Immunopathology of highly virulent pathogens: insights from Ebola virus.

PubMed

Zampieri, Carisa A; Sullivan, Nancy J; Nabel, Gary J

2007-11-01

Ebola virus is a highly virulent pathogen capable of inducing a frequently lethal hemorrhagic fever syndrome. Accumulating evidence indicates that the virus actively subverts both innate and adaptive immune responses and triggers harmful inflammatory responses as it inflicts direct tissue damage. The host immune system is ultimately overwhelmed by a combination of inflammatory factors and virus-induced cell damage, particularly in the liver and vasculature, often leading to death from septic shock. We summarize the mechanisms of immune dysregulation and virus-mediated cell damage in Ebola virus-infected patients. Future approaches to prevention and treatment of infection will be guided by answers to unresolved questions about interspecies transmission, molecular mechanisms of pathogenesis, and protective adaptive and innate immune responses to Ebola virus.

Role of Uropathogenic Escherichia coli Virulence Factors in Development of Urinary Tract Infection and Kidney Damage

PubMed Central

Bien, Justyna; Sokolova, Olga; Bozko, Przemyslaw

2012-01-01

Uropathogenic Escherichia coli (UPEC) is a causative agent in the vast majority of urinary tract infections (UTIs), including cystitis and pyelonephritis, and infectious complications, which may result in acute renal failure in healthy individuals as well as in renal transplant patients. UPEC expresses a multitude of virulence factors to break the inertia of the mucosal barrier. In response to the breach by UPEC into the normally sterile urinary tract, host inflammatory responses are triggered leading to cytokine production, neutrophil influx, and the exfoliation of infected bladder epithelial cells. Several signaling pathways activated during UPEC infection, including the pathways known to activate the innate immune response, interact with calcium-dependent signaling pathways. Some UPEC isolates, however, might possess strategies to delay or suppress the activation of components of the innate host response in the urinary tract. Studies published in the recent past provide new information regarding how virulence factors of uropathogenic E. coli are involved in activation of the innate host response. Despite numerous host defense mechanisms, UPEC can persist within the urinary tract and may serve as a reservoir for recurrent infections and serious complications. Presentation of the molecular details of these events is essential for development of successful strategies for prevention of human UTIs and urological complications associated with UTIs. PMID:22506110

The FonSIX6 gene acts as an avirulence effector in the Fusarium oxysporum f. sp. niveum - watermelon pathosystem.

PubMed

Niu, Xiaowei; Zhao, Xiaoqiang; Ling, Kai-Shu; Levi, Amnon; Sun, Yuyan; Fan, Min

2016-06-20

When infecting a host plant, the fungus Fusarium oxysporum secretes several effector proteins into the xylem tissue to promote virulence. However, in a host plant with an innate immune system involving analogous resistance proteins, the fungus effector proteins may trigger resistance, rather than promoting virulence. Identity of the effector genes of Fusarium oxysporum f. sp. niveum (Fon) races that affect watermelon (Citrullus lanatus) are currently unknown. In this study, the SIX6 (secreted in xylem protein 6) gene was identified in Fon races 0 and 1 but not in the more virulent Fon race 2. Disrupting the FonSIX6 gene in Fon race 1 did not affect the sporulation or growth rate of the fungus but significantly enhanced Fon virulence in watermelon, suggesting that the mutant ΔFon1SIX6 protein allowed evasion of R protein-mediated host resistance. Complementation of the wild-type race 2 (which lacks FonSIX6) with FonSIX6 reduced its virulence. These results provide evidence supporting the hypothesis that FonSIX6 is an avirulence gene. The identification of FonSix6 as an avirulence factor may be a first step in understanding the mechanisms of Fon virulence and resistance in watermelon and further elucidating the role of Six6 in Fusarium-plant interactions.

Pseudomonas aeruginosa type IV minor pilins and PilY1 regulate virulence by modulating FimS-AlgR activity.

PubMed

Marko, Victoria A; Kilmury, Sara L N; MacNeil, Lesley T; Burrows, Lori L

2018-05-18

Type IV pili are expressed by a wide range of prokaryotes, including the opportunistic pathogen Pseudomonas aeruginosa. These flexible fibres mediate twitching motility, biofilm maturation, surface adhesion, and virulence. The pilus is composed mainly of major pilin subunits while the low abundance minor pilins FimU-PilVWXE and the putative adhesin PilY1 prime pilus assembly and are proposed to form the pilus tip. The minor pilins and PilY1 are encoded in an operon that is positively regulated by the FimS-AlgR two-component system. Independent of pilus assembly, PilY1 was proposed to be a mechanosensory component that-in conjunction with minor pilins-triggers up-regulation of acute virulence phenotypes upon surface attachment. Here, we investigated the link between the minor pilins/PilY1 and virulence. pilW, pilX, and pilY1 mutants had reduced virulence towards Caenorhabditis elegans relative to wild type or a major pilin mutant, implying a role in pathogenicity that is independent of pilus assembly. We hypothesized that loss of specific minor pilins relieves feedback inhibition on FimS-AlgR, increasing transcription of the AlgR regulon and delaying C. elegans killing. Reporter assays confirmed that FimS-AlgR were required for increased expression of the minor pilin operon upon loss of select minor pilins. Overexpression of AlgR or its hyperactivation via a phosphomimetic mutation reduced virulence, and the virulence defects of pilW, pilX, and pilY1 mutants required FimS-AlgR expression and activation. We propose that PilY1 and the minor pilins inhibit their own expression, and that loss of these proteins leads to FimS-mediated activation of AlgR that suppresses expression of acute-phase virulence factors and delays killing. This mechanism could contribute to adaptation of P. aeruginosa in chronic lung infections, as mutations in the minor pilin operon result in the loss of piliation and increased expression of AlgR-dependent virulence factors-such as alginate-that are characteristic of such infections.

Population structure of rumen Escherichia coli associated with subacute ruminal acidosis (SARA) in dairy cattle.

PubMed

Khafipour, E; Plaizier, J C; Aikman, P C; Krause, D O

2011-01-01

Previous studies indicated that only subacute ruminal acidosis (SARA), induced by feeding a high-grain diet, is associated with an inflammatory response and increased abundance of Escherichia coli in the rumen. We hypothesized that ruminal E. coli in grain pellet-induced SARA carried virulence factors that potentially contribute to the immune activation during SARA. One hundred twenty-nine E. coli isolates were cultured from the rumens of 8 cows (4 animals per treatment) in which SARA had been nutritionally induced by feeding a high-grain diet (GPI-SARA) or a diet containing alfalfa pellets (API-SARA). The population structure of the E. coli was evaluated with the ABD genotyping system and repetitive sequence-based (rep)-PCR fingerprinting. Twenty-five virulence factors were evaluated with PCR. Escherichia coli numbers were higher in the GPI-SARA treatment than in the API-SARA treatment. The genetic structure of the E. coli was significantly different between SARA challenge models. Isolates from GPI-control (46%), API-control (70%), and API-SARA (53%) were closely related and fell into one cluster, whereas isolates from GPI-SARA (54%) grouped separately. The ABD typing indicated a shift from an A-type E. coli population to a B1-type population only due to GPI-SARA. Of the 25 virulence factors tested, curli fiber genes were highly associated with GPI. Curli fibers were first identified in E. coli mastitis isolates and are potent virulence factors that induce a range of immune responses. Results suggest that under low rumen pH conditions induced by a grain diet, there is a burst in the number of E. coli with virulence genes that can take advantage of these rumen conditions to trigger an inflammatory response. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Significance of hyphae formation in virulence of Candida tropicalis and transcriptomic analysis of hyphal cells.

PubMed

Jiang, Cen; Li, Zhen; Zhang, Lihua; Tian, Yuan; Dong, Danfeng; Peng, Yibing

2016-11-01

Recently, the proportion of Candida tropicalis in clinical isolates has significantly increased. Some C. tropicalis strains colonize the skin or mucosal surfaces as commensals; others trigger invasive infection. To date, the pathogenicity of C. tropicalis has not been thoroughly researched. This study reports several virulence factors, including biofilm and hyphae formation, proteinase, phospholipase, lipase and hemolytic activity, in 52 clinical isolates of C. tropicalis collected from five hospitals in four provinces of China. Some C. tropicalis tended to produce more hyphae than others in the same circumstance. Six C. tropicalis strains with different morphologies were injected into mice via the tail vein, and the survival proportions and fungal burdens of the strains were evaluated. Hyphal production by C. tropicalis was associated with stronger virulence. RNA sequencing revealed that C. tropicalis with more hyphae up-regulated several genes involved in morphological differentiation and oxidative response, including IF2, Atx1, and Sod2. It appears that hyphal formation plays a vital role in the pathogenicity of C. tropicalis, and interacts with the oxidative stress response to strengthen the organism's virulence. Copyright © 2016 Elsevier GmbH. All rights reserved.

Pathogenesis of African swine fever in domestic pigs and European wild boar.

PubMed

Blome, Sandra; Gabriel, Claudia; Beer, Martin

2013-04-01

African swine fever (ASF) is among the most important viral diseases that can affect domestic and feral pigs. Both clinical signs and pathomorphological changes vary considerably depending on strain virulence and host factors. Acute infections with highly virulent virus strains lead to a clinical course that resembles a viral haemorrhagic fever that is characterized by pronounced depletion of lymphoid tissues, apoptosis of lymphocyte subsets, and impairment of haemostasis and immune functions. It is generally accepted that most lesions can be attributed to cytokine-mediated interactions triggered by infected and activated monocytes and macrophages, rather than by virus-induced direct cell damage. Nevertheless, most pathogenetic mechanisms are far from being understood. This review summarizes the current knowledge and discusses implications and research gaps. Copyright © 2012 Elsevier B.V. All rights reserved.

Plant-Pathogen Warfare under Changing Climate Conditions.

PubMed

Velásquez, André C; Castroverde, Christian Danve M; He, Sheng Yang

2018-05-21

Global environmental changes caused by natural and human activities have accelerated in the past 200 years. The increase in greenhouse gases is predicted to continue to raise global temperature and change water availability in the 21 st century. In this Review, we explore the profound effect the environment has on plant diseases - a susceptible host will not be infected by a virulent pathogen if the environmental conditions are not conducive for disease. The change in CO 2 concentrations, temperature, and water availability can have positive, neutral, or negative effects on disease development, as each disease may respond differently to these variations. However, the concept of disease optima could potentially apply to all pathosystems. Plant resistance pathways, including pattern-triggered immunity to effector-triggered immunity, RNA interference, and defense hormone networks, are all affected by environmental factors. On the pathogen side, virulence mechanisms, such as the production of toxins and virulence proteins, as well as pathogen reproduction and survival are influenced by temperature and humidity. For practical reasons, most laboratory investigations into plant-pathogen interactions at the molecular level focus on well-established pathosystems and use a few static environmental conditions that capture only a fraction of the dynamic plant-pathogen-environment interactions that occur in nature. There is great need for future research to increasingly use dynamic environmental conditions in order to fully understand the multidimensional nature of plant-pathogen interactions and produce disease-resistant crop plants that are resilient to climate change. Copyright © 2018 Elsevier Ltd. All rights reserved.

Immune Receptors and Co-receptors in Antiviral Innate Immunity in Plants.

PubMed

Gouveia, Bianca C; Calil, Iara P; Machado, João Paulo B; Santos, Anésia A; Fontes, Elizabeth P B

2016-01-01

Plants respond to pathogens using an innate immune system that is broadly divided into PTI (pathogen-associated molecular pattern- or PAMP-triggered immunity) and ETI (effector-triggered immunity). PTI is activated upon perception of PAMPs, conserved motifs derived from pathogens, by surface membrane-anchored pattern recognition receptors (PRRs). To overcome this first line of defense, pathogens release into plant cells effectors that inhibit PTI and activate effector-triggered susceptibility (ETS). Counteracting this virulence strategy, plant cells synthesize intracellular resistance (R) proteins, which specifically recognize pathogen effectors or avirulence (Avr) factors and activate ETI. These coevolving pathogen virulence strategies and plant resistance mechanisms illustrate evolutionary arms race between pathogen and host, which is integrated into the zigzag model of plant innate immunity. Although antiviral immune concepts have been initially excluded from the zigzag model, recent studies have provided several lines of evidence substantiating the notion that plants deploy the innate immune system to fight viruses in a manner similar to that used for non-viral pathogens. First, most R proteins against viruses so far characterized share structural similarity with antibacterial and antifungal R gene products and elicit typical ETI-based immune responses. Second, virus-derived PAMPs may activate PTI-like responses through immune co-receptors of plant PTI. Finally, and even more compelling, a viral Avr factor that triggers ETI in resistant genotypes has recently been shown to act as a suppressor of PTI, integrating plant viruses into the co-evolutionary model of host-pathogen interactions, the zigzag model. In this review, we summarize these important progresses, focusing on the potential significance of antiviral immune receptors and co-receptors in plant antiviral innate immunity. In light of the innate immune system, we also discuss a newly uncovered layer of antiviral defense that is specific to plant DNA viruses and relies on transmembrane receptor-mediated translational suppression for defense.

Effector-triggered immunity: from pathogen perception to robust defense.

PubMed

Cui, Haitao; Tsuda, Kenichi; Parker, Jane E

2015-01-01

In plant innate immunity, individual cells have the capacity to sense and respond to pathogen attack. Intracellular recognition mechanisms have evolved to intercept perturbations by pathogen virulence factors (effectors) early in host infection and convert it to rapid defense. One key to resistance success is a polymorphic family of intracellular nucleotide-binding/leucine-rich-repeat (NLR) receptors that detect effector interference in different parts of the cell. Effector-activated NLRs connect, in various ways, to a conserved basal resistance network in order to transcriptionally boost defense programs. Effector-triggered immunity displays remarkable robustness against pathogen disturbance, in part by employing compensatory mechanisms within the defense network. Also, the mobility of some NLRs and coordination of resistance pathways across cell compartments provides flexibility to fine-tune immune outputs. Furthermore, a number of NLRs function close to the nuclear chromatin by balancing actions of defense-repressing and defense-activating transcription factors to program cells dynamically for effective disease resistance.

Protective and destructive immunity in the periodontium: Part 1--innate and humoral immunity and the periodontium.

PubMed

Teng, Y-T A

2006-03-01

Based on the results of recent research in the field, the present paper will discuss the protective and destructive aspects of the innate vs. adaptive (humoral and cell-mediated) immunity associated with the bacterial virulent factors or antigenic determinants during periodontal pathogenesis. Attention will be focused on: (i) the Toll-like receptors (TLR), the innate immune repertoire for recognizing the unique molecular patterns of microbial components that trigger innate and adaptive immunity for effective host defenses, in some general non-oral vs. periodontal microbial infections; (ii) T-cell-mediated immunity, Th-cytokines, and osteoclastogenesis in periodontal disease progression; and (iii) some molecular techniques developed and used to identify critical microbial virulence factors or antigens associated with host immunity (using Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis as the model species). Therefore, further understanding of the molecular interactions and mechanisms associated with the host's innate and adaptive immune responses will facilitate the development of new and innovative therapeutics for future periodontal treatments.

A pivotal role for the Streptococcus iniae extracellular polysaccharide in triggering proinflammatory cytokines transcription and inducing death in rainbow trout.

PubMed

Eyngor, Marina; Lublin, Avishay; Shapira, Roni; Hurvitz, Avshalom; Zlotkin, Amir; Tekoah, Yoram; Eldar, Avi

2010-04-01

Streptococcus iniae is a major pathogen of fish, causing considerable economic losses in Israel, the United States and the Far East. Containment of mortalities through vaccination was recently compromised due to the emergence of novel vaccine-escape strains that are distinguished from previous strains by their ability to produce large amounts of extracellular polysaccharide (EPS) that is released to the medium. In vitro and in vivo data now indicate that the EPS is a major virulence factor, capable of triggering the proinflammatory cytokine machinery and inducing mortality of fish. Streptococcus iniae EPS might therefore be considered to be responsible for sepsis and death just as lipopolysaccharide is for Gram-negative pathogens.

Plant immunity triggered by microbial molecular signatures.

PubMed

Zhang, Jie; Zhou, Jian-Min

2010-09-01

Pathogen/microbe-associated molecular patterns (PAMPs/MAMPs) are recognized by host cell surface-localized pattern-recognition receptors (PRRs) to activate plant immunity. PAMP-triggered immunity (PTI) constitutes the first layer of plant immunity that restricts pathogen proliferation. PTI signaling components often are targeted by various Pseudomonas syringae virulence effector proteins, resulting in diminished plant defenses and increased bacterial virulence. Some of the proteins targeted by pathogen effectors have evolved to sense the effector activity by associating with cytoplasmic immune receptors classically known as resistance proteins. This allows plants to activate a second layer of immunity termed effector-triggered immunity (ETI). Recent studies on PTI regulation and P. syringae effector targets have uncovered new components in PTI signaling. Although MAP kinase (MAPK) cascades have been considered crucial for PTI, emerging evidence indicates that a MAPK-independent pathway also plays an important role in PTI signaling.

The pH of activation of the hemagglutinin protein regulates H5N1 influenza virus replication and pathogenesis in mice.

PubMed

Zaraket, Hassan; Bridges, Olga A; Russell, Charles J

2013-05-01

After receptor binding and internalization during influenza virus entry, the hemagglutinin (HA) protein is triggered by low pH to undergo irreversible conformational changes that mediate membrane fusion. To investigate how mutations that alter the activation pH of the HA protein influence the fitness of an avian H5N1 influenza virus in a mammalian model, we infected C57BL/6J or DBA/2J mice and compared the replication and virulence of recombinant A/chicken/Vietnam/C58/04 (H5N1) HA-Y231H mutant, wild-type, and HA-H241Q and HA-K582I mutant viruses that have HA activation pH values of 6.3, 5.9, 5.6, and 5.4, respectively. The HA-Y231H mutant virus was highly susceptible to acid inactivation in vitro and was attenuated for growth and virulence in mice, suggesting that an H5N1 HA protein triggered at pH 6.3 is too unstable for the virus to remain fit. Wild-type and HA-H241Q viruses were similar in pathogenicity and grew to similar levels in mice, ducks, and cell cultures derived from both avian and mammalian tissues, suggesting that H5N1 HA proteins triggered at pH values in the range of 5.9 to 5.6 broadly support replication. The HA-K582I mutant virus had greater growth and virulence in DBA/2J mice than the wild type did, although the mutant virus was highly attenuated in ducks. The data suggest that adaptation of avian H5N1 influenza virus for infection in mammals is supported by a decrease in the HA activation pH to 5.4. Identification of the HA activation pH as a host-specific infectivity factor is expected to aid in the surveillance and risk assessment of currently circulating H5N1 influenza viruses.

A two-domain protein triggers heat shock pathway and necrosis pathway both in model plant and nematode.

PubMed

Ruan, Lifang; Wang, Huihui; Cai, Ge; Peng, Donghai; Zhou, Hua; Zheng, Jinshui; Zhu, Lei; Wang, Xixi; Yu, Haoquan; Li, Seng; Geng, Ce; Sun, Ming

2015-11-01

The entomopathogen Bacillus thuringiensis is equipped with multiple virulent factors. The genome sequence of B. thuringiensis YBT1520 revealed the presence of a two-domain protein named Nel which is composed of a necrosis-inducing phytophthora protein 1-like domain found in phytopathogens and a ricin B-like lectin domain. The merging of two distantly related domains is relatively rare. Nel induced necrosis and pathogen-triggered immunity (PTI) on model plants. The Nel also exhibited inhibition activity to nematode. Microscopic observation showed that the toxicity of Nel to nematodes targets the intestine. Quantitative proteomics revealed that Nel stimulated the host defence. The Nel thus possesses dual roles, as both toxin and elicitor. Remarkably, the Nel protein triggered a similar response, induction of the heat shock pathway and the necrosis pathway, in both model plants and nematodes. The unusual ability of Nel to function across kingdom suggests a highly conserved mechanism in eukaryotes that predates the divergence of plants and animal. It is also speculated that the two-domain protein is the result of horizontal gene transfer (HGT) between phytopathogens and entomopathogens. Our results provide an example that HGT occurs between members of different species or even genera with lower frequency are particularly important for evolution of new bacterial pathogen lineages with new virulence. Bacillus thuringiensis occupies the same ecological niches, plant and soil, as phytopathogens, providing the opportunity for gene exchange. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Induction of group A Streptococcus virulence by a human antimicrobial peptide.

PubMed

Gryllos, Ioannis; Tran-Winkler, Hien J; Cheng, Ming-Fang; Chung, Hachung; Bolcome, Robert; Lu, Wuyuan; Lehrer, Robert I; Wessels, Michael R

2008-10-28

Group A streptococci (Streptococcus pyogenes or GAS) freshly isolated from individuals with streptococcal sore throat or invasive ("flesh-eating") infection often grow as mucoid colonies on primary culture but lose this colony appearance after laboratory passage. The mucoid phenotype is due to abundant production of the hyaluronic acid capsular polysaccharide, a key virulence determinant associated with severe GAS infections. These observations suggest that signal(s) from the human host trigger increased production of capsule and perhaps other virulence factors during infection. Here we show that subinhibitory concentrations of the human antimicrobial cathelicidin peptide LL-37 stimulate expression of the GAS capsule synthesis operon (hasABC). Up-regulation is mediated by the CsrRS 2-component regulatory system: it requires a functional CsrS sensor protein and can be antagonized by increased extracellular Mg(2+), the other identified environmental signal for CsrS. Up-regulation was also evident for other CsrRS-regulated virulence genes, including the IL-8 protease PrtS/ScpC and the integrin-like/IgG protease Mac/IdeS, findings that suggest a coordinated GAS virulence response elicited by this antimicrobial immune effector peptide. LL-37 signaling through CsrRS led to a marked increase in GAS resistance to opsonophagocytic killing by human leukocytes, an in vitro measure of enhanced GAS virulence, consistent with increased expression of the antiphagocytic capsular polysaccharide and Mac/IdeS. We propose that the human cathelicidin LL-37 has the paradoxical effect of stimulating CsrRS-regulated virulence gene expression, thereby enhancing GAS pathogenicity during infection. The ability of GAS to sense and respond to LL-37 may explain, at least in part, the unique susceptibility of the human species to streptococcal infection.

The protein family TcTASV-C is a novel Trypanosoma cruzi virulence factor secreted in extracellular vesicles by trypomastigotes and highly expressed in bloodstream forms.

PubMed

Caeiro, Lucas D; Alba-Soto, Catalina D; Rizzi, Mariana; Solana, María Elisa; Rodriguez, Giselle; Chidichimo, Agustina M; Rodriguez, Matías E; Sánchez, Daniel O; Levy, Gabriela V; Tekiel, Valeria

2018-05-01

TcTASV-C is a protein family of about 15 members that is expressed only in the trypomastigote stage of Trypanosoma cruzi. We have previously shown that TcTASV-C is located at the parasite surface and secreted to the medium. Here we report that the expression of different TcTASV-C genes occurs simultaneously at the trypomastigote stage and while some secreted and parasite-associated products are found in both fractions, others are different. Secreted TcTASV-C are mainly shedded through trypomastigote extracellular vesicles, of which they are an abundant constituent, despite its scarce expression on culture-derived trypomastigotes. In contrast, TcTASV-C is highly expressed in bloodstream trypomastigotes; its upregulation in bloodstream parasites was observed in different T. cruzi strains and was specific for TcTASV-C, suggesting that some host-molecules trigger TcTASV-C expression. TcTASV-C is also strongly secreted by bloodstream parasites. A DNA prime-protein boost immunization scheme with TcTASV-C was only partially effective to control the infection in mice challenged with a highly virulent T. cruzi strain. Vaccination triggered a strong humoral response that delayed the appearance of bloodstream trypomastigotes at the early phase of the infection. Linear epitopes recognized by vaccinated mice were mapped within the TcTASV-C family motif, suggesting that blockade of secreted TcTASV-C impacts on the settlement of infection. Furthermore, although experimental and naturally T. cruzi-infected hosts did not react with antigens from extracellular vesicles, vaccinated and challenged mice recognized not only TcTASV-C but also other vesicle-antigens. We hypothesize that TcTASV-C is involved in the establishment of the initial T. cruzi infection in the mammalian host. Altogether, these results point towards TcTASV-C as a novel secreted virulence factor of T. cruzi trypomastigotes.

Effect of the Streptococcus agalactiae Virulence Regulator CovR on the Pathogenesis of Urinary Tract Infection.

PubMed

Sullivan, Matthew J; Leclercq, Sophie Y; Ipe, Deepak S; Carey, Alison J; Smith, Joshua P; Voller, Nathan; Cripps, Allan W; Ulett, Glen C

2017-02-01

Streptococcus agalactiae can cause urinary tract infection (UTI). The role of the S. agalactiae global virulence regulator, CovR, in UTI pathogenesis is unknown. We used murine and human bladder uroepithelial cell models of UTI and S. agalactiae mutants in covR and related factors, including β-hemolysin/cytolysin (β-h/c), surface-anchored adhesin HvgA, and capsule to study the role of CovR in UTI. We found that covR-deficient serotype III S. agalactiae 874391 was significantly attenuated for colonization in mice and adhesion to uroepithelial cells. Mice infected with covR-deficient S. agalactiae produced less proinflammatory cytokines than those infected with wild-type 874391. Acute cytotoxicity in uroepithelial cells triggered by covR-deficient but not wild-type 874391 was associated with significant caspase 3 activation. Mechanistically, covR mutation significantly altered the expression of several genes in S. agalactiae 874391 that encode key virulence factors, including β-h/c and HvgA, but not capsule. Subsequent mutational analyses revealed that HvgA and capsule, but not the β-h/c, exerted significant effects on colonization of the murine urinary tract in vivo. S. agalactiae CovR promotes bladder infection and inflammation, as well as adhesion to and viability of uroepithelial cells. The pathogenesis of S. agalactiae UTI is complex, multifactorial, and influenced by virulence effects of CovR, HvgA, and capsule. © The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.

Clinical and Pathophysiological Overview of Acinetobacter Infections: a Century of Challenges

PubMed Central

Nielsen, Travis B.; Bonomo, Robert A.; Pantapalangkoor, Paul; Luna, Brian; Spellberg, Brad

2016-01-01

SUMMARY Acinetobacter is a complex genus, and historically, there has been confusion about the existence of multiple species. The species commonly cause nosocomial infections, predominantly aspiration pneumonia and catheter-associated bacteremia, but can also cause soft tissue and urinary tract infections. Community-acquired infections by Acinetobacter spp. are increasingly reported. Transmission of Acinetobacter and subsequent disease is facilitated by the organism's environmental tenacity, resistance to desiccation, and evasion of host immunity. The virulence properties demonstrated by Acinetobacter spp. primarily stem from evasion of rapid clearance by the innate immune system, effectively enabling high bacterial density that triggers lipopolysaccharide (LPS)–Toll-like receptor 4 (TLR4)-mediated sepsis. Capsular polysaccharide is a critical virulence factor that enables immune evasion, while LPS triggers septic shock. However, the primary driver of clinical outcome is antibiotic resistance. Administration of initially effective therapy is key to improving survival, reducing 30-day mortality threefold. Regrettably, due to the high frequency of this organism having an extreme drug resistance (XDR) phenotype, early initiation of effective therapy is a major clinical challenge. Given its high rate of antibiotic resistance and abysmal outcomes (up to 70% mortality rate from infections caused by XDR strains in some case series), new preventative and therapeutic options for Acinetobacter spp. are desperately needed. PMID:27974412

Distinct regions of the Phytophthora essential effector Avh238 determine its function in cell death activation and plant immunity suppression.

PubMed

Yang, Bo; Wang, Qunqing; Jing, Maofeng; Guo, Baodian; Wu, Jiawei; Wang, Haonan; Wang, Yang; Lin, Long; Wang, Yan; Ye, Wenwu; Dong, Suomeng; Wang, Yuanchao

2017-04-01

Phytophthora pathogens secrete effectors to manipulate host innate immunity, thus facilitating infection. Among the RXLR effectors highly induced during Phytophthora sojae infection, Avh238 not only contributes to pathogen virulence but also triggers plant cell death. However, the detailed molecular basis of Avh238 functions remains largely unknown. We mapped the regions responsible for Avh238 functions in pathogen virulence and plant cell death induction using a strategy that combines investigation of natural variation and large-scale mutagenesis assays. The correlation between cellular localization and Avh238 functions was also evaluated. We found that the 79 th residue (histidine or leucine) of Avh238 determined its cell death-inducing activity, and that the 53 amino acids in its C-terminal region are responsible for promoting Phytophthora infection. Transient expression of Avh238 in Nicotiana benthamiana revealed that nuclear localization is essential for triggering cell death, while Avh238-mediated suppression of INF1-triggered cell death requires cytoplasmic localization. Our results demonstrate that a representative example of an essential Phytophthora RXLR effector can evolve to escape recognition by the host by mutating one nucleotide site, and can also retain plant immunosuppressive activity to enhance pathogen virulence in planta. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

The well-coordinated linkage between acidogenicity and aciduricity via insoluble glucans on the surface of Streptococcus mutans

PubMed Central

Guo, Lihong; McLean, Jeffrey S.; Lux, Renate; He, Xuesong; Shi, Wenyuan

2015-01-01

Streptococcus mutans is considered the principal cariogenic bacterium for dental caries. Despite the recognition of their importance for cariogenesis, the possible coordination among S. mutans’ main virulence factors, including glucan production, acidogenicity and aciduricity, has been less well studied. In the present study, using S. mutans strains with surface-displayed pH-sensitive pHluorin, we revealed sucrose availability- and Gtf functionality-dependent proton accumulation on S. mutans surface. Consistent with this, using a pH-sensitive dye, we demonstrated that both in vivo cell-produced and in vitro enzymatically synthesized insoluble glucans displayed proton-concentrating ability. Global transcriptomics revealed proton accumulation triggers the up-regulation of genes encoding functions involved in acid tolerance response in a glucan-dependent manner. Our data suggested that this proton enrichment around S. mutans could pre-condition the bacterium for acid-stress. Consistent with this hypothesis, we found S. mutans strains defective in glucan production were more acid sensitive. Our study revealed for the first time that insoluble glucans is likely an essential factor linking acidogenicity with aciduricity. The coordination of these key virulence factors could provide new insights on how S. mutans may have become a major cariogenic pathogen. PMID:26657939

Drosophila larvae food intake cessation following exposure to Erwinia contaminated media requires odor perception, Trpa1 channel and evf virulence factor.

PubMed

Keita, Seydou; Masuzzo, Ambra; Royet, Julien; Kurz, C Leopold

2017-05-01

When exposed to microorganisms, animals use several protective strategies. On one hand, as elegantly exemplified in Drosophila melanogaster, the innate immune system recognizes microbial compounds and triggers an antimicrobial response. On the other hand, behaviors preventing an extensive contact with the microbes and thus reducing the risk of infection have been described. However, these reactions ranging from microbes aversion to intestinal transit increase or food intake decrease have been rarely defined at the molecular level. In this study, we set up an experimental system that allowed us to rapidly identify and quantify food intake decreases in Drosophila larvae exposed to media contaminated with bacteria. Specifically, we report a robust dose-dependent food intake decrease following exposure to the bacteria Erwinia carotovora carotovora strain Ecc15. We demonstrate that this response does not require Imd innate immune pathway, but rather the olfactory neuronal circuitry, the Trpa1 receptor and the evf virulence factor. Finally, we show that Ecc15 induce the same behavior in the invasive pest insect Drosophila suzukii. Copyright © 2017 Elsevier Ltd. All rights reserved.

Yersinia virulence factors - a sophisticated arsenal for combating host defences

PubMed Central

Atkinson, Steve; Williams, Paul

2016-01-01

The human pathogens Yersinia pseudotuberculosis and Yersinia enterocolitica cause enterocolitis, while Yersinia pestis is responsible for pneumonic, bubonic, and septicaemic plague. All three share an infection strategy that relies on a virulence factor arsenal to enable them to enter, adhere to, and colonise the host while evading host defences to avoid untimely clearance. Their arsenal includes a number of adhesins that allow the invading pathogens to establish a foothold in the host and to adhere to specific tissues later during infection. When the host innate immune system has been activated, all three pathogens produce a structure analogous to a hypodermic needle. In conjunction with the translocon, which forms a pore in the host membrane, the channel that is formed enables the transfer of six ‘effector’ proteins into the host cell cytoplasm. These proteins mimic host cell proteins but are more efficient than their native counterparts at modifying the host cell cytoskeleton, triggering the host cell suicide response. Such a sophisticated arsenal ensures that yersiniae maintain the upper hand despite the best efforts of the host to counteract the infecting pathogen. PMID:27347390

Chronic gastritis - an update.

PubMed

Varbanova, Mariya; Frauenschläger, Katrin; Malfertheiner, Peter

2014-12-01

Helicobacter pylori is the main aetiologic factor for chronic gastritis worldwide. The degree of inflammation and the evolution of this form of chronic gastritis can vary largely depending on bacterial virulence factors, host susceptibility factors and environmental conditions. Autoimmune gastritis is another cause of chronic inflammation in the stomach, which can occur in all age groups. This disease presents typically with vitamin B12 deficiency and pernicious anaemia. The presence of anti-parietal cell antibodies is highly specific for the diagnosis. The role of H. pylori as a trigger for autoimmune gastritis remains uncertain. Other rare conditions for chronic gastritis are chronic inflammatory conditions such as Crohn's disease or on the background of lymphocytic or collagenous gastroenteropathies. Copyright © 2014. Published by Elsevier Ltd.

How Listeria monocytogenes organizes its surface for virulence

PubMed Central

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

Virulence, immunopathology and transmissibility of selected strains of Mycobacterium tuberculosis in a murine model

PubMed Central

Marquina-Castillo, Brenda; García-García, Lourdes; Ponce-de-León, Alfredo; Jimenez-Corona, Maria-Eugenia; Bobadilla-del Valle, Miriam; Cano-Arellano, Bulmaro; Canizales-Quintero, Sergio; Martinez-Gamboa, Areli; Kato-Maeda, Midori; Robertson, Brian; Young, Douglas; Small, Peter; Schoolnik, Gary; Sifuentes-Osornio, Jose; Hernandez-Pando, Rogelio

2009-01-01

After encounter with Mycobacterium tuberculosis, a series of non-uniform immune responses are triggered that define the course of the infection. Eight M. tuberculosis strains were selected from a prospective population-based study of pulmonary tuberculosis patients (1995–2003) based on relevant clinical/epidemiological patterns and tested in a well-characterized BALB/c mouse model of progressive pulmonary tuberculosis. In addition, a new mouse model of transmissibility consisting of prolonged cohousing (up to 60 days) of infected and naïve animals was tested. Four phenotypes were defined based on strain virulence (mouse survival, lung bacillary load and tissue damage), immunology response (cytokine expression determined by real-time polymerase chain reaction) and transmissibility (lung bacillary loads and cutaneous delayed-type hypersensitivity in naïve animals).We identified four clearly defined strain phenotypes: (1) hypervirulent strain with non-protective immune response and highly transmissible; (2) virulent strain, associated with high expression of proinflammatory cytokines (tumour necrosis factor and interferon) and very low anti-inflammatory cytokine expression (interleukins 4 and 10), which induced accelerated death by immunopathology; (3) strain inducing efficient protective immunity with lower virulence, and (4) strain demonstrating strong and early macrophage activation (innate immunity) with delayed participation of acquired immunity (interferon expression). We were able to correlate virulent and transmissible phenotypes in the mouse model and markers of community transmission such as tuberculin reactivity among contacts, rapid progression to disease and cluster status. However, we were not able to find correlation with the other two phenotypes. Our new transmission model supported the hypothesis that among these strains increased virulence was linked to increased transmission. PMID:19191912

Extracellular Gelatinase of Enterococcus faecalis Destroys a Defense System in Insect Hemolymph and Human Serum▿

PubMed Central

Park, Shin Yong; Kim, Kyoung Mi; Lee, Joon Ha; Seo, Sook Jae; Lee, In Hee

2007-01-01

We isolated Enterococcus faecalis from the body fluids of dead larvae of the greater wax moth, Galleria mellonella. Extracellular gelatinase (GelE) and serine protease (SprE), both of which are considered putative virulence factors of E. faecalis, were purified from the culture supernatant of E. faecalis. In an attempt to elucidate their virulence mechanisms, purified GelE and SprE were injected into hemolymph of G. mellonella and evaluated with regard to their effects on the immune system of insect hemolymph. As a result, it was determined that E. faecalis GelE degraded an inducible antimicrobial peptide (Gm cecropin) which is known to perform a critical role in host defense during the early phase of microbial infection. The results obtained from the G. mellonella-E. faecalis infection model compelled us to assess the virulence activity of GelE against the complement system in human serum. E. faecalis GelE hydrolyzed C3a and also mediated the degradation of the alpha chain of C3b, thereby inhibiting opsonization and the formation of the membrane attack complex resultant from the activation of the complement cascade triggered by C3 activation. In contrast, E. faecalis SprE exhibited no virulence effect against the immune system of insect hemolymph or human serum tested in this study. PMID:17261598

Differential Virulence and Pathogenesis of West Nile Viruses

PubMed Central

Donadieu, Emilie; Bahuon, Céline; Lowenski, Steeve; Zientara, Stéphan; Coulpier, Muriel; Lecollinet, Sylvie

2013-01-01

West Nile virus (WNV) is a neurotropic flavivirus that cycles between mosquitoes and birds but that can also infect humans, horses, and other vertebrate animals. In most humans, WNV infection remains subclinical. However, 20%–40% of those infected may develop WNV disease, with symptoms ranging from fever to meningoencephalitis. A large variety of WNV strains have been described worldwide. Based on their genetic differences, they have been classified into eight lineages; the pathogenic strains belong to lineages 1 and 2. Ten years ago, Beasley et al. (2002) found that dramatic differences exist in the virulence and neuroinvasion properties of lineage 1 and lineage 2 WNV strains. Further insights on how WNV interacts with its hosts have recently been gained; the virus acts either at the periphery or on the central nervous system (CNS), and these observed differences could help explain the differential virulence and neurovirulence of WNV strains. This review aims to summarize the current state of knowledge on factors that trigger WNV dissemination and CNS invasion as well as on the inflammatory response and CNS damage induced by WNV. Moreover, we will discuss how WNV strains differentially interact with the innate immune system and CNS cells, thus influencing WNV pathogenesis. PMID:24284878

Differential virulence and pathogenesis of West Nile viruses.

PubMed

Donadieu, Emilie; Bahuon, Céline; Lowenski, Steeve; Zientara, Stéphan; Coulpier, Muriel; Lecollinet, Sylvie

2013-11-22

West Nile virus (WNV) is a neurotropic flavivirus that cycles between mosquitoes and birds but that can also infect humans, horses, and other vertebrate animals. In most humans, WNV infection remains subclinical. However, 20%-40% of those infected may develop WNV disease, with symptoms ranging from fever to meningoencephalitis. A large variety of WNV strains have been described worldwide. Based on their genetic differences, they have been classified into eight lineages; the pathogenic strains belong to lineages 1 and 2. Ten years ago, Beasley et al. (2002) found that dramatic differences exist in the virulence and neuroinvasion properties of lineage 1 and lineage 2 WNV strains. Further insights on how WNV interacts with its hosts have recently been gained; the virus acts either at the periphery or on the central nervous system (CNS), and these observed differences could help explain the differential virulence and neurovirulence of WNV strains. This review aims to summarize the current state of knowledge on factors that trigger WNV dissemination and CNS invasion as well as on the inflammatory response and CNS damage induced by WNV. Moreover, we will discuss how WNV strains differentially interact with the innate immune system and CNS cells, thus influencing WNV pathogenesis.

NOD-like receptor cooperativity in effector-triggered immunity.

PubMed

Griebel, Thomas; Maekawa, Takaki; Parker, Jane E

2014-11-01

Intracellular nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are basic elements of innate immunity in plants and animals. Whereas animal NLRs react to conserved microbe- or damage-associated molecular patterns, plant NLRs intercept the actions of diverse pathogen virulence factors (effectors). In this review, we discuss recent genetic and molecular evidence for functional NLR pairs, and discuss the significance of NLR self-association and heteromeric NLR assemblies in the triggering of downstream signaling pathways. We highlight the versatility and impact of cooperating NLR pairs that combine pathogen sensing with the initiation of defense signaling in both plant and animal immunity. We propose that different NLR receptor molecular configurations provide opportunities for fine-tuning resistance pathways and enhancing the host's pathogen recognition spectrum to keep pace with rapidly evolving microbial populations. Copyright © 2014. Published by Elsevier Ltd.

Virulence factors in Escherichia coli urinary tract infection.

PubMed Central

Johnson, J R

1991-01-01

Uropathogenic strains of Escherichia coli are characterized by the expression of distinctive bacterial properties, products, or structures referred to as virulence factors because they help the organism overcome host defenses and colonize or invade the urinary tract. Virulence factors of recognized importance in the pathogenesis of urinary tract infection (UTI) include adhesins (P fimbriae, certain other mannose-resistant adhesins, and type 1 fimbriae), the aerobactin system, hemolysin, K capsule, and resistance to serum killing. This review summarizes the virtual explosion of information regarding the epidemiology, biochemistry, mechanisms of action, and genetic basis of these urovirulence factors that has occurred in the past decade and identifies areas in need of further study. Virulence factor expression is more common among certain genetically related groups of E. coli which constitute virulent clones within the larger E. coli population. In general, the more virulence factors a strain expresses, the more severe an infection it is able to cause. Certain virulence factors specifically favor the development of pyelonephritis, others favor cystitis, and others favor asymptomatic bacteriuria. The currently defined virulence factors clearly contribute to the virulence of wild-type strains but are usually insufficient in themselves to transform an avirulent organism into a pathogen, demonstrating that other as-yet-undefined virulence properties await discovery. Virulence factor testing is a useful epidemiological and research tool but as yet has no defined clinical role. Immunological and biochemical anti-virulence factor interventions are effective in animal models of UTI and hold promise for the prevention of UTI in humans. Images PMID:1672263

Pathogen exploitation of an abscisic acid- and jasmonate-inducible MAPK phosphatase and its interception by Arabidopsis immunity.

PubMed

Mine, Akira; Berens, Matthias L; Nobori, Tatsuya; Anver, Shajahan; Fukumoto, Kaori; Winkelmüller, Thomas M; Takeda, Atsushi; Becker, Dieter; Tsuda, Kenichi

2017-07-11

Phytopathogens promote virulence by, for example, exploiting signaling pathways mediated by phytohormones such as abscisic acid (ABA) and jasmonate (JA). Some plants can counteract pathogen virulence by invoking a potent form of immunity called effector-triggered immunity (ETI). Here, we report that ABA and JA mediate inactivation of the immune-associated MAP kinases (MAPKs), MPK3 and MPK6, in Arabidopsis thaliana ABA induced expression of genes encoding the protein phosphatases 2C (PP2Cs), HAI1 , HAI2 , and HAI3 through ABF/AREB transcription factors. These three HAI PP2Cs interacted with MPK3 and MPK6 and were required for ABA-mediated MPK3/MPK6 inactivation and immune suppression. The bacterial pathogen Pseudomonas syringae pv. tomato ( Pto ) DC3000 activates ABA signaling and produces a JA-mimicking phytotoxin, coronatine (COR), that promotes virulence. We found that Pto DC3000 induces HAI1 through COR-mediated activation of MYC2, a master transcription factor in JA signaling. HAI1 dephosphorylated MPK3 and MPK6 in vitro and was necessary for COR-mediated suppression of MPK3/MPK6 activation and immunity. Intriguingly, upon ETI activation, A. thaliana plants overcame the HAI1-dependent virulence of COR by blocking JA signaling. Finally, we showed conservation of induction of HAI PP2Cs by ABA and JA in other Brassicaceae species. Taken together, these results suggest that ABA and JA signaling pathways, which are hijacked by the bacterial pathogen, converge on the HAI PP2Cs that suppress activation of the immune-associated MAPKs. Also, our data unveil interception of JA-signaling activation as a host counterstrategy against the bacterial suppression of MAPKs during ETI.

Unique Biofilm Signature, Drug Susceptibility and Decreased Virulence in Drosophila through the Pseudomonas aeruginosa Two-Component System PprAB

PubMed Central

Giraud, Caroline; Bernard, Christophe S.; Calderon, Virginie; Ewald, Friederike; Plésiat, Patrick; Nguyen, Cathy; Grunwald, Didier; Attree, Ina; Jeannot, Katy; Fauvarque, Marie-Odile

2012-01-01

Bacterial biofilm is considered as a particular lifestyle helping cells to survive hostile environments triggered by a variety of signals sensed and integrated through adequate regulatory pathways. Pseudomonas aeruginosa, a Gram-negative bacterium causing severe infections in humans, forms biofilms and is a fantastic example for fine-tuning of the transition between planktonic and community lifestyles through two-component systems (TCS). Here we decipher the regulon of the P. aeruginosa response regulator PprB of the TCS PprAB. We identified genes under the control of this TCS and once this pathway is activated, analyzed and dissected at the molecular level the PprB-dependent phenotypes in various models. The TCS PprAB triggers a hyper-biofilm phenotype with a unique adhesive signature made of BapA adhesin, a Type 1 secretion system (T1SS) substrate, CupE CU fimbriae, Flp Type IVb pili and eDNA without EPS involvement. This unique signature is associated with drug hyper-susceptibility, decreased virulence in acutely infected flies and cytotoxicity toward various cell types linked to decreased Type III secretion (T3SS). Moreover, once the PprB pathway is activated, decreased virulence in orally infected flies associated with enhanced biofilm formation and dissemination defect from the intestinal lumen toward the hemolymph compartment is reported. PprB may thus represent a key bacterial adaptation checkpoint of multicellular and aggregative behavior triggering the production of a unique matrix associated with peculiar antibiotic susceptibility and attenuated virulence, a particular interesting breach for therapeutic intervention to consider in view of possible eradication of P. aeruginosa biofilm-associated infections. PMID:23209420

Temperature and Oxidative Stress as Triggers for Virulence Gene Expression in Pathogenic Leptospira spp.

PubMed Central

Fraser, Tricia; Brown, Paul D.

2017-01-01

Leptospirosis is a zooanthroponosis aetiologically caused by pathogenic bacteria belonging to the genus, Leptospira. Environmental signals such as increases in temperatures or oxidative stress can trigger response regulatory modes of virulence genes during infection. This study sought to determine the effect of temperature and oxidative stress on virulence associated genes in highly passaged Leptospira borgpeterseneii Jules and L. interrogans Portlandvere. Bacteria were grown in EMJH at 30°C, 37°C, or at 30°C before being transferred to 37°C. A total of 14 virulence-associated genes (fliY, invA, lenA, ligB, lipL32, lipL36, lipL41, lipL45, loa22, lsa21, mce, ompL1, sph2, and tlyC) were assessed using endpoint PCR. Transcriptional analyses of lenA, lipL32, lipL41, loa22, sph2 were assessed by quantitative real-time RT-PCR at the temperature conditions. To assess oxidative stress, bacteria were exposed to H2O2 for 30 and 60 min with or without the temperature stress. All genes except ligB (for Portlandvere) and ligB and mce (for Jules) were detectable in the strains. Quantitatively, temperature stress resulted in significant changes in gene expression within species or between species. Temperature changes were more influential in gene expression for Jules, particularly at 30°C and upshift conditions; at 37°C, expression levels were higher for Portlandvere. However, compared to Jules, where temperature was influential in two of five genes, temperature was an essential element in four of five genes in Portlandvere exposed to oxidative stress. At both low and high oxidative stress levels, the interplay between genetic predisposition (larger genome size) and temperature was biased towards Portlandvere particularly at 30°C and upshift conditions. While it is clear that expression of many virulence genes in highly passaged strains of Leptospira are attenuated or lost, genetic predisposition, changes in growth temperature and/or oxidative intensity and/or duration were factors which acted in isolation or together with other regulatory cues to contribute to the variable gene expression observed in this study. Overall, differential gene expression in serovar Portlandvere was more responsive to temperature and oxidative stress. PMID:28536558

Plant targets for Pseudomonas syringae type III effectors: virulence targets or guarded decoys?

PubMed

Block, Anna; Alfano, James R

2011-02-01

The phytopathogenic bacterium Pseudomonas syringae can suppress both pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI) by the injection of type III effector (T3E) proteins into host cells. T3Es achieve immune suppression using a variety of strategies including interference with immune receptor signaling, blocking RNA pathways and vesicle trafficking, and altering organelle function. T3Es can be recognized indirectly by resistance proteins monitoring specific T3E targets resulting in ETI. It is presently unclear whether the monitored targets represent bona fide virulence targets or guarded decoys. Extensive overlap between PTI and ETI signaling suggests that T3Es may suppress both pathways through common targets and by possessing multiple activities. Copyright © 2010 Elsevier Ltd. All rights reserved.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoon, Hyunjin; Ansong, Charles; McDermott, Jason E.

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 ofmore » 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.« less

CodY-Dependent Regulation of Sporulation in Clostridium difficile.

