encoding secreted virulence factors. As cells enter the postexponential phase, surface protein genes are repressed by agr and secretory protein genes are subsequently activated. The intracellular agr effector is a regulatory RNA, RNAIII, whose transcription is activated by an agr-encoded signal transduction system for which the octapeptide is the ligand.

Low virulent oral Candida albicans strains isolated from smokers.

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de Azevedo Izidoro, Ana Claudia Santos; Semprebom, Andressa Marafon; Baboni, Fernanda Brasil; Rosa, Rosimeire Takaki; Machado, Maria Angela Naval; Samaranayake, Lakshman Perera; Rosa, Edvaldo Antonio Ribeiro

2012-02-01

It is widely accepted that tabagism is a predisposing factor to oral candidosis and cumulate data suggest that cigarette compounds may increase candidal virulence. To verify if enhanced virulence occurs in Candida albicans from chronic smokers, a cohort of 42 non-smokers and other of 58 smokers (all with excellent oral conditions and without signs of candidosis) were swabbed on tong dorsum and jugal mucosa. Results showed that oral candidal loads do not differ between smoker and non-smokers. Activities of secreted aspartyl-protease (Sap), phospholipase, chondroitinase, esterase-lipase, and haemolysin secretions were screened for thirty-two C. albicans isolates. There were detected significant increments in phospholipasic and chondroitinasic activities in isolates from non-smokers. For other virulence factors, no differences between both cohorts were achieved. Copyright © 2011 Elsevier Ltd. All rights reserved.

Virulence Factors and Antibiotic Susceptibility of Staphylococcus aureus Isolates in Ready-to-Eat Foods: Detection of S. aureus Contamination and a High Prevalence of Virulence Genes

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Suat Moi Puah

2016-02-01

Full Text Available Staphylococcus aureus is one of the leading causes of food poisoning. Its pathogenicity results from the possession of virulence genes that produce different toxins which result in self-limiting to severe illness often requiring hospitalization. In this study of 200 sushi and sashimi samples, S. aureus contamination was confirmed in 26% of the food samples. The S. aureus isolates were further characterized for virulence genes and antibiotic susceptibility. A high incidence of virulence genes was identified in 96.2% of the isolates and 20 different virulence gene profiles were confirmed. DNA amplification showed that 30.8% (16/52 of the S. aureus carried at least one SE gene which causes staphylococcal food poisoning. The most common enterotoxin gene was seg (11.5% and the egc cluster was detected in 5.8% of the isolates. A combination of hla and hld was the most prevalent coexistence virulence genes and accounted for 59.6% of all isolates. Antibiotic resistance studies showed tetracycline resistance to be the most common at 28.8% while multi-drug resistance was found to be low at 3.8%. In conclusion, the high rate of S. aureus in the sampled sushi and sashimi indicates the need for food safety guidelines.

Virulence of a Klebsiella pneumoniae strain carrying the New Delhi metallo-beta-lactamase-1 (NDM-1)

DEFF Research Database (Denmark)

Fuursted, Kurt; Schøler, Lone; Hansen, Frank

2011-01-01

, and in vitro virulence by assessing various virulence factors. The NDM-1 carrying K. pneumoniae isolate was the most virulent in the murine sepsis model but there was no clear cut correlation to in vitro virulence factors or killing in C. elegans. It is concluded that K. pneumoniae carrying NDM-1 have......The aim of the study was to compare and evaluate virulence in five strains of Klebsiella pneumoniae, including an isolate carrying New Delhi metallo-beta-lactamase-1 (NDM-1). In vivo virulence was assessed using a murine sepsis model and using the nematode Caenorhabditis elegans killing model...

How Do the Virulence Factors of Shigella Work Together to Cause Disease?

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Mattock, Emily; Blocker, Ariel J

2017-01-01

Shigella is the major cause of bacillary dysentery world-wide. It is divided into four species, named S. flexneri, S. sonnei, S. dysenteriae , and S. boydii , which are distinct genomically and in their ability to cause disease. Shigellosis, the clinical presentation of Shigella infection, is characterized by watery diarrhea, abdominal cramps, and fever. Shigella 's ability to cause disease has been attributed to virulence factors, which are encoded on chromosomal pathogenicity islands and the virulence plasmid. However, information on these virulence factors is not often brought together to create a detailed picture of infection, and how this translates into shigellosis symptoms. Firstly, Shigella secretes virulence factors that induce severe inflammation and mediate enterotoxic effects on the colon, producing the classic watery diarrhea seen early in infection. Secondly, Shigella injects virulence effectors into epithelial cells via its Type III Secretion System to subvert the host cell structure and function. This allows invasion of epithelial cells, establishing a replicative niche, and causes erratic destruction of the colonic epithelium. Thirdly, Shigella produces effectors to down-regulate inflammation and the innate immune response. This promotes infection and limits the adaptive immune response, causing the host to remain partially susceptible to re-infection. Combinations of these virulence factors may contribute to the different symptoms and infection capabilities of the diverse Shigella species, in addition to distinct transmission patterns. Further investigation of the dominant species causing disease, using whole-genome sequencing and genotyping, will allow comparison and identification of crucial virulence factors and may contribute to the production of a pan- Shigella vaccine.

Restriction Fragment Length Polymorphisms of Virulence Plasmids in Rhodococcus equi

Science.gov (United States)

Takai, Shinji; Shoda, Masato; Sasaki, Yukako; Tsubaki, Shiro; Fortier, Guillaume; Pronost, Stephane; Rahal, Karim; Becu, Teotimo; Begg, Angela; Browning, Glenn; Nicholson, Vivian M.; Prescott, John F.

1999-01-01

Virulent Rhodococcus equi, which is a well-known cause of pyogranulomatous pneumonia in foals, possesses a large plasmid encoding virulence-associated 15- to 17-kDa antigens. Foal and soil isolates from five countries—Argentina, Australia, Canada, France, and Japan—were investigated for the presence of 15- to 17-kDa antigens by colony blotting, using the monoclonal antibody 10G5, and the gene coding for 15- to 17-kDa antigens by PCR. Plasmid DNAs extracted from positive isolates were digested with restriction endonucleases BamHI, EcoRI, EcoT22I, and HindIII, and the digestion patterns that resulted divided the plasmids of virulent isolates into five closely related types. Three of the five types had already been reported in Canadian and Japanese isolates, and the two new types had been found in French and Japanese isolates. Therefore, we tentatively designated these five types 85-kb type I (pREAT701), 85-kb type II (a new type), 87-kb type I (EcoRI and BamHI type 2 [V. M. Nicholson and J. F. Prescott, J. Clin. Microbiol. 35:738–740, 1997]), 87-kb type II (a new type), and 90-kb (pREL1) plasmids. The 85-kb type I plasmid was found in isolates from Argentina, Australia, Canada, and France. Plasmid 87-kb type I was isolated in specimens from Argentina, Canada, and France. The 85-kb type II plasmid appeared in isolates from France. On the other hand, plasmids 87-kb type II and 90-kb were found only in isolates from Japan. These results revealed geographic differences in the distribution of the virulence plasmids found in the five countries and suggested that the restriction fragment length polymorphism of virulence plasmids might be useful to elucidate the molecular epidemiology of virulent R. equi in the world. PMID:10488224

Staphylococcus aureus Isolates from Bovine Mastitis in Eight Countries: Genotypes, Detection of Genes Encoding Different Toxins and Other Virulence Genes

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Valentina Monistero

2018-06-01

Full Text Available Staphylococcus aureus is recognized worldwide as one of the major agents of dairy cow intra-mammary infections. This microorganism can express a wide spectrum of pathogenic factors used to attach, colonize, invade and infect the host. The present study evaluated 120 isolates from eight different countries that were genotyped by RS-PCR and investigated for 26 different virulence factors to increase the knowledge on the circulating genetic lineages among the cow population with mastitis. New genotypes were observed for South African strains while for all the other countries new variants of existing genotypes were detected. For each country, a specific genotypic pattern was found. Among the virulence factors, fmtB, cna, clfA and leucocidins genes were the most frequent. The sea and sei genes were present in seven out of eight countries; seh showed high frequency in South American countries (Brazil, Colombia, Argentina, while sel was harboured especially in one Mediterranean country (Tunisia. The etb, seb and see genes were not detected in any of the isolates, while only two isolates were MRSA (Germany and Italy confirming the low diffusion of methicillin resistance microorganism among bovine mastitis isolates. This work demonstrated the wide variety of S. aureus genotypes found in dairy cattle worldwide. This condition suggests that considering the region of interest might help to formulate strategies for reducing the infection spreading.

Ongoing Horizontal and Vertical Transmission of Virulence Genes and papA Alleles among Escherichia coli Blood Isolates from Patients with Diverse-Source Bacteremia

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Johnson, James R.; O'Bryan, Timothy T.; Kuskowski, Michael; Maslow, Joel N.

2001-01-01

The phylogenetic distributions of multiple putative virulence factors (VFs) and papA (P fimbrial structural subunit) alleles among 182 Escherichia coli blood isolates from patients with diverse-source bacteremia were defined. Phylogenetic correspondence among these strains, the E. coli Reference (ECOR) collection, and other collections of extraintestinal pathogenic E. coli (ExPEC) was assessed. Although among the 182 bacteremia isolates phylogenetic group B2 predominated, exhibited the greatest concentration of individual VFs, and contained the largest number of familiar virulent clones, other phylogenetic groups exhibited greater concentrations of certain VFs than did group B2 and included several additional virulent clones. Certain of the newly detected VF genes, e.g., fyuA (yersiniabactin; 76%) and focG (F1C fimbriae; 25%), were as prevalent or more prevalent than their more familiar traditional counterparts, e.g., iut (aerobactin; 57%) and sfaS (S fimbriae; 14%), thus possibly offering additional useful targets for preventive interventions. Considerable diversity of VF profiles was observed at every level within the phylogenetic tree, including even within individual lineages. This suggested that many different pathways can lead to extraintestinal virulence in E. coli and that the evolution of ExPEC, which involves extensive horizontal transmission of VFs and continuous remodeling of pathogenicity-associated islands, is a highly active, ongoing process. PMID:11500406

Modeling disease risk through analysis of physical interactions between genetic variants within chromatin regulatory circuitry.

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Corradin, Olivia; Cohen, Andrea J; Luppino, Jennifer M; Bayles, Ian M; Schumacher, Fredrick R; Scacheri, Peter C

2016-11-01

SNPs associated with disease susceptibility often reside in enhancer clusters, or super-enhancers. Constituents of these enhancer clusters cooperate to regulate target genes and often extend beyond the linkage disequilibrium (LD) blocks containing risk SNPs identified in genome-wide association studies (GWAS). We identified 'outside variants', defined as SNPs in weak LD with GWAS risk SNPs that physically interact with risk SNPs as part of a target gene's regulatory circuitry. These outside variants further explain variation in target gene expression beyond that explained by GWAS-associated SNPs. Additionally, the clinical risk associated with GWAS SNPs is considerably modified by the genotype of outside variants. Collectively, these findings suggest a potential model in which outside variants and GWAS SNPs that physically interact in 3D chromatin collude to influence target transcript levels as well as clinical risk. This model offers an additional hypothesis for the source of missing heritability for complex traits.

Virulence of Xanthomonas translucens pv. poae Isolated from Poa annua

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Arielle Chaves

2013-03-01

Full Text Available Bacterial wilt is a vascular wilt disease caused by Xanthomonas translucens pv. poae that infects Poa annua, a grass that is commonly found on golf course greens throughout the world. Bacterial wilt causes symptoms of etiolation, wilting, and foliar necrosis. The damage is most prevalent during the summer and the pathogen can kill turf under conditions optimal for disease development. Fifteen isolates of X. translucens pv. poae were collected from northern regions in the United States and tested for virulence against P. annua. All 15 isolates were pathogenic on P. annua, but demonstrated variable levels of virulence when inoculated onto P. annua under greenhouse conditions. The isolates were divided into two virulence groups. The first group containing four isolates generally resulted in less than 40% mortality following inoculation. The second group, containing the other eleven isolates, produced between 90 and 100% mortality following inoculation. These results suggest that differences in the virulence of bacterial populations present on a golf course may result in more or less severe amounts of observed disease.

Brucella, nitrogen and virulence.

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Ronneau, Severin; Moussa, Simon; Barbier, Thibault; Conde-Álvarez, Raquel; Zuniga-Ripa, Amaia; Moriyon, Ignacio; Letesson, Jean-Jacques

2016-08-01

The brucellae are α-Proteobacteria causing brucellosis, an important zoonosis. Although multiplying in endoplasmic reticulum-derived vacuoles, they cause no cell death, suggesting subtle but efficient use of host resources. Brucellae are amino-acid prototrophs able to grow with ammonium or use glutamate as the sole carbon-nitrogen source in vitro. They contain more than twice amino acid/peptide/polyamine uptake genes than the amino-acid auxotroph Legionella pneumophila, which multiplies in a similar vacuole, suggesting a different nutritional strategy. During these two last decades, many mutants of key actors in nitrogen metabolism (transporters, enzymes, regulators, etc.) have been described to be essential for full virulence of brucellae. Here, we review the genomic and experimental data on Brucella nitrogen metabolism and its connection with virulence. An analysis of various aspects of this metabolism (transport, assimilation, biosynthesis, catabolism, respiration and regulation) has highlighted differences and similarities in nitrogen metabolism with other α-Proteobacteria. Together, these data suggest that, during their intracellular life cycle, the brucellae use various nitrogen sources for biosynthesis, catabolism and respiration following a strategy that requires prototrophy and a tight regulation of nitrogen use.

Riboregulators: Fine-Tuning Virulence in Shigella.

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Fris, Megan E; Murphy, Erin R

2016-01-01

Within the past several years, RNA-mediated regulation (ribo-regulation) has become increasingly recognized for its importance in controlling critical bacterial processes. Regulatory RNA molecules, or riboregulators, are perpetually responsive to changes within the micro-environment of a bacterium. Notably, several characterized riboregulators control virulence in pathogenic bacteria, as is the case for each riboregulator characterized to date in Shigella. The timing of virulence gene expression and the ability of the pathogen to adapt to rapidly changing environmental conditions is critical to the establishment and progression of infection by Shigella species; ribo-regulators mediate each of these important processes. This mini review will present the current state of knowledge regarding RNA-mediated regulation in Shigella by detailing the characterization and function of each identified riboregulator in these pathogens.

Harbouring public good mutants within a pathogen population can increase both fitness and virulence.

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Lindsay, Richard J; Kershaw, Michael J; Pawlowska, Bogna J; Talbot, Nicholas J; Gudelj, Ivana

2016-12-28

Existing theory, empirical, clinical and field research all predict that reducing the virulence of individuals within a pathogen population will reduce the overall virulence, rendering disease less severe. Here, we show that this seemingly successful disease management strategy can fail with devastating consequences for infected hosts. We deploy cooperation theory and a novel synthetic system involving the rice blast fungus Magnaporthe oryzae . In vivo infections of rice demonstrate that M. oryzae virulence is enhanced, quite paradoxically, when a public good mutant is present in a population of high-virulence pathogens. We reason that during infection, the fungus engages in multiple cooperative acts to exploit host resources. We establish a multi-trait cooperation model which suggests that the observed failure of the virulence reduction strategy is caused by the interference between different social traits. Multi-trait cooperative interactions are widespread, so we caution against the indiscriminant application of anti-virulence therapy as a disease-management strategy.

CRISPR interference can prevent natural transformation and virulence acquisition during in vivo bacterial infection.

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Bikard, David; Hatoum-Aslan, Asma; Mucida, Daniel; Marraffini, Luciano A

2012-08-16

Pathogenic bacterial strains emerge largely due to transfer of virulence and antimicrobial resistance genes between bacteria, a process known as horizontal gene transfer (HGT). Clustered, regularly interspaced, short palindromic repeat (CRISPR) loci of bacteria and archaea encode a sequence-specific defense mechanism against bacteriophages and constitute a programmable barrier to HGT. However, the impact of CRISPRs on the emergence of virulence is unknown. We programmed the human pathogen Streptococcus pneumoniae with CRISPR sequences that target capsule genes, an essential pneumococcal virulence factor, and show that CRISPR interference can prevent transformation of nonencapsulated, avirulent pneumococci into capsulated, virulent strains during infection in mice. Further, at low frequencies bacteria can lose CRISPR function, acquire capsule genes, and mount a successful infection. These results demonstrate that CRISPR interference can prevent the emergence of virulence in vivo and that strong selective pressure for virulence or antibiotic resistance can lead to CRISPR loss in bacterial pathogens. Copyright © 2012 Elsevier Inc. All rights reserved.

Pathogenomic inference of virulence-associated genes in Leptospira interrogans.

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Lehmann, Jason S; Fouts, Derrick E; Haft, Daniel H; Cannella, Anthony P; Ricaldi, Jessica N; Brinkac, Lauren; Harkins, Derek; Durkin, Scott; Sanka, Ravi; Sutton, Granger; Moreno, Angelo; Vinetz, Joseph M; Matthias, Michael A

2013-01-01

Leptospirosis is a globally important, neglected zoonotic infection caused by spirochetes of the genus Leptospira. Since genetic transformation remains technically limited for pathogenic Leptospira, a systems biology pathogenomic approach was used to infer leptospiral virulence genes by whole genome comparison of culture-attenuated Leptospira interrogans serovar Lai with its virulent, isogenic parent. Among the 11 pathogen-specific protein-coding genes in which non-synonymous mutations were found, a putative soluble adenylate cyclase with host cell cAMP-elevating activity, and two members of a previously unstudied ∼15 member paralogous gene family of unknown function were identified. This gene family was also uniquely found in the alpha-proteobacteria Bartonella bacilliformis and Bartonella australis that are geographically restricted to the Andes and Australia, respectively. How the pathogenic Leptospira and these two Bartonella species came to share this expanded gene family remains an evolutionary mystery. In vivo expression analyses demonstrated up-regulation of 10/11 Leptospira genes identified in the attenuation screen, and profound in vivo, tissue-specific up-regulation by members of the paralogous gene family, suggesting a direct role in virulence and host-pathogen interactions. The pathogenomic experimental design here is generalizable as a functional systems biology approach to studying bacterial pathogenesis and virulence and should encourage similar experimental studies of other pathogens.

Virulence determinants of Moraxella catarrhalis: distribution and considerations for vaccine development.

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Blakeway, Luke V; Tan, Aimee; Peak, Ian R A; Seib, Kate L

2017-10-01

Moraxella catarrhalis is a human-restricted opportunistic bacterial pathogen of the respiratory mucosa. It frequently colonizes the nasopharynx asymptomatically, but is also an important causative agent of otitis media (OM) in children, and plays a significant role in acute exacerbations of chronic obstructive pulmonary disease (COPD) in adults. As the current treatment options for M. catarrhalis infection in OM and exacerbations of COPD are often ineffective, the development of an efficacious vaccine is warranted. However, no vaccine candidates for M. catarrhalis have progressed to clinical trials, and information regarding the distribution of M. catarrhalis virulence factors and vaccine candidates is inconsistent in the literature. It is largely unknown if virulence is associated with particular strains or subpopulations of M. catarrhalis, or if differences in clinical manifestation can be attributed to the heterogeneous expression of specific M. catarrhalis virulence factors in the circulating population. Further investigation of the distribution of M. catarrhalis virulence factors in the context of carriage and disease is required so that vaccine development may be targeted at relevant antigens that are conserved among disease-causing strains. The challenge of determining which of the proposed M. catarrhalis virulence factors are relevant to human disease is amplified by the lack of a standardized M. catarrhalis typing system to facilitate direct comparisons of worldwide isolates. Here we summarize and evaluate proposed relationships between M. catarrhalis subpopulations and specific virulence factors in the context of colonization and disease, as well as the current methods used to infer these associations.

Frequency of virulence factors in Helicobacter pylori-infected patients with gastritis.

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Salimzadeh, Loghman; Bagheri, Nader; Zamanzad, Behnam; Azadegan-Dehkordi, Fatemeh; Rahimian, Ghorbanali; Hashemzadeh-Chaleshtori, Morteza; Rafieian-Kopaei, Mahmoud; Sanei, Mohammad Hossein; Shirzad, Hedayatollah

2015-03-01

The outcome of Helicobacter pylori infection has been related to specific virulence-associated bacterial genotypes. The vacuolating cytotoxin (vacA), cagA gene, oipA and babA2 gene are important virulence factor involving gastric diseases. The objective of this study was to assess the relationship between virulence factors of H. pylori and histopathological findings. Gastroduodenoscopy was performed in 436 dyspeptic patients. Antrum biopsy was obtained for detection of H. pylori, virulence factors and for histopathological assessment. The polymerase chain reaction was used to detect virulence factors of H. pylori using specific primers. vacA genotypes in patients infected with H. pylori were associated with cagA, iceA1 and iceA2. In the patients with H. pylori infection there was a significant relationship between cagA positivity and neutrophil activity (P = 0.004) and chronic inflammation (P = 0.013) and with H. pylori density (P = 0.034). Neutrophil infiltration was found to be more severe in the s1 group than in the s2 group (P = 0.042). Also was a significant relationship between oipA positivity and neutrophil activity (P = 0.004) and with H. pylori density (P = 0.018). No significant relationships were observed between other vacA genotypes and histopathological parameters. H. pylori strains showing cagA, vacA s1 and oipA positivity are associated with more severe gastritis in some histological features but virulence factors of H. pylori do not appear to determine the overall pattern of gastritis. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evolution of Salmonella enterica virulence via point mutations in the fimbrial adhesin.

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Dagmara I Kisiela

Full Text Available Whereas the majority of pathogenic Salmonella serovars are capable of infecting many different animal species, typically producing a self-limited gastroenteritis, serovars with narrow host-specificity exhibit increased virulence and their infections frequently result in fatal systemic diseases. In our study, a genetic and functional analysis of the mannose-specific type 1 fimbrial adhesin FimH from a variety of serovars of Salmonella enterica revealed that specific mutant variants of FimH are common in host-adapted (systemically invasive serovars. We have found that while the low-binding shear-dependent phenotype of the adhesin is preserved in broad host-range (usually systemically non-invasive Salmonella, the majority of host-adapted serovars express FimH variants with one of two alternative phenotypes: a significantly increased binding to mannose (as in S. Typhi, S. Paratyphi C, S. Dublin and some isolates of S. Choleraesuis, or complete loss of the mannose-binding activity (as in S. Paratyphi B, S. Choleraesuis and S. Gallinarum. The functional diversification of FimH in host-adapted Salmonella results from recently acquired structural mutations. Many of the mutations are of a convergent nature indicative of strong positive selection. The high-binding phenotype of FimH that leads to increased bacterial adhesiveness to and invasiveness of epithelial cells and macrophages usually precedes acquisition of the non-binding phenotype. Collectively these observations suggest that activation or inactivation of mannose-specific adhesive properties in different systemically invasive serovars of Salmonella reflects their dynamic trajectories of adaptation to a life style in specific hosts. In conclusion, our study demonstrates that point mutations are the target of positive selection and, in addition to horizontal gene transfer and genome degradation events, can contribute to the differential pathoadaptive evolution of Salmonella.

Maternal inheritance and mitochondrial DNA variants in familial Parkinson's disease

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Pfeiffer Ronald F

2010-04-01

Full Text Available Abstract Background Mitochondrial function is impaired in Parkinson's disease (PD and may contribute to the pathogenesis of PD, but the causes of mitochondrial impairment in PD are unknown. Mitochondrial dysfunction is recapitulated in cell lines expressing mitochondrial DNA (mtDNA from PD patients, implicating mtDNA variants or mutations, though the role of mtDNA variants or mutations in PD risk remains unclear. We investigated the potential contribution of mtDNA variants or mutations to the risk of PD. Methods We examined the possibility of a maternal inheritance bias as well as the association between mitochondrial haplogroups and maternal inheritance and disease risk in a case-control study of 168 multiplex PD families in which the proband and one parent were diagnosed with PD. 2-tailed Fisher Exact Tests and McNemar's tests were used to compare allele frequencies, and a t-test to compare ages of onset. Results The frequency of affected mothers of the proband with PD (83/167, 49.4% was not significantly different from the frequency of affected females of the proband generation (115/259, 44.4% (Odds Ratio 1.22; 95%CI 0.83 - 1.81. After correcting for multiple tests, there were no significant differences in the frequencies of mitochondrial haplogroups or of the 10398G complex I gene polymorphism in PD patients compared to controls, and no significant associations with age of onset of PD. Mitochondrial haplogroup and 10398G polymorphism frequencies were similar in probands having an affected father as compared to probands having an affected mother. Conclusions These data fail to demonstrate a bias towards maternal inheritance in familial PD. Consistent with this, we find no association of common haplogroup-defining mtDNA variants or for the 10398G variant with the risk of PD. However, these data do not exclude a role for mtDNA variants in other populations, and it remains possible that other inherited mitochondrial DNA variants, or somatic m

Long-distance delivery of bacterial virulence factors by Pseudomonas aeruginosa outer membrane vesicles.

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Jennifer M Bomberger

2009-04-01

Full Text Available Bacteria use a variety of secreted virulence factors to manipulate host cells, thereby causing significant morbidity and mortality. We report a mechanism for the long-distance delivery of multiple bacterial virulence factors, simultaneously and directly into the host cell cytoplasm, thus obviating the need for direct interaction of the pathogen with the host cell to cause cytotoxicity. We show that outer membrane-derived vesicles (OMV secreted by the opportunistic human pathogen Pseudomonas aeruginosa deliver multiple virulence factors, including beta-lactamase, alkaline phosphatase, hemolytic phospholipase C, and Cif, directly into the host cytoplasm via fusion of OMV with lipid rafts in the host plasma membrane. These virulence factors enter the cytoplasm of the host cell via N-WASP-mediated actin trafficking, where they rapidly distribute to specific subcellular locations to affect host cell biology. We propose that secreted virulence factors are not released individually as naked proteins into the surrounding milieu where they may randomly contact the surface of the host cell, but instead bacterial derived OMV deliver multiple virulence factors simultaneously and directly into the host cell cytoplasm in a coordinated manner.

The link between morphotype transition and virulence in Cryptococcus neoformans.

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Linqi Wang

Full Text Available Cryptococcus neoformans is a ubiquitous human fungal pathogen. This pathogen can undergo morphotype transition between the yeast and the filamentous form and such morphological transition has been implicated in virulence for decades. Morphotype transition is typically observed during mating, which is governed by pheromone signaling. Paradoxically, components specific to the pheromone signaling pathways play no or minimal direct roles in virulence. Thus, the link between morphotype transition and virulence and the underlying molecular mechanism remain elusive. Here, we demonstrate that filamentation can occur independent of pheromone signaling and mating, and both mating-dependent and mating-independent morphotype transition require the transcription factor Znf2. High expression of Znf2 is necessary and sufficient to initiate and maintain sex-independent filamentous growth under host-relevant conditions in vitro and during infection. Importantly, ZNF2 overexpression abolishes fungal virulence in murine models of cryptococcosis. Thus, Znf2 bridges the sex-independent morphotype transition and fungal pathogenicity. The impacts of Znf2 on morphological switch and pathogenicity are at least partly mediated through its effects on cell adhesion property. Cfl1, a Znf2 downstream factor, regulates morphogenesis, cell adhesion, biofilm formation, and virulence. Cfl1 is the first adhesin discovered in the phylum Basidiomycota of the Kingdom Fungi. Together with previous findings in other eukaryotic pathogens, our findings support a convergent evolution of plasticity in morphology and its impact on cell adhesion as a critical adaptive trait for pathogenesis.

The Role of TonB Gene in Edwardsiella ictaluri Virulence

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Hossam Abdelhamed

2017-12-01

Full Text Available Edwardsiella ictaluri is a Gram-negative facultative intracellular pathogen that causes enteric septicemia in catfish (ESC. Stress factors including poor water quality, poor diet, rough handling, overcrowding, and water temperature fluctuations increase fish susceptibility to ESC. The TonB energy transducing system (TonB-ExbB-ExbD and TonB-dependent transporters of Gram-negative bacteria support active transport of scarce resources including iron, an essential micronutrient for bacterial virulence. Deletion of the tonB gene attenuates virulence in several pathogenic bacteria. In the current study, the role of TonB (NT01EI_RS07425 in iron acquisition and E. ictaluri virulence were investigated. To accomplish this, the E. ictaluri tonB gene was in-frame deleted. Growth kinetics, iron utilization, and virulence of the EiΔtonB mutant were determined. Loss of TonB caused a significant reduction in bacterial growth in iron-depleted medium (p > 0.05. The EiΔtonB mutant grew similarly to wild-type E. ictaluri when ferric iron was added to the iron-depleted medium. The EiΔtonB mutant was significantly attenuated in catfish compared with the parent strain (21.69 vs. 46.91% mortality. Catfish surviving infection with EiΔtonB had significant protection against ESC compared with naïve fish (100 vs. 40.47% survival. These findings indicate that TonB participates in pathogenesis of ESC and is an important E. ictaluri virulence factor.

Impact of type 2 diabetes susceptibility variants on quantitative glycemic traits reveals mechanistic heterogeneity

DEFF Research Database (Denmark)

Dimas, Antigone S; Lagou, Vasiliki; Barker, Adam

2013-01-01

Patients with established type 2 diabetes display both beta-cell dysfunction and insulin resistance. To define fundamental processes leading to the diabetic state, we examined the relationship between type 2 diabetes risk variants at 37 established susceptibility loci and indices of proinsulin pr...

The flagellar master operon flhDC is a pleiotropic regulator involved in motility and virulence of the fish pathogen Yersinia ruckeri.

Science.gov (United States)

Jozwick, A K S; Graf, J; Welch, T J

2017-03-01

To investigate the function of the master flagellar operon flhDC in the fish pathogen Yersinia ruckeri and compare the effect of a constructed flhD mutation to a naturally occurring fliR mutation causing loss-of-motility in emergent biotype 2 (BT2) strains. Yersinia ruckeri flhD and fliR mutants were constructed in a motile strain. Both mutations caused loss-of-motility, ablation of flagellin synthesis and phospholipase secretion, similar to naturally occurring BT2 strains. Transcriptome analysis confirmed flhDC regulation of flagellar, chemotaxis and phospholipase loci as well as other genes of diverse function. The flhD mutation confers a competitive advantage within the fish host when compared with its parent strain, while this advantage was not seen with the naturally occurring fliR mutation. An intact flhD is necessary for expression of the flagellar secretion system as well as other diverse loci, consistent with a role for flhD as a pleiotropic regulator. The maintenance of the flhD locus in Y. ruckeri strains suggests its importance for aspects of Y. ruckeri biology other than virulence, since the flhD mutation conferred a competitive advantage during experimental challenge of rainbow trout. Yersinia ruckeri is the causative agent of enteric red mouth disease, an invasive septicaemia that affects farmed salmonid fish species. Disease outbreaks can cause severe economic losses in aquaculture. BT2 variants, which have independently emerged worldwide, are an increasing threat to farmed fish production. Knowledge of mechanisms involved in virulence, conserved functions and gene regulation among strains may be exploited for the development of novel disease control strategies to prevent pathogen growth or virulence phenotypes within aquaculture. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Method for Screening Compounds That Influence Virulence Gene Expression in Staphylococcus aureus

DEFF Research Database (Denmark)

Nielsen, A.; Nielsen, Kristian Fog; Frees, D.

2010-01-01

We present a simple assay to examine effects of compounds on virulence gene expression in the human pathogen Staphylococcus aureus. The assay employs transcriptional reporter strains carrying lacZ fused to central virulence genes. Compounds affecting virulence gene expression and activity...... of the agr locus are scored based on color change in the presence of a chromogenic beta-galactosidase substrate. The assay can be used to screen for novel antivirulence compounds from many different sources, such as fungi, as demonstrated here....

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

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Mira Rakic Martinez

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

A comprehensive approach to identification of pathogenic FANCA variants in Fanconi anemia patients and their families.

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Kimble, Danielle C; Lach, Francis P; Gregg, Siobhan Q; Donovan, Frank X; Flynn, Elizabeth K; Kamat, Aparna; Young, Alice; Vemulapalli, Meghana; Thomas, James W; Mullikin, James C; Auerbach, Arleen D; Smogorzewska, Agata; Chandrasekharappa, Settara C

2018-02-01

Fanconi anemia (FA) is a rare recessive DNA repair deficiency resulting from mutations in one of at least 22 genes. Two-thirds of FA families harbor mutations in FANCA. To genotype patients in the International Fanconi Anemia Registry (IFAR) we employed multiple methodologies, screening 216 families for FANCA mutations. We describe identification of 57 large deletions and 261 sequence variants, in 159 families. All but seven families harbored distinct combinations of two mutations demonstrating high heterogeneity. Pathogenicity of the 18 novel missense variants was analyzed functionally by determining the ability of the mutant cDNA to improve the survival of a FANCA-null cell line when treated with MMC. Overexpressed pathogenic missense variants were found to reside in the cytoplasm, and nonpathogenic in the nucleus. RNA analysis demonstrated that two variants (c.522G > C and c.1565A > G), predicted to encode missense variants, which were determined to be nonpathogenic by a functional assay, caused skipping of exons 5 and 16, respectively, and are most likely pathogenic. We report 48 novel FANCA sequence variants. Defining both variants in a large patient cohort is a major step toward cataloging all FANCA variants, and permitting studies of genotype-phenotype correlations. © Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Virulence of geographically different Cryptosporidium parvum isolates in experimental animal model

Science.gov (United States)

Sayed, Fatma G.; Hamza, Amany I.; Galal, Lamia A.; Sayed, Douaa M.; Gaber, Mona

2016-10-01

Cryptosporidium parvum is a coccidian parasite which causes gastrointestinal disease in humans and a variety of other mammalian species. Several studies have reported different degrees of pathogenicity and virulence among Cryptosporidium species and isolates of the same species as well as evidence of variation in host susceptibility to infection. The study aimed to investigate infectivity and virulence of two Cryptosporidium parvum “Iowa isolate” (CpI) and a “local water isolate” (CpW). Thirty-three Swiss albino mice have been divided into three groups: Negative control Group (C), the CpI group infected with “Iowa isolate “and the CpW group infected with C. parvum oocysts isolated from a local water supply. Infectivity and virulence have been measured by evaluating clinical, parasitological and histological aspects of infection. Significant differences were detected regarding oocysts shedding rate, clinical outcomes, and the histopathological picture of the intestine, lung, and brain. It was concluded that the local water isolate is significantly more virulent than the exported one.

The worm has turned--microbial virulence modeled in Caenorhabditis elegans.

Science.gov (United States)

Sifri, Costi D; Begun, Jakob; Ausubel, Frederick M

2005-03-01

The nematode Caenorhabditis elegans is emerging as a facile and economical model host for the study of evolutionarily conserved mechanisms of microbial pathogenesis and innate immunity. A rapidly growing number of human and animal microbial pathogens have been shown to injure and kill nematodes. In many cases, microbial genes known to be important for full virulence in mammalian models have been shown to be similarly required for maximum pathogenicity in nematodes. C. elegans has been used in mutation-based screening systems to identify novel virulence-related microbial genes and immune-related host genes, many of which have been validated in mammalian models of disease. C. elegans-based pathogenesis systems hold the potential to simultaneously explore the molecular genetic determinants of both pathogen virulence and host defense.

Regulation of Yersina pestis Virulence by AI-2 Mediated Quorum Sensing

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Segelke, B; Hok, S; Lao, V; Corzett, M; Garcia, E

2010-03-29

The proposed research was motivated by an interest in understanding Y. pestis virulence mechanisms and bacteria cell-cell communication. It is expected that a greater understanding of virulence mechanisms will ultimately lead to biothreat countermeasures and novel therapeutics. Y. pestis is the etiological agent of plague, the most devastating disease in human history. Y. pestis infection has a high mortality rate and a short incubation before mortality. There is no widely available and effective vaccine for Y. pestis and multi-drug resistant strains are emerging. Y. pestis is a recognized biothreat agent based on the wide distribution of the bacteria in research laboratories around the world and on the knowledge that methods exist to produce and aerosolize large amounts of bacteria. We hypothesized that cell-cell communication via signaling molecules, or quorum sensing, by Y. pestis is important for the regulation of virulence factor gene expression during host invasion, though a causative link had never been established. Quorum sensing is a mode of intercellular communication which enables orchestration of gene expression for many bacteria as a function of population density and available evidence suggests there may be a link between quorum sensing and regulation of Y. pesits virulence. Several pathogenic bacteria have been shown to regulate expression of virulence factor genes, including genes encoding type III secretion, via quorum sensing. The Y. pestis genome encodes several cell-cell signaling pathways and the interaction of at least three of these are thought to be involved in one or more modes of host invasion. Furthermore, Y. pestis gene expression array studies carried out at LLNL have established a correlation between expression of known virulence factors and genes involved in processing of the AI-2 quorum sensing signal. This was a basic research project that was intended to provide new insights into bacterial intercellular communication and how it is

Genomic Structural Variations Affecting Virulence During Clonal Expansion of Pseudomonas syringae pv. actinidiae Biovar 3 in Europe.