PubMed

Nawrocki, Kathryn L; Edwards, Adrianne N; Daou, Nadine; Bouillaut, Laurent; McBride, Shonna M

2016-08-01

Clostridium difficile must form a spore to survive outside the gastrointestinal tract. The factors that trigger sporulation in C. difficile remain poorly understood. Previous studies have suggested that a link exists between nutritional status and sporulation initiation in C. difficile In this study, we investigated the impact of the global nutritional regulator CodY on sporulation in C. difficile strains from the historical 012 ribotype and the current epidemic 027 ribotype. Sporulation frequencies were increased in both backgrounds, demonstrating that CodY represses sporulation in C. difficile The 027 codY mutant exhibited a greater increase in spore formation than the 012 codY mutant. To determine the role of CodY in the observed sporulation phenotypes, we examined several factors that are known to influence sporulation in C. difficile Using transcriptional reporter fusions and quantitative reverse transcription-PCR (qRT-PCR) analysis, we found that two loci associated with the initiation of sporulation, opp and sinR, are regulated by CodY. The data demonstrate that CodY is a repressor of sporulation in C. difficile and that the impact of CodY on sporulation and expression of specific genes is significantly influenced by the strain background. These results suggest that the variability of CodY-dependent regulation is an important contributor to virulence and sporulation in current epidemic isolates. This report provides further evidence that nutritional state, virulence, and sporulation are linked in C. difficile This study sought to examine the relationship between nutrition and sporulation in C. difficile by examining the global nutritional regulator CodY. CodY is a known virulence and nutritional regulator of C. difficile, but its role in sporulation was unknown. Here, we demonstrate that CodY is a negative regulator of sporulation in two different ribotypes of C. difficile We also demonstrate that CodY regulates known effectors of sporulation, Opp and SinR. These results support the idea that nutrient limitation is a trigger for sporulation in C. difficile and that the response to nutrient limitation is coordinated by CodY. Additionally, we demonstrate that CodY has an altered role in sporulation regulation for some strains. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

CodY-Dependent Regulation of Sporulation in Clostridium difficile

PubMed Central

Nawrocki, Kathryn L.; Edwards, Adrianne N.; Daou, Nadine; Bouillaut, Laurent

2016-01-01

ABSTRACT Clostridium difficile must form a spore to survive outside the gastrointestinal tract. The factors that trigger sporulation in C. difficile remain poorly understood. Previous studies have suggested that a link exists between nutritional status and sporulation initiation in C. difficile. In this study, we investigated the impact of the global nutritional regulator CodY on sporulation in C. difficile strains from the historical 012 ribotype and the current epidemic 027 ribotype. Sporulation frequencies were increased in both backgrounds, demonstrating that CodY represses sporulation in C. difficile. The 027 codY mutant exhibited a greater increase in spore formation than the 012 codY mutant. To determine the role of CodY in the observed sporulation phenotypes, we examined several factors that are known to influence sporulation in C. difficile. Using transcriptional reporter fusions and quantitative reverse transcription-PCR (qRT-PCR) analysis, we found that two loci associated with the initiation of sporulation, opp and sinR, are regulated by CodY. The data demonstrate that CodY is a repressor of sporulation in C. difficile and that the impact of CodY on sporulation and expression of specific genes is significantly influenced by the strain background. These results suggest that the variability of CodY-dependent regulation is an important contributor to virulence and sporulation in current epidemic isolates. This report provides further evidence that nutritional state, virulence, and sporulation are linked in C. difficile. IMPORTANCE This study sought to examine the relationship between nutrition and sporulation in C. difficile by examining the global nutritional regulator CodY. CodY is a known virulence and nutritional regulator of C. difficile, but its role in sporulation was unknown. Here, we demonstrate that CodY is a negative regulator of sporulation in two different ribotypes of C. difficile. We also demonstrate that CodY regulates known effectors of sporulation, Opp and SinR. These results support the idea that nutrient limitation is a trigger for sporulation in C. difficile and that the response to nutrient limitation is coordinated by CodY. Additionally, we demonstrate that CodY has an altered role in sporulation regulation for some strains. PMID:27246573

Helicobacter pylori virulence and cancer pathogenesis

PubMed Central

Yamaoka, Yoshio; Graham, David Y

2014-01-01

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. PMID:25052757

Helicobacter pylori virulence and cancer pathogenesis.

PubMed

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.

The observation of mitochondrial movement and ATG5 position in Arabidopsis during the process of infection with virulent and avirulent P. syringae strains

NASA Astrophysics Data System (ADS)

Yang, Liu; Ma, Chao; Chen, Wen li

2012-03-01

Infection of plants with pathogens leads to programmed cell death (PCD) associated with the pathogen-triggered hypersensitive response (HR) during plant innate immunity. In this study, the effects of infection by virulent Pseudomonas syringae pv. tomato (Pst) DC3000 and strains harboring avirulence factors AvrRps4 on the induction of HR-PCD were compared. We used Arabidopsis thaliana plants as materials, which expressed green fluorescent protein labeled mitochondria (mito-GFP) and green fluorescent protein tagged ATG5 (ATG5-GFP), these GFP are instantaneous expression. We found both Pst DC3000 and Pst-avrRps4 could induce mitochondria to assemble, the effect of Pst DC3000 was more obvious. ATG5 was located in chloroplasts after infection with Pst DC3000 or Pst-avrRps4. Under the condition of Pst-avrRps4, the expression of ATG5 was stronger than Pst DC3000 treatment.

Expression of virulence factors by Staphylococcus aureus grown in serum.

PubMed

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.

Staphylococcal leukotoxins trigger free intracellular Ca2+ rise in neurones, signalling through acidic stores and activation of store-operated channels

PubMed Central

Jover, Emmanuel; Tawk, Mira Y; Laventie, Benoît-Joseph; Poulain, Bernard; Prévost, Gilles

2013-01-01

Headache, muscle aches and chest pain of mild to medium intensity are among the most common clinical symptoms in moderate Staphylococcus aureus infections, with severe infections usually associated with worsening pain symptoms. These nociceptive responses of the body raise the question of how bacterial infection impinges on the nervous system. Does S. aureus, or its released virulence factors, act directly on neurones? To address this issue, we evaluated the potential effects on neurones of certain bi-component leukotoxins, which are virulent factors released by the bacterium. The activity of four different leukotoxins was verified by measuring the release of glutamate from rat cerebellar granular neurones. The bi-component γ-haemolysin HlgC/HlgB was the most potent leukotoxin, initiating transient rises in intracellular Ca2+ concentration in cerebellar neurones and in primary sensory neurones from dorsal root ganglia, as probed with the Fura-2 Ca2+ indicator dye. Using pharmacological antagonists of receptors and Ca2+ channels, the variations in intracellular Ca2+ concentration were found independent of the activation of voltage-operatedCa2+ channels or glutamate receptors. Drugs targeting Sarco-Endoplasmic Reticulum Ca2+-ATPase (SERCA) or H+-ATPase and antagonists of the store-operated Ca2+ entry complex blunted, or significantly reduced, the leukotoxin-induced elevation in intracellular Ca2+. Moreover, activation of the ADP-ribosyl cyclase CD38 was also required to initiate the release of Ca2+ from acidic stores. These findings suggest that, prior to forming a pore at the plasma membrane, leukotoxin HlgC/HlgB triggers a multistep process which initiates the release of Ca2+ from lysosomes, modifies the steady-state level of reticular Ca2+ stores and finally activates the Store-Operated Calcium Entry complex. PMID:23152983

Staphylococcal leukotoxins trigger free intracellular Ca(2+) rise in neurones, signalling through acidic stores and activation of store-operated channels.

PubMed

Jover, Emmanuel; Tawk, Mira Y; Laventie, Benoît-Joseph; Poulain, Bernard; Prévost, Gilles

2013-05-01

Headache, muscle aches and chest pain of mild to medium intensity are among the most common clinical symptoms in moderate Staphylococcus aureus infections, with severe infections usually associated with worsening pain symptoms. These nociceptive responses of the body raise the question of how bacterial infection impinges on the nervous system. Does S. aureus, or its released virulence factors, act directly on neurones? To address this issue, we evaluated the potential effects on neurones of certain bi-component leukotoxins, which are virulent factors released by the bacterium. The activity of four different leukotoxins was verified by measuring the release of glutamate from rat cerebellar granular neurones. The bi-component γ-haemolysin HlgC/HlgB was the most potent leukotoxin, initiating transient rises in intracellular Ca(2+) concentration in cerebellar neurones and in primary sensory neurones from dorsal root ganglia, as probed with the Fura-2 Ca(2+) indicator dye. Using pharmacological antagonists of receptors and Ca(2+) channels, the variations in intracellular Ca(2+) concentration were found independent of the activation of voltage-operated Ca(2+) channels or glutamate receptors. Drugs targeting Sarco-Endoplasmic Reticulum Ca(2+)-ATPase (SERCA) or H(+)-ATPase and antagonists of the store-operated Ca(2+) entry complex blunted, or significantly reduced, the leukotoxin-induced elevation in intracellular Ca(2+). Moreover, activation of the ADP-ribosyl cyclase CD38 was also required to initiate the release of Ca(2+) from acidic stores. These findings suggest that, prior to forming a pore at the plasma membrane, leukotoxin HlgC/HlgB triggers a multistep process which initiates the release of Ca(2+) from lysosomes, modifies the steady-state level of reticular Ca(2+) stores and finally activates the Store-Operated Calcium Entry complex. © 2012 Blackwell Publishing Ltd.

Septation of infectious hyphae is critical for appressoria formation and virulence in the smut fungus Ustilago maydis.

PubMed

Freitag, Johannes; Lanver, Daniel; Böhmer, Christian; Schink, Kay Oliver; Bölker, Michael; Sandrock, Björn

2011-05-01

Differentiation of hyphae into specialized infection structures, known as appressoria, is a common feature of plant pathogenic fungi that penetrate the plant cuticle. Appressorium formation in U. maydis is triggered by environmental signals but the molecular mechanism of this hyphal differentiation is largely unknown. Infectious hyphae grow on the leaf surface by inserting regularly spaced retraction septa at the distal end of the tip cell leaving empty sections of collapsed hyphae behind. Here we show that formation of retraction septa is critical for appressorium formation and virulence in U. maydis. We demonstrate that the diaphanous-related formin Drf1 is necessary for actomyosin ring formation during septation of infectious hyphae. Drf1 acts as an effector of a Cdc42 GTPase signaling module, which also consists of the Cdc42-specific guanine nucleotide exchange factor Don1 and the Ste20-like kinase Don3. Deletion of drf1, don1 or don3 abolished formation of retraction septa resulting in reduced virulence. Appressorium formation in these mutants was not completely blocked but infection structures were found only at the tip of short filaments indicating that retraction septa are necessary for appressorium formation in extended infectious hyphae. In addition, appressoria of drf1 mutants penetrated the plant tissue less frequently.

Staphylococcus aureus clonal dynamics and virulence factors in children with atopic dermatitis.

PubMed

Lomholt, Hans; Andersen, Klaus Ejner; Kilian, Mogens

2005-11-01

A prospective cohort study was undertaken to determine the clonal dynamics of Staphylococcus aureus colonization and infection during 1 y in children with atopic dermatitis, and to correlate specific clones, accessory gene regulator (agr) groups, and production of virulence factors with eczema activity. Eleven children were examined every 6 wk with swaps taken from active eczema, anterior nose, axillae and perineum, and scoring of eczema activity by severity scoring of atopic dermatitis (SCORAD). Individual S. aureus clonal types were identified and examined for production of superantigens, toxins, and were assigned to agr groups. S. aureus colonization patterns ranged from rare colonization over transient colonization to persistent colonization by a single clone or a dynamic exchange of up to five clones. Production of no single virulence factor including superantigens and toxins was significantly associated with exacerbation of eczema. In four children there was a shift between visits in agr group of colonizing clones. These shifts were associated with an increased SCORAD value of 19 (SE = 7, p = 0.009). Change of clones belonging to the same agr group was not associated with a higher SCORAD value. In 11 of 12 cases with two different clones co-colonizing a child the clones belonged to the same agr group. In conclusion, this limited group of children with atopic dermatitis showed highly variable colonization patterns of S. aureus, and communication between strains by use of agr encoded octa peptides appeared to be active in vivo. Increased severity of eczema was related to a change in agr group and may have been because of inflammation triggered by the takeover of an antigenically different clone, as agr groups represent ancient phylogenetic lineages.

Candida glabrata: an emerging oral opportunistic pathogen.

PubMed

Li, L; Redding, S; Dongari-Bagtzoglou, A

2007-03-01

Following the widespread use of immunosuppressive therapy and broad-spectrum antimycotic prophylaxis, C. glabrata has emerged as an important opportunistic pathogen in the oral mucosa. In the past, studies on the virulence factors and host-pathogen interactions of this organism were scarce, but continued to rise in recent years. Denture-wearing, immunosuppression, antibiotic therapy, and aging are risk factors for oral colonization or infection with C. glabrata. Compared with C. albicans, C. glabrata exhibits lower oral keratinocyte-adherence capacity, but higher denture-surface-adherence ability. The role of extracellular hydrolase production in the virulence of this organism does not appear to be as important as it is in C. albicans pathogenesis. Although traditionally thought of as a non-transforming yeast organism, both phenotypic switching and pseudohyphal formation have recently been identified in C. glabrata, but their role in pathogenesis is not known. With the exception of granulocyte monocyte colony-stimulating factor, C. glabrata triggers a lower proinflammatory cytokine response in oral epithelial cells than does C. albicans, in a strain-dependent manner. C. glabrata is less susceptible to killing by human beta-defensins than is C. albicans and exhibits various degrees of resistance to the antifungal activity of salivary histatins and mucins. In addition, C. glabrata possesses both innate and acquired resistance against antifungal drugs, due to its ability to modify ergosterol biosynthesis, mitochondrial function, or antifungal efflux. This resistance allows for its relative overgrowth over other susceptible species and may contribute to the recent emergence of C. glabrata infections in chronically immunocompromised populations. Further investigations on the virulence and host-pathogen interactions of C. glabrata are needed to better define the pathogenesis of oral C. glabrata infection in susceptible hosts.

Small RNAs—The Secret Agents in the Plant-Pathogen Interactions

PubMed Central

Weiberg, Arne; Jin, Hailing

2015-01-01

Eukaryotic regulatory small RNAs (sRNAs) that induce RNA interference (RNAi) are involved in a plethora of biological processes, including host immunity and pathogen virulence. In plants, diverse classes of sRNAs contribute to the regulation of host innate immunity. These immune-regulatory sRNAs operate through distinct RNAi pathways that trigger transcriptional or post-transcriptional gene silencing. Similarly, many pathogen-derived sRNAs also regulate pathogen virulence. Remarkably, the influence of regulatory sRNAs is not limited to the individual organism in which they are generated. It can sometimes extend to interacting species from even different kingdoms. There they trigger gene silencing in the interacting organism, a phenomenon called cross-kingdom RNAi. This is exhibited in advanced pathogens and parasites that produce sRNAs to suppress host immunity. Conversely, in host-induced gene silencing (HIGS), diverse plants are engineered to trigger RNAi against pathogens and pests to confer host resistance. Cross-kingdom RNAi opens up a vastly unexplored area of research on mobile sRNAs in the battlefield between hosts and pathogens. PMID:26123395

ORD/NERL CURRENT VRARS RESEARCH

EPA Science Inventory

Virulence is the degree of pathogenicity of a microorganism and virulence factors are the components of an organism that contribute to virulence. Identifying microorganisms using known virulence factors is one method used by microbiologists to distinguish pathogenic isolates fro...

Invasive growth of Saccharomyces cerevisiae depends on environmental triggers: a quantitative model.

PubMed

Zupan, Jure; Raspor, Peter

2010-04-01

In this contribution, the influence of various physicochemical factors on Saccharomyces cerevisiae invasive growth is examined quantitatively. Agar-invasion assays are generally applied for in vitro studies on S. cerevisiae invasiveness, the phenomenon observed as a putative virulence trait in this clinically more and more concerning yeast. However, qualitative agar-invasion assays, used until now, strongly limit the feasibility and interpretation of analyses and therefore needed to be improved. Besides, knowledge in this field concerning the physiology of invasive growth, influenced by stress conditions related to the human alimentary tract and food, is poor and should be expanded. For this purpose, a quantitative agar-invasion assay, presented in our previous work, was applied in this contribution to clarify the significance of the stress factors controlling the adhesion and invasion of the yeast in greater detail. Ten virulent and non-virulent S. cerevisiae strains were assayed at various temperatures, pH values, nutrient starvation, modified atmosphere, and different concentrations of NaCl, CaCl2 and preservatives. With the use of specific parameters, like a relative invasion, eight invasive growth models were hypothesized, which enabled intelligible interpretation of the results. A strong preference for invasive growth (meaning high relative invasion) was observed when the strains were grown on nitrogen- and glucose-depleted media. A significant increase in the invasion of the strains was also determined at temperatures typical for human fever (37-39 degrees C). On the other hand, a strong repressive effect on invasion was found in the presence of salts, anoxia and some preservatives. Copyright 2010 John Wiley & Sons, Ltd.

Legionella pneumophila Effector LpdA Is a Palmitoylated Phospholipase D Virulence Factor

PubMed Central

Aurass, Philipp; Oates, Clare V.; Tate, Edward W.; Hartland, Elizabeth L.; Flieger, Antje

2015-01-01

Legionella pneumophila is a bacterial pathogen that thrives in alveolar macrophages, causing a severe pneumonia. The virulence of L. pneumophila depends on its Dot/Icm type IV secretion system (T4SS), which delivers more than 300 effector proteins into the host, where they rewire cellular signaling to establish a replication-permissive niche, the Legionella-containing vacuole (LCV). Biogenesis of the LCV requires substantial redirection of vesicle trafficking and remodeling of intracellular membranes. In order to achieve this, several T4SS effectors target regulators of membrane trafficking, while others resemble lipases. Here, we characterized LpdA, a phospholipase D effector, which was previously proposed to modulate the lipid composition of the LCV. We found that ectopically expressed LpdA was targeted to the plasma membrane and Rab4- and Rab14-containing vesicles. Subcellular targeting of LpdA required a C-terminal motif, which is posttranslationally modified by S-palmitoylation. Substrate specificity assays showed that LpdA hydrolyzed phosphatidylinositol, -inositol-3- and -4-phosphate, and phosphatidylglycerol to phosphatidic acid (PA) in vitro. In HeLa cells, LpdA generated PA at vesicles and the plasma membrane. Imaging of different phosphatidylinositol phosphate (PIP) and organelle markers revealed that while LpdA did not impact on membrane association of various PIP probes, it triggered fragmentation of the Golgi apparatus. Importantly, although LpdA is translocated inefficiently into cultured cells, an L. pneumophila ΔlpdA mutant displayed reduced replication in murine lungs, suggesting that it is a virulence factor contributing to L. pneumophila infection in vivo. PMID:26216420

Legionella pneumophila Effector LpdA Is a Palmitoylated Phospholipase D Virulence Factor.

PubMed

Schroeder, Gunnar N; Aurass, Philipp; Oates, Clare V; Tate, Edward W; Hartland, Elizabeth L; Flieger, Antje; Frankel, Gad

2015-10-01

Legionella pneumophila is a bacterial pathogen that thrives in alveolar macrophages, causing a severe pneumonia. The virulence of L. pneumophila depends on its Dot/Icm type IV secretion system (T4SS), which delivers more than 300 effector proteins into the host, where they rewire cellular signaling to establish a replication-permissive niche, the Legionella-containing vacuole (LCV). Biogenesis of the LCV requires substantial redirection of vesicle trafficking and remodeling of intracellular membranes. In order to achieve this, several T4SS effectors target regulators of membrane trafficking, while others resemble lipases. Here, we characterized LpdA, a phospholipase D effector, which was previously proposed to modulate the lipid composition of the LCV. We found that ectopically expressed LpdA was targeted to the plasma membrane and Rab4- and Rab14-containing vesicles. Subcellular targeting of LpdA required a C-terminal motif, which is posttranslationally modified by S-palmitoylation. Substrate specificity assays showed that LpdA hydrolyzed phosphatidylinositol, -inositol-3- and -4-phosphate, and phosphatidylglycerol to phosphatidic acid (PA) in vitro. In HeLa cells, LpdA generated PA at vesicles and the plasma membrane. Imaging of different phosphatidylinositol phosphate (PIP) and organelle markers revealed that while LpdA did not impact on membrane association of various PIP probes, it triggered fragmentation of the Golgi apparatus. Importantly, although LpdA is translocated inefficiently into cultured cells, an L. pneumophila ΔlpdA mutant displayed reduced replication in murine lungs, suggesting that it is a virulence factor contributing to L. pneumophila infection in vivo. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

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

PubMed Central

Zhang, Bing; Xia, Yu; Wen, Xianghua; Wang, Xiaohui; Yang, Yunfeng; Zhou, Jizhong; Zhang, Yu

2016-01-01

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. PMID:27907117

Impairment of Infectivity and Immunoprotective Effect of a LYT1 Null Mutant of Trypanosoma cruzi▿

PubMed Central

Zago, M. Paola; Barrio, Alejandra B.; Cardozo, Rubén M.; Duffy, Tomás; Schijman, Alejandro G.; Basombrío, Miguel A.

2008-01-01

Trypanosoma cruzi infection of host cells is a complex process in which many proteins participate but only a few of these proteins have been identified experimentally. One parasite factor likely to be involved is the protein product of LYT1, a single-copy gene cloned, sequenced, and characterized by Manning-Cela et al. (Infect. Immun. 69:3916-3923, 2001). This gene was potentially associated with infectivity, since the deletion of both LYT1 alleles in the CL Brenner strain (the wild type [WT]) resulted in a null mutant T. cruzi clone (L16) that shows an attenuated phenotype in cell culture models. The aim of this work was to characterize the infective behavior of L16 in the insect vector and murine models. The infection of adult Swiss mice with 103 trypomastigotes of both clones revealed a significant reduction in infective behavior of L16, as shown by direct parasitemia, spleen index, and quantitation of tissue parasite burden, suggesting the loss of virulence in the null mutant clone. Although L16 blood counts were almost undetectable, blood-based PCRs indicated the presence of latent and persistent infection during all of the study period and epimastigotes were reisolated from hemocultures until 12 months postinfection. Nevertheless, virulence was not restored in L16 by serial passages in mice, and reisolated parasites lacking the LYT1 gene and bearing the antibiotic resistance genes revealed the stability of the genetic manipulation. Histopathological studies showed a strong diminution in the muscle inflammatory response triggered by L16 compared to that triggered by the WT group, consistent with a lower tissue parasite load. A strong protection against a virulent challenge in both L16- and WT-infected mice was observed; however, the immunizing infection by the genetically modified parasite was highly attenuated. PMID:17938222

Virulence Factors Detection in Aspergillus Isolates from Clinical and Environmental Samples

PubMed Central

Raksha; Urhekar, A.D.

2017-01-01

Introduction Pathogenesis of aspergillosis is dependent on various factors of the host (immune status) and virulence factors of the pathogen which could play a significant role in the pathogenesis of invasive aspergillosis. Aim To study the virulence factors of Aspergillus species isolated from patient samples and environmental samples. Materials and Methods This prospective and experimental study was carried out at Department of Microbiology, MGM Medical College and Hospital, Mumbai, Maharashtra, India, from July 2014 to June 2015. For detection of virulence factors of Aspergillus species, total 750 samples were included in this study (350 from patients and 400 samples from environment). Patient samples and hospital environment samples were subjected to standard methods for screening of Biofilm, Lipase, α–amylase, proteinase, haemolysin, phospholipase and pectinase. Statistical analysis was done using Chi-square test and SPSS (Version 17.0). Results American Type Culture Collection (ATCC) control of Aspergillus oryzae, Aspergillus niger and Aspergillus brasiliensis showed production of all virulence factors. In patient samples maximum virulence factor was produced i.e., α-amylase activity (89.74%) followed by proteinase activity (87.17%), biofilm production was (82.05%) haemolysin activity (79.48%), lipase activity (66.66%), pectinase activity and phospholipase activity (61.53%). In environment samples maximum virulence factor was produced i.e., proteinase activity (41.02%) followed by biofilm production was (38.46%), α-amylase activity (35.89%), haemolysin activity (33.33%), lipase activity (28.20%), phospholipase (25.64%) and pectinase activity (23.07%). The differences in patient and environment virulence factors were statistically significant (p-value <0.05). Conclusion Overall the presence of virulence factors was found more in Aspergillus species isolated from patient samples then environmental samples. This could be due to invasiveness nature of Aspergilli. Aspergillus niger was common isolates from both patient and environmental samples. Our study highlights the possible transmission of Aspergilli from environment to patient. Detection of virulence factors of Aspergillus species help to differentiate between pathogenic and non-pathogenic Aspergilli. Presence of virulence factors confirmed pathogenicity of the isolates. It also helps the physicians to treat the patient when appropriate treatment is needed. PMID:28892890

Potent Innate Immune Response to Pathogenic Leptospira in Human Whole Blood

PubMed Central

Hartskeerl, Rudy A.; van Gorp, Eric C. M.; Schuller, Simone; Monahan, Avril M.; Nally, Jarlath E.; van der Poll, Tom; van 't Veer, Cornelis

2011-01-01

Background Leptospirosis is caused by pathogenic spirochetes of the genus Leptospira. The bacteria enter the human body via abraded skin or mucous membranes and may disseminate throughout. In general the clinical picture is mild but some patients develop rapidly progressive, severe disease with a high case fatality rate. Not much is known about the innate immune response to leptospires during haematogenous dissemination. Previous work showed that a human THP-1 cell line recognized heat-killed leptospires and leptospiral LPS through TLR2 instead of TLR4. The LPS of virulent leptospires displayed a lower potency to trigger TNF production by THP-1 cells compared to LPS of non-virulent leptospires. Methodology/Principal Findings We investigated the host response and killing of virulent and non-virulent Leptospira of different serovars by human THP-1 cells, human PBMC's and human whole blood. Virulence of each leptospiral strain was tested in a well accepted standard guinea pig model. Virulent leptospires displayed complement resistance in human serum and whole blood while in-vitro attenuated non-virulent leptospires were rapidly killed in a complement dependent manner. In vitro stimulation of THP-1 and PBMC's with heat-killed and living leptospires showed differential serovar and cell type dependence of cytokine induction. However, at low, physiological, leptospiral dose, living virulent complement resistant strains were consistently more potent in whole blood stimulations than the corresponding non-virulent complement sensitive strains. At higher dose living virulent and non-virulent leptospires were equipotent in whole blood. Inhibition of different TLRs indicated that both TLR2 and TLR4 as well as TLR5 play a role in the whole blood cytokine response to living leptospires. Conclusions/Significance Thus, in a minimally altered system as human whole blood, highly virulent Leptospira are potent inducers of the cytokine response. PMID:21483834

Potent innate immune response to pathogenic leptospira in human whole blood.

PubMed

Goris, Marga G A; Wagenaar, Jiri F P; Hartskeerl, Rudy A; van Gorp, Eric C M; Schuller, Simone; Monahan, Avril M; Nally, Jarlath E; van der Poll, Tom; van 't Veer, Cornelis

2011-03-31

Leptospirosis is caused by pathogenic spirochetes of the genus Leptospira. The bacteria enter the human body via abraded skin or mucous membranes and may disseminate throughout. In general the clinical picture is mild but some patients develop rapidly progressive, severe disease with a high case fatality rate. Not much is known about the innate immune response to leptospires during haematogenous dissemination. Previous work showed that a human THP-1 cell line recognized heat-killed leptospires and leptospiral LPS through TLR2 instead of TLR4. The LPS of virulent leptospires displayed a lower potency to trigger TNF production by THP-1 cells compared to LPS of non-virulent leptospires. We investigated the host response and killing of virulent and non-virulent Leptospira of different serovars by human THP-1 cells, human PBMC's and human whole blood. Virulence of each leptospiral strain was tested in a well accepted standard guinea pig model. Virulent leptospires displayed complement resistance in human serum and whole blood while in-vitro attenuated non-virulent leptospires were rapidly killed in a complement dependent manner. In vitro stimulation of THP-1 and PBMC's with heat-killed and living leptospires showed differential serovar and cell type dependence of cytokine induction. However, at low, physiological, leptospiral dose, living virulent complement resistant strains were consistently more potent in whole blood stimulations than the corresponding non-virulent complement sensitive strains. At higher dose living virulent and non-virulent leptospires were equipotent in whole blood. Inhibition of different TLRs indicated that both TLR2 and TLR4 as well as TLR5 play a role in the whole blood cytokine response to living leptospires. Thus, in a minimally altered system as human whole blood, highly virulent Leptospira are potent inducers of the cytokine response.

DgcA, a diguanylate cyclase from Xanthomonas oryzae pv. oryzae regulates bacterial pathogenicity on rice

PubMed Central

Su, Jianmei; Zou, Xia; Huang, Liangbo; Bai, Tenglong; Liu, Shu; Yuan, Meng; Chou, Shan-Ho; He, Ya-Wen; Wang, Haihong; He, Jin

2016-01-01

Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of rice blight disease as well as a serious phytopathogen worldwide. It is also one of the model organisms for studying bacteria-plant interactions. Current progress in bacterial signal transduction pathways has identified cyclic di-GMP as a major second messenger molecule in controlling Xanthomonas pathogenicity. However, it still remains largely unclear how c-di-GMP regulates the secretion of bacterial virulence factors in Xoo. In this study, we focused on the important roles played by DgcA (XOO3988), one of our previously identified diguanylate cyclases in Xoo, through further investigating the phenotypes of several dgcA-related mutants, namely, the dgcA-knockout mutant ΔdgcA, the dgcA overexpression strain OdgcA, the dgcA complemented strain CdgcA and the wild-type strain. The results showed that dgcA negatively affected virulence, EPS production, bacterial autoaggregation and motility, but positively triggered biofilm formation via modulating the intracellular c-di-GMP levels. RNA-seq data further identified 349 differentially expressed genes controlled by DgcA, providing a foundation for a more solid understanding of the signal transduction pathways in Xoo. Collectively, the present study highlights DgcA as a major regulator of Xoo virulence, and can serve as a potential target for preventing rice blight diseases. PMID:27193392

Structure of the Francisella response regulator QseB receiver domain, and characterization of QseB inhibition by antibiofilm 2-aminoimidazole-based compounds: Inhibition of response regulator QseB by antibiofilm compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milton, Morgan E.; Allen, C. Leigh; Feldmann, Erik A.

With antibiotic resistance increasing at alarming rates, targets for new antimicrobial therapies must be identified. A particularly promising target is the bacterial two-component system. Two-component systems allow bacteria to detect, evaluate and protect themselves against changes in the environment, such as exposure to antibiotics and also to trigger production of virulence factors. Drugs that target the response regulator portion of two-component systems represent a potent new approach so far unexploited. Here, we focus efforts on the highly virulent bacterium Francisella tularensis tularensis. Francisella contains only three response regulators, making it an ideal system to study. In this study, we initiallymore » present the structure of the N-terminal domain of QseB, the response regulator responsible for biofilm formation. Subsequently, using binding assays, computational docking and cellular studies, we show that QseB interacts with2-aminoimidazole based compounds that impede its function. This information will assist in tailoring compounds to act as adjuvants that will enhance the effect of antibiotics.« less

Combinatorial function of velvet and AreA in transcriptional regulation of nitrate utilization and secondary metabolism.

PubMed

López-Berges, Manuel S; Schäfer, Katja; Hera, Concepción; Di Pietro, Antonio

2014-01-01

Velvet is a conserved protein complex that functions as a regulator of fungal development and secondary metabolism. In the soil-inhabiting pathogen Fusarium oxysporum, velvet governs mycotoxin production and virulence on plant and mammalian hosts. Here we report a previously unrecognized role of the velvet complex in regulation of nitrate metabolism. F. oxysporum mutants lacking VeA or LaeA, two key components of the complex, were impaired in growth on the non-preferred nitrogen sources nitrate and nitrite. Both velvet and the general nitrogen response GATA factor AreA were required for transcriptional activation of nitrate (nit1) and nitrite (nii1) reductase genes under de-repressing conditions, as well as for the nitrate-triggered increase in chromatin accessibility at the nit1 locus. AreA also contributed to chromatin accessibility and expression of two velvet-regulated gene clusters, encoding biosynthesis of the mycotoxin beauvericin and of the siderophore ferricrocin. Thus, velvet and AreA coordinately orchestrate primary and secondary metabolism as well as virulence functions in F. oxysporum. Copyright © 2013 Elsevier Inc. All rights reserved.

Community-associated and healthcare-associated methicillin-resistant Staphylococcus aureus virulence toward Caenorhabditis elegans compared.

PubMed

Day, Shandra R; Moore, Christopher M; Kundzins, John R; Sifri, Costi D

2012-11-15

Community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged as major human pathogens. CA-MRSA virulence appears to be distinct from healthcare-associated (HA) MRSA with several factors [α-hemolysin (Hla), Panton-Valentine leukocidin (PVL), α-type phenol soluble modulins (PSMα) and SCCmec IV] postulated to enhance virulence or fitness. Using the Caenorhabditis elegans infection model, we compared the virulence of clinical and laboratory isolates of CA-MRSA and HA-MRSA and explored the contribution of CA-MRSA associated virulence factors to nematode killing. All CA-MRSA strains were highly pathogenic to nematodes, while HA-MRSA strains demonstrated variable nematode killing. Nematode killing by isogenic mutants of hla or the loci for PVL, PSMα, PSMβ, PSMδ or SCCmec IV was not different than the parental strains. These results demonstrate that CA-MRSA is highly virulent, shows some strains of HA-MRSA are equally virulent toward nematodes and suggests CA-MRSA virulence in C. elegans is not linked to a single virulence factor.

Community-associated and healthcare-associated methicillin-resistant Staphylococcus aureus virulence toward Caenorhabditis elegans compared

PubMed Central

Day, Shandra R.; Moore, Christopher M.; Kundzins, John R.; Sifri, Costi D.

2012-01-01

Community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged as major human pathogens. CA-MRSA virulence appears to be distinct from healthcare-associated (HA) MRSA with several factors [α-hemolysin (Hla), Panton-Valentine leukocidin (PVL), α-type phenol soluble modulins (PSMα) and SCCmec IV] postulated to enhance virulence or fitness. Using the Caenorhabditis elegans infection model, we compared the virulence of clinical and laboratory isolates of CA-MRSA and HA-MRSA and explored the contribution of CA-MRSA associated virulence factors to nematode killing. All CA-MRSA strains were highly pathogenic to nematodes, while HA-MRSA strains demonstrated variable nematode killing. Nematode killing by isogenic mutants of hla or the loci for PVL, PSMα, PSMβ, PSMδ or SCCmec IV was not different than the parental strains. These results demonstrate that CA-MRSA is highly virulent, shows some strains of HA-MRSA are equally virulent toward nematodes and suggests CA-MRSA virulence in C. elegans is not linked to a single virulence factor. PMID:23076331

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

NASA Astrophysics Data System (ADS)

Bartell, Jennifer A.; Blazier, Anna S.; Yen, Phillip; Thøgersen, Juliane C.; Jelsbak, Lars; Goldberg, Joanna B.; Papin, Jason A.

2017-03-01

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 to metabolism. We evaluate the complex interrelationships between growth and virulence-linked pathways using a genome-scale metabolic network reconstruction of Pseudomonas aeruginosa strain PA14 and an updated, expanded reconstruction of P. aeruginosa strain PAO1. The PA14 reconstruction accounts for the activity of 112 virulence-linked genes and virulence factor synthesis pathways that produce 17 unique compounds. We integrate eight published genome-scale mutant screens to validate gene essentiality predictions in rich media, contextualize intra-screen discrepancies and evaluate virulence-linked gene distribution across essentiality datasets. Computational screening further elucidates interconnectivity between inhibition of virulence factor synthesis and growth. Successful validation of selected gene perturbations using PA14 transposon mutants demonstrates the utility of model-driven screening of therapeutic targets.

Multiplex-PCR-Based Screening and Computational Modeling of Virulence Factors and T-Cell Mediated Immunity in Helicobacter pylori Infections for Accurate Clinical Diagnosis.

PubMed

Oktem-Okullu, Sinem; Tiftikci, Arzu; Saruc, Murat; Cicek, Bahattin; Vardareli, Eser; Tozun, Nurdan; Kocagoz, Tanil; Sezerman, Ugur; Yavuz, Ahmet Sinan; Sayi-Yazgan, Ayca

2015-01-01

The outcome of H. pylori infection is closely related with bacteria's virulence factors and host immune response. The association between T cells and H. pylori infection has been identified, but the effects of the nine major H. pylori specific virulence factors; cagA, vacA, oipA, babA, hpaA, napA, dupA, ureA, ureB on T cell response in H. pylori infected patients have not been fully elucidated. We developed a multiplex- PCR assay to detect nine H. pylori virulence genes with in a three PCR reactions. Also, the expression levels of Th1, Th17 and Treg cell specific cytokines and transcription factors were detected by using qRT-PCR assays. Furthermore, a novel expert derived model is developed to identify set of factors and rules that can distinguish the ulcer patients from gastritis patients. Within all virulence factors that we tested, we identified a correlation between the presence of napA virulence gene and ulcer disease as a first data. Additionally, a positive correlation between the H. pylori dupA virulence factor and IFN-γ, and H. pylori babA virulence factor and IL-17 was detected in gastritis and ulcer patients respectively. By using computer-based models, clinical outcomes of a patients infected with H. pylori can be predicted by screening the patient's H. pylori vacA m1/m2, ureA and cagA status and IFN-γ (Th1), IL-17 (Th17), and FOXP3 (Treg) expression levels. Herein, we report, for the first time, the relationship between H. pylori virulence factors and host immune responses for diagnostic prediction of gastric diseases using computer-based models.

Multiplex-PCR-Based Screening and Computational Modeling of Virulence Factors and T-Cell Mediated Immunity in Helicobacter pylori Infections for Accurate Clinical Diagnosis

PubMed Central

Oktem-Okullu, Sinem; Tiftikci, Arzu; Saruc, Murat; Cicek, Bahattin; Vardareli, Eser; Tozun, Nurdan; Kocagoz, Tanil; Sezerman, Ugur; Yavuz, Ahmet Sinan; Sayi-Yazgan, Ayca

2015-01-01

The outcome of H. pylori infection is closely related with bacteria's virulence factors and host immune response. The association between T cells and H. pylori infection has been identified, but the effects of the nine major H. pylori specific virulence factors; cagA, vacA, oipA, babA, hpaA, napA, dupA, ureA, ureB on T cell response in H. pylori infected patients have not been fully elucidated. We developed a multiplex- PCR assay to detect nine H. pylori virulence genes with in a three PCR reactions. Also, the expression levels of Th1, Th17 and Treg cell specific cytokines and transcription factors were detected by using qRT-PCR assays. Furthermore, a novel expert derived model is developed to identify set of factors and rules that can distinguish the ulcer patients from gastritis patients. Within all virulence factors that we tested, we identified a correlation between the presence of napA virulence gene and ulcer disease as a first data. Additionally, a positive correlation between the H. pylori dupA virulence factor and IFN-γ, and H. pylori babA virulence factor and IL-17 was detected in gastritis and ulcer patients respectively. By using computer-based models, clinical outcomes of a patients infected with H. pylori can be predicted by screening the patient's H. pylori vacA m1/m2, ureA and cagA status and IFN-γ (Th1), IL-17 (Th17), and FOXP3 (Treg) expression levels. Herein, we report, for the first time, the relationship between H. pylori virulence factors and host immune responses for diagnostic prediction of gastric diseases using computer—based models. PMID:26287606

Functional duality of the cell wall.

PubMed

Latgé, Jean-Paul; Beauvais, Anne

2014-08-01

The polysaccharide cell wall is the extracellular armour of the fungal cell. Although essential in the protection of the fungal cell against aggressive external stresses, the biosynthesis of the polysaccharide core is poorly understood. For a long time it was considered that this cell wall skeleton was a fixed structure whose role was only to be sensed as non-self by the host and consequently trigger the defence response. It is now known that the cell wall polysaccharide composition and localization continuously change to adapt to their environment and that these modifications help the fungus to escape from the immune system. Moreover, cell wall polysaccharides could function as true virulence factors. Copyright © 2014 Elsevier Ltd. All rights reserved.

Using host-pathogen protein interactions to identify and characterize Francisella tularensis virulence factors.

PubMed

Wallqvist, Anders; Memišević, Vesna; Zavaljevski, Nela; Pieper, Rembert; Rajagopala, Seesandra V; Kwon, Keehwan; Yu, Chenggang; Hoover, Timothy A; Reifman, Jaques

2015-12-29

Francisella tularensis is a select bio-threat agent and one of the most virulent intracellular pathogens known, requiring just a few organisms to establish an infection. Although several virulence factors are known, we lack an understanding of virulence factors that act through host-pathogen protein interactions to promote infection. To address these issues in the highly infectious F. tularensis subsp. tularensis Schu S4 strain, we deployed a combined in silico, in vitro, and in vivo analysis to identify virulence factors and their interactions with host proteins to characterize bacterial infection mechanisms. We initially used comparative genomics and literature to identify and select a set of 49 putative and known virulence factors for analysis. Each protein was then subjected to proteome-scale yeast two-hybrid (Y2H) screens with human and murine cDNA libraries to identify potential host-pathogen protein-protein interactions. Based on the bacterial protein interaction profile with both hosts, we selected seven novel putative virulence factors for mutant construction and animal validation experiments. We were able to create five transposon insertion mutants and used them in an intranasal BALB/c mouse challenge model to establish 50 % lethal dose estimates. Three of these, ΔFTT0482c, ΔFTT1538c, and ΔFTT1597, showed attenuation in lethality and can thus be considered novel F. tularensis virulence factors. The analysis of the accompanying Y2H data identified intracellular protein trafficking between the early endosome to the late endosome as an important component in virulence attenuation for these virulence factors. Furthermore, we also used the Y2H data to investigate host protein binding of two known virulence factors, showing that direct protein binding was a component in the modulation of the inflammatory response via activation of mitogen-activated protein kinases and in the oxidative stress response. Direct interactions with specific host proteins and the ability to influence interactions among host proteins are important components for F. tularensis to avoid host-cell defense mechanisms and successfully establish an infection. Although direct host-pathogen protein-protein binding is only one aspect of Francisella virulence, it is a critical component in directly manipulating and interfering with cellular processes in the host cell.

A Red Blood Cell Membrane-Camouflaged Nanoparticle Counteracts Streptolysin O-Mediated Virulence Phenotypes of Invasive Group A Streptococcus

PubMed Central

Escajadillo, Tamara; Olson, Joshua; Luk, Brian T.; Zhang, Liangfang; Nizet, Victor

2017-01-01

Group A Streptococcus (GAS), an important human-specific Gram-positive bacterial pathogen, is associated with a broad spectrum of disease, ranging from mild superficial infections such as pharyngitis and impetigo, to serious invasive infections including necrotizing fasciitis and streptococcal toxic shock syndrome. The GAS pore-forming streptolysin O (SLO) is a well characterized virulence factor produced by nearly all GAS clinical isolates. High level expression of SLO is epidemiologically linked to intercontinental dissemination of hypervirulent clonotypes and poor clinical outcomes. SLO can trigger macrophage and neutrophil cell death and/or the inactivation of immune cell functions, and promotes tissue injury and bacterial survival in animal models of infection. In the present work, we describe how the pharmacological presentation of red blood cell (RBC) derived biomimetic nanoparticles (“nanosponges”) can sequester SLO and block the ability of GAS to damage host cells, thereby preserving innate immune function and increasing bacterial clearance in vitro and in vivo. Nanosponge administration protected human neutrophils, macrophages, and keratinocytes against SLO-mediated cytotoxicity. This therapeutic intervention prevented SLO-induced macrophage apoptosis and increased neutrophil extracellular trap formation, allowing increased GAS killing by the respective phagocytic cell types. In a murine model of GAS necrotizing skin infection, local administration of the biomimetic nanosponges was associated with decreased lesion size and reduced bacterial colony-forming unit recovery. Utilization of a toxin decoy and capture platform that inactivates the secreted SLO before it contacts the host cell membrane, presents a novel virulence factor targeted strategy that could be a powerful adjunctive therapy in severe GAS infections where morbidity and mortality are high despite antibiotic treatment. PMID:28769806

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

PubMed

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.

Insights into virulence factors determining the pathogenicity of Cronobacter sakazakii.

PubMed

Singh, Niharika; Goel, Gunjan; Raghav, Mamta

2015-01-01

Cronobacter sakazakii is an opportunistic pathogen associated with outbreaks of life-threatening necrotizing enterocolitis, meningitis and sepsis in neonates and infants. The pathogen possesses an array of virulence factors which aid in tissue adhesion, invasion and host cell injury. Although the identification and validation of C. sakazakii virulence factors has been hindered by availability of suitable neonatal animal model, various studies has reported outer membrane protein A (ompA) as a potential virulence marker. Various other plasmid associated genes such as filamentous hemagglutinin (fhaBC), Cronobacter plasminogen activator (cpa) and genes responsible for iron acquisition (eitCBAD and iucABD/iutA) have been reported in different strains of C. sakazakii. Besides these proposed virulence factors, several biophysical growth factors such as formation of biofilms and resistance to various environmental stresses also contributes to the pathogenic potential of this pathogen. This review provides an update on virulence determinants associated with the pathogenesis of C. sakazakii. The potential reservoirs of the pathogen, mode of transmission and epidemiology are also discussed.

Insights into virulence factors determining the pathogenicity of Cronobacter sakazakii

PubMed Central

Singh, Niharika; Goel, Gunjan; Raghav, Mamta

2015-01-01

Cronobacter sakazakii is an opportunistic pathogen associated with outbreaks of life-threatening necrotizing enterocolitis, meningitis and sepsis in neonates and infants. The pathogen possesses an array of virulence factors which aid in tissue adhesion, invasion and host cell injury. Although the identification and validation of C. sakazakii virulence factors has been hindered by availability of suitable neonatal animal model, various studies has reported outer membrane protein A (ompA) as a potential virulence marker. Various other plasmid associated genes such as filamentous hemagglutinin (fhaBC), Cronobacter plasminogen activator (cpa) and genes responsible for iron acquisition (eitCBAD and iucABD/iutA) have been reported in different strains of C. sakazakii. Besides these proposed virulence factors, several biophysical growth factors such as formation of biofilms and resistance to various environmental stresses also contributes to the pathogenic potential of this pathogen. This review provides an update on virulence determinants associated with the pathogenesis of C. sakazakii. The potential reservoirs of the pathogen, mode of transmission and epidemiology are also discussed. PMID:25950947

Escaping Underground Nets: Extracellular DNases Degrade Plant Extracellular Traps and Contribute to Virulence of the Plant Pathogenic Bacterium Ralstonia solanacearum

PubMed Central

Tran, Tuan Minh; MacIntyre, April; Hawes, Martha; Allen, Caitilyn

2016-01-01

Plant root border cells have been recently recognized as an important physical defense against soil-borne pathogens. Root border cells produce an extracellular matrix of protein, polysaccharide and DNA that functions like animal neutrophil extracellular traps to immobilize pathogens. Exposing pea root border cells to the root-infecting bacterial wilt pathogen Ralstonia solanacearum triggered release of DNA-containing extracellular traps in a flagellin-dependent manner. These traps rapidly immobilized the pathogen and killed some cells, but most of the entangled bacteria eventually escaped. The R. solanacearum genome encodes two putative extracellular DNases (exDNases) that are expressed during pathogenesis, suggesting that these exDNases contribute to bacterial virulence by enabling the bacterium to degrade and escape root border cell traps. We tested this hypothesis with R. solanacearum deletion mutants lacking one or both of these nucleases, named NucA and NucB. Functional studies with purified proteins revealed that NucA and NucB are non-specific endonucleases and that NucA is membrane-associated and cation-dependent. Single ΔnucA and ΔnucB mutants and the ΔnucA/B double mutant all had reduced virulence on wilt-susceptible tomato plants in a naturalistic soil-soak inoculation assay. The ΔnucA/B mutant was out-competed by the wild-type strain in planta and was less able to stunt root growth or colonize plant stems. Further, the double nuclease mutant could not escape from root border cells in vitro and was defective in attachment to pea roots. Taken together, these results demonstrate that extracellular DNases are novel virulence factors that help R. solanacearum successfully overcome plant defenses to infect plant roots and cause bacterial wilt disease. PMID:27336156

Host-Nonspecific Iron Acquisition Systems and Virulence in the Zoonotic Serovar of Vibrio vulnificus

PubMed Central

Pajuelo, David; Lee, Chung-Te; Roig, Francisco J.; Lemos, Manuel L.; Hor, Lien-I

2014-01-01

The zoonotic serovar of Vibrio vulnificus (known as biotype 2 serovar E) is the etiological agent of human and fish vibriosis. The aim of the present work was to discover the role of the vulnibactin- and hemin-dependent iron acquisition systems in the pathogenicity of this zoonotic serovar under the hypothesis that both are host-nonspecific virulence factors. To this end, we selected three genes for three outer membrane receptors (vuuA, a receptor for ferric vulnibactin, and hupA and hutR, two hemin receptors), obtained single and multiple mutants as well as complemented strains, and tested them in a series of in vitro and in vivo assays, using eels and mice as animal models. The overall results confirm that hupA and vuuA, but not hutR, are host-nonspecific virulence genes and suggest that a third undescribed host-specific plasmid-encoded system could also be used by the zoonotic serovar in fish. hupA and vuuA were expressed in the internal organs of the animals in the first 24 h of infection, suggesting that they may be needed to achieve the population size required to trigger fatal septicemia. vuuA and hupA were sequenced in strains representative of the genetic diversity of this species, and their phylogenies were reconstructed by multilocus sequence analysis of selected housekeeping and virulence genes as a reference. Given the overall results, we suggest that both genes might form part of the core genes essential not only for disease development but also for the survival of this species in its natural reservoir, the aquatic environment. PMID:24478087

P. brasiliensis Virulence Is Affected by SconC, the Negative Regulator of Inorganic Sulfur Assimilation

PubMed Central

Menino, João Filipe; Saraiva, Margarida; Gomes-Rezende, Jéssica; Sturme, Mark; Pedrosa, Jorge; Castro, António Gil; Ludovico, Paula; Goldman, Gustavo H.; Rodrigues, Fernando

2013-01-01

Conidia/mycelium-to-yeast transition of Paracoccidioides brasiliensis is a critical step for the establishment of paracoccidioidomycosis, a systemic mycosis endemic in Latin America. Thus, knowledge of the factors that mediate this transition is of major importance for the design of intervention strategies. So far, the only known pre-requisites for the accomplishment of the morphological transition are the temperature shift to 37°C and the availability of organic sulfur compounds. In this study, we investigated the auxotrophic nature to organic sulfur of the yeast phase of Paracoccidioides , with special attention to P. brasiliensis species. For this, we addressed the role of SconCp, the negative regulator of the inorganic sulfur assimilation pathway, in the dimorphism and virulence of this pathogen. We show that down-regulation of SCONC allows initial steps of mycelium-to-yeast transition in the absence of organic sulfur compounds, contrarily to the wild-type fungus that cannot undergo mycelium-to-yeast transition under such conditions. However, SCONC down-regulated transformants were unable to sustain yeast growth using inorganic sulfur compounds only. Moreover, pulses with inorganic sulfur in SCONC down-regulated transformants triggered an increase of the inorganic sulfur metabolism, which culminated in a drastic reduction of the ATP and NADPH cellular levels and in higher oxidative stress. Importantly, the down-regulation of SCONC resulted in a decreased virulence of P. brasiliensis, as validated in an in vivo model of infection. Overall, our findings shed light on the inability of P. brasiliensis yeast to rely on inorganic sulfur compounds, correlating its metabolism with cellular energy and redox imbalances. Furthermore, the data herein presented reveal SconCp as a novel virulence determinant of P. brasiliensis. PMID:24066151

Mucin acts as a nutrient source and a signal for the differential expression of genes coding for cellular processes and virulence factors in Acinetobacter baumannii

PubMed Central

Ohneck, Emily J.; Arivett, Brock A.; Fiester, Steven E.; Wood, Cecily R.; Metz, Maeva L.; Simeone, Gabriella M.

2018-01-01

The capacity of Acinetobacter baumannii to persist and cause infections depends on its interaction with abiotic and biotic surfaces, including those found on medical devices and host mucosal surfaces. However, the extracellular stimuli affecting these interactions are poorly understood. Based on our previous observations, we hypothesized that mucin, a glycoprotein secreted by lung epithelial cells, particularly during respiratory infections, significantly alters A. baumannii’s physiology and its interaction with the surrounding environment. Biofilm, virulence and growth assays showed that mucin enhances the interaction of A. baumannii ATCC 19606T with abiotic and biotic surfaces and its cytolytic activity against epithelial cells while serving as a nutrient source. The global effect of mucin on the physiology and virulence of this pathogen is supported by RNA-Seq data showing that its presence in a low nutrient medium results in the differential transcription of 427 predicted protein-coding genes. The reduced expression of ion acquisition genes and the increased transcription of genes coding for energy production together with the detection of mucin degradation indicate that this host glycoprotein is a nutrient source. The increased expression of genes coding for adherence and biofilm biogenesis on abiotic and biotic surfaces, the degradation of phenylacetic acid and the production of an active type VI secretion system further supports the role mucin plays in virulence. Taken together, our observations indicate that A. baumannii recognizes mucin as an environmental signal, which triggers a response cascade that allows this pathogen to acquire critical nutrients and promotes host-pathogen interactions that play a role in the pathogenesis of bacterial infections. PMID:29309434

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, Jun; Zaborin, Alexander; Poroyko, Valeriy

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 polymermore » 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 P. aeruginosa« less

[Virulence factors and pathophysiology of extraintestinal pathogenic Escherichia coli].

PubMed

Bidet, P; Bonarcorsi, S; Bingen, E

2012-11-01

Extraintestinal pathogenic Escherichia coli (ExPEC) causing urinary tract infections, bacteraemia or meningitis are characterized by a particular genetic background (phylogenetic group B2 and D) and the presence, within genetic pathogenicity islands (PAI) or plasmids, of genes encoding virulence factors involved in adhesion to epithelia, crossing of the body barriers (digestive, kidney, bloodbrain), iron uptake and resistance to the immune system. Among the many virulence factors described, two are particularly linked with a pathophysiological process: type P pili PapGII adhesin is linked with acute pyelonephritis, in the absence of abnormal flow of urine, and the K1 capsule is linked with neonatal meningitis. However, if the adhesin PapGII appears as the key factor of pyelonephritis, such that its absence in strain causing the infection is predictive of malformation or a vesico-ureteral reflux, the meningeal virulence of E. coli can not be reduced to a single virulence factor, but results from a combination of factors unique to each clone, and an imbalance between the immune defenses of the host and bacterial virulence. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Network analysis of S. aureus response to ramoplanin reveals modules for virulence factors and resistance mechanisms and characteristic novel genes.

PubMed

Subramanian, Devika; Natarajan, Jeyakumar

2015-12-10

Staphylococcus aureus is a major human pathogen and ramoplanin is an antimicrobial attributed for effective treatment. The goal of this study was to examine the transcriptomic profiles of ramoplanin sensitive and resistant S. aureus to identify putative modules responsible for virulence and resistance-mechanisms and its characteristic novel genes. The dysregulated genes were used to reconstruct protein functional association networks for virulence-factors and resistance-mechanisms individually. Strong link between metabolic-pathways and development of virulence/resistance is suggested. We identified 15 putative modules of virulence factors. Six hypothetical genes were annotated with novel virulence activity among which SACOL0281 was discovered to be an essential virulence factor EsaD. The roles of MazEF toxin-antitoxin system, SACOL0202/SACOL0201 two-component system and that of amino-sugar and nucleotide-sugar metabolism in virulence are also suggested. In addition, 14 putative modules of resistance mechanisms including modules of ribosomal protein-coding genes and metabolic pathways such as biotin-synthesis, TCA-cycle, riboflavin-biosynthesis, peptidoglycan-biosynthesis etc. are also indicated. Copyright © 2015 Elsevier B.V. All rights reserved.

Helicobacter pylori virulence factors in development of gastric carcinoma.

PubMed

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.

Proteomic Characterization of Yersinia pestis Virulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chromy, B; Murphy, G; Gonzales, A

2005-01-05

Yersinia pestis, the etiological agent of plague, functions via the Type III secretion mechanism whereby virulence factors are induced upon interactions with a mammalian host. Here, the Y. pestis proteome was studied by two-dimensional differential gel electrophoresis (2-D DIGE) under physiologically relevant growth conditions mimicking the calcium concentrations and temperatures that the pathogen would encounter in the flea vector and upon interaction with the mammalian host. Over 4100 individual protein spots were detected of which hundreds were differentially expressed in the entire comparative experiment. A total of 43 proteins that were differentially expressed between the vector and host growth conditionsmore » were identified by mass spectrometry. Expected differences in expression were observed for several known virulence factors including catalase-peroxidase (KatY), murine toxin (Ymt), plasminogen activator (Pla), and F1 capsule antigen (Caf1), as well as putative virulence factors. Chaperone proteins and signaling molecules hypothesized to be involved in virulence due to their role in Type III secretion were also identified. Other differentially expressed proteins not previously reported to contribute to virulence are candidates for more detailed mechanistic studies, representing potential new virulence determinants. For example, several sugar metabolism proteins were differentially regulated in response to lower calcium and higher temperature, suggesting these proteins, while not directly connected to virulence, either represent a metabolic switch for survival in the host environment or may facilitate production of virulence factors. Results presented here contribute to a more thorough understanding of the virulence mechanism of Y. pestis through proteomic characterization of the pathogen under induced virulence.« less

Convergent Evolution of Pathogen Effectors toward Reactive Oxygen Species Signaling Networks in Plants.

PubMed

Jwa, Nam-Soo; Hwang, Byung Kook

2017-01-01

Microbial pathogens have evolved protein effectors to promote virulence and cause disease in host plants. Pathogen effectors delivered into plant cells suppress plant immune responses and modulate host metabolism to support the infection processes of pathogens. Reactive oxygen species (ROS) act as cellular signaling molecules to trigger plant immune responses, such as pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity. In this review, we discuss recent insights into the molecular functions of pathogen effectors that target multiple steps in the ROS signaling pathway in plants. The perception of PAMPs by pattern recognition receptors leads to the rapid and strong production of ROS through activation of NADPH oxidase Respiratory Burst Oxidase Homologs (RBOHs) as well as peroxidases. Specific pathogen effectors directly or indirectly interact with plant nucleotide-binding leucine-rich repeat receptors to induce ROS production and the hypersensitive response in plant cells. By contrast, virulent pathogens possess effectors capable of suppressing plant ROS bursts in different ways during infection. PAMP-triggered ROS bursts are suppressed by pathogen effectors that target mitogen-activated protein kinase cascades. Moreover, pathogen effectors target vesicle trafficking or metabolic priming, leading to the suppression of ROS production. Secreted pathogen effectors block the metabolic coenzyme NADP-malic enzyme, inhibiting the transfer of electrons to the NADPH oxidases (RBOHs) responsible for ROS generation. Collectively, pathogen effectors may have evolved to converge on a common host protein network to suppress the common plant immune system, including the ROS burst and cell death response in plants.

Screening for Antimicrobial Resistance Genes and Virulence Factors via Genome Sequencing▿†

PubMed Central

Bennedsen, Mads; Stuer-Lauridsen, Birgitte; Danielsen, Morten; Johansen, Eric

2011-01-01

Second-generation genome sequencing and alignment of the resulting reads to in silico genomes containing antimicrobial resistance and virulence factor genes were used to screen for undesirable genes in 28 strains which could be used in human nutrition. No virulence factor genes were detected, while several isolates contained antimicrobial resistance genes. PMID:21335393

DsbA Plays a Critical and Multifaceted Role in the Production of Secreted Virulence Factors by the Phytopathogen Erwinia carotovora subsp. atroseptica*S⃞

PubMed Central

Coulthurst, Sarah J.; Lilley, Kathryn S.; Hedley, Peter E.; Liu, Hui; Toth, Ian K.; Salmond, George P. C.

2008-01-01

Erwinia carotovora subsp. atroseptica is an enterobacterial phytopathogen causing economically significant soft rot disease. Pathogenesis is mediated by multiple secreted virulence factors, many of which are secreted by the type II (Out) secretion system. DsbA catalyzes the introduction of disulfide bonds into periplasmic and secreted proteins. In this study, the extracellular proteome (secretome) of wild type E. carotovora subsp. atroseptica SCRI1043, and dsbA and out mutants, was analyzed by spectral counting mass spectrometry. This revealed that dsbA inactivation had a huge impact on the secretome and identified diverse DsbA- and Out-dependent secreted proteins, representing known, predicted, and novel candidate virulence factors. Further characterization of the dsbA mutant showed that secreted enzyme activities, motility, production of the quorumsensing signal, and virulence were absent or substantially reduced. The impact of DsbA on secreted virulence factor production was mediated at multiple levels, including impacting on the Out secretion system and the virulence gene regulatory network. Transcriptome analyses revealed that the abundance of a broad, but defined, set of transcripts, including many virulence factors, was altered in the dsbA mutant, identifying a new virulence regulon responsive to extracytoplasmic conditions. In conclusion, DsbA plays a crucial, multifaceted role in the pathogenesis of E. carotovora subsp. atroseptica. PMID:18562317

Vibrio cholerae ToxR downregulates virulence factor production in response to cyclo(Phe-Pro).

PubMed

Bina, X Renee; Taylor, Dawn L; Vikram, Amit; Ante, Vanessa M; Bina, James E

2013-08-27

Vibrio cholerae is an aquatic organism that causes the severe acute diarrheal disease cholera. The ability of V. cholerae to cause disease is dependent upon the production of two critical virulence determinants, cholera toxin (CT) and the toxin-coregulated pilus (TCP). The expression of the genes that encode for CT and TCP production is under the control of a hierarchical regulatory system called the ToxR regulon, which functions to activate virulence gene expression in response to in vivo stimuli. Cyclic dipeptides have been found to be produced by numerous bacteria, yet their biological function remains unknown. V. cholerae has been shown to produce cyclo(Phe-Pro). Previous studies in our laboratory demonstrated that cyclo(Phe-Pro) inhibited V. cholerae virulence factor production. For this study, we report on the mechanism by which cyclo(Phe-Pro) inhibited virulence factor production. We have demonstrated that exogenous cyclo(Phe-Pro) activated the expression of leuO, a LysR-family regulator that had not been previously associated with V. cholerae virulence. Increased leuO expression repressed aphA transcription, which resulted in downregulation of the ToxR regulon and attenuated CT and TCP production. The cyclo(Phe-Pro)-dependent induction of leuO expression was found to be dependent upon the virulence regulator ToxR. Cyclo(Phe-Pro) did not affect toxR transcription or ToxR protein levels but appeared to enhance the ToxR-dependent transcription of leuO. These results have identified leuO as a new component of the ToxR regulon and demonstrate for the first time that ToxR is capable of downregulating virulence gene expression in response to an environmental cue. The ToxR regulon has been a focus of cholera research for more than three decades. During this time, a model has emerged wherein ToxR functions to activate the expression of Vibrio cholerae virulence factors upon host entry. V. cholerae and other enteric bacteria produce cyclo(Phe-Pro), a cyclic dipeptide that we identified as an inhibitor of V. cholerae virulence factor production. This finding suggested that cyclo(Phe-Pro) was a negative effector of virulence factor production and represented a molecule that could potentially be exploited for therapeutic development. In this work, we investigated the mechanism by which cyclo(Phe-Pro) inhibited virulence factor production. We found that cyclo(Phe-Pro) signaled through ToxR to activate the expression of leuO, a new virulence regulator that functioned to repress virulence factor production. Our results have identified a new arm of the ToxR regulon and suggest that ToxR may play a broader role in pathogenesis than previously known.

Thermal control of virulence factors in bacteria: A hot topic

PubMed Central

Lam, Oliver; Wheeler, Jun; Tang, Christoph M

2014-01-01

Pathogenic bacteria sense environmental cues, including the local temperature, to control the production of key virulence factors. Thermal regulation can be achieved at the level of DNA, RNA or protein and although many virulence factors are subject to thermal regulation, the exact mechanisms of control are yet to be elucidated in many instances. Understanding how virulence factors are regulated by temperature presents a significant challenge, as gene expression and protein production are often influenced by complex regulatory networks involving multiple transcription factors in bacteria. Here we highlight some recent insights into thermal regulation of virulence in pathogenic bacteria. We focus on bacteria which cause disease in mammalian hosts, which are at a significantly higher temperature than the outside environment. We outline the mechanisms of thermal regulation and how understanding this fundamental aspect of the biology of bacteria has implications for pathogenesis and human health. PMID:25494856

Diverse mechanisms shape the evolution of virulence factors in the potato late blight pathogen Phytophthora infestans sampled from China

PubMed Central

Wu, E-Jiao; Yang, Li-Na; Zhu, Wen; Chen, Xiao-Mei; Shang, Li-Ping; Zhan, Jiasui

2016-01-01

Evolution of virulence in plant pathogens is still poorly understood but the knowledge is important for the effective use of plant resistance and sustainable disease management. Spatial population dynamics of virulence, race and SSR markers in 140 genotypes sampled from seven geographic locations in China were compared to infer the mechanisms driving the evolution of virulence in Phytophthora infestans (P. infestans). All virulence types and a full spectrum of race complexity, ranging from the race able to infect the universally susceptible cultivar only to all differentials, were detected. Eight and two virulence factors were under diversifying and constraining selection respectively while no natural selection was detected in one of the virulence types. Further analyses revealed excesses in simple and complex races but deficiency in intermediate race and negative associations of annual mean temperature at the site from which pathogen isolates were collected with frequency of virulence to differentials and race complexity in the pathogen populations. These results suggest that host selection may interact with other factors such as climatic conditions in determining the evolutionary trajectory of virulence and race structure in P. infestans and global warming may slow down the emergence of new virulence in the pathogen. PMID:27193142

Associations between anti-microbial resistance phenotypes, anti-microbial resistance genotypes and virulence genes of Escherichia coli isolates from Pakistan and China.

PubMed

Yaqoob, M; Wang, L P; Wang, S; Hussain, S; Memon, J; Kashif, J; Lu, C-P

2013-10-01

The objective of this study was to determine the association between phenotypic resistance, genotypic resistance and virulence genes of Escherichia coli isolates in Jiangsu province, China and Punjab province Pakistan. A total of 62 E. coli isolates were characterized for phenotypic resistance, genotypic resistance and virulence factor genes. The anti-microbial resistance phenotype and genotypes in relation to virulence factor genes were assessed by statistical analysis. Of 20 tested virulence genes, twelve were found and eight were not found in any isolates. sitA and TspE4C2 were the most prevalent virulence genes. Of the 13 anti-microbial agents tested, resistance to ampicillin, sulphonamide and tetracycline was the most frequent. All isolates were multiresistant, and 74% were resistant to trimethoprim and sulphamethaxazole. Phenotypically, tetracycline-, cefotaxime- and trimethoprim-resistant isolates had increased virulence factors as compared with susceptible isolates. Genotypically, resistant genes Tem, ctx-M, Tet, Sul 1, dhfr1, Cat2 and flo-R showed the association with the virulence genes. Almost all classes of anti-microbial-resistant genes have a high association with virulence. Resistant isolates have more virulent genes than the susceptible isolates. © 2012 Blackwell Verlag GmbH.

Virulence from vesicles: Novel mechanisms of host cell injury by Escherichia coli O104:H4 outbreak strain.

PubMed

Kunsmann, Lisa; Rüter, Christian; Bauwens, Andreas; Greune, Lilo; Glüder, Malte; Kemper, Björn; Fruth, Angelika; Wai, Sun Nyunt; He, Xiaohua; Lloubes, Roland; Schmidt, M Alexander; Dobrindt, Ulrich; Mellmann, Alexander; Karch, Helge; Bielaszewska, Martina

2015-08-18

The highly virulent Escherichia coli O104:H4 that caused the large 2011 outbreak of diarrhoea and haemolytic uraemic syndrome secretes blended virulence factors of enterohaemorrhagic and enteroaggregative E. coli, but their secretion pathways are unknown. We demonstrate that the outbreak strain releases a cocktail of virulence factors via outer membrane vesicles (OMVs) shed during growth. The OMVs contain Shiga toxin (Stx) 2a, the major virulence factor of the strain, Shigella enterotoxin 1, H4 flagellin, and O104 lipopolysaccharide. The OMVs bind to and are internalised by human intestinal epithelial cells via dynamin-dependent and Stx2a-independent endocytosis, deliver the OMV-associated virulence factors intracellularly and induce caspase-9-mediated apoptosis and interleukin-8 secretion. Stx2a is the key OMV component responsible for the cytotoxicity, whereas flagellin and lipopolysaccharide are the major interleukin-8 inducers. The OMVs represent novel ways for the E. coli O104:H4 outbreak strain to deliver pathogenic cargoes and injure host cells.

Mining Host-Pathogen Protein Interactions to Characterize Burkholderia mallei Infectivity Mechanisms

DTIC Science & Technology

2015-03-04

were shown to attenuate disease progression in an aerosol infection animal model using the virulent Burkholderia mallei ATCC 23344 strain. Here, we...performed an extended analysis of primarily nine B. mallei virulence factors and their interactions with human proteins to map out how the bacteria can...virulent Burkholderia mallei ATCC 23344 strain. Here, we performed an extended analysis of primarily nine B. mallei virulence factors and their

Variations in Virulence and Molecular Biology among Emerging Strains of Clostridium difficile

PubMed Central

Hunt, Jonathan J.

2013-01-01

SUMMARY Clostridium difficile is a Gram-positive, spore-forming organism which infects and colonizes the large intestine, produces potent toxins, triggers inflammation, and causes significant systemic complications. Treating C. difficile infection (CDI) has always been difficult, because the disease is both caused and resolved by antibiotic treatment. For three and a half decades, C. difficile has presented a treatment challenge to clinicians, and the situation took a turn for the worse about 10 years ago. An increase in epidemic outbreaks related to CDI was first noticed around 2003, and these outbreaks correlated with a sudden increase in the mortality rate of this illness. Further studies discovered that these changes in CDI epidemiology were associated with the rapid emergence of hypervirulent strains of C. difficile, now collectively referred to as NAP1/BI/027 strains. The discovery of new epidemic strains of C. difficile has provided a unique opportunity for retrospective and prospective studies that have sought to understand how these strains have essentially replaced more historical strains as a major cause of CDI. Moreover, detailed studies on the pathogenesis of NAP1/BI/027 strains are leading to new hypotheses on how this emerging strain causes severe disease and is more commonly associated with epidemics. In this review, we provide an overview of CDI, discuss critical mechanisms of C. difficile virulence, and explain how differences in virulence-associated factors between historical and newly emerging strains might explain the hypervirulence exhibited by this pathogen during the past decade. PMID:24296572

Differential immune responses to Segniliparus rotundus and Segniliparus rugosus infection and analysis of their comparative virulence profiles.

PubMed

Kim, Jong-Seok; Kim, Woo Sik; Lee, Keehoon; Won, Choul-Jae; Kim, Jin Man; Eum, Seok-Yong; Koh, Won-Jung; Shin, Sung Jae

2013-01-01

Two closely related bacterial species, Segniliparus rotundus and Segniliparus rugosus, have emerged as important human pathogens, but little is known about the immune responses they elicit or their comparative pathophysiologies. To determine the virulence and immune responses of the two species, we compared their abilities to grow in phagocytic and non-phagocytic cells. Both species maintained non-replicating states within A549 epithelial cells. S. rugosus persisted longer and multiplied more rapidly inside murine bone marrow-derived macrophages (BMDMs), induced more pro-inflammatory cytokines, and induced higher levels of macrophage necrosis. Activation of BMDMs by both species was mediated by toll-like receptor 2 (TLR2), followed by mitogen-activated protein kinases (MAPK) and nuclear factor κB (NF-κB) signaling pathways, indicating a critical role for TLR2 in Segniliparus-induced macrophage activation. S. rugosus triggered faster and stronger activation of MAPK signaling and IκB degradation, indicating that S. rugosus induces more pro-inflammatory cytokines than S. rotundus. Multifocal granulomatous inflammations in the liver and lung were observed in mice infected with S. rugosus, but S. rotundus was rapidly cleared from all organs tested within 15 days post-infection. Furthermore, S. rugosus induced faster infiltration of innate immune cells such as neutrophils and macrophages to the lung than S. rotundus. Our results suggest that S. rugosus is more virulent and induces a stronger immune response than S. rotundus.

Common Virulence Factors and Tissue Targets of Entomopathogenic Bacteria for Biological Control of Lepidopteran Pests

PubMed Central

Castagnola, Anaïs; Stock, S. Patricia

2014-01-01

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. PMID:24634779

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

PubMed Central

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

Random T-DNA mutagenesis identifies a Cu-Zn-superoxide dismutase gene as a virulence factor of Sclerotinia sclerotiorum

USDA-ARS?s Scientific Manuscript database

Agrobacterium-mediated transformation (AMT) was used to identify potential virulence factors in Sclerotinia sclerotiorum. Screening AMT transformants identified two mutants showing significantly reduced virulence. The mutants showed similar growth rate, colony morphology, and sclerotial and oxalate ...

Multiple virulence factors regulated by quorum sensing may help in establishment and colonisation of urinary tract by Pseudomonas aeruginosa during experimental urinary tract infection.

PubMed

Gupta, P; Gupta, R K; Harjai, K

2013-01-01

Damage caused by an organism during infection is attributed to production of virulence factors. Different virulence factors produced by the organism contribute to its pathogenicity, individually. During infectious conditions, role of virulence factors produced by the pathogen is different, depending upon the site of involvement. Pseudomonas aeruginosa is an opportunistic nosocomial pathogen known to cause infections of the respiratory tract, burn wound, urinary tract and eye. Importance of virulence factors produced by P. Aeruginosa during infections such as keratitis, burn wound and respiratory tract is known. The present study was designed to understand the importance of different virulence factors of P. aeruginosa in urinary tract infection in vivo. An ascending urinary tract infection model was established in mice using standard parent strain PAO1 and its isogenic mutant, JP2. Mice were sacrificed at different time intervals and renal tissue homogenates were used for estimation of renal bacterial load and virulence factors. Both parent and mutant strains were able to reach the renal tissue. PAO 1 PAO1 was isolated from renal tissue till day 5 post-infection. However, the mutant strain was unable to colonise the renal tissue. Failure of mutant strain to colonise was attributed to its inability to produce protease, elastase and rhamnolipid. This study suggests that protease, elastase and rhamnolipid contribute to pathogenesis and survival of P. aeruginosa during urinary tract infection.

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

PubMed

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.

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

PubMed Central

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. PMID:28393050

Increasing RpoS expression causes cell death in Borrelia burgdorferi.

PubMed

Chen, Linxu; Xu, Qilong; Tu, Jiagang; Ge, Yihe; Liu, Jun; Liang, Fang Ting

2013-01-01

RpoS, one of the two alternative σ factors in Borrelia burgdorferi, is tightly controlled by multiple regulators and, in turn, determines expression of many critical virulence factors. Here we show that increasing RpoS expression causes cell death. The immediate effect of increasing RpoS expression was to promote bacterial division and as a consequence result in a rapid increase in cell number before causing bacterial death. No DNA fragmentation or degradation was observed during this induced cell death. Cryo-electron microscopy showed induced cells first formed blebs, which were eventually released from dying cells. Apparently blebbing initiated cell disintegration leading to cell death. These findings led us to hypothesize that increasing RpoS expression triggers intracellular programs and/or pathways that cause spirochete death. The potential biological significance of induced cell death may help B. burgdorferi regulate its population to maintain its life cycle in nature.

Virulence potential of Staphylococcus aureus isolates from Buruli ulcer patients.

PubMed

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.

6-Gingerol reduces Pseudomonas aeruginosa biofilm formation and virulence via quorum sensing inhibition.

PubMed

Kim, Han-Shin; Lee, Sang-Hoon; Byun, Youngjoo; Park, Hee-Deung

2015-03-02

Pseudomonas aeruginosa is a well-known pathogenic bacterium that forms biofilms and produces virulence factors via quorum sensing (QS). Interfering with normal QS interactions between signal molecules and their cognate receptors is a developing strategy for attenuating its virulence. Here we tested the hypothesis that 6-gingerol, a pungent oil of fresh ginger, reduces biofilm formation and virulence by antagonistically binding to P. aeruginosa QS receptors. In silico studies demonstrated molecular binding occurs between 6-gingerol and the QS receptor LasR through hydrogen bonding and hydrophobic interactions. Experimentally 6-gingerol reduced biofilm formation, several virulence factors (e.g., exoprotease, rhamnolipid, and pyocyanin), and mice mortality. Further transcriptome analyses demonstrated that 6-gingerol successfully repressed QS-induced genes, specifically those related to the production of virulence factors. These results strongly support our hypothesis and offer insight into the molecular mechanism that caused QS gene repression.

6-Gingerol reduces Pseudomonas aeruginosa biofilm formation and virulence via quorum sensing inhibition

PubMed Central

Kim, Han-Shin; Lee, Sang-Hoon; Byun, Youngjoo; Park, Hee-Deung

2015-01-01

Pseudomonas aeruginosa is a well-known pathogenic bacterium that forms biofilms and produces virulence factors via quorum sensing (QS). Interfering with normal QS interactions between signal molecules and their cognate receptors is a developing strategy for attenuating its virulence. Here we tested the hypothesis that 6-gingerol, a pungent oil of fresh ginger, reduces biofilm formation and virulence by antagonistically binding to P. aeruginosa QS receptors. In silico studies demonstrated molecular binding occurs between 6-gingerol and the QS receptor LasR through hydrogen bonding and hydrophobic interactions. Experimentally 6-gingerol reduced biofilm formation, several virulence factors (e.g., exoprotease, rhamnolipid, and pyocyanin), and mice mortality. Further transcriptome analyses demonstrated that 6-gingerol successfully repressed QS-induced genes, specifically those related to the production of virulence factors. These results strongly support our hypothesis and offer insight into the molecular mechanism that caused QS gene repression. PMID:25728862

RETRACTED ARTICLE: Quorum-sensing of bacteria and its application

NASA Astrophysics Data System (ADS)

Jiang, Guoliang; Su, Mingxia

2009-12-01

Quorum sensing, or auto induction, as a cell density dependent signaling mechanism in many microorganisms, is triggered via auto inducers which passively diffuse across the bacterial envelope and therefore intracellulaly accumulate only at higher bacterial densities to regulate specialized processes such as genetic competence, bioluminescence, virulence and sporulation. N-acyl homoserine lactones are the most common type of signal molecules. Aquaculture is one of the fastest-growing food-producing industries, but disease outbreaks caused by pathogenic bacteria are a significant constraint on the development of the sector worldwide. Many of these pathogens have been found to be controlled by their quorum sensing systems. As there is relevance between the pathogenic bacteria's virulence factor expression and their auto inducers, quorum quenching is a new effective anti-infective strategy to control infections caused by bacterial pathogens in aquaculture. The techniques used to do this mainly include the following: (1) the inhibition of signal molecule biosynthesis, (2) blocking signal transduction, and (3) chemical inactivation and biodegradation of signal molecules. To provide a basis for finding alternative means of controlling aquatic diseases by quorum quenching instead of treatment by antibiotics and disinfectants, we will discuss the examination, purification and identification of auto inducers in this paper.

A Homolog of Bacillus subtilis Trigger Factor in Listeria monocytogenes Is Involved in Stress Tolerance and Bacterial Virulence

PubMed Central

Bigot, Armelle; Botton, Eleonore; Dubail, Iharilalao; Charbit, Alain

2006-01-01

Molecular chaperones play an essential role in the folding of nascent chain polypeptides, as well as in the refolding and degradation of misfolded or aggregated proteins. They also assist in protein translocation and participate in stress functions. We identified a gene, designated tig, encoding a protein homologous to trigger factor (TF), a cytosolic ribosome-associated chaperone, in the genome of Listeria monocytogenes. We constructed a chromosomal Δtig deletion and evaluated the impact of the mutation on bacterial growth in broth under various stress conditions and on pathogenesis. The Δtig deletion did not affect cell viability but impaired survival in the presence of heat and ethanol stresses. We also identified the ffh gene, encoding a protein homologous to the SRP54 eukaryotic component of the signal recognition particle. However, a Δffh deletion was not tolerated, suggesting that Ffh is essential, as it is in Bacillus subtilis and Escherichia coli. Thus, although dispensable for growth, TF is involved in the stress response of L. monocytogenes. The Δtig mutant showed no or very modest intracellular survival defects in eukaryotic cells. However, in vivo it showed a reduced capacity to persist in the spleens and livers of infected mice, revealing that TF has a role in the pathogenicity of L. monocytogenes. PMID:17021213

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

PubMed

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.

Adhesion and host cell modulation: critical pathogenicity determinants of Bartonella henselae

PubMed Central

2011-01-01

Bartonella henselae, the agent of cat scratch disease and the vasculoproliferative disorders bacillary angiomatosis and peliosis hepatis, contains to date two groups of described pathogenicity factors: adhesins and type IV secretion systems. Bartonella adhesin A (BadA), the Trw system and possibly filamentous hemagglutinin act as promiscous or specific adhesins, whereas the virulence locus (Vir)B/VirD4 type IV secretion system modulates a variety of host cell functions. BadA mediates bacterial adherence to endothelial cells and extracellular matrix proteins and triggers the induction of angiogenic gene programming. The VirB/VirD4 type IV secretion system is responsible for, e.g., inhibition of host cell apoptosis, bacterial persistence in erythrocytes, and endothelial sprouting. The Trw-conjugation system of Bartonella spp. mediates host-specific adherence to erythrocytes. Filamentous hemagglutinins represent additional potential pathogenicity factors which are not yet characterized. The exact molecular functions of these pathogenicity factors and their contribution to an orchestral interplay need to be analyzed to understand B. henselae pathogenicity in detail. PMID:21489243

Identification of potential virulence factors of Cronobacter sakazakii isolates by comparative proteomic analysis.

PubMed

Ye, Yingwang; Li, Hui; Ling, Na; Han, Yongjia; Wu, Qingping; Xu, Xiaoke; Jiao, Rui; Gao, Jina

2016-01-18

Cronobacter is a group of important foodborne pathogens associated with neonatal meningitis, septicemia, and necrotizing enterocolitis. Among Cronobacter species, Cronobacter sakazakii is the most common species in terms of isolation frequency. However, the molecular basis involved in virulence differences among C. sakazakii isolates is still unknown. In this study, based on the determination of virulence differences of C. sakazakii G362 (virulent isolate) and L3101 (attenuated isolate) through intraperitoneal injection, histopathologic analysis (small intestine, kidney, and liver) further confirmed virulence differences. Thereafter, the potential virulence factors were determined using two-dimensional electrophoresis (2-DE) coupled with MALDI/TOP/TOF mass spectrometry. Among a total of 36 protein spots showing differential expression (fold change>1.2), we identified 31 different proteins, of which the expression abundance of 22 was increased in G362. These up-regulated proteins in G362 mainly contained DNA starvation/stationary phase protection protein Dps, OmpA, LuxS, ATP-dependent Clp protease ClpC, and ABC transporter substrate-binding proteins, which might be involved in virulence of C. sakazakii. This is the first report to determine the potential virulence factors of C. sakazakii isolates at the proteomic levels. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed Central

Wang, Guo-Qi; Li, Tong-Tong; Li, Zhi-Rui; Zhang, Li-Cheng

2016-01-01

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. PMID:28074188

[Establishment of multiple regression model for virulence factors of Saccharomyces albicans by random amplified polymorphic DNA bands].

PubMed

Liu, Qi; Wu, Youcong; Yuan, Youhua; Bai, Li; Niu, Kun

2011-12-01

To research the relationship between the virulence factors of Saccharomyces albicans (S. albicans) and the random amplified polymorphic DNA (RAPD) bands of them, and establish the regression model by multiple regression analysis. Extracellular phospholipase, secreted proteinase, ability to generate germ tubes and adhere to oral mucosal cells of 92 strains of S. albicans were measured in vitro; RAPD-polymerase chain reaction (RAPD-PCR) was used to get their bands. Multiple regression for virulence factors of S. albicans and RAPD-PCR bands was established. The extracellular phospholipase activity was associated with 4 RAPD bands: 350, 450, 650 and 1 300 bp (P < 0.05); secreted proteinase activity of S. albicans was associated with 2 bands: 350 and 1 200 bp (P < 0.05); the ability of germ tube produce was associated with 2 bands: 400 and 550 bp (P < 0.05). Some RAPD bands will reflect the virulence factors of S. albicans indirectly. These bands would contain some important messages for regulation of S. albicans virulence factors.

Comparative transcriptomics reveals CrebA as a novel regulator of infection tolerance in D. melanogaster

PubMed Central

2018-01-01

Host responses to infection encompass many processes in addition to activation of the immune system, including metabolic adaptations, stress responses, tissue repair, and other reactions. The response to bacterial infection in Drosophila melanogaster has been classically described in studies that focused on the immune response elicited by a small set of largely avirulent microbes. Thus, we have surprisingly limited knowledge of responses to infection that are outside the canonical immune response, of how the response to pathogenic infection differs from that to avirulent bacteria, or even of how generic the response to various microbes is and what regulates that core response. In this study, we addressed these questions by profiling the D. melanogaster transcriptomic response to 10 bacteria that span the spectrum of virulence. We found that each bacterium triggers a unique transcriptional response, with distinct genes making up to one third of the response elicited by highly virulent bacteria. We also identified a core set of 252 genes that are differentially expressed in response to the majority of bacteria tested. Among these, we determined that the transcription factor CrebA is a novel regulator of infection tolerance. Knock-down of CrebA significantly increased mortality from microbial infection without any concomitant change in bacterial number. Upon infection, CrebA is upregulated by both the Toll and Imd pathways in the fat body, where it is required to induce the expression of secretory pathway genes. Loss of CrebA during infection triggered endoplasmic reticulum (ER) stress and activated the unfolded protein response (UPR), which contributed to infection-induced mortality. Altogether, our study reveals essential features of the response to bacterial infection and elucidates the function of a novel regulator of infection tolerance. PMID:29394281

Virulence Factors of Streptococcus mutans.

DTIC Science & Technology

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

Molecular investigation of virulence factors of Brucella melitensis and Brucella abortus strains isolated from clinical and non-clinical samples.

PubMed

Mirnejad, Reza; Jazi, Faramarz Masjedian; Mostafaei, Shayan; Sedighi, Mansour

2017-08-01

Brucella is zoonotic pathogen that induces abortion and sterility in domestic mammals and chronic infections in humans called Malta fever. It is a facultative intracellular potential pathogen with high infectivity. The virulence of Brucella is dependent upon its potential virulence factors such as enzymes and cell envelope associated virulence genes. The aim of this study was to investigate the Brucella virulence factors among strains isolated from humans and animals in different parts of Iran. Seventy eight strains of Brucella species isolated from suspected human and animal cases from several provinces of Iran during 2015-2016 and identified by phenotypic and molecular methods. The multiplex-PCR (M-PCR) assay was performed in order to detect the ure, wbkA, omp19, mviN, manA and perA genes by using gene specific primers. Out of 78 isolates of Brucella spp., 57 (73%) and 21 (27%) isolates were detected as B. melitensis and B. abortus, respectively, by molecular method. The relative frequency of virulence genes ure, wbkA, omp19, mviN, manA and perA were 74.4%, 89.7%, 93.6%, 94.9%, 100% and 92.3%, respectively. Our results indicate that the most of Brucella strains isolated from this region possess high percent of virulence factor genes (ure, wbkA, omp19, mviN, manA and perA) in their genome. So, each step of infection can be mediated by a number of virulence factors and each strain may have a unique combination of these factors that affected the rate of bacterial pathogenesis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Association between virulence profile, biofilm formation and phylogenetic groups of Escherichia coli causing urinary tract infection and the commensal gut microbiota: A comparative analysis.

PubMed

Hashemizadeh, Zahra; Kalantar-Neyestanaki, Davood; Mansouri, Shahla

2017-09-01

Variety of virulence factors are involved in the pathogenicity of Escherichia coli, the common cause of the urinary tract infections (UTIs). The aim of this study was to determine some virulence factors involved in the pathogenicity and the phylogenetic grouping of E. coli from UTIs compared with the E. coli isolates from gut microbiota (fecal flora). The isolates were tested for biofilm formation, haemagglutination, cell surface hydrophobicity (CSH), hemolysin production, phylogenetic grouping and the distribution of 6 known virulence genes. Isolates from UTIs showed a significantly higher prevalence of haemagglutination and hemolysin production compared with fecal flora (P ≤ 0.05), while biofilm formation and cell surface hydrophobicity (CSH) were not significantly different among the groups. Prevalence of virulence genes fimH, kpsMT ll, iutA, sat, hlyA, and cnf1 among all isolates were: 94.5%, 66.95%, 67.8%, 39%, 23.07% and 21.08%, respectively. The genes for hlyA, cnf1, kpsMT ll were found to be higher in UTI isolates compared to fecal flora (P ≤ 0.05). The frequency of the isolates in the phylogenetic groups B2, D, A and B1 were 36.7%, 31.3%, 16.2% and 15.6%, respectively. All the virulence genes except fimH were found to be significantly higher in the isolates of groups B2 and D. The results suggests that certain factors are necessary for the host colonization and infection and they are common in both virulent and non-virulent strains, and that the strains in the groups A and B1 having the lower virulence factors must acquire these factors when the condition is in favor of their dissemination to the urinary tract. In contrast the isolates in the groups B2 and D appeared to be potentially virulent. Copyright © 2017. Published by Elsevier Ltd.

Convergent Evolution of Pathogen Effectors toward Reactive Oxygen Species Signaling Networks in Plants

PubMed Central

Jwa, Nam-Soo; Hwang, Byung Kook

2017-01-01

Microbial pathogens have evolved protein effectors to promote virulence and cause disease in host plants. Pathogen effectors delivered into plant cells suppress plant immune responses and modulate host metabolism to support the infection processes of pathogens. Reactive oxygen species (ROS) act as cellular signaling molecules to trigger plant immune responses, such as pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity. In this review, we discuss recent insights into the molecular functions of pathogen effectors that target multiple steps in the ROS signaling pathway in plants. The perception of PAMPs by pattern recognition receptors leads to the rapid and strong production of ROS through activation of NADPH oxidase Respiratory Burst Oxidase Homologs (RBOHs) as well as peroxidases. Specific pathogen effectors directly or indirectly interact with plant nucleotide-binding leucine-rich repeat receptors to induce ROS production and the hypersensitive response in plant cells. By contrast, virulent pathogens possess effectors capable of suppressing plant ROS bursts in different ways during infection. PAMP-triggered ROS bursts are suppressed by pathogen effectors that target mitogen-activated protein kinase cascades. Moreover, pathogen effectors target vesicle trafficking or metabolic priming, leading to the suppression of ROS production. Secreted pathogen effectors block the metabolic coenzyme NADP-malic enzyme, inhibiting the transfer of electrons to the NADPH oxidases (RBOHs) responsible for ROS generation. Collectively, pathogen effectors may have evolved to converge on a common host protein network to suppress the common plant immune system, including the ROS burst and cell death response in plants. PMID:29033963

Clostridium difficile virulence factors: Insights into an anaerobic spore-forming pathogen.

PubMed

Awad, Milena M; Johanesen, Priscilla A; Carter, Glen P; Rose, Edward; Lyras, Dena

2014-01-01

The worldwide emergence of epidemic strains of Clostridium difficile linked to increased disease severity and mortality has resulted in greater research efforts toward determining the virulence factors and pathogenesis mechanisms used by this organism to cause disease. C. difficile is an opportunist pathogen that employs many factors to infect and damage the host, often with devastating consequences. This review will focus on the role of the 2 major virulence factors, toxin A (TcdA) and toxin B (TcdB), as well as the role of other putative virulence factors, such as binary toxin, in C. difficile-mediated infection. Consideration is given to the importance of spores in both the initiation of disease and disease recurrence and also to the role that surface proteins play in host interactions.

Clostridium difficile virulence factors: Insights into an anaerobic spore-forming pathogen

PubMed Central

Awad, Milena M; Johanesen, Priscilla A; Carter, Glen P; Rose, Edward; Lyras, Dena

2014-01-01

The worldwide emergence of epidemic strains of Clostridium difficile linked to increased disease severity and mortality has resulted in greater research efforts toward determining the virulence factors and pathogenesis mechanisms used by this organism to cause disease. C. difficile is an opportunist pathogen that employs many factors to infect and damage the host, often with devastating consequences. This review will focus on the role of the 2 major virulence factors, toxin A (TcdA) and toxin B (TcdB), as well as the role of other putative virulence factors, such as binary toxin, in C. difficile-mediated infection. Consideration is given to the importance of spores in both the initiation of disease and disease recurrence and also to the role that surface proteins play in host interactions. PMID:25483328

A direct link between carbohydrate utilization and virulence in the major human pathogen group A Streptococcus.

PubMed

Shelburne, Samuel A; Keith, David; Horstmann, Nicola; Sumby, Paul; Davenport, Michael T; Graviss, Edward A; Brennan, Richard G; Musser, James M

2008-02-05

Although central to pathogenesis, the molecular mechanisms used by microbes to regulate virulence factor production in specific environments during host-pathogen interaction are poorly defined. Several recent ex vivo and in vivo studies have found that the level of group A Streptococcus (GAS) virulence factor gene transcripts is temporally related to altered expression of genes encoding carbohydrate utilization proteins. These findings stimulated us to analyze the role in pathogenesis of catabolite control protein A (CcpA), a GAS ortholog of a key global regulator of carbohydrate metabolism in Bacillus subtilis. Inasmuch as the genomewide effects of CcpA in a human pathogen are unknown, we analyzed the transcriptome of a DeltaccpA isogenic mutant strain grown in nutrient-rich medium. CcpA influences the transcript levels of many carbohydrate utilization genes and several well characterized GAS virulence factors, including the potent cytolysin streptolysin S. Compared with the wild-type parental strain, the DeltaccpA isogenic mutant strain was significantly less virulent in a mouse model of invasive infection. Moreover, the isogenic mutant strain was significantly impaired in ability to colonize the mouse oropharynx. When grown in human saliva, a nutrient-limited environment, CcpA influenced production of several key virulence factors not influenced during growth in nutrient-rich medium. Purified recombinant CcpA bound to the promoter region of the gene encoding streptolysin S. Our discovery that GAS virulence and complex carbohydrate utilization are directly linked through CcpA provides enhanced understanding of a mechanism used by a Gram-positive pathogen to modulate virulence factor production in specific environments.

Resveratrol Induces Apoptosis-Like Death and Prevents In Vitro and In Vivo Virulence of Entamoeba histolytica.

PubMed

Pais-Morales, Jonnatan; Betanzos, Abigail; García-Rivera, Guillermina; Chávez-Munguía, Bibiana; Shibayama, Mineko; Orozco, Esther

2016-01-01

Entamoeba histolytica causes amoebiasis, an infection that kills 100,000 individuals each year. Metronidazole and its derivatives are currently used against this protozoan, but these drugs present adverse effects on human health. Here, we investigated the effect of resveratrol (a natural compound) on E. histolytica trophozoites viability, as well as its influence on the parasite virulence. Trophozoites growth was arrested by 72 μM resveratrol and the IC50 was determined as 220 μM at 48 h. Cells appeared smaller, rounded and in clusters, with debris-containing vacuoles and with abnormally condensed chromatin. Resveratrol triggered reactive oxygen species production. It caused lipid peroxidation and produced phosphatidylserine externalization and DNA fragmentation this latter evidenced by TUNEL assays. It also provoked an increase of intracellular Ca2+ concentration, activated calpain and decreased superoxide dismutase activity, indicating that an apoptosis-like event occurred; however, autophagy was not detected. Cytopathic activity, phagocytosis, encystment and in vivo virulence were diminished dramatically by pre-incubation of trophozoites with resveratrol, evidencing that resveratrol attenuated the trophozoite virulence in vitro. Interestingly, after the inoculation of virulent trophozoites, animals treated with the drug did not develop or developed very small abscesses. Our findings propose that resveratrol could be an alternative to contend amoebiasis.

Siderophore biosynthesis coordinately modulated the virulence-associated interactive metabolome of uropathogenic Escherichia coli and human urine

PubMed Central

Su, Qiao; Guan, Tianbing; Lv, Haitao

2016-01-01

Uropathogenic Escherichia coli (UPEC) growth in women’s bladders during urinary tract infection (UTI) incurs substantial chemical exchange, termed the “interactive metabolome”, which primarily accounts for the metabolic costs (utilized metabolome) and metabolic donations (excreted metabolome) between UPEC and human urine. Here, we attempted to identify the individualized interactive metabolome between UPEC and human urine. We were able to distinguish UPEC from non-UPEC by employing a combination of metabolomics and genetics. Our results revealed that the interactive metabolome between UPEC and human urine was markedly different from that between non-UPEC and human urine, and that UPEC triggered much stronger perturbations in the interactive metabolome in human urine. Furthermore, siderophore biosynthesis coordinately modulated the individualized interactive metabolome, which we found to be a critical component of UPEC virulence. The individualized virulence-associated interactive metabolome contained 31 different metabolites and 17 central metabolic pathways that were annotated to host these different metabolites, including energetic metabolism, amino acid metabolism, and gut microbe metabolism. Changes in the activities of these pathways mechanistically pinpointed the virulent capability of siderophore biosynthesis. Together, our findings provide novel insights into UPEC virulence, and we propose that siderophores are potential targets for further discovery of drugs to treat UPEC-induced UTI. PMID:27076285

Siderophore biosynthesis coordinately modulated the virulence-associated interactive metabolome of uropathogenic Escherichia coli and human urine.

PubMed

Su, Qiao; Guan, Tianbing; Lv, Haitao

2016-04-14

Uropathogenic Escherichia coli (UPEC) growth in women's bladders during urinary tract infection (UTI) incurs substantial chemical exchange, termed the "interactive metabolome", which primarily accounts for the metabolic costs (utilized metabolome) and metabolic donations (excreted metabolome) between UPEC and human urine. Here, we attempted to identify the individualized interactive metabolome between UPEC and human urine. We were able to distinguish UPEC from non-UPEC by employing a combination of metabolomics and genetics. Our results revealed that the interactive metabolome between UPEC and human urine was markedly different from that between non-UPEC and human urine, and that UPEC triggered much stronger perturbations in the interactive metabolome in human urine. Furthermore, siderophore biosynthesis coordinately modulated the individualized interactive metabolome, which we found to be a critical component of UPEC virulence. The individualized virulence-associated interactive metabolome contained 31 different metabolites and 17 central metabolic pathways that were annotated to host these different metabolites, including energetic metabolism, amino acid metabolism, and gut microbe metabolism. Changes in the activities of these pathways mechanistically pinpointed the virulent capability of siderophore biosynthesis. Together, our findings provide novel insights into UPEC virulence, and we propose that siderophores are potential targets for further discovery of drugs to treat UPEC-induced UTI.

Resveratrol Induces Apoptosis-Like Death and Prevents In Vitro and In Vivo Virulence of Entamoeba histolytica

PubMed Central

Pais-Morales, Jonnatan; Betanzos, Abigail; García-Rivera, Guillermina; Chávez-Munguía, Bibiana; Shibayama, Mineko; Orozco, Esther

2016-01-01

Entamoeba histolytica causes amoebiasis, an infection that kills 100,000 individuals each year. Metronidazole and its derivatives are currently used against this protozoan, but these drugs present adverse effects on human health. Here, we investigated the effect of resveratrol (a natural compound) on E. histolytica trophozoites viability, as well as its influence on the parasite virulence. Trophozoites growth was arrested by 72 μM resveratrol and the IC50 was determined as 220 μM at 48 h. Cells appeared smaller, rounded and in clusters, with debris-containing vacuoles and with abnormally condensed chromatin. Resveratrol triggered reactive oxygen species production. It caused lipid peroxidation and produced phosphatidylserine externalization and DNA fragmentation this latter evidenced by TUNEL assays. It also provoked an increase of intracellular Ca2+ concentration, activated calpain and decreased superoxide dismutase activity, indicating that an apoptosis-like event occurred; however, autophagy was not detected. Cytopathic activity, phagocytosis, encystment and in vivo virulence were diminished dramatically by pre-incubation of trophozoites with resveratrol, evidencing that resveratrol attenuated the trophozoite virulence in vitro. Interestingly, after the inoculation of virulent trophozoites, animals treated with the drug did not develop or developed very small abscesses. Our findings propose that resveratrol could be an alternative to contend amoebiasis. PMID:26731663

Evaluation of phytochemicals from medicinal plants of Myrtaceae family on virulence factor production by Pseudomonas aeruginosa.

PubMed

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.

Urinary tract infectivity or R strains of Escherichia coli carrying various virulence factors.

PubMed

Kétyi, I; Naumann, G; Nimmich, W

1983-01-01

The virulence factors of Escherichia coli supposed to act in urinary tract infections were studied on R strains in a suckling mouse model. The production of alpha-(diffusible-) haemolysin or the possession of antigen K1 enhanced the virulence significantly, while the type 1 (common) fimbriae failed to do so. An isogenic motile and non-motile pair of E. coli did not show any difference in infectivity in the model. The adhesins, the diffusible haemolysin, and the acidic polysaccharide K antigens (K1) are definitely additive virulence factors in the model. This is in good agreement with the experience of clinical bacteriology.