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Firrao, Giuseppe; Torelli, Emanuela; Polano, Cesare; Ferrante, Patrizia; Ferrini, Francesca; Martini, Marta; Marcelletti, Simone; Scortichini, Marco; Ermacora, Paolo

2018-01-01

Pseudomonas syringae pv. actinidiae (Psa) biovar 3 caused pandemic bacterial canker of Actinidia chinensis and Actinidia deliciosa since 2008. In Europe, the disease spread rapidly in the kiwifruit cultivation areas from a single introduction. In this study, we investigated the genomic diversity of Psa biovar 3 strains during the primary clonal expansion in Europe using single molecule real-time (SMRT), Illumina and Sanger sequencing technologies. We recorded evidences of frequent mobilization and loss of transposon Tn6212, large chromosome inversions, and ectopic integration of IS sequences (remarkably ISPsy31, ISPsy36, and ISPsy37). While no phenotype change associated with Tn6212 mobilization could be detected, strains CRAFRU 12.29 and CRAFRU 12.50 did not elicit the hypersensitivity response (HR) on tobacco and eggplant leaves and were limited in their growth in kiwifruit leaves due to insertion of ISPsy31 and ISPsy36 in the hrpS and hrpR genes, respectively, interrupting the hrp cluster. Both strains had been isolated from symptomatic plants, suggesting coexistence of variant strains with reduced virulence together with virulent strains in mixed populations. The structural differences caused by rearrangements of self-genetic elements within European and New Zealand strains were comparable in number and type to those occurring among the European strains, in contrast with the significant difference in terms of nucleotide polymorphisms. We hypothesize a relaxation, during clonal expansion, of the selection limiting the accumulation of deleterious mutations associated with genome structural variation due to transposition of mobile elements. This consideration may be relevant when evaluating strategies to be adopted for epidemics management.

Analysis of mtDNA sequence variants in colorectal adenomatous polyps

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Grizzle William

2010-10-01

Full Text Available Abstract Colorectal tumors mostly arise from sporadic adenomatous polyps. Polyps are defined as a mass of cells that protrudes into the lumen of the colon. Adenomatous polyps are benign neoplasms that, by definition display some characteristics of dysplasia. It has been shown that polyps were benign tumors which may undergo malignant transformation. Adenomatous polyps have been classified into three histologic types; tubular, tubulovillous, and villous with increasing malignant potential. The ability to differentially diagnose these colorectal adenomatous polyps is important for therapeutic intervention. To date, little efforts have been directed to identifying genetic changes involved in adenomatous polyps. This study was designed to examine the relevance of mitochondrial genome alterations in the three adenomatous polyps. Using high resolution restriction endonucleases and PCR-based sequencing, fifty-seven primary fresh frozen tissues of adenomatous polyps (37 tumors and 20 matched surrounding normal tissues obtained from the southern regional Cooperative Human Tissue Network (CHTN and Grady Memorial Hospital at Atlanta were screened with three mtDNA regional primer pairs that spanned 5.9 kbp. Results from our data analyses revealed the presence of forty-four variants in some of these mitochondrial genes that the primers spanned; COX I, II, III, ATP 6, 8, CYT b, ND 5, 6 and tRNAs. Based on the MITODAT database as a sequence reference, 25 of the 44 (57% variants observed were unreported. Notably, a heteroplasmic variant C8515G/T in the MT-ATP 8 gene and a germline variant 8327delA in the tRNAlys was observed in all the tissue samples of the three adenomatous polyps in comparison to the referenced database sequence. A germline variant G9055A in the MT-ATP 6 gene had a frequency of 100% (17/17 in tubular and 57% (13/23 in villous adenomas; no corresponding variant was in tubulovillous adenomas. Furthermore, A9006G variant at MT-ATP 6 gene was

Molecular epidemiology and virulence of Escherichia coli O16:H5-ST131: comparison with H30 and H30-Rx subclones of O25b:H4-ST131.

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Dahbi, Ghizlane; Mora, Azucena; Mamani, Rosalia; López, Cecilia; Alonso, María Pilar; Marzoa, Juan; Blanco, Miguel; Herrera, Alexandra; Viso, Susana; García-Garrote, Fernando; Tchesnokova, Veronika; Billig, Mariya; de la Cruz, Fernando; de Toro, María; González-López, Juan José; Prats, Guillermo; Chaves, Fernando; Martínez-Martínez, Luis; López-Cerezo, Lorena; Denamur, Erick; Blanco, Jorge

2014-11-01

The present study was carried out to evaluate the prevalence of the clonal subgroup O16:H5-ST131 and the H30 and H30-Rx subclones among E. coli isolates causing extraintestinal infections and to know their virulence potential. The ST131 clonal group accounted for 490 (16%) of the 2995 isolates obtained from clinical samples in five Spanish hospitals during the study period (2005-2012). Among those 490 ST131 isolates, 456 belonged to serotype O25b:H4, 27 to O16:H5 and seven were O-non-typeable:H4 (ONT:H4). All 27 O16:H5 isolates showed fimH41, whereas fimH30 and fimH22 alleles were the most frequently detected among O25b:H4 isolates. The majority (381/490; 78%) of ST131 isolates belonged to H30 subclone, and 302 of 381 (79%) H30 isolates belonged to the H30-Rx subclone. Of the 27 O16:H5 isolates, 48% produced CTX-M-14; however, none produced CTX-M-15. In contrast, 46% of O25b:H4 isolates produced CTX-M-15 while only 2% produced CTX-M-14. More than a half of the O16:H5 isolates (56%) showed the ExPEC status which was significantly more prevalent within O25b:H4 isolates (81%) (P<0.01), especially among H30-Rx (97%) isolates. In the present study, a modified virotype scheme was applied within which approximately half (52%) of the O16:H5 isolates showed the C1 specific virotype. Despite their low virulence-gene score (mean of virulence genes 6.4 versus 8.5 in O25b:H4 isolates), six out of the 10 O16:H5 isolates assayed showed high virulence in the mouse model of sepsis (killed 90-100% of mice challenged). Furthermore, four O16:H5 isolates of virotypes A and C1, carrying K2 variant of group II capsule, showed lethality at 24h. Thus, certain O16:H5 fimH41 isolates show a similar in vivo virulence to that reported with the highly virulent O25b:H4 H30-Rx isolates (Mora et al., PLOS ONE 2014, e87025), supporting their potential virulence for humans. Copyright © 2014 Elsevier GmbH. All rights reserved.

Protocols for screening antimicrobial peptides that influence virulence gene expression in Staphylococcus aureus

DEFF Research Database (Denmark)

Bojer, Martin Saxtorph; Baldry, Mara; Ingmer, Hanne

2017-01-01

Compounds that inhibit virulence gene expression in bacterial pathogens have received increasing interest as possible alternatives to the traditional antibiotic treatment of infections. For the human pathogen Staphylococcus aureus, we have developed two simple assays based on reporter gene fusions...... to central virulence genes that are easily applicable for screening various sources of natural and synthetic peptides for anti-virulence effects. The plate assay is qualitative but simultaneously assesses the effect of gradient concentrations of the investigated compound, whereas the liquid assay...... is quantitative and can be employed to address whether a compound is acting on the central quorum sensing regulatory system, agr, that controls a large number of virulence genes in S. aureus....

Virulent Type A Francisella tularensis actively suppresses cytokine responses in human monocytes

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Gillette, Devyn D.; Curry, Heather M.; Cremer, Thomas; Ravneberg, David; Fatehchand, Kavin; Shah, Prexy A.; Wewers, Mark D.; Schlesinger, Larry S.; Butchar, Jonathan P.; Tridandapani, Susheela; Gavrilin, Mikhail A.

2014-01-01

Background: Human monocyte inflammatory responses differ between virulent and attenuated Francisella infection. Results: A mixed infection model showed that the virulent F. tularensis Schu S4 can attenuate inflammatory cytokine responses to the less virulent F. novicida in human monocytes. Conclusion: F. tularensis dampens inflammatory response by an active process. Significance: This suppression may contribute to enhanced pathogenicity of F. tularensis. Francisella tularensis is a Gram-negative facultative bacterium that can cause the disease tularemia, even upon exposure to low numbers of bacteria. One critical characteristic of Francisella is its ability to dampen or subvert the host immune response. Previous work has shown that monocytes infected with highly virulent F. tularensis subsp. tularensis strain Schu S4 responded with a general pattern of quantitatively reduced pro-inflammatory signaling pathway genes and cytokine production in comparison to those infected with the less virulent related F. novicida. However, it has been unclear whether the virulent Schu S4 was merely evading or actively suppressing monocyte responses. By using mixed infection assays with F. tularensis and F. novicida, we show that F. tularensis actively suppresses monocyte pro-inflammatory responses. Additional experiments show that this suppression occurs in a dose-dependent manner and is dependent upon the viability of F. tularensis. Importantly, F. tularensis was able to suppress pro-inflammatory responses to earlier infections with F. novicida. These results lend support that F. tularensis actively dampens human monocyte responses and this likely contributes to its enhanced pathogenicity. PMID:24783062

Uropathogenic Escherichia coli virulence genes: invaluable approaches for designing DNA microarray probes.

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Jahandeh, Nadia; Ranjbar, Reza; Behzadi, Payam; Behzadi, Elham

2015-01-01

The pathotypes of uropathogenic Escherichia coli (UPEC) cause different types of urinary tract infections (UTIs). The presence of a wide range of virulence genes in UPEC enables us to design appropriate DNA microarray probes. These probes, which are used in DNA microarray technology, provide us with an accurate and rapid diagnosis and definitive treatment in association with UTIs caused by UPEC pathotypes. The main goal of this article is to introduce the UPEC virulence genes as invaluable approaches for designing DNA microarray probes. Main search engines such as Google Scholar and databases like NCBI were searched to find and study several original pieces of literature, review articles, and DNA gene sequences. In parallel with in silico studies, the experiences of the authors were helpful for selecting appropriate sources and writing this review article. There is a significant variety of virulence genes among UPEC strains. The DNA sequences of virulence genes are fabulous patterns for designing microarray probes. The location of virulence genes and their sequence lengths influence the quality of probes. The use of selected virulence genes for designing microarray probes gives us a wide range of choices from which the best probe candidates can be chosen. DNA microarray technology provides us with an accurate, rapid, cost-effective, sensitive, and specific molecular diagnostic method which is facilitated by designing microarray probes. Via these tools, we are able to have an accurate diagnosis and a definitive treatment regarding UTIs caused by UPEC pathotypes.

Pathogenomic inference of virulence-associated genes in Leptospira interrogans.

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Jason S Lehmann

Full Text Available Leptospirosis is a globally important, neglected zoonotic infection caused by spirochetes of the genus Leptospira. Since genetic transformation remains technically limited for pathogenic Leptospira, a systems biology pathogenomic approach was used to infer leptospiral virulence genes by whole genome comparison of culture-attenuated Leptospira interrogans serovar Lai with its virulent, isogenic parent. Among the 11 pathogen-specific protein-coding genes in which non-synonymous mutations were found, a putative soluble adenylate cyclase with host cell cAMP-elevating activity, and two members of a previously unstudied ∼15 member paralogous gene family of unknown function were identified. This gene family was also uniquely found in the alpha-proteobacteria Bartonella bacilliformis and Bartonella australis that are geographically restricted to the Andes and Australia, respectively. How the pathogenic Leptospira and these two Bartonella species came to share this expanded gene family remains an evolutionary mystery. In vivo expression analyses demonstrated up-regulation of 10/11 Leptospira genes identified in the attenuation screen, and profound in vivo, tissue-specific up-regulation by members of the paralogous gene family, suggesting a direct role in virulence and host-pathogen interactions. The pathogenomic experimental design here is generalizable as a functional systems biology approach to studying bacterial pathogenesis and virulence and should encourage similar experimental studies of other pathogens.

The combined effects of starvation and pH on the virulence of ...

African Journals Online (AJOL)

ACER

2013-04-17

Apr 17, 2013 ... the virulence of Shigella sonnei ATCC25931. Ali Ellafi* .... P-values of < 0.05 were considered as significant. ..... Virulence factors of Escherichia coli O157:H7 and other ... gene expression in Porphyromonas gingivalis. Infect.

A novel inactivated gE/gI deleted pseudorabies virus (PRV) vaccine completely protects pigs from an emerged variant PRV challenge.

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Gu, Zhenqing; Dong, Jing; Wang, Jichun; Hou, Chengcai; Sun, Haifeng; Yang, Wenping; Bai, Juan; Jiang, Ping

2015-01-02

A highly virulent and antigenic variant of pseudorabies virus (PRV) broke out in China at the end of 2011 and caused great economic loss in the pig industry. In this study, an infectious bacterial artificial chromosome (BAC) clone containing the full-length genome of the emerged variant PRV ZJ01 strain was generated. The BAC-derived viruses, vZJ01-GFPΔgE/gI (gE/gI deleted strain, and exhibiting green autofluorescence), vZJ01ΔgE/gI (gE/gI deleted strain), and vZJ01gE/gI-R (gE/gI revertant strain), showed similar in vitro growth to their parent strain. In pigs, inactivated vZJ01ΔgE/gI vaccine generated significantly high levels of neutralizing antibodies against ZJ01 compared with Bartha-K61 live vaccine (pvaccine group survived without exhibiting any clinical sings, but two of five animals exhibited central nervous signs in the Bartha-K61 group. Meanwhile, all the non-vaccinated control animals died at 7 days post-challenge. This indicates that the inactivated vZJ01ΔgE/gI vaccine is a promising vaccine candidate for controlling the variant strains of PRV now circulating in China. Copyright © 2014 Elsevier B.V. All rights reserved.

Is dolphin morbillivirus virulent for white-beaked dolphins (Lagenorhynchus albirostris)?

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van Elk, C E; van de Bildt, M W G; Jauniaux, T; Hiemstra, S; van Run, P R W A; Foster, G; Meerbeek, J; Osterhaus, A D M E; Kuiken, T

2014-11-01

The virulence of morbilliviruses for toothed whales (odontocetes) appears to differ according to host species. In 4 species of odontocetes, morbilliviruses are highly virulent, causing large-scale epizootics with high mortality. In 8 other species of odontocetes, including white-beaked dolphins (Lagenorhynchus albirostris), morbilliviruses have been found as an incidental infection. In these species, the virulence of morbilliviruses is not clear. Therefore, the admission of 2 white-beaked dolphins with morbillivirus infection into a rehabilitation center provided a unique opportunity to investigate the virulence of morbillivirus in this species. By phylogenetic analysis, the morbilliviruses in both animals were identified as a dolphin morbillivirus (DMV) most closely related to that detected in a white-beaked dolphin in Germany in 2007. Both animals were examined clinically and pathologically. Case No. 1 had a chronic neural DMV infection, characterized by polioencephalitis in the cerebrum and morbillivirus antigen expression limited to neurons and glial cells. Surprisingly, no nervous signs were observed in this animal during the 6 months before death. Case No. 2 had a subacute systemic DMV infection, characterized by interstitial pneumonia, leucopenia, lymphoid depletion, and DMV antigen expression in mononuclear cells and syncytia in the lung and in mononuclear cells in multiple lymphoid organs. Cause of death was not attributed to DMV infection in either animal. DMV was not detected in 2 contemporaneously stranded white-beaked dolphins. Stranding rate did not increase in the region. These results suggest that DMV is not highly virulent for white-beaked dolphins. © The Author(s) 2013.

Virulence Factors of Aeromonas hydrophila: in the Wake of Reclassification

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Cody R Rasmussen-Ivey

2016-08-01

Full Text Available The ubiquitous jack-of-all-trades, Aeromonas hydrophila, is a freshwater, Gram-negative bacterial pathogen under revision in regard to its phylogenetic and functional affiliation with other aeromonads. While virulence factors are expectedly diverse across A. hydrophila strains and closely related species, our mechanistic knowledge of the vast majority of these factors is based on the molecular characterization of the strains A. hydrophila AH-3 and SSU, which were reclassified as A. piscicola AH-3 in 2009 and A. dhakensis SSU in 2013. Individually, these reclassifications raise important questions involving the applicability of previous research on A. hydrophila virulence mechanisms; however, this issue is exacerbated by a lack of genomic data on other research strains. Collectively, these changes represent a fundamental gap in the literature on A. hydrophila and confirm the necessity of biochemical, molecular, and morphological techniques in the classification of research strains that are used as a foundation for future research. This review revisits what is known about virulence in A. hydrophila and the feasibility of using comparative genomics in light of this phylogenetic revision. Conflicting data between virulence factors, secretion systems, quorum sensing, and their effect on A. hydrophila pathogenicity appears to be an artifact of inappropriate taxonomic comparisons and/or be due to the fact that these properties are strain-specific. This review audits emerging data on dominant virulence factors that are present in both A. dhakensis and A. hydrophila in order to synthesize existing data with the aim of locating where future research is needed.

Genes involved in virulence of the entomopathogenic fungus Beauveria bassiana.

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Valero-Jiménez, Claudio A; Wiegers, Harm; Zwaan, Bas J; Koenraadt, Constantianus J M; van Kan, Jan A L

2016-01-01

Pest insects cause severe damage to global crop production and pose a threat to human health by transmitting diseases. Traditionally, chemical pesticides (insecticides) have been used to control such pests and have proven to be effective only for a limited amount of time because of the rapid spread of genetic insecticide resistance. The basis of this resistance is mostly caused by (co)dominant mutations in single genes, which explains why insecticide use alone is an unsustainable solution. Therefore, robust solutions for insect pest control need to be sought in alternative methods such as biological control agents for which single-gene resistance is less likely to evolve. The entomopathogenic fungus Beauveria bassiana has shown potential as a biological control agent of insects, and insight into the mechanisms of virulence is essential to show the robustness of its use. With the recent availability of the whole genome sequence of B. bassiana, progress in understanding the genetics that constitute virulence toward insects can be made more quickly. In this review we divide the infection process into distinct steps and provide an overview of what is currently known about genes and mechanisms influencing virulence in B. bassiana. We also discuss the need for novel strategies and experimental methods to better understand the infection mechanisms deployed by entomopathogenic fungi. Such knowledge can help improve biocontrol agents, not only by selecting the most virulent genotypes, but also by selecting the genotypes that use combinations of virulence mechanisms for which resistance in the insect host is least likely to develop. Copyright © 2015 Elsevier Inc. All rights reserved.

NEW VIRULENCE FACTORS OF STREPTOCOCCUS PNEUMONIAE

NARCIS (Netherlands)

Hermans, Peter Wilhelmus Maria; Bootsma, Jeanette Hester; Burghout, Pieter Jan; Kuipers, Oscar; Bijlsma, Johanna Jacoba Elisabeth; Kloosterman, Tomas Gerrit; Andersen, Christian O.

2011-01-01

The present invention provides proteins/genes, which are essential for survival, and consequently, for virulence of Streptococcus pneumoniae in vivo, and thus are ideal vaccine candidates for a vaccine preparation against pneumococcal infection. Further, also antibodies against said protein(s) are

Antimicrobial peptide GH12 suppresses cariogenic virulence factors of Streptococcus mutans

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Wang, Yufei; Wang, Xiuqing; Jiang, Wentao; Wang, Kun; Luo, Junyuan; Li, Wei; Zhou, Xuedong; Zhang, Linglin

2018-01-01

ABSTRACT Cariogenic virulence factors of Streptococcus mutans include acidogenicity, aciduricity, and extracellular polysaccharides (EPS) synthesis. The de novo designed antimicrobial peptide GH12 has shown bactericidal effects on S. mutans, but its interaction with virulence and regulatory systems of S. mutans remains to be elucidated. The objectives were to investigate the effects of GH12 on virulence factors of S. mutans, and further explore the function mechanisms at enzymatic and transcriptional levels. To avoid decrease in bacterial viability, we limited GH12 to subinhibitory levels. We evaluated effects of GH12 on acidogenicity of S. mutans by pH drop, lactic acid measurement and lactate dehydrogenase (LDH) assay, on aciduricity through survival rate at pH 5.0 and F1F0-ATPase assay, and on EPS synthesis using quantitative measurement, morphology observation, vertical distribution analyses and biomass calculation. Afterwards, we conducted quantitative real-time PCR to acquire the expression profile of related genes. GH12 at 1/2 MIC (4 mg/L) inhibited acid production, survival rate, EPS synthesis, and biofilm formation. The enzymatic activity of LDH and F1F0-ATPase was inhibited, and ldh, gtfBCD, vicR, liaR, and comDE genes were significantly downregulated. In conclusion, GH12 inhibited virulence factors of S. mutans, through reducing the activity of related enzymes, downregulating virulence genes, and inactivating specific regulatory systems. PMID:29503706

Molecular basis of virulence in Staphylococcus aureus mastitis.

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Caroline Le Maréchal

Full Text Available S. aureus is one of the main pathogens involved in ruminant mastitis worldwide. The severity of staphylococcal infection is highly variable, ranging from subclinical to gangrenous mastitis. This work represents an in-depth characterization of S. aureus mastitis isolates to identify bacterial factors involved in severity of mastitis infection.We employed genomic, transcriptomic and proteomic approaches to comprehensively compare two clonally related S. aureus strains that reproducibly induce severe (strain O11 and milder (strain O46 mastitis in ewes. Variation in the content of mobile genetic elements, iron acquisition and metabolism, transcriptional regulation and exoprotein production was observed. In particular, O11 produced relatively high levels of exoproteins, including toxins and proteases known to be important in virulence. A characteristic we observed in other S. aureus strains isolated from clinical mastitis cases.Our data are consistent with a dose-dependant role of some staphylococcal factors in the hypervirulence of strains isolated from severe mastitis. Mobile genetic elements, transcriptional regulators, exoproteins and iron acquisition pathways constitute good targets for further research to define the underlying mechanisms of mastitis severity.

Ecto-5′-Nucleotidase: A Candidate Virulence Factor in Streptococcus sanguinis Experimental Endocarditis

OpenAIRE

Fan, Jingyuan; Zhang, Yongshu; Chuang-Smith, Olivia N.; Frank, Kristi L.; Guenther, Brian D.; Kern, Marissa; Schlievert, Patrick M.; Herzberg, Mark C.

2012-01-01

Streptococcus sanguinis is the most common cause of infective endocarditis (IE). Since the molecular basis of virulence of this oral commensal bacterium remains unclear, we searched the genome of S. sanguinis for previously unidentified virulence factors. We identified a cell surface ecto-5′-nucleotidase (Nt5e), as a candidate virulence factor. By colorimetric phosphate assay, we showed that S. sanguinis Nt5e can hydrolyze extracellular adenosine triphosphate to generate adenosine. Moreover, ...

Viability and Virulence of Entomopathogenic Nematodes Exposed to Ultraviolet Radiation.

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Shapiro-Ilan, David I; Hazir, Selcuk; Lete, Luis

2015-09-01

Entomopathogenic nematodes (EPNs) can be highly effective biocontrol agents, but their efficacy can be reduced due to exposure to environmental stress such as from ultraviolet (UV) radiation. Our objectives were to 1) compare UV tolerance among a broad array of EPN species, and 2) investigate the relationship between reduced nematode viability (after exposure to UV) and virulence. Nematodes exposed to a UV radiation (254 nm) for 10 or 20 min were assessed separately for viability (survival) and virulence to Galleria mellonella. We compared 9 different EPN species and 15 strains: Heterorhabditis bacteriophora (Baine, fl11, Oswego, and Vs strains), H. floridensis (332), H. georgiana (Kesha), H. indica (HOM1), H. megidis (UK211), Steinernema carpocapsae (All, Cxrd, DD136, and Sal strains), S. feltiae (SN), S. rarum (17C&E), and S. riobrave (355). In viability assessments, steinernematids, particularly strains of S. carpocapsae, generally exhibited superior UV tolerance compared with the heterorhabditids. However, some heterorhabditids tended to be more tolerant than others, e.g., H. megidis and H. bacteriophora (Baine) were most susceptible and H. bacteriophora (Vs) was the only heterorhabditid that did not exhibit a significant effect after 10 min of exposure. All heterorhabditids experienced reduced viability after 20 min exposure though several S. carpocapsae strains did not. In total, after 10 or 20 min exposure, the viability of seven nematode strains did not differ from their non-UV exposed controls. In virulence assays, steinernematids (particularly S. carpocapsae strains) also tended to exhibit higher UV tolerance. However, in contrast to the viability measurements, all nematodes experienced a reduction in virulence relative to their controls. Correlation analysis revealed that viability among nematode strains is not necessarily related to virulence. In conclusion, our results indicate that the impact of UV varies substantially among EPNs, and viability alone

Differential interactions of virulent and non-virulent H. parasuis strains with naïve or swine influenza virus pre-infected dendritic cells.

Science.gov (United States)

Mussá, Tufária; Rodríguez-Cariño, Carolina; Sánchez-Chardi, Alejandro; Baratelli, Massimiliano; Costa-Hurtado, Mar; Fraile, Lorenzo; Domínguez, Javier; Aragon, Virginia; Montoya, María

2012-11-16

Pigs possess a microbiota in the upper respiratory tract that includes Haemophilus parasuis. Pigs are also considered the reservoir of influenza viruses and infection with this virus commonly results in increased impact of bacterial infections, including those by H. parasuis. However, the mechanisms involved in host innate responses towards H. parasuis and their implications in a co-infection with influenza virus are unknown. Therefore, the ability of a non-virulent H. parasuis serovar 3 (SW114) and a virulent serovar 5 (Nagasaki) strains to interact with porcine bone marrow dendritic cells (poBMDC) and their modulation in a co-infection with swine influenza virus (SwIV) H3N2 was examined. At 1 hour post infection (hpi), SW114 interaction with poBMDC was higher than that of Nagasaki, while at 8 hpi both strains showed similar levels of interaction. The co-infection with H3N2 SwIV and either SW114 or Nagasaki induced higher levels of IL-1β, TNF-α, IL-6, IL-12 and IL-10 compared to mock or H3N2 SwIV infection alone. Moreover, IL-12 and IFN-α secretion differentially increased in cells co-infected with H3N2 SwIV and Nagasaki. These results pave the way for understanding the differences in the interaction of non-virulent and virulent strains of H. parasuis with the swine immune system and their modulation in a viral co-infection.

Luminescence, virulence and quorum sensing signal production by pathogenic Vibrio campbellii and Vibrio harveyi isolates.

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Defoirdt, T; Verstraete, W; Bossier, P

2008-05-01

To study the relationship between luminescence, autoinducer production and virulence of pathogenic vibrios. Luminescence, quorum sensing signal production and virulence towards brine shrimp nauplii of 13 Vibrio campbellii and Vibrio harveyi strains were studied. Although only two of the tested strains were brightly luminescent, all of them were shown to produce the three different types of quorum sensing signals known to be produced by Vibrio harveyi. Cell-free culture fluids of all strains significantly induced bioluminescence in the cholerae autoinducer 1, autoinducer 2 and harveyi autoinducer 1 reporter strains JAF375, JMH597 and JMH612, respectively. There was no relation between luminescence and signal production and virulence towards brine shrimp. There is a large difference between different strains of Vibrio campbellii and Vibrio harveyi with respect to bioluminescence. However, this is not reflected in signal production and virulence towards gnotobiotic brine shrimp. Moreover, there seems to be no relation between quorum sensing signal production and virulence towards brine shrimp. The results presented here indicate that strains that are most brightly luminescent are not necessarily the most virulent ones and that the lower virulence of some of the strains is not due to a lack of autoinducer production.

Hairy cell leukemia-variant

International Nuclear Information System (INIS)

Quadri, Mohammad I.; Al-Sheikh, Iman H.

2001-01-01

Hairy cell leukaemia variant is a very rare chronic lymphoproliferative disorder and is closely related to hairy cell leukemia. We hereby describe a case of hairy cell leukaemia variant for the first time in Saudi Arabia. An elderly Saudi man presented with pallor, massive splenomegaly, and moderate hepatomegaly. Hemoglobin was 7.7 g/dl, Platelets were 134 x109/l and white blood count was 140x10 9/l with 97% being abnormal lymphoid cells with cytoplasmic projections. The morphology, cytochemistry, and immunophenotype of the lymphoid cells were classical of hairy cell leukaemia variant. The bone marrow was easily aspirated and findings were consistent with hairy cell leukaemia variant. (author)

Ecological fitness and virulence features of Vibrio parahaemolyticus in estuarine environments.

Science.gov (United States)

Lovell, Charles R

2017-03-01

Vibrio parahaemolyticus is a commonly encountered and highly successful organism in marine ecosystems. It is a fast-growing, extremely versatile copiotroph that is active over a very broad range of conditions. It frequently occurs suspended in the water column (often attached to particles or zooplankton), and is a proficient colonist of submerged surfaces. This organism is an important pathogen of animals ranging from microcrustaceans to humans and is a causative agent of seafood-associated food poisoning. This review examines specific ecological adaptations of V. parahaemolyticus, including its broad tolerances to temperature and salinity, its utilization of a wide variety of organic carbon and energy sources, and its pervasive colonization of suspended and stationary materials that contribute to its success and ubiquity in temperate and tropical estuarine ecosystems. Several virulence-related features are examined, in particular the thermostable direct hemolysin (TDH), the TDH-related hemolysin (TRH), and the type 3 secretion system, and the possible importance of these features in V. parahaemolyticus pathogenicity is explored. The impact of new and much more effective PCR primers on V. parahaemolyticus detection and our views of virulent strain abundance are also described. It is clear that strains carrying the canonical virulence genes are far more common than previously thought, which opens questions regarding the role of these genes in pathogenesis. It is also clear that virulence is an evolving feature of V. parahaemolyticus and that novel combinations of virulence factors can lead to emergent virulence in which a strain that is markedly more pathogenic evolves and propagates to produce an outbreak. The effects of global climate change on the frequency of epidemic disease, the geographic distribution of outbreaks, and the human impacts of V. parahaemolyticus are increasing and this review provides information on why this ubiquitous human pathogen has

Copper tolerance and virulence in bacteria

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Ladomersky, Erik; Petris, Michael J.

2015-01-01

Copper (Cu) is an essential trace element for all aerobic organisms. It functions as a cofactor in enzymes that catalyze a wide variety of redox reactions due to its ability to cycle between two oxidation states, Cu(I) and Cu(II). This same redox property of copper has the potential to cause toxicity if copper homeostasis is not maintained. Studies suggest that the toxic properties of copper are harnessed by the innate immune system of the host to kill bacteria. To counter such defenses, bacteria rely on copper tolerance genes for virulence within the host. These discoveries suggest bacterial copper intoxication is a component of host nutritional immunity, thus expanding our knowledge of the roles of copper in biology. This review summarizes our current understanding of copper tolerance in bacteria, and the extent to which these pathways contribute to bacterial virulence within the host. PMID:25652326

Multilocus sequence typing and virulence analysis of Haemophilus parasuis strains isolated in five provinces of China.

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Wang, Liyan; Ma, Lina; Liu, Yongan; Gao, Pengcheng; Li, Youquan; Li, Xuerui; Liu, Yongsheng

2016-10-01

Haemophilus parasuis is the etiological agent of Glässers disease, which causes high morbidity and mortality in swine herds. Although H. parasuis strains can be classified into 15 serovars with the Kielstein-Rapp-Gabrielson serotyping scheme, a large number of isolates cannot be classified and have been designated 'nontypeable' strains. In this study, multilocus sequence typing (MLST) of H. parasuis was used to analyze 48 H. parasuis field strains isolated in China and two strains from Australia. Twenty-six new alleles and 29 new sequence types (STs) were detected, enriching the H. parasuis MLST databases. A BURST analysis indicated that H. parasuis lacks stable population structure and is highly heterogeneous, and that there is no association between STs and geographic area. When an UPGMA dendrogram was constructed, two major clades, clade A and clade B, were defined. Animal experiments, in which guinea pigs were challenged intraperitoneally with the bacterial isolates, supported the hypothesis that the H. parasuis STs in clade A are generally avirulent or weakly virulent, whereas the STs in clade B tend to be virulent. Copyright © 2016 Elsevier B.V. All rights reserved.

Inactivation of glutamate racemase (MurI) eliminates virulence in Streptococcus mutans.

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Zhang, Jianying; Liu, Jia; Ling, Junqi; Tong, Zhongchun; Fu, Yun; Liang, Min

2016-01-01

Inhibition of enzymes required for bacterial cell wall synthesis is often lethal or leads to virulence defects. Glutamate racemase (MurI), an essential enzyme in peptidoglycan biosynthesis, has been an attractive target for therapeutic interventions. Streptococcus mutans, one of the many etiological factors of dental caries, possesses a series of virulence factors associated with cariogenicity. However, little is known regarding the mechanism by which MurI influences pathogenesis of S. mutans. In this work, a stable mutant of S. mutans deficient in glutamate racemase (S. mutans FW1718) was constructed to investigate the impact of murI inactivation on cariogenic virulence in S. mutans UA159. Microscopy revealed that the murI mutant exhibited an enlarged cell size, longer cell chains, diminished cell⬜cell aggregation, and altered cell surface ultrastructure compared with the wild-type. Characterization of this mutant revealed that murI deficiency weakened acidogenicity, aciduricity, and biofilm formation ability of S. mutans (Pmutans virulence properties, making MurI a potential target for controlling dental caries. Copyright © 2016 Elsevier GmbH. All rights reserved.

Virulence Genotyping of Pasteurella multocida Isolated from Multiple Hosts from India

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Laxmi Narayan Sarangi

2014-01-01

Full Text Available In this study, 108 P. multocida isolates recovered from various host animals such as cattle, buffalo, swine, poultry (chicken, duck, and emu and rabbits were screened for carriage of 8 virulence associated genes. The results revealed some unique information on the prevalence of virulence associated genes among Indian isolates. With the exception of toxA gene, all other virulence associated genes were found to be regularly distributed among host species. Association study between capsule type and virulence genes suggested that pfhA, nanB, and nanH genes were regularly distributed among all serotypes with the exception of CapD, whereas toxA gene was found to be positively associated with CapD and CapA. The frequency of hgbA and nanH genes among swine isolates of Indian origin was found to be less in comparison to its equivalents around the globe. Interestingly, very high prevalence of tbpA gene was observed among poultry, swine, and rabbit isolates. Likewise, very high prevalence of pfhA gene (95.3% was observed among Indian isolates, irrespective of host species origin.

Virulence genotyping of Pasteurella multocida isolated from multiple hosts from India.

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Sarangi, Laxmi Narayan; Priyadarshini, Adyasha; Kumar, Santosh; Thomas, Prasad; Gupta, Santosh Kumar; Nagaleekar, Viswas Konasagara; Singh, Vijendra Pal

2014-01-01

In this study, 108 P. multocida isolates recovered from various host animals such as cattle, buffalo, swine, poultry (chicken, duck, and emu) and rabbits were screened for carriage of 8 virulence associated genes. The results revealed some unique information on the prevalence of virulence associated genes among Indian isolates. With the exception of toxA gene, all other virulence associated genes were found to be regularly distributed among host species. Association study between capsule type and virulence genes suggested that pfhA, nanB, and nanH genes were regularly distributed among all serotypes with the exception of CapD, whereas toxA gene was found to be positively associated with CapD and CapA. The frequency of hgbA and nanH genes among swine isolates of Indian origin was found to be less in comparison to its equivalents around the globe. Interestingly, very high prevalence of tbpA gene was observed among poultry, swine, and rabbit isolates. Likewise, very high prevalence of pfhA gene (95.3%) was observed among Indian isolates, irrespective of host species origin.

Antibiotics resistance phenomenon and virulence ability in bacteria from water environment

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Mohamed I. Azzam

2017-10-01

Full Text Available This study aims to determine the impact of five main drains as sources of antibiotics resistant bacteria in River Nile at Rosetta branch, and to generate a baseline data on their virulence ability. Out of 212 bacterial isolates, 39.2% and 60.8% were recovered from drains and Rosetta branch, respectively. Susceptibility of bacteria to different antibiotics showed multiple antibiotics resistances (MAR for the majority of isolates. Meanwhile, sensitivity was mostly directed to ofloxacin and norfloxacin antibiotics. Calculated MAR index values (>0.25 classified area of study as potentially health risk environment. Testing virulence ability of bacteria from drains showed positive results (65%. Contrastively, virulent strains in Rosetta branch were mostly lacking in this study. Concluding remarks justify the strong correlation (r = +0.82 between MAR and virulence of bacteria in polluted aquatic ecosystems, and highlight the potential of drains as reactors for their amplification and dissemination. The study suggests regular monitoring for antibiotics resistance in native bacteria of River Nile, prohibition of unregulated use of antibiotics, and proper management for wastes disposal.

Lack of Frank Agrammatism in the Nonfluent Agrammatic Variant of Primary Progressive Aphasia

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Naida L. Graham

2016-09-01

Full Text Available Background/Aims: Frank agrammatism, defined as the omission and/or substitution of grammatical morphemes with associated grammatical errors, is variably reported in patients with nonfluent variant primary progressive aphasia (nfPPA. This study addressed whether frank agrammatism is typical in agrammatic nfPPA patients when this feature is not required for diagnosis. Method: We assessed grammatical production in 9 patients who satisfied current diagnostic criteria. Although the focus was agrammatism, motor speech skills were also evaluated to determine whether dysfluency arose primarily from apraxia of speech (AOS, instead of, or in addition to, agrammatism. Volumetric MRI analyses provided impartial imaging-supported diagnosis. Results: The majority of cases exhibited neither frank agrammatism nor AOS. Conclusion: There are nfPPA patients with imaging-supported diagnosis and preserved motor speech skills who do not exhibit frank agrammatism, and this may persist beyond the earliest stages of the illness. Because absence of frank agrammatism is a subsidiary diagnostic feature in the logopenic variant of PPA, this result has implications for differentiation of the nonfluent and logopenic variants, and indicates that PPA patients with nonfluent speech in the absence of frank agrammatism or AOS do not necessarily have the logopenic variant.