Correlates of virulence in a frog-killing fungal pathogen: evidence from a California amphibian decline

Treesearch

Jonah Piovia-Scott; Karen Pope; S. Joy Worth; Erica Bree Rosenblum; Dean Simon; Gordon Warburton; Louise A. Rollins-Smith; Laura K. Reinert; Heather L. Wells; Dan Rejmanek; Sharon Lawler; Janet Foley

2015-01-01

The fungal pathogen Batrachochytrium dendrobatidis (Bd) has caused declines and extinctions in amphibians worldwide, and there is increasing evidence that some strains of this pathogen are more virulent than others. While a number of putative virulence factors have been identified, few studies link these factors to specific epizootic events. We...

Iron uptake controls the generation of Leishmania infective forms through regulation of ROS levels

PubMed Central

Mittra, Bidyottam; Cortez, Mauro; Haydock, Andrew; Ramasamy, Gowthaman; Myler, Peter J.

2013-01-01

During its life cycle, Leishmania undergoes extreme environmental changes, alternating between insect vectors and vertebrate hosts. Elevated temperature and decreased pH, conditions encountered after macrophage invasion, can induce axenic differentiation of avirulent promastigotes into virulent amastigotes. Here we show that iron uptake is a major trigger for the differentiation of Leishmania amazonensis amastigotes, independently of temperature and pH changes. We found that iron depletion from the culture medium triggered expression of the ferrous iron transporter LIT1 (Leishmania iron transporter 1), an increase in iron content of the parasites, growth arrest, and differentiation of wild-type (WT) promastigotes into infective amastigotes. In contrast, LIT1-null promastigotes showed reduced intracellular iron content and sustained growth in iron-poor media, followed by cell death. LIT1 up-regulation also increased iron superoxide dismutase (FeSOD) activity in WT but not in LIT1-null parasites. Notably, the superoxide-generating drug menadione or H2O2 was sufficient to trigger differentiation of WT promastigotes into fully infective amastigotes. LIT1-null promastigotes accumulated superoxide radicals and initiated amastigote differentiation after exposure to H2O2 but not to menadione. Our results reveal a novel role for FeSOD activity and reactive oxygen species in orchestrating the differentiation of virulent Leishmania amastigotes in a process regulated by iron availability. PMID:23382545

Cyclo(valine-valine) inhibits Vibrio cholerae virulence gene expression.

PubMed

Vikram, Amit; Ante, Vanessa M; Bina, X Renee; Zhu, Qin; Liu, Xinyu; Bina, James E

2014-06-01

Vibrio cholerae has been shown to produce a cyclic dipeptide, cyclo(phenylalanine-proline) (cFP), that functions to repress virulence factor production. The objective of this study was to determine if heterologous cyclic dipeptides could repress V. cholerae virulence factor production. To that end, three synthetic cyclic dipeptides that differed in their side chains from cFP were assayed for virulence inhibitory activity in V. cholerae. The results revealed that cyclo(valine-valine) (cVV) inhibited virulence factor production by a ToxR-dependent process that resulted in the repression of the virulence regulator aphA. cVV-dependent repression of aphA was found to be independent of known aphA regulatory genes. The results demonstrated that V. cholerae was able to respond to exogenous cyclic dipeptides and implicated the hydrophobic amino acid side chains on both arms of the cyclo dipeptide scaffold as structural requirements for inhibitory activity. The results further suggest that cyclic dipeptides have potential as therapeutics for cholera treatment. © 2014 The Authors.

Limiting opportunities for cheating stabilizes virulence in insect parasitic nematodes.

PubMed

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.

Cell Density Control of Staphylococcal Virulence Mediated by an Octapeptide Pheromone

NASA Astrophysics Data System (ADS)

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.

PSTha5a23, a candidate effector from the obligate biotrophic pathogen Puccinia striiformis f. sp. tritici, is involved in plant defense suppression and rust pathogenicity.

PubMed

Cheng, Yulin; Wu, Kuan; Yao, Juanni; Li, Shumin; Wang, Xiaojie; Huang, Lili; Kang, Zhensheng

2017-05-01

During the infection of host plants, pathogens can deliver virulence-associated 'effector' proteins to promote plant susceptibility. However, little is known about effector function in the obligate biotrophic pathogen Puccinia striiformis f. sp. tritici (Pst) that is an important fungal pathogen in wheat production worldwide. Here, they report their findings on an in planta highly induced candidate effector from Pst, PSTha5a23. The PSTha5a23 gene is unique to Pst and shows a low level of intra-species polymorphism. It has a functional N-terminal signal peptide and is translocated to the host cytoplasm after infection. Overexpression of PSTha5a23 in Nicotiana benthamiana was found to suppress the programmed cell death triggered by BAX, PAMP-INF1 and two resistance-related mitogen-activated protein kinases (MKK1 and NPK1). Overexpression of PSTha5a23 in wheat also suppressed pattern-triggered immunity (PTI)-associated callose deposition. In addition, silencing of PSTha5a23 did not change Pst virulence phenotypes; however, overexpression of PSTha5a23 significantly enhanced Pst virulence in wheat. These results indicate that the Pst candidate effector PSTha5a23 plays an important role in plant defense suppression and rust pathogenicity, and also highlight the utility of gene overexpression in plants as a tool for studying effectors from obligate biotrophic pathogens. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

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

PubMed

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.

Virulence and Immunomodulatory Roles of Bacterial Outer Membrane Vesicles

PubMed Central

Ellis, Terri N.; Kuehn, Meta J.

2010-01-01

Summary: Outer membrane (OM) vesicles are ubiquitously produced by Gram-negative bacteria during all stages of bacterial growth. OM vesicles are naturally secreted by both pathogenic and nonpathogenic bacteria. Strong experimental evidence exists to categorize OM vesicle production as a type of Gram-negative bacterial virulence factor. A growing body of data demonstrates an association of active virulence factors and toxins with vesicles, suggesting that they play a role in pathogenesis. One of the most popular and best-studied pathogenic functions for membrane vesicles is to serve as natural vehicles for the intercellular transport of virulence factors and other materials directly into host cells. The production of OM vesicles has been identified as an independent bacterial stress response pathway that is activated when bacteria encounter environmental stress, such as what might be experienced during the colonization of host tissues. Their detection in infected human tissues reinforces this theory. Various other virulence factors are also associated with OM vesicles, including adhesins and degradative enzymes. As a result, OM vesicles are heavily laden with pathogen-associated molecular patterns (PAMPs), virulence factors, and other OM components that can impact the course of infection by having toxigenic effects or by the activation of the innate immune response. However, infected hosts can also benefit from OM vesicle production by stimulating their ability to mount an effective defense. Vesicles display antigens and can elicit potent inflammatory and immune responses. In sum, OM vesicles are likely to play a significant role in the virulence of Gram-negative bacterial pathogens. PMID:20197500

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

PubMed

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.

Intensive fish farming and the evolution of pathogen virulence: the case of columnaris disease in Finland

PubMed Central

Pulkkinen, K.; Suomalainen, L.-R.; Read, A. F.; Ebert, D.; Rintamäki, P.; Valtonen, E. T.

2010-01-01

Ecological changes affect pathogen epidemiology and evolution and may trigger the emergence of novel diseases. Aquaculture radically alters the ecology of fish and their pathogens. Here we show an increase in the occurrence of the bacterial fish disease Flavobacterium columnare in salmon fingerlings at a fish farm in northern Finland over 23 years. We hypothesize that this emergence was owing to evolutionary changes in bacterial virulence. We base this argument on several observations. First, the emergence was associated with increased severity of symptoms. Second, F. columnare strains vary in virulence, with more lethal strains inducing more severe symptoms prior to death. Third, more virulent strains have greater infectivity, higher tissue-degrading capacity and higher growth rates. Fourth, pathogen strains co-occur, so that strains compete. Fifth, F. columnare can transmit efficiently from dead fish, and maintain infectivity in sterilized water for months, strongly reducing the fitness cost of host death likely experienced by the pathogen in nature. Moreover, this saprophytic infectiousness means that chemotherapy strongly select for strains that rapidly kill their hosts: dead fish remain infectious; treated fish do not. Finally, high stocking densities of homogeneous subsets of fish greatly enhance transmission opportunities. We suggest that fish farms provide an environment that promotes the circulation of more virulent strains of F. columnare. This effect is intensified by the recent increases in summer water temperature. More generally, we predict that intensive fish farming will lead to the evolution of more virulent pathogens. PMID:19864284

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

PubMed

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 speculated that pathogenicity of Pe was more similar to high virulence Pg than that to low virulence strain.

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

PubMed

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.

Streptolysin S-like virulence factors: the continuing sagA

PubMed Central

Molloy, Evelyn M.; Cotter, Paul D.; Hill, Colin; Mitchell, Douglas A.; Ross, R. Paul

2014-01-01

Streptolysin S (SLS) is a potent cytolytic toxin and virulence factor produced by nearly all Streptococcus pyogenes strains. Despite a 100-year history of research on this toxin, it has only recently been established that SLS represents the archetypal example of an extended family of post-translationally modified virulence factors also produced by some other streptococci and Gram-positive pathogens, such as Listeria monocytogenes and Clostridium botulinum. In this Review we describe the identification, genetics, biochemistry and various functions of SLS. We also discuss the shared features of the virulence-associated SLS-like peptides, as well as their place within the rapidly expanding family of thiazole/oxazole-modified microcins (TOMMs). PMID:21822292

Melanization and Pathogenicity in the Insect, Tenebrio molitor, and the Crustacean, Pacifastacus leniusculus, by Aeromonas hydrophila AH-3

PubMed Central

Noonin, Chadanat; Jiravanichpaisal, Pikul; Söderhäll, Irene; Merino, Susana; Tomás, Juan M.; Söderhäll, Kenneth

2010-01-01

Aeromonas hydrophila is the most common Aeromonas species causing infections in human and other animals such as amphibians, reptiles, fish and crustaceans. Pathogenesis of Aeromonas species have been reported to be associated with virulence factors such as lipopolysaccharides (LPS), bacterial toxins, bacterial secretion systems, flagella, and other surface molecules. Several mutant strains of A. hydrophila AH-3 were initially used to study their virulence in two animal species, Pacifastacus leniusculus (crayfish) and Tenebrio molitor larvae (mealworm). The AH-3 strains used in this study have mutations in genes involving the synthesis of flagella, LPS structures, secretion systems, and some other factors, which have been reported to be involved in A. hydrophila pathogenicity. Our study shows that the LPS (O-antigen and external core) is the most determinant A. hydrophila AH-3 virulence factor in both animals. Furthermore, we studied the immune responses of these hosts to infection of virulent or non-virulent strains of A. hydrophila AH-3. The AH-3 wild type (WT) containing the complete LPS core is highly virulent and this bacterium strongly stimulated the prophenoloxidase activating system resulting in melanization in both crayfish and mealworm. In contrast, the ΔwaaE mutant which has LPS without O-antigen and external core was non-virulent and lost ability to stimulate this system and melanization in these two animals. The high phenoloxidase activity found in WT infected crayfish appears to result from a low expression of pacifastin, a prophenoloxidase activating enzyme inhibitor, and this gene expression was not changed in the ΔwaaE mutant infected animal and consequently phenoloxidase activity was not altered as compared to non-infected animals. Therefore we show that the virulence factors of A. hydrophila are the same regardless whether an insect or a crustacean is infected and the O-antigen and external core is essential for activation of the proPO system and as virulence factors for this bacterium. PMID:21206752

Cell wall-degrading enzymes of Didymella bryoniae in relation to fungal growth and virulence in cantaloupe fruit

PubMed Central

Zhang, J.; Bruton, B. D.; Biles, C. L.

2014-01-01

Didymella bryoniae is an important pathogen of cucurbits worldwide. Virulence factors of D. bryoniae were investigated in regard to fungal growth and the production of cell wall-degrading enzymes, polygalacturonase (PG), pectate lyase (PL), pectin lyase (PNL), β-galactosidase (β-Gal) and cellulase (Cx). Virulence levels of five D. bryoniae isolates were determined by the severity of inoculated cantaloupe fruit decay. The highly virulent isolates had more mycelial growth than the moderately virulent isolates in different media. PG activities produced by the highly virulent isolates in shake cultures and in decayed fruit were greater than those of the moderately virulent isolates. PNL, but not PL, in decayed fruit was higher with the highly virulent isolates compared to the moderately virulent ones. The highly virulent isolates showed higher Cx activity than the moderately virulent ones in decayed fruit and in fruit tissue shake culture. β-Gal activities of the highly virulent isolates in pectin shake culture and in decayed fruit were greater than those of the two moderately virulent isolates although fruit also produced β-Gal. Protein analysis showed two fungal β-Gal isozymes in decayed fruit compared to those of healthy fruit. Correlation analysis indicated that the activities of PG, PNL, β-Gal and Cx in cultures and in decayed fruit positively correlated with fungal growth and fruit decay severity. The results of this study suggest that PG, PNL, β-Gal, and Cx appear to be virulence factors of D. bryoniae in cantaloupe decay with PG and β-Gal as the most predominant fruit decay enzymes. PMID:25364138

Secreted bacterial effectors that inhibit host protein synthesis are critical for induction of the innate immune response to virulent Legionella pneumophila.

PubMed

Fontana, Mary F; Banga, Simran; Barry, Kevin C; Shen, Xihui; Tan, Yunhao; Luo, Zhao-Qing; Vance, Russell E

2011-02-01

The intracellular bacterial pathogen Legionella pneumophila causes an inflammatory pneumonia called Legionnaires' Disease. For virulence, L. pneumophila requires a Dot/Icm type IV secretion system that translocates bacterial effectors to the host cytosol. L. pneumophila lacking the Dot/Icm system is recognized by Toll-like receptors (TLRs), leading to a canonical NF-κB-dependent transcriptional response. In addition, L. pneumophila expressing a functional Dot/Icm system potently induces unique transcriptional targets, including proinflammatory genes such as Il23a and Csf2. Here we demonstrate that this Dot/Icm-dependent response, which we term the effector-triggered response (ETR), requires five translocated bacterial effectors that inhibit host protein synthesis. Upon infection of macrophages with virulent L. pneumophila, these five effectors caused a global decrease in host translation, thereby preventing synthesis of IκB, an inhibitor of the NF-κB transcription factor. Thus, macrophages infected with wildtype L. pneumophila exhibited prolonged activation of NF-κB, which was associated with transcription of ETR target genes such as Il23a and Csf2. L. pneumophila mutants lacking the five effectors still activated TLRs and NF-κB, but because the mutants permitted normal IκB synthesis, NF-κB activation was more transient and was not sufficient to fully induce the ETR. L. pneumophila mutants expressing enzymatically inactive effectors were also unable to fully induce the ETR, whereas multiple compounds or bacterial toxins that inhibit host protein synthesis via distinct mechanisms recapitulated the ETR when administered with TLR ligands. Previous studies have demonstrated that the host response to bacterial infection is induced primarily by specific microbial molecules that activate TLRs or cytosolic pattern recognition receptors. Our results add to this model by providing a striking illustration of how the host immune response to a virulent pathogen can also be shaped by pathogen-encoded activities, such as inhibition of host protein synthesis.

Molecular evolution of an Avirulence Homolog (Avh) gene subfamily in Phytophthora ramorum

Treesearch

GossErica M.; Caroline M. Press; Niklaus J. Grünwald

2008-01-01

Pathogen effectors can serve a virulence function on behalf of the pathogen or trigger a rapid defense response in resistant hosts. Sequencing of the Phytophthora ramorum genome and subsequent analysis identified a diverse superfamily of approximately 350 genes that are homologous to the four known avirulence genes in plant pathogenic oomycetes and...

Die another day: molecular mechanisms of effector-triggered immunity elicited by type III secreted effector proteins

USDA-ARS?s Scientific Manuscript database

Bacterial pathogens inject type III secreted effector (T3SE) proteins into their hosts where they display dual roles depending on the host genotype. T3SEs promote bacterial virulence in susceptible hosts, and elicit immunity in resistant hosts. T3SEs are typically recognized when they modify a host ...

Common themes in microbial pathogenicity revisited.

PubMed Central

Finlay, B B; Falkow, S

1997-01-01

Bacterial pathogens employ a number of genetic strategies to cause infection and, occasionally, disease in their hosts. Many of these virulence factors and their regulatory elements can be divided into a smaller number of groups based on the conservation of similar mechanisms. These common themes are found throughout bacterial virulence factors. For example, there are only a few general types of toxins, despite a large number of host targets. Similarly, there are only a few conserved ways to build the bacterial pilus and nonpilus adhesins used by pathogens to adhere to host substrates. Bacterial entry into host cells (invasion) is a complex mechanism. However, several common invasion themes exist in diverse microorganisms. Similarly, once inside a host cell, pathogens have a limited number of ways to ensure their survival, whether remaining within a host vacuole or by escaping into the cytoplasm. Avoidance of the host immune defenses is key to the success of a pathogen. Several common themes again are employed, including antigenic variation, camouflage by binding host molecules, and enzymatic degradation of host immune components. Most virulence factors are found on the bacterial surface or secreted into their immediate environment, yet virulence factors operate through a relatively small number of microbial secretion systems. The expression of bacterial pathogenicity is dependent upon complex regulatory circuits. However, pathogens use only a small number of biochemical families to express distinct functional factors at the appropriate time that causes infection. Finally, virulence factors maintained on mobile genetic elements and pathogenicity islands ensure that new strains of pathogens evolve constantly. Comprehension of these common themes in microbial pathogenicity is critical to the understanding and study of bacterial virulence mechanisms and to the development of new "anti-virulence" agents, which are so desperately needed to replace antibiotics. PMID:9184008

Dynamics of Escherichia coli Virulence Factors in Dairy Herds and Farm Environments in a Longitudinal Study in the United States

PubMed Central

Lambertini, Elisabetta; Karns, Jeffrey S.; Van Kessel, Jo Ann S.; Cao, Huilin; Schukken, Ynte H.; Wolfgang, David R.; Smith, Julia M.

2015-01-01

Pathogenic Escherichia coli or its associated virulence factors have been frequently detected in dairy cow manure, milk, and dairy farm environments. However, it is unclear what the long-term dynamics of E. coli virulence factors are and which farm compartments act as reservoirs. This study assessed the occurrence and dynamics of four E. coli virulence factors (eae, stx1, stx2, and the gamma allele of the tir gene [γ-tir]) on three U.S. dairy farms. Fecal, manure, water, feed, milk, and milk filter samples were collected from 2004 to 2012. Virulence factors were measured by postenrichment quantitative PCR (qPCR). All factors were detected in most compartments on all farms. Fecal and manure samples showed the highest prevalence, up to 53% for stx and 21% for γ-tir in fecal samples and up to 84% for stx and 44% for γ-tir in manure. Prevalence was low in milk (up to 1.9% for stx and 0.7% for γ-tir). However, 35% of milk filters were positive for stx and 20% were positive for γ-tir. All factors were detected in feed and water. Factor prevalence and levels, expressed as qPCR cycle threshold categories, fluctuated significantly over time, with no clear seasonal signal independent from year-to-year variability. Levels were correlated between fecal and manure samples, and in some cases autocorrelated, but not between manure and milk filters. Shiga toxins were nearly ubiquitous, and 10 to 18% of the lactating cows were potential shedders of E. coli O157 at least once during their time in the herds. E. coli virulence factors appear to persist in many areas of the farms and therefore contribute to transmission dynamics. PMID:25911478

The Genome of a Pathogenic Rhodococcus: Cooptive Virulence Underpinned by Key Gene Acquisitions

PubMed Central

Letek, Michal; González, Patricia; MacArthur, Iain; Rodríguez, Héctor; Freeman, Tom C.; Valero-Rello, Ana; Blanco, Mónica; Buckley, Tom; Cherevach, Inna; Fahey, Ruth; Hapeshi, Alexia; Holdstock, Jolyon; Leadon, Desmond; Navas, Jesús; Ocampo, Alain; Quail, Michael A.; Sanders, Mandy; Scortti, Mariela M.; Prescott, John F.; Fogarty, Ursula; Meijer, Wim G.; Parkhill, Julian; Bentley, Stephen D.; Vázquez-Boland, José A.

2010-01-01

We report the genome of the facultative intracellular parasite Rhodococcus equi, the only animal pathogen within the biotechnologically important actinobacterial genus Rhodococcus. The 5.0-Mb R. equi 103S genome is significantly smaller than those of environmental rhodococci. This is due to genome expansion in nonpathogenic species, via a linear gain of paralogous genes and an accelerated genetic flux, rather than reductive evolution in R. equi. The 103S genome lacks the extensive catabolic and secondary metabolic complement of environmental rhodococci, and it displays unique adaptations for host colonization and competition in the short-chain fatty acid–rich intestine and manure of herbivores—two main R. equi reservoirs. Except for a few horizontally acquired (HGT) pathogenicity loci, including a cytoadhesive pilus determinant (rpl) and the virulence plasmid vap pathogenicity island (PAI) required for intramacrophage survival, most of the potential virulence-associated genes identified in R. equi are conserved in environmental rhodococci or have homologs in nonpathogenic Actinobacteria. This suggests a mechanism of virulence evolution based on the cooption of existing core actinobacterial traits, triggered by key host niche–adaptive HGT events. We tested this hypothesis by investigating R. equi virulence plasmid-chromosome crosstalk, by global transcription profiling and expression network analysis. Two chromosomal genes conserved in environmental rhodococci, encoding putative chorismate mutase and anthranilate synthase enzymes involved in aromatic amino acid biosynthesis, were strongly coregulated with vap PAI virulence genes and required for optimal proliferation in macrophages. The regulatory integration of chromosomal metabolic genes under the control of the HGT–acquired plasmid PAI is thus an important element in the cooptive virulence of R. equi. PMID:20941392

Role of dupA in virulence of Helicobacter pylori

PubMed Central

Talebi Bezmin Abadi, Amin; Perez-Perez, Guillermo

2016-01-01

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. PMID:28028359

Role of dupA in virulence of Helicobacter pylori.

PubMed

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.

Virulence of Pseudomonas syringae pv. tomato DC3000 Is Influenced by the Catabolite Repression Control Protein Crc.

PubMed

Chakravarthy, Suma; Butcher, Bronwyn G; Liu, Yingyu; D'Amico, Katherine; Coster, Matthew; Filiatrault, Melanie J

2017-04-01

Pseudomonas syringae infects diverse plant species and is widely used as a model system in the study of effector function and the molecular basis of plant diseases. Although the relationship between bacterial metabolism, nutrient acquisition, and virulence has attracted increasing attention in bacterial pathology, it is largely unexplored in P. syringae. The Crc (catabolite repression control) protein is a putative RNA-binding protein that regulates carbon metabolism as well as a number of other factors in the pseudomonads. Here, we show that deletion of crc increased bacterial swarming motility and biofilm formation. The crc mutant showed reduced growth and symptoms in Arabidopsis and tomato when compared with the wild-type strain. We have evidence that the crc mutant shows delayed hypersensitive response (HR) when infiltrated into Nicotiana benthamiana and tobacco. Interestingly, the crc mutant was more susceptible to hydrogen peroxide, suggesting that, in planta, the mutant may be sensitive to reactive oxygen species generated during pathogen-associated molecular pattern-triggered immunity (PTI). Indeed, HR was further delayed when PTI-induced tissues were challenged with the crc mutant. The crc mutant did not elicit an altered PTI response in plants compared with the wild-type strain. We conclude that Crc plays an important role in growth and survival during infection.

Atmospheric CO2 Alters Resistance of Arabidopsis to Pseudomonas syringae by Affecting Abscisic Acid Accumulation and Stomatal Responsiveness to Coronatine

PubMed Central

Zhou, Yeling; Vroegop-Vos, Irene; Schuurink, Robert C.; Pieterse, Corné M. J.; Van Wees, Saskia C. M.

2017-01-01

Atmospheric CO2 influences plant growth and stomatal aperture. Effects of high or low CO2 levels on plant disease resistance are less well understood. Here, resistance of Arabidopsis thaliana against the foliar pathogen Pseudomonas syringae pv. tomato DC3000 (Pst) was investigated at three different CO2 levels: high (800 ppm), ambient (450 ppm), and low (150 ppm). Under all conditions tested, infection by Pst resulted in stomatal closure within 1 h after inoculation. However, subsequent stomatal reopening at 4 h, triggered by the virulence factor coronatine (COR), occurred only at ambient and high CO2, but not at low CO2. Moreover, infection by Pst was reduced at low CO2 to the same extent as infection by mutant Pst cor-. Under all CO2 conditions, the ABA mutants aba2-1 and abi1-1 were as resistant to Pst as wild-type plants under low CO2, which contained less ABA. Moreover, stomatal reopening mediated by COR was dependent on ABA. Our results suggest that reduced ABA levels at low CO2 contribute to the observed enhanced resistance to Pst by deregulation of virulence responses. This implies that enhanced ABA levels at increasing CO2 levels may have a role in weakening plant defense. PMID:28559899

Complete genome sequencing and analysis of a Lancefield group G Streptococcus dysgalactiae subsp. equisimilis strain causing streptococcal toxic shock syndrome (STSS)

PubMed Central

2011-01-01

Background Streptococcus dysgalactiae subsp. equisimilis (SDSE) causes invasive streptococcal infections, including streptococcal toxic shock syndrome (STSS), as does Lancefield group A Streptococcus pyogenes (GAS). We sequenced the entire genome of SDSE strain GGS_124 isolated from a patient with STSS. Results We found that GGS_124 consisted of a circular genome of 2,106,340 bp. Comparative analyses among bacterial genomes indicated that GGS_124 was most closely related to GAS. GGS_124 and GAS, but not other streptococci, shared a number of virulence factor genes, including genes encoding streptolysin O, NADase, and streptokinase A, distantly related to SIC (DRS), suggesting the importance of these factors in the development of invasive disease. GGS_124 contained 3 prophages, with one containing a virulence factor gene for streptodornase. All 3 prophages were significantly similar to GAS prophages that carry virulence factor genes, indicating that these prophages had transferred these genes between pathogens. SDSE was found to contain a gene encoding a superantigen, streptococcal exotoxin type G, but lacked several genes present in GAS that encode virulence factors, such as other superantigens, cysteine protease speB, and hyaluronan synthase operon hasABC. Similar to GGS_124, the SDSE strains contained larger numbers of clustered, regularly interspaced, short palindromic repeats (CRISPR) spacers than did GAS, suggesting that horizontal gene transfer via streptococcal phages between SDSE and GAS is somewhat restricted, although they share phage species. Conclusion Genome wide comparisons of SDSE with GAS indicate that SDSE is closely and quantitatively related to GAS. SDSE, however, lacks several virulence factors of GAS, including superantigens, SPE-B and the hasABC operon. CRISPR spacers may limit the horizontal transfer of phage encoded GAS virulence genes into SDSE. These findings may provide clues for dissecting the pathological roles of the virulence factors in SDSE and GAS that cause STSS. PMID:21223537

Complete genome sequencing and analysis of a Lancefield group G Streptococcus dysgalactiae subsp. equisimilis strain causing streptococcal toxic shock syndrome (STSS).

PubMed

Shimomura, Yumi; Okumura, Kayo; Murayama, Somay Yamagata; Yagi, Junji; Ubukata, Kimiko; Kirikae, Teruo; Miyoshi-Akiyama, Tohru

2011-01-11

Streptococcus dysgalactiae subsp. equisimilis (SDSE) causes invasive streptococcal infections, including streptococcal toxic shock syndrome (STSS), as does Lancefield group A Streptococcus pyogenes (GAS). We sequenced the entire genome of SDSE strain GGS_124 isolated from a patient with STSS. We found that GGS_124 consisted of a circular genome of 2,106,340 bp. Comparative analyses among bacterial genomes indicated that GGS_124 was most closely related to GAS. GGS_124 and GAS, but not other streptococci, shared a number of virulence factor genes, including genes encoding streptolysin O, NADase, and streptokinase A, distantly related to SIC (DRS), suggesting the importance of these factors in the development of invasive disease. GGS_124 contained 3 prophages, with one containing a virulence factor gene for streptodornase. All 3 prophages were significantly similar to GAS prophages that carry virulence factor genes, indicating that these prophages had transferred these genes between pathogens. SDSE was found to contain a gene encoding a superantigen, streptococcal exotoxin type G, but lacked several genes present in GAS that encode virulence factors, such as other superantigens, cysteine protease speB, and hyaluronan synthase operon hasABC. Similar to GGS_124, the SDSE strains contained larger numbers of clustered, regularly interspaced, short palindromic repeats (CRISPR) spacers than did GAS, suggesting that horizontal gene transfer via streptococcal phages between SDSE and GAS is somewhat restricted, although they share phage species. Genome wide comparisons of SDSE with GAS indicate that SDSE is closely and quantitatively related to GAS. SDSE, however, lacks several virulence factors of GAS, including superantigens, SPE-B and the hasABC operon. CRISPR spacers may limit the horizontal transfer of phage encoded GAS virulence genes into SDSE. These findings may provide clues for dissecting the pathological roles of the virulence factors in SDSE and GAS that cause STSS.

ε/ζ systems: their role in resistance, virulence, and their potential for antibiotic development.

PubMed

Mutschler, Hannes; Meinhart, Anton

2011-12-01

Cell death in bacteria can be triggered by activation of self-inflicted molecular mechanisms. Pathogenic bacteria often make use of suicide mechanisms in which the death of individual cells benefits survival of the population. Important elements for programmed cell death in bacteria are proteinaceous toxin-antitoxin systems. While the toxin generally resides dormant in the bacterial cytosol in complex with its antitoxin, conditions such as impaired de novo synthesis of the antitoxin or nutritional stress lead to antitoxin degradation and toxin activation. A widespread toxin-antitoxin family consists of the ε/ζ systems, which are distributed over plasmids and chromosomes of various pathogenic bacteria. In its inactive state, the bacteriotoxic ζ toxin protein is inhibited by its cognate antitoxin ε. Upon degradation of ε, the ζ toxin is released allowing this enzyme to poison bacterial cell wall synthesis, which eventually triggers autolysis. ε/ζ systems ensure stable plasmid inheritance by inducing death in plasmid-deprived offspring cells. In contrast, chromosomally encoded ε/ζ systems were reported to contribute to virulence of pathogenic bacteria, possibly by inducing autolysis in individual cells under stressful conditions. The capability of toxin-antitoxin systems to kill bacteria has made them potential targets for new therapeutic compounds. Toxin activation could be hijacked to induce suicide of bacteria. Likewise, the unique mechanism of ζ toxins could serve as template for new drugs. Contrarily, inhibition of virulence-associated ζ toxins might attenuate infections. Here we provide an overview of ε/ζ toxin-antitoxin family and its potential role in the development of new therapeutic approaches in microbial defense.

Phytoplasma-conserved phyllogen proteins induce phyllody across the Plantae by degrading floral MADS domain proteins.

PubMed

Kitazawa, Yugo; Iwabuchi, Nozomu; Himeno, Misako; Sasano, Momoka; Koinuma, Hiroaki; Nijo, Takamichi; Tomomitsu, Tatsuya; Yoshida, Tetsuya; Okano, Yukari; Yoshikawa, Nobuyuki; Maejima, Kensaku; Oshima, Kenro; Namba, Shigetou

2017-05-17

ABCE-class MADS domain transcription factors (MTFs) are key regulators of floral organ development in angiosperms. Aberrant expression of these genes can result in abnormal floral traits such as phyllody. Phyllogen is a virulence factor conserved in phytoplasmas, plant pathogenic bacteria of the class Mollicutes. It triggers phyllody in Arabidopsis thaliana by inducing degradation of A- and E-class MTFs. However, it is still unknown whether phyllogen can induce phyllody in plants other than A. thaliana, although phytoplasma-associated phyllody symptoms are observed in a broad range of angiosperms. In this study, phyllogen was shown to cause phyllody phenotypes in several eudicot species belonging to three different families. Moreover, phyllogen can interact with MTFs of not only angiosperm species including eudicots and monocots but also gymnosperms and a fern, and induce their degradation. These results suggest that phyllogen induces phyllody in angiosperms and inhibits MTF function in diverse plant species. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Molecular determinants for a cardiovascular collapse in anthrax

PubMed Central

Brojatsch, Jurgen; Casadevall, Arturo; Goldman, David L.

2015-01-01

Bacillus anthracis releases two bipartite proteins, lethal toxin and edema factor, that contribute significantly to the progression of anthrax-associated shock. As blocking the anthrax toxins prevents disease, the toxins are considered the main virulence factors of the bacterium. The anthrax bacterium and the anthrax toxins trigger multiorgan failure associated with enhanced vascular permeability, hemorrhage and cardiac dysfunction in animal challenge models. A recent study using mice that either lacked the anthrax toxin receptor in specific cells and corresponding mice expressing the receptor in specific cell types demonstrated that cardiovascular cells are critical for disease mediated by anthrax lethal toxin. These studies are consistent with involvement of the cardiovascular system, and with an increase of cardiac failure markers observed in human anthrax and in animal models using B. anthracis and anthrax toxins. This review discusses the current state of knowledge regarding the pathophysiology of anthrax and tries to provide a mechanistic model and molecular determinants for the circulatory shock in anthrax. PMID:24389148

New Aspects of RpoE in Uropathogenic Proteus mirabilis

PubMed Central

Liu, Ming-Che; Kuo, Kuan-Ting; Chien, Hsiung-Fei; Tsai, Yi-Lin

2014-01-01

Proteus mirabilis is a common human pathogen causing recurrent or persistent urinary tract infections (UTIs). The underlying mechanisms for P. mirabilis to establish UTIs are not fully elucidated. In this study, we showed that loss of the sigma factor E (RpoE), mediating extracytoplasmic stress responses, decreased fimbria expression, survival in macrophages, cell invasion, and colonization in mice but increased the interleukin-8 (IL-8) expression of urothelial cells and swarming motility. This is the first study to demonstrate that RpoE modulated expression of MR/P fimbriae by regulating mrpI, a gene encoding a recombinase controlling the orientation of MR/P fimbria promoter. By real-time reverse transcription-PCR, we found that the IL-8 mRNA amount of urothelial cells was induced significantly by lipopolysaccharides extracted from rpoE mutant but not from the wild type. These RpoE-associated virulence factors should be coordinately expressed to enhance the fitness of P. mirabilis in the host, including the avoidance of immune attacks. Accordingly, rpoE mutant-infected mice displayed more immune cell infiltration in bladders and kidneys during early stages of infection, and the rpoE mutant had a dramatically impaired ability of colonization. Moreover, it is noteworthy that urea (the major component in urine) and polymyxin B (a cationic antimicrobial peptide) can induce expression of rpoE by the reporter assay, suggesting that RpoE might be activated in the urinary tract. Altogether, our results indicate that RpoE is important in sensing environmental cues of the urinary tract and subsequently triggering the expression of virulence factors, which are associated with the fitness of P. mirabilis, to build up a UTI. PMID:25547796

New aspects of RpoE in uropathogenic Proteus mirabilis.

PubMed

Liu, Ming-Che; Kuo, Kuan-Ting; Chien, Hsiung-Fei; Tsai, Yi-Lin; Liaw, Shwu-Jen

2015-03-01

Proteus mirabilis is a common human pathogen causing recurrent or persistent urinary tract infections (UTIs). The underlying mechanisms for P. mirabilis to establish UTIs are not fully elucidated. In this study, we showed that loss of the sigma factor E (RpoE), mediating extracytoplasmic stress responses, decreased fimbria expression, survival in macrophages, cell invasion, and colonization in mice but increased the interleukin-8 (IL-8) expression of urothelial cells and swarming motility. This is the first study to demonstrate that RpoE modulated expression of MR/P fimbriae by regulating mrpI, a gene encoding a recombinase controlling the orientation of MR/P fimbria promoter. By real-time reverse transcription-PCR, we found that the IL-8 mRNA amount of urothelial cells was induced significantly by lipopolysaccharides extracted from rpoE mutant but not from the wild type. These RpoE-associated virulence factors should be coordinately expressed to enhance the fitness of P. mirabilis in the host, including the avoidance of immune attacks. Accordingly, rpoE mutant-infected mice displayed more immune cell infiltration in bladders and kidneys during early stages of infection, and the rpoE mutant had a dramatically impaired ability of colonization. Moreover, it is noteworthy that urea (the major component in urine) and polymyxin B (a cationic antimicrobial peptide) can induce expression of rpoE by the reporter assay, suggesting that RpoE might be activated in the urinary tract. Altogether, our results indicate that RpoE is important in sensing environmental cues of the urinary tract and subsequently triggering the expression of virulence factors, which are associated with the fitness of P. mirabilis, to build up a UTI. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Double-Edged Innovations: Preventing the Misuse of Emerging Biological/Chemical Technologies

DTIC Science & Technology

2010-07-01

1953 paper describing the double-helical structure of the DNA molecule and suggesting a mechanism for its replication. In 1973, Stanley Cohen of...Virology in early 2001. The security implications of the paper , however, triggered a storm of...unexpected findings of the mousepox experiment could have been predicted because a paper describing the role of interleukin-4 in poxvirus virulence

A novel, economical way to assess virulence in field populations of Hessian fly (Diptera: Cecidomyiidae) utilizing H13 as a model

USDA-ARS?s Scientific Manuscript database

Mayetiola destructor (Say) is a serious pest of wheat in the southeastern United States. The Hessian fly (Hf) uses effector triggered immunity to overcome wheat’s H genes, the resistance genes responsible for providing protection from the Hf. As the most effective form of Hf control employs the plan...

Transcriptional Basis of Drought-Induced Susceptibility to the Rice Blast Fungus Magnaporthe oryzae

PubMed Central

Bidzinski, Przemyslaw; Ballini, Elsa; Ducasse, Aurélie; Michel, Corinne; Zuluaga, Paola; Genga, Annamaria; Chiozzotto, Remo; Morel, Jean-Benoit

2016-01-01

Plants are often facing several stresses simultaneously. Understanding how they react and the way pathogens adapt to such combinational stresses is poorly documented. Here, we developed an experimental system mimicking field intermittent drought on rice followed by inoculation by the pathogenic fungus Magnaporthe oryzae. This experimental system triggers an enhancement of susceptibility that could be correlated with the dampening of several aspects of plant immunity, namely the oxidative burst and the transcription of several pathogenesis-related genes. Quite strikingly, the analysis of fungal transcription by RNASeq analysis under drought reveals that the fungus is greatly modifying its virulence program: genes coding for small secreted proteins were massively repressed in droughted plants compared to unstressed ones whereas genes coding for enzymes involved in degradation of cell-wall were induced. We also show that drought can lead to the partial breakdown of several major resistance genes by affecting R plant gene and/or pathogen effector expression. We propose a model where a yet unknown plant signal can trigger a change in the virulence program of the pathogen to adapt to a plant host that was affected by drought prior to infection. PMID:27833621

2-Furaldehyde diethyl acetal from tender coconut water (Cocos nucifera) attenuates biofilm formation and quorum sensing-mediated virulence of Chromobacterium violaceum and Pseudomonas aeruginosa.

PubMed

Sethupathy, Sivasamy; Nithya, Chari; Pandian, Shunmugiah Karutha

2015-01-01

The aim of this study was to evaluate the anti-biofilm and quorum sensing inhibitory (QSI) potential of tender coconut water (TCW) against Chromobacterium violaceum and Pseudomonas aeruginosa. TCW significantly inhibited the QS regulated violacein, virulence factors and biofilm production without affecting their growth. qRT-PCR analysis revealed the down-regulation of autoinducer synthase, transcriptional regulator and virulence genes. Mass-spectrometric analysis of a petroleum ether extract of the TCW hydrolyte revealed that 2-furaldehyde diethyl acetal (2FDA) and palmitic acid (PA) are the major compounds. In vitro bioassays confirmed the ability of 2FDA to inhibit the biofilm formation and virulence factors. In addition, the combination of PA with 2FDA resulted in potent inhibition of biofilm formation and virulence factors. The results obtained strongly suggest that TCW can be exploited as a base for designing a novel antipathogenic drug formulation to treat biofilm mediated infections caused by P. aeruginosa.

Catheter-related infections caused by Pseudomonas aeruginosa: virulence factors involved and their relationships.

PubMed

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.

Blue light treatment of Pseudomonas aeruginosa: Strong bactericidal activity, synergism with antibiotics and inactivation of virulence factors.

PubMed

Fila, Grzegorz; Kawiak, Anna; Grinholc, Mariusz Stanislaw

2017-08-18

Pseudomonas aeruginosa is among the most common pathogens responsible for both acute and chronic infections of high incidence and severity. Additionally, P. aeruginosa resistance to conventional antimicrobials has increased rapidly over the past decade. Therefore, it is crucial to explore new therapeutic options, particularly options that specifically target the pathogenic mechanisms of this microbe. The ability of a pathogenic bacterium to cause disease is dependent upon the production of agents termed 'virulence factors', and approaches to mitigate these agents have gained increasing attention as new antibacterial strategies. Although blue light irradiation is a promising alternative approach, only limited and preliminary studies have described its effect on virulence factors. The current study aimed to investigate the effects of lethal and sub-lethal doses of blue light treatment (BLT) on P. aeruginosa virulence factors. We analyzed the inhibitory effects of blue light irradiation on the production/activity of several virulence factors. Lethal BLT inhibited the activity of pyocyanin, staphylolysin, pseudolysin and other proteases, but sub-lethal BLT did not affect the production/expression of proteases, phospholipases, and flagella- or type IV pili-associated motility. Moreover, a eukaryotic cytotoxicity test confirmed the decreased toxicity of blue light-treated extracellular P. aeruginosa fractions. Finally, the increased antimicrobial susceptibility of P. aeruginosa treated with sequential doses of sub-lethal BLT was demonstrated with a checkerboard test. Thus, this work provides evidence-based proof of the susceptibility of drug-resistant P. aeruginosa to BLT-mediated killing, accompanied by virulence factor reduction, and describes the synergy between antibiotics and sub-lethal BLT.

Role of Staphylococcus aureus Virulence Factors in Inducing Inflammation and Vascular Permeability in a Mouse Model of Bacterial Endophthalmitis

PubMed Central

Kumar, Ajay; Kumar, Ashok

2015-01-01

Staphylococcus (S.) aureus is a common causative agent of bacterial endophthalmitis, a vision threatening complication of eye surgeries. The relative contribution of S. aureus virulence factors in the pathogenesis of endophthalmitis remains unclear. Here, we comprehensively analyzed the development of intraocular inflammation, vascular permeability, and the loss of retinal function in C57BL/6 mouse eyes, challenged with live S. aureus, heat-killed S. aureus (HKSA), peptidoglycan (PGN), lipoteichoic acid (LTA), staphylococcal protein A (SPA), α-toxin, and Toxic-shock syndrome toxin 1 (TSST1). Our data showed a dose-dependent (range 0.01 μg/eye to 1.0 μg/eye) increase in the levels of inflammatory mediators by all virulence factors. The cell wall components, particularly PGN and LTA, seem to induce higher levels of TNF-α, IL-6, KC, and MIP2, whereas the toxins induced IL-1β. Similarly, among the virulence factors, PGN induced higher PMN infiltration. The vascular permeability assay revealed significant leakage in eyes challenged with live SA (12-fold) and HKSA (7.3-fold), in comparison to other virulence factors (~2-fold) and controls. These changes coincided with retinal tissue damage, as evidenced by histological analysis. The electroretinogram (ERG) analysis revealed a significant decline in retinal function in eyes inoculated with live SA, followed by HKSA, SPA, and α-toxin. Together, these findings demonstrate the differential innate responses of the retina to S. aureus virulence factors, which contribute to intraocular inflammation and retinal function loss in endophthalmitis. PMID:26053426

Evaluation of Caco-2 cells response to Listeria monocytogenes virulence factors by RT-PCR.

PubMed

Xie, Manman; Ding, Chengchao; Guo, Liang; Chen, Guowei; Zeng, Haijuan; Liu, Qing

2018-04-30

Listeria monocytogenes expresses various virulence factors enabling the invasion and multiplying in host cells, and together induces cytokines transcription. In order to explore the relationship between virulence factors of L. monocytogenes wild-type EGD-e and cellular response in human colonic epithelial cell line(Caco-2), we constructed mutant strains with in-frame deletions of critical virulence genes of inlA, inlB, hly, actA and virulence regulatory factor prfA from EGD-e, respectively. Compared with EGD-e, mutant strains showed significantly decreased invasion and apoptosis in Caco-2 cells. However, mutant strains were capable to evoke cytokines transcription of interleukin-8 (IL-8), mononuclear chemoattractant protein-1 (MCP-1), tumor necrosis factor-a (TNF-a), interleukin-1β (IL-1β), interleukin-6 (IL-6) and CXCL-2 production in Caco-2 cells. Interestingly, EGD-e Δhly-infected Caco-2 cells showed a significant decrease of IL-6, IL-8 and MCP-1 transcription compared with EGD-e at 1 h post-infection. Simultaneously, EGD-e ΔinlB-infected cells showed a decrease in IL-6 transcription, while EGD-e ΔactA-infected cells reflected a decrease in MCP-1 transcription. Virulence genes play a role in inflammatory transcription, but the interaction between pathogenic bacteria and the host cells predominates in inflammatory transcription. Overall, the data showed cellular response of Caco-2 cells infected with EGD-e mutant strains. Copyright © 2018. Published by Elsevier Ltd.

Inactivation of pecS restores the virulence of mutants devoid of osmoregulated periplasmic glucans in the phytopathogenic bacterium Dickeya dadantii.

PubMed

Bontemps-Gallo, Sébastien; Madec, Edwige; Lacroix, Jean-Marie

2014-04-01

Dickeya dadantii is a phytopathogenic enterobacterium that causes soft rot disease in a wide range of plant species. Maceration, an apparent symptom of the disease, is the result of the synthesis and secretion of a set of plant cell wall-degrading enzymes (PCWDEs), but many additional factors are required for full virulence. Among these, osmoregulated periplasmic glucans (OPGs) and the PecS transcriptional regulator are essential virulence factors. Several cellular functions are controlled by both OPGs and PecS. Strains devoid of OPGs display a pleiotropic phenotype including total loss of virulence, loss of motility and severe reduction in the synthesis of PCWDEs. PecS is one of the major regulators of virulence in D. dadantii, acting mainly as a repressor of various cellular functions including virulence, motility and synthesis of PCWDEs. The present study shows that inactivation of the pecS gene restored virulence in a D. dadantii strain devoid of OPGs, indicating that PecS cannot be de-repressed in strains devoid of OPGs.

Virulence factors of the human opportunistic pathogen Serratia marcescens identified by in vivo screening

PubMed Central

Kurz, C.Léopold; Chauvet, Sophie; Andrès, Emmanuel; Aurouze, Marianne; Vallet, Isabelle; Michel, Gérard P.F.; Uh, Mitch; Celli, Jean; Filloux, Alain; de Bentzmann, Sophie; Steinmetz, Ivo; Hoffmann, Jules A.; Finlay, B.Brett; Gorvel, Jean-Pierre; Ferrandon, Dominique; Ewbank, Jonathan J.

2003-01-01

The human opportunistic pathogen Serratia marcescens is a bacterium with a broad host range, and represents a growing problem for public health. Serratia marcescens kills Caenorhabditis elegans after colonizing the nematode’s intestine. We used C.elegans to screen a bank of transposon-induced S.marcescens mutants and isolated 23 clones with an attenuated virulence. Nine of the selected bacterial clones also showed a reduced virulence in an insect model of infection. Of these, three exhibited a reduced cytotoxicity in vitro, and among them one was also markedly attenuated in its virulence in a murine lung infection model. For 21 of the 23 mutants, the transposon insertion site was identified. This revealed that among the genes necessary for full in vivo virulence are those that function in lipopolysaccharide (LPS) biosynthesis, iron uptake and hemolysin produc tion. Using this system we also identified novel conserved virulence factors required for Pseudomonas aeruginosa pathogenicity. This study extends the utility of C.elegans as an in vivo model for the study of bacterial virulence and advances the molecular understanding of S.marcescens pathogenicity. PMID:12660152

Plasma membrane lipids and their role in fungal virulence.

PubMed

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.

Assessment of virulence diversity of methicillin-resistant Staphylococcus aureus strains with a Drosophila melanogaster infection model.

PubMed

Wu, Kaiyu; Conly, John; Surette, Michael; Sibley, Christopher; Elsayed, Sameer; Zhang, Kunyan

2012-11-23

Staphylococcus aureus strains with distinct genetic backgrounds have shown different virulence in animal models as well as associations with different clinical outcomes, such as causing infection in the hospital or the community. With S. aureus strains carrying diverse genetic backgrounds that have been demonstrated by gene typing and genomic sequences, it is difficult to compare these strains using mammalian models. Invertebrate host models provide a useful alternative approach for studying bacterial pathogenesis in mammals since they have conserved innate immune systems of biological defense. Here, we employed Drosophila melanogaster as a host model for studying the virulence of S. aureus strains. Community-associated methicillin-resistant S. aureus (CA-MRSA) strains USA300, USA400 and CMRSA2 were more virulent than a hospital-associated (HA)-MRSA strain (CMRSA6) and a colonization strain (M92) in the D. melanogaster model. These results correlate with bacterial virulence in the Caenorhabditis elegans host model as well as human clinical data. Moreover, MRSA killing activities in the D. melanogaster model are associated with bacterial replication within the flies. Different MRSA strains induced similar host responses in D. melanogaster, but demonstrated differential expression of common bacterial virulence factors, which may account for the different killing activities in the model. In addition, hemolysin α, an important virulence factor produced by S. aureus in human infections is postulated to play a role in the fly killing. Our results demonstrate that the D. melanogaster model is potentially useful for studying S. aureus pathogenicity. Different MRSA strains demonstrated diverse virulence in the D. melanogaster model, which may be the result of differing expression of bacterial virulence factors in vivo.

Virulence gene regulation by CvfA, a putative RNase: the CvfA-enolase complex in Streptococcus pyogenes links nutritional stress, growth-phase control, and virulence gene expression.