Escherichia coli isolates from calf diarrhea in Korea and their virulent genetic characteristics.

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Hur, Jin; Jeon, Byung Woo; Kim, Yeong Ju; Oh, In Gyeong; Lee, John Hwa

2013-05-02

Escherichia coli strains were isolated from the feces of 130 diarrheic calves at different farms locations in Korea. The presence of the virulence genes, such as fanC, f41, f17a, eaeA, clpG, afa-8D, sta, stx1 and stx2, in each E. coli isolate was examined. Among the 314 isolates, 157 carried one or more of the virulence genes tested in this study. The most prevalent virulence gene was clpG (45.9%), although f17A (36.9%) and afa-8D (21.7%) were also frequently observed. The sta, stx1 and eaeA genes were detected in between approximately 13 and 17% of the isolates, and the fanC and fim41a genes were detected to a lesser extent. Collectively, our data indicated that diarrhea in calves in these locations can be ascribed to various virulence factors, and the pathogenesis may be more related to virulence genes such as, clpG, f17A, and afa-8D.

Cholesterol oxidase (ChoE) is not important in the virulence of Rhodococcus equi.

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Pei, Yanlong; Dupont, Chris; Sydor, Tobias; Haas, Albert; Prescott, John F

2006-12-20

To analyze further the role in virulence of the prominent cholesterol oxidase (ChoE) of Rhodococcus equi, an allelic exchange choE mutant from strain 103+ was constructed and assessed for virulence in macrophages, in mice, and in foals. There was no difference between the mutant and parent strain in cytotoxic activity for macrophages or in intra-macrophage multiplication. No evidence of attenuation was obtained in macrophages and in mice, but there was slight attenuation apparent in four intra-bronchially infected foals compared to infection of four foals with the virulent parent strain, based on a delayed rise in temperature of the choE-mutant infected foals. However, bacterial colony counts in the lung 2 weeks after infection were not significantly different, although there was a slight but non-significant (P=0.12) difference in lung:body weight ratio of the choE mutant versus virulent parent infected foals (mean 2.67+/-0.25% compared to 4.58+/-0.96%). We conclude that the cholesterol oxidase is not important for the virulence of R. equi.

The Three Lineages of the Diploid Hybrid Verticillium longisporum Differ in Virulence and Pathogenicity.

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Novakazi, Fluturë; Inderbitzin, Patrik; Sandoya, German; Hayes, Ryan J; von Tiedemann, Andreas; Subbarao, Krishna V

2015-05-01

Verticillium longisporum is an economically important vascular pathogen of Brassicaceae crops in different parts of the world. V. longisporum is a diploid hybrid that consists of three different lineages, each of which originated from a separate hybridization event between two different sets of parental species. We used 20 isolates representing the three V. longisporum lineages and the relative V. dahliae, and performed pathogenicity tests on 11 different hosts, including artichoke, cabbage, cauliflower, cotton, eggplant, horseradish, lettuce, linseed, oilseed rape (canola), tomato, and watermelon. V. longisporum was overall more virulent on the Brassicaceae crops than V. dahliae, which was more virulent than V. longisporum across the non-Brassicaceae crops. There were differences in virulence between the three V. longisporum lineages. V. longisporum lineage A1/D1 was the most virulent lineage on oilseed rape, and V. longisporum lineage A1/D2 was the most virulent lineage on cabbage and horseradish. We also found that on the non-Brassicaceae hosts eggplant, tomato, lettuce, and watermelon, V. longisporum was more or equally virulent than V. dahliae. This suggests that V. longisporum may have a wider potential host range than currently appreciated.

Steps toward broad-spectrum therapeutics: discovering virulence-associated genes present in diverse human pathogens

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de Rochefort Anna

2009-10-01

Full Text Available Abstract Background New and improved antimicrobial countermeasures are urgently needed to counteract increased resistance to existing antimicrobial treatments and to combat currently untreatable or new emerging infectious diseases. We demonstrate that computational comparative genomics, together with experimental screening, can identify potential generic (i.e., conserved across multiple pathogen species and novel virulence-associated genes that may serve as targets for broad-spectrum countermeasures. Results Using phylogenetic profiles of protein clusters from completed microbial genome sequences, we identified seventeen protein candidates that are common to diverse human pathogens and absent or uncommon in non-pathogens. Mutants of 13 of these candidates were successfully generated in Yersinia pseudotuberculosis and the potential role of the proteins in virulence was assayed in an animal model. Six candidate proteins are suggested to be involved in the virulence of Y. pseudotuberculosis, none of which have previously been implicated in the virulence of Y. pseudotuberculosis and three have no record of involvement in the virulence of any bacteria. Conclusion This work demonstrates a strategy for the identification of potential virulence factors that are conserved across a number of human pathogenic bacterial species, confirming the usefulness of this tool.

Ecto-5'-nucleotidase: a candidate virulence factor in Streptococcus sanguinis experimental endocarditis.

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Jingyuan Fan

Full Text Available Streptococcus sanguinis is the most common cause of infective endocarditis (IE. Since the molecular basis of virulence of this oral commensal bacterium remains unclear, we searched the genome of S. sanguinis for previously unidentified virulence factors. We identified a cell surface ecto-5'-nucleotidase (Nt5e, as a candidate virulence factor. By colorimetric phosphate assay, we showed that S. sanguinis Nt5e can hydrolyze extracellular adenosine triphosphate to generate adenosine. Moreover, a nt5e deletion mutant showed significantly shorter lag time (P<0.05 to onset of platelet aggregation than the wild-type strain, without affecting platelet-bacterial adhesion in vitro (P=0.98. In the absence of nt5e, S. sanguinis caused IE (4 d in a rabbit model with significantly decreased mass of vegetations (P<0.01 and recovered bacterial loads (log(10CFU, P=0.01, suggesting that Nt5e contributes to the virulence of S. sanguinis in vivo. As a virulence factor, Nt5e may function by (i hydrolyzing ATP, a pro-inflammatory molecule, and generating adenosine, an immunosuppressive molecule to inhibit phagocytic monocytes/macrophages associated with valvular vegetations. (ii Nt5e-mediated inhibition of platelet aggregation could also delay presentation of platelet microbicidal proteins to infecting bacteria on heart valves. Both plausible Nt5e-dependent mechanisms would promote survival of infecting S. sanguinis. In conclusion, we now show for the first time that streptococcal Nt5e modulates S. sanguinis-induced platelet aggregation and may contribute to the virulence of streptococci in experimental IE.

Splicing analysis of 14 BRCA1 missense variants classifies nine variants as pathogenic

DEFF Research Database (Denmark)

Ahlborn, Lise B; Dandanell, Mette; Steffensen, Ane Y

2015-01-01

by functional analysis at the protein level. Results from a validated mini-gene splicing assay indicated that nine BRCA1 variants resulted in splicing aberrations leading to truncated transcripts and thus can be considered pathogenic (c.4987A>T/p.Met1663Leu, c.4988T>A/p.Met1663Lys, c.5072C>T/p.Thr1691Ile, c......Pathogenic germline mutations in the BRCA1 gene predispose carriers to early onset breast and ovarian cancer. Clinical genetic screening of BRCA1 often reveals variants with uncertain clinical significance, complicating patient and family management. Therefore, functional examinations are urgently...... needed to classify whether these uncertain variants are pathogenic or benign. In this study, we investigated 14 BRCA1 variants by in silico splicing analysis and mini-gene splicing assay. All 14 alterations were missense variants located within the BRCT domain of BRCA1 and had previously been examined...

Virulence and genomic feature of multidrug resistant Campylobacter jejuni isolated from broiler chicken

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Haihong Hao

2016-10-01

Full Text Available The aim of this study was to reveal the molecular mechanism involved in multidrug resistance and virulence of Campylobacter jejuni isolated from broiler chickens. The virulence of six multidrug resistant C. jejuni was determined by in vitro and in vivo methods. The de novo whole genome sequencing technology and molecular biology methods were used to analyze the genomic features associated with the multidrug resistance and virulence of a selected isolate (C. jejuni 1655. The comparative genomic analyses revealed a large number of single nucleotide polymorphisms, deletions, rearrangements, and inversions in C. jejuni 1655 compared to reference C. jejuni genomes. The co-emergence of Thr-86-Ile mutation in gyrA gene, A2075G mutation in 23S rRNA gene, tetO, aphA and aadE genes and pTet plasmid in C. jejuni 1655 contributed its multidrug resistance to fluoroquinolones, macrolides, tetracycline and aminoglycosides. The combination of multiple virulence genes may work together to confer the relative higher virulence in C. jejuni 1655. The co-existence of mobile gene elements (e.g. pTet and CRISPR-Cas system in C. jejuni 1655 may play an important role in the gene transfer and immune defense. The present study provides basic information of phenotypic and genomic features of C. jejuni 1655, a strain recently isolated from a chicken displaying multidrug resistance and relatively high level of virulence.

Virulence potential of Escherichia coli strains causing asymptomatic bacteriuria during pregnancy.

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Lavigne, Jean-Philippe; Boutet-Dubois, Adeline; Laouini, Dorsaf; Combescure, Christophe; Bouziges, Nicole; Marès, Pierre; Sotto, Albert

2011-11-01

We compared the virulence properties of a collection of asymptomatic bacteriuria (ABU) Escherichia coli strains to urinary tract infection (UTI) strains isolated from pregnant women in a university hospital over 1 year. The in vitro and in vivo studies suggest that ABU strains presented a virulence behavior similar to that of strains isolated from cases of cystitis.

Comparative Genomics of Mycoplasma bovis Strains Reveals That Decreased Virulence with Increasing Passages Might Correlate with Potential Virulence-Related Factors

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Muhammad A. Rasheed

2017-05-01

Full Text Available Mycoplasma bovis is an important cause of bovine respiratory disease worldwide. To understand its virulence mechanisms, we sequenced three attenuated M. bovis strains, P115, P150, and P180, which were passaged in vitro 115, 150, and 180 times, respectively, and exhibited progressively decreasing virulence. Comparative genomics was performed among the wild-type M. bovis HB0801 (P1 strain and the P115, P150, and P180 strains, and one 14.2-kb deleted region covering 14 genes was detected in the passaged strains. Additionally, 46 non-sense single-nucleotide polymorphisms and indels were detected, which confirmed that more passages result in more mutations. A subsequent collective bioinformatics analysis of paralogs, metabolic pathways, protein-protein interactions, secretory proteins, functionally conserved domains, and virulence-related factors identified 11 genes that likely contributed to the increased attenuation in the passaged strains. These genes encode ascorbate-specific phosphotransferase system enzyme IIB and IIA components, enolase, L-lactate dehydrogenase, pyruvate kinase, glycerol, and multiple sugar ATP-binding cassette transporters, ATP binding proteins, NADH dehydrogenase, phosphate acetyltransferase, transketolase, and a variable surface protein. Fifteen genes were shown to be enriched in 15 metabolic pathways, and they included the aforementioned genes encoding pyruvate kinase, transketolase, enolase, and L-lactate dehydrogenase. Hydrogen peroxide (H2O2 production in M. bovis strains representing seven passages from P1 to P180 decreased progressively with increasing numbers of passages and increased attenuation. However, eight mutants specific to eight individual genes within the 14.2-kb deleted region did not exhibit altered H2O2 production. These results enrich the M. bovis genomics database, and they increase our understanding of the mechanisms underlying M. bovis virulence.

Virulence Genes and Antibiotic Susceptibilities of Uropathogenic E. coli Strains.

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Uzun, Cengiz; Oncül, Oral; Gümüş, Defne; Alan, Servet; Dayioğlu, Nurten; Küçüker, Mine Anğ

2015-01-01

The aim of this study is to detect the presence of and possible relation between virulence genes and antibiotic resistance in E. coli strains isolated from patients with acute, uncomplicated urinary tract infections (UTI). 62 E. coli strains isolated from patients with acute, uncomplicated urinary tract infections (50 strains isolated from acute uncomplicated cystitis cases (AUC); 12 strains from acute uncomplicated pyelonephritis cases (AUP)) were screened for virulence genes [pap (pyelonephritis-associated pili), sfa/foc (S and F1C fimbriae), afa (afimbrial adhesins), hly (hemolysin), cnf1 (cytotoxic necrotizing factor), aer (aerobactin), PAI (pathogenicity island marker), iroN (catecholate siderophore receptor), ompT (outer membrane protein T), usp (uropathogenic specific protein)] by PCR and for antimicrobial resistance by disk diffusion method according to CLSI criteria. It was found that 56 strains (90.3%) carried at least one virulence gene. The most common virulence genes were ompT (79%), aer (51.6%), PAI (51.6%) and usp (56.5%). 60% of the strains were resistant to at least one antibiotic. The highest resistance rates were against ampicillin (79%) and co-trimoxazole (41.9%). Fifty percent of the E. coli strains (31 strains) were found to be multiple resistant. Eight (12.9%) out of 62 strains were found to be ESBL positive. Statistically significant relationships were found between the absence of usp and AMP - SXT resistance, iroN and OFX - CIP resistance, PAI and SXT resistance, cnf1 and AMP resistance, and a significant relationship was also found between the presence of the afa and OFX resistance. No difference between E. coli strains isolated from two different clinical presentations was found in terms of virulence genes and antibiotic susceptibility.

HD-GYP domain proteins regulate biofilm formation and virulence in Pseudomonas aeruginosa

DEFF Research Database (Denmark)

Ryan, Robert P.; Lucey, Jean; O'Donovan, Karen

2009-01-01

residues (YN-GYP). Here we have investigated the role of these proteins in biofilm formation, virulence factor synthesis and virulence of P. aeruginosa. Mutation of PA4108 and PA4781 led to an increase in the level of cyclic-di-GMP in P. aeruginosa, consistent with the predicted activity of the encoded......2572 had a negative influence on swarming that was cryptic and was revealed only after removal of an uncharacterized C-terminal domain. Mutation of PA4108, PA4781 and PA2572 had distinct effects on biofilm formation and architecture of P. aeruginosa. All three proteins contributed to virulence of P...

From the Outside-In: the Francisella tularensis Envelope and Virulence

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Hannah M. Rowe

2015-12-01

Full Text Available Francisella tularensis is a highly-infectious bacterium that causes the rapid, and often lethal disease, tularemia. Many studies have been performed to identify and characterize the virulence factors that F. tularensis uses to infect a wide variety of hosts and host cell types, evade immune defenses, and induce severe disease and death. This review focuses on the virulence factors that are present in the F. tularensis envelope, including capsule, LPS, outer membrane, periplasm, inner membrane, secretion systems, and various molecules in each of aforementioned sub-compartments. Whereas no single bacterial molecule or molecular complex single-handedly controls F. tularensis virulence, we review here how diverse bacterial systems work in conjunction to subvert the immune system, attach to and invade host cells, alter phagosome/lysosome maturation pathways, replicate in host cells without being detected, inhibit apoptosis, and induce host cell death for bacterial release and infection of adjacent cells. Given that the F. tularensis envelope is the outermost layer of the bacterium, we highlight herein how many of these molecules directly interact with the host to promote infection and disease. These and future envelope studies are important to advance our collective understanding of F. tularensis virulence mechanisms and offer targets for future vaccine development efforts.

Mixed infections reveal virulence differences between host-specific bee pathogens.

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Klinger, Ellen G; Vojvodic, Svjetlana; DeGrandi-Hoffman, Gloria; Welker, Dennis L; James, Rosalind R

2015-07-01

Dynamics of host-pathogen interactions are complex, often influencing the ecology, evolution and behavior of both the host and pathogen. In the natural world, infections with multiple pathogens are common, yet due to their complexity, interactions can be difficult to predict and study. Mathematical models help facilitate our understanding of these evolutionary processes, but empirical data are needed to test model assumptions and predictions. We used two common theoretical models regarding mixed infections (superinfection and co-infection) to determine which model assumptions best described a group of fungal pathogens closely associated with bees. We tested three fungal species, Ascosphaera apis, Ascosphaera aggregata and Ascosphaera larvis, in two bee hosts (Apis mellifera and Megachile rotundata). Bee survival was not significantly different in mixed infections vs. solo infections with the most virulent pathogen for either host, but fungal growth within the host was significantly altered by mixed infections. In the host A. mellifera, only the most virulent pathogen was present in the host post-infection (indicating superinfective properties). In M. rotundata, the most virulent pathogen co-existed with the lesser-virulent one (indicating co-infective properties). We demonstrated that the competitive outcomes of mixed infections were host-specific, indicating strong host specificity among these fungal bee pathogens. Published by Elsevier Inc.

Ecto-5'-nucleotidase: a candidate virulence factor in Streptococcus sanguinis experimental endocarditis.

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Fan, Jingyuan; Zhang, Yongshu; Chuang-Smith, Olivia N; Frank, Kristi L; Guenther, Brian D; Kern, Marissa; Schlievert, Patrick M; Herzberg, Mark C

2012-01-01

Streptococcus sanguinis is the most common cause of infective endocarditis (IE). Since the molecular basis of virulence of this oral commensal bacterium remains unclear, we searched the genome of S. sanguinis for previously unidentified virulence factors. We identified a cell surface ecto-5'-nucleotidase (Nt5e), as a candidate virulence factor. By colorimetric phosphate assay, we showed that S. sanguinis Nt5e can hydrolyze extracellular adenosine triphosphate to generate adenosine. Moreover, a nt5e deletion mutant showed significantly shorter lag time (PS. sanguinis caused IE (4 d) in a rabbit model with significantly decreased mass of vegetations (PS. sanguinis in vivo. As a virulence factor, Nt5e may function by (i) hydrolyzing ATP, a pro-inflammatory molecule, and generating adenosine, an immunosuppressive molecule to inhibit phagocytic monocytes/macrophages associated with valvular vegetations. (ii) Nt5e-mediated inhibition of platelet aggregation could also delay presentation of platelet microbicidal proteins to infecting bacteria on heart valves. Both plausible Nt5e-dependent mechanisms would promote survival of infecting S. sanguinis. In conclusion, we now show for the first time that streptococcal Nt5e modulates S. sanguinis-induced platelet aggregation and may contribute to the virulence of streptococci in experimental IE.

High Prevalence of Diabetes-Predisposing Variants in MODY Genes Among Danish Women With Gestational Diabetes Mellitus

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Gjesing, Anette Marianne Prior; Rui, Gao; Lauenborg, Jeannet

2017-01-01

Context: Gestational diabetes mellitus (GDM), defined as any degree of glucose intolerance with first recognition during pregnancy, is a heterogeneous form of diabetes characterized by various degrees ofβ-cell dysfunction. Objectives: We aimed to estimate the prevalence of possibly pathogenic...... variants in the maturity-onset diabetes of the young genesGCK,HNF1A,HNF4A,HNF1B, andINSamong women with GDM. Furthermore, we examined the glucose tolerance status in variant carriers vs noncarriers at follow-up. Design Setting and Patients: We sequenced the coding regions and intron/exon boundaries of.......9% (95% confidence interval: 3.5% to 8.4%). At follow-up, 15 out of 135 women with diabetes (11%) were carriers of variants inGCK,HNF1A,HNF4A,HNF1B, orINS. Conclusions: Almost 6% of Danish women with diet-treated GDM have possibly pathogenic variants inGCK,HNF1A,HNF4A,HNF1B, orINS. These women...

Molecular Characterization of Putative Virulence Determinants in Burkholderia pseudomallei

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Suat Moi Puah

2014-01-01

Full Text Available The Gram-negative saprophyte Burkholderia pseudomallei is the causative agent of melioidosis, an infectious disease which is endemic in Southeast Asia and northern Australia. This bacterium possesses many virulence factors which are thought to contribute to its survival and pathogenicity. Using a virulent clinical isolate of B. pseudomallei and an attenuated strain of the same B. pseudomallei isolate, 6 genes BPSL2033, BP1026B_I2784, BP1026B_I2780, BURPS1106A_A0094, BURPS1106A_1131, and BURPS1710A_1419 were identified earlier by PCR-based subtractive hybridization. These genes were extensively characterized at the molecular level, together with an additional gene BPSL3147 that had been identified by other investigators. Through a reverse genetic approach, single-gene knockout mutants were successfully constructed by using site-specific insertion mutagenesis and were confirmed by PCR. BPSL2033::Km and BURPS1710A_1419::Km mutants showed reduced rates of survival inside macrophage RAW 264.7 cells and also low levels of virulence in the nematode infection model. BPSL2033::Km demonstrated weak statistical significance (P=0.049 at 8 hours after infection in macrophage infection study but this was not seen in BURPS1710A_1419::Km. Nevertheless, complemented strains of both genes were able to partially restore the gene defects in both in vitro and in vivo studies, thus suggesting that they individually play a minor role in the virulence of B. pseudomallei.

The sensor kinase MprB is required for Rhodococcus equi virulence.

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MacArthur, Iain; Parreira, Valeria R; Lepp, Dion; Mutharia, Lucy M; Vazquez-Boland, José A; Prescott, John F

2011-01-10

Rhodococcus equi is a soil bacterium and, like Mycobacterium tuberculosis, a member of the mycolata. Through possession of a virulence plasmid, it has the ability to infect the alveolar macrophages of foals, resulting in pyogranulomatous bronchopneumonia. The virulence plasmid has an orphan two-component system (TCS) regulatory gene, orf8, mutation of which completely attenuates virulence. This study attempted to find the cognate sensor kinase (SK) of orf8. Annotation of the R. equi strain 103 genome identified 23 TCSs encoded on the chromosome, which were used in a DNA microarray to compare TCS gene transcription in murine macrophage-like cells to growth in vitro. This identified six SKs as significantly up-regulated during growth in macrophages. Mutants of these SKs were constructed and their ability to persist in macrophages was determined with one SK, MprB, found to be required for intracellular survival. The attenuation of the mprB- mutant, and its complementation, was confirmed in a mouse virulence assay. In silico analysis of the R. equi genome sequence identified an MprA binding box motif homologous to that of M. tuberculosis, on mprA, pepD, sigB and sigE. The results of this study also show that R. equi responds to the macrophage environment differently from M. tuberculosis. MprB is the first SK identified as required for R. equi virulence and intracellular survival. Copyright © 2010 Elsevier B.V. All rights reserved.

Virulence and genetic diversity among isolates of Mycosphaerella fijiensis in two regions of Brazil.

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Silva, G F; Santos, V S; Sousa, N R; Hanada, R E; Gasparotto, L

2016-04-27

Black sigatoka, caused by the fungus Mycosphaerella fijiensis (anamorphic stage: Paracercospora fijiensis), was first detected in Brazil in early 1998 in the Benjamin Constant and Tabatinga municipalities in the State of Amazonas, near to where the borders of Brazil, Colombia, and Peru converge. Understanding how cultivars react to the pathogen, and characterizing the genetic variability of isolates from two distant and distinct banana-producing regions, are important for determining the virulence of M. fijiensis. In the present study, the genetic diversity of 22 M. fijiensis isolates was assessed using simple sequence repeats (SSR) markers, and their virulence was determined following inoculation on three different banana tree cultivars. All 22 isolates caused symptoms of the disease in the Maçã and Prata Comum cultivars 45 days after inoculation, and at least two virulence groups were identified for the Maçã and Prata Comum cultivars. For the D'Angola cultivars, two virulence groups were observed only after 60 days post-inoculation, and three of the isolates were not virulent. Using SSR markers, the isolates from two different regions of Brazil were placed into two genetic groups, both genetically distant from the Mf 138 isolate collected in Leticia, Colombia. There was no evidence of correlation between the virulence groups and the genetic diversity groups. These results demonstrate variability in virulence between isolates as measured by the severity of black sigatoka in the analyzed cultivars.

A novel anti-virulence gene revealed by proteomic analysis in Shigella flexneri 2a

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Ying Tianyi

2010-06-01

Full Text Available Abstract Background Shigella flexneri is a gram-negative, facultative pathogen that causes the majority of communicable bacterial dysenteries in developing countries. The virulence factors of S. flexneri have been shown to be produced at 37 degrees C but not at 30 degrees C. To discover potential, novel virulence-related proteins of S. flexneri, we performed differential in-gel electrophoresis (DIGE analysis to measure changes in the expression profile that are induced by a temperature increase. Results The ArgT protein was dramatically down-regulated at 37 degrees C. In contrast, the ArgT from the non-pathogenic E. coli did not show this differential expression as in S. flexneri, which suggested that argT might be a potential anti-virulence gene. Competitive invasion assays in HeLa cells and in BALB/c mice with argT mutants were performed, and the results indicated that the over-expression of ArgTY225D would attenuate the virulence of S. flexneri. A comparative proteomic analysis was subsequently performed to investigate the effects of ArgT in S. flexneri at the molecular level. We show that HtrA is differentially expressed among different derivative strains. Conclusion Gene argT is a novel anti-virulence gene that may interfere with the virulence of S. flexneri via the transport of specific amino acids or by affecting the expression of the virulence factor, HtrA.

The majority of genes in the pathogenic Neisseria species are present in non-pathogenic Neisseria lactamica, including those designated as 'virulence genes'

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Saunders Nigel J

2006-05-01

Full Text Available Abstract Background Neisseria meningitidis causes the life-threatening diseases meningococcal meningitis and meningococcal septicemia. Neisseria gonorrhoeae is closely related to the meningococcus, but is the cause of the very different infection, gonorrhea. A number of genes have been implicated in the virulence of these related yet distinct pathogens, but the genes that define and differentiate the species and their behaviours have not been established. Further, a related species, Neisseria lactamica is not associated with either type of infection in normally healthy people, and lives as a harmless commensal. We have determined which of the genes so far identified in the genome sequences of the pathogens are also present in this non-pathogenic related species. Results Thirteen unrelated strains of N. lactamica were investigated using comparative genome hybridization to the pan-Neisseria microarray-v2, which contains 2845 unique gene probes. The presence of 127 'virulence genes' was specifically addressed; of these 85 are present in N. lactamica. Of the remaining 42 'virulence genes' only 11 are present in all four of the sequenced pathogenic Neisseria. Conclusion Assessment of the complete dataset revealed that the vast majority of genes present in the pathogens are also present in N. lactamica. Of the 1,473 probes to genes shared by all four pathogenic genome sequences, 1,373 hybridize to N. lactamica. These shared genes cannot include genes that are necessary and sufficient for the virulence of the pathogens, since N. lactamica does not share this behaviour. This provides an essential context for the interpretation of gene complement studies of the pathogens.

Quorum-sensing regulators control virulence gene expression in Vibrio cholerae

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Zhu, Jun; Miller, Melissa B.; Vance, Russell E.; Dziejman, Michelle; Bassler, Bonnie L.; Mekalanos, John J.

2002-01-01

The production of virulence factors including cholera toxin and the toxin-coregulated pilus in the human pathogen Vibrio cholerae is strongly influenced by environmental conditions. The well-characterized ToxR signal transduction cascade is responsible for sensing and integrating the environmental information and controlling the virulence regulon. We show here that, in addition to the known components of the ToxR signaling circuit, quorum-sensing regulators are involved in regulation of V. ch...

Identification of Salmonella typhimurium Genes Required for Colonization of the Chicken Alimentary Tract and for Virulence in Newly Hatched Chicks

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Turner, Arthur K.; Lovell, Margaret A.; Hulme, Scott D.; Zhang-Barber, Li; Barrow, Paul A.

1998-01-01

From a collection of 2,800 Tn5-TC1 transposon mutants of Salmonella typhimurium F98, 18 that showed reduced intestinal colonization of 3-week-old chicks were identified. The sites of transposon insertion were determined for most of the mutants and included insertions in the lipopolysaccharide biosynthesis genes rfaK, rfaY, rfbK, and rfbB and the genes dksA, clpB, hupA, and sipC. In addition, identification was made of an insertion into a novel gene that encodes a protein showing similarity to the IIC component of the mannose class of phosphoenolpyruvate-carbohydrate phosphotransferase systems, which we putatively called ptsC. Transduction of most of the transposon mutations to a fresh S. typhimurium F98 genetic background and construction of defined mutations in the rfbK, dksA, hupA, sipC, and ptsC genes of S. typhimurium F98 supported the role in colonization of all but the pts locus. The virulence of the rfbK, dksA, hupA, sipC, and ptsC defined mutants and clpB and rfaY transductants in 1-day-old chicks was tested. All but the ptsC and rfaY mutants were attenuated for virulence. A number of other phenotypes associated with some of the mutations are described. PMID:9573095

The HtrA-Like Protease CD3284 Modulates Virulence of Clostridium difficile

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Bakker, Dennis; Buckley, Anthony M.; de Jong, Anne; van Winden, Vincent J. C.; Verhoeks, Joost P. A.; Kuipers, Oscar P.; Douce, Gillian R.; Kuijper, Ed J.; Smits, Wiep Klaas; Corver, Jeroen

2014-01-01

In the past decade, Clostridium difficile has emerged as an important gut pathogen. Symptoms of C. difficile infection range from mild diarrhea to pseudomembranous colitis. Besides the two main virulence factors toxin A and toxin B, other virulence factors are likely to play a role in the

Genetic recombination and Cryptosporidium hominis virulent subtype IbA10G2.

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Li, Na; Xiao, Lihua; Cama, Vitaliano A; Ortega, Ynes; Gilman, Robert H; Guo, Meijin; Feng, Yaoyu

2013-10-01

Little is known about the emergence and spread of virulent subtypes of Cryptosporidium hominis, the predominant species responsible for human cryptosporidiosis. We conducted sequence analyses of 32 genetic loci of 53 C. hominis specimens isolated from a longitudinally followed cohort of children living in a small community. We identified by linkage disequilibrium and recombination analyses only limited genetic recombination, which occurred exclusively within the 60-kDa glycoprotein gene subtype IbA10G2, a predominant subtype for outbreaks in industrialized nations and a virulent subtype in the study community. Intensive transmission of virulent subtype IbA10G2 in the study area might have resulted in genetic recombination with other subtypes. Moreover, we identified selection for IbA10G2 at a 129-kb region around the 60-kDa glycoprotein gene in chromosome 6. These findings improve our understanding of the origin and evolution of C. hominis subtypes and the spread of virulent subtypes.

The evolution of intermediate castration virulence and ant coexistence in a spatially structured environment.

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Szilágyi, András; Scheuring, István; Edwards, David P; Orivel, Jerome; Yu, Douglas W

2009-12-01

Theory suggests that spatial structuring should select for intermediate levels of virulence in parasites, but empirical tests are rare and have never been conducted with castration (sterilizing) parasites. To test this theory in a natural landscape, we construct a spatially explicit model of the symbiosis between the ant-plant Cordia nodosa and its two, protecting ant symbionts, Allomerus and Azteca. Allomerus is also a castration parasite, preventing fruiting to increase colony fecundity. Limiting the dispersal of Allomerus and host plant selects for intermediate castration virulence. Increasing the frequency of the mutualist, Azteca, selects for higher castration virulence in Allomerus, because seeds from Azteca-inhabited plants are a public good that Allomerus exploits. These results are consistent with field observations and, to our knowledge, provide the first empirical evidence supporting the hypothesis that spatial structure can reduce castration virulence and the first such evidence in a natural landscape for either mortality or castration virulence.

Microbial virulence and interactions with metals

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German, N.; Lüthje, Freja Lea; Hao, X.

2016-01-01

Transition metals, such as iron, copper, zinc, and manganese play an important role in many bacterial biological processes that add to an overall evolutional fitness of bacteria. They are often involved in regulation of bacterial virulence as a mechanism of host invasion. However, the same transi...

Lupus risk variants in the PXK locus alter B-cell receptor internalization

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Samuel E. Vaughn

2015-01-01

Full Text Available Genome wide association studies have identified variants in PXK that confer risk for humoral autoimmune diseases, including systemic lupus erythematosus (SLE or lupus, rheumatoid arthritis and more recently systemic sclerosis. While PXK is involved in trafficking of epidermal growth factor Receptor (EGFR in COS-7 cells, mechanisms linking PXK to lupus pathophysiology have remained undefined. In an effort to uncover the mechanism at this locus that increases lupus-risk, we undertook a fine-mapping analysis in a large multi-ancestral study of lupus patients and controls. We define a large (257kb common haplotype that confers lupus risk detected only in European ancestral populations and spans the promoter through the 3’ UTR of PXK. The strongest association was found at rs6445972 with P < 4.62 x 10-10, OR 0.81 (0.75 – 0.86. Using stepwise logistic regression analysis, we demonstrate that one signal drives the genetic association in the region. Bayesian analysis confirms our results, identifying a 95% credible set consisting of 172 variants spanning 200kb.Functionally, we found that PXK operates on the B-cell antigen receptor (BCR; we confirmed that PXK influenced the rate of BCR internalization. Furthermore, we demonstrate that individuals carrying the risk haplotype exhibited a decreased rate of BCR internalization, a process known to impact B cell survival and cell fate. Taken together, these data define a new candidate mechanism for the genetic association of variants around PXK with lupus risk and highlight the regulation of intracellular trafficking as a genetically regulated pathway mediating human autoimmunity.

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

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

2017-01-01

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

De Novo Truncating Variants in SON Cause Intellectual Disability, Congenital Malformations, and Failure to Thrive.

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Tokita, Mari J; Braxton, Alicia A; Shao, Yunru; Lewis, Andrea M; Vincent, Marie; Küry, Sébastien; Besnard, Thomas; Isidor, Bertrand; Latypova, Xénia; Bézieau, Stéphane; Liu, Pengfei; Motter, Connie S; Melver, Catherine Ward; Robin, Nathaniel H; Infante, Elena M; McGuire, Marianne; El-Gharbawy, Areeg; Littlejohn, Rebecca O; McLean, Scott D; Bi, Weimin; Bacino, Carlos A; Lalani, Seema R; Scott, Daryl A; Eng, Christine M; Yang, Yaping; Schaaf, Christian P; Walkiewicz, Magdalena A

2016-09-01

SON is a key component of the spliceosomal complex and a critical mediator of constitutive and alternative splicing. Additionally, SON has been shown to influence cell-cycle progression, genomic integrity, and maintenance of pluripotency in stem cell populations. The clear functional relevance of SON in coordinating essential cellular processes and its presence in diverse human tissues suggests that intact SON might be crucial for normal growth and development. However, the phenotypic effects of deleterious germline variants in SON have not been clearly defined. Herein, we describe seven unrelated individuals with de novo variants in SON and propose that deleterious variants in SON are associated with a severe multisystem disorder characterized by developmental delay, persistent feeding difficulties, and congenital malformations, including brain anomalies. Copyright © 2016 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

Exploring virulence and immunogenicity in the emerging pathogen Sporothrix brasiliensis.

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Della Terra, Paula Portella; Rodrigues, Anderson Messias; Fernandes, Geisa Ferreira; Nishikaku, Angela Satie; Burger, Eva; de Camargo, Zoilo Pires

2017-08-01

Sporotrichosis is a polymorphic chronic infection of humans and animals classically acquired after traumatic inoculation with soil and plant material contaminated with Sporothrix spp. propagules. An alternative and successful route of transmission is bites and scratches from diseased cats, through which Sporothrix yeasts are inoculated into mammalian tissue. The development of a murine model of subcutaneous sporotrichosis mimicking the alternative route of transmission is essential to understanding disease pathogenesis and the development of novel therapeutic strategies. To explore the impact of horizontal transmission in animals (e.g., cat-cat) and zoonotic transmission on Sporothrix fitness, the left hind footpads of BALB/c mice were inoculated with 5×106 yeasts (n = 11 S. brasiliensis, n = 2 S. schenckii, or n = 1 S. globosa). Twenty days post-infection, our model reproduced both the pathophysiology and symptomology of sporotrichosis with suppurating subcutaneous nodules that progressed proximally along lymphatic channels. Across the main pathogenic members of the S. schenckii clade, S. brasiliensis was usually more virulent than S. schenckii and S. globosa. However, the virulence in S. brasiliensis was strain-dependent, and we demonstrated that highly virulent isolates disseminate from the left hind footpad to the liver, spleen, kidneys, lungs, heart, and brain of infected animals, inducing significant and chronic weight loss (losing up to 15% of their body weight). The weight loss correlated with host death between 2 and 16 weeks post-infection. Histopathological features included necrosis, suppurative inflammation, and polymorphonuclear and mononuclear inflammatory infiltrates. Immunoblot using specific antisera and homologous exoantigen investigated the humoral response. Antigenic profiles were isolate-specific, supporting the hypothesis that different Sporothrix species can elicit a heterogeneous humoral response over time, but cross reaction was observed

Defining mental disorder. Exploring the 'natural function' approach.

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Varga, Somogy

2011-01-21

Due to several socio-political factors, to many psychiatrists only a strictly objective definition of mental disorder, free of value components, seems really acceptable. In this paper, I will explore a variant of such an objectivist approach to defining metal disorder, natural function objectivism. Proponents of this approach make recourse to the notion of natural function in order to reach a value-free definition of mental disorder. The exploration of Christopher Boorse's 'biostatistical' account of natural function (1) will be followed an investigation of the 'hybrid naturalism' approach to natural functions by Jerome Wakefield (2). In the third part, I will explore two proposals that call into question the whole attempt to define mental disorder (3). I will conclude that while 'natural function objectivism' accounts fail to provide the backdrop for a reliable definition of mental disorder, there is no compelling reason to conclude that a definition cannot be achieved.

A SNARE-Like Protein and Biotin Are Implicated in Soybean Cyst Nematode Virulence.