PubMed

Kang, Song Ok; Caparon, Michael G; Cho, Kyu Hong

2010-06-01

Streptococcus pyogenes, a multiple-auxotrophic human pathogen, regulates virulence gene expression according to nutritional availability during various stages in the infection process or in different infection sites. We discovered that CvfA influenced the expression of virulence genes according to growth phase and nutritional status. The influence of CvfA in C medium, rich in peptides and poor in carbohydrates, was most pronounced at the stationary phase. Under these conditions, up to 30% of the transcriptome exhibited altered expression; the levels of expression of multiple virulence genes were altered, including the genes encoding streptokinase, CAMP factor, streptolysin O, M protein (more abundant in the CvfA(-) mutant), SpeB, mitogenic factor, and streptolysin S (less abundant). The increase of carbohydrates or peptides in media restored the levels of expression of the virulence genes in the CvfA(-) mutant to wild-type levels (emm, ska, and cfa by carbohydrates; speB by peptides). Even though the regulation of gene expression dependent on nutritional stress is commonly linked to the stringent response, the levels of ppGpp were not altered by deletion of cvfA. Instead, CvfA interacted with enolase, implying that CvfA, a putative RNase, controls the transcript decay rates of virulence factors or their regulators according to nutritional status. The virulence of CvfA(-) mutants was highly attenuated in murine models, indicating that CvfA-mediated gene regulation is necessary for the pathogenesis of S. pyogenes. Taken together, the CvfA-enolase complex in S. pyogenes is involved in the regulation of virulence gene expression by controlling RNA degradation according to nutritional stress.

Antimicrobial peptide GH12 suppresses cariogenic virulence factors of Streptococcus mutans

PubMed Central

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

Gene expression patterns and dynamics of the colonization of common bean (Phaseolus vulgaris L.) by highly virulent and weakly virulent strains of Fusarium oxysporum

PubMed Central

Niño-Sánchez, Jonathan; Tello, Vega; Casado-del Castillo, Virginia; Thon, Michael R.; Benito, Ernesto P.; Díaz-Mínguez, José María

2015-01-01

The dynamics of root and hypocotyl colonization, and the gene expression patterns of several fungal virulence factors and plant defense factors have been analyzed and compared in the interaction of two Fusarium oxysporum f. sp. phaseoli strains displaying clear differences in virulence, with a susceptible common bean cultivar. The growth of the two strains on the root surface and the colonization of the root was quantitatively similar although the highly virulent (HV) strain was more efficient reaching the central root cylinder. The main differences between both strains were found in the temporal and spatial dynamics of crown root and hypocotyl colonization. The increase of fungal biomass in the crown root was considerably larger for the HV strain, which, after an initial stage of global colonization of both the vascular cylinder and the parenchymal cells, restricted its growth to the newly differentiated xylem vessels. The weakly virulent (WV) strain was a much slower and less efficient colonizer of the xylem vessels, showing also growth in the intercellular spaces of the parenchyma. Most of the virulence genes analyzed showed similar expression patterns in both strains, except SIX1, SIX6 and the gene encoding the transcription factor FTF1, which were highly upregulated in root crown and hypocotyl. The response induced in the infected plant showed interesting differences for both strains. The WV strain induced an early and strong transcription of the PR1 gene, involved in SAR response, while the HV strain preferentially induced the early expression of the ethylene responsive factor ERF2. PMID:25883592

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

PubMed

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 (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(10)CFU, 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.

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

PubMed Central

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 (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 (log10CFU, 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. PMID:22685551

Genome-wide analysis of gene expression and protein secretion of Babesia canis during virulent infection identifies potential pathogenicity factors.

PubMed

Eichenberger, Ramon M; Ramakrishnan, Chandra; Russo, Giancarlo; Deplazes, Peter; Hehl, Adrian B

2017-06-13

Infections of dogs with virulent strains of Babesia canis are characterized by rapid onset and high mortality, comparable to complicated human malaria. As in other apicomplexan parasites, most Babesia virulence factors responsible for survival and pathogenicity are secreted to the host cell surface and beyond where they remodel and biochemically modify the infected cell interacting with host proteins in a very specific manner. Here, we investigated factors secreted by B. canis during acute infections in dogs and report on in silico predictions and experimental analysis of the parasite's exportome. As a backdrop, we generated a fully annotated B. canis genome sequence of a virulent Hungarian field isolate (strain BcH-CHIPZ) underpinned by extensive genome-wide RNA-seq analysis. We find evidence for conserved factors in apicomplexan hemoparasites involved in immune-evasion (e.g. VESA-protein family), proteins secreted across the iRBC membrane into the host bloodstream (e.g. SA- and Bc28 protein families), potential moonlighting proteins (e.g. profilin and histones), and uncharacterized antigens present during acute crisis in dogs. The combined data provides a first predicted and partially validated set of potential virulence factors exported during fatal infections, which can be exploited for urgently needed innovative intervention strategies aimed at facilitating diagnosis and management of canine babesiosis.

Correlation between genetic variability and virulence factors in clinical strains of Malassezia pachydermatis of animal origin.

PubMed

Buommino, Elisabetta; Nocera, Francesca Paola; Parisi, Annamaria; Rizzo, Antonietta; Donnarumma, Giovanna; Mallardo, Karina; Fiorito, Filomena; Baroni, Adone; De Martino, Luisa

2016-07-01

Malassezia pachydermatis is a yeast belonging to the microbiota of the skin and mucous membranes of dog and cat, but it can also act as pathogen, causing dermatitis. The aim of this work was to evaluate the genetic variability of M. pachydermatis strains isolated from symptomatic dogs and cats and determine a correlation between genotype and phenotype. For this purpose eleven strains of M. pachydermatis were molecularly classified by nested-polymerase chain reaction (nested-PCR) based on ITS-1 and ITS-2 regions, specific for fungal rRNA genes. Furthermore, random amplification of polymorphic DNA (RAPD) was applied for genetic typing of M. pachydermatis isolates identifying four different genotypes. Strains belonging to genotype 1 produced the highest amount of biofilm and phospholipase activity. The inflammatory response induced by M. pachydermatis strains in immortalized human keratinocytes (HaCat cells) was significantly different when we compared the results obtained from each strain. In particular, HaCat cells infected with the strains belonging to genotypes 1 and 2 triggered the highest levels of increase in TLR-2, IL-1β, IL-6, IL-8, COX-2 and MMP-9 expression. By contrast, cells infected with the strains of genotype 3 and those of genotype 4 did not significantly induce TLR-2 and cytokines. The results obtained might suggest a possible association between genotype and virulence factors expressed by M. pachydermatis strains. This highlights the need for a more accurate identification of the yeast to improve the therapeutic approach and to monitor the onset of human infections caused by this emergent zoonotic pathogen.

Petri Net-Based Model of Helicobacter pylori Mediated Disruption of Tight Junction Proteins in Stomach Lining during Gastric Carcinoma

PubMed Central

Naz, Anam; Obaid, Ayesha; Awan, Faryal M.; Ikram, Aqsa; Ahmad, Jamil; Ali, Amjad

2017-01-01

Tight junctions help prevent the passage of digestive enzymes and microorganisms through the space between adjacent epithelial cells lining. However, Helicobacter pylori encoded virulence factors negatively regulate these tight junctions and contribute to dysfunction of gastric mucosa. Here, we have predicted the regulation of important tight junction proteins, such as Zonula occludens-1, Claudin-2 and Connexin32 in the presence of pathogenic proteins. Molecular events such as post translational modifications and crosstalk between phosphorylation, O-glycosylation, palmitoylation and methylation are explored which may compromise the integrity of these tight junction proteins. Furthermore, the signaling pathways disrupted by dysregulated kinases, proteins and post-translational modifications are reviewed to design an abstracted computational model showing the situation-dependent dynamic behaviors of these biological processes and entities. A qualitative hybrid Petri Net model is therefore constructed showing the altered host pathways in the presence of virulence factor cytotoxin-associated gene A, leading to the disruption of tight junction proteins. The model is qualitative logic-based, which does not depend on any kinetic parameter and quantitative data and depends on knowledge derived from experiments. The designed model provides insights into the tight junction disruption and disease progression. Model is then verified by the available experimental data, nevertheless formal in vitro experimentation is a promising way to ensure its validation. The major findings propose that H. pylori activated kinases are responsible to trigger specific post translational modifications within tight junction proteins, at specific sites. These modifications may favor alterations in gastric barrier and provide a route to bacterial invasion into host cells. PMID:28932213

Petri Net-Based Model of Helicobacter pylori Mediated Disruption of Tight Junction Proteins in Stomach Lining during Gastric Carcinoma.

PubMed

Naz, Anam; Obaid, Ayesha; Awan, Faryal M; Ikram, Aqsa; Ahmad, Jamil; Ali, Amjad

2017-01-01

Tight junctions help prevent the passage of digestive enzymes and microorganisms through the space between adjacent epithelial cells lining. However, Helicobacter pylori encoded virulence factors negatively regulate these tight junctions and contribute to dysfunction of gastric mucosa. Here, we have predicted the regulation of important tight junction proteins, such as Zonula occludens-1, Claudin-2 and Connexin32 in the presence of pathogenic proteins. Molecular events such as post translational modifications and crosstalk between phosphorylation, O-glycosylation, palmitoylation and methylation are explored which may compromise the integrity of these tight junction proteins. Furthermore, the signaling pathways disrupted by dysregulated kinases, proteins and post-translational modifications are reviewed to design an abstracted computational model showing the situation-dependent dynamic behaviors of these biological processes and entities. A qualitative hybrid Petri Net model is therefore constructed showing the altered host pathways in the presence of virulence factor cytotoxin-associated gene A, leading to the disruption of tight junction proteins. The model is qualitative logic-based, which does not depend on any kinetic parameter and quantitative data and depends on knowledge derived from experiments. The designed model provides insights into the tight junction disruption and disease progression. Model is then verified by the available experimental data, nevertheless formal in vitro experimentation is a promising way to ensure its validation. The major findings propose that H. pylori activated kinases are responsible to trigger specific post translational modifications within tight junction proteins, at specific sites. These modifications may favor alterations in gastric barrier and provide a route to bacterial invasion into host cells.

Metabolism of the vacuolar pathogen Legionella and implications for virulence.

PubMed

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.

A variable region within the genome of Streptococcus pneumoniae contributes to strain-strain variation in virulence.

PubMed

Harvey, Richard M; Stroeher, Uwe H; Ogunniyi, Abiodun D; Smith-Vaughan, Heidi C; Leach, Amanda J; Paton, James C

2011-05-05

The bacterial factors responsible for the variation in invasive potential between different clones and serotypes of Streptococcus pneumoniae are largely unknown. Therefore, the isolation of rare serotype 1 carriage strains in Indigenous Australian communities provided a unique opportunity to compare the genomes of non-invasive and invasive isolates of the same serotype in order to identify such factors. The human virulence status of non-invasive, intermediately virulent and highly virulent serotype 1 isolates was reflected in mice and showed that whilst both human non-invasive and highly virulent isolates were able to colonize the murine nasopharynx equally, only the human highly virulent isolates were able to invade and survive in the murine lungs and blood. Genomic sequencing comparisons between these isolates identified 8 regions >1 kb in size that were specific to only the highly virulent isolates, and included a version of the pneumococcal pathogenicity island 1 variable region (PPI-1v), phage-associated adherence factors, transporters and metabolic enzymes. In particular, a phage-associated endolysin, a putative iron/lead permease and an operon within PPI-1v exhibited niche-specific changes in expression that suggest important roles for these genes in the lungs and blood. Moreover, in vivo competition between pneumococci carrying PPI-1v derivatives representing the two identified versions of the region showed that the version of PPI-1v in the highly virulent isolates was more competitive than the version from the less virulent isolates in the nasopharyngeal tissue, blood and lungs. This study is the first to perform genomic comparisons between serotype 1 isolates with distinct virulence profiles that correlate between mice and humans, and has highlighted the important role that hypervariable genomic loci, such as PPI-1v, play in pneumococcal disease. The findings of this study have important implications for understanding the processes that drive progression from colonization to invasive disease and will help direct the development of novel therapeutic strategies.

Molecular insights into Burkholderia pseudomallei and Burkholderia mallei pathogenesis.

PubMed

Galyov, Edouard E; Brett, Paul J; DeShazer, David

2010-01-01

Burkholderia pseudomallei and Burkholderia mallei are closely related gram-negative bacteria that can cause serious diseases in humans and animals. This review summarizes the current and rapidly expanding knowledge on the specific virulence factors employed by these pathogens and their roles in the pathogenesis of melioidosis and glanders. In particular, the contributions of recently identified virulence factors are described in the context of the intracellular lifestyle of these pathogens. Throughout this review, unique and shared virulence features of B. pseudomallei and B. mallei are discussed.

Antimicrobial Resistance and Virulence: a Successful or Deleterious Association in the Bacterial World?

PubMed Central

Beceiro, Alejandro; Tomás, María

2013-01-01

SUMMARY Hosts and bacteria have coevolved over millions of years, during which pathogenic bacteria have modified their virulence mechanisms to adapt to host defense systems. Although the spread of pathogens has been hindered by the discovery and widespread use of antimicrobial agents, antimicrobial resistance has increased globally. The emergence of resistant bacteria has accelerated in recent years, mainly as a result of increased selective pressure. However, although antimicrobial resistance and bacterial virulence have developed on different timescales, they share some common characteristics. This review considers how bacterial virulence and fitness are affected by antibiotic resistance and also how the relationship between virulence and resistance is affected by different genetic mechanisms (e.g., coselection and compensatory mutations) and by the most prevalent global responses. The interplay between these factors and the associated biological costs depend on four main factors: the bacterial species involved, virulence and resistance mechanisms, the ecological niche, and the host. The development of new strategies involving new antimicrobials or nonantimicrobial compounds and of novel diagnostic methods that focus on high-risk clones and rapid tests to detect virulence markers may help to resolve the increasing problem of the association between virulence and resistance, which is becoming more beneficial for pathogenic bacteria. PMID:23554414

Genome Sequences and Phylogenetic Analysis of K88- and F18-Positive Porcine Enterotoxigenic Escherichia coli

PubMed Central

Shepard, Sara M.; Danzeisen, Jessica L.; Isaacson, Richard E.; Seemann, Torsten; Achtman, Mark

2012-01-01

Porcine enterotoxigenic Escherichia coli (ETEC) continues to result in major morbidity and mortality in the swine industry via postweaning diarrhea. The key virulence factors of ETEC strains, their serotypes, and their fimbrial components have been well studied. However, most studies to date have focused on plasmid-encoded traits related to colonization and toxin production, and the chromosomal backgrounds of these strains have been largely understudied. Here, we generated the genomic sequences of K88-positive and F18-positive porcine ETEC strains and examined the phylogenetic distribution of clinical porcine ETEC strains and their plasmid-associated genetic content. The genomes of porcine ETEC strains UMNK88 and UMNF18 were both found to contain remarkable plasmid complements containing known virulence factors, potential novel virulence factors, and antimicrobial resistance-associated elements. The chromosomes of these strains also possessed several unique genomic islands containing hypothetical genes with similarity to classical virulence factors, although phage-associated genomic islands dominated the accessory genomes of these strains. Phylogenetic analysis of 78 clinical isolates associated with neonatal and porcine diarrhea revealed that a limited subset of porcine ETEC lineages exist that generally contain common toxin and fimbrial profiles, with many of the isolates belonging to the ST10, ST23, and ST169 multilocus sequencing types. These lineages were generally distinct from existing human ETEC database isolates. Overall, most porcine ETEC strains appear to have emerged from a limited subset of E. coli lineages that either have an increased propensity to carry plasmid-encoded virulence factors or have the appropriate ETEC core genome required for virulence. PMID:22081385

Secretome Analysis Identifies Potential Pathogenicity/Virulence Factors of Tilletia indica, a Quarantined Fungal Pathogen Inciting Karnal Bunt Disease in Wheat.

PubMed

Pandey, Vishakha; Singh, Manoj; Pandey, Dinesh; Marla, Soma; Kumar, Anil

2018-04-01

Tilletia indica is a smut fungus that incites Karnal bunt in wheat. It has been considered as quarantine pest in more than 70 countries. Despite its quarantine significance, there is meager knowledge regarding the molecular mechanisms of disease pathogenesis. Moreover, various disease management strategies have proven futile. Development of effective disease management strategy requires identification of pathogenicity/virulence factors. With this aim, the present study was conducted to compare the secretomes of T. indica isolates, that is, highly (TiK) and low (TiP) virulent isolates. About 120 and 95 protein spots were detected reproducibly in TiK and TiP secretome gel images. Nineteen protein spots, which were consistently observed as upregulated/differential in the secretome of TiK isolate, were selected for their identification by MALDI-TOF/TOF. Identified proteins exhibited homology with fungal proteins playing important role in fungal adhesion, penetration, invasion, protection against host-derived reactive oxygen species, production of virulence factors, cellular signaling, and degradation of host cell wall proteins and antifungal proteins. These results were complemented with T. indica genome sequence leading to identification of candidate pathogenicity/virulence factors homologs that were further subjected to sequence- and structure-based functional annotation. Thus, present study reports the first comparative secretome analysis of T. indica for identification of pathogenicity/virulence factors. This would provide insights into pathogenic mechanisms of T. indica and aid in devising effective disease management strategies. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

XocR, a LuxR solo required for virulence in Xanthomonas oryzae pv. oryzicola.

PubMed

Xu, Huiyong; Zhao, Yancun; Qian, Guoliang; Liu, Fengquan

2015-01-01

Xanthomonas oryzae pv. oryzicola (Xoc) causes bacterial leaf streak (BLS) in rice, a serious bacterial disease of rice in Asia and parts of Africa. The virulence mechanisms of Xoc are not entirely clear and control measures for BLS are poorly developed. The solo LuxR proteins are widespread and shown to be involved in virulence in some plant associated bacteria (PAB). Here, we have cloned and characterized a PAB LuxR solo from Xoc, named as XocR. Mutation of xocR almost completely impaired the virulence ability of Xoc on host rice, but did not alter the ability to trigger HR (hypersensitive response, a programmed cell death) on non-host (plant) tobacco, suggesting the diversity of function of xocR in host and non-host plants. We also provide evidence to show that xocR is involved in the regulation of growth-independent cell motility in response to a yet-to-be-identified rice signal, as mutation of xocR impaired cell swimming motility of wild-type Rs105 in the presence but not absence of rice macerate. We further found that xocR regulated the transcription of two characterized virulence-associated genes (recN and trpE) in the presence of rice macerate. The promoter regions of recN and trpE possessed a potential binding motif (an imperfect pip box-like element) of XocR, raising the possibility that XocR might directly bind the promoter regions of these two genes to regulate their transcriptional activity. Our studies add a new member of PAB LuxR solos and also provide new insights into the role of PAB LuxR solo in the virulence of Xanthomonas species.

Dynamics of E.coli virulence factors in dairy cow herds

USDA-ARS?s Scientific Manuscript database

Background. Dairy farms are known reservoirs of entero-pathogenic E. coli (EPEC). EPEC, or the virulence factors associated with pathogenicity, have been detected in manure, milk, and the farm environment. However, it is unclear which farm compartments are reservoirs contributing to EPEC persistence...

TLR-2 Recognizes Propionibacterium acnes CAMP Factor 1 from Highly Inflammatory Strains

PubMed Central

Ollagnier, Guillaume; Désiré, Nathalie; Sayon, Sophie; Raingeaud, Jöel; Marcelin, Anne-Geneviève; Calvez, Vincent; Khammari, Amir; Batteux, Frédéric; Dréno, Brigitte; Dupin, Nicolas

2016-01-01

Background Propionibacterium acnes (P. acnes) is an anaerobic, Gram-positive bacteria encountered in inflammatory acne lesions, particularly in the pilosebaceous follicle. P. acnes triggers a strong immune response involving keratinocytes, sebocytes and monocytes, the target cells during acne development. Lipoteicoic acid and peptidoglycan induce the inflammatory reaction, but no P. acnes surface protein interacting with Toll-like receptors has been identified. P. acnes surface proteins have been extracted by lithium stripping and shown to induce CXCL8 production by keratinocytes. Methodology and principal findings Far-western blotting identified two surface proteins, of 24.5- and 27.5-kDa in size, specifically recognized by TLR2. These proteins were characterized, by LC-MS/MS, as CAMP factor 1 devoid of its signal peptide sequence, as shown by N-terminal sequencing. Purified CAMP factor 1 induces CXCL8 production by activating the CXCL8 gene promoter, triggering the synthesis of CXCL8 mRNA. Antibodies against TLR2 significantly decreased the CXCL8 response. For the 27 P. acnes strains used in this study, CAMP1-TLR2 binding intensity was modulated and appeared to be strong in type IB and II strains, which produced large amounts of CXCL8, whereas most of the type IA1 and IA2 strains presented little or no CAMP1-TLR2 binding and low levels of CXCL8 production. The nucleotide sequence of CAMP factor displays a major polymorphism, defining two distinct genetic groups corresponding to CAMP factor 1 with 14 amino-acid changes from strains phylotyped II with moderate and high levels of CAMP1-TLR2 binding activity, and CAMP factor 1 containing 0, 1 or 2 amino-acid changes from strains phylotyped IA1, IA2, or IB presenting no, weak or moderate CAMP1-TLR2 binding. Conclusions Our findings indicate that CAMP factor 1 may contribute to P. acnes virulence, by amplifying the inflammation reaction through direct interaction with TLR2. PMID:27902761

TLR-2 Recognizes Propionibacterium acnes CAMP Factor 1 from Highly Inflammatory Strains.

PubMed

Lheure, Coralie; Grange, Philippe Alain; Ollagnier, Guillaume; Morand, Philippe; Désiré, Nathalie; Sayon, Sophie; Corvec, Stéphane; Raingeaud, Jöel; Marcelin, Anne-Geneviève; Calvez, Vincent; Khammari, Amir; Batteux, Frédéric; Dréno, Brigitte; Dupin, Nicolas

2016-01-01

Propionibacterium acnes (P. acnes) is an anaerobic, Gram-positive bacteria encountered in inflammatory acne lesions, particularly in the pilosebaceous follicle. P. acnes triggers a strong immune response involving keratinocytes, sebocytes and monocytes, the target cells during acne development. Lipoteicoic acid and peptidoglycan induce the inflammatory reaction, but no P. acnes surface protein interacting with Toll-like receptors has been identified. P. acnes surface proteins have been extracted by lithium stripping and shown to induce CXCL8 production by keratinocytes. Far-western blotting identified two surface proteins, of 24.5- and 27.5-kDa in size, specifically recognized by TLR2. These proteins were characterized, by LC-MS/MS, as CAMP factor 1 devoid of its signal peptide sequence, as shown by N-terminal sequencing. Purified CAMP factor 1 induces CXCL8 production by activating the CXCL8 gene promoter, triggering the synthesis of CXCL8 mRNA. Antibodies against TLR2 significantly decreased the CXCL8 response. For the 27 P. acnes strains used in this study, CAMP1-TLR2 binding intensity was modulated and appeared to be strong in type IB and II strains, which produced large amounts of CXCL8, whereas most of the type IA1 and IA2 strains presented little or no CAMP1-TLR2 binding and low levels of CXCL8 production. The nucleotide sequence of CAMP factor displays a major polymorphism, defining two distinct genetic groups corresponding to CAMP factor 1 with 14 amino-acid changes from strains phylotyped II with moderate and high levels of CAMP1-TLR2 binding activity, and CAMP factor 1 containing 0, 1 or 2 amino-acid changes from strains phylotyped IA1, IA2, or IB presenting no, weak or moderate CAMP1-TLR2 binding. Our findings indicate that CAMP factor 1 may contribute to P. acnes virulence, by amplifying the inflammation reaction through direct interaction with TLR2.

Limiting opportunities for cheating stabilizes virulence in insect parasitic nematodes

USDA-ARS?s Scientific Manuscript database

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...

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

USDA-ARS?s Scientific Manuscript database

The factors defining virulence of foot-and-mouth disease virus (FMDV) in cattle were 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). After simulated-natural, aerosol inoculation, both vi...

Basis of virulence in a Panton-Valentine leukocidin-negative community-associated methicillin-resistant Staphylococcus aureus strain.

PubMed

Chen, Yan; Yeh, Anthony J; Cheung, Gordon Y C; Villaruz, Amer E; Tan, Vee Y; Joo, Hwang-Soo; Chatterjee, Som S; Yu, Yunsong; Otto, Michael

2015-02-01

Community-associated (CA) infections with methicillin-resistant Staphylococcus aureus (MRSA) are on a global rise. However, analysis of virulence characteristics has been limited almost exclusively to the US endemic strain USA300. CA-MRSA strains that do not produce Panton-Valentine leukocidin (PVL) have not been investigated on a molecular level. Therefore, we analyzed virulence determinants in a PVL-negative CA-MRSA strain, ST72, from Korea. Genome-wide analysis identified 3 loci that are unique to that strain, but did not affect virulence. In contrast, phenol-soluble modulins (PSMs) and the global virulence regulator Agr strongly affected lysis of neutrophils and erythrocytes, while α-toxin and Agr had a major impact on in vivo virulence. Our findings substantiate the general key roles these factors play in CA-MRSA virulence. However, our analyses also showed noticeable differences to strain USA300, inasmuch as α-toxin emerged as a much more important factor than PSMs in experimental skin infection caused by ST72. Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Bicarbonate Increases Binding Affinity of Vibrio cholerae ToxT to Virulence Gene Promoters

PubMed Central

Thomson, Joshua J.

2014-01-01

The major Vibrio cholerae virulence gene transcription activator, ToxT, is responsible for the production of the diarrhea-inducing cholera toxin (CT) and the major colonization factor, toxin coregulated pilus (TCP). In addition to the two primary virulence factors mentioned, ToxT is responsible for the activation of accessory virulence genes, such as aldA, tagA, acfA, acfD, tcpI, and tarAB. ToxT activity is negatively modulated by bile and unsaturated fatty acids found in the upper small intestine. Conversely, previous work identified another intestinal signal, bicarbonate, which enhances the ability of ToxT to activate production of CT and TCP. The work presented here further elucidates the mechanism for the enhancement of ToxT activity by bicarbonate. Bicarbonate was found to increase the activation of ToxT-dependent accessory virulence promoters in addition to those that produce CT and TCP. Bicarbonate is taken up into the V. cholerae cell, where it positively affects ToxT activity by increasing DNA binding affinity for the virulence gene promoters that ToxT activates regardless of toxbox configuration. The increase in ToxT binding affinity in the presence of bicarbonate explains the elevated level of virulence gene transcription. PMID:25182489

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

PubMed

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

PubMed Central

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. PMID:25147855

The red pigment prodigiosin is not an essential virulence factor in entomopathogenic Serratia marcescens.

PubMed

Zhou, Wei; Li, JingHua; Chen, Jie; Liu, XiaoYuan; Xiang, TingTing; Zhang, Lin; Wan, YongJi

2016-05-01

Although pigments produced by pathogenic microbes are generally hypothesized as essential virulence factors, the role of red pigment prodigiosin in the pathogenesis of entomopathogenic Serratia marcescens is not clear. In this study, we analyzed the pathogenicity of different pigmented S. marcescens strains and their non-pigmented mutants in silkworms. Each pigmented strain and the corresponding non-pigmented mutants showed very similar LD50 value (statistically no difference), but caused very different symptom (color of the dead larva). Our results clearly indicated that the red pigment prodigiosin is not an essential virulence factor in entomopathogenic S. marcescens. Copyright © 2016 Elsevier Inc. All rights reserved.

Intracellular survival of virulence and low-virulence strains of Vibrio parahaemolyticus in Epinephelus awoara macrophages and peripheral leukocytes.

PubMed

Xu, X J; Sang, B H; Chen, W B; Yan, Q P; Xiong, Z Y; Su, J B; Zou, W Z

2015-01-30

In this study, we examined the virulence factors and pathogenesis of Vibrio parahaemolyticus in Epinephelus awoara. The chemotactic motility of V. parahaemolyticus for phagocytosis and intracellular survival in fish macrophages was determined using virulence strains and low-virulence strains of V. parahaemolyticus. We found that the intracellular mean number of virulence strains of V. parahaemolyticus ranged from 0-180 min after co-incubation with macrophages and peripheral leukocytes, was relatively low, and decreased steadily over the observation period. Low-virulence strains of V. parahaemolyticus were unable to survive in peripheral leukocytes and macrophages. Cell viability in response to V. parahaemolyticus was assessed using the MTT assay. Low-virulence V. parahaemolyticus strains exhibited lower cytotoxicity compared to virulent strains. The average percent of live macrophages and peripheral leukocytes infected by V. parahaemolyticus ranged from 13.50-79.20%. These results indicate that V. parahaemolyticus in E. awoara is a facultative intracellular bacterium that may be involved in virulence.

Detection of Streptococcus pyogenes virulence genes in Streptococcus dysgalactiae subsp. equisimilis from Vellore, India.

PubMed

Babbar, Anshu; Itzek, Andreas; Pieper, Dietmar H; Nitsche-Schmitz, D Patric

2018-03-12

Streptococcus dysgalactiae subsp. equisimilis (SDSE), belonging to the group C and G streptococci, are human pathogens reported to cause clinical manifestations similar to infections caused by Streptococcus pyogenes. To scrutinize the distribution of gene coding for S. pyogenes virulence factors in SDSE, 255 isolates were collected from humans infected with SDSE in Vellore, a region in southern India, with high incidence of SDSE infections. Initial evaluation indicated SDSE isolates comprising of 82.35% group G and 17.64% group C. A multiplex PCR system was used to detect 21 gene encoding virulence-associated factors of S. pyogenes, like superantigens, DNases, proteinases, and other immune modulatory toxins. As validated by DNA sequencing of the PCR products, sequences homologous to speC, speG, speH, speI, speL, ssa and smeZ of the family of superantigen coding genes and for DNases like sdaD and sdc were detected in the SDSE collection. Furthermore, there was high abundance (48.12% in group G and 86.6% in group C SDSE) of scpA, the gene coding for C5a peptidase in these isolates. Higher abundance of S. pyogenes virulence factor genes was observed in SDSE of Lancefield group C as compared to group G, even though the incidence rates in former were lower. This study not only substantiates detection of S. pyogenes virulence factor genes in whole genome sequenced SDSE but also makes significant contribution towards the understanding of SDSE and its increasing virulence potential.

Down Regulation of Virulence Factors of Pseudomonas aeruginosa by Salicylic Acid Attenuates Its Virulence on Arabidopsis thaliana and Caenorhabditis elegans

PubMed Central

Prithiviraj, B.; Bais, H. P.; Weir, T.; Suresh, B.; Najarro, E. H.; Dayakar, B. V.; Schweizer, H. P.; Vivanco, J. M.

2005-01-01

Salicylic acid (SA) is a phenolic metabolite produced by plants and is known to play an important role in several physiological processes, such as the induction of plant defense responses against pathogen attack. Here, using the Arabidopsis thaliana-Pseudomonas aeruginosa pathosystem, we provide evidence that SA acts directly on the pathogen, down regulating fitness and virulence factor production of the bacteria. Pseudomonas aeruginosa PA14 showed reduced attachment and biofilm formation on the roots of the Arabidopsis mutants lox2 and cpr5-2, which produce elevated amounts of SA, as well as on wild-type Arabidopsis plants primed with exogenous SA, a treatment known to enhance endogenous SA concentration. Salicylic acid at a concentration that did not inhibit PA14 growth was sufficient to significantly affect the ability of the bacteria to attach and form biofilm communities on abiotic surfaces. Furthermore, SA down regulated three known virulence factors of PA14: pyocyanin, protease, and elastase. Interestingly, P. aeruginosa produced more pyocyanin when infiltrated into leaves of the Arabidopsis transgenic line NahG, which accumulates less SA than wild-type plants. This finding suggests that endogenous SA plays a role in down regulating the synthesis and secretion of pyocyanin in vivo. To further test if SA directly affects the virulence of P. aeruginosa, we used the Caenorhabiditis elegans-P. aeruginosa infection model. The addition of SA to P. aeruginosa lawns significantly diminished the bacterium's ability to kill the worms, without affecting the accumulation of bacteria inside the nematodes' guts, suggesting that SA negatively affects factors that influence the virulence of P. aeruginosa. We employed microarray technology to identify SA target genes. These analyses showed that SA treatment affected expression of 331 genes. It selectively repressed transcription of exoproteins and other virulence factors, while it had no effect on expression of housekeeping genes. Our results indicate that in addition to its role as a signal molecule in plant defense responses, SA works as an anti-infective compound by affecting the physiology of P. aeruginosa and ultimately attenuating its virulence. PMID:16113247

Gallium induces the production of virulence factors in Pseudomonas aeruginosa.

PubMed

García-Contreras, Rodolfo; Pérez-Eretza, Berenice; Lira-Silva, Elizabeth; Jasso-Chávez, Ricardo; Coria-Jiménez, Rafael; Rangel-Vega, Adrián; Maeda, Toshinari; Wood, Thomas K

2014-02-01

The novel antimicrobial gallium is a nonredox iron III analogue with bacteriostatic and bactericidal properties, effective for the treatment of Pseudomonas aeruginosa in vitro and in vivo in mouse and rabbit infection models. It interferes with iron metabolism, transport, and presumably its homeostasis. As gallium exerts its antimicrobial effects by competing with iron, we hypothesized that it ultimately will lead cells to an iron deficiency status. As iron deficiency promotes the expression of virulence factors in vitro and promotes the pathogenicity of P. aeruginosa in animal models, it is anticipated that treatment with gallium will also promote the production of virulence factors. To test this hypothesis, the reference strain PA14 and two clinical isolates from patients with cystic fibrosis were exposed to gallium, and their production of pyocyanin, rhamnolipids, elastase, alkaline protease, alginate, pyoverdine, and biofilm was determined. Gallium treatment induced the production of all the virulence factors tested in the three strains except for pyoverdine. In addition, as the Ga-induced virulence factors are quorum sensing controlled, co-administration of Ga and the quorum quencher brominated furanone C-30 was assayed, and it was found that C-30 alleviated growth inhibition from gallium. Hence, adding both C-30 and gallium may be more effective in the treatment of P. aeruginosa infections. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Study of virulence factors of uropathogenic Escherichia coli and its antibiotic susceptibility pattern.

PubMed

Mittal, Seema; Sharma, Madhu; Chaudhary, Uma

2014-01-01

Urinary tract infection (UTI) is one of the most common nosocomial infections, caused by Escherichia coli. This study determined the presence of virulence factors in the organism and correlates it with the multi-drug resistance (MDR). The aim of the following study is to assess the virulence factors of uropathogenic E. coli and antibiotic susceptibility pattern. This was a prospective study conducted in the Department of Microbiology in PT. B. D. Sharma, PGIMS, Rohtak. The study was conducted over a period of 1 year. Urine samples received were processed as per standard microbiological procedures. Virulence factors such as hemolysin, hemagglutination, cell surface hydrophobicity, serum resistance, gelatinase and siderophore production were studied. The antimicrobial susceptibility was done as per Clinical and Laboratory Standard Institute Guidelines. The data was analyzed by using SPSS(Statistical Package for the social sciences) IBM Corporation version 17.0. A two sided P ≤ 0.05 was considered to be significant. Hemolysin production was seen in 47.4%, hemagglutination in 74.8%, cell surface hydrophobicity in 61%, serum resistance in 59%, gelatinase in 67.5% and siderophore production in 88% isolates. Nitrofurantoin was found to be most effective followed by, gatifloxacin and gentamicin. Twenty nine percent (29.62%) isolates were MDR. Therefore, the knowledge of virulence factors of E. coli and their antibiotic susceptibility pattern will help in better understanding of the organism and in the treatment of UTI.

Rice Exo70 interacts with a fungal effector, AVR-Pii, and is required for AVR-Pii-triggered immunity.

PubMed

Fujisaki, Koki; Abe, Yoshiko; Ito, Akiko; Saitoh, Hiromasa; Yoshida, Kentaro; Kanzaki, Hiroyuki; Kanzaki, Eiko; Utsushi, Hiroe; Yamashita, Tetsuro; Kamoun, Sophien; Terauchi, Ryohei

2015-09-01

Vesicle trafficking including the exocytosis pathway is intimately associated with host immunity against pathogens. However, we still have insufficient knowledge about how it contributes to immunity, and how pathogen factors affect it. In this study, we explore host factors that interact with the Magnaporthe oryzae effector AVR-Pii. Gel filtration chromatography and co-immunoprecipitation assays identified a 150 kDa complex of proteins in the soluble fraction comprising AVR-Pii and OsExo70-F2 and OsExo70-F3, two rice Exo70 proteins presumably involved in exocytosis. Simultaneous knockdown of OsExo70-F2 and F3 totally abrogated Pii immune receptor-dependent resistance, but had no effect on Pia- and Pik-dependent resistance. Knockdown levels of OsExo70-F3 but not OsExo70-F2 correlated with reduction of Pii function, suggesting that OsExo70-F3 is specifically involved in Pii-dependent resistance. Under our current experimental conditions, over-expression of AVR-Pii or knockdown of OsExo70-F2 and -F3 genes in rice did not affect the virulence of compatible isolates of M. oryzae. AVR-Pii interaction with OsExo70-F3 appears to play a crucial role in immunity triggered by Pii, suggesting a role for OsExo70 as a decoy or helper in Pii/AVR-Pii interactions. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

The complete genome sequence of Corynebacterium pseudotuberculosis FRC41 isolated from a 12-year-old girl with necrotizing lymphadenitis reveals insights into gene-regulatory networks contributing to virulence

PubMed Central

2010-01-01

Background Corynebacterium pseudotuberculosis is generally regarded as an important animal pathogen that rarely infects humans. Clinical strains are occasionally recovered from human cases of lymphadenitis, such as C. pseudotuberculosis FRC41 that was isolated from the inguinal lymph node of a 12-year-old girl with necrotizing lymphadenitis. To detect potential virulence factors and corresponding gene-regulatory networks in this human isolate, the genome sequence of C. pseudotuberculosis FCR41 was determined by pyrosequencing and functionally annotated. Results Sequencing and assembly of the C. pseudotuberculosis FRC41 genome yielded a circular chromosome with a size of 2,337,913 bp and a mean G+C content of 52.2%. Specific gene sets associated with iron and zinc homeostasis were detected among the 2,110 predicted protein-coding regions and integrated into a gene-regulatory network that is linked with both the central metabolism and the oxidative stress response of FRC41. Two gene clusters encode proteins involved in the sortase-mediated polymerization of adhesive pili that can probably mediate the adherence to host tissue to facilitate additional ligand-receptor interactions and the delivery of virulence factors. The prominent virulence factors phospholipase D (Pld) and corynebacterial protease CP40 are encoded in the genome of this human isolate. The genome annotation revealed additional serine proteases, neuraminidase H, nitric oxide reductase, an invasion-associated protein, and acyl-CoA carboxylase subunits involved in mycolic acid biosynthesis as potential virulence factors. The cAMP-sensing transcription regulator GlxR plays a key role in controlling the expression of several genes contributing to virulence. Conclusion The functional data deduced from the genome sequencing and the extended knowledge of virulence factors indicate that the human isolate C. pseudotuberculosis FRC41 is equipped with a distinct gene set promoting its survival under unfavorable environmental conditions encountered in the mammalian host. PMID:21192786

Vaginal versus Obstetric Infection Escherichia coli Isolates among Pregnant Women: Antimicrobial Resistance and Genetic Virulence Profile.

PubMed

Sáez-López, Emma; Guiral, Elisabet; Fernández-Orth, Dietmar; Villanueva, Sonia; Goncé, Anna; López, Marta; Teixidó, Irene; Pericot, Anna; Figueras, Francesc; Palacio, Montse; Cobo, Teresa; Bosch, Jordi; Soto, Sara M

2016-01-01

Vaginal Escherichia coli colonization is related to obstetric infections and the consequent development of infections in newborns. Ampicillin resistance among E. coli strains is increasing, which is the main choice for treating empirically many obstetric and neonatal infections. Vaginal E. coli strains are very similar to extraintestinal pathogenic E. coli with regards to the virulence factors and the belonging to phylogroup B2. We studied the antimicrobial resistance and the genetic virulence profile of 82 E. coli isolates from 638 vaginal samples and 63 isolated from endometrial aspirate, placental and amniotic fluid samples from pregnant women with obstetric infections. The prevalence of E. coli in the vaginal samples was 13%, which was significant among women with associated risk factors during pregnancy, especially premature preterm rupture of membranes (p<0.0001). Sixty-five percent of the strains were ampicillin-resistant. The E. coli isolates causing obstetric infections showed higher resistance levels than vaginal isolates, particularly for gentamicin (p = 0.001). The most prevalent virulence factor genes were those related to the iron uptake systems revealing clear targets for interventions. More than 50% of the isolates belonged to the virulent B2 group possessing the highest number of virulence factor genes. The ampicillin-resistant isolates had high number of virulence factors primarily related to pathogenicity islands, and the remarkable gentamicin resistance in E. coli isolates from women presenting obstetric infections, the choice of the most appropriate empiric treatment and clinical management of pregnant women and neonates should be carefully made. Taking into account host-susceptibility, the heterogeneity of E. coli due to evolution over time and the geographical area, characterization of E. coli isolates colonizing the vagina and causing obstetric infections in different regions may help to develop interventions and avoid the aetiological link between maternal carriage and obstetric and subsequent puerperal infections.

FNR Regulates the Expression of Important Virulence Factors Contributing to the Pathogenicity of Avian Pathogenic Escherichia coli

PubMed Central

Barbieri, Nicolle L.; Vande Vorde, Jessica A.; Baker, Alison R.; Horn, Fabiana; Li, Ganwu; Logue, Catherine M.; Nolan, Lisa K.

2017-01-01

Avian pathogenic Escherichia coli (APEC) is the etiologic agent of colibacillosis, an important cause of morbidity and mortality in poultry. Though, many virulence factors associated with APEC pathogenicity are known, their regulation remains unclear. FNR (fumarate and nitrate reduction) is a well-known global regulator that works as an oxygen sensor and has previously been described as a virulence regulator in bacterial pathogens. The goal of this study was to examine the role of FNR in the regulation of APEC virulence factors, such as Type I fimbriae, and processes such as adherence and invasion, type VI secretion, survival during oxidative stress, and growth in iron-restricted environments. To accomplish this goal, APEC O1, a well-characterized, highly virulent, and fully sequenced strain of APEC harboring multiple virulence mechanisms, some of which are plasmid-linked, was compared to its FNR mutant for expression of various virulence traits. Deletion of FNR was found to affect APEC O1's adherence, invasion and expression of ompT, a plasmid-encoded outer membrane protein, type I fimbriae, and aatA, encoding an autotransporter. Indeed, the fnr− mutant showed an 8-fold reduction in expression of type I fimbriae and a highly significant (P < 0.0001) reduction in expression of fimA, ompT (plasmid-borne), and aatA. FNR was also found to regulate expression of the type VI secretion system, affecting the expression of vgrG. Further, FNR was found to be important to APEC O1's growth in iron-deficient media and survival during oxidative stress with the mutant showing a 4-fold decrease in tolerance to oxidative stress, as compared to the wild type. Thus, our results suggest that FNR functions as an important regulator of APEC virulence. PMID:28690981

Stenotrophomonas maltophilia isolated from patients exposed to invasive devices in a university hospital in Argentina: molecular typing, susceptibility and detection of potential virulence factors.

PubMed

Alcaraz, Eliana; Garcia, Carlos; Papalia, Mariana; Vay, Carlos; Friedman, Laura; Passerini de Rossi, Beatriz

2018-05-25

The aim of this work was to investigate the presence of selected potential virulence factors, susceptibility and clonal relatedness among 63 Stenotrophomonas maltophilia isolates recovered from patients exposed to invasive devices in a university hospital in Argentina between January 2004 and August 2012. Genetic relatedness was assessed by enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and pulsed-field gel electrophoresis (PFGE). Isolates were characterized by antimicrobial resistance, the presence and/or expression of potential virulence determinants, and virulence in the Galleria mellonella model.Results/Key findings. ERIC-PCR generated 52 fingerprints, and PFGE added another pattern. Resistance to trimethoprim-sulfamethoxazole (6.35 %), levofloxacin (9.52 %) and ciprofloxacin (23.80 %) was detected. All isolates were susceptible to minocycline. All isolates were lipase, protease and siderophore producers, while all but Sm61 formed biofilms. However, 11/63 isolates did not amplify the major extracellular protease-coding gene (stmPr1). Sm61 is an stmPr1-negative isolate, and showed (as did Sm13 and the reference strain K279a) strong proteolysis and siderophore production, and high resistance to hydrogen peroxide. The three isolates were virulent in the G. mellonella model, while Sm10, a low-resistance hydrogen peroxide stmPr1-negative isolate, and weak proteolysis and siderophore producer, was not virulent. This is the first epidemiological study of the clonal relatedness of S. maltophilia clinical isolates in Argentina. Great genomic diversity was observed, and only two small clusters of related S. maltophilia types were found. Minocycline and trimethoprim-sulfamethoxazole were the most active agents. S. maltophilia virulence in the G. mellonella model is multifactorial, and further studies are needed to elucidate the role of each potential virulence factor.

Distribution of pathogenicity island markers and virulence factors in new phylogenetic groups of uropathogenic Escherichia coli isolates.

PubMed

Najafi, Akram; Hasanpour, Mojtaba; Askary, Azam; Aziemzadeh, Masoud; Hashemi, Najmeh

2018-05-01

The present study was aimed at investigating the relationship between the new Clermont's phylogenetic groups, virulence factors, and pathogenicity island markers (PAIs) among uropathogenic Escherichia coli (UPEC) in Iran. This cross-sectional study was carried out on 140 UPEC isolates collected from patients with urinary tract infections in Bushehr, Iran. All isolates were subjected to phylogenetic typing using a new quadruplex-PCR method. The presence of PAI markers and virulence factors in UPEC strains was evaluated by multiplex PCR. The most predominant virulence gene was fimH (85%), followed by iucC (61.4%), papC (38.6%), hlyA (22.1%), cnf-1 (18.6%), afa (10.7%), papG and neuC (each 9.3%), ibeA (3.6%), and sfa/foc (0.7%). The most common phylogenetic group was related to B2 (39.3%), and the least common to A (0.7%). The most prevalent PAI marker was PAI IV536 (77.14%), while markers for PAI III536 (13.57%), PAI IIJ96 (12.86%), and PAI II536 (12.14%) were the least frequent among the UPEC strains. Meanwhile, the PAI IJ96 marker was not detected. There was a significant association between the phylogenetic group B2 and all the studied virulence genes and PAI markers. To our knowledge, this is the first study to compare the relationship between new phylogenetic groups, virulence genes and PAI markers in UPEC strains in Iran. The phylogenetic group B2 was predominantly represented among the studied virulence genes and PAI markers, indicating the preference of particular strains to carry virulence genes.

Mechanisms of disease: Helicobacter pylori virulence factors.

PubMed

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.

Mechanisms of disease: Helicobacter pylori virulence factors

PubMed Central

Yamaoka, Yoshio

2011-01-01

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. PMID:20938460

Virulence from vesicles: Novel mechanisms of host cell injury by Escherichia coli O104:H4 outbreak strain

USDA-ARS?s Scientific Manuscript database

The highly virulent Escherichia coli O104:H4 that caused the large 2011 outbreak of diarrhoea and haemolytic uraemic syndrome secretes blended virulence factors of enterohaemorrhagic and enteroaggregative E. coli, but their secretion pathways are unknown. We demonstrate that the outbreak strain rele...

Dietary L-glutamine supplementation increases Pasteurella multocida burden and the expression of its major virulence factors in mice.

PubMed

Ren, Wenkai; Liu, Shuping; Chen, Shuai; Zhang, Fengmei; Li, Nengzhang; Yin, Jie; Peng, Yuanyi; Wu, Li; Liu, Gang; Yin, Yulong; Wu, Guoyao

2013-10-01

This study was conducted to determine the effects of graded doses of L-glutamine supplementation on the replication and distribution of Pasteurella multocida, and the expression of its major virulence factors in mouse model. Mice were randomly assigned to the basal diet supplemented with 0, 0.5, 1.0 or 2.0 % glutamine. Pasteurella multocida burden was detected in the heart, liver, spleen, lung and kidney after 12 h of P. multocida infection. The expression of major virulence factors, toll-like receptors (TLRs), proinflammatory cytokines (interleukin-1 beta, interleukin-6, and tumor necrosis factor alpha) and anti-oxidative factors (GPX1 and CuZnSOD) was analyzed in the lung and spleen. Dietary 0.5 % glutamine supplementation has little significant effect on these parameters, compared to those with basal diet. However, results showed that a high dose of glutamine supplementation increased the P. multocida burden (P < 0.001) and the expression of its major virulence factors (P < 0.05) as compared to those with a lower dose of supplementation. In the lung, high dose of glutamine supplementation inhibited the proinflammatory responses (P < 0.05) and TLRs signaling (P < 0.05). In the spleen, the effect of glutamine supplementation on different components in TLR signaling depends on glutamine concentration, and high dose of glutamine supplementation activated the proinflammatory response. In conclusion, glutamine supplementation increased P. multocida burden and the expression of its major virulence factors, while affecting the functions of the lung and spleen.

Crystal structure of listeriolysin O reveals molecular details of oligomerization and pore formation

NASA Astrophysics Data System (ADS)

Köster, Stefan; van Pee, Katharina; Hudel, Martina; Leustik, Martin; Rhinow, Daniel; Kühlbrandt, Werner; Chakraborty, Trinad; Yildiz, Özkan

2014-04-01

Listeriolysin O (LLO) is an essential virulence factor of Listeria monocytogenes that causes listeriosis. Listeria monocytogenes owes its ability to live within cells to the pH- and temperature-dependent pore-forming activity of LLO, which is unique among cholesterol-dependent cytolysins. LLO enables the bacteria to cross the phagosomal membrane and is also involved in activation of cellular processes, including the modulation of gene expression or intracellular Ca2+ oscillations. Neither the pore-forming mechanism nor the mechanisms triggering the signalling processes in the host cell are known in detail. Here, we report the crystal structure of LLO, in which we identified regions important for oligomerization and pore formation. Mutants were characterized by determining their haemolytic and Ca2+ uptake activity. We analysed the pore formation of LLO and its variants on erythrocyte ghosts by electron microscopy and show that pore formation requires precise interface interactions during toxin oligomerization on the membrane.

Biochemical Basis for Increased Activity of Ebola Glycoprotein in the 2013-16 Epidemic.

PubMed

Wang, May K; Lim, Sun-Young; Lee, Soo Mi; Cunningham, James M

2017-03-08

Ebola virus (EBOV) infection is characterized by sporadic outbreaks caused by zoonotic transmission. Fixed changes in amino acid sequence, such as A82V in the EBOV glycoprotein (GP) that occurred early in the 2013-16 epidemic, are suspected to confer a selective advantage to the virus. We used biochemical assays of GP function to show that A82V, as well as a polymorphism in residue 544 identified in other outbreaks, enhances infection by decreasing the threshold for activation of membrane fusion activity triggered by the host factors cathepsin B and Niemann-Pick C1. Importantly, the increase in infectivity comes with the cost of decreased virus stability. Thus, emergence of a virus GP with altered properties that can affect transmission and virulence may have contributed to the severity and scope of the 2013-16 EBOV epidemic. Copyright © 2017 Elsevier Inc. All rights reserved.

Kefiran protects Caco-2 cells from cytopathic effects induced by Bacillus cereus infection.

PubMed

Medrano, Micaela; Hamet, Maria F; Abraham, Analía G; Pérez, Pablo F

2009-11-01

The aim of this work was to evaluate the ability of kefiran to antagonize cytopathic effects triggered by Bacillus cereus strain B10502 on cultured human enterocytes (Caco-2 cells). Cell damage was evaluated by F-actin labelling, scanning electron microscopy and determination of ratios of necrotic and detached cells. To assess the interaction between kefiran and bacteria or eukaryotic cells, flow cytometric analysis was conducted with FITC-labelled kefiran. Kefiran significantly protected infected cells from cytopathic effects induced by B. cereus such as cell necrosis, F-actin disorganisation and microvilli effacement, although presence of kefiran did not modify the adhesion of microorganisms to cultured human enterocytes. Results could be ascribed to the ability of kefiran to interact with both bacteria and eukaryotic cells thus antagonizing interactions necessary for maximal biological effects. Our findings encourage further research on the use of bacterial exopolysaccharides to antagonize virulence factors associated to direct bacteria-cell interactions.

The role of the cell wall in fungal pathogenesis

PubMed Central

Arana, David M.; Prieto, Daniel; Román, Elvira; Nombela, César; Alonso‐Monge, Rebeca; Pla, Jesús

2009-01-01

Summary Fungal infections are a serious health problem. In recent years, basic research is focusing on the identification of fungal virulence factors as promising targets for the development of novel antifungals. The wall, as the most external cellular component, plays a crucial role in the interaction with host cells mediating processes such as adhesion or phagocytosis that are essential during infection. Specific components of the cell wall (called PAMPs) interact with specific receptors in the immune cell (called PRRs), triggering responses whose molecular mechanisms are being elucidated. We review here the main structural carbohydrate components of the fungal wall (glucan, mannan and chitin), how their biogenesis takes place in fungi and the specific receptors that they interact with. Different model fungal pathogens are chosen to illustrate the functional consequences of this interaction. Finally, the identification of the key components will have important consequences in the future and will allow better approaches to treat fungal infections. PMID:21261926

VISLISI trial, a prospective clinical study allowing identification of a new metalloprotease and putative virulence factor from Staphylococcus lugdunensis.

PubMed

Argemi, X; Prévost, G; Riegel, P; Keller, D; Meyer, N; Baldeyrou, M; Douiri, N; Lefebvre, N; Meghit, K; Ronde Oustau, C; Christmann, D; Cianférani, S; Strub, J M; Hansmann, Y

2017-05-01

Staphylococcus lugdunensis is a coagulase-negative staphylococcus that displays an unusually high virulence rate close to that of Staphylococcus aureus. It also shares phenotypic properties with S. aureus and several studies found putative virulence factors. The objective of the study was to describe the clinical manifestations of S. lugdunensis infections and investigate putative virulence factors. We conducted a prospective study from November 2013 to March 2016 at the University Hospital of Strasbourg. Putative virulence factors were investigated by clumping factor detection, screening for proteolytic activity, and sequence analysis using tandem nano-liquid chromatography-mass spectrometry. In total, 347 positive samples for S. lugdunensis were collected, of which 129 (37.2%) were from confirmed cases of S. lugdunensis infection. Eighty-one of these 129 patients were included in the study. Bone and prosthetic joints (PJI) were the most frequent sites of infection (n=28; 34.6%) followed by skin and soft tissues (n=23; 28.4%). We identified and purified a novel protease secreted by 50 samples (61.7%), most frequently associated with samples from deep infections and PJI (pr 0.97 and pr 0.91, respectively). Protease peptide sequencing by nano-liquid chromatography-mass spectrometry revealed a novel protease bearing 62.42% identity with ShpI, a metalloprotease secreted by Staphylococcus hyicus. This study confirms the pathogenicity of S. lugdunensis, particularly in bone and PJI. We also identified a novel metalloprotease called lugdulysin that may contribute to virulence. Copyright © 2016 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Genome-wide identification of Hfq-regulated small RNAs in the fire blight pathogen Erwinia amylovora discovered small RNAs with virulence regulatory function.

PubMed

Zeng, Quan; Sundin, George W

2014-05-31

Erwinia amylovora is a phytopathogenic bacterium and causal agent of fire blight disease in apples and pears. Although many virulence factors have been characterized, the coordination of expression of these virulence factors in E. amylovora is still not clear. Regulatory small RNAs (sRNAs) are important post-transcriptional regulatory components in bacteria. A large number of sRNAs require the RNA chaperone Hfq for both stability and functional activation. In E. amylovora, Hfq was identified as a major regulator of virulence and various virulence traits. However, information is still lacking about Hfq-dependent sRNAs on a genome scale, including the virulence regulatory functions of these sRNAs in E. amylovora. Using both an RNA-seq analysis and a Rho-independent terminator search, 40 candidate Hfq-dependent sRNAs were identified in E. amylovora. The expression and sizes of 12 sRNAs and the sequence boundaries of seven sRNAs were confirmed by Northern blot and 5' RACE assay respectively. Sequence conservation analysis identified sRNAs conserved only in the Erwinia genus as well as E. amylovora species-specific sRNAs. In addition, a dynamic re-patterning of expression of Hfq-dependent sRNAs was observed at 6 and 12 hours after induction in Hrp-inducing minimal medium. Furthermore, sRNAs that control virulence traits were characterized, among which ArcZ positively controls the type III secretion system (T3SS), amylovoran exopolysaccahride production, biofilm formation, and motility, and negatively modulates attachment while RmaA (Hrs6) and OmrAB both negatively regulate amylovoran production and positively regulate motility. This study has significantly enhanced our understanding of the Hfq-dependent sRNAs in E. amylovora at the genome level. The identification of multiple virulence-regulating sRNAs also suggests that post-transcriptional regulation by sRNAs may play a role in the deployment of virulence factors needed during varying stages of pathogenesis during host invasion by E. amylovora.

Comparative proteomic analysis of Cronobacter sakazakii isolates with different virulences.

PubMed

Du, Xin-jun; Han, Ran; Li, Ping; Wang, Shuo

2015-10-14

Cronobacter is a genus of widespread, opportunistic, foodborne pathogens that can result in serious illnesses in at-risk infants because of their immature immunity and high dependence on powdered formula, which is one of the foods most often contaminated by this pathogen. However, limited information is available regarding the pathogenesis and the specific virulence factors of this species. In this study, the virulences of 42 Cronobacter sakazakii isolates were analyzed by infecting neonatal SD rats. A comparison of the typing patterns of the isolates enabled groups with close relationships but that exhibited distinct pathogenesis to be identified. Among these groups, 2 strains belonging to the same group but showing distinct virulences were selected, and 2-DE was applied to identify differentially expressed proteins, focusing on virulence-related proteins. A total of 111 protein spots were identified using matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF-MS), and 89 were successfully identified. Further analysis suggested that at least 11 of these proteins may be involved in the pathogenesis of this pathogen. Real-time PCR was carried out to further confirm the differential expression pattern of the genes, and the results indicated that the mRNA expression levels were consistent with the protein expression levels. The virulence factors and pathogenesis of Cronobacter are largely unknown. In combination with animal toxicological experiments and subtyping results of C. sakazakii, comparative proteomics analysis was performed to comprehensively evaluate the differentially expressed proteins of two isolates that exhibited distinct virulence but were closely related. These procedures made it possible to identify the virulence-related of factors of Cronobacter. Among the 89 total identified proteins, at least 11 show virulence-related potential. This work provides comprehensive candidates for the further investigation of the pathogenesis of Cronobacter. Copyright © 2015 Elsevier B.V. All rights reserved.

The contribution of Pseudomonas aeruginosa virulence factors and host factors in the establishment of urinary tract infections.

PubMed

Newman, John W; Floyd, Rachel V; Fothergill, Joanne L

2017-08-15

Pseudomonas aeruginosa can cause complicated urinary tract infections, particularly in people with catheters, which can lead to pyelonephritis. Whilst some subgroups appear more susceptible to infection, such as the elderly and women, the contribution of other host factors and bacterial virulence factors to successful infection remains relatively understudied. In this review, we explore the potential role of P. aeruginosa virulence factors including phenazines, quorum sensing, biofilm formation and siderophores along with host factors such as Tamm-Horsfall protein, osmotic stress and iron specifically on establishment of successful infection in the urinary niche. P. aeruginosa urinary tract infections are highly antibiotic resistant and require costly and intensive treatment. By understanding the infection dynamics of this organism within this specific niche, we may be able to identify novel therapeutic strategies to enhance the use of existing antibiotics. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Clumping factor A-mediated virulence during Staphylococcus aureus infection is retained despite fibrinogen depletion.

PubMed

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.

The CpxRA two-component system contributes to Legionella pneumophila virulence.

PubMed

Tanner, Jennifer R; Li, Laam; Faucher, Sébastien P; Brassinga, Ann Karen C

2016-06-01

The bacterium Legionella pneumophila is capable of intracellular replication within freshwater protozoa as well as human macrophages, the latter of which results in the serious pneumonia Legionnaires' disease. A primary factor involved in these host cell interactions is the Dot/Icm Type IV secretion system responsible for translocating effector proteins needed to establish and maintain the bacterial replicative niche. Several regulatory factors have been identified to control the expression of the Dot/Icm system and effectors, one of which is the CpxRA two-component system, suggesting essentiality for virulence. In this study, we generated cpxR, cpxA and cpxRA in-frame null mutant strains to further delineate the role of the CpxRA system in bacterial survival and virulence. We found that cpxR is essential for intracellular replication within Acanthamoeba castellanii, but not in U937-derived macrophages. Transcriptome analysis revealed that CpxRA regulates a large number of virulence-associated proteins including Dot/Icm effectors as well as Type II secreted substrates. Furthermore, the cpxR and cpxRA mutant strains were more sodium resistant than the parental strain Lp02, and cpxRA expression reaches maximal levels during postexponential phase. Taken together, our findings suggest the CpxRA system is a key contributor to L. pneumophila virulence in protozoa via virulence factor regulation. © 2016 John Wiley & Sons Ltd.

Metabolism of the vacuolar pathogen Legionella and implications for virulence

PubMed Central

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. PMID:25250244

Effective tolerance based on resource reallocation is a virus-specific defence in Arabidopsis thaliana.

PubMed

Shukla, Aayushi; Pagán, Israel; García-Arenal, Fernando

2018-06-01

Plant viruses often harm their hosts, which have developed mechanisms to prevent or minimize the effects of virus infection. Resistance and tolerance are the two main plant defences to pathogens. Although resistance to plant viruses has been studied extensively, tolerance has received much less attention. Theory predicts that tolerance to low-virulent parasites would be achieved through resource reallocation from growth to reproduction, whereas tolerance to high-virulent parasites would be attained through shortening of the pre-reproductive period. We have shown previously that the tolerance of Arabidopsis thaliana to Cucumber mosaic virus (CMV), a relatively low-virulent virus in this host, accords to these predictions. However, whether other viruses trigger the same response, and how A. thaliana copes with highly virulent virus infections remains unexplored. To address these questions, we challenged six A. thaliana wild genotypes with five viruses with different genomic structures, life histories and transmission modes. In these plants, we quantified virus multiplication, virulence, and the effects of infection on plant growth and reproduction, and on the developmental schedule. Our results indicate that virus multiplication varies according to the virus × host genotype interaction. Conversely, effective tolerance is observed only on CMV infection, and is associated with resource reallocation from growth to reproduction. Tolerance to the other viruses is observed only in specific host-virus combinations and, at odds with theoretical predictions, is linked to longer pre-reproductive periods. These findings only partially agree with theoretical predictions, and contribute to a better understanding of pathogenic processes in plant-virus interactions. © 2017 BSPP AND JOHN WILEY & SONS LTD.

Involvement of the Electrophilic Isothiocyanate Sulforaphane in Arabidopsis Local Defense Responses1

PubMed Central

Andersson, Mats X.; Nilsson, Anders K.; Johansson, Oskar N.; Boztaş, Gülin; Adolfsson, Lisa E.; Pinosa, Francesco; Petit, Christel Garcia; Aronsson, Henrik; Mackey, David; Tör, Mahmut; Hamberg, Mats; Ellerström, Mats

2015-01-01

Plants defend themselves against microbial pathogens through a range of highly sophisticated and integrated molecular systems. Recognition of pathogen-secreted effector proteins often triggers the hypersensitive response (HR), a complex multicellular defense reaction where programmed cell death of cells surrounding the primary site of infection is a prominent feature. Even though the HR was described almost a century ago, cell-to-cell factors acting at the local level generating the full defense reaction have remained obscure. In this study, we sought to identify diffusible molecules produced during the HR that could induce cell death in naive tissue. We found that 4-methylsulfinylbutyl isothiocyanate (sulforaphane) is released by Arabidopsis (Arabidopsis thaliana) leaf tissue undergoing the HR and that this compound induces cell death as well as primes defense in naive tissue. Two different mutants impaired in the pathogen-induced accumulation of sulforaphane displayed attenuated programmed cell death upon bacterial and oomycete effector recognition as well as decreased resistance to several isolates of the plant pathogen Hyaloperonospora arabidopsidis. Treatment with sulforaphane provided protection against a virulent H. arabidopsidis isolate. Glucosinolate breakdown products are recognized as antifeeding compounds toward insects and recently also as intracellular signaling and bacteriostatic molecules in Arabidopsis. The data presented here indicate that these compounds also trigger local defense responses in Arabidopsis tissue. PMID:25371552

Characterisation of virulence genes in methicillin susceptible and resistant Staphylococcus aureus isolates from a paediatric population in a university hospital of Medellín, Colombia.

PubMed

Jiménez, Judy Natalia; Ocampo, Ana María; Vanegas, Johanna Marcela; Rodríguez, Erika Andrea; Garcés, Carlos Guillermo; Patiño, Luz Adriana; Ospina, Sigifredo; Correa, Margarita María

2011-12-01

Virulence and antibiotic resistance are significant determinants of the types of infections caused by Staphylococcus aureus and paediatric groups remain among the most commonly affected populations. The goal of this study was to characterise virulence genes of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains isolated from a paediatric population of a Colombian University Hospital during 2009. Sixty MSSA and MRSA isolates were obtained from paediatric patients between zero-14 years. We identified the genes encoding virulence factors, which included Panton-Valentine leucocidine (PVL), staphylococcal enterotoxins A-E, exfoliative toxins A and B and toxic shock syndrome toxin 1. Typing of the staphylococcal chromosome cassette mec (SCCmec) was performed in MRSA strains. The virulence genes were more diverse and frequent in MSSA than in MRSA isolates (83% vs. 73%). MRSA strains harboured SCCmec types IVc (60%), I (30%), IVa (7%) and V (3%). SCCmec type IVc isolates frequently carried the PVL encoding genes and harboured virulence determinants resembling susceptible strains while SCCmec type I isolates were often negative. PVL was not exclusive to skin and soft tissue infections. As previously suggested, these differences in the distribution of virulence factor genes may be due to the fitness cost associated with methicillin resistance.

Bicarbonate increases binding affinity of Vibrio cholerae ToxT to virulence gene promoters.

PubMed

Thomson, Joshua J; Withey, Jeffrey H

2014-11-01

The major Vibrio cholerae virulence gene transcription activator, ToxT, is responsible for the production of the diarrhea-inducing cholera toxin (CT) and the major colonization factor, toxin coregulated pilus (TCP). In addition to the two primary virulence factors mentioned, ToxT is responsible for the activation of accessory virulence genes, such as aldA, tagA, acfA, acfD, tcpI, and tarAB. ToxT activity is negatively modulated by bile and unsaturated fatty acids found in the upper small intestine. Conversely, previous work identified another intestinal signal, bicarbonate, which enhances the ability of ToxT to activate production of CT and TCP. The work presented here further elucidates the mechanism for the enhancement of ToxT activity by bicarbonate. Bicarbonate was found to increase the activation of ToxT-dependent accessory virulence promoters in addition to those that produce CT and TCP. Bicarbonate is taken up into the V. cholerae cell, where it positively affects ToxT activity by increasing DNA binding affinity for the virulence gene promoters that ToxT activates regardless of toxbox configuration. The increase in ToxT binding affinity in the presence of bicarbonate explains the elevated level of virulence gene transcription. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Unprecedented Abundance of Protein Tyrosine Phosphorylation Modulates Shigella flexneri Virulence.

PubMed

Standish, Alistair James; Teh, Min Yan; Tran, Elizabeth Ngoc Hoa; Doyle, Matthew Thomas; Baker, Paul J; Morona, Renato

2016-10-09

Evidence is accumulating that protein tyrosine phosphorylation plays a crucial role in the ability of important human bacterial pathogens to cause disease. While most works have concentrated on its role in the regulation of a major bacterial virulence factor, the polysaccharide capsule, recent studies have suggested a much broader role for this post-translational modification. This prompted us to investigate protein tyrosine phosphorylation in the human pathogen Shigella flexneri. We first completed a tyrosine phosphoproteome, identifying 905 unique tyrosine phosphorylation sites on at least 573 proteins (approximately 15% of all proteins). This is the most tyrosine-phosphorylated sites and proteins in a single bacterium identified to date, substantially more than the level seen in eukaryotic cells. Most had not previously been identified and included proteins encoded by the virulence plasmid, which is essential for S. flexneri to invade cells and cause disease. In order to investigate the function of these phosphorylation sites in important virulence factors, phosphomimetic and ablative mutations were constructed in the type 3 secretion system ATPase Spa47 and the master virulence regulator VirB. This revealed that tyrosine residues phosphorylated in our study are critical for Spa47 and VirB activity, and tyrosine phosphorylation likely regulates their functional activity and subsequently the virulence of this major human pathogen. This study suggests that tyrosine phosphorylation plays a critical role in regulating a wide variety of virulence factors in the human pathogen S. flexneri and serves as a base for future studies defining its complete role. Copyright © 2016 Elsevier Ltd. All rights reserved.

Functional and Structural Properties of a Novel Protein and Virulence Factor (Protein sHIP) in Streptococcus pyogenes *

PubMed Central

Wisniewska, Magdalena; Happonen, Lotta; Kahn, Fredrik; Varjosalo, Markku; Malmström, Lars; Rosenberger, George; Karlsson, Christofer; Cazzamali, Giuseppe; Pozdnyakova, Irina; Frick, Inga-Maria; Björck, Lars; Streicher, Werner; Malmström, Johan; Wikström, Mats

2014-01-01

Streptococcus pyogenes is a significant bacterial pathogen in the human population. The importance of virulence factors for the survival and colonization of S. pyogenes is well established, and many of these factors are exposed to the extracellular environment, enabling bacterial interactions with the host. In the present study, we quantitatively analyzed and compared S. pyogenes proteins in the growth medium of a strain that is virulent to mice with a non-virulent strain. Particularly, one of these proteins was present at significantly higher levels in stationary growth medium from the virulent strain. We determined the three-dimensional structure of the protein that showed a unique tetrameric organization composed of four helix-loop-helix motifs. Affinity pull-down mass spectrometry analysis in human plasma demonstrated that the protein interacts with histidine-rich glycoprotein (HRG), and the name sHIP (streptococcal histidine-rich glycoprotein-interacting protein) is therefore proposed. HRG has antibacterial activity, and when challenged by HRG, sHIP was found to rescue S. pyogenes bacteria. This and the finding that patients with invasive S. pyogenes infection respond with antibody production against sHIP suggest a role for the protein in S. pyogenes pathogenesis. PMID:24825900

From grazing resistance to pathogenesis: the coincidental evolution of virulence factors.

PubMed

Adiba, Sandrine; Nizak, Clément; van Baalen, Minus; Denamur, Erick; Depaulis, Frantz

2010-08-11

To many pathogenic bacteria, human hosts are an evolutionary dead end. This begs the question what evolutionary forces have shaped their virulence traits. Why are these bacteria so virulent? The coincidental evolution hypothesis suggests that such virulence factors result from adaptation to other ecological niches. In particular, virulence traits in bacteria might result from selective pressure exerted by protozoan predator. Thus, grazing resistance may be an evolutionarily exaptation for bacterial pathogenicity. This hypothesis was tested by subjecting a well characterized collection of 31 Escherichia coli strains (human commensal or extra-intestinal pathogenic) to grazing by the social haploid amoeba Dictyostelium discoideum. We then assessed how resistance to grazing correlates with some bacterial traits, such as the presence of virulence genes. Whatever the relative population size (bacteria/amoeba) for a non-pathogenic bacteria strain, D. discoideum was able to phagocytise, digest and grow. In contrast, a pathogenic bacterium strain killed D. discoideum above a certain bacteria/amoeba population size. A plating assay was then carried out using the E. coli collection faced to the grazing of D. discoideum. E. coli strains carrying virulence genes such as iroN, irp2, fyuA involved in iron uptake, belonging to the B2 phylogenetic group and being virulent in a mouse model of septicaemia were resistant to the grazing from D. discoideum. Experimental proof of the key role of the irp gene in the grazing resistance was evidenced with a mutant strain lacking this gene. Such determinant of virulence may well be originally selected and (or) further maintained for their role in natural habitat: resistance to digestion by free-living protozoa, rather than for virulence per se.

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

PubMed Central

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

Identification of pathogenic factors potentially involved in Staphylococcus aureus keratitis using proteomics.

PubMed

Khan, Shamila; Cole, Nerida; Hume, Emma B H; Garthwaite, Linda L; Nguyen-Khuong, Terry; Walsh, Bradley J; Willcox, Mark D P

2016-10-01

Staphylococcus is a leading cause of microbial keratitis, characterized by destruction of the cornea by bacterial exoproteins and host-associated factors. The aim of this study was to compare extracellular and cell-associated proteins produced by two different isolates of S. aureus, a virulent clinical isolate (Staph 38) and a laboratory strain (Staphylococcus aureus 8325-4) of weaker virulence in the mouse keratitis model. Proteins were analyzed using 2D polyacrylamide gel electrophoresis and identified by subsequent mass spectrometry. Activity of staphylococcal adhesins was assessed by allowing strains to bind to various proteins adsorbed onto polymethylmethacrylate squares. Thirteen proteins in the extracellular fraction and eight proteins in the cell-associated fractions after bacterial growth were produced in increased amounts in the clinical isolate Staph 38. Four of these proteins were S. aureus virulence factor adhesins, fibronectin binding protein A, staphopain, glyceraldehyde-3-phosphate dehydrogenase 2 and extracellular adherence protein. The clinical isolate Staph 38 adhered to a greater extent to all mammalian proteins tested, indicating the potential of the adhesins to be active on its surface. Other proteins with increased expression in Staph 38 included potential moonlighting proteins and proteins involved in transcription or translation. This is the first demonstration of the proteome of S. aureus isolates from keratitis. These results indicate that the virulent clinical isolate produces more potentially important virulence factors compared to the less virulent laboratory strain and these may be associated with the ability of a S. aureus strain to cause more severe keratitis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Identification of novel secreted virulence factors from Xylella fastidiosa using a TRV expression system

USDA-ARS?s Scientific Manuscript database

Xylella fastidiosa is a bacterium that causes leaf scorch diseases of agriculturally important crops including grapevines and almonds. Little is known about virulence factors that are necessary for X. fastidiosa to grow and cause disease in the xylem vessels of a plant host. Any protein secreted by ...

SNARE-encoding genes VdSec22 and VdSso1 mediate protein secretion required for full virulence in Verticillium dahliae

USDA-ARS?s Scientific Manuscript database

Proteins that mediate cellular and subcellular membrane fusion are key factors in vesicular trafficking in all eukaryotic cells, including the secretion and transport of plant pathogen virulence factors. In this study, we identified vesicle fusion components that included 22 soluble N-ethylmaleimide...

Evolutionary insights from Erwinia amylovora genomics.

PubMed

Smits, Theo H M; Rezzonico, Fabio; Duffy, Brion

2011-08-20

Evolutionary genomics is coming into focus with the recent availability of complete sequences for many bacterial species. A hypothesis on the evolution of virulence factors in the plant pathogen Erwinia amylovora, the causative agent of fire blight, was generated using comparative genomics with the genomes E. amylovora, Erwinia pyrifoliae and Erwinia tasmaniensis. Putative virulence factors were mapped to the proposed genealogy of the genus Erwinia that is based on phylogenetic and genomic data. Ancestral origin of several virulence factors was identified, including levan biosynthesis, sorbitol metabolism, three T3SS and two T6SS. Other factors appeared to have been acquired after divergence of pathogenic species, including a second flagellar gene and two glycosyltransferases involved in amylovoran biosynthesis. E. amylovora singletons include 3 unique T3SS effectors that may explain differential virulence/host ranges. E. amylovora also has a unique T1SS export system, and a unique third T6SS gene cluster. Genetic analysis revealed signatures of foreign DNA suggesting that horizontal gene transfer is responsible for some of these differential features between the three species. Copyright © 2010 Elsevier B.V. All rights reserved.

Virulence factors and antimicrobial resistance of escherichia coli isolated from urinary tract of swine in southern of Brazil

PubMed Central

da Costa, Mateus Matiuzzi; Drescher, Guilherme; Maboni, Franciele; Weber, Shana; de Avila Botton, Sônia; Vainstein, Marilene Henning; Schrank, Irene Silveira; de Vargas, Agueda Castagna

2008-01-01

The present study determined the molecular and resistance patterns of E. coli isolates from urinary tract of swine in Southern of Brazil. Molecular characterization of urinary vesicle samples was performed by PCR detection of virulence factors from ETEC, STEC and UPEC. From a total of 82 E. coli isolates, 34 (38.63%) harbored one or more virulence factors. The frequency of virulence factors genes detected by PCR were: pap (10.97%), hlyA (10.97%), iha (9.75%), lt (8.53%), sta (7.31%) sfa (6.09%), f4 (4.87%), f5 (4.87%), stb (4.87%), f6 (1.21%) and f41 (1.21%). Isolates were resistant to penicillin (95.12%), lincomycin (93.9%), erythromycin (92.68%), tetracycline (90.24%), amoxicillin (82.92%), ampicillin (74.39%), josamycin (79.26%), norfloxacin (58.53%), enrofloxacin (57.31%), gentamicin (39.02%), neomycin (37.8%), apramycin (30.48%), colistine (30.48%) and cefalexin (6.09%). A number of 32 (39.02%) E. coli isolates harbored plasmids. PMID:24031300

Virulence Factors of Erwinia amylovora: A Review.

PubMed

Piqué, Núria; Miñana-Galbis, David; Merino, Susana; Tomás, Juan M

2015-06-05

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.

Environmental signals modulate ToxT-dependent virulence factor expression in Vibrio cholerae.

PubMed

Schuhmacher, D A; Klose, K E

1999-03-01

The regulatory protein ToxT directly activates the transcription of virulence factors in Vibrio cholerae, including cholera toxin (CT) and the toxin-coregulated pilus (TCP). Specific environmental signals stimulate virulence factor expression by inducing the transcription of toxT. We demonstrate that transcriptional activation by the ToxT protein is also modulated by environmental signals. ToxT expressed from an inducible promoter activated high-level expression of CT and TCP in V. cholerae at 30 degrees C, but expression of CT and TCP was significantly decreased or abolished by the addition of 0.4% bile to the medium and/or an increase of the temperature to 37 degrees C. Also, expression of six ToxT-dependent TnphoA fusions was modulated by temperature and bile. Measurement of ToxT-dependent transcription of genes encoding CT and TCP by ctxAp- and tcpAp-luciferase fusions confirmed that negative regulation by 37 degrees C or bile occurs at the transcriptional level in V. cholerae. Interestingly, ToxT-dependent transcription of these same promoters in Salmonella typhimurium was relatively insensitive to regulation by temperature or bile. These data are consistent with ToxT transcriptional activity being modulated by environmental signals in V. cholerae and demonstrate an additional level of complexity governing the expression of virulence factors in this pathogen. We propose that negative regulation of ToxT-dependent transcription by environmental signals prevents the incorrect temporal and spatial expression of virulence factors during cholera pathogenesis.

Prevalence, identification of virulence factors, O-serogroups and antibiotic resistance properties of Shiga-toxin producing Escherichia coli strains isolated from raw milk and traditional dairy products.

PubMed

Ranjbar, Reza; Safarpoor Dehkordi, Farhad; Sakhaei Shahreza, Mohammad Hossein; Rahimi, Ebrahim

2018-01-01

Shiga-toxigenic Escherichia coli strains are one of the most important foodborne bacteria with an emergence of antibiotic resistance. Foodborne STEC strains are mainly associated with presence of certain virulence factors and O-seogroups. The present investigation was done to study the distribution of virulence factors, O-serogroups and antibiotic resistance properties of Shiga-toxigenic Escherichia coli isolated from milk and dairy products. Six-hundred samples were randomly collected and immediately transferred to laboratory. All samples were cultured and E. coli strains were isolated. STEC strains were identified based on the presence of putative virulence factors and subtypes. STEC isolates were subjected to multiplex PCR and disk diffusion methods. One-hundred and eighty-one out of 600 samples (30.16%) harbored E. coli . Prevalence of STEC strains was 10.66%. O157 (43.75%) and O26 (37.50%) were the most frequently identified serogroups. Aac(3)-IV (100%), CITM (96.87%) and tetA (76.56%) were the most commonly detected antibiotic resistance genes. STEC strains had the highest prevalence of resistance against ampicillin (100%), gentamicin (100%) and tetracycline (96.87%). Kashk and dough were negative for presence of E. coli strains. High prevalence of resistant-O157 strains and simultaneous presence of multiple virulence factors pose an important public health problem regarding the consumption of raw milk and dairy products.

Diversification of the function of cell-to-cell signaling in regulation of virulence within plant pathogenic xanthomonads.

PubMed

Dow, Max

2008-05-27

The virulence of plant pathogenic bacteria belonging to the genera Xanthomonas and Xylella depends upon cell-to-cell signaling mediated by the diffusible signal molecule DSF (Diffusible Signaling Factor). Synthesis and perception of the DSF signal require products of the rpf gene cluster. The synthesis of DSF depends on RpfF, whereas the RpfC/RpfG two-component system is implicated in DSF perception and signal transduction. The sensor RpfC acts to negatively regulate synthesis of DSF. In Xanthomonas campestris, mutation of rpfF or rpfC leads to a coordinate down-regulation in synthesis of virulence factors and a reduction in virulence. In contrast, in Xylella fastidiosa, the causal agent of Pierce's disease of grape, mutation of rpfF and rpfC have opposite effects on virulence, with rpfF mutants exhibiting a hypervirulent phenotype. The findings suggest that different xanthomonads have adapted the perception and function of similar types of signaling molecule to fit the specific needs for colonization of different hosts.

Uncovering the components of the Francisella tularensis virulence stealth strategy

PubMed Central

Jones, Bradley D.; Faron, Matthew; Rasmussen, Jed A.; Fletcher, Joshua R.

2014-01-01

Over the last decade, studies on the virulence of the highly pathogenic intracellular bacterial pathogen Francisella tularensis have increased dramatically. The organism produces an inert LPS, a capsule, escapes the phagosome to grow in the cytosol (FPI genes mediate phagosomal escape) of a variety of host cell types that include epithelial, endothelial, dendritic, macrophage, and neutrophil. This review focuses on the work that has identified and characterized individual virulence factors of this organism and we hope to highlight how these factors collectively function to produce the pathogenic strategy of this pathogen. In addition, several recent studies have been published characterizing F. tularensis mutants that induce host immune responses not observed in wild type F. tularensis strains that can induce protection against challenge with virulent F. tularensis. As more detailed studies with attenuated strains are performed, it will be possible to see how host models develop acquired immunity to Francisella. Collectively, detailed insights into the mechanisms of virulence of this pathogen are emerging that will allow the design of anti-infective strategies. PMID:24639953

Deoxynivalenol: A Major Player in the Multifaceted Response of Fusarium to Its Environment

PubMed Central

Audenaert, Kris; Vanheule, Adriaan; Höfte, Monica; Haesaert, Geert

2013-01-01

The mycotoxin deoxynivalenol (DON), produced by several Fusarium spp., acts as a virulence factor and is essential for symptom development after initial wheat infection. Accumulating evidence shows that the production of this secondary metabolite can be triggered by diverse environmental and cellular signals, implying that it might have additional roles during the life cycle of the fungus. Here, we review data that position DON in the saprophytic fitness of Fusarium, in defense and in the primary C and N metabolism of the plant and the fungus. We combine the available information in speculative models on the role of DON throughout the interaction with the host, providing working hypotheses that await experimental validation. We also highlight the possible impact of control measures in the field on DON production and summarize the influence of abiotic factors during processing and storage of food and feed matrices. Altogether, we can conclude that DON is a very important compound for Fusarium to cope with a changing environment and to assure its growth, survival, and production of toxic metabolites in diverse situations. PMID:24451843

Targeted Deletion of a Plasmodium Site-2 Protease Impairs Life Cycle Progression in the Mammalian Host

PubMed Central

Goulielmaki, Evi; Chalari, Anna; Withers-Martinez, Chrislaine; Siden-Kiamos, Inga; Matuschewski, Kai

2017-01-01

Site-2 proteases (S2P) belong to the M50 family of metalloproteases, which typically perform essential roles by mediating activation of membrane–bound transcription factors through regulated intramembrane proteolysis (RIP). Protease-dependent liberation of dormant transcription factors triggers diverse cellular responses, such as sterol regulation, Notch signalling and the unfolded protein response. Plasmodium parasites rely on regulated proteolysis for controlling essential pathways throughout the life cycle. In this study we examine the Plasmodium-encoded S2P in a murine malaria model and show that it is expressed in all stages of Plasmodium development. Localisation studies by endogenous gene tagging revealed that in all invasive stages the protein is in close proximity to the nucleus. Ablation of PbS2P by reverse genetics leads to reduced growth rates during liver and blood infection and, hence, virulence attenuation. Strikingly, absence of PbS2P was compatible with parasite life cycle progression in the mosquito and mammalian hosts under physiological conditions, suggesting redundant or dispensable roles in vivo. PMID:28107409

Targeted Deletion of a Plasmodium Site-2 Protease Impairs Life Cycle Progression in the Mammalian Host.

PubMed

Koussis, Konstantinos; Goulielmaki, Evi; Chalari, Anna; Withers-Martinez, Chrislaine; Siden-Kiamos, Inga; Matuschewski, Kai; Loukeris, Thanasis G

2017-01-01

Site-2 proteases (S2P) belong to the M50 family of metalloproteases, which typically perform essential roles by mediating activation of membrane-bound transcription factors through regulated intramembrane proteolysis (RIP). Protease-dependent liberation of dormant transcription factors triggers diverse cellular responses, such as sterol regulation, Notch signalling and the unfolded protein response. Plasmodium parasites rely on regulated proteolysis for controlling essential pathways throughout the life cycle. In this study we examine the Plasmodium-encoded S2P in a murine malaria model and show that it is expressed in all stages of Plasmodium development. Localisation studies by endogenous gene tagging revealed that in all invasive stages the protein is in close proximity to the nucleus. Ablation of PbS2P by reverse genetics leads to reduced growth rates during liver and blood infection and, hence, virulence attenuation. Strikingly, absence of PbS2P was compatible with parasite life cycle progression in the mosquito and mammalian hosts under physiological conditions, suggesting redundant or dispensable roles in vivo.

Signature Motifs Identify an Acinetobacter Cif Virulence Factor with Epoxide Hydrolase Activity*

PubMed Central

Bahl, Christopher D.; Hvorecny, Kelli L.; Bridges, Andrew A.; Ballok, Alicia E.; Bomberger, Jennifer M.; Cady, Kyle C.; O'Toole, George A.; Madden, Dean R.

2014-01-01

Endocytic recycling of the cystic fibrosis transmembrane conductance regulator (CFTR) is blocked by the CFTR inhibitory factor (Cif). Originally discovered in Pseudomonas aeruginosa, Cif is a secreted epoxide hydrolase that is transcriptionally regulated by CifR, an epoxide-sensitive repressor. In this report, we investigate a homologous protein found in strains of the emerging nosocomial pathogens Acinetobacter nosocomialis and Acinetobacter baumannii (“aCif”). Like Cif, aCif is an epoxide hydrolase that carries an N-terminal secretion signal and can be purified from culture supernatants. When applied directly to polarized airway epithelial cells, mature aCif triggers a reduction in CFTR abundance at the apical membrane. Biochemical and crystallographic studies reveal a dimeric assembly with a stereochemically conserved active site, confirming our motif-based identification of candidate Cif-like pathogenic EH sequences. Furthermore, cif expression is transcriptionally repressed by a CifR homolog (“aCifR”) and is induced in the presence of epoxides. Overall, this Acinetobacter protein recapitulates the essential attributes of the Pseudomonas Cif system and thus may facilitate airway colonization in nosocomial lung infections. PMID:24474692

The bias of experimental design, including strain background, in the determination of critical Streptococcus suis serotype 2 virulence factors

PubMed Central

Auger, Jean-Philippe; Chuzeville, Sarah; Roy, David; Mathieu-Denoncourt, Annabelle; Xu, Jianguo; Grenier, Daniel

2017-01-01

Streptococcus suis serotype 2 is an important porcine bacterial pathogen and emerging zoonotic agent mainly responsible for sudden death, septic shock, and meningitis. However, serotype 2 strains are genotypically and phenotypically heterogeneous. Though a multitude of virulence factors have been described for S. suis serotype 2, the lack of a clear definition regarding which ones are truly “critical” has created inconsistencies that have only recently been highlighted. Herein, the involvement of two factors previously described as being critical for S. suis serotype 2 virulence, whether the dipeptidyl peptidase IV and autolysin, were evaluated with regards to different ascribed functions using prototype strains belonging to important sequence types. Results demonstrate a lack of reproducibility with previously published data. In fact, the role of the dipeptidyl peptidase IV and autolysin as critical virulence factors could not be confirmed. Though certain in vitro functions may be ascribed to these factors, their roles are not unique for S. suis, probably due to compensation by other factors. As such, variations and discrepancies in experimental design, including in vitro assays, cell lines, and animal models, are an important source of differences between results. Moreover, the use of different sequence types in this study demonstrates that the role attributed to a virulence factor may vary according to the S. suis serotype 2 strain background. Consequently, it is necessary to establish standard experimental designs according to the experiment and purpose in order to facilitate comparison between laboratories. Alongside, studies should include strains of diverse origins in order to prevent erroneous and biased conclusions that could affect future studies. PMID:28753679

Pathogenicity of Vibrio parahaemolyticus in Different Food Matrices.

PubMed

Wang, Rundong; Sun, Lijun; Wang, Yaling; Deng, Yijia; Liu, Ying; Xu, Defeng; Liu, Huanming; Ye, Riying; Gooneratne, Ravi

2016-02-01

The pathogenicity and virulence factors of Vibrio parahaemolyticus in four food matrices--shrimp, freshwater fish, pork, and egg-fried rice--were compared by measuring the thermostable direct hemolysin activity and total hemolytic titer. Significantly high thermostable direct hemolysin and also hemolytic titers (P < 0.05) were produced by V. parahaemolyticus in egg-fried rice > shrimp > freshwater fish > pork. Filtrates of V. parahaemolyticus in shrimp given intraperitoneally induced marked liver and kidney damage and were highly lethal to adult mice compared with filtrates of V. parahaemolyticus in freshwater fish > egg-fried rice > pork. From in vitro and in vivo pathogenicity tests, it seems the type of food matrix has a significant impact on the virulence of V. parahaemolyticus. These results suggest that hemolysin may not necessarily be the only virulence factor for pathogenicity of V. parahaemolyticus. This is the first report that shows that virulence factors produced by V. parahaemolyticus in seafood such as shrimp are more toxic in vivo than in nonseafood.

Salmonella-secreted Virulence Factors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heffron, Fred; Niemann, George; Yoon, Hyunjin

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. Excellentmore » 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.« less

Helicobacter pylori virulence genes and host genetic polymorphisms as risk factors for peptic ulcer disease.

PubMed

Miftahussurur, Muhammad; Yamaoka, Yoshio

2015-01-01

Helicobacter pylori infection plays an important role in the pathogenesis of peptic ulcer disease (PUD). Several factors have been proposed as possible H. pylori virulence determinants; for example, bacterial adhesins and gastric inflammation factors are associated with an increased risk of PUD. However, differences in bacterial virulence factors alone cannot explain the opposite ends of the PUD disease spectrum, that is duodenal and gastric ulcers; presumably, both bacterial and host factors contribute to the differential response. Carriers of the high-producer alleles of the pro-inflammatory cytokines IL-1B, IL-6, IL-8, IL-10, and TNF-α who also carry low-producer allele of anti-inflammatory cytokines have severe gastric mucosal inflammation, whereas carriers of the alternative alleles have mild inflammation. Recent reports have suggested that the PSCA and CYP2C19 ultra-rapid metabolizer genotypes are also associated with PUD.

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

PubMed

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.

Virulence gene content in Escherichia coli isolates from poultry flocks with clinical signs of colibacillosis in Brazil.

PubMed

De Carli, Silvia; Ikuta, Nilo; Lehmann, Fernanda Kieling Moreira; da Silveira, Vinicius Proença; de Melo Predebon, Gabriela; Fonseca, André Salvador Kazantzi; Lunge, Vagner Ricardo

2015-11-01

Escherichia coli is a commensal bacterium of the bird's intestinal tract, but it can invade different tissues resulting in systemic symptoms (colibacillosis). This disease occurs only when the E. coli infecting strain presents virulence factors (encoded by specific genes) that enable the adhesion and proliferation in the host organism. Thus, it is important to differentiate pathogenic (APEC, avian pathogenic E. coli) and non-pathogenic or fecal (AFEC, avian fecal E. coli) isolates. Previous studies analyzed the occurrence of virulence factors in E. coli strains isolated from birds with colibacillosis, demonstrating a high frequency of the bacterial genes cvaC, iroN, iss, iutA, sitA, tsh, fyuA, irp-2, ompT and hlyF in pathogenic strains. The aim of the present study was to evaluate the occurrence and frequency of these virulence genes in E. coli isolated from poultry flocks in Brazil. A total of 138 isolates of E. coli was obtained from samples of different tissues and/or organs (spleen, liver, kidney, trachea, lungs, skin, ovary, oviduct, intestine, cloaca) and environmental swabs collected from chicken and turkey flocks suspected to have colibacillosis in farms from the main Brazilian producing regions. Total DNA was extracted and the 10 virulence genes were detected by traditional and/or real-time PCR. At least 11 samples of each gene were sequenced and compared to reference strains. All 10 virulence factors were detected in Brazilian E. coli isolates, with frequencies ranging from 39.9% (irp-2) to 68.8% (hlyF and sitA). Moreover, a high nucleotide similarity (over 99%) was observed between gene sequences of Brazilian isolates and reference strains. Seventy-nine isolates were defined as pathogenic (APEC) and 59 as fecal (AFEC) based on previously described criteria. In conclusion, the main virulence genes of the reference E. coli strains are also present in isolates associated with colibacillosis in Brazil. The analysis of this set of virulence factors can be used to differentiate between APEC and AFEC isolates in Brazil. © 2015 Poultry Science Association Inc.

A Resource Allocation Trade-Off between Virulence and Proliferation Drives Metabolic Versatility in the Plant Pathogen Ralstonia solanacearum

PubMed Central

Marmiesse, Lucas; Gouzy, Jérôme

2016-01-01

Bacterial pathogenicity relies on a proficient metabolism and there is increasing evidence that metabolic adaptation to exploit host resources is a key property of infectious organisms. In many cases, colonization by the pathogen also implies an intensive multiplication and the necessity to produce a large array of virulence factors, which may represent a significant cost for the pathogen. We describe here the existence of a resource allocation trade-off mechanism in the plant pathogen R. solanacearum. We generated a genome-scale reconstruction of the metabolic network of R. solanacearum, together with a macromolecule network module accounting for the production and secretion of hundreds of virulence determinants. By using a combination of constraint-based modeling and metabolic flux analyses, we quantified the metabolic cost for production of exopolysaccharides, which are critical for disease symptom production, and other virulence factors. We demonstrated that this trade-off between virulence factor production and bacterial proliferation is controlled by the quorum-sensing-dependent regulatory protein PhcA. A phcA mutant is avirulent but has a better growth rate than the wild-type strain. Moreover, a phcA mutant has an expanded metabolic versatility, being able to metabolize 17 substrates more than the wild-type. Model predictions indicate that metabolic pathways are optimally oriented towards proliferation in a phcA mutant and we show that this enhanced metabolic versatility in phcA mutants is to a large extent a consequence of not paying the cost for virulence. This analysis allowed identifying candidate metabolic substrates having a substantial impact on bacterial growth during infection. Interestingly, the substrates supporting well both production of virulence factors and growth are those found in higher amount within the plant host. These findings also provide an explanatory basis to the well-known emergence of avirulent variants in R. solanacearum populations in planta or in stressful environments. PMID:27732672

Differential compartmentalization of Streptococcus pyogenes virulence factors and host protein binding properties as a mechanism for host adaptation.

PubMed

Kilsgård, Ola; Karlsson, Christofer; Malmström, Erik; Malmström, Johan

2016-11-01

Streptococcus pyogenes is an important human pathogen responsible for substantial morbidity and mortality worldwide. Although S. pyogenes is a strictly human pathogen with no other known animal reservoir, several murine infection models exist to explore different aspects of the bacterial pathogenesis. Inoculating mice with wild-type S. pyogenes strains can result in the generation of new bacterial phenotypes that are hypervirulent compared to the original inoculum. In this study, we used a serial mass spectrometry based proteomics strategy to investigate if these hypervirulent strains have an altered distribution of virulence proteins across the intracellular, surface associated and secreted bacterial compartments and if any change in compartmentalization can alter the protein-protein interaction network between bacteria and host proteins. Quantitative analysis of the S. pyogenes surface and secreted proteomes revealed that animal passaged strains are associated with significantly higher amount of virulence factors on the bacterial surface and in the media. This altered virulence factor compartmentalization results in increased binding of several mouse plasma proteins to the bacterial surface, a trend that was consistent for mouse plasma from several different mouse strains. In general, both the wild-type strain and animal passaged strain were capable of binding high amounts of human plasma proteins. However, compared to the non-passaged strains, the animal passaged strains displayed an increased ability to bind mouse plasma proteins, in particular for M protein binders, indicating that the increased affinity for mouse blood plasma proteins is a consequence of host adaptation of this pathogen to a new host. In conclusion, plotting the total amount of virulence factors against the total amount of plasma proteins associated to the bacterial surface could clearly separate out animal passaged strains from wild type strains indicating a virulence model that could predict the virulence of a S. pyogenes strain in mice and which could be used to identify key aspects of this bacteria's pathogenesis. Copyright © 2016 Elsevier GmbH. All rights reserved.

Hemolysin as a Virulence Factor for Systemic Infection with Isolates of Mycobacterium avium Complex

PubMed Central

Maslow, Joel N.; Dawson, David; Carlin, Elizabeth A.; Holland, Steven M.

1999-01-01

Isolates of the Mycobacterium avium complex were examined for hemolysin expression. Only invasive isolates of M. avium were observed to be hemolytic (P < 0.001), with activity the greatest for isolates of serovars 4 and 8. Thus, M. avium hemolysin appears to represent a virulence factor necessary for invasive disease. PMID:9889239

Nontoxigenic Vibrio cholerae Non-O1/O139 Isolate from a Case of Human Gastroenteritis in the U.S. Gulf Coast

PubMed Central

Hasan, Nur A.; Rezayat, Talayeh; Blatz, Peter J.; Choi, Seon Young; Griffitt, Kimberly J.; Rashed, Shah M.; Huq, Anwar; Conger, Nicholas G.; Colwell, Rita R.

2014-01-01

An occurrence of Vibrio cholerae non-O1/O139 gastroenteritis in the U.S. Gulf Coast is reported here. Genomic analysis revealed that the isolate lacked known virulence factors associated with the clinical outcome of a V. cholerae infection but did contain putative genomic islands and other accessory virulence factors. Many of these factors are widespread among environmental strains of V. cholerae, suggesting that there might be additional virulence factors in non-O1/O139 V. cholerae yet to be determined. Phylogenetic analysis revealed that the isolate belonged to a phyletic lineage of environmental V. cholerae isolates associated with sporadic cases of gastroenteritis in the Western Hemisphere, suggesting a need to monitor non-O1/O139 V. cholerae in the interest of public health. PMID:25339398

Klebsiella variicola Is a Frequent Cause of Bloodstream Infection in the Stockholm Area, and Associated with Higher Mortality Compared to K. pneumoniae

PubMed Central

Kabir, Muhammad Humaun; Bakhrouf, Amina; Kalin, Mats; Nauclér, Pontus; Brisse, Sylvain; Giske, Christian G.

2014-01-01

Clinical isolates of Klebsiella pneumoniae are divided into three phylogroups and differ in their virulence factor contents. The aim of this study was to determine an association between phylogroup, virulence factors and mortality following bloodstream infection (BSI) caused by Klebsiella pneumoniae. Isolates from all adult patients with BSI caused by K. pneumoniae admitted to Karolinska University Hospital, Solna between 2007 and 2009 (n = 139) were included in the study. Phylogenetic analysis was performed based on multilocus sequence typing (MLST) data. Testing for mucoid phenotype, multiplex PCR determining serotypes K1, K2, K5, K20, K54 and K57, and testing for virulence factors connected to more severe disease in previous studies, was also performed. Data was retrieved from medical records including age, sex, comorbidity, central and urinary catheters, time to adequate treatment, hospital-acquired infection, and mortality, to identify risk factors. The primary end-point was 30- day mortality. The three K. pneumoniae phylogroups were represented: KpI (n = 96), KpII (corresponding to K. quasipneumoniae, n = 9) and KpIII (corresponding to K. variicola, n = 34). Phylogroups were not significantly different in baseline characteristics. Overall, the 30-day mortality was 24/139 (17.3%). Isolates belonging to KpIII were associated with the highest 30-day mortality (10/34 cases, 29.4%), whereas KpI isolates were associated with mortality in 13/96 cases (13.5%). This difference was significant both in univariate statistical analysis (P = 0.037) and in multivariate analysis adjusting for age and comorbidity (OR 3.03 (95% CI: 1.10–8.36). Only three of the isolates causing mortality within 30 days belonged to any of the virulent serotypes (K54, n = 1), had a mucoid phenotype (n = 1) and/or contained virulence genes (wcaG n = 1 and wcaG/allS n = 1). In conclusion, the results indicate higher mortality among patients infected with isolates belonging to K. variicola. The increased mortality could not be related to any known virulence factors, including virulent capsular types or mucoid phenotype. PMID:25426853

Characterization of virulence factor regulation by SrrAB, a two-component system in Staphylococcus aureus.