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Sadia Bekal

Full Text Available Phytoparasitic nematodes that are able to infect and reproduce on plants that are considered resistant are referred to as virulent. The mechanism(s that virulent nematodes employ to evade or suppress host plant defenses are not well understood. Here we report the use of a genetic strategy (allelic imbalance analysis to associate single nucleotide polymorphisms (SNPs with nematode virulence genes in Heterodera glycines, the soybean cyst nematode (SCN. To accomplish this analysis, a custom SCN SNP array was developed and used to genotype SCN F3-derived populations grown on resistant and susceptible soybean plants. Three SNPs reproducibly showed allele imbalances between nematodes grown on resistant and susceptible plants. Two candidate SCN virulence genes that were tightly linked to the SNPs were identified. One SCN gene encoded biotin synthase (HgBioB, and the other encoded a bacterial-like protein containing a putative SNARE domain (HgSLP-1. The two genes mapped to two different linkage groups. HgBioB contained sequence polymorphisms between avirulent and virulent nematodes. However, the gene encoding HgSLP-1 had reduced copy number in virulent nematode populations and appears to produce multiple forms of the protein via intron retention and alternative splicing. We show that HgSLP-1 is an esophageal-gland protein that is secreted by the nematode during plant parasitism. Furthermore, in bacterial co-expression experiments, HgSLP-1 co-purified with the SCN resistance protein Rhg1 α-SNAP, suggesting that these two proteins physically interact. Collectively our data suggest that multiple SCN genes are involved in SCN virulence, and that HgSLP-1 may function as an avirulence protein and when absent it helps SCN evade host defenses.

Decrease of Staphylococcus aureus Virulence by Helcococcus kunzii in a Caenorhabditis elegans Model.

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Ngba Essebe, Christelle; Visvikis, Orane; Fines-Guyon, Marguerite; Vergne, Anne; Cattoir, Vincent; Lecoustumier, Alain; Lemichez, Emmanuel; Sotto, Albert; Lavigne, Jean-Philippe; Dunyach-Remy, Catherine

2017-01-01

Social bacterial interactions are considered essential in numerous infectious diseases, particularly in wounds. Foot ulcers are a common complication in diabetic patients and these ulcers become frequently infected. This infection is usually polymicrobial promoting cell-to-cell communications. Staphylococcus aureus is the most prevalent pathogen isolated. Its association with Helcococcus kunzii , commensal Gram-positive cocci, is frequently described. The aim of this study was to assess the impact of co-infection on virulence of both H. kunzii and S. aureus strains in a Caenorhabditis elegans model. To study the host response, qRT-PCRs targeting host defense genes were performed. We observed that H. kunzii strains harbored a very low (LT50: 5.7 days ± 0.4) or an absence of virulence (LT50: 6.9 days ± 0.5). In contrast, S. aureus strains (LT50: 2.9 days ± 0.4) were significantly more virulent than all H. kunzii ( P aureus strains were associated, H. kunzii significantly reduced the virulence of the S. aureus strain in nematodes (LT50 between 4.4 and 5.2 days; P aureus led to a strong induction of defense genes ( lys-5, sodh-1 , and cyp-37B1 ) while H. kunzii did not. No statistical difference of host response genes expression was observed when C. elegans were infected with either S. aureus alone or with S. aureus + H. kunzii . Moreover, two well-characterized virulence factors ( hla and agr ) present in S. aureus were down-regulated when S. aureus were co-infected with H. kunzii . This study showed that H. kunzii decreased the virulence of S. aureus without modifying directly the host defense response. Factor(s) produced by this bacterium modulating the staphylococci virulence must be investigated.

Coordinated zinc homeostasis is essential for the wild-type virulence of Brucella abortus.

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Sheehan, Lauren M; Budnick, James A; Roop, R Martin; Caswell, Clayton C

2015-05-01

Metal homeostasis in bacterial cells is a highly regulated process requiring intricately coordinated import and export, as well as precise sensing of intracellular metal concentrations. The uptake of zinc (Zn) has been linked to the virulence of Brucella abortus; however, the capacity of Brucella strains to sense Zn levels and subsequently coordinate Zn homeostasis has not been described. Here, we show that expression of the genes encoding the zinc uptake system ZnuABC is negatively regulated by the Zn-sensing Fur family transcriptional regulator, Zur, by direct interactions between Zur and the promoter region of znuABC. Moreover, the MerR-type regulator, ZntR, controls the expression of the gene encoding the Zn exporter ZntA by binding directly to its promoter. Deletion of zur or zntR alone did not result in increased zinc toxicity in the corresponding mutants; however, deletion of zntA led to increased sensitivity to Zn but not to other metals, such as Cu and Ni, suggesting that ZntA is a Zn-specific exporter. Strikingly, deletion of zntR resulted in significant attenuation of B. abortus in a mouse model of chronic infection, and subsequent experiments revealed that overexpression of zntA in the zntR mutant is the molecular basis for its decreased virulence. The importance of zinc uptake for Brucella pathogenesis has been demonstrated previously, but to date, there has been no description of how overall zinc homeostasis is maintained and genetically controlled in the brucellae. The present work defines the predominant zinc export system, as well as the key genetic regulators of both zinc uptake and export in Brucella abortus. Moreover, the data show the importance of precise coordination of the zinc homeostasis systems as disregulation of some elements of these systems leads to the attenuation of Brucella virulence in a mouse model. Overall, this study advances our understanding of the essential role of zinc in the pathogenesis of intracellular bacteria

Main functions and taxonomic distribution of virulence genes in Brucella melitensis 16 M.

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Aniel Jessica Leticia Brambila-Tapia

Full Text Available Many virulence genes have been detected in attenuated mutants of Brucella melitensis 16 M; nevertheless, a complete report of these genes, including the main Cluster of Orthologous Groups (COG represented as well as the taxonomical distribution among all complete bacterial and archaeal genomes, has not been analyzed. In this work a total of 160 virulence genes that have been reported in attenuated mutants in B. melitensis were included and analyzed. Additionally, we obtained 250 B. melitensis randomly selected genes as a reference group for the taxonomical comparisons. The COGs and the taxonomical distribution profile for 789 nonredundant bacterial and archaeal genomes were obtained and compared with the whole-genome COG distribution and with the 250 randomly selected genes, respectively. The main COGs associated with virulence genes corresponded to the following: intracellular trafficking, secretion and vesicular transport (U; cell motility (N; nucleotide transport and metabolism (F; transcription (K; and cell wall/membrane/envelope biogenesis (M. In addition, we found that virulence genes presented a higher proportion of orthologs in the Euryarchaeota and Proteobacteria phyla, with a significant decrease in Chlamydiae, Bacteroidetes, Tenericutes, Firmicutes and Thermotogae. In conclusion, we found that genes related to specific functions are more relevant to B. melitensis virulence, with the COG U the most significant. Additionally, the taxonomical distribution of virulence genes highlights the importance of these genes in the related Proteobacteria, being less relevant in distant groups of organisms with the exception of Euryarchaeota.

Fast and efficient three-step target-specific curing of a virulence plasmid in Salmonella enterica.

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de Moraes, Marcos H; Teplitski, Max

2015-12-01

Virulence plasmids borne by serovars of Salmonella enterica carry genes involved in its pathogenicity, as well as other functions. Characterization of phenotypes associated with virulence plasmids requires a system for efficiently curing strains of their virulence plasmids. Here, we developed a 3-step protocol for targeted curing of virulence plasmids. The protocol involves insertion of an I-SecI restriction site linked to an antibiotic resistance gene into the target plasmid using λ-Red mutagenesis, followed by the transformation with a temperature-sensitive auxiliary plasmid which carries I-SecI nuclease expressed from a tetracycline-inducible promoter. Finally, the auxiliary plasmid is removed by incubation at 42 °C and the plasmid-less strains are verified on antibiotic-containing media. This method is fast and very efficient: over 90 % of recovered colonies lacked their virulence plasmid.

Studies on the virulence and attenuation of Trypanosoma cruzi using immunodeficient animals

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Basombrío Miguel Ángel

2000-01-01

Full Text Available Tissue invasion and pathology by Trypanosoma cruzi result from an interaction between parasite virulence and host immunity. Successive in vivo generations of the parasite select populations with increasing ability to invade the host. Conversely, prolonged in vitro selection of the parasite produces attenuated sublines with low infectivity for mammals. One such subline (TCC clone has been extensively used in our laboratory as experimental vaccine and tested in comparative experiments with its virulent ancestor (TUL. The experiments here reviewed aimed at the use of immunodeficient mice for testing the infectivity of TCC parasites. It has not been possible to obtain virulent, revertant sublines by prolonged passaged in such mice.

Emergence and genomic diversification of a virulent serogroup W:ST-2881(CC175) Neisseria meningitidis clone in the African meningitis belt.

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Lamelas, Araceli; Hauser, Julia; Dangy, Jean-Pierre; Hamid, Abdul-Wahab M; Röltgen, Katharina; Abdul Sater, Mohamad R; Hodgson, Abraham; Sie, Ali; Junghanss, Thomas; Harris, Simon R; Parkhill, Julian; Bentley, Stephen D; Pluschke, Gerd

2017-08-01

Countries of the African 'meningitis belt' are susceptible to meningococcal meningitis outbreaks. While in the past major epidemics have been primarily caused by serogroup A meningococci, W strains are currently responsible for most of the cases. After an epidemic in Mecca in 2000, W:ST-11 strains have caused many outbreaks worldwide. An unrelated W:ST-2881 clone was described for the first time in 2002, with the first meningitis cases caused by these bacteria reported in 2003. Here we describe results of a comparative whole-genome analysis of 74 W:ST-2881 strains isolated within the framework of two longitudinal colonization and disease studies conducted in Ghana and Burkina Faso. Genomic data indicate that the W:ST-2881 clone has emerged from Y:ST-175(CC175) bacteria by capsule switching. The circulating W:ST-2881 populations were composed of a variety of closely related but distinct genomic variants with no systematic differences between colonization and disease isolates. Two distinct and geographically clustered phylogenetic clonal variants were identified in Burkina Faso and a third in Ghana. On the basis of the presence or absence of 17 recombination fragments, the Ghanaian variant could be differentiated into five clusters. All 25 Ghanaian disease isolates clustered together with 23 out of 40 Ghanaian isolates associated with carriage within one cluster, indicating that W:ST-2881 clusters differ in virulence. More than half of the genes affected by horizontal gene transfer encoded proteins of the 'cell envelope' and the 'transport/binding protein' categories, which indicates that exchange of non-capsular antigens plays an important role in immune evasion.

Identification of Burkholderia cenocepacia strain H111 virulence factors using nonmammalian infection hosts

DEFF Research Database (Denmark)

Schwager, Stephan; Agnoli, Kirsty; Köthe, Manuela

2013-01-01

Burkholderia cenocepacia H111, a strain isolated from a cystic fibrosis patient, has been shown to effectively kill the nematode Caenorhabditis elegans. We used the C. elegans model of infection to screen a mini-Tn5 mutant library of B. cenocepacia H111 for attenuated virulence....... Of the approximately 5,500 B. cenocepacia H111 random mini-Tn5 insertion mutants that were screened, 22 showed attenuated virulence in C. elegans. Except for the quorum-sensing regulator cepR, none of the mutated genes coded for the biosynthesis of classical virulence factors such as extracellular proteases...... or siderophores. Instead, the mutants contained insertions in metabolic and regulatory genes. Mutants attenuated in virulence in the C. elegans infection model were also tested in the Drosophila melanogaster pricking model, and those also attenuated in this model were further tested in Galleria mellonella. Six...

Pathogenicity of Virulent Species of Group C Streptococci in Human

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Marta Kłos

2017-01-01

Full Text Available Group C streptococci (GCS are livestock pathogens and they often cause zoonotic diseases in humans. They are Gram-positive, in mostly β-hemolytic and facultative anaerobes. Because of their close evolutionary kinship with group A streptococci (GAS, GCS share many common virulence factors with GAS and cause a similar range of diseases. Due to the exchange of genetic material with GAS, GCS belong to bacteria that are difficult to be distinguished from group A streptococci; GCS are often treated in microbiological diagnostics as contamination of the culture. This report focuses mainly on the pathogenicity of virulent species of GCS and their association with human diseases. The condition that is most frequently quoted is pharyngitis. In this paper, the virulence factors have also been mentioned and an interesting link has been made between GCS and the pathogenesis of rheumatic diseases among the native people of India and Aboriginal populations.

Phosphotyrosine-Mediated Regulation of Enterohemorrhagic Escherichia coli Virulence

Science.gov (United States)

Robertson, Colin D.; Hazen, Tracy H.; Kaper, James B.

2018-01-01

ABSTRACT Enteric pathogens with low infectious doses rely on the ability to orchestrate the expression of virulence and metabolism-associated genes in response to environmental cues for successful infection. Accordingly, the human pathogen enterohemorrhagic Escherichia coli (EHEC) employs a complex multifaceted regulatory network to link the expression of type III secretion system (T3SS) components to nutrient availability. While phosphorylation of histidine and aspartate residues on two-component system response regulators is recognized as an integral part of bacterial signaling, the involvement of phosphotyrosine-mediated control is minimally explored in Gram-negative pathogens. Our recent phosphotyrosine profiling study of E. coli identified 342 phosphorylated proteins, indicating that phosphotyrosine modifications in bacteria are more prevalent than previously anticipated. The present study demonstrates that tyrosine phosphorylation of a metabolite-responsive LacI/GalR family regulator, Cra, negatively affects T3SS expression under glycolytic conditions that are typical for the colonic lumen environment where production of the T3SS is unnecessary. Our data suggest that Cra phosphorylation affects T3SS expression by modulating the expression of ler, which encodes the major activator of EHEC virulence gene expression. Phosphorylation of the Cra Y47 residue diminishes DNA binding to fine-tune the expression of virulence-associated genes, including those of the locus of enterocyte effacement pathogenicity island that encode the T3SS, and thereby negatively affects the formation of attaching and effacing lesions. Our data indicate that tyrosine phosphorylation provides an additional mechanism to control the DNA binding of Cra and other LacI/GalR family regulators, including LacI and PurR. This study describes an initial effort to unravel the role of global phosphotyrosine signaling in the control of EHEC virulence potential. PMID:29487233

Phosphotyrosine-Mediated Regulation of Enterohemorrhagic Escherichia coli Virulence

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Colin D. Robertson

2018-02-01

Full Text Available Enteric pathogens with low infectious doses rely on the ability to orchestrate the expression of virulence and metabolism-associated genes in response to environmental cues for successful infection. Accordingly, the human pathogen enterohemorrhagic Escherichia coli (EHEC employs a complex multifaceted regulatory network to link the expression of type III secretion system (T3SS components to nutrient availability. While phosphorylation of histidine and aspartate residues on two-component system response regulators is recognized as an integral part of bacterial signaling, the involvement of phosphotyrosine-mediated control is minimally explored in Gram-negative pathogens. Our recent phosphotyrosine profiling study of E. coli identified 342 phosphorylated proteins, indicating that phosphotyrosine modifications in bacteria are more prevalent than previously anticipated. The present study demonstrates that tyrosine phosphorylation of a metabolite-responsive LacI/GalR family regulator, Cra, negatively affects T3SS expression under glycolytic conditions that are typical for the colonic lumen environment where production of the T3SS is unnecessary. Our data suggest that Cra phosphorylation affects T3SS expression by modulating the expression of ler, which encodes the major activator of EHEC virulence gene expression. Phosphorylation of the Cra Y47 residue diminishes DNA binding to fine-tune the expression of virulence-associated genes, including those of the locus of enterocyte effacement pathogenicity island that encode the T3SS, and thereby negatively affects the formation of attaching and effacing lesions. Our data indicate that tyrosine phosphorylation provides an additional mechanism to control the DNA binding of Cra and other LacI/GalR family regulators, including LacI and PurR. This study describes an initial effort to unravel the role of global phosphotyrosine signaling in the control of EHEC virulence potential.

ESX-1-mediated translocation to the cytosol controls virulence of mycobacteria

KAUST Repository

Houben, Diane; Demangel, Caroline; Van Ingen, Jakko; Perez, Jorge; Baldeó n, Lucy R.; Abdallah, Abdallah; Caleechurn, Laxmee; Bottai, Daria; Van Zon, Maaike; De Punder, Karin; Van Der Laan, Tridia; Kant, Arie; Bossers-De Vries, Ruth; Willemsen, Peter Th J; Bitter, Wilbert M.; Van Soolingen, Dick; Brosch, Roland; Van Der Wel, Nicole N.; Peters, Peter J.

2012-01-01

Mycobacterium species, including Mycobacterium tuberculosis and Mycobacterium leprae, are among the most potent human bacterial pathogens. The discovery of cytosolic mycobacteria challenged the paradigm that these pathogens exclusively localize within the phagosome of host cells. As yet the biological relevance of mycobacterial translocation to the cytosol remained unclear. In this current study we used electron microscopy techniques to establish a clear link between translocation and mycobacterial virulence. Pathogenic, patient-derived mycobacteria species were found to translocate to the cytosol, while non-pathogenic species did not. We were further able to link cytosolic translocation with pathogenicity by introducing the ESX-1 (type VII) secretion system into the non-virulent, exclusively phagolysosomal Mycobacterium bovis BCG. Furthermore, we show that translocation is dependent on the C-terminus of the early-secreted antigen ESAT-6. The C-terminal truncation of ESAT-6 was shown to result in attenuation in mice, again linking translocation to virulence. Together, these data demonstrate the molecular mechanism facilitating translocation of mycobacteria. The ability to translocate from the phagolysosome to the cytosol is with this study proven to be biologically significant as it determines mycobacterial virulence. © 2012 Blackwell Publishing Ltd.

ESX-1-mediated translocation to the cytosol controls virulence of mycobacteria

KAUST Repository

Houben, Diane

2012-05-08

Mycobacterium species, including Mycobacterium tuberculosis and Mycobacterium leprae, are among the most potent human bacterial pathogens. The discovery of cytosolic mycobacteria challenged the paradigm that these pathogens exclusively localize within the phagosome of host cells. As yet the biological relevance of mycobacterial translocation to the cytosol remained unclear. In this current study we used electron microscopy techniques to establish a clear link between translocation and mycobacterial virulence. Pathogenic, patient-derived mycobacteria species were found to translocate to the cytosol, while non-pathogenic species did not. We were further able to link cytosolic translocation with pathogenicity by introducing the ESX-1 (type VII) secretion system into the non-virulent, exclusively phagolysosomal Mycobacterium bovis BCG. Furthermore, we show that translocation is dependent on the C-terminus of the early-secreted antigen ESAT-6. The C-terminal truncation of ESAT-6 was shown to result in attenuation in mice, again linking translocation to virulence. Together, these data demonstrate the molecular mechanism facilitating translocation of mycobacteria. The ability to translocate from the phagolysosome to the cytosol is with this study proven to be biologically significant as it determines mycobacterial virulence. © 2012 Blackwell Publishing Ltd.

Targeting Staphylococcus aureus Toxins: A Potential form of Anti-Virulence Therapy

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Cin Kong

2016-03-01

Full Text Available Staphylococcus aureus is an opportunistic pathogen and the leading cause of a wide range of severe clinical infections. The range of diseases reflects the diversity of virulence factors produced by this pathogen. To establish an infection in the host, S. aureus expresses an inclusive set of virulence factors such as toxins, enzymes, adhesins, and other surface proteins that allow the pathogen to survive under extreme conditions and are essential for the bacteria’s ability to spread through tissues. Expression and secretion of this array of toxins and enzymes are tightly controlled by a number of regulatory systems. S. aureus is also notorious for its ability to resist the arsenal of currently available antibiotics and dissemination of various multidrug-resistant S. aureus clones limits therapeutic options for a S. aureus infection. Recently, the development of anti-virulence therapeutics that neutralize S. aureus toxins or block the pathways that regulate toxin production has shown potential in thwarting the bacteria’s acquisition of antibiotic resistance. In this review, we provide insights into the regulation of S. aureus toxin production and potential anti-virulence strategies that target S. aureus toxins.

The Regulatory Small RNA MarS Supports Virulence of Streptococcus pyogenes.

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Pappesch, Roberto; Warnke, Philipp; Mikkat, Stefan; Normann, Jana; Wisniewska-Kucper, Aleksandra; Huschka, Franziska; Wittmann, Maja; Khani, Afsaneh; Schwengers, Oliver; Oehmcke-Hecht, Sonja; Hain, Torsten; Kreikemeyer, Bernd; Patenge, Nadja

2017-09-25

Small regulatory RNAs (sRNAs) play a role in the control of bacterial virulence gene expression. In this study, we investigated an sRNA that was identified in Streptococcus pyogenes (group A Streptococcus, GAS) but is conserved throughout various streptococci. In a deletion strain, expression of mga, the gene encoding the multiple virulence gene regulator, was reduced. Accordingly, transcript and proteome analyses revealed decreased expression of several Mga-activated genes. Therefore, and because the sRNA was shown to interact with the 5' UTR of the mga transcript in a gel-shift assay, we designated it MarS for m ga-activating regulatory sRNA. Down-regulation of important virulence factors, including the antiphagocytic M-protein, led to increased susceptibility of the deletion strain to phagocytosis and reduced adherence to human keratinocytes. In a mouse infection model, the marS deletion mutant showed reduced dissemination to the liver, kidney, and spleen. Additionally, deletion of marS led to increased tolerance towards oxidative stress. Our in vitro and in vivo results indicate a modulating effect of MarS on virulence gene expression and on the pathogenic potential of GAS.

A rabies virus vampire bat variant shows increased neuroinvasiveness in mice when compared to a carnivore variant.

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Mesquita, Leonardo Pereira; Gamon, Thais Helena Martins; Cuevas, Silvia Elena Campusano; Asano, Karen Miyuki; Fahl, Willian de Oliveira; Iamamoto, Keila; Scheffer, Karin Correa; Achkar, Samira Maria; Zanatto, Dennis Albert; Mori, Cláudia Madalena Cabrera; Maiorka, Paulo César; Mori, Enio

2017-12-01

Rabies is one of the most important zoonotic diseases and is caused by several rabies virus (RABV) variants. These variants can exhibit differences in neurovirulence, and few studies have attempted to evaluate the neuroinvasiveness of variants derived from vampire bats and wild carnivores. The aim of this study was to evaluate the neuropathogenesis of infection with two Brazilian RABV street variants (variant 3 and crab-eating fox) in mice. BALB/c mice were inoculated with RABV through the footpad, with the 50% mouse lethal dose (LD 50 ) determined by intracranial inoculation. The morbidity of rabies in mice infected with variant 3 and the crab-eating fox strain was 100% and 50%, respectively, with an incubation period of 7 and 6 days post-inoculation (dpi), respectively. The clinical disease in mice was similar with both strains, and it was characterized initially by weight loss, ruffled fur, hunched posture, and hind limb paralysis progressing to quadriplegia and recumbency at 9 to 12 dpi. Histological lesions within the central nervous system (CNS) characterized by nonsuppurative encephalomyelitis with neuronal degeneration and necrosis were observed in mice infected with variant 3 and those infected with the crab-eating fox variant. However, lesions and the presence of RABV antigen, were more widespread within the CNS of variant-3-infected mice, whereas in crab-eating fox-variant-infected mice, RABV antigens were more restricted to caudal areas of the CNS, such as the spinal cord and brainstem. In conclusion, the results shown here demonstrate that the RABV vampire bat strain (variant 3) has a higher potential for neuroinvasiveness than the carnivore variant.

Peripheral Tissue Involvement in Sporadic, Iatrogenic, and Variant Creutzfeldt-Jakob Disease

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Head, Mark W.; Ritchie, Diane; Smith, Nadine; McLoughlin, Victoria; Nailon, William; Samad, Sazia; Masson, Stephen; Bishop, Matthew; McCardle, Linda; Ironside, James W.

2004-01-01

Human prion diseases are rare fatal neurodegenerative conditions that occur as acquired, familial, or idiopathic disorders. A key event in their pathogenesis is the accumulation of an altered form of the prion protein, termed PrPSc, in the central nervous system. A novel acquired human prion disease, variant Creutzfeldt-Jakob disease, is thought to result from oral exposure to the bovine spongiform encephalopathy agent. This disease differs from other human prion diseases in its neurological, neuropathological, and biochemical phenotype. We have used immunohistochemistry and Western blot techniques to analyze the tissue distribution and biochemical properties of PrPSc in peripheral tissues in a unique series of nine cases of variant Creutzfeldt-Jakob disease. We have compared this with the distribution and biochemical forms found in all of the major subtypes of sporadic Creutzfeldt-Jakob disease and in a case of iatrogenic Creutzfeldt-Jakob disease associated with growth hormone therapy. The results show that involvement of the lymphoreticular system is a defining feature of variant Creutzfeldt-Jakob disease, but that the biochemical isoform of PrPSc found is influenced by the cell type in which it accumulates. PMID:14695328

Technologies and Approaches to Elucidate and Model the Virulence Program of Salmonella.

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McDermott, Jason E.; Yoon, Hyunjin; Nakayasu, Ernesto S.; Metz, Thomas O.; Hyduke, Daniel R.; Kidwai, Afshan S.; Palsson, Bernhard O.; Adkins, Joshua N.; Heffron, Fred

2011-04-01

Salmonella is a primary cause of enteric diseases in a variety of animals. During its evolution into a pathogenic bacterium, Salmonella acquired an elaborate regulatory network that responds to multiple environmental stimuli within host animals and integrates them resulting in fine regulation of the virulence program. The coordinated action by this regulatory network involves numerous virulence regulators, necessitating genome-wide profiling analysis to assess and combine efforts from multiple regulons. In this review we discuss recent high-throughput analytic approaches to understand the regulatory network of Salmonella that controls virulence processes. Application of high-throughput analyses have generated a large amount of data and driven development of computational approaches required for data integration. Therefore, we also cover computer-aided network analyses to infer regulatory networks, and demonstrate how genome-scale data can be used to construct regulatory and metabolic systems models of Salmonella pathogenesis. Genes that are coordinately controlled by multiple virulence regulators under infectious conditions are more likely to be important for pathogenesis. Thus, reconstructing the global regulatory network during infection or, at the very least, under conditions that mimic the host cellular environment not only provides a bird’s eye view of Salmonella survival strategy in response to hostile host environments but also serves as an efficient means to identify novel virulence factors that are essential for Salmonella to accomplish systemic infection in the host.

Eco-reliable path finding in time-variant and stochastic networks

International Nuclear Information System (INIS)

Li, Wenjie; Yang, Lixing; Wang, Li; Zhou, Xuesong; Liu, Ronghui; Gao, Ziyou

2017-01-01

This paper addresses a route guidance problem for finding the most eco-reliable path in time-variant and stochastic networks such that travelers can arrive at the destination with the maximum on-time probability while meeting vehicle emission standards imposed by government regulators. To characterize the dynamics and randomness of transportation networks, the link travel times and emissions are assumed to be time-variant random variables correlated over the entire network. A 0–1 integer mathematical programming model is formulated to minimize the probability of late arrival by simultaneously considering the least expected emission constraint. Using the Lagrangian relaxation approach, the primal model is relaxed into a dualized model which is further decomposed into two simple sub-problems. A sub-gradient method is developed to reduce gaps between upper and lower bounds. Three sets of numerical experiments are tested to demonstrate the efficiency and performance of our proposed model and algorithm. - Highlights: • The most eco-reliable path is defined in time-variant and stochastic networks. • The model is developed with on-time arrival probability and emission constraints. • The sub-gradient and label correcting algorithm are integrated to solve the model. • Numerical experiments demonstrate the effectiveness of developed approaches.

Suspected Lynch syndrome associated MSH6 variants: A functional assay to determine their pathogenicity.

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Hellen Houlleberghs

2017-05-01

Full Text Available Lynch syndrome (LS is a hereditary cancer predisposition caused by inactivating mutations in DNA mismatch repair (MMR genes. Mutations in the MSH6 DNA MMR gene account for approximately 18% of LS cases. Many LS-associated sequence variants are nonsense and frameshift mutations that clearly abrogate MMR activity. However, missense mutations whose functional implications are unclear are also frequently seen in suspected-LS patients. To conclusively diagnose LS and enroll patients in appropriate surveillance programs to reduce morbidity as well as mortality, the functional consequences of these variants of uncertain clinical significance (VUS must be defined. We present an oligonucleotide-directed mutagenesis screen for the identification of pathogenic MSH6 VUS. In the screen, the MSH6 variant of interest is introduced into mouse embryonic stem cells by site-directed mutagenesis. Subsequent selection for MMR-deficient cells using the DNA damaging agent 6-thioguanine (6TG allows the identification of MMR abrogating VUS because solely MMR-deficient cells survive 6TG exposure. We demonstrate the efficacy of the genetic screen, investigate the phenotype of 26 MSH6 VUS and compare our screening results to clinical data from suspected-LS patients carrying these variant alleles.

The importance of virulence prediction and gene networks in microbial risk assessment

DEFF Research Database (Denmark)

Wassenaar, Gertrude Maria; Gamieldien, Junaid; Shatkin, JoAnne

2007-01-01

For microbial risk assessment, it is necessary to recognize and predict Virulence of bacterial pathogens, including their ability to contaminate foods. Hazard characterization requires data on strain variability regarding virulence and survival during food processing. Moreover, information...... and characterization of microbial hazards, including emerging pathogens, in the context of microbial risk assessment....

Intact Protein Analysis at 21 Tesla and X-Ray Crystallography Define Structural Differences in Single Amino Acid Variants of Human Mitochondrial Branched-Chain Amino Acid Aminotransferase 2 (BCAT2)

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Anderson, Lissa C.; Håkansson, Maria; Walse, Björn; Nilsson, Carol L.

2017-09-01

Structural technologies are an essential component in the design of precision therapeutics. Precision medicine entails the development of therapeutics directed toward a designated target protein, with the goal to deliver the right drug to the right patient at the right time. In the field of oncology, protein structural variants are often associated with oncogenic potential. In a previous proteogenomic screen of patient-derived glioblastoma (GBM) tumor materials, we identified a sequence variant of human mitochondrial branched-chain amino acid aminotransferase 2 as a putative factor of resistance of GBM to standard-of-care-treatments. The enzyme generates glutamate, which is neurotoxic. To elucidate structural coordinates that may confer altered substrate binding or activity of the variant BCAT2 T186R, a 45 kDa protein, we applied combined ETD and CID top-down mass spectrometry in a LC-FT-ICR MS at 21 T, and X-Ray crystallography in the study of both the variant and non-variant intact proteins. The combined ETD/CID fragmentation pattern allowed for not only extensive sequence coverage but also confident localization of the amino acid variant to its position in the sequence. The crystallographic experiments confirmed the hypothesis generated by in silico structural homology modeling, that the Lys59 side-chain of BCAT2 may repulse the Arg186 in the variant protein (PDB code: 5MPR), leading to destabilization of the protein dimer and altered enzyme kinetics. Taken together, the MS and novel 3D structural data give us reason to further pursue BCAT2 T186R as a precision drug target in GBM. [Figure not available: see fulltext.

Are secondary metabolites dispensable for virulence?

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The production of toxins by conidial fungal pathogens and their association with virulence has been assumed to occur in vivo and is widely accepted as dogma, but this association has yet to be definitively proven by either genetic or chemical means. Several studies from our labs have used targeted g...

Comparative genome analysis of 24 bovine-associated Staphylococcus isolates with special focus on the putative virulence genes

Science.gov (United States)

Åvall-Jääskeläinen, Silja; Paulin, Lars; Blom, Jochen

2018-01-01

Non-aureus staphylococci (NAS) are most commonly isolated from subclinical mastitis. Different NAS species may, however, have diverse effects on the inflammatory response in the udder. We determined the genome sequences of 20 staphylococcal isolates from clinical or subclinical bovine mastitis, belonging to the NAS species Staphylococcus agnetis, S. chromogenes, and S. simulans, and focused on the putative virulence factor genes present in the genomes. For comparison we used our previously published genome sequences of four S. aureus isolates from bovine mastitis. The pan-genome and core genomes of the non-aureus isolates were characterized. After that, putative virulence factor orthologues were searched in silico. We compared the presence of putative virulence factors in the NAS species and S. aureus and evaluated the potential association between bacterial genotype and type of mastitis (clinical vs. subclinical). The NAS isolates had much less virulence gene orthologues than the S. aureus isolates. One third of the virulence genes were detected only in S. aureus. About 100 virulence genes were present in all S. aureus isolates, compared to about 40 to 50 in each NAS isolate. S. simulans differed the most. Several of the virulence genes detected among NAS were harbored only by S. simulans, but it also lacked a number of genes present both in S. agnetis and S. chromogenes. The type of mastitis was not associated with any specific virulence gene profile. It seems that the virulence gene profiles or cumulative number of different virulence genes are not directly associated with the type of mastitis (clinical or subclinical), indicating that host derived factors such as the immune status play a pivotal role in the manifestation of mastitis. PMID:29610707

Comparative genome analysis of 24 bovine-associated Staphylococcus isolates with special focus on the putative virulence genes

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Silja Åvall-Jääskeläinen

2018-03-01

Full Text Available Non-aureus staphylococci (NAS are most commonly isolated from subclinical mastitis. Different NAS species may, however, have diverse effects on the inflammatory response in the udder. We determined the genome sequences of 20 staphylococcal isolates from clinical or subclinical bovine mastitis, belonging to the NAS species Staphylococcus agnetis, S. chromogenes, and S. simulans, and focused on the putative virulence factor genes present in the genomes. For comparison we used our previously published genome sequences of four S. aureus isolates from bovine mastitis. The pan-genome and core genomes of the non-aureus isolates were characterized. After that, putative virulence factor orthologues were searched in silico. We compared the presence of putative virulence factors in the NAS species and S. aureus and evaluated the potential association between bacterial genotype and type of mastitis (clinical vs. subclinical. The NAS isolates had much less virulence gene orthologues than the S. aureus isolates. One third of the virulence genes were detected only in S. aureus. About 100 virulence genes were present in all S. aureus isolates, compared to about 40 to 50 in each NAS isolate. S. simulans differed the most. Several of the virulence genes detected among NAS were harbored only by S. simulans, but it also lacked a number of genes present both in S. agnetis and S. chromogenes. The type of mastitis was not associated with any specific virulence gene profile. It seems that the virulence gene profiles or cumulative number of different virulence genes are not directly associated with the type of mastitis (clinical or subclinical, indicating that host derived factors such as the immune status play a pivotal role in the manifestation of mastitis.

The Composition and Spatial Patterns of Bacterial Virulence Factors and Antibiotic Resistance Genes in 19 Wastewater Treatment Plants.

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Bing Zhang

Full Text Available Bacterial pathogenicity and antibiotic resistance are of concern for environmental safety and public health. Accumulating evidence suggests that wastewater treatment plants (WWTPs are as an important sink and source of pathogens and antibiotic resistance genes (ARGs. Virulence genes (encoding virulence factors are good indicators for bacterial pathogenic potentials. To achieve a comprehensive understanding of bacterial pathogenic potentials and antibiotic resistance in WWTPs, bacterial virulence genes and ARGs in 19 WWTPs covering a majority of latitudinal zones of China were surveyed by using GeoChip 4.2. A total of 1610 genes covering 13 virulence factors and 1903 genes belonging to 11 ARG families were detected respectively. The bacterial virulence genes exhibited significant spatial distribution patterns of a latitudinal biodiversity gradient and a distance-decay relationship across China. Moreover, virulence genes tended to coexist with ARGs as shown by their strongly positive associations. In addition, key environmental factors shaping the overall virulence gene structure were identified. This study profiles the occurrence, composition and distribution of virulence genes and ARGs in current WWTPs in China, and uncovers spatial patterns and important environmental variables shaping their structure, which may provide the basis for further studies of bacterial virulence factors and antibiotic resistance in WWTPs.

Genetic Diversity of Tick-Borne Rickettsial Pathogens; Insights Gained from Distant Strains

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Sebastián Aguilar Pierlé

2014-01-01

Full Text Available The ability to capture genetic variation with unprecedented resolution improves our understanding of bacterial populations and their ability to cause disease. The goal of the pathogenomics era is to define genetic diversity that results in disease. Despite the economic losses caused by vector-borne bacteria in the Order Rickettsiales, little is known about the genetic variants responsible for observed phenotypes. The tick-transmitted rickettsial pathogen Anaplasma marginale infects cattle in tropical and subtropical regions worldwide, including Australia. Genomic analysis of North American A. marginale strains reveals a closed core genome defined by high levels of Single Nucleotide Polymorphisms (SNPs. Here we report the first genome sequences and comparative analysis for Australian strains that differ in virulence and transmissibility. A list of genetic differences that segregate with phenotype was evaluated for the ability to distinguish the attenuated strain from virulent field strains. Phylogenetic analyses of the Australian strains revealed a marked evolutionary distance from all previously sequenced strains. SNP analysis showed a strikingly reduced genetic diversity between these strains, with the smallest number of SNPs detected between any two A. marginale strains. The low diversity between these phenotypically distinct bacteria presents a unique opportunity to identify the genetic determinants of virulence and transmission.