PubMed

Pragman, Alexa A; Yarwood, Jeremy M; Tripp, Timothy J; Schlievert, Patrick M

2004-04-01

Workers in our laboratory have previously identified the staphylococcal respiratory response AB (SrrAB), a Staphylococcus aureus two-component system that acts in the global regulation of virulence factors. This system down-regulates production of agr RNAIII, protein A, and toxic shock syndrome toxin 1 (TSST-1), particularly under low-oxygen conditions. In this study we investigated the localization and membrane orientation of SrrA and SrrB, transcription of the srrAB operon, the DNA-binding properties of SrrA, and the effect of SrrAB expression on S. aureus virulence. We found that SrrA is localized to the S. aureus cytoplasm, while SrrB is localized to the membrane and is properly oriented to function as a histidine kinase. srrAB has one transcriptional start site which results in either an srrA transcript or a full-length srrAB transcript; srrB must be cotranscribed with srrA. Gel shift assays of the agr P2, agr P3, protein A (spa), TSST-1 (tst), and srr promoters revealed SrrA binding at each of these promoters. Analysis of SrrAB-overexpressing strains by using the rabbit model of bacterial endocarditis demonstrated that overexpression of SrrAB decreased the virulence of the organisms compared to the virulence of isogenic strains that do not overexpress SrrAB. We concluded that SrrAB is properly localized and oriented to function as a two-component system. Overexpression of SrrAB, which represses agr RNAIII, TSST-1, and protein A in vitro, decreases virulence in the rabbit endocarditis model. Repression of these virulence factors is likely due to a direct interaction between SrrA and the agr, tst, and spa promoters.

Dynamics of Vibrio with virulence genes detected in Pacific harbor seals (Phoca vitulina richardii) off California: implications for marine mammal health.

PubMed

Hughes, Stephanie N; Greig, Denise J; Miller, Woutrina A; Byrne, Barbara A; Gulland, Frances M D; Harvey, James T

2013-05-01

Given their coastal site fidelity and opportunistic foraging behavior, harbor seals (Phoca vitulina) may serve as sentinels for coastal ecosystem health. Seals using urbanized coastal habitat can acquire enteric bacteria, including Vibrio that may affect their health. To understand Vibrio dynamics in seals, demographic and environmental factors were tested for predicting potentially virulent Vibrio in free-ranging and stranded Pacific harbor seals (Phoca vitulina richardii) off California. Vibrio prevalence did not vary with season and was greater in free-ranging seals (29 %, n = 319) compared with stranded seals (17 %, n = 189). Of the factors tested, location, turbidity, and/or salinity best predicted Vibrio prevalence in free-ranging seals. The relationship of environmental factors with Vibrio prevalence differed by location and may be related to oceanographic or terrestrial contributions to water quality. Vibrio parahaemolyticus, Vibrio alginolyticus, and Vibrio cholerae were observed in seals, with V. cholerae found almost exclusively in stranded pups and yearlings. Additionally, virulence genes (trh and tdh) were detected in V. parahaemolyticus isolates. Vibrio cholerae isolates lacked targeted virulence genes, but were hemolytic. Three out of four stranded pups with V. parahaemolyticus (trh+ and/or tdh+) died in rehabilitation, but the role of Vibrio in causing mortality is unclear, and Vibrio expression of virulence genes should be investigated. Considering that humans share the environment and food resources with seals, potentially virulent Vibrio observed in seals also may be of concern to human health.

Gene Overexpression/Suppression Analysis of Candidate Virulence Factors of Candida albicans▿

PubMed Central

Fu, Yue; Luo, Guanpingsheng; Spellberg, Brad J.; Edwards, John E.; Ibrahim, Ashraf S.

2008-01-01

We developed a conditional overexpression/suppression genetic strategy in Candida albicans to enable simultaneous testing of gain or loss of function in order to identify new virulence factors. The strategy involved insertion of a strong, tetracycline-regulated promoter in front of the gene of interest. To validate the strategy, a library of genes encoding glycosylphosphatidylinositol (GPI)-anchored surface proteins was screened for virulence phenotypes in vitro. During the screening, overexpression of IFF4 was found to increase the adherence of C. albicans to plastic and to human epithelial cells, but not endothelial cells. Consistent with the in vitro results, IFF4 overexpression modestly increased the tissue fungal burden during murine vaginal candidiasis. In addition to the in vitro screening tests, IFF4 overexpression was found to increase C. albicans susceptibility to neutrophil-mediated killing. Furthermore, IFF4 overexpression decreased the severity of hematogenously disseminated candidiasis in normal mice, but not in neutropenic mice, again consistent with the in vitro phenotype. Overexpression of 12 other GPI proteins did not affect normal GPI protein cell surface accumulation, demonstrating that the overexpression strategy did not affect the cell capacity for making such proteins. These data indicate that the same gene can increase or decrease candidal virulence in distinct models of infection, emphasizing the importance of studying virulence genes in different anatomical contexts. Finally, these data validate the use of a conditional overexpression/suppression genetic strategy to identify candidal virulence factors. PMID:18178776

Structure-based functional characterization of repressor of toxin (Rot), a central regulator of staphylococcus aureus virulence

DOE PAGES

Killikelly, April; Jakoncic, Jean; Benson, Meredith A.; ...

2014-10-20

Staphylococcus aureus is responsible for a large number of diverse infections worldwide. In order to support its pathogenic lifestyle, S. aureus has to regulate the expression of virulence factors in a coordinated fashion. One of the central regulators of the S. aureus virulence regulatory networks is the transcription factor repressor of toxin (Rot). Rot plays a key role in regulating S. aureus virulence through activation or repression of promoters that control expression of a large number of critical virulence factors. However, the mechanism by which Rot mediates gene regulation has remained elusive. Here, we have determined the crystal structure ofmore » Rot and used this information to probe the contribution made by specific residues to Rot function. Rot was found to form a dimer, with each monomer harboring a winged helix-turn-helix (WHTH) DNA-binding motif. Despite an overall acidic pI, the asymmetric electrostatic charge profile suggests that Rot can orient the WHTH domain to bind DNA. Structure-based site-directed mutagenesis studies demonstrated that R 91, at the tip of the wing, plays an important role in DNA binding, likely through interaction with the minor groove. We also found that Y 66, predicted to bind within the major groove, contributes to Rot interaction with target promoters. Evaluation of Rot binding to different activated and repressed promoters revealed that certain mutations on Rot exhibit promoter-specific effects, suggesting for the first time that Rot differentially interacts with target promoters. As a result, this work provides insight into a precise mechanism by which Rot controls virulence factor regulation in S. aureus.« less

Structure-based functional characterization of repressor of toxin (Rot), a central regulator of staphylococcus aureus virulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Killikelly, April; Jakoncic, Jean; Benson, Meredith A.

Staphylococcus aureus is responsible for a large number of diverse infections worldwide. In order to support its pathogenic lifestyle, S. aureus has to regulate the expression of virulence factors in a coordinated fashion. One of the central regulators of the S. aureus virulence regulatory networks is the transcription factor repressor of toxin (Rot). Rot plays a key role in regulating S. aureus virulence through activation or repression of promoters that control expression of a large number of critical virulence factors. However, the mechanism by which Rot mediates gene regulation has remained elusive. Here, we have determined the crystal structure ofmore » Rot and used this information to probe the contribution made by specific residues to Rot function. Rot was found to form a dimer, with each monomer harboring a winged helix-turn-helix (WHTH) DNA-binding motif. Despite an overall acidic pI, the asymmetric electrostatic charge profile suggests that Rot can orient the WHTH domain to bind DNA. Structure-based site-directed mutagenesis studies demonstrated that R 91, at the tip of the wing, plays an important role in DNA binding, likely through interaction with the minor groove. We also found that Y 66, predicted to bind within the major groove, contributes to Rot interaction with target promoters. Evaluation of Rot binding to different activated and repressed promoters revealed that certain mutations on Rot exhibit promoter-specific effects, suggesting for the first time that Rot differentially interacts with target promoters. As a result, this work provides insight into a precise mechanism by which Rot controls virulence factor regulation in S. aureus.« less

Vibrio parahaemolyticus Inhibition of Rho Family GTPase Activation Requires a Functional Chromosome I Type III Secretion System▿

PubMed Central

Casselli, Timothy; Lynch, Tarah; Southward, Carolyn M.; Jones, Bryan W.; DeVinney, Rebekah

2008-01-01

Vibrio parahaemolyticus is a leading cause of seafood-borne gastroenteritis; however, its virulence mechanisms are not well understood. The identification of type III secreted proteins has provided candidate virulence factors whose functions are still being elucidated. Genotypic strain variability contributes a level of complexity to understanding the role of different virulence factors. The ability of V. parahaemolyticus to inhibit Rho family GTPases and cause cytoskeletal disruption was examined with HeLa cells. After HeLa cells were infected, intracellular Rho activation was inhibited in response to external stimuli. In vitro activation of Rho, Rac, and Cdc42 isolated from infected HeLa cell lysates was also inhibited, indicating that the bacteria were specifically targeting GTPase activation. The inhibition of Rho family GTPase activation was retained for clinical and environmental isolates of V. parahaemolyticus and was dependent on a functional chromosome I type III secretion system (CI-T3SS). GTPase inhibition was independent of hemolytic toxin genotype and the chromasome II (CII)-T3SS. Rho inhibition was accompanied by a shift in the total actin pool to its monomeric form. These phenotypes were abrogated in a mutant strain lacking the CI-T3S effector Vp1686, suggesting that the inhibiting actin polymerization may be a downstream effect of Vp1686-dependent GTPase inhibition. Although Vp1686 has been previously characterized as a potential virulence factor in macrophages, our findings reveal an effect on cultured HeLa cells. The ability to inhibit Rho family GTPases independently of the CII-T3SS and the hemolytic toxins may provide insight into the mechanisms of virulence used by strains lacking these virulence factors. PMID:18347050

Chemical Inhibition of Kynureninase Reduces Pseudomonas aeruginosa Quorum Sensing and Virulence Factor Expression.

PubMed

Kasper, Stephen H; Bonocora, Richard P; Wade, Joseph T; Musah, Rabi Ann; Cady, Nathaniel C

2016-04-15

The opportunistic pathogen Pseudomonas aeruginosa utilizes multiple quorum sensing (QS) pathways to coordinate an arsenal of virulence factors. We previously identified several cysteine-based compounds inspired by natural products from the plant Petiveria alliacea which are capable of antagonizing multiple QS circuits as well as reducing P. aeruginosa biofilm formation. To understand the global effects of such compounds on virulence factor production and elucidate their mechanism of action, RNA-seq transcriptomic analysis was performed on P. aeruginosa PAO1 exposed to S-phenyl-l-cysteine sulfoxide, the most potent inhibitor from the prior study. Exposure to this inhibitor down-regulated expression of several QS-regulated virulence operons (e.g., phenazine biosynthesis, type VI secretion systems). Interestingly, many genes that were differentially regulated pertain to the related metabolic pathways that yield precursors of pyochelin, tricarboxylic acid cycle intermediates, phenazines, and Pseudomonas quinolone signal (PQS). Activation of the MexT-regulon was also indicated, including the multidrug efflux pump encoded by mexEF-oprN, which has previously been shown to inhibit QS and pathogenicity. Deeper investigation of the metabolites involved in these systems revealed that S-phenyl-l-cysteine sulfoxide has structural similarity to kynurenine, a precursor of anthranilate, which is critical for P. aeruginosa virulence. By supplementing exogenous anthranilate, the QS-inhibitory effect was reversed. Finally, it was shown that S-phenyl-l-cysteine sulfoxide competitively inhibits P. aeruginosa kynureninase (KynU) activity in vitro and reduces PQS production in vivo. The kynurenine pathway has been implicated in P. aeruginosa QS and virulence factor expression; however, this is the first study to show that targeted inhibition of KynU affects P. aeruginosa gene expression and QS, suggesting a potential antivirulence strategy.

Escherichia coli O104:H4 Pathogenesis: an Enteroaggregative E. coli/Shiga Toxin-Producing E. coli Explosive Cocktail of High Virulence.

PubMed

Navarro-Garcia, Fernando

2014-12-01

A major outbreak caused by Escherichia coli of serotype O104:H4 spread throughout Europe in 2011. This large outbreak was caused by an unusual strain that is most similar to enteroaggregative E. coli (EAEC) of serotype O104:H4. A significant difference, however, is the presence of a prophage encoding the Shiga toxin, which is characteristic of enterohemorrhagic E. coli (EHEC) strains. This combination of genomic features, associating characteristics from both EAEC and EHEC, represents a new pathotype. The 2011 E. coli O104:H4 outbreak of hemorrhagic diarrhea in Germany is an example of the explosive cocktail of high virulence and resistance that can emerge in this species. A total of 46 deaths, 782 cases of hemolytic-uremic syndrome, and 3,128 cases of acute gastroenteritis were attributed to this new clone of EAEC/EHEC. In addition, recent identification in France of similar O104:H4 clones exhibiting the same virulence factors suggests that the EHEC O104:H4 pathogen has become endemically established in Europe after the end of the outbreak. EAEC strains of serotype O104:H4 contain a large set of virulence-associated genes regulated by the AggR transcription factor. They include, among other factors, the pAA plasmid genes encoding the aggregative adherence fimbriae, which anchor the bacterium to the intestinal mucosa (stacked-brick adherence pattern on epithelial cells). Furthermore, sequencing studies showed that horizontal genetic exchange allowed for the emergence of the highly virulent Shiga toxin-producing EAEC O104:H4 strain that caused the German outbreak. This article discusses the role these virulence factors could have in EAEC/EHEC O104:H4 pathogenesis.

Perturbation of Staphylococcus aureus Gene Expression by the Enoyl-Acyl Carrier Protein Reductase Inhibitor AFN-1252

PubMed Central

Parsons, Joshua B.; Kukula, Maciej; Jackson, Pamela; Pulse, Mark; Simecka, Jerry W.; Valtierra, David; Weiss, William J.; Kaplan, Nachum

2013-01-01

This study examines the alteration in Staphylococcus aureus gene expression following treatment with the type 2 fatty acid synthesis inhibitor AFN-1252. An Affymetrix array study showed that AFN-1252 rapidly increased the expression of fatty acid synthetic genes and repressed the expression of virulence genes controlled by the SaeRS 2-component regulator in exponentially growing cells. AFN-1252 did not alter virulence mRNA levels in a saeR deletion strain or in strain Newman expressing a constitutively active SaeS kinase. AFN-1252 caused a more pronounced increase in fabH mRNA levels in cells entering stationary phase, whereas the depression of virulence factor transcription was attenuated. The effect of AFN-1252 on gene expression in vivo was determined using a mouse subcutaneous granuloma infection model. AFN-1252 was therapeutically effective, and the exposure (area under the concentration-time curve from 0 to 48 h [AUC0–48]) of AFN-1252 in the pouch fluid was comparable to the plasma levels in orally dosed animals. The inhibition of fatty acid biosynthesis by AFN-1252 in the infected pouches was signified by the substantial and sustained increase in fabH mRNA levels in pouch-associated bacteria, whereas depression of virulence factor mRNA levels in the AFN-1252-treated pouch bacteria was not as evident as it was in exponentially growing cells in vitro. The trends in fabH and virulence factor gene expression in the animal were similar to those in slower-growing bacteria in vitro. These data indicate that the effects of AFN-1252 on virulence factor gene expression depend on the physiological state of the bacteria. PMID:23459481

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

PubMed

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 < 0.001). When H. kunzii and S. 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 < 0.001). To evaluate the impact of these strains on host response, transcriptomic analysis showed that the ingestion of S. 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.

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

PubMed Central

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 < 0.001). When H. kunzii and S. 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 < 0.001). To evaluate the impact of these strains on host response, transcriptomic analysis showed that the ingestion of S. 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. PMID:28361041

Virulence of Erwinia amylovora, a prevalent apple pathogen: Outer membrane proteins and type III secreted effectors increase fitness and compromise plant defenses.

PubMed

Holtappels, Michelle; Noben, Jean-Paul; Valcke, Roland

2016-09-01

Until now, no data are available on the outer membrane (OM) proteome of Erwinia amylovora, a Gram-negative plant pathogen, causing fire blight in most of the members of the Rosaceae family. Since the OM forms the interface between the bacterial cell and its environment it is in direct contact with the host. Additionally, the type III secretion system, embedded in the OM, is a pathogenicity factor of E. amylovora. To assess the influence of the OM composition and the secretion behavior on virulence, a 2D-DIGE analysis and gene expression profiling were performed on a high and lower virulent strain, both in vitro and in planta. Proteome data showed an increase in flagellin for the lower virulent strain in vitro, whereas, in planta several interesting proteins were identified as being differently expressed between both the strains. Further, gene expression of nearly all type III secreted effectors was elevated for the higher virulent strain, both in vitro and in planta. As a first, we report that several characteristics of virulence can be assigned to the OM proteome. Moreover, we demonstrate that secreted proteins prove to be the important factors determining differences in virulence between the strains, otherwise regarded as homogeneous on a genome level. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PecS is an important player in the regulatory network governing the coordinated expression of virulence genes during the interaction between Dickeya dadantii 3937 and plants.

PubMed

Mhedbi-Hajri, Nadia; Malfatti, Pierrette; Pédron, Jacques; Gaubert, Stéphane; Reverchon, Sylvie; Van Gijsegem, Frédérique

2011-11-01

Successful infection of a pathogen relies on the coordinated expression of numerous virulence factor-encoding genes. In plant-bacteria interactions, this control is very often achieved through the integration of several regulatory circuits controlling cell-cell communication or sensing environmental conditions. Dickeya dadantii (formerly Erwinia chrysanthemi), the causal agent of soft rot on many crops and ornamentals, provokes maceration of infected plants mainly by producing and secreting a battery of plant cell wall-degrading enzymes. However, several other virulence factors have also been characterized. During Arabidopsis infection, most D. dadantii virulence gene transcripts accumulated in a coordinated manner during infection. This activation requires a functional GacA-GacS two-component regulatory system but the Gac system is not involved in the growth phase dependence of virulence gene expression. Here we show that, contrary to Pectobacterium, the AHL-mediated ExpIR quorum-sensing system does not play a major role in the growth phase-dependent control of D. dadantii virulence genes. On the other hand, the global regulator PecS participates in this coordinated expression since, in a pecS mutant, an early activation of virulence genes is observed both in vitro and in planta. This correlated with the known hypervirulence phenotype of the pecS mutant. Analysis of the relationship between the regulatory circuits governed by the PecS and GacA global regulators indicates that these two regulators act independently. PecS prevents a premature expression of virulence genes in the first stages of colonization whereas GacA, presumably in conjunction with other regulators, is required for the activation of virulence genes at the onset of symptom occurrence. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

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

PubMed

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 .

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

PubMed

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.

Pan-Genomic Analysis Permits Differentiation of Virulent and Non-virulent Strains of Xanthomonas arboricola That Cohabit Prunus spp. and Elucidate Bacterial Virulence Factors

PubMed Central

Garita-Cambronero, Jerson; Palacio-Bielsa, Ana; López, María M.; Cubero, Jaime

2017-01-01

Xanthomonas arboricola is a plant-associated bacterial species that causes diseases on several plant hosts. One of the most virulent pathovars within this species is X. arboricola pv. pruni (Xap), the causal agent of bacterial spot disease of stone fruit trees and almond. Recently, a non-virulent Xap-look-a-like strain isolated from Prunus was characterized and its genome compared to pathogenic strains of Xap, revealing differences in the profile of virulence factors, such as the genes related to the type III secretion system (T3SS) and type III effectors (T3Es). The existence of this atypical strain arouses several questions associated with the abundance, the pathogenicity, and the evolutionary context of X. arboricola on Prunus hosts. After an initial characterization of a collection of Xanthomonas strains isolated from Prunus bacterial spot outbreaks in Spain during the past decade, six Xap-look-a-like strains, that did not clustered with the pathogenic strains of Xap according to a multi locus sequence analysis, were identified. Pathogenicity of these strains was analyzed and the genome sequences of two Xap-look-a-like strains, CITA 14 and CITA 124, non-virulent to Prunus spp., were obtained and compared to those available genomes of X. arboricola associated with this host plant. Differences were found among the genomes of the virulent and the Prunus non-virulent strains in several characters related to the pathogenesis process. Additionally, a pan-genomic analysis that included the available genomes of X. arboricola, revealed that the atypical strains associated with Prunus were related to a group of non-virulent or low virulent strains isolated from a wide host range. The repertoire of the genes related to T3SS and T3Es varied among the strains of this cluster and those strains related to the most virulent pathovars of the species, corylina, juglandis, and pruni. This variability provides information about the potential evolutionary process associated to the acquisition of pathogenicity and host specificity in X. arboricola. Finally, based in the genomic differences observed between the virulent and the non-virulent strains isolated from Prunus, a sensitive and specific real-time PCR protocol was designed to detect and identify Xap strains. This method avoids miss-identifications due to atypical strains of X. arboricola that can cohabit Prunus. PMID:28450852

Role of Fatty Acid Kinase in Cellular Lipid Homeostasis and SaeRS-Dependent Virulence Factor Expression in Staphylococcus aureus.

PubMed

Ericson, Megan E; Subramanian, Chitra; Frank, Matthew W; Rock, Charles O

2017-08-01

The SaeRS two-component system is a master activator of virulence factor transcription in Staphylococcus aureus , but the cellular factors that control its activity are unknown. Fatty acid (FA) kinase is a two-component enzyme system required for extracellular FA uptake and SaeRS activity. Here, we demonstrate the existence of an intracellular nonesterified FA pool in S. aureus that is elevated in strains lacking FA kinase activity. SaeRS-mediated transcription is restored in FA kinase-negative strains when the intracellular FA pool is reduced either by growth with FA-depleted bovine serum albumin to extract the FA into the medium or by the heterologous expression of Neisseria gonorrhoeae acyl-acyl carrier protein synthetase to activate FA for phospholipid synthesis. These data show that FAs act as negative regulators of SaeRS signaling, and FA kinase activates SaeRS-dependent virulence factor production by lowering inhibitory FA levels. Thus, FA kinase plays a role in cellular lipid homeostasis by activating FA for incorporation into phospholipid, and it indirectly regulates SaeRS signaling by maintaining a low intracellular FA pool. IMPORTANCE The SaeRS two-component system is a master transcriptional activator of virulence factor production in response to the host environment in S. aureus , and strains lacking FA kinase have severely attenuated SaeRS-dependent virulence factor transcription. FA kinase is required for the activation of exogenous FAs, and it plays a role in cellular lipid homeostasis by recycling cellular FAs into the phospholipid biosynthetic pathway. Activation of the sensor kinase, SaeS, is mediated by its membrane anchor domain, and the FAs which accumulate in FA kinase knockout strains are potent inhibitors of SaeS-dependent signaling. This work identifies FAs as physiological effectors for the SaeRS system and reveals a connection between cellular lipid homeostasis and the regulation of virulence factor transcription. FA kinase is widely distributed in Gram-positive bacteria, suggesting similar roles for FA kinase in these organisms. Copyright © 2017 Ericson et al.

Effect of subinhibitory concentrations of chlorogenic acid on reducing the virulence factor production by Staphylococcus aureus.

PubMed

Li, Guanghui; Qiao, Mingyu; Guo, Yan; Wang, Xin; Xu, Yunfeng; Xia, Xiaodong

2014-09-01

Chlorogenic acid (CA) has been reported to inhibit several pathogens, but the influence of subinhibitory concentrations of CA on virulence expression of pathogens has not been fully elucidated. The aim of this study was to explore the effect of CA on the virulence factor production of Staphylococcus aureus. The minimum inhibitory concentration (MIC) of CA against S. aureus was determined using a broth microdilution method. Hemolysin assays, coagulase titer assays, adherence to solid-phase fibrinogen assays, Western blot, and real-time reverse transcriptase-polymerase chain reaction were performed to evaluate the effect of subinhibitory concentrations of CA on the virulence factors of S. aureus. MIC of CA against S. aureus ATCC29213 was found to be 2.56 mg/mL. At subinhibitory concentrations, CA significantly inhibited the hemolysis and dose-dependently decreased coagulase titer. Reduced binding to fibrinogen and decreased production of SEA were observed with treatment of CA at concentrations ranging from 1/16MIC to 1/2MIC. CA markedly inhibited the expression of hla, sea, and agr genes in S. aureus. These data demonstrate that the virulence expression of S. aureus could be reduced by CA and suggest that CA could be potentially developed as a supplemental strategy to control S. aureus infection and to prevent staphylococcal food poisoning.

Ribonucleotide reductase class III, an essential enzyme for the anaerobic growth of Staphylococcus aureus, is a virulence determinant in septic arthritis.

PubMed

Kirdis, Ebru; Jonsson, Ing-Marie; Kubica, Malgorzata; Potempa, Jan; Josefsson, Elisabet; Masalha, Mahmud; Foster, Simon J; Tarkowski, Andrzej

2007-01-01

Staphylococcus aureus is the most common cause of joint infections. It also contributes to several other diseases such as pneumonia, osteomyelitis, endocarditis, and sepsis. Bearing in mind that S. aureus becomes rapidly resistant to new antibiotics, many studies survey the virulence factors, with the aim to find alternative prophylaxis/treatment regimens. One potential virulence factor is the bacterial ability to survive at different oxygen tensions. S. aureus expresses ribonucleotide reductases (RNRs), which help it to grow under both aerobic and anaerobic conditions, by reducing ribonucleotides to deoxyribonucleotides. In this study, we investigated the role of RNR class III, which is required for anaerobic growth, as a virulence determinant in the pathogenesis of staphylococcal arthritis. The wild-type S. aureus strain and its isogenic mutant nrdDG mutant were inoculated intravenously into mice. Mice inoculated with the wild-type strain displayed significantly more severe arthritis, with significantly more synovitis and destruction of the bone and cartilage versus mutant strain inoculated mice. Further, the persistence of bacteria in the kidneys was significantly more pronounced in the group inoculated with the wild-type strain. Together these results indicate that RNR class III is an important virulence factor for the establishment of septic arthritis.

Functional and structural properties of a novel protein and virulence factor (Protein sHIP) in Streptococcus pyogenes.

PubMed

Wisniewska, Magdalena; Happonen, Lotta; Kahn, Fredrik; Varjosalo, Markku; Malmström, Lars; Rosenberger, George; Karlsson, Christofer; Cazzamali, Giuseppe; Pozdnyakova, Irina; Frick, Inga-Maria; Björck, Lars; Streicher, Werner; Malmström, Johan; Wikström, Mats

2014-06-27

Streptococcus pyogenes is a significant bacterial pathogen in the human population. The importance of virulence factors for the survival and colonization of S. pyogenes is well established, and many of these factors are exposed to the extracellular environment, enabling bacterial interactions with the host. In the present study, we quantitatively analyzed and compared S. pyogenes proteins in the growth medium of a strain that is virulent to mice with a non-virulent strain. Particularly, one of these proteins was present at significantly higher levels in stationary growth medium from the virulent strain. We determined the three-dimensional structure of the protein that showed a unique tetrameric organization composed of four helix-loop-helix motifs. Affinity pull-down mass spectrometry analysis in human plasma demonstrated that the protein interacts with histidine-rich glycoprotein (HRG), and the name sHIP (streptococcal histidine-rich glycoprotein-interacting protein) is therefore proposed. HRG has antibacterial activity, and when challenged by HRG, sHIP was found to rescue S. pyogenes bacteria. This and the finding that patients with invasive S. pyogenes infection respond with antibody production against sHIP suggest a role for the protein in S. pyogenes pathogenesis. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Xanthomonas oryzae pv. oryzae RpfE Regulates Virulence and Carbon Source Utilization without Change of the DSF Production

PubMed Central

Cho, Jung-Hee; Yoon, Joo-Mi; Lee, Sang-Won; Noh, Young-Hee; Cha, Jae-Soon

2013-01-01

It has been known that most regulation of pathogenicity factor (rpf) genes in xanthomonads regulates virulence in response to the diffusible signal factor, DSF. Although many rpf genes have been functionally characterized, the function of rpfE is still unknown. We cloned the rpfE gene from a Xanthomonas oryzae pv. oryzae (Xoo) Korean race KACC10859 and generated mutant strains to elucidate the role of RpfE with respect to the rpf system. Through experiments using the rpfE-deficient mutant strain, we found that mutation in rpfE gene in Xoo reduced virulence, swarm motility, and production of virulence factors such as cellulase and extracellular polysaccharide. Disease progress by the rpfE-deficient mutant strain was significantly slowed compared to disease progress by the wild type and the number of the rpfE-deficient mutant strain was lower than that of the wild type in the early phase of infection in the inoculated rice leaf. The rpfE mutant strain was unable to utilize sucrose or xylose as carbon sources efficiently in culture. The mutation in rpfE, however, did not affect DSF synthesis. Our results suggest that the rpfE gene regulates the virulence of Xoo under different nutrient conditions without change of DSF production. PMID:25288965

Deletion of ssnA Attenuates the Pathogenicity of Streptococcus suis and Confers Protection against Serovar 2 Strain Challenge.

PubMed

Li, Miao; Cai, Ru-Jian; Li, Chun-Ling; Song, Shuai; Li, Yan; Jiang, Zhi-Yong; Yang, Dong-Xia

2017-01-01

Streptococcus suis serotype 2 (SS2) is a major porcine and human pathogen which causes arthritis, meningitis, and septicemia. Streptococcus suis nuclease A (SsnA) is a recently discovered deoxyribonuclease (DNase), which has been demonstrated to contribute to escape killing in neutrophil extracellular traps (NETs). To further determine the effects of ssnA on virulence, the ssnA deletion mutant (ΔssnA) and its complemented strain (C-ΔssnA) were constructed. The ability of ΔssnA mutant to interact with human laryngeal epithelial cell (Hep-2) was evaluated and it exhibited dramatically decreased ability to adhere to and invade Hep-2 cells. This mutation was found to exhibit significant attenuation of virulence when evaluated in CD1 mice, suggesting ssnA plays a critical role in the pathogenesis of SS2. Finally, we found that immunization with the ΔssnA mutant triggered both antibody responses and cell-mediated immunity, and conferred 80% protection against virulent SS2 challenge in mice. Taken together, our results suggest that ΔssnA represents an attractive candidate for designing an attenuated live vaccine against SS2.

Shoot the Message, Not the Messenger—Combating Pathogenic Virulence in Plants by Inhibiting Quorum Sensing Mediated Signaling Molecules

PubMed Central

Alagarasan, Ganesh; Aswathy, Kumar S.; Madhaiyan, Munusamy

2017-01-01

Immunity, virulence, biofilm formation, and survival in the host environment are regulated by the versatile nature of density dependent microbial cell signaling, also called quorum sensing (QS). The QS molecules can associate with host plant tissues and, at times, cause a change in its gene expression at the downstream level through inter-kingdom cross talking. Progress in controlling QS through fungicide/bactericide in pathogenic microscopic organisms has lead to a rise of antibiotic resistance pathogens. Here, we review the application of selective quorum quenching (QQ) endophytes to control phytopathogens that are shared by most, if not all, terrestrial plant species as well as aquatic plants. Allowing the plants to posses endophytic colonies through biotization will be an additional and a sustainable encompassing methodology resulting in attenuated virulence rather than killing the pathogens. Furthermore, the introduced endophytes could serve as a potential biofertilizer and bioprotection agent, which in turn increases the PAMP- triggered immunity and hormonal systemic acquired resistance (SAR) in plants through SA-JA-ET signaling systems. This paper discusses major challenges imposed by QS and QQ application in biotechnology. PMID:28446917

Biomarker Candidate Identification in Yersinia Pestis Using Organism-Wide Semiquantitative Proteomics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hixson, Kim K.; Adkins, Joshua N.; Baker, Scott E.

2006-11-03

Yersinia pestis, the causative agent of plague, is listed by the CDC as a level A select pathogen. To better enable detection, intervention and treatment of Y. pestis infections, it is necessary to understand its protein expression under conditions that promote or inhibit virulence. To this end, we have utilized a novel combination of the accurate mass and time tag methodology of mass spectrometry and clustering analysis using OmniViz™ to compare the protein abundance changes of 992 identified proteins under four growth conditions. Temperature and Ca2+ concentration were used to trigger virulence associated protein expression fundamental to the low calciummore » response. High-resolution liquid chromatography and electrospray ionization mass spectrometry were utilized to determine protein identity and abundance on the genome-wide level. The cluster analyses revealed, in a rapid visual platform, the reproducibility of the current method as well as relevant protein abundance changes of expected and novel proteins relating to a specific growth condition and sub-cellular location. Using this method, 89 proteins were identified as having a similar abundance change profile to 29 known virulence associated proteins, providing additional biomarker candidates for future detection and vaccine development strategies.« less

The Sit-and-Wait Hypothesis in Bacterial Pathogens: A Theoretical Study of Durability and Virulence.

PubMed

Wang, Liang; Liu, Zhanzhong; Dai, Shiyun; Yan, Jiawei; Wise, Michael J

2017-01-01

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 host-mortality are significantly more durable in the external environment. The results of bioinformatics analysis correspond well with epidemiological data, that is, non-vector-borne pathogens with sit-and-wait potentials have higher number of virulence and durability genes compared with other bacterial groups. However, the conclusions are constrained by the relatively small bacterial sample size and non-standardized experimental data.

The Sit-and-Wait Hypothesis in Bacterial Pathogens: A Theoretical Study of Durability and Virulence

PubMed Central

Wang, Liang; Liu, Zhanzhong; Dai, Shiyun; Yan, Jiawei; Wise, Michael J.

2017-01-01

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 host-mortality are significantly more durable in the external environment. The results of bioinformatics analysis correspond well with epidemiological data, that is, non-vector-borne pathogens with sit-and-wait potentials have higher number of virulence and durability genes compared with other bacterial groups. However, the conclusions are constrained by the relatively small bacterial sample size and non-standardized experimental data. PMID:29209284

Context-Dependent Requirements for FimH and Other Canonical Virulence Factors in Gut Colonization by Extraintestinal Pathogenic Escherichia coli

PubMed Central

Russell, Colin W.; Fleming, Brittany A.; Jost, Courtney A.; Tran, Alexander; Stenquist, Alan T.; Wambaugh, Morgan A.; Bronner, Mary P.

2018-01-01

ABSTRACT Extraintestinal pathogenic Escherichia coli (ExPEC) acts as a commensal within the mammalian gut but can induce pathology upon dissemination to other host environments such as the urinary tract and bloodstream. ExPEC genomes are likely shaped by evolutionary forces encountered within the gut, where the bacteria spend much of their time, provoking the question of how their extraintestinal virulence traits arose. The principle of coincidental evolution, in which a gene that evolved in one niche happens to be advantageous in another, has been used to argue that ExPEC virulence factors originated in response to selective pressures within the gut ecosystem. As a test of this hypothesis, the fitness of ExPEC mutants lacking canonical virulence factors was assessed within the intact murine gut in the absence of antibiotic treatment. We found that most of the tested factors, including cytotoxic necrotizing factor type 1 (CNF1), Usp, colibactin, flagella, and plasmid pUTI89, were dispensable for gut colonization. The deletion of genes encoding the adhesin PapG or the toxin HlyA had transient effects but did not interfere with longer-term persistence. In contrast, a mutant missing the type 1 pilus-associated adhesin FimH displayed somewhat reduced persistence within the gut. However, this phenotype varied dependent on the presence of specific competing strains and was partially attributable to aberrant flagellin expression in the absence of fimH. These data indicate that FimH and other key ExPEC-associated factors are not strictly required for gut colonization, suggesting that the development of extraintestinal virulence traits is not driven solely by selective pressures within the gut. PMID:29311232

Virulence Factors of Erwinia amylovora: A Review

PubMed Central

Piqué, Núria; Miñana-Galbis, David; Merino, Susana; Tomás, Juan M.

2015-01-01

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. PMID:26057748

Candida Species From Eye Infections: Drug Susceptibility, Virulence Factors, and Molecular Characterization.

PubMed

Ranjith, Konduri; Sontam, Bhavani; Sharma, Savitri; Joseph, Joveeta; Chathoth, Kanchana N; Sama, Kalyana C; Murthy, Somasheila I; Shivaji, Sisinthy

2017-08-01

To determine the type of Candida species in ocular infections and to investigate the relationship of antifungal susceptibility profile to virulence factors. Fifty isolates of yeast-like fungi from patients with keratitis, endophthalmitis, and orbital cellulitis were identified by Vitek-2 compact system and DNA sequencing of ITS1-5.8S-ITS2 regions of the rRNA gene, followed by phylogenetic analysis for phenotypic and genotypic identification, respectively. Minimum inhibitory concentration of six antifungal drugs was determined by E test/microbroth dilution methods. Phenotypic and genotypic methods were used to determine the virulence factors. Phylogenetic analysis showed the clustering of all isolates into eight distinct groups with a major cluster formed Candida parapsilosis (n = 21), which was the most common species by both Vitek 2 and DNA sequencing. Using χ2 test no significant difference was noted between the techniques except that Vitek 2 did not identify C. viswanathii, C. orthopsilosis, and two non-Candida genera. Of 43 tested Candida isolates high susceptibility to amphotericin B (39/43, 90.6%) and natamycin (43/43, 100%) was noted. While none of the isolates produced coagulase, all produced esterase and catalase. The potential to form biofilm was detected in 23/43 (53.4%) isolates. Distribution of virulence factors by heat map analysis showed difference in metabolic activity of biofilm producers from nonbiofilm producers. Identified by Vitek 2 and DNA sequencing methods C. parapsilosis was the most common species associated with eye infections. Irrespective of the virulence factors elaborated, the Candida isolates were susceptible to commonly used antifungal drugs such as amphotericin B and natamycin.

The significance of virulence factors in Helicobacter pylori

PubMed Central

SHIOTA, Seiji; SUZUKI, Rumiko; YAMAOKA, Yoshio

2013-01-01

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 geographic 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 the host and environmental factors. Virulence factors of H. pylori, such as cagA, vacA, dupA, iceA, oipA and babA, have been demonstrated to be predictors of severe clinical outcomes. Interestingly, meta-analysis showed that CagA seropositivity was associated with gastric cancer compared with gastritis even in East Asian countries where almost of the strains possessing cagA. Meta-analysis also confirmed the significance of vacA, dupA and iceA. However, there remains the possibility that additional important pathogenic genes can be existed because H. pylori consists of approximately 1 600 genes. 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. PMID:23452293

PCR-based identification of cacao black pod causal agents and identification of biological factors possibly contributing to Phytophthora megakarya's field dominance in West Africa

USDA-ARS?s Scientific Manuscript database

Among the Phytophthora species that cause black pod of cacao, P. megakarya is the most virulent, posing a serious threat to cacao production in Africa. Correct identification of the species causing the black pod and understanding the virulence factors involved are important for developing sustainabl...

Divergent and convergent modes of interaction between wheat and Puccinia graminis f. sp. tritici isolates revealed by the comparative gene co-expression network and genome analyses

USDA-ARS?s Scientific Manuscript database

Two opposing evolutionary constraints exert pressure on pathogens: one to diversify virulence factors in order to evade host defenses, and the other to retain virulence factors critical for maintaining a compatible interaction. To better understand how the diversified arsenals of fungal genes promot...

Survival of the Fittest: How Bacterial Pathogens Utilize Bile To Enhance Infection

PubMed Central

Sistrunk, Jeticia R.; Nickerson, Kourtney P.; Chanin, Rachael B.; Rasko, David A.

2016-01-01

SUMMARY Bacterial pathogens have coevolved with humans in order to efficiently infect, replicate within, and be transmitted to new hosts to ensure survival and a continual infection cycle. For enteric pathogens, the ability to adapt to numerous host factors under the harsh conditions of the gastrointestinal tract is critical for establishing infection. One such host factor readily encountered by enteric bacteria is bile, an innately antimicrobial detergent-like compound essential for digestion and nutrient absorption. Not only have enteric pathogens evolved to resist the bactericidal conditions of bile, but these bacteria also utilize bile as a signal to enhance virulence regulation for efficient infection. This review provides a comprehensive and up-to-date analysis of bile-related research with enteric pathogens. From common responses to the unique expression of specific virulence factors, each pathogen has overcome significant challenges to establish infection in the gastrointestinal tract. Utilization of bile as a signal to modulate virulence factor expression has led to important insights for our understanding of virulence mechanisms for many pathogens. Further research on enteric pathogens exposed to this in vivo signal will benefit therapeutic and vaccine development and ultimately enhance our success at combating such elite pathogens. PMID:27464994

The pathogenesis, detection, and prevention of Vibrio parahaemolyticus

PubMed Central

Wang, Rongzhi; Zhong, Yanfang; Gu, Xiaosong; Yuan, Jun; Saeed, Abdullah F.; Wang, Shihua

2015-01-01

Vibrio parahaemolyticus, a Gram-negative motile bacterium that inhabits marine and estuarine environments throughout the world, is a major food-borne pathogen that causes life-threatening diseases in humans after the consumption of raw or undercooked seafood. The global occurrence of V. parahaemolyticus accentuates the importance of investigating its virulence factors and their effects on the human host. This review describes the virulence factors of V. parahaemolyticus reported to date, including hemolysin, urease, two type III secretion systems and two type VI secretion systems, which both cause both cytotoxicity in cultured cells and enterotoxicity in animal models. We describe various types of detection methods, based on virulence factors, that are used for quantitative detection of V. parahaemolyticus in seafood. We also discuss some useful preventive measures and therapeutic strategies for the diseases mediated by V. parahaemolyticus, which can reduce, to some extent, the damage to humans and aquatic animals attributable to V. parahaemolyticus. This review extends our understanding of the pathogenic mechanisms of V. parahaemolyticus mediated by virulence factors and the diseases it causes in its human host. It should provide new insights for the diagnosis, treatment, and prevention of V. parahaemolyticus infection. PMID:25798132

The Biotrophic Development of Ustilago maydis Studied by RNA-Seq Analysis[OPEN

PubMed Central

Lanver, Daniel; Müller, André N.; Happel, Petra; Franitza, Marek; Reissmann, Stefanie; Altmüller, Janine

2018-01-01

The maize smut fungus Ustilago maydis is a model organism for elucidating host colonization strategies of biotrophic fungi. Here, we performed an in depth transcriptional profiling of the entire plant-associated development of U. maydis wild-type strains. In our analysis, we focused on fungal metabolism, nutritional strategies, secreted effectors, and regulatory networks. Secreted proteins were enriched in three distinct expression modules corresponding to stages on the plant surface, establishment of biotrophy, and induction of tumors. These modules are likely the key determinants for U. maydis virulence. With respect to nutrient utilization, we observed that expression of several nutrient transporters was tied to these virulence modules rather than being controlled by nutrient availability. We show that oligopeptide transporters likely involved in nitrogen assimilation are important virulence factors. By measuring the intramodular connectivity of transcription factors, we identified the potential drivers for the virulence modules. While known components of the b-mating type cascade emerged as inducers for the plant surface and biotrophy module, we identified a set of yet uncharacterized transcription factors as likely responsible for expression of the tumor module. We demonstrate a crucial role for leaf tumor formation and effector gene expression for one of these transcription factors. PMID:29371439

Extracts of Cordia gilletii de wild (Boraginaceae) quench the quorum sensing of Pseudomonas aeruginosa PAO1

PubMed Central

Okusa, Philippe N.; Rasamiravaka, Tsiry; Vandeputte, Olivier; Stévigny, Caroline; Jaziri, Mondher El; Duez, Pierre

2014-01-01

Aim: The fight against infectious diseases and antimicrobial resistances needs the exploration of new active compounds with new proprieties like disrupting quorum sensing (QS) mechanisms, which is a cell-to-cell communication that regulates bacterial virulence factors. In this work, leaves and root barks extracts of a Congolese medicinal plant, Cordia gilletii, were investigated for their effect on the production of Pseudomonas aeruginosa major virulence factors regulated by QS. Materials and Methods: The effect of C. gilletii extracts on virulence factors of P. aeruginosa PAO1 was studied by the evaluation of the production of pyocyanine, elastase and biofilm; and by the measurement of the expression of QS-related genes. Results: The dichloromethane extract from root barks was found to quench the production of pyocyanin, a QS-dependent virulence factor in P. aeruginosa PAO1. Moreover, this extract specifically inhibits the expression of several QS-regulated genes (i.e. lasB, rhlA, lasI, lasR, rhlI, and rhlR) and reduces biofilm formation by PAO1. Conclusion: This study contributes to explain the efficacy of C. gilletii in the traditional treatment of infectious diseases caused by P. aeruginosa. PMID:26401363

Extracts of Cordia gilletii de wild (Boraginaceae) quench the quorum sensing of Pseudomonas aeruginosa PAO1.

PubMed

Okusa, Philippe N; Rasamiravaka, Tsiry; Vandeputte, Olivier; Stévigny, Caroline; Jaziri, Mondher El; Duez, Pierre

2014-01-01

The fight against infectious diseases and antimicrobial resistances needs the exploration of new active compounds with new proprieties like disrupting quorum sensing (QS) mechanisms, which is a cell-to-cell communication that regulates bacterial virulence factors. In this work, leaves and root barks extracts of a Congolese medicinal plant, Cordia gilletii, were investigated for their effect on the production of Pseudomonas aeruginosa major virulence factors regulated by QS. The effect of C. gilletii extracts on virulence factors of P. aeruginosa PAO1 was studied by the evaluation of the production of pyocyanine, elastase and biofilm; and by the measurement of the expression of QS-related genes. The dichloromethane extract from root barks was found to quench the production of pyocyanin, a QS-dependent virulence factor in P. aeruginosa PAO1. Moreover, this extract specifically inhibits the expression of several QS-regulated genes (i.e. lasB, rhlA, lasI, lasR, rhlI, and rhlR) and reduces biofilm formation by PAO1. This study contributes to explain the efficacy of C. gilletii in the traditional treatment of infectious diseases caused by P. aeruginosa.

Pneumolysin plays a key role at the initial step of establishing pneumococcal nasal colonization.

PubMed

Hotomi, Muneki; Yuasa, Jun; Briles, David E; Yamanaka, Noboru

2016-09-01

Nasopharyngeal colonization by Streptococcus pneumoniae is an important initial step for the subsequent development of pneumococcal infections. Pneumococci have many virulence factors that play a role in colonization. Pneumolysin (PLY), a pivotal pneumococcal virulence factor for invasive disease, causes severe tissue damage and inflammation with disruption of epithelial tight junctions. In this study, we evaluated the role of PLY in nasal colonization of S. pneumoniae using a mouse colonization model. A reduction of numbers of PLY-deficient pneumococci recovered from nasal tissue, as well as nasal wash, was observed at days 1 and 2 post-intranasal challenges, but not later. The findings strongly support an important role for PLY in the initial establishment nasal colonization. PLY-dependent invasion of local nasal mucosa may be required to establish nasal colonization with S. pneumoniae. The data help provide a rationale to explain why an organism that exists as an asymptomatic colonizer has evolved virulence factors that enable it to occasionally invade and kill its hosts. Thus, the same pneumococcal virulence factor, PLY that can contribute to killing the host, may also play a role early in the establishment of nasopharynx carriage.

De Novo Synthesis and Functional Analysis of Polyphosphate-Loaded Poly(Ethylene) Glycol Hydrogel Nanoparticles Targeting Pyocyanin and Pyoverdin Production in Pseudomonas aeruginosa as a Model Intestinal Pathogen

PubMed Central

Yin, Yushu; Papavasiliou, Georgia; Zaborina, Olga Y.; Alverdy, John C.; Teymour, Fouad

2017-01-01

The human gastrointestinal tract is the primary site of colonization of multidrug resistant pathogens and the major source of life-threatening complications in critically ill and immunocompromised patients. Eradication measures using antibiotics carry further risk of antibiotic resistance. Furthermore, antibiotic treatment can adversely shift the intestinal microbiome toward domination by resistant pathogens. Therefore, approaches directed to prevent replacement of health promoting microbiota with resistant pathogens should be developed. The use of non-microbicidal drugs to create microenvironmental conditions that suppress virulence of pathogens is an attractive strategy to minimize the negative consequences of intestinal microbiome disruption. We have previously shown that phosphate is depleted in the intestinal tract following surgical injury, that this depletion is a major “cue” that triggers bacterial virulence, and that the maintenance of phosphate abundance prevents virulence expression. However, the use of inorganic phosphate may not be a suitable agent to deliver to the site of the host-pathogen interaction since it is readily adsorbed in small intestine. Here we propose a novel drug delivery approach that exploits the use of nanoparticles that allow for prolonged release of phosphates. We have synthesized phosphate (Pi) and polyphosphate (PPi) crosslinked poly (ethylene) glycol (PEG) hydrogel nanoparticles (NP-Pi and NP-PPi, respectively) that result in sustained delivery of Pi and PPi. NP-PPi demonstrated more prolonged release of PPi as compared to the release of Pi from NP-Pi. In vitro studies indicate that free PPi as well NP-PPi are effective compounds for suppressing pyoverdin and pyocyanin production, two global virulence systems of virulence of P. aeruginosa. These studies suggest that sustained release of polyphosphate from NP-PPi can be exploited as a target for virulence suppression of lethal pathogenic phenotypes in the gastrointestinal tract. PMID:27761766

A natural variant of the cysteine protease virulence factor of group A Streptococcus with an arginine-glycine-aspartic acid (RGD) motif preferentially binds human integrins alphavbeta3 and alphaIIbbeta3.