Validation of a Novel Immunoline Assay for Patient Stratification according to Virulence of the Infecting Helicobacter pylori Strain and Eradication Status

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Luca Formichella

2017-01-01

Full Text Available Helicobacter pylori infection shows a worldwide prevalence of around 50%. However, only a minority of infected individuals develop clinical symptoms or diseases. The presence of H. pylori virulence factors, such as CagA and VacA, has been associated with disease development, but assessment of virulence factor presence requires gastric biopsies. Here, we evaluate the H. pylori recomLine test for risk stratification of infected patients by comparing the test score and immune recognition of type I or type II strains defined by the virulence factors CagA, VacA, GroEL, UreA, HcpC, and gGT with patient’s disease status according to histology. Moreover, the immune responses of eradicated individuals from two different populations were analysed. Their immune response frequencies and intensities against all antigens except CagA declined below the detection limit. CagA was particularly long lasting in both independent populations. An isolated CagA band often represents past eradication with a likelihood of 88.7%. In addition, a high recomLine score was significantly associated with high-grade gastritis, atrophy, intestinal metaplasia, and gastric cancer. Thus, the recomLine is a sensitive and specific noninvasive test for detecting serum responses against H. pylori in actively infected and eradicated individuals. Moreover, it allows stratifying patients according to their disease state.

Genetic variants of genital mycoplasmas and their relation to the clinical course of inflammatory diseases of the urogenital system in women

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M. R. Rakhmatulina

2014-01-01

Full Text Available Goal of the study. To study genetic variability of M. hominis (based on the vaa gene and M. genitalium (based on the mg192 gene derived from biological material samples taken from women with different clinical manifestations of inflammatory diseases of the urogenital system and clinically healthy women (for M. hominis. Materials and methods. Genetic variability of twenty M. hominis samples taken from patients with inflammatory diseases of the urogenital system and twenty M. hominis samples taken from patients without clinical and laboratory signs of inflammatory processes of the urogenital system was studied by the sequence analysis method. Genetic variability of eight M. genitalium samples taken from patients with different clinical signs of inflammatory diseases of the urogenital system was also examined by the sequence analysis method. Results. Three genetic variants of M. hominis based on the vaa gene were found; variant I was revealed more often in patients with clinical manifestations of inflammatory diseases (65.0%, and variant II - in clinically healthy women (60.0%. Three phylogenetic M. gentium groups based on the mg192 gene were revealed; two samples were referred to Groups I and II, and four samples were referred to Group III. Samples from each phylogenetic groups were taken from patients with clinical and laboratory manifestations of cervicitis and urethritis. Conclusion. The study data demonstrate a potential effect of the VAA surface protein on the virulence of opportunistic M. hominis pathogens.

Common and Rare Variant Association Study for Plasma Lipids and Coronary Artery Disease.

Science.gov (United States)

Tada, Hayato; Kawashiri, Masa-aki; Konno, Tetsuo; Yamagishi, Masakazu; Hayashi, Kenshi

2016-01-01

Blood lipid levels are highly heritable and modifiable risk factors for coronary artery disease (CAD), and are the leading cause of death worldwide. These facts have motivated human genetic association studies that have the substantial potential to define the risk factors that are causal and to identify pathways and therapeutic targets for lipids and CAD.The success of the HapMap project that provided an extensive catalog of human genetic variations and the development of microarray based genotyping chips (typically containing variations with allele frequencies ＞ 5%) facilitated common variant association study (CVAS; formerly termed genome-wide association study, GWAS) identifying disease-associated variants in a genome-wide manner. To date, 157 loci associated with blood lipids and 46 loci with CAD have been successfully identified, accounting for approximately 12%-14% of heritability for lipids and 10% of heritability for CAD. However, there is yet a major challenge termed "missing heritability problem," namely the observation that loci detected by CVAS explain only a small fraction of the inferred genetic variations. To explain such missing portions, focuses in genetic association studies have shifted from common to rare variants. However, it is challenging to apply rare variant association study (RVAS) in an unbiased manner because such variants typically lack the sufficient number to be identified statistically.In this review, we provide a current understanding of the genetic architecture mostly derived from CVAS, and several updates on the progress and limitations of RVAS for lipids and CAD.

Heterozygous genotype at codon 129 correlates with prolonged disease course in Heidenhain variant sporadic CJD: case report.

Science.gov (United States)

Townley, Ryan A; Dawson, Elliot T; Drubach, Daniel A

2018-02-01

Sporadic Creutzfeldt-Jakob disease (sCJD) is a rapid and fatal neurodegenerative disease defined by misfolded prion proteins accumulating in the brain. A minority of cases initially present with posterior cortical atrophy (PCA) phenotype, also known as Heidenhain variant or visual variant CJD. This case provides further evidence of sCJD presenting as PCA. The case also provides evidence for early DWI changes and cortical atrophy over 30 months before neurologic decline and subsequent death. The prolonged disease course correlates with prion protein codon 129 heterozygosity and coexistence of multiple prion strains.

Variants of cellobiohydrolases

Energy Technology Data Exchange (ETDEWEB)

Bott, Richard R.; Foukaraki, Maria; Hommes, Ronaldus Wilhelmus; Kaper, Thijs; Kelemen, Bradley R.; Kralj, Slavko; Nikolaev, Igor; Sandgren, Mats; Van Lieshout, Johannes Franciscus Thomas; Van Stigt Thans, Sander

2018-04-10

Disclosed are a number of homologs and variants of Hypocrea jecorina Ce17A (formerly Trichoderma reesei cellobiohydrolase I or CBH1), nucleic acids encoding the same and methods for producing the same. The homologs and variant cellulases have the amino acid sequence of a glycosyl hydrolase of family 7A wherein one or more amino acid residues are substituted and/or deleted.

Yersinia enterocolitica: Mode of Transmission, Molecular Insights of Virulence, and Pathogenesis of Infection

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Yeasmin Sabina

2011-01-01

Full Text Available Although Yersinia enterocolitica is usually transmitted through contaminated food and untreated water, occasional transmission such as human-to-human, animal-to-human and blood transfusion associated transmission have also identified in human disease. Of the six Y. enterocolitica biotypes, the virulence of the pathogenic biotypes, namely, 1B and 2–5 is attributed to the presence of a highly conserved 70-kb virulence plasmid, termed pYV/pCD and certain chromosomal genes. Some biotype 1A strains, despite lacking virulence plasmid (pYV and traditional chromosomal virulence genes, are isolated frequently from humans with gastrointestinal diseases similar to that produced by isolates belonging known pathogenic biotypes. Y. enterocolitica pathogenic biotypes have evolved two major properties: the ability to penetrate the intestinal wall, which is thought to be controlled by plasmid genes, and the production of heat-stable enterotoxin, which is controlled by chromosomal genes.

Bottlenecks and Hubs in Inferred Networks Are Important for Virulence in Salmonella typhimurium

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McDermott, Jason E.; Taylor, Ronald C.; Yoon, Hyunjin; Heffron, Fred

2009-02-01

Recent advances in experimental methods have provided sufficient data to consider systems as large networks of interconnected components. High-throughput determination of protein-protein interaction networks has led to the observation that topological bottlenecks, that is proteins defined by high centrality in the network, are enriched in proteins with systems-level phenotypes such as essentiality. Global transcriptional profiling by microarray analysis has been used extensively to characterize systems, for example, cellular response to environmental conditions and genetic mutations. These transcriptomic datasets have been used to infer regulatory and functional relationship networks based on co-regulation. We use the context likelihood of relatedness (CLR) method to infer networks from two datasets gathered from the pathogen Salmonella typhimurium; one under a range of environmental culture conditions and the other from deletions of 15 regulators found to be essential in virulence. Bottleneck nodes were identified from these inferred networks and we show that these nodes are significantly more likely to be essential for virulence than their non-bottleneck counterparts. A network generated using Pearson correlation did not display this behavior. Overall this study demonstrates that topology of networks inferred from global transcriptional profiles provides information about the systems-level roles of bottleneck genes. Analysis of the differences between the two CLR-derived networks suggests that the bottleneck nodes are either mediators of transitions between system states or sentinels that reflect the dynamics of these transitions.

Do pathogens become more virulent as they spread? Evidence from the amphibian declines in Central America.

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Phillips, Ben L; Puschendorf, Robert

2013-09-07

The virulence of a pathogen can vary strongly through time. While cyclical variation in virulence is regularly observed, directional shifts in virulence are less commonly observed and are typically associated with decreasing virulence of biological control agents through coevolution. It is increasingly appreciated, however, that spatial effects can lead to evolutionary trajectories that differ from standard expectations. One such possibility is that, as a pathogen spreads through a naive host population, its virulence increases on the invasion front. In Central America, there is compelling evidence for the recent spread of pathogenic Batrachochytrium dendrobatidis (Bd) and for its strong impact on amphibian populations. Here, we re-examine data on Bd prevalence and amphibian population decline across 13 sites from southern Mexico through Central America, and show that, in the initial phases of the Bd invasion, amphibian population decline lagged approximately 9 years behind the arrival of the pathogen, but that this lag diminished markedly over time. In total, our analysis suggests an increase in Bd virulence as it spread southwards, a pattern consistent with rapid evolution of increased virulence on Bd's invading front. The impact of Bd on amphibians might therefore be driven by rapid evolution in addition to more proximate environmental drivers.

Feeding behaviour of Caenorhabditis elegans is an indicator of Pseudomonas aeruginosa PAO1 virulence

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Shawn Lewenza

2014-08-01

Full Text Available Caenorhabditis elegans is commonly used as an infection model for pathogenesis studies in Pseudomonas aeruginosa. The standard virulence assays rely on the slow and fast killing or paralysis of nematodes but here we developed a behaviour assay to monitor the preferred bacterial food sources of C. elegans. We monitored the food preferences of nematodes fed the wild type PAO1 and mutants in the type III secretion (T3S system, which is a conserved mechanism to inject secreted effectors into the host cell cytosol. A ΔexsEΔpscD mutant defective for type III secretion served as a preferred food source, while an ΔexsE mutant that overexpresses the T3S effectors was avoided. Both food sources were ingested and observed in the gastrointestinal tract. Using the slow killing assay, we showed that the ΔexsEΔpscD had reduced virulence and thus confirmed that preferred food sources are less virulent than the wild type. Next we developed a high throughput feeding behaviour assay with 48 possible food colonies in order to screen a transposon mutant library and identify potential virulence genes. C. elegans identified and consumed preferred food colonies from a grid of 48 choices. The mutants identified as preferred food sources included known virulence genes, as well as novel genes not identified in previous C. elegans infection studies. Slow killing assays were performed and confirmed that several preferred food sources also showed reduced virulence. We propose that C. elegans feeding behaviour can be used as a sensitive indicator of virulence for P. aeruginosa PAO1.

Computer-aided identification of polymorphism sets diagnostic for groups of bacterial and viral genetic variants

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Huygens Flavia

2007-08-01

Full Text Available Abstract Background Single nucleotide polymorphisms (SNPs and genes that exhibit presence/absence variation have provided informative marker sets for bacterial and viral genotyping. Identification of marker sets optimised for these purposes has been based on maximal generalized discriminatory power as measured by Simpson's Index of Diversity, or on the ability to identify specific variants. Here we describe the Not-N algorithm, which is designed to identify small sets of genetic markers diagnostic for user-specified subsets of known genetic variants. The algorithm does not treat the user-specified subset and the remaining genetic variants equally. Rather Not-N analysis is designed to underpin assays that provide 0% false negatives, which is very important for e.g. diagnostic procedures for clinically significant subgroups within microbial species. Results The Not-N algorithm has been incorporated into the "Minimum SNPs" computer program and used to derive genetic markers diagnostic for multilocus sequence typing-defined clonal complexes, hepatitis C virus (HCV subtypes, and phylogenetic clades defined by comparative genome hybridization (CGH data for Campylobacter jejuni, Yersinia enterocolitica and Clostridium difficile. Conclusion Not-N analysis is effective for identifying small sets of genetic markers diagnostic for microbial sub-groups. The best results to date have been obtained with CGH data from several bacterial species, and HCV sequence data.

Ecto-5′-Nucleotidase: A Candidate Virulence Factor in Streptococcus sanguinis Experimental Endocarditis

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Fan, Jingyuan; Zhang, Yongshu; Chuang-Smith, Olivia N.; Frank, Kristi L.; Guenther, Brian D.; Kern, Marissa; Schlievert, Patrick M.; Herzberg, Mark C.

2012-01-01

Streptococcus sanguinis is the most common cause of infective endocarditis (IE). Since the molecular basis of virulence of this oral commensal bacterium remains unclear, we searched the genome of S. sanguinis for previously unidentified virulence factors. We identified a cell surface ecto-5′-nucleotidase (Nt5e), as a candidate virulence factor. By colorimetric phosphate assay, we showed that S. sanguinis Nt5e can hydrolyze extracellular adenosine triphosphate to generate adenosine. Moreover, a nt5e deletion mutant showed significantly shorter lag time (PS. sanguinis caused IE (4 d) in a rabbit model with significantly decreased mass of vegetations (PS. sanguinis in vivo. As a virulence factor, Nt5e may function by (i) hydrolyzing ATP, a pro-inflammatory molecule, and generating adenosine, an immunosuppressive molecule to inhibit phagocytic monocytes/macrophages associated with valvular vegetations. (ii) Nt5e-mediated inhibition of platelet aggregation could also delay presentation of platelet microbicidal proteins to infecting bacteria on heart valves. Both plausible Nt5e-dependent mechanisms would promote survival of infecting S. sanguinis. In conclusion, we now show for the first time that streptococcal Nt5e modulates S. sanguinis-induced platelet aggregation and may contribute to the virulence of streptococci in experimental IE. PMID:22685551

Ancient mtDNA genetic variants modulate mtDNA transcription and replication.

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Sarit Suissa

2009-05-01

Full Text Available Although the functional consequences of mitochondrial DNA (mtDNA genetic backgrounds (haplotypes, haplogroups have been demonstrated by both disease association studies and cell culture experiments, it is not clear which of the mutations within the haplogroup carry functional implications and which are "evolutionary silent hitchhikers". We set forth to study the functionality of haplogroup-defining mutations within the mtDNA transcription/replication regulatory region by in vitro transcription, hypothesizing that haplogroup-defining mutations occurring within regulatory motifs of mtDNA could affect these processes. We thus screened >2500 complete human mtDNAs representing all major populations worldwide for natural variation in experimentally established protein binding sites and regulatory regions comprising a total of 241 bp in each mtDNA. Our screen revealed 77/241 sites showing point mutations that could be divided into non-fixed (57/77, 74% and haplogroup/sub-haplogroup-defining changes (i.e., population fixed changes, 20/77, 26%. The variant defining Caucasian haplogroup J (C295T increased the binding of TFAM (Electro Mobility Shift Assay and the capacity of in vitro L-strand transcription, especially of a shorter transcript that maps immediately upstream of conserved sequence block 1 (CSB1, a region associated with RNA priming of mtDNA replication. Consistent with this finding, cybrids (i.e., cells sharing the same nuclear genetic background but differing in their mtDNA backgrounds harboring haplogroup J mtDNA had a >2 fold increase in mtDNA copy number, as compared to cybrids containing haplogroup H, with no apparent differences in steady state levels of mtDNA-encoded transcripts. Hence, a haplogroup J regulatory region mutation affects mtDNA replication or stability, which may partially account for the phenotypic impact of this haplogroup. Our analysis thus demonstrates, for the first time, the functional impact of particular mt

A Salmonella typhimurium-translocated Glycerophospholipid:Cholesterol Acyltransferase Promotes Virulence by Binding to the RhoA Protein Switch Regions

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LaRock, Doris L.; Brzovic, Peter S.; Levin, Itay; Blanc, Marie-Pierre; Miller, Samuel I.

2012-08-24

Salmonella enterica serovar typhimurium translocates a glycerophospholipid: cholesterol acyltransferase (SseJ) into the host cytosol after its entry into mammalian cells. SseJ is recruited to the cytoplasmic face of the host cell phagosome membrane where it is activated upon binding the small GTPase, RhoA. SseJ is regulated similarly to cognate eukaryotic effectors, as only the GTP-bound form of RhoA family members stimulates enzymatic activity. Using NMR and biochemistry, this work demonstrates that SseJ competes effectively with Rhotekin, ROCK, and PKN1 in binding to a similar RhoA surface. The RhoA surface that binds SseJ includes the regulatory switch regions that control activation of mammalian effectors. These data were used to create RhoA mutants with altered SseJ binding and activation. This structure-function analysis supports a model in which SseJ activation occurs predominantly through binding to residues within switch region II. We further defined the nature of the interaction between SseJ and RhoA by constructing SseJ mutants in the RhoA binding surface. These data indicate that SseJ binding to RhoA is required for recruitment of SseJ to the endosomal network and for full Salmonella virulence for inbred susceptible mice, indicating that regulation of SseJ by small GTPases is an important virulence strategy of this bacterial pathogen. The dependence of a bacterial effector on regulation by a mammalian GTPase defines further how intimately host pathogen interactions have coevolved through similar and divergent evolutionary strategies.

Inactivation of DNA mismatch repair by variants of uncertain significance in the PMS2 gene.

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Drost, Mark; Koppejan, Hester; de Wind, Niels

2013-11-01

Lynch syndrome (LS) is a common cancer predisposition caused by an inactivating mutation in one of four DNA mismatch repair (MMR) genes. Frequently a variant of uncertain significance (VUS), rather than an obviously pathogenic mutation, is identified in one of these genes. The inability to define pathogenicity of such variants precludes targeted healthcare. Here, we have modified a cell-free assay to test VUS in the MMR gene PMS2 for functional activity. We have analyzed nearly all VUS in PMS2 found thus far and describe loss of MMR activity for five, suggesting the applicability of the assay for diagnosis of LS. © 2013 WILEY PERIODICALS, INC.

Characterization of putative virulence factors of Serratia marcescens strain SEN for pathogenesis in Spodoptera litura.

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Aggarwal, Chetana; Paul, Sangeeta; Tripathi, Vishwas; Paul, Bishwajeet; Khan, Md Aslam

2017-02-01

Two Serratia marcescens strains, SEN and ICC-4, isolated from diseased insect cadavers were observed to differ considerably in their virulence towards Spodoptera litura. The present study was aimed to characterize the possible virulence factors present in the virulent Serratia marcescens strain SEN. Both the S. marcescens strains were evaluated for the presence of various lytic enzymes such as chitinase, lipase, protease and phospholipase. The virulent S. marcescens strain SEN was observed to possess considerably higher activity of chitinase and protease enzymes; activity of phospholipase enzyme was also higher. Although, all the three toxin genes shlA, phlA and swr could be detected in both the S. marcescens strains, there was a higher expression of these genes in the virulent strain SEN. S. marcescens strain ICC-4 showed greater reduction in overall growth yield in the post-exponential phase in the presence of midgut juice and hemolymph of S. litura larvae, as compared to S. marcescens strain SEN. Proliferation of the S. marcescens strain SEN was also considerably higher in foregut, midgut and hemolymph of S. litura larvae, as compared to strain ICC-4. Peritrophic membrane treated with broth culture of the S. marcescens strain SEN showed higher damage as compared to strain ICC-4. The peritrophic membrane of larvae fed on diet treated with the virulent strain showed considerable damage while the peritrophic membrane of larvae fed on diet treated with the non-virulent strain showed no damage. This is the first report documenting the fate of ingested S. marcescens in S. litura gut and the relative expression of toxin genes from two S. marcescens strains differing in their virulence towards S. litura. Copyright © 2016 Elsevier Inc. All rights reserved.

Defining mental disorder. Exploring the 'natural function' approach

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Varga Somogy

2011-01-01

Full Text Available Abstract Due to several socio-political factors, to many psychiatrists only a strictly objective definition of mental disorder, free of value components, seems really acceptable. In this paper, I will explore a variant of such an objectivist approach to defining metal disorder, natural function objectivism. Proponents of this approach make recourse to the notion of natural function in order to reach a value-free definition of mental disorder. The exploration of Christopher Boorse's 'biostatistical' account of natural function (1 will be followed an investigation of the 'hybrid naturalism' approach to natural functions by Jerome Wakefield (2. In the third part, I will explore two proposals that call into question the whole attempt to define mental disorder (3. I will conclude that while 'natural function objectivism' accounts fail to provide the backdrop for a reliable definition of mental disorder, there is no compelling reason to conclude that a definition cannot be achieved.

Virulence marker candidates in N-protein of viral haemorrhagic septicaemia virus (VHSV): virulence variability within VHSV Ib clones

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Ito, Takafumi; Kurita, Jun; Mori, Koh-ichiro

2018-01-01

, upon cloning by limited dilution, both isolates appeared to be heterogeneous in terms of reactivity with nucleo (N)-protein-specific MAbs as well their gene sequences. Infection trials in rainbow trout further revealed differences in the virulence of these virus clones derived from the same primary...

Wide distribution of virulence genes among Enterococcus faecium and Enterococcus faecalis clinical isolates.

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Soheili, Sara; Ghafourian, Sobhan; Sekawi, Zamberi; Neela, Vasanthakumari; Sadeghifard, Nourkhoda; Ramli, Ramliza; Hamat, Rukman Awang

2014-01-01

Enterococcus, a Gram-positive facultative anaerobic cocci belonging to the lactic acid bacteria of the phylum Firmicutes, is known to be able to resist a wide range of hostile conditions such as different pH levels, high concentration of NaCl (6.5%), and the extended temperatures between 5(°)C and 65(°)C. Despite being the third most common nosocomial pathogen, our understanding on its virulence factors is still poorly understood. The current study was aimed to determine the prevalence of different virulence genes in Enterococcus faecalis and Enterococcus faecium. For this purpose, 79 clinical isolates of Malaysian enterococci were evaluated for the presence of virulence genes. pilB, fms8, efaAfm, and sgrA genes are prevalent in all clinical isolates. In conclusion, the pathogenicity of E. faecalis and E. faecium could be associated with different virulence factors and these genes are widely distributed among the enterococcal species.

Wide Distribution of Virulence Genes among Enterococcus faecium and Enterococcus faecalis Clinical Isolates

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Sara Soheili

2014-01-01

Full Text Available Enterococcus, a Gram-positive facultative anaerobic cocci belonging to the lactic acid bacteria of the phylum Firmicutes, is known to be able to resist a wide range of hostile conditions such as different pH levels, high concentration of NaCl (6.5%, and the extended temperatures between 5°C and 65°C. Despite being the third most common nosocomial pathogen, our understanding on its virulence factors is still poorly understood. The current study was aimed to determine the prevalence of different virulence genes in Enterococcus faecalis and Enterococcus faecium. For this purpose, 79 clinical isolates of Malaysian enterococci were evaluated for the presence of virulence genes. pilB, fms8, efaAfm, and sgrA genes are prevalent in all clinical isolates. In conclusion, the pathogenicity of E. faecalis and E. faecium could be associated with different virulence factors and these genes are widely distributed among the enterococcal species.

Genome-wide screen of Pseudomonas aeruginosa In Saccharomyces cerevisiae identifies new virulence factors

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Rafat eZrieq

2015-11-01

Full Text Available Pseudomonas aeruginosa is a human opportunistic pathogen that causes mortality in cystic fibrosis and immunocompromised patients. While many virulence factors of this pathogen have already been identified, several remain to be discovered. In this respect we set an unprecedented genome-wide screen of a P. aeruginosa expression library based on a yeast growth phenotype. 51 candidates were selected in a three-round screening process. The robustness of the screen was validated by the selection of three well known secreted proteins including one demonstrated virulence factor, the protease LepA. Further in silico sorting of the 51 candidates highlighted three potential new Pseudomonas effector candidates (Pec. By testing the cytotoxicity of wild type P. aeruginosa vs pec mutants towards macrophages and the virulence in the Caenorhabditis elegans model, we demonstrated that the three selected Pecs are novel virulence factors of P. aeruginosa. Additional cellular localization experiments in the host revealed specific localization for Pec1 and Pec2 that could inform about their respective functions.

Tropical calcific pancreatitis and its association with CTRC and SPINK1 (p.N34S) variants.

NARCIS (Netherlands)

Derikx, M.H.; Szmola, R.; Morsche, R.H.M. te; Sunderasan, S.; Chacko, A.; Drenth, J.P.H.

2009-01-01

BACKGROUND: Tropical calcific pancreatitis (TCP) is a relatively common form of chronic pancreatitis in parts of Asia and Africa. The SPINK1 variant p.N34S is strongly associated with TCP, but other genetic factors remain to be defined. Chymotrypsinogen C (CTRC) degrades trypsinogen and

The animal model determines the results of Aeromonas virulence factors

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Alejandro Romero

2016-10-01

Full Text Available The selection of an experimental animal model is of great importance in the study of bacterial virulence factors. Here, a bath infection of zebrafish larvae is proposed as an alternative model to study the virulence factors of A. hydrophila. Intraperitoneal infections in mice and trout were compared with bath infections in zebrafish larvae using specific mutants. The great advantage of this model is that bath immersion mimics the natural route of infection, and injury to the tail also provides a natural portal of entry for the bacteria. The implication of T3SS in the virulence of A. hydrophila was analysed using the AH-1::aopB mutant. This mutant was less virulent than the wild-type strain when inoculated into zebrafish larvae, as described in other vertebrates. However, the zebrafish model exhibited slight differences in mortality kinetics only observed using invertebrate models. Infections using the mutant AH-1∆vapA lacking the gene coding for the surface S-layer suggested that this protein was not totally necessary to the bacteria once it was inside the host, but it contributed to the inflammatory response. Only when healthy zebrafish larvae were infected did the mutant produce less mortality than the wild type. Variations between models were evidenced using the AH-1∆rmlB, which lacks the O-antigen lipopolysaccharide (LPS, and the AH-1∆wahD, which lacks the O-antigen LPS and part of the LPS outer-core. Both mutants showed decreased mortality in all of the animal models, but the differences between them were only observed in injured zebrafish larvae, suggesting that residues from the LPS outer core must be important for virulence. The greatest differences were observed using the AH-1ΔFlaB-J (lacking polar flagella and unable to swim and the AH-1::motX (non-motile but producing flagella. They were as pathogenic as the wild-type strain when injected into mice and trout, but no mortalities were registered in zebrafish larvae. This study

Role of Arf GTPases in fungal morphogenesis and virulence.

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Hayet Labbaoui

2017-02-01

Full Text Available Virulence of the human fungal pathogen Candida albicans depends on the switch from budding to filamentous growth, which requires sustained membrane traffic and polarized growth. In many organisms, small GTPases of the Arf (ADP-ribosylation factor family regulate membrane/protein trafficking, yet little is known about their role in fungal filamentous growth. To investigate these GTPases in C. albicans, we generated loss of function mutants in all 3 Arf proteins, Arf1-Arf3, and 2 Arf-like proteins, Arl1 and Arl3. Our results indicate that of these proteins, Arf2 is required for viability and sensitivity to antifungal drugs. Repressible ARF2 expression results in defects in filamentous growth, cell wall integrity and virulence, likely due to alteration of the Golgi. Arl1 is also required for invasive filamentous growth and, although arl1/arl1 cells can initiate hyphal growth, hyphae are substantially shorter than that of the wild-type, due to the inability of this mutant to maintain hyphal growth at a single site. We show that this defect does not result from an alteration of phospholipid distribution and is unlikely to result from the sole Golgin Imh1 mislocalization, as Imh1 is not required for invasive filamentous growth. Rather, our results suggest that the arl1/arl1 hyphal growth defect results from increased secretion in this mutant. Strikingly, the arl1/arl1 mutant is drastically reduced in virulence during oropharyngeal candidiasis. Together, our results highlight the importance of Arl1 and Arf2 as key regulators of hyphal growth and virulence in C. albicans and identify a unique function of Arl1 in secretion.

Catabolite and Oxygen Regulation of Enterohemorrhagic Escherichia coli Virulence

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Kimberly M. Carlson-Banning

2016-11-01

Full Text Available The biogeography of the gut is diverse in its longitudinal axis, as well as within specific microenvironments. Differential oxygenation and nutrient composition drive the membership of microbial communities in these habitats. Moreover, enteric pathogens can orchestrate further modifications to gain a competitive advantage toward host colonization. These pathogens are versatile and adept when exploiting the human colon. They expertly navigate complex environmental cues and interkingdom signaling to colonize and infect their hosts. Here we demonstrate how enterohemorrhagic Escherichia coli (EHEC uses three sugar-sensing transcription factors, Cra, KdpE, and FusR, to exquisitely regulate the expression of virulence factors associated with its type III secretion system (T3SS when exposed to various oxygen concentrations. We also explored the effect of mucin-derived nonpreferred carbon sources on EHEC growth and expression of virulence genes. Taken together, the results show that EHEC represses the expression of its T3SS when oxygen is absent, mimicking the largely anaerobic lumen, and activates its T3SS when oxygen is available through Cra. In addition, when EHEC senses mucin-derived sugars heavily present in the O-linked and N-linked glycans of the large intestine, virulence gene expression is initiated. Sugars derived from pectin, a complex plant polysaccharide digested in the large intestine, also increased virulence gene expression. Not only does EHEC sense host- and microbiota-derived interkingdom signals, it also uses oxygen availability and mucin-derived sugars liberated by the microbiota to stimulate expression of the T3SS. This precision in gene regulation allows EHEC to be an efficient pathogen with an extremely low infectious dose.

Virulence Factors Associated with Pediatric Shigellosis in Brazilian Amazon

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Carolinie Batista Nobre da Cruz

2014-01-01

Full Text Available Shigellosis is a global human health problem and the incidence is highest among children. In the present work, main Shigella virulence genes was examined by PCR and compared to symptoms of pediatric shigellosis. Thirty Shigella isolates were identified from an etiologic study at which 1,339 children ranging 0–10 years old were enrolled. S. flexneri was the most frequent species reaching 60.0% of isolates, 22.2% were S. sonnei, and 6.6% were both S. dysenteriae and S. boydii. All Shigella infected children had diarrhea, but not all were accompanied by others symptoms of bacillary dysentery. Among major virulence genes, the PCR typing revealed ipaBCD was present in all isolates, followed by IpaH7.8, set-1A, set-1B, sen/ospD3, virF, and invE. The pathogenic potential of the ShET-1B subunit was observed in relation to dehydration (P<0.001 and ShET-2 related to the intestinal injury (P=0.033 evidenced by the presence of bloody diarrhea. Our results show associations among symptoms of shigellosis and virulence genes of clinical isolates of Shigella spp.

Variants of Moreau's sweeping process

International Nuclear Information System (INIS)

Siddiqi, A.H.; Manchanda, P.

2001-07-01

In this paper we prove the existence and uniqueness of two variants of Moreau's sweeping process -u'(t) is an element of Nc (t) (u(t)), where in one variant we replace u(t) by u'(t) in the right-hand side of the inclusion and in the second variant u'(t) and u(t) are respectively replaced by u''(t) and u'(t). (author)

Characterization of form variants of Xenorhabdus luminescens.

Science.gov (United States)

Gerritsen, L J; de Raay, G; Smits, P H

1992-01-01

From Xenorhabdus luminescens XE-87.3 four variants were isolated. One, which produced a red pigment and antibiotics, was luminescent, and could take up dye from culture media, was considered the primary form (XE-red). A pink-pigmented variant (XE-pink) differed from the primary form only in pigmentation and uptake of dye. Of the two other variants, one produced a yellow pigment and fewer antibiotics (XE-yellow), while the other did not produce a pigment or antibiotics (XE-white). Both were less luminescent, did not take up dye, and had small cell and colony sizes. These two variants were very unstable and shifted to the primary form after 3 to 5 days. It was not possible to separate the primary form and the white variant completely; subcultures of one colony always contained a few colonies of the other variant. The white variant was also found in several other X. luminescens strains. DNA fingerprints showed that all four variants are genetically identical and are therefore derivatives of the same parent. Protein patterns revealed a few differences among the four variants. None of the variants could be considered the secondary form. The pathogenicity of the variants decreased in the following order: XE-red, XE-pink, XE-yellow, and XE-white. The mechanism and function of this variability are discussed. Images PMID:1622273

Functional genomic characterization of virulence factors from necrotizing fasciitis-causing strains of Aeromonas hydrophila.

Science.gov (United States)

Grim, Christopher J; Kozlova, Elena V; Ponnusamy, Duraisamy; Fitts, Eric C; Sha, Jian; Kirtley, Michelle L; van Lier, Christina J; Tiner, Bethany L; Erova, Tatiana E; Joseph, Sandeep J; Read, Timothy D; Shak, Joshua R; Joseph, Sam W; Singletary, Ed; Felland, Tracy; Baze, Wallace B; Horneman, Amy J; Chopra, Ashok K

2014-07-01

The genomes of 10 Aeromonas isolates identified and designated Aeromonas hydrophila WI, Riv3, and NF1 to NF4; A. dhakensis SSU; A. jandaei Riv2; and A. caviae NM22 and NM33 were sequenced and annotated. Isolates NF1 to NF4 were from a patient with necrotizing fasciitis (NF). Two environmental isolates (Riv2 and -3) were from the river water from which the NF patient acquired the infection. While isolates NF2 to NF4 were clonal, NF1 was genetically distinct. Outside the conserved core genomes of these 10 isolates, several unique genomic features were identified. The most virulent strains possessed one of the following four virulence factors or a combination of them: cytotoxic enterotoxin, exotoxin A, and type 3 and 6 secretion system effectors AexU and Hcp. In a septicemic-mouse model, SSU, NF1, and Riv2 were the most virulent, while NF2 was moderately virulent. These data correlated with high motility and biofilm formation by the former three isolates. Conversely, in a mouse model of intramuscular infection, NF2 was much more virulent than NF1. Isolates NF2, SSU, and Riv2 disseminated in high numbers from the muscular tissue to the visceral organs of mice, while NF1 reached the liver and spleen in relatively lower numbers on the basis of colony counting and tracking of bioluminescent strains in real time by in vivo imaging. Histopathologically, degeneration of myofibers with significant infiltration of polymorphonuclear cells due to the highly virulent strains was noted. Functional genomic analysis provided data that allowed us to correlate the highly infectious nature of Aeromonas pathotypes belonging to several different species with virulence signatures and their potential ability to cause NF. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Bmh1p (14-3-3) mediates pathways associated with virulence in Candida albicans.

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Kelly, Michelle N; Johnston, Douglas A; Peel, Bethany A; Morgan, Timothy W; Palmer, Glen E; Sturtevant, Joy E

2009-05-01

The ability of the pathogenic fungus Candida albicans to cause disease requires rapid adaptation to changes in the host environment and to an evolving host immune response. The identification of 'virulence factors' using in vitro characterization of mutant strains has traditionally relied on a common set of phenotypic and biochemical assays (most often performed at 30 degrees C) and the subsequent correlation with their corresponding virulence in mouse models of disease. Utilizing a panel of isogenic mutants for the multifunctional signal-modulating 14-3-3 protein (Bmh1p), we have found that specific mutations affect a variety of different pathways currently associated with virulence, including those involved with the formation of filaments, as well as interaction with host immune cells. Surprisingly, our studies revealed that deficiencies in many of these pathways do not always correlate with virulence in a mouse model of disseminated infection. Mutations within the binding pocket of Bmh1p that affect the ability of the protein to efficiently bind ligand had varying effects on the results of a number of in vitro and in vivo assays. The capability, in vitro, to filament in embedment conditions, and to filament and form chlamydospores under microaerophilic conditions on cornmeal agar, does not correlate with virulence. It is likely that only a subset of hyphal signalling pathways is actually required for the establishment of infection in the disseminated mouse model. Most importantly, our results suggest that the delayed onset of log-phase [corrected] growth in vitro at 37 degrees C, and not at 30 degrees C, results in an inability of these mutants to rapidly adjust to environmental changes in vivo and may be responsible for their increased clearance and reduced virulence. It is critical, therefore, that future in vitro studies of putative virulence factors in C. albicans include careful characterization at physiological temperatures.

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....

BigQ: a NoSQL based framework to handle genomic variants in i2b2.

Science.gov (United States)

Gabetta, Matteo; Limongelli, Ivan; Rizzo, Ettore; Riva, Alberto; Segagni, Daniele; Bellazzi, Riccardo

2015-12-29

Precision medicine requires the tight integration of clinical and molecular data. To this end, it is mandatory to define proper technological solutions able to manage the overwhelming amount of high throughput genomic data needed to test associations between genomic signatures and human phenotypes. The i2b2 Center (Informatics for Integrating Biology and the Bedside) has developed a widely internationally adopted framework to use existing clinical data for discovery research that can help the definition of precision medicine interventions when coupled with genetic data. i2b2 can be significantly advanced by designing efficient management solutions of Next Generation Sequencing data. We developed BigQ, an extension of the i2b2 framework, which integrates patient clinical phenotypes with genomic variant profiles generated by Next Generation Sequencing. A visual programming i2b2 plugin allows retrieving variants belonging to the patients in a cohort by applying filters on genomic variant annotations. We report an evaluation of the query performance of our system on more than 11 million variants, showing that the implemented solution scales linearly in terms of query time and disk space with the number of variants. In this paper we describe a new i2b2 web service composed of an efficient and scalable document-based database that manages annotations of genomic variants and of a visual programming plug-in designed to dynamically perform queries on clinical and genetic data. The system therefore allows managing the fast growing volume of genomic variants and can be used to integrate heterogeneous genomic annotations.

The effects of multiple infections on the expression and evolution of virulence in a Daphnia-endoparasite system.

Science.gov (United States)

Ben-Ami, Frida; Mouton, Laurence; Ebert, Dieter

2008-07-01

Multiple infections of a host by different strains of the same microparasite are common in nature. Although numerous models have been developed in an attempt to predict the evolutionary effects of intrahost competition, tests of the assumptions of these models are rare and the outcome is diverse. In the present study we examined the outcome of mixed-isolate infections in individual hosts, using a single clone of the waterflea Daphnia magna and three isolates of its semelparous endoparasite Pasteuria ramosa. We exposed individual Daphnia to single- and mixed-isolate infection treatments, both simultaneously and sequentially. Virulence was assessed by monitoring host mortality and fecundity, and parasite spore production was used as a measure of parasite fitness. Consistent with most assumptions, in multiply infected hosts we found that the virulence of mixed infections resembled that of the more virulent competitor, both in simultaneous multiple infections and in sequential multiple infections in which the virulent isolate was first to infect. The more virulent competitor also produced the vast majority of transmission stages. Only when the less virulent isolate was first to infect, the intrahost contest resembled scramble competition, whereby both isolates suffered by producing fewer transmission stages. Surprisingly, mixed-isolate infections resulted in lower fecundity-costs for the hosts, suggesting that parasite competition comes with an advantage for the host relative to single infections. Finally, spore production correlated positively with time-to-host-death. Thus, early-killing of more competitive isolates produces less transmission stages than less virulent, inferior isolates. Our results are consistent with the idea that less virulent parasite lines may be replaced by more virulent strains under conditions with high rates of multiple infections.

Genome-wide association scan for variants associated with early-onset prostate cancer.

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Ethan M Lange

Full Text Available Prostate cancer is the most common non-skin cancer and the second leading cause of cancer related mortality for men in the United States. There is strong empirical and epidemiological evidence supporting a stronger role of genetics in early-onset prostate cancer. We performed a genome-wide association scan for early-onset prostate cancer. Novel aspects of this study include the focus on early-onset disease (defined as men with prostate cancer diagnosed before age 56 years and use of publically available control genotype data from previous genome-wide association studies. We found genome-wide significant (p<5×10(-8 evidence for variants at 8q24 and 11p15 and strong supportive evidence for a number of previously reported loci. We found little evidence for individual or systematic inflated association findings resulting from using public controls, demonstrating the utility of using public control data in large-scale genetic association studies of common variants. Taken together, these results demonstrate the importance of established common genetic variants for early-onset prostate cancer and the power of including early-onset prostate cancer cases in genetic association studies.

Random Plant Viral Variants Attain Temporal Advantages During Systemic Infections and in Turn Resist other Variants of the Same Virus.

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Zhang, Xiao-Feng; Guo, Jiangbo; Zhang, Xiuchun; Meulia, Tea; Paul, Pierce; Madden, Laurence V; Li, Dawei; Qu, Feng

2015-10-20

Infection of plants with viruses containing multiple variants frequently leads to dominance by a few random variants in the systemically infected leaves (SLs), for which a plausible explanation is lacking. We show here that SL dominance by a given viral variant is adequately explained by its fortuitous lead in systemic spread, coupled with its resistance to superinfection by other variants. We analyzed the fate of a multi-variant turnip crinkle virus (TCV) population in Arabidopsis and N. benthamiana plants. Both wild-type and RNA silencing-defective plants displayed a similar pattern of random dominance by a few variant genotypes, thus discounting a prominent role for RNA silencing. When introduced to plants sequentially as two subpopulations, a twelve-hour head-start was sufficient for the first set to dominate. Finally, SLs of TCV-infected plants became highly resistant to secondary invasions of another TCV variant. We propose that random distribution of variant foci on inoculated leaves allows different variants to lead systemic movement in different plants. The leading variants then colonize large areas of SLs, and resist the superinfection of lagging variants in the same areas. In conclusion, superinfection resistance is the primary driver of random enrichment of viral variants in systemically infected plants.

The effect of immunodeficiency on the evolution of virulence: an experimental test with the rodent malaria Plasmodium chabaudi.

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Barclay, Victoria C; Kennedy, David A; Weaver, Veronika C; Sim, Derek; Lloyd-Smith, James O; Read, Andrew F

2014-08-01

Host immunity plays an important role in the evolution of pathogen virulence and disease emergence. There is increasing theoretical and empirical evidence that enhanced immunity through vaccination may have the unfortunate side effect of selecting for more virulent parasites, but the effect of host immune suppression on pathogen evolution is less clear. Here, we use serial passage experiments in mice to test how immune-suppressed hosts may alter pathogen virulence evolution. We passaged Plasmodium chabaudi through CD4(+) T cell-depleted or control mice every 7 days for 20 weeks and then measured virulence differences during infection of immunologically normal mice. We found that those parasites that had been selected through CD4(+) T cell-depleted mice were more virulent than parasites selected through control mice. Virulence increases during serial passage are believed to be caused by pathogen adaptation to the passage host. These data suggest that immune-suppressed hosts could provide a within-host environment that lowers the barrier to parasite adaptation and promotes the evolution of virulence.

Cyt toxin expression reveals an inverse regulation of insect and plant virulence factors of Dickeya dadantii.

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Costechareyre, Denis; Dridi, Bedis; Rahbé, Yvan; Condemine, Guy

2010-12-01

The plant pathogenic bacteria Dickeya dadantii is also a pathogen of the pea aphid Acyrthosiphon pisum. The genome of the bacteria contains four cyt genes, encoding homologues of Bacillus thuringiensis Cyt toxins, which are involved in its pathogenicity to insects. We show here that these genes are transcribed as an operon, and we determined the conditions necessary for their expression. Their expression is induced at high temperature and at an osmolarity equivalent to that found in the plant phloem sap. The regulators of cyt genes have also been identified: their expression is repressed by H-NS and VfmE and activated by PecS. These genes are already known to regulate plant virulence factors, but in an opposite way. When tested in a virulence assay by ingestion, the pecS mutant was almost non-pathogenic while hns and vfmE mutants behaved in the same way as the wild-type strain. Mutants of other regulators of plant virulence, GacA, OmpR and PhoP, that do not control Cyt toxin production, also showed reduced pathogenicity. In an assay by injection of bacteria, the gacA strain was less pathogenic but, surprisingly, the pecS mutant was slightly more virulent. These results show that Cyt toxins are not the only virulence factors required to kill aphids, and that these factors act at different stages of the infection. Moreover, their production is controlled by general virulence regulators known for their role in plant virulence. This integration could indicate that virulence towards insects is a normal mode of life for D. dadantii. © 2010 Society for Applied Microbiology and Blackwell Publishing Ltd.

Comparison of virulence factors and capsular types of Streptococcus agalactiae isolated from human and bovine infections.

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Emaneini, Mohammad; Khoramian, Babak; Jabalameli, Fereshteh; Abani, Samira; Dabiri, Hossein; Beigverdi, Reza

2016-02-01

Streptococcus agalactiae is a leading cause of human and bovine infections. A total of 194 S. agalactiae isolates, 55 isolates from bovines and 139 from humans, were analyzed for capsular types, virulence genes (scpB, hly, rib, bca and bac) and mobile genetic elements (IS1548 and GBSi1) using polymerase chain reaction (PCR) and multiplex PCR. Capsular type III was predominant (61%), followed by types V, II, Ib, and IV. The scpB, hly, bca and bac virulence genes were only found among human isolates. Twelve and 2 distinct virulence gene profiles were identified among human and bovine isolates respectively. The virulence gene profiles scpB- hly- IS1548- rib-bca (51%) and scpB- hly- IS1548- bca (19%) were only predominant among human isolates. The rib gene was the most common virulence gene in both human and bovine isolates. The study showed a high prevalence of virulence genes in S. agalactiae strains isolated from human infections, these result can support the idea that S. agalactiae isolated from humans and bovines are generally unrelated and probably belonged to separate populations. Copyright © 2015 Elsevier Ltd. All rights reserved.

A polymerase chain reaction assay for detection of virulent and attenuated strains of duck plague virus.

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Xie, Liji; Xie, Zhixun; Huang, Li; Wang, Sheng; Huang, Jiaoling; Zhang, Yanfang; Zeng, Tingting; Luo, Sisi

2017-11-01

Sequence analysis of duck plague virus (DPV) revealed that there was a 528bp (B fragment) deletion within the UL2 gene of DPV attenuated vaccine strain in comparison with field virulent strains. The finding of gene deletion provides a potential differentiation test between DPV virulent strain and attenuated strain based on their UL2 gene sizes. Thus we developed a polymerase chain reaction (PCR) assay targeting to the DPV UL2 gene for simultaneous detection of DPV virulent strain and attenuated strain, 827bp for virulent strain and 299bp for attenuated strain. This newly developed PCR for DPV was highly sensitive and specific. It detected as low as 100fg of DNA on both DPV virulent and attenuated strains, no same size bands were amplified from other duck viruses including duck paramyxovirus, duck tembusu virus, duck circovirus, Muscovy duck parvovirus, duck hepatitis virus type I, avian influenza virus and gosling plague virus. Therefore, this PCR assay can be used for the rapid, sensitive and specific detection of DPV virulent and attenuated strains affecting ducks. Copyright © 2017. Published by Elsevier B.V.

Semantic prioritization of novel causative genomic variants

KAUST Repository

Boudellioua, Imene

2017-04-17

Discriminating the causative disease variant(s) for individuals with inherited or de novo mutations presents one of the main challenges faced by the clinical genetics community today. Computational approaches for variant prioritization include machine learning methods utilizing a large number of features, including molecular information, interaction networks, or phenotypes. Here, we demonstrate the PhenomeNET Variant Predictor (PVP) system that exploits semantic technologies and automated reasoning over genotype-phenotype relations to filter and prioritize variants in whole exome and whole genome sequencing datasets. We demonstrate the performance of PVP in identifying causative variants on a large number of synthetic whole exome and whole genome sequences, covering a wide range of diseases and syndromes. In a retrospective study, we further illustrate the application of PVP for the interpretation of whole exome sequencing data in patients suffering from congenital hypothyroidism. We find that PVP accurately identifies causative variants in whole exome and whole genome sequencing datasets and provides a powerful resource for the discovery of causal variants.

Semantic prioritization of novel causative genomic variants

KAUST Repository

Boudellioua, Imene; Mohamad Razali, Rozaimi; Kulmanov, Maxat; Hashish, Yasmeen; Bajic, Vladimir B.; Goncalves-Serra, Eva; Schoenmakers, Nadia; Gkoutos, Georgios V.; Schofield, Paul N.; Hoehndorf, Robert

2017-01-01

Discriminating the causative disease variant(s) for individuals with inherited or de novo mutations presents one of the main challenges faced by the clinical genetics community today. Computational approaches for variant prioritization include machine learning methods utilizing a large number of features, including molecular information, interaction networks, or phenotypes. Here, we demonstrate the PhenomeNET Variant Predictor (PVP) system that exploits semantic technologies and automated reasoning over genotype-phenotype relations to filter and prioritize variants in whole exome and whole genome sequencing datasets. We demonstrate the performance of PVP in identifying causative variants on a large number of synthetic whole exome and whole genome sequences, covering a wide range of diseases and syndromes. In a retrospective study, we further illustrate the application of PVP for the interpretation of whole exome sequencing data in patients suffering from congenital hypothyroidism. We find that PVP accurately identifies causative variants in whole exome and whole genome sequencing datasets and provides a powerful resource for the discovery of causal variants.

Pathogenic Leptospira: Advances in understanding the molecular pathogenesis and virulence

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Ghazaei, Ciamak

2018-01-01

Leptospirosis is a common zoonotic disease has emerged as a major public health problem, with developing countries bearing disproportionate burdens. Although the diverse range of clinical manifestations of the leptospirosis in humans is widely documented, the mechanisms through which the pathogen causes disease remain undetermined. In addition, leptospirosis is a much-neglected life-threatening disease although it is one of the most important zoonoses occurring in a diverse range of epidemiological distribution. Recent advances in molecular profiling of pathogenic species of the genus Leptospira have improved our understanding of the evolutionary factors that determine virulence and mechanisms that the bacteria employ to survive. However, a major impediment to the formulation of intervention strategies has been the limited understanding of the disease determinants. Consequently, the association of the biological mechanisms to the pathogenesis of Leptospira, as well as the functions of numerous essential virulence factors still remain implicit. This review examines recent advances in genetic screening technologies, the underlying microbiological processes, the virulence factors and associated molecular mechanisms driving pathogenesis of Leptospira species. PMID:29445617

Evolution of Regions Containing Antibiotic Resistance Genes in FII-2-FIB-1 ColV-Colla Virulence Plasmids.

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Moran, Robert A; Hall, Ruth M

2018-05-01

Three ColV virulence plasmids carrying antibiotic resistance genes were assembled from draft genome sequences of commensal ST95, ST131, and ST2705 Escherichia coli isolates from healthy Australians. Plasmids pCERC4, pCERC5, and pCERC9 include almost identical backbones containing FII-2 and FIB-1 replicons and the conserved ColV virulence region with an additional ColIa determinant. Only pCERC5 includes a complete, uninterrupted F-like transfer region and was able to conjugate. pCERC5 and pCERC9 contain Tn1721, carrying the tet(A) tetracycline resistance determinant in the same location, with Tn2 (bla TEM ; ampicillin resistance) interrupting the Tn1721 in pCERC5. pCERC4 has a Tn1721/Tn21 hybrid transposon carrying dfrA5 (trimethoprim resistance) and sul1 (sulfamethoxazole resistance) in a class 1 integron. Four FII-2:FIB-1 ColV-ColIa plasmids in the GenBank nucleotide database have a related transposon in the same position, but an IS26 has reshaped the resistance gene region, deleting 2,069 bp of the integron 3'-CS, including sul1, and serving as a target for IS26 translocatable units containing bla TEM , sul2 and strAB (streptomycin resistance), or aphA1 (kanamycin/neomycin resistance). Another ColV-ColIa plasmid containing a related resistance gene region has lost the FII replicon and acquired a unique transfer region via recombination within the resistance region and at oriT. Eighteen further complete ColV plasmid sequences in GenBank contained FIB-1, but the FII replicons were of three types, FII-24, FII-18, and a variant of FII-36.

Generation of a convalescent model of virulent Francisella tularensis infection for assessment of host requirements for survival of tularemia.

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Deborah D Crane

Full Text Available Francisella tularensis is a facultative intracellular bacterium and the causative agent of tularemia. Development of novel vaccines and therapeutics for tularemia has been hampered by the lack of understanding of which immune components are required to survive infection. Defining these requirements for protection against virulent F. tularensis, such as strain SchuS4, has been difficult since experimentally infected animals typically die within 5 days after exposure to as few as 10 bacteria. Such a short mean time to death typically precludes development, and therefore assessment, of immune responses directed against virulent F. tularensis. To enable identification of the components of the immune system that are required for survival of virulent F. tularensis, we developed a convalescent model of tularemia in C57Bl/6 mice using low dose antibiotic therapy in which the host immune response is ultimately responsible for clearance of the bacterium. Using this model we demonstrate αβTCR(+ cells, γδTCR(+ cells, and B cells are necessary to survive primary SchuS4 infection. Analysis of mice deficient in specific soluble mediators shows that IL-12p40 and IL-12p35 are essential for survival of SchuS4 infection. We also show that IFN-γ is required for survival of SchuS4 infection since mice lacking IFN-γR succumb to disease during the course of antibiotic therapy. Finally, we found that both CD4(+ and CD8(+ cells are the primary producers of IFN-γand that γδTCR(+ cells and NK cells make a minimal contribution toward production of this cytokine throughout infection. Together these data provide a novel model that identifies key cells and cytokines required for survival or exacerbation of infection with virulent F. tularensis and provides evidence that this model will be a useful tool for better understanding the dynamics of tularemia infection.

Identification of virulence genes carried by bacteriophages obtained from clinically isolated methicillin-resistant Staphylococcus aureus.

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Karasartova, Djursun; Cavusoglu, Zeynep Burcin; Turegun, Buse; Ozsan, Murat T; Şahin, Fikret

2016-12-01

Bacteriophages play an important role in the pathogenicity of Staphylococcus aureus (S. aureus) either by carrying accessory virulence factors or several superantigens. Despite their importance, there are not many studies showing the actual distribution of the virulence genes carried by the prophages obtained from the clinically isolated Staphylococcus. In this study, we investigated prophages obtained from methicillin-resistant S. aureus (MRSA) strains isolated from hospital- and community-associated (HA-CA) infections for the virulence factors. In the study, 43 phages isolated from 48 MRSA were investigated for carrying toxin genes including the sak, eta, lukF-PV, sea, selp, sek, seg, seq chp, and scn virulence genes using polymerase chain reaction (PCR) and Southern blot. Restriction fragment length polymorphism was used to analyze phage genomes to investigate the relationship between the phage profiles and the toxin genes' presence. MRSA strains isolated from HA infections tended to have higher prophage presence than the MRSA strains obtained from the CA infections (97% and 67%, respectively). The study showed that all the phages with the exception of one phage contained one or more virulence genes in their genomes with different combinations. The most common toxin genes found were sea (83%) followed by sek (77%) and seq (64%). The study indicates that prophages encode a significant proportion of MRSA virulence factors.

Carbapenem-resistant Pseudomonas aeruginosa: association with virulence genes and biofilm formation

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Iara Rossi Gonçalves

Full Text Available Abstract Pseudomonas aeruginosa is an opportunistic pathogen that causes frequently nosocomial infections, currently becoming more difficult to treat due to the various resistance mechanisms and different virulence factors. The purpose of this study was to determine the risk factors independently associated with the development of bacteremia by carbapenem-resistant P. aeruginosa, the frequency of virulence genes in metallo-β-lactamases producers and to evaluate their ability to produce biofilm. We conducted a case–control study in the Uberlândia Federal University – Hospital Clinic, Brazil. Polymerase Chain Reaction was performed for metallo-β-lactamases and virulence genes. Adhesion and biofilm assays were done by quantitative tests. Among the 157 strains analyzed, 73.9% were multidrug-resistant, 43.9% were resistant to carbapenems, 16.1% were phenotypically positive for metallo-β-lactamases, and of these, 10.7% were positive for blaSPM gene and 5.3% positive for blaVIM. The multivariable analysis showed that mechanical ventilation, enteral/nasogastric tubes, primary bacteremia with unknown focus, and inappropriate therapy were independent risk factors associated with bacteremia. All tested strains were characterized as strongly biofilm producers. A higher mortality was found among patients with bacteremia by carbapenem-resistant P. aeruginosa strains, associated independently with extrinsic risk factors, however it was not evident the association with the presence of virulence and metallo-β-lactamases genes.

[Virulence of Sporothrix globosa in murine models].

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Cruz Choappa, Rodrigo; Pérez Gaete, Salomón; Rodríguez Badilla, Valentina; Vieille Oyarzo, Peggy; Opazo Sanchez, Héctor

The sporothricosis disease is an infection caused by species included in Sporothrix schenkii complex. Verify the virulence of a strain of S. globosa using two different concentrations of inoculum by intraperitoneally and subcutaneously, into a mouse model. Nonrandomized pilot study, in murine inoculated with a strain of S. globosa (CBS 14.076M) by intraperitoneally and subcutaneously with inoculum concentrations of 0.5 and 4 McFarland. For this purpose 18 rodents CF-1 (ISP, Santiago, Chile) were used. The studied strain did not induce illness or injury on animals, they all survived and neither the tissue culture nor the histopathological analysis showed fungal growth or suggestive infection by organ abnormalities. The S. globosa strain did not present any virulence enough to cause disease at 0.5 and 4.0 McFarland concentration inoculum when inoculated in both intraperitoneally and subcutaneously, in murine models. Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

A single polymerase (L) mutation in avian metapneumovirus increased virulence and partially maintained virus viability at an elevated temperature.

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Brown, Paul A; Lupini, Caterina; Catelli, Elena; Clubbe, Jayne; Ricchizzi, Enrico; Naylor, Clive J

2011-02-01

Previously, a virulent avian metapneumovirus, farm isolate Italy 309/04, was shown to have been derived from a live vaccine. Virulence due to the five nucleotide mutations associated with the reversion to virulence was investigated by their addition to the genome of the vaccine strain using reverse genetics. Virulence of these recombinant viruses was determined by infection of 1-day-old turkeys. Disease levels resulting from the combined two matrix mutations was indistinguishable from that produced by the recombinant vaccine, whereas the combined three L gene mutations increased disease to a level (P<0.0001) that was indistinguishable from that caused by the revertant Italy 309/04 virus. Testing of the L mutations individually showed that two mutations did not increase virulence, while the third mutation, corresponding to an asparagine to aspartic acid substitution, produced virulence indistinguishable from that caused by Italy 309/04. In contrast to the vaccine, the virulent mutant also showed increased viability at temperatures typical of turkey core tissues. The notion that increased viral virulence resulted from enhanced ability to replicate in tissues away from the cool respiratory tract, cannot be discounted.

Catheter-related infections caused by Pseudomonas aeruginosa: virulence factors involved and their relationships.

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Olejnickova, Katerina; Hola, Veronika; Ruzicka, Filip

2014-11-01

The nosocomial pathogen Pseudomonas aeruginosa is equipped with a large arsenal of cell-associated and secreted virulence factors which enhance its invasive potential. The complex relationships among virulence determinants have hitherto not been fully elucidated. In the present study, 175 catheter-related isolates were observed for the presence of selected virulence factors, namely extracellular enzymes and siderophore production, biofilm formation, resistance to antibiotics, and motility. A high percentage of the strains produced most of the tested virulence factors. A positive correlation was identified between the production of several exoproducts, and also between the formation of both types of biofilm. An opposite trend was observed between the two types of biofilm and the production of siderophores. Whereas the relationship between the submerged biofilm production (i.e. the biofilm formed on the solid surface below the water level) and the siderophore secretion was negative, the production of air-liquid interface (A-L) biofilm (i.e. the biofilm floating on the surface of the cultivation medium) and the siderophore secretion were positively correlated. All correlations were statistically significant at the level P = 0.05 with the correlation coefficient γ ≥ 0.50. Our results suggest that: (1) the co-production of the lytic enzymes and siderophores can play an important role in the pathogenesis of the catheter-related infections and should be taken into account when the virulence potential is assessed; (2) biofilm-positive strains are capable of forming both submerged and non-attached A-L biofilms; and (3) the different micro-environment in the submerged biofilm and A-L biofilm layers have opposite consequences for the production of other virulence factors. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Temperate and virulent Lactobacillus delbrueckii bacteriophages: comparison of their thermal and chemical resistance.

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Ebrecht, Ana C; Guglielmotti, Daniela M; Tremmel, Gustavo; Reinheimer, Jorge A; Suárez, Viviana B

2010-06-01

The aim of this work was to study the efficiency of diverse chemical and thermal treatments usually used in dairy industries to control the number of virulent and temperate Lactobacillus delbrueckii bacteriophages. Two temperate (Cb1/204 and Cb1/342) and three virulent (BYM, YAB and Ib3) phages were studied. The thermal treatments applied were: 63 degrees C for 30 min (low temperature--long time, LTLT), 72 degrees C for 15 s (high temperature--short time, HTST), 82 degrees C for 5 min (milk destined to yogurt elaboration) and 90 degrees C for 15 min (FIL-IDF). The chemical agents studied were: sodium hypochlorite, ethanol, isopropanol, peracetic acid, biocides A (quaternary ammonium chloride), B (hydrogen peroxide, peracetic acid and peroctanoic acid), C (alkaline chloride foam), D (p-toluensulfonchloroamide, sodium salt) and E (ethoxylated nonylphenol and phosphoric acid). The kinetics of inactivation were drew and T(99) (time necessary to eliminate the 99% of phage particles) calculated. Results obtained showed that temperate phages revealed lower resistance than the virulent ones to the treatment temperatures. Biocides A, C, E and peracetic acid showed a notable efficiency to inactivate high concentrations of temperate and virulent L. delbrueckii phages. Biocide B evidenced, in general, a good capacity to eliminate the phage particles. Particularly for this biocide virulent phage Ib3 showed the highest resistance in comparison to the rest of temperate and virulent ones. On the contrary, biocide D and isopropanol presented a very low capacity to inactivate all phages studied. The efficiency of ethanol and hypochlorite was variable depending to the phages considered. These results allow a better knowledge and give useful information to outline more effective treatments to reduce the phage infections in dairy plants. 2009 Elsevier Ltd. All rights reserved.

Macrophage replication screen identifies a novel Francisella hydroperoxide resistance protein involved in virulence.

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Anna C Llewellyn

Full Text Available Francisella tularensis is a gram-negative facultative intracellular pathogen and the causative agent of tularemia. Recently, genome-wide screens have identified Francisella genes required for virulence in mice. However, the mechanisms by which most of the corresponding proteins contribute to pathogenesis are still largely unknown. To further elucidate the roles of these virulence determinants in Francisella pathogenesis, we tested whether each gene was required for replication of the model pathogen F. novicida within macrophages, an important virulence trait. Fifty-three of the 224 genes tested were involved in intracellular replication, including many of those within the Francisella pathogenicity island (FPI, validating our results. Interestingly, over one third of the genes identified are annotated as hypothetical, indicating that F. novicida likely utilizes novel virulence factors for intracellular replication. To further characterize these virulence determinants, we selected two hypothetical genes to study in more detail. As predicted by our screen, deletion mutants of FTN_0096 and FTN_1133 were attenuated for replication in macrophages. The mutants displayed differing levels of attenuation in vivo, with the FTN_1133 mutant being the most attenuated. FTN_1133 has sequence similarity to the organic hydroperoxide resistance protein Ohr, an enzyme involved in the bacterial response to oxidative stress. We show that FTN_1133 is required for F. novicida resistance to, and degradation of, organic hydroperoxides as well as resistance to the action of the NADPH oxidase both in macrophages and mice. Furthermore, we demonstrate that F. holarctica LVS, a strain derived from a highly virulent human pathogenic species of Francisella, also requires this protein for organic hydroperoxide resistance as well as replication in macrophages and mice. This study expands our knowledge of Francisella's largely uncharacterized intracellular lifecycle and

Phenotypic and Genotypic Characterization of Virulent Yersinia enterocolitica Strains Unable To Ferment Sucrose

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Guiyoule, Annie; Guinet, Françoise; Martin, Liliane; Benoit, Catherine; Desplaces, Nicole; Carniel, Elisabeth

1998-01-01

Several atypical sucrose-negative Yersinia strains, isolated from clinical samples and sometimes associated with symptoms, proved to have full virulence potential in in vitro and in vivo testings. DNA-relatedness studies revealed that they were authentic Yersinia enterocolitica strains. Therefore, atypical sucrose-negative Yersinia isolates should be analyzed for their virulence potential. PMID:9705424

Metabolism of the vacuolar pathogen Legionella and implications for virulence.

Science.gov (United States)

Manske, Christian; Hilbi, Hubert

2014-01-01

Legionella pneumophila is a ubiquitous environmental bacterium that thrives in fresh water habitats, either as planktonic form or as part of biofilms. The bacteria also grow intracellularly in free-living protozoa as well as in mammalian alveolar macrophages, thus triggering a potentially fatal pneumonia called "Legionnaires' disease." To establish its intracellular niche termed the "Legionella-containing vacuole" (LCV), L. pneumophila employs a type IV secretion system and translocates ~300 different "effector" proteins into host cells. The pathogen switches between two distinct forms to grow in its extra- or intracellular niches: transmissive bacteria are virulent for phagocytes, and replicative bacteria multiply within their hosts. The switch between these forms is regulated by different metabolic cues that signal conditions favorable for replication or transmission, respectively, causing a tight link between metabolism and virulence of the bacteria. Amino acids represent the prime carbon and energy source of extra- or intracellularly growing L. pneumophila. Yet, the genome sequences of several Legionella spp. as well as transcriptome and proteome data and metabolism studies indicate that the bacteria possess broad catabolic capacities and also utilize carbohydrates such as glucose. Accordingly, L. pneumophila mutant strains lacking catabolic genes show intracellular growth defects, and thus, intracellular metabolism and virulence of the pathogen are intimately connected. In this review we will summarize recent findings on the extra- and intracellular metabolism of L. pneumophila using genetic, biochemical and cellular microbial approaches. Recent progress in this field sheds light on the complex interplay between metabolism, differentiation and virulence of the pathogen.

Comparison of gene-based rare variant association mapping methods for quantitative traits in a bovine population with complex familial relationships.

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Zhang, Qianqian; Guldbrandtsen, Bernt; Calus, Mario P L; Lund, Mogens Sandø; Sahana, Goutam

2016-08-17

There is growing interest in the role of rare variants in the variation of complex traits due to increasing evidence that rare variants are associated with quantitative traits. However, association methods that are commonly used for mapping common variants are not effective to map rare variants. Besides, livestock populations have large half-sib families and the occurrence of rare variants may be confounded with family structure, which makes it difficult to disentangle their effects from family mean effects. We compared the power of methods that are commonly applied in human genetics to map rare variants in cattle using whole-genome sequence data and simulated phenotypes. We also studied the power of mapping rare variants using linear mixed models (LMM), which are the method of choice to account for both family relationships and population structure in cattle. We observed that the power of the LMM approach was low for mapping a rare variant (defined as those that have frequencies lower than 0.01) with a moderate effect (5 to 8 % of phenotypic variance explained by multiple rare variants that vary from 5 to 21 in number) contributing to a QTL with a sample size of 1000. In contrast, across the scenarios studied, statistical methods that are specialized for mapping rare variants increased power regardless of whether multiple rare variants or a single rare variant underlie a QTL. Different methods for combining rare variants in the test single nucleotide polymorphism set resulted in similar power irrespective of the proportion of total genetic variance explained by the QTL. However, when the QTL variance is very small (only 0.1 % of the total genetic variance), these specialized methods for mapping rare variants and LMM generally had no power to map the variants within a gene with sample sizes of 1000 or 5000. We observed that the methods that combine multiple rare variants within a gene into a meta-variant generally had greater power to map rare variants compared

Molecular Detection of Virulence Genes and Antibiotic Resistance ...

African Journals Online (AJOL)

Pathogen, E. coli O157:H7, virulence genes, antibiotic-resistance, beef meat. Correspondence: ... box to the laboratory for further processing. Isolation and identification of ... Technologies (IDT) Inc, U.S.A. The sequences and annealing ...

A preliminary survey of M. hyopneumoniae virulence factors based on comparative genomic analysis

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Henrique Bunselmeyer Ferreira

2007-01-01

Full Text Available Mycoplasma hyopneumoniae is the etiological agent of porcine enzootic pneumonia (PEP, a major problem for the pig industry. The mechanisms of M. hyopneumoniae pathogenicity allow to predict the existence of several classes of virulence factors, whose study has been essentially restricted to the characterization of adhesion-related and major antigenic proteins. The now available complete sequences of the genomes of two pathogenic and one non-pathogenic strain of M. hyopneumoniae allowed to use a comparative genomics approach to putatively identify virulence genes. In this preliminary survey, we were able to identify 118 CDSs encoding putative virulence factors, based on specific criteria ranging from predicted cell surface location or variation between strains to previous functional studies showing antigenicity or involvement in host-pathogen interaction. This survey is expected to serve as a first step towards the functional characterization of new virulence genes/proteins that will be important not only for a better comprehension of M. hyopneumoniae biology, but also for the development of new and improved protocols for PEP vaccination, diagnosis and treatment.

Swine Influenza/Variant Influenza Viruses

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Beta-glucosidase variants and polynucleotides encoding same

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Wogulis, Mark; Harris, Paul; Osborn, David

2017-06-27

The present invention relates to beta-glucosidase variants, e.g. beta-glucosidase variants of a parent Family GH3A beta-glucosidase from Aspergillus fumigatus. The present invention also relates to polynucleotides encoding the beta-glucosidase variants; nucleic acid constructs, vectors, and host cells comprising the polynucleotides; and methods of using the beta-glucosidase variants.

Co-evolution of genomes and plasmids within Chlamydia trachomatis and the emergence in Sweden of a new variant strain

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Skilton Rachel J

2009-05-01

Full Text Available Abstract Background Chlamydia trachomatis is the most common cause of sexually transmitted infections globally and the leading cause of preventable blindness in the developing world. There are two biovariants of C. trachomatis: 'trachoma', causing ocular and genital tract infections, and the invasive 'lymphogranuloma venereum' strains. Recently, a new variant of the genital tract C. trachomatis emerged in Sweden. This variant escaped routine diagnostic tests because it carries a plasmid with a deletion. Failure to detect this strain has meant it has spread rapidly across the country provoking a worldwide alert. In addition to being a key diagnostic target, the plasmid has been linked to chlamydial virulence. Analysis of chlamydial plasmids and their cognate chromosomes was undertaken to provide insights into the evolutionary relationship between chromosome and plasmid. This is essential knowledge if the plasmid is to be continued to be relied on as a key diagnostic marker, and for an understanding of the evolution of Chlamydia trachomatis. Results The genomes of two new C. trachomatis strains were sequenced, together with plasmids from six C. trachomatis isolates, including the new variant strain from Sweden. The plasmid from the new Swedish variant has a 377 bp deletion in the first predicted coding sequence, abolishing the site used for PCR detection, resulting in negative diagnosis. In addition, the variant plasmid has a 44 bp duplication downstream of the deletion. The region containing the second predicted coding sequence is the most highly conserved region of the plasmids investigated. Phylogenetic analysis of the plasmids and chromosomes are fully congruent. Moreover this analysis also shows that ocular and genital strains diverged from a common C. trachomatis progenitor. Conclusion The evolutionary pathways of the chlamydial genome and plasmid imply that inheritance of the plasmid is tightly linked with its cognate chromosome. These data

A phylogenomic analysis of Marek's disease virus reveals independent paths to virulence in Eurasia and North America.

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Trimpert, Jakob; Groenke, Nicole; Jenckel, Maria; He, Shulin; Kunec, Dusan; Szpara, Moriah L; Spatz, Stephen J; Osterrieder, Nikolaus; McMahon, Dino P

2017-12-01

Virulence determines the impact a pathogen has on the fitness of its host, yet current understanding of the evolutionary origins and causes of virulence of many pathogens is surprisingly incomplete. Here, we explore the evolution of Marek's disease virus (MDV), a herpesvirus commonly afflicting chickens and rarely other avian species. The history of MDV in the 20th century represents an important case study in the evolution of virulence. The severity of MDV infection in chickens has been rising steadily since the adoption of intensive farming techniques and vaccination programs in the 1950s and 1970s, respectively. It has remained uncertain, however, which of these factors is causally more responsible for the observed increase in virulence of circulating viruses. We conducted a phylogenomic study to understand the evolution of MDV in the context of dramatic changes to poultry farming and disease control. Our analysis reveals evidence of geographical structuring of MDV strains, with reconstructions supporting the emergence of virulent viruses independently in North America and Eurasia. Of note, the emergence of virulent viruses appears to coincide approximately with the introduction of comprehensive vaccination on both continents. The time-dated phylogeny also indicated that MDV has a mean evolutionary rate of ~1.6 × 10 -5 substitutions per site per year. An examination of gene-linked mutations did not identify a strong association between mutational variation and virulence phenotypes, indicating that MDV may evolve readily and rapidly under strong selective pressures and that multiple genotypic pathways may underlie virulence adaptation in MDV.

Multilocus Sequence Typing and Virulence Profiles in Uropathogenic Escherichia coli Isolated from Cats in the United States.

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Xiaoqiang Liu

Full Text Available The population structure, virulence, and antimicrobial resistance of uropathogenic E. coli (UPEC from cats are rarely characterized. The aim of this study was to compare and characterize the UPEC isolated from cats in four geographic regions of USA in terms of their multilocus sequence typing (MLST, virulence profiles, clinical signs, antimicrobial resistance and phylogenetic grouping. The results showed that a total of 74 E. coli isolates were typed to 40 sequence types with 10 being novel. The most frequent phylogenetic group was B2 (n = 57. The most frequent sequence types were ST73 (n = 12 and ST83 (n = 6, ST73 was represented by four multidrug resistant (MDR and eight non-multidrug resistant (SDR isolates, and ST83 were significantly more likely to exhibit no drug resistant (NDR isolates carrying the highest number of virulence genes. Additionally, MDR isolates were more diverse, and followed by SDR and NDR isolates in regards to the distribution of the STs. afa/draBC was the most prevalent among the 29 virulence-associated genes. Linking virulence profile and antimicrobial resistance, the majority of virulence-associated genes tested were more prevalent in NDR isolates, and followed by SDR and MDR isolates. Twenty (50% MLST types in this study have previously been associated with human isolates, suggesting that these STs are potentially zoonotic. Our data enhanced the understanding of E. coli population structure and virulence association from cats. The diverse and various combinations of virulence-associated genes implied that the infection control may be challenging.

Spleen-dependent regulation of antigenic variation in malaria parasites: Plasmodium knowlesi SICAvar expression profiles in splenic and asplenic hosts.

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Stacey A Lapp

Full Text Available Antigenic variation by malaria parasites was first described in Plasmodium knowlesi, which infects humans and macaque monkeys, and subsequently in P. falciparum, the most virulent human parasite. The schizont-infected cell agglutination (SICA variant proteins encoded by the SICAvar multigene family in P. knowlesi, and Erythrocyte Membrane Protein-1 (EMP-1 antigens encoded by the var multigene family in P. falciparum, are expressed at the surface of infected erythrocytes, are associated with virulence, and serve as determinants of naturally acquired immunity. A parental P. knowlesi clone, Pk1(A+, and a related progeny clone, Pk1(B+1+, derived by an in vivo induced variant antigen switch, were defined by the expression of distinct SICA variant protein doublets of 210/190 and 205/200 kDa, respectively. Passage of SICA[+] infected erythrocytes through splenectomized rhesus monkeys results in the SICA[-] phenotype, defined by the lack of surface expression and agglutination with variant specific antisera.We have investigated SICAvar RNA and protein expression in Pk1(A+, Pk1(B+1+, and SICA[-] parasites. The Pk1(A+ and Pk1(B+1+ parasites express different distinct SICAvar transcript and protein repertoires. By comparison, SICA[-] parasites are characterized by a vast reduction in SICAvar RNA expression, the lack of full-length SICAvar transcript signals on northern blots, and correspondingly, the absence of any SICA protein detected by mass spectrometry.SICA protein expression may be under transcriptional as well as post-transcriptional control, and we show for the first time that the spleen, an organ central to blood-stage immunity in malaria, exerts an influence on these processes. Furthermore, proteomics has enabled the first in-depth characterization of SICA[+] protein phenotypes and we show that the in vivo switch from Pk1(A+ to Pk1(B+1+ parasites resulted in a complete change in SICA profiles. These results emphasize the importance of studying

aes, the gene encoding the esterase B in Escherichia coli, is a powerful phylogenetic marker of the species

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Tuffery Pierre

2009-12-01

Full Text Available Abstract Background Previous studies have established a correlation between electrophoretic polymorphism of esterase B, and virulence and phylogeny of Escherichia coli. Strains belonging to the phylogenetic group B2 are more frequently implicated in extraintestinal infections and include esterase B2 variants, whereas phylogenetic groups A, B1 and D contain less virulent strains and include esterase B1 variants. We investigated esterase B as a marker of phylogeny and/or virulence, in a thorough analysis of the esterase B-encoding gene. Results We identified the gene encoding esterase B as the acetyl-esterase gene (aes using gene disruption. The analysis of aes nucleotide sequences in a panel of 78 reference strains, including the E. coli reference (ECOR strains, demonstrated that the gene is under purifying selection. The phylogenetic tree reconstructed from aes sequences showed a strong correlation with the species phylogenetic history, based on multi-locus sequence typing using six housekeeping genes. The unambiguous distinction between variants B1 and B2 by electrophoresis was consistent with Aes amino-acid sequence analysis and protein modelling, which showed that substituted amino acids in the two esterase B variants occurred mostly at different sites on the protein surface. Studies in an experimental mouse model of septicaemia using mutant strains did not reveal a direct link between aes and extraintestinal virulence. Moreover, we did not find any genes in the chromosomal region of aes to be associated with virulence. Conclusion Our findings suggest that aes does not play a direct role in the virulence of E. coli extraintestinal infection. However, this gene acts as a powerful marker of phylogeny, illustrating the extensive divergence of B2 phylogenetic group strains from the rest of the species.

Evaluation of phytochemicals from medicinal plants of Myrtaceae family on virulence factor production by Pseudomonas aeruginosa.

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Musthafa, Khadar Syed; Sianglum, Wipawadee; Saising, Jongkon; Lethongkam, Sakkarin; Voravuthikunchai, Supayang Piyawan

2017-05-01

Virulence factors regulated by quorum sensing (QS) play a critical role in the pathogenesis of an opportunistic human pathogen, Pseudomonas aeruginosa in causing infections to the host. Hence, in the present work, the anti-virulence potential of the medicinal plant extracts and their derived phytochemicals from Myrtaceae family was evaluated against P. aeruginosa. In the preliminary screening of the tested medicinal plant extracts, Syzygium jambos and Syzygium antisepticum demonstrated a maximum inhibition in QS-dependent violacein pigment production by Chromobacterium violaceum DMST 21761. These extracts demonstrated an inhibitory activity over a virulence factor, pyoverdin, production by P. aeruginosa ATCC 27853. Gas chromatography-mass spectrometric (GC-MS) analysis revealed the presence of 23 and 12 phytochemicals from the extracts of S. jambos and S. antisepticum respectively. Three top-ranking phytochemicals, including phytol, ethyl linoleate and methyl linolenate, selected on the basis of docking score in molecular docking studies lowered virulence factors such as pyoverdin production, protease and haemolytic activities of P. aeruginosa to a significant level. In addition, the phytochemicals reduced rhamnolipid production by the organism. The work demonstrated an importance of plant-derived compounds as anti-virulence drugs to conquer P. aeruginosa virulence towards the host. © 2017 APMIS. Published by John Wiley & Sons Ltd.

Virulence of Klebsiella pneumoniae isolates harboring bla KPC-2 carbapenemase gene in a Caenorhabditis elegans model.

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Jean-Philippe Lavigne

Full Text Available Klebsiella pneumoniae carbapenemase (KPC is a carbapenemase increasingly reported worldwide in Enterobacteriaceae. The aim of this study was to analyze the virulence of several KPC-2-producing K. pneumoniae isolates. The studied strains were (i five KPC-2 clinical strains from different geographical origins, belonging to different ST-types and possessing plasmids of different incompatibility groups; (ii seven transformants obtained after electroporation of either these natural KPC plasmids or a recombinant plasmid harboring only the bla KPC-2 gene into reference strains K. pneumoniae ATCC10031/CIP53153; and (iii five clinical strains cured of plasmids. The virulence of K. pneumoniae isolates was evaluated in the Caenorhabditis elegans model. The clinical KPC producers and transformants were significantly less virulent (LT50: 5.5 days than K. pneumoniae reference strain (LT50: 4.3 days (p<0.01. However, the worldwide spread KPC-2 positive K. pneumoniae ST258 strains and reference strains containing plasmids extracted from K. pneumoniae ST258 strains had a higher virulence than KPC-2 strains belonging to other ST types (LT50: 5 days vs. 6 days, p<0.01. The increased virulence observed in cured strains confirmed this trend. The bla KPC-2 gene itself was not associated to increased virulence.

Regulation of bacterial virulence by Csr (Rsm) systems.

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Vakulskas, Christopher A; Potts, Anastasia H; Babitzke, Paul; Ahmer, Brian M M; Romeo, Tony

2015-06-01

Most bacterial pathogens have the remarkable ability to flourish in the external environment and in specialized host niches. This ability requires their metabolism, physiology, and virulence factors to be responsive to changes in their surroundings. It is no surprise that the underlying genetic circuitry that supports this adaptability is multilayered and exceedingly complex. Studies over the past 2 decades have established that the CsrA/RsmA proteins, global regulators of posttranscriptional gene expression, play important roles in the expression of virulence factors of numerous proteobacterial pathogens. To accomplish these tasks, CsrA binds to the 5' untranslated and/or early coding regions of mRNAs and alters translation, mRNA turnover, and/or transcript elongation. CsrA activity is regulated by noncoding small RNAs (sRNAs) that contain multiple CsrA binding sites, which permit them to sequester multiple CsrA homodimers away from mRNA targets. Environmental cues sensed by two-component signal transduction systems and other regulatory factors govern the expression of the CsrA-binding sRNAs and, ultimately, the effects of CsrA on secretion systems, surface molecules and biofilm formation, quorum sensing, motility, pigmentation, siderophore production, and phagocytic avoidance. This review presents the workings of the Csr system, the paradigm shift that it generated for understanding posttranscriptional regulation, and its roles in virulence networks of animal and plant pathogens. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Identification of virulence determinants for endocarditis in Streptococcus sanguinis by signature-tagged mutagenesis.

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Paik, Sehmi; Senty, Lauren; Das, Sankar; Noe, Jody C; Munro, Cindy L; Kitten, Todd

2005-09-01

Streptococcus sanguinis is a gram-positive, facultative anaerobe and a normal inhabitant of the human oral cavity. It is also one of the most common agents of infective endocarditis, a serious endovascular infection. To identify virulence factors for infective endocarditis, signature-tagged mutagenesis (STM) was applied to the SK36 strain of S. sanguinis, whose genome is being sequenced. STM allows the large-scale creation, in vivo screening, and recovery of a series of mutants with altered virulence. Screening of 800 mutants by STM identified 38 putative avirulent and 5 putative hypervirulent mutants. Subsequent molecular analysis of a subset of these mutants identified genes encoding undecaprenol kinase, homoserine kinase, anaerobic ribonucleotide reductase, adenylosuccinate lyase, and a hypothetical protein. Virulence reductions ranging from 2-to 150-fold were confirmed by competitive index assays. One putatively hypervirulent strain with a transposon insertion in an intergenic region was identified, though increased virulence was not confirmed in competitive index assays. All mutants grew comparably to SK36 in aerobic broth culture except for the homoserine kinase mutant. Growth of this mutant was restored by the addition of threonine to the medium. Mutants containing an insertion or in-frame deletion in the anaerobic ribonucleotide reductase gene failed to grow under strictly anaerobic conditions. The results suggest that housekeeping functions such as cell wall synthesis, amino acid and nucleic acid synthesis, and the ability to survive under anaerobic conditions are important virulence factors in S. sanguinis endocarditis.

Identification of Virulence Determinants for Endocarditis in Streptococcus sanguinis by Signature-Tagged Mutagenesis†

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Paik, Sehmi; Senty, Lauren; Das, Sankar; Noe, Jody C.; Munro, Cindy L.; Kitten, Todd

2005-01-01

Streptococcus sanguinis is a gram-positive, facultative anaerobe and a normal inhabitant of the human oral cavity. It is also one of the most common agents of infective endocarditis, a serious endovascular infection. To identify virulence factors for infective endocarditis, signature-tagged mutagenesis (STM) was applied to the SK36 strain of S. sanguinis, whose genome is being sequenced. STM allows the large-scale creation, in vivo screening, and recovery of a series of mutants with altered virulence. Screening of 800 mutants by STM identified 38 putative avirulent and 5 putative hypervirulent mutants. Subsequent molecular analysis of a subset of these mutants identified genes encoding undecaprenol kinase, homoserine kinase, anaerobic ribonucleotide reductase, adenylosuccinate lyase, and a hypothetical protein. Virulence reductions ranging from 2-to 150-fold were confirmed by competitive index assays. One putatively hypervirulent strain with a transposon insertion in an intergenic region was identified, though increased virulence was not confirmed in competitive index assays. All mutants grew comparably to SK36 in aerobic broth culture except for the homoserine kinase mutant. Growth of this mutant was restored by the addition of threonine to the medium. Mutants containing an insertion or in-frame deletion in the anaerobic ribonucleotide reductase gene failed to grow under strictly anaerobic conditions. The results suggest that housekeeping functions such as cell wall synthesis, amino acid and nucleic acid synthesis, and the ability to survive under anaerobic conditions are important virulence factors in S. sanguinis endocarditis. PMID:16113327

Caenorhabditis elegans reveals novel Pseudomonas aeruginosa virulence mechanism

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Utari, Putri Dwi; Quax, Wim J.

The susceptibility of Caenorhabditis elegans to different virulent phenotypes of Pseudomonas aeruginosa makes the worms an excellent model for studying host-pathogen interactions. Including the recently described liquid killing, five different killing assays are now available offering superb

Emergence as an outbreak of the HIV-1 CRF19_cpx variant in treatment-naïve patients in southern Spain.

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González-Domenech, Carmen M; Viciana, Isabel; Delaye, Luis; Mayorga, María Luisa; Palacios, Rosario; de la Torre, Javier; Jarilla, Francisco; Castaño, Manuel; Del Arco, Alfonso; Clavijo, Encarnación; Santos, Jesús

2018-01-01

CRF19_cpx is a complex circulating recombination form (CRF) of HIV-1. We describe the characteristics of an outbreak of the CRF19_cpx variant among treatment-naïve patients in southern Spain. The study was undertaken at the Virgen de la Victoria Hospital, a reference centre for the analysis of HIV-1 genotype in Malaga (Spain). Subtyping was performed through REGA v3.0 and the relationship of our CRF19_cpx sequences, among themselves and regarding other reference sequences from the same variant, was defined by phylogenetic analysis. We used PhyML program to perform a reconstruction of the phylogeny by Maximum Likelihood method as well as further confirmation of the transmission clusters by Bayesian inference. Additionally, we collected demographic, clinical and immunovirological data. Between 2011 and 2016, we detected 57 treatment-naïve patients with the CRF19_cpx variant. Of these, 55 conformed a very well-defined transmission cluster, phylogenetically close to CRF19_cpx sequences from the United Kingdom. The origin of this subtype in Malaga was dated between 2007 and 2010. Over 50% of the patients presented the non-nucleoside reverse transcriptase inhibitor G190A resistance mutation. This variant was mostly represented by young adult Spanish men who had sex with men. Almost half of them were recent seroconverters, though a similar percentage was diagnosed at a late state of HIV infection. Five cases of AIDS and one non-AIDS defined death occurred during follow-up. The majority of patients treated with first-line combination antiretroviral therapy (ART) responded. We report the largest HIV-1 CRF19_cpx cohort of treatment-naïve patients outside Cuba, almost all emerging as an outbreak in the South of Spain. Half the cases had the G190A resistance mutation. Unlike previous studies, the variant from Malaga seems less pathogenic, with few AIDS events and an excellent response to ART.

Emergence as an outbreak of the HIV-1 CRF19_cpx variant in treatment-naïve patients in southern Spain.

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Carmen M González-Domenech

Full Text Available CRF19_cpx is a complex circulating recombination form (CRF of HIV-1. We describe the characteristics of an outbreak of the CRF19_cpx variant among treatment-naïve patients in southern Spain.The study was undertaken at the Virgen de la Victoria Hospital, a reference centre for the analysis of HIV-1 genotype in Malaga (Spain. Subtyping was performed through REGA v3.0 and the relationship of our CRF19_cpx sequences, among themselves and regarding other reference sequences from the same variant, was defined by phylogenetic analysis. We used PhyML program to perform a reconstruction of the phylogeny by Maximum Likelihood method as well as further confirmation of the transmission clusters by Bayesian inference. Additionally, we collected demographic, clinical and immunovirological data.Between 2011 and 2016, we detected 57 treatment-naïve patients with the CRF19_cpx variant. Of these, 55 conformed a very well-defined transmission cluster, phylogenetically close to CRF19_cpx sequences from the United Kingdom. The origin of this subtype in Malaga was dated between 2007 and 2010. Over 50% of the patients presented the non-nucleoside reverse transcriptase inhibitor G190A resistance mutation. This variant was mostly represented by young adult Spanish men who had sex with men. Almost half of them were recent seroconverters, though a similar percentage was diagnosed at a late state of HIV infection. Five cases of AIDS and one non-AIDS defined death occurred during follow-up. The majority of patients treated with first-line combination antiretroviral therapy (ART responded.We report the largest HIV-1 CRF19_cpx cohort of treatment-naïve patients outside Cuba, almost all emerging as an outbreak in the South of Spain. Half the cases had the G190A resistance mutation. Unlike previous studies, the variant from Malaga seems less pathogenic, with few AIDS events and an excellent response to ART.

Distribution of antimicrobial resistance determinants, virulence-associated factors and clustered regularly interspaced palindromic repeats loci in isolates of Enterococcus faecalis from various settings and genetic lineages.

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Gawryszewska, Iwona; Malinowska, Katarzyna; Kuch, Alicja; Chrobak-Chmiel, Dorota; Trokenheim, Lucja Laniewska-; Hryniewicz, Waleria; Sadowy, Ewa

2017-03-01

Enterococcus faecalis represents an important factor of hospital-associated infections (HAIs). The knowledge on its evolution from a commensal to an opportunistic pathogen is still limited; thus, we performed a study to characterise distribution of factors that may contribute to this adaptation. Using a collection obtained from various settings (hospitalised patients, community carriers, animals, fresh food, sewage, water), we investigated differences in antimicrobial susceptibility, distribution of antimicrobial resistance genes, virulence-associated determinants and phenotypes, and CRISPR loci in the context of the clonal relatedness of isolates. Bayesian Analysis of Population Structure revealed the presence of three major groups; two subgroups comprised almost exclusively HAI isolates, belonging to previously proposed enterococcal high-risk clonal complexes (HiRECCs) 6 and 28. Isolates of these two subgroups were significantly enriched in antimicrobial resistance genes, presumably produced a polysaccharide capsule and often carried the aggregation substance asa1; distribution of other virulence-associated genes, such as esp and cyl, formation of a biofilm and gelatinase production were more variable. Moreover, both subgroups showed a low prevalence of CRISPR-Cas 1 and 3 and presence of small CRISPR2 variants. Our study confirms the importance of HiRECCs in the population of E. faecalis and their confinement to the hospital settings. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Three Herpes Simplex Virus Type 1 Latency-Associated Transcript Mutants with Distinct and Asymmetric Effects on Virulence in Mice Compared with Rabbits

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Perng, Guey-Chuen; Esmaili, Daniel; Slanina, Susan M.; Yukht, Ada; Ghiasi, Homayon; Osorio, Nelson; Mott, Kevin R.; Maguen, Barak; Jin, Ling; Nesburn, Anthony B.; Wechsler, Steven L.

2001-01-01

Herpes simplex virus type 1 latency-associated transcript (LAT)-null mutants have decreased reactivation but normal virulence in rabbits and mice. We report here on dLAT1.5, a mutant with LAT nucleotides 76 to 1667 deleted. Following ocular infection of rabbits, dLAT1.5 reactivated at a lower rate than its wild-type parent McKrae (6.1 versus 11.8%; P = 0.0025 [chi-square test]). Reactivation was restored in the marker-rescued virus dLAT1.5R (12.6%; P = 0.53 versus wild type), confirming the importance of the deleted region in spontaneous reactivation. Compared with wild-type or marker-rescued virus, dLAT1.5 had similar or slightly reduced virulence in rabbits (based on survival following ocular infection). In contrast, in mice, dLAT1.5 had increased virulence (P Wechsler, J. Virol. 73:920–929, 1999), had decreased virulence in mice (P = 0.03). In addition, we also found that dLAT371, a LAT mutant that we previously reported to have wild-type virulence in rabbits (G. C. Perng, S. M. Slanina, H. Ghiasi, A. B. Nesburn, and S. L. Wechsler, J. Virol. 70:2014–2018, 1996), had decreased virulence in mice (P < 0.05). Thus, these three mutants, each of which encodes a different LAT RNA, have different virulence phenotypes. dLAT1.5 had wild-type virulence in rabbits but increased virulence in mice. In contrast, LAT2.9A had increased virulence in rabbits but decreased virulence in mice, and dLAT371 had wild-type virulence in rabbits but decreased virulence in mice. Taken together, these results suggest that (i) the 5′ end of LAT and/or a gene that overlaps part of this region is involved in viral virulence, (ii) this virulence appears to have species-specific effects, and (iii) regulation of this virulence may be complex. PMID:11533165

Congenital anomalies and normal skeletal variants

International Nuclear Information System (INIS)

Guebert, G.M.; Yochum, T.R.; Rowe, L.J.

1987-01-01

Congenital anomalies and normal skeletal variants are a common occurrence in clinical practice. In this chapter a large number of skeletal anomalies of the spine and pelvis are reviewed. Some of the more common skeletal anomalies of the extremities are also presented. The second section of this chapter deals with normal skeletal variants. Some of these variants may simulate certain disease processes. In some instances there are no clear-cut distinctions between skeletal variants and anomalies; therefore, there may be some overlap of material. The congenital anomalies are presented initially with accompanying text, photos, and references, beginning with the skull and proceeding caudally through the spine to then include the pelvis and extremities. The normal skeletal variants section is presented in an anatomical atlas format without text or references

Development of genetic tools for in vivo virulence analysis of Streptococcus sanguinis.

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Turner, Lauren Senty; Das, Sankar; Kanamoto, Taisei; Munro, Cindy L; Kitten, Todd

2009-08-01

Completion of the genome sequence of Streptococcus sanguinis SK36 necessitates tools for further characterization of this species. It is often desirable to insert antibiotic resistance markers and other exogenous genes into the chromosome; therefore, we sought to identify a chromosomal site for ectopic expression of foreign genes, and to verify that insertion into this site did not affect important cellular phenotypes. We designed three plasmid constructs for insertion of erm, aad9 or tetM resistance determinants into a genomic region encoding only a small (65 aa) hypothetical protein. To determine whether this insertion affected important cellular properties, SK36 and its erythromycin-resistant derivative, JFP36, were compared for: (i) growth in vitro, (ii) genetic competence, (iii) biofilm formation and (iv) virulence for endocarditis in the rabbit model of infective endocarditis (IE). The spectinomycin-resistant strain, JFP56, and tetracycline-resistant strain, JFP76, were also tested for virulence in vivo. Insertion of erm did not affect growth, competence or biofilm development of JFP36. Recovery of bacteria from heart valves of co-inoculated rabbits was similar to wild-type for JFP36, JFP56 and JFP76, indicating that IE virulence was not significantly affected. The capacity for mutant complementation in vivo was explored in an avirulent ssaB mutant background. Expression of ssaB from its predicted promoter in the target region restored IE virulence. Thus, the chromosomal site utilized is a good candidate for further manipulations of S. sanguinis. In addition, the resistant strains developed may be further applied as controls to facilitate screening for virulence factors in vivo.

The supposedly attenuated Hy-HK variant of highly virulent Hypr strain of Tick-borne encephalitis virus is obviously a strain of Langat virus

Czech Academy of Sciences Publication Activity Database

Růžek, Daniel; Štěrba, Ján; Kopecký, Jan; Grubhoffer, Libor

2006-01-01

Roč. 50, č. 4 (2006), s. 277-278 ISSN 0001-723X R&D Projects: GA ČR(CZ) GA524/06/1479 Grant - others:Grant Agency of the University of South Bohemia(CZ) 35/2005/P-BF Institutional research plan: CEZ:AV0Z60220518 Keywords : TBE virus * Langat virus * Hy-HK attenuated variant Subject RIV: GJ - Animal Vermins ; Diseases, Veterinary Medicine Impact factor: 0.788, year: 2006

Phenotypic Characteristics Associated with Virulence of Clinical Isolates from the Sporothrix Complex

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Almeida-Paes, Rodrigo; de Oliveira, Luã Cardoso; Oliveira, Manoel Marques Evangelista; Gutierrez-Galhardo, Maria Clara; Nosanchuk, Joshua Daniel; Zancopé-Oliveira, Rosely Maria

2015-01-01

The Sporothrix complex members cause sporotrichosis, a subcutaneous mycosis with a wide spectrum of clinical manifestations. Several specific phenotypic characteristics are associated with virulence in many fungi, but studies in this field involving the Sporothrix complex species are scarce. Melanization, thermotolerance, and production of proteases, catalase, and urease were investigated in 61 S. brasiliensis, one S. globosa, and 10 S. schenckii strains. The S. brasiliensis strains showed a higher expression of melanin and urease compared with S. schenckii. These two species, however, presented similar thermotolerances. Our S. globosa strain had low expression of all studied virulence factors. The relationship between these phenotypes and clinical aspects of sporotrichosis was also evaluated. Strains isolated from patients with spontaneous regression of infection were heavily melanized and produced high urease levels. Melanin was also related to dissemination of internal organs and protease production was associated with HIV-coinfection. A murine sporotrichosis model showed that a S. brasiliensis strain with high expression of virulence factors was able to disseminate and yield a high fungal burden in comparison with a control S. schenckii strain. Our results show that virulence-related phenotypes are variably expressed within the Sporothrix complex species and might be involved in clinical aspects of sporotrichosis. PMID:25961005

Virulence factor genotypes of Helicobacter pylori affect cure rates of eradication therapy.

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Sugimoto, Mitsushige; Yamaoka, Yoshio

2009-01-01

The cure rates of Helicobacter pylori infection by using a combination of a proton pump inhibitor (PPI) and antimicrobial agents are mainly influenced by bacterial susceptibility to antimicrobial agents and the magnitude of acid inhibition during the treatment. Currently used empirical triple therapies do not reliably produce a > or =80% cure rate on an intention-to-treat basis. Therefore, tailored regimens based on relevant microbiological findings and pharmacogenomics are recommended for attaining an acceptable > or =95% cure rate. Recently, virulence factors of H. pylori, such as cagA and vacA, are reported to be major factors determining the cure rates. Individuals infected with strains with cagA-negative and vacA s2 genotypes have significantly increased risk of eradication failure of H. pylori infection. These virulence factors enhance gastric mucosal inflammation and are associated with the development of peptic ulcer and gastric cancer. H. pylori virulence factors induce proinflammatory cytokines, such as interleukin (IL)-1, IL-8, and tumor necrosis factor (TNF)- which influence mucosal inflammation and/or gastric acid secretion. When physicians select an H. pylori eradication regimen with an acceptable cure rate, they might need to consider H. pylori virulence factors, especially cagA and vacA.

The Clinical Correlations of Helicobacter pylori Virulence Factors and Chronic Spontaneous Urticaria

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Yi-Chun Chiu

2013-01-01

Full Text Available Background and Study Aims. The association between Helicobacter pylori (H. pylori and chronic spontaneous urticaria (CSU remains controversial. This study explored the role of H. pylori in CSU among different virulent genotypes patients. Patients and Methods. Patients infected by H. pylori were sorted into two groups as group A (with CSU and group B (without CSU. The tissue materials were taken via endoscopy for polymerase chain reaction study to determine virulence factors. After H. pylori eradication therapy, the eradication rate and response of urticaria were evaluated by using C13-UBT and a three-point scale (complete remission, partial remission, or no improvement. Results. The results were comparable between patients of groups A and B in terms of H. pylori infection rates and eradication rate. Longitudinal follow-up of 23.5 months showed complete remission of urticaria in 63.6% but no improvement in 36.4% of the patients after H. pylori eradication. H. pylori infected patients with different virulence factors such as cytotoxin-associated gene A, vacuolating cytotoxin gene A signal region and middle region have similar remission rates for CSU. Conclusions. Current study suggests that H. pylori may play a role in the development and disease course of CSU but may be irrelevant to different virulent genotypes.

Evaluation of a FRET-peptide substrate to predict virulence in Pseudomonas aeruginosa.

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Wendy E Kaman

Full Text Available Pseudomonas aeruginosa produces a number of proteases that are associated with virulence and disease progression. A substrate able to detect P. aeruginosa-specific proteolytic activity could help to rapidly alert clinicians to the virulence potential of individual P. aeruginosa strains. For this purpose we designed a set of P. aeruginosa-specific fluorogenic substrates, comprising fluorescence resonance energy transfer (FRET-labeled peptides, and evaluated their applicability to P. aeruginosa virulence in a range of clinical isolates. A FRET-peptide comprising three glycines (3xGly was found to be specific for the detection of P. aeruginosa proteases. Further screening of 97 P. aeruginosa clinical isolates showed a wide variation in 3xGly cleavage activity. The absence of 3xGly degradation by a lasI knock out strain indicated that 3xGly cleavage by P. aeruginosa could be quorum sensing (QS-related, a hypothesis strengthened by the observation of a strong correlation between 3xGly cleavage, LasA staphylolytic activity and pyocyanin production. Additionally, isolates able to cleave 3xGly were more susceptible to the QS inhibiting antibiotic azithromycin (AZM. In conclusion, we designed and evaluated a 3xGly substrate possibly useful as a simple tool to predict virulence and AZM susceptibility.

Prevalence of deleterious germline variants in risk genes including BRCA1/2 in consecutive ovarian cancer patients (AGO-TR-1.

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Philipp Harter

Full Text Available Identification of families at risk for ovarian cancer offers the opportunity to consider prophylactic surgery thus reducing ovarian cancer mortality. So far, identification of potentially affected families in Germany was solely performed via family history and numbers of affected family members with breast or ovarian cancer. However, neither the prevalence of deleterious variants in BRCA1/2 in ovarian cancer in Germany nor the reliability of family history as trigger for genetic counselling has ever been evaluated.Prospective counseling and germline testing of consecutive patients with primary diagnosis or with platinum-sensitive relapse of an invasive epithelial ovarian cancer. Testing included 25 candidate and established risk genes. Among these 25 genes, 16 genes (ATM, BRCA1, BRCA2, CDH1, CHEK2, MLH1, MSH2, MSH6, NBN, PMS2, PTEN, PALB2, RAD51C, RAD51D, STK11, TP53 were defined as established cancer risk genes. A positive family history was defined as at least one relative with breast cancer or ovarian cancer or breast cancer in personal history.In total, we analyzed 523 patients: 281 patients with primary diagnosis of ovarian cancer and 242 patients with relapsed disease. Median age at primary diagnosis was 58 years (range 16-93 and 406 patients (77.6% had a high-grade serous ovarian cancer. In total, 27.9% of the patients showed at least one deleterious variant in all 25 investigated genes and 26.4% in the defined 16 risk genes. Deleterious variants were most prevalent in the BRCA1 (15.5%, BRCA2 (5.5%, RAD51C (2.5% and PALB2 (1.1% genes. The prevalence of deleterious variants did not differ significantly between patients at primary diagnosis and relapse. The prevalence of deleterious variants in BRCA1/2 (and in all 16 risk genes in patients <60 years was 30.2% (33.2% versus 10.6% (18.9% in patients ≥60 years. Family history was positive in 43% of all patients. Patients with a positive family history had a prevalence of deleterious variants

Bistable expression of virulence genes in salmonella leads to the formation of an antibiotic-tolerant subpopulation.

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Markus Arnoldini

2014-08-01

Full Text Available Phenotypic heterogeneity can confer clonal groups of organisms with new functionality. A paradigmatic example is the bistable expression of virulence genes in Salmonella typhimurium, which leads to phenotypically virulent and phenotypically avirulent subpopulations. The two subpopulations have been shown to divide labor during S. typhimurium infections. Here, we show that heterogeneous virulence gene expression in this organism also promotes survival against exposure to antibiotics through a bet-hedging mechanism. Using microfluidic devices in combination with fluorescence time-lapse microscopy and quantitative image analysis, we analyzed the expression of virulence genes at the single cell level and related it to survival when exposed to antibiotics. We found that, across different types of antibiotics and under concentrations that are clinically relevant, the subpopulation of bacterial cells that express virulence genes shows increased survival after exposure to antibiotics. Intriguingly, there is an interplay between the two consequences of phenotypic heterogeneity. The bet-hedging effect that arises through heterogeneity in virulence gene expression can protect clonal populations against avirulent mutants that exploit and subvert the division of labor within these populations. We conclude that bet-hedging and the division of labor can arise through variation in a single trait and interact with each other. This reveals a new degree of functional complexity of phenotypic heterogeneity. In addition, our results suggest a general principle of how pathogens can evade antibiotics: Expression of virulence factors often entails metabolic costs and the resulting growth retardation could generally increase tolerance against antibiotics and thus compromise treatment.

Multiple plasmid-borne virulence genes of Clavibacter michiganensis ssp. capsici critical for disease development in pepper.

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Hwang, In Sun; Oh, Eom-Ji; Kim, Donghyuk; Oh, Chang-Sik

2018-02-01

Clavibacter michiganensis ssp. capsici is a Gram-positive plant-pathogenic bacterium causing bacterial canker disease in pepper. Virulence genes and mechanisms of C. michiganensis ssp. capsici in pepper have not yet been studied. To identify virulence genes of C. michiganensis ssp. capsici, comparative genome analyses with C. michiganensis ssp. capsici and its related C. michiganensis subspecies, and functional analysis of its putative virulence genes during infection were performed. The C. michiganensis ssp. capsici type strain PF008 carries one chromosome (3.056 Mb) and two plasmids (39 kb pCM1 Cmc and 145 kb pCM2 Cmc ). The genome analyses showed that this bacterium lacks a chromosomal pathogenicity island and celA gene that are important for disease development by C. michiganensis ssp. michiganensis in tomato, but carries most putative virulence genes in both plasmids. Virulence of pCM1 Cmc -cured C. michiganensis ssp. capsici was greatly reduced compared with the wild-type strain in pepper. The complementation analysis with pCM1 Cmc -located putative virulence genes showed that at least five genes, chpE, chpG, ppaA1, ppaB1 and pelA1, encoding serine proteases or pectate lyase contribute to disease development in pepper. In conclusion, C. michiganensis ssp. capsici has a unique genome structure, and its multiple plasmid-borne genes play critical roles in virulence in pepper, either separately or together. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Common Virulence Factors and Tissue Targets of Entomopathogenic Bacteria for Biological Control of Lepidopteran Pests

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Anaïs Castagnola

2014-01-01

Full Text Available This review focuses on common insecticidal virulence factors from entomopathogenic bacteria with special emphasis on two insect pathogenic bacteria Photorhabdus (Proteobacteria: Enterobacteriaceae and Bacillus (Firmicutes: Bacillaceae. Insect pathogenic bacteria of diverse taxonomic groups and phylogenetic origin have been shown to have striking similarities in the virulence factors they produce. It has been suggested that the detection of phage elements surrounding toxin genes, horizontal and lateral gene transfer events, and plasmid shuffling occurrences may be some of the reasons that virulence factor genes have so many analogs throughout the bacterial kingdom. Comparison of virulence factors of Photorhabdus, and Bacillus, two bacteria with dissimilar life styles opens the possibility of re-examining newly discovered toxins for novel tissue targets. For example, nematodes residing in the hemolymph may release bacteria with virulence factors targeting neurons or neuromuscular junctions. The first section of this review focuses on toxins and their context in agriculture. The second describes the mode of action of toxins from common entomopathogens and the third draws comparisons between Gram positive and Gram negative bacteria. The fourth section reviews the implications of the nervous system in biocontrol.

Evaluation of the role of SNCA variants in survival without neurological disease.

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Michael G Heckman

Full Text Available A variety of definitions of successful aging have been proposed, many of which relate to longevity, freedom from disease and disability, or preservation of high physical and cognitive function. Many behavioral, biomedical, and psychological factors have been linked with these various measures of successful aging, however genetic predictors are less understood. Parkinson's disease (PD is an age-related neurodegenerative disorder, and variants in the α-synuclein gene (SNCA affect susceptibility to PD. This exploratory study examined whether SNCA variants may also promote successful aging as defined by survival without neurological disease.We utilized 769 controls without neurological disease (Mean age: 79 years, Range: 33-99 years and examined the frequency of 20 different SNCA variants across age groups using logistic regression models. We also included 426 PD cases to assess the effect of these variants on PD risk.There was a significant decline in the proportion of carriers of the minor allele of rs10014396 as age increased (P = 0.021, from 30% in controls younger than 60 to 14% in controls 90 years of age or older. Findings were similar for rs3775439, where the proportion of carriers of the minor allele declined from 32% in controls less than 60 years old to 19% in those 90 or older (P = 0.025. A number of SNCA variants, not including rs10014396 or rs3775439, were significantly associated with susceptibility to PD.In addition to its documented roles in PD and α-synucleinopathies, our results suggest that SNCA has a role in survival free of neurological disease. Acknowledging that our findings would not have withstood correction for multiple testing, validation in an independent series of aged neurologically normal controls is needed.

Fine-Mapping of Common Genetic Variants Associated with Colorectal Tumor Risk Identified Potential Functional Variants.

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Mengmeng Du

Full Text Available Genome-wide association studies (GWAS have identified many common single nucleotide polymorphisms (SNPs associated with colorectal cancer risk. These SNPs may tag correlated variants with biological importance. Fine-mapping around GWAS loci can facilitate detection of functional candidates and additional independent risk variants. We analyzed 11,900 cases and 14,311 controls in the Genetics and Epidemiology of Colorectal Cancer Consortium and the Colon Cancer Family Registry. To fine-map genomic regions containing all known common risk variants, we imputed high-density genetic data from the 1000 Genomes Project. We tested single-variant associations with colorectal tumor risk for all variants spanning genomic regions 250-kb upstream or downstream of 31 GWAS-identified SNPs (index SNPs. We queried the University of California, Santa Cruz Genome Browser to examine evidence for biological function. Index SNPs did not show the strongest association signals with colorectal tumor risk in their respective genomic regions. Bioinformatics analysis of SNPs showing smaller P-values in each region revealed 21 functional candidates in 12 loci (5q31.1, 8q24, 11q13.4, 11q23, 12p13.32, 12q24.21, 14q22.2, 15q13, 18q21, 19q13.1, 20p12.3, and 20q13.33. We did not observe evidence of additional independent association signals in GWAS-identified regions. Our results support the utility of integrating data from comprehensive fine-mapping with expanding publicly available genomic databases to help clarify GWAS associations and identify functional candidates that warrant more onerous laboratory follow-up. Such efforts may aid the eventual discovery of disease-causing variant(s.

Critical role of LuxS in the virulence of Campylobacter jejuni in a guinea pig model of abortion.

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Plummer, Paul; Sahin, Orhan; Burrough, Eric; Sippy, Rachel; Mou, Kathy; Rabenold, Jessica; Yaeger, Mike; Zhang, Qijing

2012-02-01

Previous studies on Campylobacter jejuni have demonstrated the role of LuxS in motility, cytolethal distending toxin production, agglutination, and intestinal colonization; however, its direct involvement in virulence has not been reported. In this study, we demonstrate a direct role of luxS in the virulence of C. jejuni in two different animal hosts. The IA3902 strain, a highly virulent sheep abortion strain recently described by our laboratory, along with its isogenic luxS mutant and luxS complement strains, was inoculated by the oral route into both a pregnant guinea pig virulence model and a chicken colonization model. In both cases, the IA3902 luxS mutant demonstrated a complete loss of ability to colonize the intestinal tract. In the pregnant model, the mutant also failed to induce abortion, while the wild-type strain was highly abortifacient. Genetic complementation of the luxS gene fully restored the virulent phenotype in both models. Interestingly, when the organism was inoculated into guinea pigs by the intraperitoneal route, no difference in virulence (abortion induction) was observed between the luxS mutant and the wild-type strain, suggesting that the defect in virulence following oral inoculation is likely associated with a defect in colonization and/or translocation of the organism out of the intestine. These studies provide the first direct evidence that LuxS plays an important role in the virulence of C. jejuni using an in vivo model of natural disease.

Virulence determinants within the E2 glycoprotein of Classical Swine Fever Virus

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Johnston, Camille Melissa; Fahnøe, Ulrik; Lohse, Louise

Classical Swine Fever is a highly contagious disease of pigs caused by Classical Swine Fever Virus (CSFV), a member of the pestivirus genus within the family Flaviviridae. The E2 glycoprotein of CSFV has been shown to be an important factor for the virulence of the virus. In a recent study, we have......Kos (with the SL motif). The results indicate that the E2 residues 763-64 play an important role in CSFV virulence....

Characterization of coding synonymous and non-synonymous variants in ADAMTS13 using ex vivo and in silico approaches.

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Nathan C Edwards

Full Text Available Synonymous variations, which are defined as codon substitutions that do not change the encoded amino acid, were previously thought to have no effect on the properties of the synthesized protein(s. However, mounting evidence shows that these "silent" variations can have a significant impact on protein expression and function and should no longer be considered "silent". Here, the effects of six synonymous and six non-synonymous variations, previously found in the gene of ADAMTS13, the von Willebrand Factor (VWF cleaving hemostatic protease, have been investigated using a variety of approaches. The ADAMTS13 mRNA and protein expression levels, as well as the conformation and activity of the variants have been compared to that of wild-type ADAMTS13. Interestingly, not only the non-synonymous variants but also the synonymous variants have been found to change the protein expression levels, conformation and function. Bioinformatic analysis of ADAMTS13 mRNA structure, amino acid conservation and codon usage allowed us to establish correlations between mRNA stability, RSCU, and intracellular protein expression. This study demonstrates that variants and more specifically, synonymous variants can have a substantial and definite effect on ADAMTS13 function and that bioinformatic analysis may allow development of predictive tools to identify variants that will have significant effects on the encoded protein.

Short-sighted evolution of virulence in parasitic honeybee workers ( Apis mellifera capensis Esch.)

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Moritz, Robin F. A.; Pirk, Christian W. W.; Hepburn, H. Randall; Neumann, Peter

2008-06-01

The short-sighted selection hypothesis for parasite virulence predicts that winners of within-host competition are poorer at transmission to new hosts. Social parasitism by self-replicating, female-producing workers occurs in the Cape honeybee Apis mellifera capensis, and colonies of other honeybee subspecies are susceptible hosts. We found high within-host virulence but low transmission rates in a clone of social parasitic A. m. capensis workers invading the neighbouring subspecies A. m. scutellata. In contrast, parasitic workers from the endemic range of A. m. capensis showed low within-host virulence but high transmission rates. This suggests a short-sighted selection scenario for the host-parasite co-evolution in the invasive range of the Cape honeybee, probably facilitated by beekeeping-assisted parasite transmission in apiaries.

All Yersinia enterocolitica are pathogenic: virulence of phylogroup 1 Y. enterocolitica in a Galleria mellonella infection model.

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Alenizi, Dhahi; Ringwood, Tamara; Redhwan, Alya; Bouraha, Bouchra; Wren, Brendan W; Prentice, Michael; McNally, Alan

2016-08-01

Yersinia enterocolitica is a zoonotic pathogen and a common cause of gastroenteritis in humans. The species is composed of six diverse phylogroups, of which strains of phylogroup 1 are considered non-pathogenic to mammals due to the lack of the major virulence plasmid pYV, and their lack of virulence in a mouse infection model. In the present report we present data examining the pathogenicity of strains of Y. enterocolitica across all six phylogroups in a Galleria mellonellla model. We have demonstrated that in this model strains of phylogroup 1 exhibit severe pathogenesis with a lethal dose of as low as 10 c.f.u., that this virulence is an active process and that flagella play a major role in the virulence phenotype. We have also demonstrated that the complete lack of virulence in Galleria of the mammalian pathogenic phylogroups is not due to carriage of the pYV virulence plasmid. Our data suggest that all Y. enterocolitica can be pathogenic, which may be a reflection of the true natural habitat of the species, and that we may need to reconsider the eco-evo perspective of this important bacterial species.

Bacterial Human Virulence Genes across Diverse Habitats As Assessed by In silico Analysis of Environmental Metagenomes

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Søborg, Ditte A; Hendriksen, Niels B; Kilian, Mogens

2016-01-01

of natural environments in the evolution of bacterial virulence. Twenty four bacterial virulence genes were analyzed in 46 diverse environmental metagenomic datasets, representing various soils, seawater, freshwater, marine sediments, hot springs, the deep-sea, hypersaline mats, microbialites, gutless worms......The occurrence and distribution of clinically relevant bacterial virulence genes across natural (non-human) environments is not well understood. We aimed to investigate the occurrence of homologs to bacterial human virulence genes in a variety of ecological niches to better understand the role...... in non-human environments point to an important ecological role of the genes for the activity and survival of environmental bacteria. Furthermore, the high degree of sequence conservation between several of the environmental and clinical genes suggests common ancestral origins....

Spontaneous Loss of Virulence in Natural Populations of Listeria monocytogenes.

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

2017-11-01

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

Typing and virulence factors of food-borne Candida spp. isolates.

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Rajkowska, Katarzyna; Kunicka-Styczyńska, Alina

2018-08-20

Food-borne yeasts, excluding yeasts used as starter cultures, are commonly considered as food spoilage microorganisms. However, the incidence of non-C. albicans Candida (NCAC) infections has increased considerably over the past two decades. Although 15 Candida species are frequently identified as pathogens, a threat to human from food-borne Candida is poorly recognized. In the present study food-borne NCAC were characterized for the virulence factors, known to be associated with yeast pathogenicity. All food-borne strains in planktonic forms and 89% in biofilm structures represented biotypes established for C. albicans, and 61% demonstrated hemolytic activity. 56-94% of food-borne isolates formed biofilms on glass and biomaterials at a level comparable to clinical C. albicans. Nine out of eighteen tested food-borne NCAC strains (C. krusei, C. lusitaniae, C. famata, C. colliculosa, C. parapsilosis, C. tropicalis) showed similarity to clinical C. albicans in terms of their biotypes and the tested virulence factors, allocating them in a group of risk of potential pathogens. However, their capacity to grow at 37 °C seems to be the preliminary criterion in the study of potential virulence of food-borne yeasts. Copyright © 2018 Elsevier B.V. All rights reserved.

An investigation of virulence factors of Legionella pneumophila environmental isolates

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Elif Özlem Arslan-Aydoğdu

Full Text Available ABSTRACT Nine Legionella pneumophila strains isolated from cooling towers and a standard strain (L. pneumophila serogroup 1, ATCC 33152, Philadelphia 1 were analyzed and compared in terms of motility, flagella structure, ability to form biofilms, enzymatic activities (hemolysin, nucleases, protease, phospholipase A, phospholipase C, acid phosphatase, alkaline phosphatase and lipase, hemagglutination capabilities, and pathogenicity in various host cells (Acanthamoeba castellanii ATCC 30234, mouse peritoneal macrophages and human peripheral monocytes. All the isolates of bacteria appeared to be motile and polar-flagellated and possessed the type-IV fimbria. Upon the evaluation of virulence factors, isolate 4 was found to be the most pathogenic strain, while 6 out of the 9 isolates (the isolates 1, 2, 3, 4, 5, and 7 were more virulent than the ATCC 33152 strain. The different bacterial strains exhibited differences in properties such as adhesion, penetration and reproduction in the hosts, and preferred host type. To our knowledge, this is the first study to compare the virulence of environmental L. pneumophila strains isolated in Turkey, and it provides important information relevant for understanding the epidemiology of L. pneumophila.

Molecular serotyping, virulence gene profiling and pathogenicity of Streptococcus agalactiae isolated from tilapia farms in Thailand by multiplex PCR.

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Kannika, K; Pisuttharachai, D; Srisapoome, P; Wongtavatchai, J; Kondo, H; Hirono, I; Unajak, S; Areechon, N

2017-06-01

This study aimed to biotype Streptococcus agalactiae isolated from tilapia farms in Thailand based on molecular biotyping methods and to determine the correlation between the serotype and virulence of bacteria. In addition to a biotyping (serotyping) technique based on multiplex PCR of cps genes, in this study, we developed multiplex PCR typing of Group B streptococcus (GBS) virulence genes to examine three clusters of virulence genes and their correlation with the pathogenicity of S. agalactiae. The epidemiology of S. agalactiae in Thailand was analysed to provide bacterial genetic information towards a future rational vaccine strategy for tilapia culture systems. Streptococcus agalactiae were isolated from diseased tilapia from different areas of Thailand. A total of 124 S. agalactiae isolates were identified by phenotypic analysis and confirmed by 16S rRNA PCR. Bacterial genotyping was conducted based on (i) molecular serotyping of the capsular polysaccharide (cps) gene cluster and (ii) virulence gene profiling using multiplex PCR analysis of 14 virulence genes (lmb, scpB, pavA, cspA, spb1, cyl, bca, rib, fbsA, fbsB, cfb, hylB, bac and pbp1A/ponA). Only serotypes Ia and III were found in this study; serotype Ia lacks the lmb, scpB and spb1 genes, whereas serotype III lacks only the bac gene. Virulence tests in juvenile Nile tilapia demonstrated a correlation between the pathogenicity of the bacteria and their virulence gene profile, with serotype III showing higher virulence than serotype Ia. Epidemiological analysis showed an almost equal distribution in all regions of Thailand, except serotype III was found predominantly in the southern areas. Only two serotypes of S. agalactiae were isolated from diseased tilapia in Thailand. Serotype Ia showed fewer virulence genes and lower virulence than serotype III. Both serotypes showed a similar distribution throughout Thailand. We identified two major serotypes of S. agalactiae isolates associated with the outbreak in

Identification of immunogenic and virulence-associated Campylobacter jejuni proteins

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Nielsen, Lene Nørby; Luijkx, Thomas A.; Vegge, Christina Skovgaard

2012-01-01

With the aim of identifying proteins important for host interaction and virulence, we have screened an expression library of NCTC 11168 Campylobacter jejuni genes for highly immunogenic proteins. A commercial C. jejuni open reading frame (ORF) library consisting of more than 1,600 genes was trans......With the aim of identifying proteins important for host interaction and virulence, we have screened an expression library of NCTC 11168 Campylobacter jejuni genes for highly immunogenic proteins. A commercial C. jejuni open reading frame (ORF) library consisting of more than 1,600 genes...

Virulence factor genes possessing Enterococcus faecalis strains from rabbits and their sensitivity to enterocins

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M. Pogány Simonová

2017-03-01

Full Text Available Information concerning the virulence factor genes and antibiotic resistance of rabbit enterococci is limited, so in this study we tested the virulence factor genes in Enterococcus faecalis strains from rabbits. Moreover, their resistance/sensitivity to antibiotics and sensitivity to enterocins was also tested, with the aim of contributing to our enterocin spectra study and to indicate the possibility of enterocin application in prevention or contaminant elimination in rabbit husbandry. A total of 144 rabbit samples were treated using a standard microbiological method. Thirty-one pure colonies of the species Enterococcus faecalis were identified, using the MALDI-TOF identification system and confirmed using phenotyping, among which 15 strains were virulence factor gene absent. The gelE gene was the most detected (42%; however, the expression of gelatinase phenotype did not always correlate with the detection of gelE. Strains did not show ß-haemolysis and were mostly resistant to tested antibiotics, but sensitive to enterocins (Ent, mainly to Ents EK13=A (P, 2019 and Ent M. Rabbit E. faecalis strains displayed antibiotic resistant traits and the presence of expressed and silent virulence genes, but they showed high levels of sensitivity to natural antimicrobials-enterocins, which indicates the possible prevention of multidrug and virulent enterococcal contaminants by enterocins.

Virulence Genes Profile of Multidrug Resistant Pseudomonas aeruginosa Isolated from Iranian Children with UTIs

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Zohreh Heidary

2016-04-01

Full Text Available Virulent and resistant strains Pseudomonas aeruginosa (P. aeruginosa is one of the most important cause of UTIs in pediatrics. The present study was carried to investigate the frequency of virulence factors in the multi-drug resistant strains of P. aeruginosa isolated from pediatrics hospitalized due to the UTIs. One - hundred and forty three urine samples were collected from pediatric patients suffered from UTIs. Samples were cultured and those that were P. aeruginosa positive were analyzed for the presence of putative virulence genes. Seventy one out of 143 samples (49.65% were positive for P. aeruginosa. Monthly, sex and age-dependent prevalence were seen for P. aeruginosa. Bacterial strains had the highest levels of resistance against ampicillin (95.77%, gentamicin (92.95% and ciprofloxacin (81.69%. Of 71 P. aeruginosa isolates, 12 strains were resistant to more than 9 antibiotics (16.90%. The most commonly detected virulence factors in the cases of urethral infections were exoU and plcH while those of pyelonephritis and cystitis were were exoS and lasB. Our findings should raise awareness about antibiotic resistance in hospitalized pediatrics with UTIs in Iran. Clinicians should exercise caution in prescribing antibiotics, especially in cases of UTIs. Such information can help in identifying these virulence genes as useful diagnostic markers for clinical P. aeruginosa strains isolated from UTIs.

Clumping factor A-mediated virulence during Staphylococcus aureus infection is retained despite fibrinogen depletion.

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Palmqvist, Niklas; Josefsson, Elisabet; Tarkowski, Andrzej

2004-02-01

Clumping factor A (ClfA), a fibrinogen-binding protein expressed on the Staphylococcus aureus cell surface, has previously been shown to act as a virulence factor in experimental septic arthritis. Although the interaction between ClfA and fibrinogen is assumed to be of importance for the virulence of S. aureus, this has not been demonstrated in any in vivo model of infection. Therefore, the objective of this study was to investigate the contribution of this interaction to ClfA-mediated virulence in murine S. aureus-induced arthritis. Ancrod, a serine protease with thrombin-like activity, was used to induce in vivo depletion of fibrinogen in mice. Ancrod treatment significantly aggravated septic arthritis following inoculation with a ClfA-expressing strain (Newman) compared to control treatment. Also, ancrod treatment tended to enhance the arthritis induced by a clfA mutant strain (DU5876), indicating that fibrinogen depletion exacerbates septic arthritis in a ClfA-independent manner. Most importantly, the ClfA-expressing strain was much more arthritogenic than the isogenic clfA mutant, following inoculation of fibrinogen-depleted mice. This finding indicates that the interaction between ClfA and free fibrinogen is not required for ClfA-mediated functions contributing to S. aureus virulence. It is conceivable that ClfA contributes to the virulence of S. aureus through interactions with other host ligands than fibrinogen.

Microarray Evaluation of Antimicrobial Resistance and Virulence of Escherichia coli Isolates from Portuguese Poultry

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Nuno Mendonça

2016-01-01

Full Text Available The presence of antimicrobial resistance and virulence factors of 174 Escherichia coli strains isolated from healthy Portuguese Gallus gallus was evaluated. Resistance profiles were determined against 33 antimicrobials by microbroth dilution. Resistance was prevalent for tetracycline (70% and ampicillin (63%. Extended-spectrum beta-lactamase (ESBL phenotype was observed in 18% of the isolates. Multidrug resistance was found in 56% of isolates. A subset of 74 isolates were screened by DNA microarrays for the carriage of 88 antibiotic resistance genes and 62 virulence genes. Overall, 37 different resistance genes were detected. The most common were tet(A (72%, blaTEM (68%, and sul1 (47%, while 21% isolates harbored an ESBL gene (blaCTX-M group 1, group 2, or group 9. Of these, 96% carried the increased serum survival (iss virulence gene, while 89% presented the enterobactin siderophore receptor protein (iroN, 70% the temperature-sensitive hemagglutinin (tsh, and 68% the long polar fimbriae (lpfA virulence genes associated with extraintestinal pathogenic E. coli. In conclusion, prevalence of antibiotic resistant E. coli from the microbiota of Portuguese chickens was high, including to extended spectrum cephalosporins. The majority of isolates seems to have the potential to trigger extraintestinal human infection due to the presence of some virulence genes. However, the absence of genes specific for enteropathogenic E. coli reduces the risk for human intestinal infection.

Survival and virulence of copper- and chlorine-stressed Yersinia enterocolitica in Experimentally infected mice

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Singh, A.; McFeters, G.A.

1987-08-01

The effect of gastric pH on the viability and virulence of Yersinia enterocolitica 0:8 after exposure to sublethal concentrations of copper and chlorine was determined in mice. Viability and injury were assessed with a nonselective TLY agar and two selective media, TLYD agar and CIN agar. Both copper and chlorine caused injury which was manifested by the inability of the cells to grow on selective media. CIN agar was more restrictive to the growth of injured cells than TLYD agar. Injury of the exposed cells was further enhanced in the gastric environment of mice. Besides injury, the low gastric pH caused extensive loss of viability in copper-exposed cells. Lethality in the chlorine-exposed cells was less extensive, and a portion of the inoculum reached the small intestine 5 min postinoculation. No adverse effect on the injured cells was apparent in the small intestine, and a substantial revival of the injury occurred in 3 to 4 h after intraluminal inoculation. The virulence of chlorine-stressed Y. enterocolitica in orally inoculated mice was similar to that of the control culture, but copper-stressed cells showed reduced virulence. Virulence was partly restored by oral administration of sodium bicarbonate before the inoculation of copper-exposed cells. Neutralization of gastric acidity had no effect on the virulence of the control of chlorine-stressed cells.

Virulence-associated genome mutations of murine rotavirus identified by alternating serial passages in mice and cell cultures.

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Tsugawa, Takeshi; Tatsumi, Masatoshi; Tsutsumi, Hiroyuki

2014-05-01

Although significant clinical efficacy and safety of rotavirus vaccines were recently revealed in many countries, the mechanism of their attenuation is not well understood. We passaged serially a cell culture-adapted murine rotavirus EB strain in mouse pups or in cell cultures alternately and repeatedly and fully sequenced all 11 genes of 21 virus samples passaged in mice or in cell cultures. Sequence analysis revealed that mouse-passaged viruses that regained virulence almost consistently acquired four kinds of amino acid (aa) substitutions in VP4 and substitution in aa 37 (Val to Ala) in NSP4. In addition, they gained and invariably conserved the 3' consensus sequence in NSP1. The molecular changes occurred along with the acquisition of virulence during passages in mice and then disappeared following passages in cell cultures. Intraperitoneal injection of recombinant NSP4 proteins confirmed the aa 37 site as important for its diarrheagenic activity in mice. These genome changes are likely to be correlated with rotavirus virulence. Serial passage of a virulent wild-type virus in vitro often results in loss of virulence of the virus in an original animal host, while serial passage of a cell culture-adapted avirulent virus in vivo often gains virulence in an animal host. Actually, live attenuated virus vaccines were originally produced by serial passage in cell cultures. Although clinical efficacy and safety of rotavirus vaccines were recently revealed, the mechanism of their attenuation is not well understood. We passaged serially a murine rotavirus by alternating switch of host (mice or cell cultures) repeatedly and sequenced the eleven genes of the passaged viruses to identify mutations associated with the emergence or disappearance of virulence. Sequence analysis revealed that changes in three genes (VP4, NSP1, and NSP4) were associated with virulence in mice. Intraperitoneal injection of recombinant NSP4 proteins confirmed its diarrheagenic activity in mice

Virulence-Associated Genome Mutations of Murine Rotavirus Identified by Alternating Serial Passages in Mice and Cell Cultures

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Tatsumi, Masatoshi; Tsutsumi, Hiroyuki

2014-01-01

ABSTRACT Although significant clinical efficacy and safety of rotavirus vaccines were recently revealed in many countries, the mechanism of their attenuation is not well understood. We passaged serially a cell culture-adapted murine rotavirus EB strain in mouse pups or in cell cultures alternately and repeatedly and fully sequenced all 11 genes of 21 virus samples passaged in mice or in cell cultures. Sequence analysis revealed that mouse-passaged viruses that regained virulence almost consistently acquired four kinds of amino acid (aa) substitutions in VP4 and substitution in aa 37 (Val to Ala) in NSP4. In addition, they gained and invariably conserved the 3′ consensus sequence in NSP1. The molecular changes occurred along with the acquisition of virulence during passages in mice and then disappeared following passages in cell cultures. Intraperitoneal injection of recombinant NSP4 proteins confirmed the aa 37 site as important for its diarrheagenic activity in mice. These genome changes are likely to be correlated with rotavirus virulence. IMPORTANCE Serial passage of a virulent wild-type virus in vitro often results in loss of virulence of the virus in an original animal host, while serial passage of a cell culture-adapted avirulent virus in vivo often gains virulence in an animal host. Actually, live attenuated virus vaccines were originally produced by serial passage in cell cultures. Although clinical efficacy and safety of rotavirus vaccines were recently revealed, the mechanism of their attenuation is not well understood. We passaged serially a murine rotavirus by alternating switch of host (mice or cell cultures) repeatedly and sequenced the eleven genes of the passaged viruses to identify mutations associated with the emergence or disappearance of virulence. Sequence analysis revealed that changes in three genes (VP4, NSP1, and NSP4) were associated with virulence in mice. Intraperitoneal injection of recombinant NSP4 proteins confirmed its

The Streptococcus sanguinis competence regulon is not required for infective endocarditis virulence in a rabbit model.

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Callahan, Jill E; Munro, Cindy L; Kitten, Todd

2011-01-01

Streptococcus sanguinis is an important component of dental plaque and a leading cause of infective endocarditis. Genetic competence in S. sanguinis requires a quorum sensing system encoded by the early comCDE genes, as well as late genes controlled by the alternative sigma factor, ComX. Previous studies of Streptococcus pneumoniae and Streptococcus mutans have identified functions for the >100-gene com regulon in addition to DNA uptake, including virulence. We investigated this possibility in S. sanguinis. Strains deleted for the comCDE or comX master regulatory genes were created. Using a rabbit endocarditis model in conjunction with a variety of virulence assays, we determined that both mutants possessed infectivity equivalent to that of a virulent control strain, and that measures of disease were similar in rabbits infected with each strain. These results suggest that the com regulon is not required for S. sanguinis infective endocarditis virulence in this model. We propose that the different roles of the S. sanguinis, S. pneumoniae, and S. mutans com regulons in virulence can be understood in relation to the pathogenic mechanisms employed by each species.

The Rcs regulon in Proteus mirabilis: implications for motility, biofilm formation, and virulence.

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Howery, Kristen E; Clemmer, Katy M; Rather, Philip N

2016-11-01

The overall role of the Rcs phosphorelay in Proteus mirabilis is largely unknown. Previous work had demonstrated that the Rcs phosphorelay represses the flhDC operon and activates the minCDE cell division inhibition system. To identify additional cellular functions regulated by the Rcs phosphorelay, an analysis of RNA-seq data was undertaken. In this report, the results of the RNA-sequencing are discussed with an emphasis on the predicted roles of the Rcs phosphorelay in swarmer cell differentiation, motility, biofilm formation, and virulence. RcsB is shown to activate genes important for differentiation and fimbriae formation, while repressing the expression of genes important for motility and virulence. Additionally, to follow up on the RNA-Seq data, we demonstrate that an rcsB mutant is deficient in its ability to form biofilm and exhibits enhanced virulence in a Galleria mellonella waxworm model. Overall, these results indicate the Rcs regulon in P. mirabilis extends beyond flagellar genes to include those involved in biofilm formation and virulence. Furthermore, the information presented in this study may provide clues to additional roles of the Rcs phosphorelay in other members of the Enterobacteriaceae.

[Effect of the 10 kb sequence of piscine Streptococcus agalactiae on bacterial virulence].

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Liu, Guangjin; Zhu, Jielian; Shi, Ziwei; Ding, Ming; Wang, Ruyi; Yao, Huochun; Lu, Chengping; Xu, Pao

2016-01-04

From the previous comparative genomic analysis, we found a specific unknown 10 kb sequence (including 11 Open reading Frames) in Chinese piscine strain GD201008-001 genome. To study the role of 10 kb in the pathogenicity of piscine S. agalactiae, the 10 kb sequence was deleted from the GD201008-001 genome. The isogenic mutant Δ10 kb was constructed by using the temperature-sensitive Streptococcus-E. coli shuttle vector pSET4s. We compared the growth characteristics, adherence to HEp-2 cell and bacterial virulence in a zebrafish infection model between wild strain and mutant. Meanwhile the expressions of the known virulence genes from GD201008-001 and Δ10 kb were also quantified by real-time PCR. The Δ10 kb showed no significant differences in bacterial morphology and adherence to HEp-2 cells compared with the wild-type strain, but the speed of growth was slightly slower than the wild strain. Furthermore the 50% lethal dose of Δ10 kb was decreased up to 10-fold (P kb sequence of piscine Streptococcus agalactiae exerts a significant effect on bacterial virulence and probably regulates the virulence genes expression of GD20 1008-001.

Annotating pathogenic non-coding variants in genic regions.

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Gelfman, Sahar; Wang, Quanli; McSweeney, K Melodi; Ren, Zhong; La Carpia, Francesca; Halvorsen, Matt; Schoch, Kelly; Ratzon, Fanni; Heinzen, Erin L; Boland, Michael J; Petrovski, Slavé; Goldstein, David B

2017-08-09

Identifying the underlying causes of disease requires accurate interpretation of genetic variants. Current methods ineffectively capture pathogenic non-coding variants in genic regions, resulting in overlooking synonymous and intronic variants when searching for disease risk. Here we present the Transcript-inferred Pathogenicity (TraP) score, which uses sequence context alterations to reliably identify non-coding variation that causes disease. High TraP scores single out extremely rare variants with lower minor allele frequencies than missense variants. TraP accurately distinguishes known pathogenic and benign variants in synonymous (AUC = 0.88) and intronic (AUC = 0.83) public datasets, dismissing benign variants with exceptionally high specificity. TraP analysis of 843 exomes from epilepsy family trios identifies synonymous variants in known epilepsy genes, thus pinpointing risk factors of disease from non-coding sequence data. TraP outperforms leading methods in identifying non-coding variants that are pathogenic and is therefore a valuable tool for use in gene discovery and the interpretation of personal genomes.While non-coding synonymous and intronic variants are often not under strong selective constraint, they can be pathogenic through affecting splicing or transcription. Here, the authors develop a score that uses sequence context alterations to predict pathogenicity of synonymous and non-coding genetic variants, and provide a web server of pre-computed scores.

The Sit-and-Wait Hypothesis in Bacterial Pathogens: A Theoretical Study of Durability and Virulence

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Liang Wang

2017-11-01

Full Text Available The intriguing sit-and-wait hypothesis predicts that bacterial durability in the external environment is positively correlated with their virulence. Since its first proposal in 1987, the hypothesis has been spurring debates in terms of its validity in the field of bacterial virulence. As a special case of the vector-borne transmission versus virulence tradeoff, where vector is now replaced by environmental longevity, there are only sporadic studies over the last three decades showing that environmental durability is possibly linked with virulence. However, no systematic study of these works is currently available and epidemiological analysis has not been updated for the sit-and-wait hypothesis since the publication of Walther and Ewald’s (2004 review. In this article, we put experimental evidence, epidemiological data and theoretical analysis together to support the sit-and-wait hypothesis. According to the epidemiological data in terms of gain and loss of virulence (+/- and durability (+/- phenotypes, we classify bacteria into four groups, which are: sit-and-wait pathogens (++, vector-borne pathogens (+-, obligate-intracellular bacteria (--, and free-living bacteria (-+. After that, we dive into the abundant bacterial proteomic data with the assistance of bioinformatics techniques in order to investigate the two factors at molecular level thanks to the fast development of high-throughput sequencing technology. Sequences of durability-related genes sourced from Gene Ontology and UniProt databases and virulence factors collected from Virulence Factor Database are used to search 20 corresponding bacterial proteomes in batch mode for homologous sequences via the HMMER software package. Statistical analysis only identified a modest, and not statistically significant correlation between mortality and survival time for eight non-vector-borne bacteria with sit-and-wait potentials. Meanwhile, through between-group comparisons, bacteria with higher

Histone variants and lipid metabolism

NARCIS (Netherlands)

Borghesan, Michela; Mazzoccoli, Gianluigi; Sheedfar, Fareeba; Oben, Jude; Pazienza, Valerio; Vinciguerra, Manlio

2014-01-01

Within nucleosomes, canonical histones package the genome, but they can be opportunely replaced with histone variants. The incorporation of histone variants into the nucleosome is a chief cellular strategy to regulate transcription and cellular metabolism. In pathological terms, cellular steatosis

Virulence gene profiles of avian pathogenic Escherichia coli isolated from chickens with colibacillosis in Bulawayo, Zimbabwe

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Joshua Mbanga

2015-04-01

Full Text Available Colibacillosis, a disease caused by avian pathogenic Escherichia coli (APEC, is one of the main causes of economic losses in the poultry industry worldwide. This study was carried out in order to determine the APEC-associated virulence genes contained by E. coli isolates causing colibacillosis in chickens. A total of 45 E. coli isolates were obtained from the diagnostics and research branch of the Central Veterinary Laboratories, Bulawayo, Zimbabwe. These isolates were obtained from chickens with confirmed cases of colibacillosis after postmortem examination. The presence of the iutA, hlyF, ompT, frz, sitD, fimH, kpsM, sitA, sopB, uvrY, pstB and vat genes were investigated by multiplex polymerase chain reaction (PCR assay. Of the 45 isolates, 93% were positive for the presence of at least one virulence gene. The three most prevalent virulence genes were iutA (80%, fimH (33.3% and hlyF (24.4%. The kpsM, pstB and ompT genes had the lowest prevalence, having been detected in only 2.2% of the isolates. All 12 virulence genes studied were detected in the 45 APEC isolates. Virulence gene profiles were constructed for each APEC isolate from the multiplex data. The APEC isolates were profiled as 62.2% fitting profile A, 31.1% profile B and 6.7% profile C. None of the isolates had more than seven virulence genes. Virulence profiles of Zimbabwean APEC isolates are different from those previously reported. Zimbabwean APEC isolates appear to be less pathogenic and may rely on environmental factors and stress in hosts to establish infection.

Invasive mold infections: virulence and pathogenesis of mucorales.

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Morace, Giulia; Borghi, Elisa

2012-01-01

Mucorales have been increasingly reported as cause of invasive fungal infections in immunocompromised subjects, particularly in patients with haematological malignancies or uncontrolled diabetes mellitus and in those under deferoxamine treatment or undergoing dialysis. The disease often leads to a fatal outcome, but the pathogenesis of the infection is still poorly understood as well as the role of specific virulence determinants and the interaction with the host immune system. Members of the order Mucorales are responsible of almost all cases of invasive mucormycoses, the majority of the etiological agents belonging to the Mucoraceae family. Mucorales are able to produce various proteins and metabolic products toxic to animals and humans, but the pathogenic role of these potential virulence factors is unknown. The availability of free iron in plasma and tissues is believed to be crucial for the pathogenesis of these mycoses. Vascular invasion and neurotropism are considered common pathogenic features of invasive mucormycoses.

Accessory genes confer a high replication rate to virulent feline immunodeficiency virus.

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Troyer, Ryan M; Thompson, Jesse; Elder, John H; VandeWoude, Sue

2013-07-01

Feline immunodeficiency virus (FIV) is a lentivirus that causes AIDS in domestic cats, similar to human immunodeficiency virus (HIV)/AIDS in humans. The FIV accessory protein Vif abrogates the inhibition of infection by cat APOBEC3 restriction factors. FIV also encodes a multifunctional OrfA accessory protein that has characteristics similar to HIV Tat, Vpu, Vpr, and Nef. To examine the role of vif and orfA accessory genes in FIV replication and pathogenicity, we generated chimeras between two FIV molecular clones with divergent disease potentials: a highly pathogenic isolate that replicates rapidly in vitro and is associated with significant immunopathology in vivo, FIV-C36 (referred to here as high-virulence FIV [HV-FIV]), and a less-pathogenic strain, FIV-PPR (referred to here as low-virulence FIV [LV-FIV]). Using PCR-driven overlap extension, we produced viruses in which vif, orfA, or both genes from virulent HV-FIV replaced equivalent genes in LV-FIV. The generation of these chimeras is more straightforward in FIV than in primate lentiviruses, since FIV accessory gene open reading frames have very little overlap with other genes. All three chimeric viruses exhibited increased replication kinetics in vitro compared to the replication kinetics of LV-FIV. Chimeras containing HV-Vif or Vif/OrfA had replication rates equivalent to those of the virulent HV-FIV parental virus. Furthermore, small interfering RNA knockdown of feline APOBEC3 genes resulted in equalization of replication rates between LV-FIV and LV-FIV encoding HV-FIV Vif. These findings demonstrate that Vif-APOBEC interactions play a key role in controlling the replication and pathogenicity of this immunodeficiency-inducing virus in its native host species and that accessory genes act as mediators of lentiviral strain-specific virulence.

Functional dissection of Streptococcus pyogenes M5 protein: the hypervariable region is essential for virulence.

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Johan Waldemarsson

Full Text Available The surface-localized M protein of Streptococcus pyogenes is a major virulence factor that inhibits phagocytosis, as determined ex vivo. Because little is known about the role of M protein in vivo we analyzed the contribution of different M protein regions to virulence, using the fibrinogen (Fg-binding M5 protein and a mouse model of acute invasive infection. This model was suitable, because M5 is required for mouse virulence and binds mouse and human Fg equally well, as shown here. Mixed infection experiments with wild type bacteria demonstrated that mutants lacking the N-terminal hypervariable region (HVR or the Fg-binding B-repeat region were strongly attenuated, while a mutant lacking the conserved C-repeats was only slightly attenuated. Because the HVR of M5 is not required for phagocytosis resistance, our data imply that this HVR plays a major but unknown role during acute infection. The B-repeat region is required for phagocytosis resistance and specifically binds Fg, suggesting that it promotes virulence by binding Fg. However, B-repeat mutants were attenuated even in Fg-deficient mice, implying that the B-repeats may have a second function, in addition to Fg-binding. These data demonstrate that two distinct M5 regions, including the HVR, are essential to virulence during the early stages of an infection. In particular, our data provide the first in vivo evidence that the HVR of an M protein plays a major role in virulence, focusing interest on the molecular role of this region.

The significance of virulence factors in Helicobacter pylori.

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Shiota, Seiji; Suzuki, Rumiko; Yamaoka, Yoshio

2013-07-01

Helicobacter pylori (H. pylori) infection is linked to various gastroduodenal diseases; however, only a small fraction of these patients develop associated diseases. Despite the high prevalence of H. pylori infection in Africa and South Asia, the incidence of gastric cancer in these areas is much lower than those in other countries. The incidence of gastric cancer tends to decrease from north to south in East Asia. Such geographical differences in the pathology can be explained, at least in part, by the presence of different types of H. pylori virulence factors in addition to host and environmental factors. Virulence factors of H. pylori, such as CagA, VacA, DupA, IceA, OipA and BabA, have been demonstrated to be the predictors of severe clinical outcomes. Interestingly, a meta-analysis showed that CagA seropositivity was associated with gastric cancer compared with gastritis, even in East Asian countries where almost the strains possess cagA. Another meta-analysis also confirmed the significance of vacA, dupA and iceA. However, it is possible that additional important pathogenic genes may exist because H. pylori consists of approximately 1600 genes. Despite the advances in our understanding of the development of H. pylori infection-related diseases, further work is required to clarify the roles of H. pylori virulence factors. © 2013 The Authors. Journal of Digestive Diseases © 2013 Wiley Publishing Asia Pty Ltd and Chinese Medical Association Shanghai Branch, Chinese Society of Gastroenterology, Renji Hospital Affiliated to Shanghai Jiaotong University School of Medicine.

Novel cyclic di-GMP effectors of the YajQ protein family control bacterial virulence.

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Shi-qi An

2014-10-01

Full Text Available Bis-(3',5' cyclic di-guanylate (cyclic di-GMP is a key bacterial second messenger that is implicated in the regulation of many critical processes that include motility, biofilm formation and virulence. Cyclic di-GMP influences diverse functions through interaction with a range of effectors. Our knowledge of these effectors and their different regulatory actions is far from complete, however. Here we have used an affinity pull-down assay using cyclic di-GMP-coupled magnetic beads to identify cyclic di-GMP binding proteins in the plant pathogen Xanthomonas campestris pv. campestris (Xcc. This analysis identified XC_3703, a protein of the YajQ family, as a potential cyclic di-GMP receptor. Isothermal titration calorimetry showed that the purified XC_3703 protein bound cyclic di-GMP with a high affinity (K(d∼2 µM. Mutation of XC_3703 led to reduced virulence of Xcc to plants and alteration in biofilm formation. Yeast two-hybrid and far-western analyses showed that XC_3703 was able to interact with XC_2801, a transcription factor of the LysR family. Mutation of XC_2801 and XC_3703 had partially overlapping effects on the transcriptome of Xcc, and both affected virulence. Electromobility shift assays showed that XC_3703 positively affected the binding of XC_2801 to the promoters of target virulence genes, an effect that was reversed by cyclic di-GMP. Genetic and functional analysis of YajQ family members from the human pathogens Pseudomonas aeruginosa and Stenotrophomonas maltophilia showed that they also specifically bound cyclic di-GMP and contributed to virulence in model systems. The findings thus identify a new class of cyclic di-GMP effector that regulates bacterial virulence.

CLEVER: Clique-Enumerating Variant Finder