PubMed

Stockbauer, K E; Magoun, L; Liu, M; Burns, E H; Gubba, S; Renish, S; Pan, X; Bodary, S C; Baker, E; Coburn, J; Leong, J M; Musser, J M

1999-01-05

The human pathogenic bacterium group A Streptococcus produces an extracellular cysteine protease [streptococcal pyrogenic exotoxin B (SpeB)] that is a critical virulence factor for invasive disease episodes. Sequence analysis of the speB gene from 200 group A Streptococcus isolates collected worldwide identified three main mature SpeB (mSpeB) variants. One of these variants (mSpeB2) contains an Arg-Gly-Asp (RGD) sequence, a tripeptide motif that is commonly recognized by integrin receptors. mSpeB2 is made by all isolates of the unusually virulent serotype M1 and several other geographically widespread clones that frequently cause invasive infections. Only the mSpeB2 variant bound to transfected cells expressing integrin alphavbeta3 (also known as the vitronectin receptor) or alphaIIbbeta3 (platelet glycoprotein IIb-IIIa), and binding was blocked by a mAb that recognizes the streptococcal protease RGD motif region. In addition, mSpeB2 bound purified platelet integrin alphaIIbbeta3. Defined beta3 mutants that are altered for fibrinogen binding were defective for SpeB binding. Synthetic peptides with the mSpeB2 RGD motif, but not the RSD sequence present in other mSpeB variants, blocked binding of mSpeB2 to transfected cells expressing alphavbeta3 and caused detachment of cultured human umbilical vein endothelial cells. The results (i) identify a Gram-positive virulence factor that directly binds integrins, (ii) identify naturally occurring variants of a documented Gram-positive virulence factor with biomedically relevant differences in their interactions with host cells, and (iii) add to the theme that subtle natural variation in microbial virulence factor structure alters the character of host-pathogen interactions.

Phylogenetic group distributions, virulence factors and antimicrobial resistance properties of uropathogenic Escherichia coli strains isolated from patients with urinary tract infections in South Korea.

PubMed

Lee, J H; Subhadra, B; Son, Y-J; Kim, D H; Park, H S; Kim, J M; Koo, S H; Oh, M H; Kim, H-J; Choi, C H

2016-01-01

Urinary tract infections (UTIs) are one of the most common diseases by which humans seek medical help and are caused mainly by uropathogenic Escherichia coli (UPEC). Studying the virulence and antibiotic resistance of UPEC with respect to various phylogenetic groups is of utmost importance in developing new therapeutic agents. Thus, in this study, we analysed the virulence factors, antibiotic resistance and phylogenetic groups among various UPEC isolates from children with UTIs. The phylogenetic analysis revealed that majority of the strains responsible for UTIs belonged to the phylogenetic groups B2 and D. Of the 58 E. coli isolates, 79·31% belonged to group B2, 15·51% to group D, 3·44% to group A and 1·72% to B1. Simultaneously, the number of virulence factors and antibiotic resistance exhibited were also significantly high in groups B2 and D compared to other groups. Among the isolates, 44·8% were multidrug resistant and of that 73% belonged to the phylogenetic group B2, indicating the compatibility of antibiotic resistance and certain strains carrying virulence factor genes. The antibiotic resistance profiling of UPEC strains elucidates that the antimicrobial agents such as chloramphenicol, cefoxitin, cefepime, ceftazidime might still be used in the therapy for treating UTIs. As the antibiotic resistance pattern of uropathogenic Escherichia coli varies depending on different geographical regions, the antibiotic resistance pattern from this study will help the physicians to effectively administer antibiotic therapy for urinary tract infections. In addition, the frequency of virulence factors and antibiotic resistance genes among various phylogenic groups could be effectively used to draw new targets for uropathogenic Escherichia coli antibiotic-independent therapies. The study emphasizes need of public awareness on multidrug resistance and for more prudent use of antimicrobials. © 2015 The Society for Applied Microbiology.

Association among H. pylori virulence markers dupA, cagA and vacA in Brazilian patients.

PubMed

Pereira, Weendelly Nayara; Ferraz, Mariane Avante; Zabaglia, Luanna Munhoz; de Labio, Roger William; Orcini, Wilson Aparecido; Bianchi Ximenez, João Paulo; Neto, Agostinho Caleman; Payão, Spencer Luiz Marques; Rasmussen, Lucas Trevizani

2014-01-23

Only a few Helicobacter pylori-infected individuals develop severe gastric diseases and virulence factors of H. pylori appear to be involved in such clinical outcomes. Duodenal ulcer promoting gene A (dupA) is a novel virulence factor of Helicobacter pylori that is associated with duodenal ulcer development and reduced risk for gastric carcinoma in some populations. The aims of the present study were to determine the presence of dupA gene and evaluate the association among dupA and other virulence factors including cagA and vacA in Brazilian patients. Gastric biopsies were obtained from 205 dyspeptic patients (100 children and 105 adults). DNA was extracted and analyzed for the presence of H. pylori and its virulence factors using the polymerase chain reaction method. Patients with gastritis tested positive for H. pylori more frequently. The dupA gene was detected in 41.5% of them (85/205); cagA gene was found in 98 isolates (47.8%) and vacA genotype s1/m1 in 50.2%, s1/m2 in 8.3%, s2/m2 in 36.6%, s2/m1 in 0.5% and s1/s2/m1/m2 in 4.4%. We also verified a significant association between cagA and dupA genes [p = 0.0003, relative risk (RR) 1.73 and confidence interval [CI] = 1.3-2.3]. The genotypes s1/m1 were also associated with dupA gene (p = 0.0001, RR: 1.72 and CI: 1.3-2.2). The same associations were found when analyzing pediatric and adult groups of patients individually. Ours results suggest that dupA is highly frequent in Brazilian patients and is associated with cagA gene and vacA s1/m1 genotype, and it may be considered an important virulence factor in the development of gastric diseases in adults or children.

Association among H. pylori virulence markers dupA, cagA and vacA in Brazilian patients

PubMed Central

2014-01-01

Background Only a few Helicobacter pylori-infected individuals develop severe gastric diseases and virulence factors of H. pylori appear to be involved in such clinical outcomes. Duodenal ulcer promoting gene A (dupA) is a novel virulence factor of Helicobacter pylori that is associated with duodenal ulcer development and reduced risk for gastric carcinoma in some populations. The aims of the present study were to determine the presence of dupA gene and evaluate the association among dupA and other virulence factors including cagA and vacA in Brazilian patients. Gastric biopsies were obtained from 205 dyspeptic patients (100 children and 105 adults). DNA was extracted and analyzed for the presence of H. pylori and its virulence factors using the polymerase chain reaction method. Results Patients with gastritis tested positive for H. pylori more frequently. The dupA gene was detected in 41.5% of them (85/205); cagA gene was found in 98 isolates (47.8%) and vacA genotype s1/m1 in 50.2%, s1/m2 in 8.3%, s2/m2 in 36.6%, s2/m1 in 0.5% and s1/s2/m1/m2 in 4.4%. We also verified a significant association between cagA and dupA genes [p = 0.0003, relative risk (RR) 1.73 and confidence interval [CI] = 1.3–2.3]. The genotypes s1/m1 were also associated with dupA gene (p = 0.0001, RR: 1.72 and CI: 1.3–2.2). The same associations were found when analyzing pediatric and adult groups of patients individually. Conclusion Ours results suggest that dupA is highly frequent in Brazilian patients and is associated with cagA gene and vacA s1/m1 genotype, and it may be considered an important virulence factor in the development of gastric diseases in adults or children. PMID:24456629

Real-Time Characterization of Virulence Factor Expression in Yersinia pestis Using a Green Fluorescent Protein Reporter System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forde, C; Rocco, J; Fitch, J P

2004-06-09

A real-time reporter system was developed to monitor the thermal induction of virulence factors in Yersinia pestis. The reporter system consists of a plasmid in Y. pestis in which the expression of green fluorescent protein (GFP) is under the control of the promoters for six virulence factors, yopE, sycE, yopK, yopT, yscN, and lcrE/yopN, which are all components of the Type III secretion virulence mechanism of Y. pestis. Induction of the expression of these genes in vivo was determined by the increase in fluorescence intensity of GFP in real time. Basal expression levels observed for the Y. pestis promoters, expressedmore » as percentages of the positive control with GFP under the control of the lac promoter, were: yopE (15%), sycE (15%), yopK (13%), yopT (4%), lcrE (3.3%) and yscN (0.8%). The yopE reporter showed the strongest gene induction following temperature transition from 26 C to 37 C. The induction levels of the other virulence factors, expressed as percentages of yopE induction, were: yopK (57%), sycE (9%), yscN (3%), lcrE (3%), and yopT (2%). The thermal induction of each of these promoter fusions was repressed by calcium, and the ratios of the initial rates of thermal induction without calcium supplementation compared to the rate with calcium supplementation were: yopE (11 fold), yscN (7 fold), yopK (6 fold), lcrE (3 fold), yopT (2 fold), and sycE (2 fold). This work demonstrates a novel approach to quantify gene induction and provides a method to rapidly determine the effects of external stimuli on expression of Y. pestis virulence factors in real time, in living cells.« less

Pathogen effectors target Arabidopsis EDS1 and alter its interactions with immune regulators.

PubMed

Bhattacharjee, Saikat; Halane, Morgan K; Kim, Sang Hee; Gassmann, Walter

2011-12-09

Plant resistance proteins detect the presence of specific pathogen effectors and initiate effector-triggered immunity. Few immune regulators downstream of resistance proteins have been identified, none of which are known virulence targets of effectors. We show that Arabidopsis ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1), a positive regulator of basal resistance and of effector-triggered immunity specifically mediated by Toll-interleukin-1 receptor-nucleotide binding-leucine-rich repeat (TIR-NB-LRR) resistance proteins, forms protein complexes with the TIR-NB-LRR disease resistance proteins RPS4 and RPS6 and with the negative immune regulator SRFR1 at a cytoplasmic membrane. Further, the cognate bacterial effectors AvrRps4 and HopA1 disrupt these EDS1 complexes. Tight association of EDS1 with TIR-NB-LRR-mediated immunity may therefore derive mainly from being guarded by TIR-NB-LRR proteins, and activation of this branch of effector-triggered immunity may directly connect to the basal resistance signaling pathway via EDS1.

The Staphylococcus aureus RNome and Its Commitment to Virulence

PubMed Central

Felden, Brice; Vandenesch, François; Bouloc, Philippe; Romby, Pascale

2011-01-01

Staphylococcus aureus is a major human pathogen causing a wide spectrum of nosocomial and community-associated infections with high morbidity and mortality. S. aureus generates a large number of virulence factors whose timing and expression levels are precisely tuned by regulatory proteins and RNAs. The aptitude of bacteria to use RNAs to rapidly modify gene expression, including virulence factors in response to stress or environmental changes, and to survive in a host is an evolving concept. Here, we focus on the recently inventoried S. aureus regulatory RNAs, with emphasis on those with identified functions, two of which are directly involved in pathogenicity. PMID:21423670

Spondylodiscitis in a healthy 12-year-old girl with Extraintestinal pathogenic Escherichia coli (ExPEC) bacteraemia.

PubMed

Gaschignard, J; Geslain, G; Mallet, C; Lorrot, M; Blot, N; Alison, M; Bonacorsi, S

2017-05-31

Escherichia coli (E. coli) is rarely implicated in bone or joint infections in children. We discuss the case of a healthy 12-year-old girl with an E. coli bacteraemia and a T11-T12 spondylodiscitis revealed by magnetic resonance imaging. The strain harboured serogroup O1:K1 and virulence factors common to highly virulent extra intestinal pathogenic E. coli (ExPEC). Immunological work-up was normal. The identification of E. coli in a spondylodiscitis should lead to the search for immunosuppression of the host and virulence factors of the strain, particularly those of ExPEC.

Phenotypic, antimicrobial susceptibility profile and virulence factors of Klebsiella pneumoniae isolated from buffalo and cow mastitic milk.

PubMed

Osman, Kamelia M; Hassan, Hany M; Orabi, Ahmed; Abdelhafez, Ahmed S T

2014-06-01

Studies on the prevalence and virulence genes of Klebsiella mastitis pathogens in a buffalo population are undocumented. Also, the association of rmpA kfu, uge, magA, Aerobactin, K1 and K2 virulent factors with K. pneumoniae buffalo, and cow mastitis is unreported. The virulence of K. pneumoniae was evaluated through both phenotypic and molecular assays. In vivo virulence was assessed by the Vero cell cytotoxicity, suckling mouse assay and mice lethality test. Antimicrobial susceptibility was tested by disk diffusion method. The 45 K. pneumoniae isolates from buffalo (n = 10/232) and cow (n = 35/293) milk were isolated (45/525; 8.6%) and screened via PCR for seven virulence genes encoding uridine diphosphate galactose 4 epimerase encoding gene responsible for capsule and smooth lipopolysaccharide synthesis (uge), siderophores (kfu and aerobactin), protectines or invasins (rmpA and magA), and the capsule and hypermucoviscosity (K1 and K2). The most common virulence genes were rmpA, kfu, uge, and magA (77.8% each). Aerobactin and K1 genes were found at medium rates of 66.7% each and K2 (55.6%). The Vero cell cytotoxicity and LD (50) in mice were found in 100% of isolates. A multidrug resistance pattern was observed for 40% of the antimicrobials. The distribution of virulence profiles indicate a role of rmpA, kfu, uge, magA, Aerobactin, and K1 and K2 in pathogenicity of K. pneumoniae in udder infections and invasiveness, and constitutes a threat for vulnerable animals, even more if they are in combination with antibiotic resistance.

Determinants of GBP Recruitment to Toxoplasma gondii Vacuoles and the Parasitic Factors That Control It

PubMed Central

Virreira Winter, Sebastian; Niedelman, Wendy; Jensen, Kirk D.; Rosowski, Emily E.; Julien, Lindsay; Spooner, Eric; Caradonna, Kacey; Burleigh, Barbara A.; Saeij, Jeroen P. J.; Ploegh, Hidde L.; Frickel, Eva-Maria

2011-01-01

IFN-γ is a major cytokine that mediates resistance against the intracellular parasite Toxoplasma gondii. The p65 guanylate-binding proteins (GBPs) are strongly induced by IFN-γ. We studied the behavior of murine GBP1 (mGBP1) upon infection with T. gondii in vitro and confirmed that IFN-γ-dependent re-localization of mGBP1 to the parasitophorous vacuole (PV) correlates with the virulence type of the parasite. We identified three parasitic factors, ROP16, ROP18, and GRA15 that determine strain-specific accumulation of mGBP1 on the PV. These highly polymorphic proteins are held responsible for a large part of the strain-specific differences in virulence. Therefore, our data suggest that virulence of T. gondii in animals may rely in part on recognition by GBPs. However, phagosomes or vacuoles containing Trypanosoma cruzi did not recruit mGBP1. Co-immunoprecipitation revealed mGBP2, mGBP4, and mGBP5 as binding partners of mGBP1. Indeed, mGBP2 and mGBP5 co-localize with mGBP1 in T. gondii-infected cells. T. gondii thus elicits a cell-autonomous immune response in mice with GBPs involved. Three parasitic virulence factors and unknown IFN-γ-dependent host factors regulate this complex process. Depending on the virulence of the strains involved, numerous GBPs are brought to the PV as part of a large, multimeric structure to combat T. gondii. PMID:21931713

Virulence Factor Targeting of the Bacterial Pathogen Staphylococcus aureus for Vaccine and Therapeutics

PubMed Central

Kane, Trevor L.; Carothers, Katelyn E.; Lee, Shaun W.

2018-01-01

Background Staphylococcus aureus is a major bacterial pathogen capable of causing a range of infections in humans from gastrointestinal disease, skin and soft tissue infections, to severe outcomes such as sepsis. Staphylococcal infections in humans can be frequent and recurring, with treatments becoming less effective due to the growing persistence of antibiotic resistant S. aureus strains. Due to the prevalence of antibiotic resistance, and the current limitations on antibiotic development, an active and highly promising avenue of research has been to develop strategies to specifically inhibit the activity of virulence factors produced S. aureus as an alternative means to treat disease. Objective In this review we specifically highlight several major virulence factors produced by S. aureus for which recent advances in antivirulence approaches may hold promise as an alternative means to treating diseases caused by this pathogen. Strategies to inhibit virulence factors can range from small molecule inhibitors, to antibodies, to mutant and toxoid forms of the virulence proteins. Conclusion The major prevalence of antibiotic resistant strains of S. aureus combined with the lack of new antibiotic discoveries highlight the need for vigorous research into alternative strategies to combat diseases caused by this highly successful pathogen. Current efforts to develop specific antivirulence strategies, vaccine approaches, and alternative therapies for treating severe disease caused by S. aureus have the potential to stem the tide against the limitations that we face in the post-antibiotic era. PMID:27894236

Aberrant Synthesis of Indole-3-Acetic Acid in Saccharomyces cerevisiae Triggers Morphogenic Transition, a Virulence Trait of Pathogenic Fungi

PubMed Central

Rao, Reeta Prusty; Hunter, Ally; Kashpur, Olga; Normanly, Jennifer

2010-01-01

Many plant-associated microbes synthesize the auxin indole-3-acetic acid (IAA), and several IAA biosynthetic pathways have been identified in microbes and plants. Saccharomyces cerevisiae has previously been shown to respond to IAA by inducing pseudohyphal growth. We observed that IAA also induced hyphal growth in the human pathogen Candida albicans and thus may function as a secondary metabolite signal that regulates virulence traits such as hyphal transition in pathogenic fungi. Aldehyde dehydrogenase (Ald) is required for IAA synthesis from a tryptophan (Trp) precursor in Ustilago maydis. Mutant S. cerevisiae with deletions in two ALD genes are unable to convert radiolabeled Trp to IAA, yet produce IAA in the absence of exogenous Trp and at levels higher than wild type. These data suggest that yeast may have multiple pathways for IAA synthesis, one of which is not dependent on Trp. PMID:20233857

Assessment of Mycobacterium bovis deleted in p27-p55 virulence operon as candidate vaccine against tuberculosis in animal models.

PubMed

Bianco, María V; Clark, Simon; Blanco, Federico C; Garbaccio, Sergio; García, Elizabeth; Cataldi, Angel A; Williams, Ann; Bigi, Fabiana

2014-01-01

A Mycobacterium bovis knockout in p27-p55 operon was tested as an antituberculosis experimental vaccine in animal models. The mutant MbΔp27-p55 was significantly more attenuated in nude mice than its parental strain but more virulent than BCG Pasteur. Challenge experiments in mice and guinea pigs using M. bovis or M. tuberculosis strains showed similar protection conferred by MbΔp27-p55 mutant than BCG in terms of pathology and bacterial loads in spleen but lower protection than BCG in lungs. When tested in cattle, MbΔp27-p55 did not induce IL-2 expression and induced a very low production of IFNγ, suggesting that the lack of P27/P55 reduces the capacity of M. bovis of triggering an adequate Th1 response.

Characterization and vaccine potential of outer membrane vesicles produced by Haemophilus parasuis

DOE PAGES

McCaig, William D.; Loving, Crystal L.; Hughes, Holly R.; ...

2016-03-01

Haemophilus parasuis is a Gram-negative bacterium that colonizes the upper respiratory tract of swine and is capable of causing a systemic infection, resulting in high morbidity and mortality. H. parasuis isolates display a wide range of virulence and virulence factors are largely unknown. Commercial bacterins are often used to vaccinate swine against H. parasuis, though strain variability and lack of cross-reactivity can make this an ineffective means of protection. Outer membrane vesicles (OMV) are spherical structures naturally released from the membrane of bacteria and OMV are often enriched in toxins, signaling molecules and other bacterial components. Examination of OMV structuresmore » has led to identification of virulence factors in a number of bacteria and they have been successfully used as subunit vaccines. We have isolated OMV from both virulent and avirulent strains of H. parasuis, have examined their protein content and assessed their ability to induce an immune response in the host. Lastly, vaccination with purified OMV derived from the virulent H. parasuis Nagasaki strain provided protection against challenge with a lethal dose of the bacteria.« less

Pathogenic Vibrio species isolated from estuarine environments (Ceará, Brazil) - antimicrobial resistance and virulence potential profiles.

PubMed

Menezes, Francisca G R DE; Rodriguez, Marina T T; Carvalho, Fátima C T DE; Rebouças, Rosa H; Costa, Renata A; Sousa, Oscarina V DE; Hofer, Ernesto; Vieira, Regine H S F

2017-01-01

Detection of virulent strains associated with aquatic environment is a current concern for the management and control of human and animal health. Thus, Vibrio diversity was investigated in four estuaries from state of Ceará (Pacoti, Choró, Pirangi and Jaguaribe) followed by antimicrobial susceptibility to different antimicrobials used in aquaculture and detection of main virulence factors to human health. Isolation and identification were performed on TCBS agar (selective medium) and dichotomous key based on biochemical characteristics, respectively. Nineteen strains of genus Vibrio were catalogued. Vibrio parahaemolyticus (Choró River) and V. alginolyticus (Pacoti River) were the most abundant species in the four estuaries. All strains were submitted to disk diffusion technique (15 antimicrobials were tested). Resistance was found to: penicillin (82%), ampicillin (54%), cephalotin (7%), aztreonan (1%), gentamicin, cefotaxime and ceftriaxone (0.5%). Five pathogenic strains were chosen to verification of virulence factors. Four estuaries showed a high abundance of species. High number of tested positive strains for virulence is concerning, since some of those strains are associated to human diseases, while others are known pathogens of aquatic organisms.

Characterization and vaccine potential of outer membrane vesicles produced by Haemophilus parasuis

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCaig, William D.; Loving, Crystal L.; Hughes, Holly R.

Haemophilus parasuis is a Gram-negative bacterium that colonizes the upper respiratory tract of swine and is capable of causing a systemic infection, resulting in high morbidity and mortality. H. parasuis isolates display a wide range of virulence and virulence factors are largely unknown. Commercial bacterins are often used to vaccinate swine against H. parasuis, though strain variability and lack of cross-reactivity can make this an ineffective means of protection. Outer membrane vesicles (OMV) are spherical structures naturally released from the membrane of bacteria and OMV are often enriched in toxins, signaling molecules and other bacterial components. Examination of OMV structuresmore » has led to identification of virulence factors in a number of bacteria and they have been successfully used as subunit vaccines. We have isolated OMV from both virulent and avirulent strains of H. parasuis, have examined their protein content and assessed their ability to induce an immune response in the host. Lastly, vaccination with purified OMV derived from the virulent H. parasuis Nagasaki strain provided protection against challenge with a lethal dose of the bacteria.« less

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

PubMed Central

Kong, Cin; Neoh, Hui-min; Nathan, Sheila

2016-01-01

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. PMID:26999200

Assessing the Effects of Light on Differentiation and Virulence of the Plant Pathogen Botrytis cinerea: Characterization of the White Collar Complex

PubMed Central

Hevia, Montserrat A.; Tudzynski, Paul; Larrondo, Luis F.

2013-01-01

Organisms are exposed to a tough environment, where acute daily challenges, like light, can strongly affect several aspects of an individual's physiology, including pathogenesis. While several fungal models have been widely employed to understand the physiological and molecular events associated with light perception, various other agricultural-relevant fungi still remain, in terms of their responsiveness to light, in the dark. The fungus Botrytis cinerea is an aggressive pathogen able to cause disease on a wide range of plant species. Natural B. cinerea isolates exhibit a high degree of diversity in their predominant mode of reproduction. Thus, the majority of naturally occurring strains are known to reproduce asexually via conidia and sclerotia, and sexually via apothecia. Studies from the 1970′s reported on specific developmental responses to treatments with near-UV, blue, red and far-red light. To unravel the signaling machinery triggering development – and possibly also connected with virulence – we initiated the functional characterization of the transcription factor/photoreceptor BcWCL1 and its partner BcWCL2, that form the White Collar Complex (WCC) in B. cinerea. Using mutants either abolished in or exhibiting enhanced WCC signaling (overexpression of both bcwcl1 and bcwcl2), we demonstrate that the WCC is an integral part of the mentioned machinery by mediating transcriptional responses to white light and the inhibition of conidiation in response to this stimulus. Furthermore, the WCC is required for coping with excessive light, oxidative stress and also to achieve full virulence. Although several transcriptional responses are abolished in the absence of bcwcl1, the expression of some genes is still light induced and a distinct conidiation pattern in response to daily light oscillations is enhanced, revealing a complex underlying photobiology. Though overlaps with well-studied fungal systems exist, the light-associated machinery of B. cinerea appears more complex than those of Neurospora crassa and Aspergillus nidulans. PMID:24391918

Assessing the effects of light on differentiation and virulence of the plant pathogen Botrytis cinerea: characterization of the White Collar Complex.

PubMed

Canessa, Paulo; Schumacher, Julia; Hevia, Montserrat A; Tudzynski, Paul; Larrondo, Luis F

2013-01-01

Organisms are exposed to a tough environment, where acute daily challenges, like light, can strongly affect several aspects of an individual's physiology, including pathogenesis. While several fungal models have been widely employed to understand the physiological and molecular events associated with light perception, various other agricultural-relevant fungi still remain, in terms of their responsiveness to light, in the dark. The fungus Botrytis cinerea is an aggressive pathogen able to cause disease on a wide range of plant species. Natural B. cinerea isolates exhibit a high degree of diversity in their predominant mode of reproduction. Thus, the majority of naturally occurring strains are known to reproduce asexually via conidia and sclerotia, and sexually via apothecia. Studies from the 1970's reported on specific developmental responses to treatments with near-UV, blue, red and far-red light. To unravel the signaling machinery triggering development--and possibly also connected with virulence--we initiated the functional characterization of the transcription factor/photoreceptor BcWCL1 and its partner BcWCL2, that form the White Collar Complex (WCC) in B. cinerea. Using mutants either abolished in or exhibiting enhanced WCC signaling (overexpression of both bcwcl1 and bcwcl2), we demonstrate that the WCC is an integral part of the mentioned machinery by mediating transcriptional responses to white light and the inhibition of conidiation in response to this stimulus. Furthermore, the WCC is required for coping with excessive light, oxidative stress and also to achieve full virulence. Although several transcriptional responses are abolished in the absence of bcwcl1, the expression of some genes is still light induced and a distinct conidiation pattern in response to daily light oscillations is enhanced, revealing a complex underlying photobiology. Though overlaps with well-studied fungal systems exist, the light-associated machinery of B. cinerea appears more complex than those of Neurospora crassa and Aspergillus nidulans.

Rtt109-dependent histone H3 K56 acetylation and gene activity are essential for the biological control potential of Beauveria bassiana.

PubMed

Cai, Qing; Wang, Juan-Juan; Shao, Wei; Ying, Sheng-Hua; Feng, Ming-Guang

2018-04-27

Rtt109 is a histone acetyltransferase that catalyzes histone H3K56 acetylation required for genomic stability, DNA damage repair and virulence-related gene activity in yeast-like human pathogens but remains functionally unknown in fungal insect pathogens. This study seeks to elucidate catalytic activity of Rtt109 orthologue and its possible role in sustaining biological control potential of Beauveria bassiana, a fungal entomopathogen. Deletion of rtt109 in B. bassiana abolished histone H3K56 acetylation and triggered histone H2A-S129 phosphorylation. Consequently, the deletion mutant showed increased sensitivities to the stresses of DNA damage, oxidation, cell wall perturbation, high osmolarity and heat shock during colony growth, severe conidiation defects under normal culture conditions, reduced conidial hydrophobicity, decreased conidial UV-B resistance, and attenuated virulence through normal cuticle infection. These phenotypic changes correlated well with reduced transcript levels of many genes, which encode the families of H2A-S129 dephosphorylation-related protein phosphotases, DNA damage-repairing factors, antioxidant enzymes, heat-shock proteins, key developmental activators, hydrophobins and cuticle-degrading Pr1 proteases respectively. Rtt109 can acetylate H3K56 and dephosphorylate H2A-S129 in direct and indirect manners respectively, and hence plays an essential role in sustaining genomic stability and global gene activity required for conidiation capacity, environmental fitness and pest-control potential in B. bassiana. This article is protected by copyright. All rights reserved.

Production of the catechol type siderophore bacillibactin by the honey bee pathogen Paenibacillus larvae.

PubMed

Hertlein, Gillian; Müller, Sebastian; Garcia-Gonzalez, Eva; Poppinga, Lena; Süssmuth, Roderich D; Genersch, Elke

2014-01-01

The Gram-positive bacterium Paenibacillus larvae is the etiological agent of American Foulbrood. This bacterial infection of honey bee brood is a notifiable epizootic posing a serious threat to global honey bee health because not only individual larvae but also entire colonies succumb to the disease. In the recent past considerable progress has been made in elucidating molecular aspects of host pathogen interactions during pathogenesis of P. larvae infections. Especially the sequencing and annotation of the complete genome of P. larvae was a major step forward and revealed the existence of several giant gene clusters coding for non-ribosomal peptide synthetases which might act as putative virulence factors. We here present the detailed analysis of one of these clusters which we demonstrated to be responsible for the biosynthesis of bacillibactin, a P. larvae siderophore. We first established culture conditions allowing the growth of P. larvae under iron-limited conditions and triggering siderophore production by P. larvae. Using a gene disruption strategy we linked siderophore production to the expression of an uninterrupted bacillibactin gene cluster. In silico analysis predicted the structure of a trimeric trithreonyl lactone (DHB-Gly-Thr)3 similar to the structure of bacillibactin produced by several Bacillus species. Mass spectrometric analysis unambiguously confirmed that the siderophore produced by P. larvae is identical to bacillibactin. Exposure bioassays demonstrated that P. larvae bacillibactin is not required for full virulence of P. larvae in laboratory exposure bioassays. This observation is consistent with results obtained for bacillibactin in other pathogenic bacteria.

Prevalence of genes encoding extracellular virulence factors among meticillin-resistant Staphylococcus aureus isolates from the University Hospital, Olomouc, Czech Republic.

PubMed

Sauer, P; Síla, J; Stosová, T; Vecerová, R; Hejnar, P; Vágnerová, I; Kolár, M; Raclavsky, V; Petrzelová, J; Lovecková, Y; Koukalová, D

2008-04-01

A rather fast and complicated progression of an infection caused by some strains of Staphylococcus aureus could be associated with the expression and co-action of virulence factor complexes in these strains. This study screened the antibiotic susceptibility and prevalence of virulence markers in isolates of meticillin-resistant S. aureus (MRSA) obtained from patients hospitalized at the University Hospital in Olomouc, Czech Republic. A total of 100 isolates was screened for 13 genes encoding extracellular virulence determinants (tst, pvl, eta, etb, sea, seb, sec, sed, see, seg, seh, sei and sej) and for their distribution in sample types. Eighty-nine isolates were positive for at least one of the genes. Genes for etb, pvl, see and seh were not detected in any of the MRSA isolates. No statistically significant differences in the occurrence of the determinants studied among sample types were found.

Heterologous expression of Streptococcus mutans Cnm in Lactococcus lactis promotes intracellular invasion, adhesion to human cardiac tissues and virulence.

PubMed

Freires, Irlan A; Avilés-Reyes, Alejandro; Kitten, Todd; Simpson-Haidaris, P J; Swartz, Michael; Knight, Peter A; Rosalen, Pedro L; Lemos, José A; Abranches, Jacqueline

2017-01-02

In S. mutans, the expression of the surface glycoprotein Cnm mediates binding to extracellular matrix proteins, endothelial cell invasion and virulence in the Galleria mellonella invertebrate model. To further characterize Cnm as a virulence factor, the cnm gene from S. mutans strain OMZ175 was expressed in the non-pathogenic Lactococcus lactis NZ9800 using a nisin-inducible system. Despite the absence of the machinery necessary for Cnm glycosylation, Western blot and immunofluorescence microscopy analyses demonstrated that Cnm was effectively expressed and translocated to the cell wall of L. lactis. Similar to S. mutans, expression of Cnm in L. lactis enabled robust binding to collagen and laminin, invasion of human coronary artery endothelial cells and increased virulence in G. mellonella. Using an ex vivo human heart tissue colonization model, we showed that Cnm-positive strains of either S. mutans or L. lactis outcompete their Cnm-negative counterparts for tissue colonization. Finally, Cnm expression facilitated L. lactis adhesion and colonization in a rabbit model of infective endocarditis. Collectively, our results provide unequivocal evidence that binding to extracellular matrices mediated by Cnm is an important virulence attribute of S. mutans and confirm the usefulness of the L. lactis heterologous system for further characterization of bacterial virulence factors.

The Role of Antibiotics in Modulating Virulence in Staphylococcus aureus.

PubMed

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.

Virulence control in group A Streptococcus by a two-component gene regulatory system: global expression profiling and in vivo infection modeling.

PubMed

Graham, Morag R; Smoot, Laura M; Migliaccio, Cristi A Lux; Virtaneva, Kimmo; Sturdevant, Daniel E; Porcella, Stephen F; Federle, Michael J; Adams, Gerald J; Scott, June R; Musser, James M

2002-10-15

Two-component gene regulatory systems composed of a membrane-bound sensor and cytoplasmic response regulator are important mechanisms used by bacteria to sense and respond to environmental stimuli. Group A Streptococcus, the causative agent of mild infections and life-threatening invasive diseases, produces many virulence factors that promote survival in humans. A two-component regulatory system, designated covRS (cov, control of virulence; csrRS), negatively controls expression of five proven or putative virulence factors (capsule, cysteine protease, streptokinase, streptolysin S, and streptodornase). Inactivation of covRS results in enhanced virulence in mouse models of invasive disease. Using DNA microarrays and quantitative RT-PCR, we found that CovR influences transcription of 15% (n = 271) of all chromosomal genes, including many that encode surface and secreted proteins mediating host-pathogen interactions. CovR also plays a central role in gene regulatory networks by influencing expression of genes encoding transcriptional regulators, including other two-component systems. Differential transcription of genes influenced by covR also was identified in mouse soft-tissue infection. This analysis provides a genome-scale overview of a virulence gene network in an important human pathogen and adds insight into the molecular mechanisms used by group A Streptococcus to interact with the host, promote survival, and cause disease.

Malassezia virulence determinants.

PubMed

Hort, Wiebke; Mayser, Peter

2011-04-01

Malassezia yeasts are associated with a number of dermatologic and systemic diseases in humans and animals. Pityriasis versicolor is amongst these diseases and represents one of the most common human skin diseases. Beyond that, the role of Malassezia yeasts in the pathogenesis of other skin diseases such as psoriasis, seborrheic dermatitis and confluent and reticulate papillomatosis is discussed but remains less clear. Clear pathogenetic mechanisms of the above-mentioned diseases are not known so far. The review presents new findings on virulence factors of Malassezia yeasts, shedding light on the pathogenesis of Malassezia-associated diseases. Several virulence factors in Malassezia yeasts are known, based on their enzymatic lipolytic activity resulting in the production of distinct metabolites and special cell wall features. Recently, a secondary metabolic pathway possibly implicated in the pathogenesis of pityriasis versicolor was described. The article presents virulence factors of Malassezia yeasts ranging from irritant metabolic byproducts to highly bioactive indole derivatives and attempts to clarify their pathogenic implications in the different diseases. Special emphasis is given to the pathogenesis of pityriasis versicolor, as it represents the disease wherein the causative relationship with Malassezia yeasts appears the most obvious.

Pathogenic Leptospira: Advances in understanding the molecular pathogenesis and virulence

PubMed Central

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

Proteases from Entamoeba spp. and Pathogenic Free-Living Amoebae as Virulence Factors

PubMed Central

Serrano-Luna, Jesús; Piña-Vázquez, Carolina; Reyes-López, Magda; Ortiz-Estrada, Guillermo

2013-01-01

The standard reference for pathogenic and nonpathogenic amoebae is the human parasite Entamoeba histolytica; a direct correlation between virulence and protease expression has been demonstrated for this amoeba. Traditionally, proteases are considered virulence factors, including those that produce cytopathic effects in the host or that have been implicated in manipulating the immune response. Here, we expand the scope to other amoebae, including less-pathogenic Entamoeba species and highly pathogenic free-living amoebae. In this paper, proteases that affect mucin, extracellular matrix, immune system components, and diverse tissues and cells are included, based on studies in amoebic cultures and animal models. We also include proteases used by amoebae to degrade iron-containing proteins because iron scavenger capacity is currently considered a virulence factor for pathogens. In addition, proteases that have a role in adhesion and encystation, which are essential for establishing and transmitting infection, are discussed. The study of proteases and their specific inhibitors is relevant to the search for new therapeutic targets and to increase the power of drugs used to treat the diseases caused by these complex microorganisms. PMID:23476670

A nitrogen response pathway regulates virulence in plant pathogenic fungi: role of TOR and the bZIP protein MeaB.

PubMed

López-Berges, Manuel S; Rispail, Nicolas; Prados-Rosales, Rafael C; Di Pietro, Antonio

2010-12-01

Virulence in plant pathogenic fungi is controlled through a variety of cellular pathways in response to the host environment. Nitrogen limitation has been proposed to act as a key signal to trigger the in planta expression of virulence genes. Moreover, a conserved Pathogenicity mitogen activated protein kinase (MAPK) cascade is strictly required for plant infection in a wide range of pathogens. We investigated the relationship between nitrogen signaling and the Pathogenicity MAPK cascade in controlling infectious growth of the vascular wilt fungus Fusarium oxysporum. Several MAPK-activated virulence functions such as invasive growth, vegetative hyphal fusion and host adhesion were strongly repressed in the presence of the preferred nitrogen source ammonium. Repression of these functions by ammonium was abolished by L-Methionine sulfoximine (MSX) or rapamycin, two specific inhibitors of Gln synthetase and the protein kinase TOR (Target Of Rapamycin), respectively, and was dependent on the bZIP protein MeaB. Supplying tomato plants with ammonium rather than nitrate resulted in a significant delay of vascular wilt symptoms caused by the F. oxysporum wild type strain, but not by the ΔmeaB mutant. Ammonium also repressed invasive growth in two other pathogens, the rice blast fungus Magnaporthe oryzae and the wheat head blight pathogen Fusarium graminearum. Our results suggest the presence of a conserved nitrogen-responsive pathway that operates via TOR and MeaB to control infectious growth in plant pathogenic fungi.

Virulence and competitive ability in genetically diverse malaria infections

PubMed Central

de Roode, Jacobus C.; Pansini, Riccardo; Cheesman, Sandra J.; Helinski, Michelle E. H.; Huijben, Silvie; Wargo, Andrew R.; Bell, Andrew S.; Chan, Brian H. K.; Walliker, David; Read, Andrew F.

2005-01-01

Explaining parasite virulence is a great challenge for evolutionary biology. Intuitively, parasites that depend on their hosts for their survival should be benign to their hosts, yet many parasites cause harm. One explanation for this is that within-host competition favors virulence, with more virulent strains having a competitive advantage in genetically diverse infections. This idea, which is well supported in theory, remains untested empirically. Here we provide evidence that within-host competition does indeed select for high parasite virulence. We examine the rodent malaria Plasmodium chabaudi in laboratory mice, a parasite–host system in which virulence can be easily monitored and competing strains quantified by using strain-specific real-time PCR. As predicted, we found a strong relationship between parasite virulence and competitive ability, so that more virulent strains have a competitive advantage in mixed-strain infections. In transmission experiments, we found that the strain composition of the parasite populations in mosquitoes was directly correlated with the composition of the blood-stage parasite population. Thus, the outcome of within-host competition determined relative transmission success. Our results imply that within-host competition is a major factor driving the evolution of virulence and can explain why many parasites harm their hosts. PMID:15894623

Listeria monocytogenes ATCC 35152 and NCTC 7973 contain a nonhemolytic, nonvirulent variant.

PubMed Central

Pine, L; Weaver, R E; Carlone, G M; Pienta, P A; Rocourt, J; Goebel, W; Kathariou, S; Bibb, W F; Malcolm, G B

1987-01-01

Listeria monocytogenes NCTC 7973 and this same strain deposited as ATCC 35152 contain two phenotypes: hemolytic virulent colonies and nonvirulent colonies that show no zones of hemolysis when streaked on heart infusion agar containing 5% rabbit blood. Results of examinations of these virulent and nonvirulent strains by investigators at the Centers for Disease Control, Atlanta, Ga., the Pasteur Institute, Paris, France, and the University of Würzburg, Federal Republic of Germany, support the conclusion that the avirulent strain is a nonhemolytic mutant of the virulent strain and that hemolysin is a virulence factor for L. monocytogenes. Images PMID:3121669

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

PubMed

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.

Comparison of the Virulence-Associated Phenotypes of Five Species of Acinetobacter baumannii Complex.

PubMed

Na, In Young; Chung, Eun Seon; Jung, Chang-Yun; Kim, Dae Hun; Shin, Juyoun; Kang, KyeongJin; Kim, Seong-Tae; Ko, Kwan Soo

2016-01-01

In this study, we compared the virulence-associated factors of Acinetobacter baumannii complex species. Sixty-three isolates of five A. baumannii complex species, including 19 A. baumannii, 15 A. nosocomialis, 13 A. seifertii, 13 A. pittii, and 3 A. calcoaceticus isolates, were included in this study. For all isolates, biofilm formation, A549 cell adherence, resistance to normal human serum, and motility were evaluated. A. baumannii complex isolates showed diversity in biofilm formation, A549 cell adherence, and serum resistance, and no strong positive relationships among these virulence characteristics. However, A. seifertii showed relatively consistent virulence-associated phenotypes. In addition, A. baumannii clone ST110 exhibited consistently high virulence-associated phenotypes. Motility was observed in seven isolates, and all four A. baumannii ST110 isolates showed twitching motility. Although some inconsistencies in virulence-associated phenotypes were seen, high virulence characteristics were observed in A. seifertii, which has been mainly reported in Korea and shows high rates of colistin resistance.

Molecular Characterization of Shiga Toxin-Producing Escherichia coli Strains Isolated in Poland.

PubMed

Januszkiewicz, Aleksandra; Rastawicki, Waldemar

2016-08-26

Shiga toxin-producing Escherichia coli (STEC) strains also called verotoxin-producing E. coli (VTEC) represent one of the most important groups of food-borne pathogens that can cause several human diseases such as hemorrhagic colitis (HC) and hemolytic - uremic syndrome (HUS) worldwide. The ability of STEC strains to cause disease is associated with the presence of wide range of identified and putative virulence factors including those encoding Shiga toxin. In this study, we examined the distribution of various virulence determinants among STEC strains isolated in Poland from different sources. A total of 71 Shiga toxin-producing E. coli strains isolated from human, cattle and food over the years 1996-2010 were characterized by microarray and PCR detection of virulence genes. As stx1a subtype was present in all of the tested Shiga toxin 1 producing E. coli strains, a greater diversity of subtypes was found in the gene stx2, which occurred in five subtypes: stx2a, stx2b, stx2c, stx2d, stx2g. Among STEC O157 strains we observed conserved core set of 14 virulence factors, stable in bacteria genome at long intervals of time. There was one cattle STEC isolate which possessed verotoxin gene as well as sta1 gene encoded heat-stable enterotoxin STIa characteristic for enterotoxigenic E. coli. To the best of our knowledge, this is the first comprehensive analysis of virulence gene profiles identified in STEC strains isolated from human, cattle and food in Poland. The results obtained using microarrays technology confirmed high effectiveness of this method in determining STEC virulotypes which provides data suitable for molecular risk assessment of the potential virulence of this bacteria. virulence factors including those encoding Shiga toxin. In this study, we examined the distribution of various virulence determinants among STEC strains isolated in Poland from different sources. A total of 71 Shiga toxin-producing E. coli strains isolated from human, cattle and food over the years 1996-2010 were characterized by microarray and PCR detection of virulence genes. As stx1a subtype was present in all of the tested Shiga toxin 1 producing E. coli strains, a greater diversity of subtypes was found in the gene stx2, which occurred in five subtypes: stx2a, stx2b, stx2c, stx2d, stx2g. Among STEC O157 strains we observed conserved core set of 14 virulence factors, stable in bacteria genome at long intervals of time. There was one cattle STEC isolate which possessed verotoxin gene as well as sta1 gene encoded heat-stable enterotoxin STIa characteristic for enterotoxigenic E. coli. To the best of our knowledge, this is the first comprehensive analysis of virulence gene profiles identified in STEC strains isolated from human, cattle and food in Poland. The results obtained using microarrays technology confirmed high effectiveness of this method in determining STEC virulotypes which provides data suitable for molecular risk assessment of the potential virulence of this bacteria.

Virulence Factor-activity Relationships: Workshop Summary

EPA Science Inventory

The concept or notion of virulence factor–activity relationships (VFAR) is an approach for identifying an analogous process to the use of qualitative structure–activity relationships (QSAR) for identifying new microbial contaminants. In QSAR, it is hypothesized that, for new chem...

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

PubMed

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.

Effector-Triggered Immunity Determines Host Genotype-Specific Incompatibility in Legume-Rhizobium Symbiosis.

PubMed

Yasuda, Michiko; Miwa, Hiroki; Masuda, Sachiko; Takebayashi, Yumiko; Sakakibara, Hitoshi; Okazaki, Shin

2016-08-01

Symbiosis between legumes and rhizobia leads to the formation of N2-fixing root nodules. In soybean, several host genes, referred to as Rj genes, control nodulation. Soybean cultivars carrying the Rj4 gene restrict nodulation by specific rhizobia such as Bradyrhizobium elkanii We previously reported that the restriction of nodulation was caused by B. elkanii possessing a functional type III secretion system (T3SS), which is known for its delivery of virulence factors by pathogenic bacteria. In the present study, we investigated the molecular basis for the T3SS-dependent nodulation restriction in Rj4 soybean. Inoculation tests revealed that soybean cultivar BARC-2 (Rj4/Rj4) restricted nodulation by B. elkanii USDA61, whereas its nearly isogenic line BARC-3 (rj4/rj4) formed nitrogen-fixing nodules with the same strain. Root-hair curling and infection threads were not observed in the roots of BARC-2 inoculated with USDA61, indicating that Rj4 blocked B. elkanii infection in the early stages. Accumulation of H2O2 and salicylic acid (SA) was observed in the roots of BARC-2 inoculated with USDA61. Transcriptome analyses revealed that inoculation of USDA61, but not its T3SS mutant in BARC-2, induced defense-related genes, including those coding for hypersensitive-induced responsive protein, which act in effector-triggered immunity (ETI) in Arabidopsis. These findings suggest that B. elkanii T3SS triggers the SA-mediated ETI-type response in Rj4 soybean, which consequently blocks symbiotic interactions. This study revealed a common molecular mechanism underlying both plant-pathogen and plant-symbiont interactions, and suggests that establishment of a root nodule symbiosis requires the evasion or suppression of plant immune responses triggered by rhizobial effectors. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Plant immunity against viruses: antiviral immune receptors in focus

PubMed Central

Calil, Iara P.

2017-01-01

Abstract Background Among the environmental limitations that affect plant growth, viruses cause major crop losses worldwide and represent serious threats to food security. Significant advances in the field of plant–virus interactions have led to an expansion of potential strategies for genetically engineered resistance in crops during recent years. Nevertheless, the evolution of viral virulence represents a constant challenge in agriculture that has led to a continuing interest in the molecular mechanisms of plant–virus interactions that affect disease or resistance. Scope and Conclusion This review summarizes the molecular mechanisms of the antiviral immune system in plants and the latest breakthroughs reported in plant defence against viruses. Particular attention is given to the immune receptors and transduction pathways in antiviral innate immunity. Plants counteract viral infection with a sophisticated innate immune system that resembles the non-viral pathogenic system, which is broadly divided into pathogen-associated molecular pattern (PAMP)-triggered immunity and effector-triggered immunity. An additional recently uncovered virus-specific defence mechanism relies on host translation suppression mediated by a transmembrane immune receptor. In all cases, the recognition of the virus by the plant during infection is central for the activation of these innate defences, and, conversely, the detection of host plants enables the virus to activate virulence strategies. Plants also circumvent viral infection through RNA interference mechanisms by utilizing small RNAs, which are often suppressed by co-evolving virus suppressors. Additionally, plants defend themselves against viruses through hormone-mediated defences and activation of the ubiquitin–26S proteasome system (UPS), which alternatively impairs and facilitates viral infection. Therefore, plant defence and virulence strategies co-evolve and co-exist; hence, disease development is largely dependent on the extent and rate at which these opposing signals emerge in host and non-host interactions. A deeper understanding of plant antiviral immunity may facilitate innovative biotechnological, genetic and breeding approaches for crop protection and improvement. PMID:27780814

Xanthomonas euvesicatoria type III effector XopQ interacts with tomato and pepper 14-3-3 isoforms to suppress effector-triggered immunity.

PubMed

Teper, Doron; Salomon, Dor; Sunitha, Sukumaran; Kim, Jung-Gun; Mudgett, Mary Beth; Sessa, Guido

2014-01-01

Effector-triggered immunity (ETI) to host-adapted pathogens is associated with rapid cell death at the infection site. The plant-pathogenic bacterium Xanthomonas euvesicatoria (Xcv) interferes with plant cellular processes by injecting effector proteins into host cells through the type III secretion system. Here, we show that the Xcv effector XopQ suppresses cell death induced by components of the ETI-associated MAP kinase cascade MAPKKKα MEK2/SIPK and by several R/avr gene pairs. Inactivation of xopQ by insertional mutagenesis revealed that this effector inhibits ETI-associated cell death induced by avirulent Xcv in resistant pepper (Capsicum annuum), and enhances bacterial growth in resistant pepper and tomato (Solanum lycopersicum). Using protein-protein interaction studies in yeast (Saccharomyces cerevisiae) and in planta, we identified the tomato 14-3-3 isoform SlTFT4 and homologs from other plant species as XopQ interactors. A mutation in the putative 14-3-3 binding site of XopQ impaired interaction of the effector with CaTFT4 in yeast and its virulence function in planta. Consistent with a role in ETI, TFT4 mRNA abundance increased during the incompatible interaction of tomato and pepper with Xcv. Silencing of NbTFT4 in Nicotiana benthamiana significantly reduced cell death induced by MAPKKKα. In addition, silencing of CaTFT4 in pepper delayed the appearance of ETI-associated cell death and enhanced growth of virulent and avirulent Xcv, demonstrating the requirement of TFT4 for plant immunity to Xcv. Our results suggest that the XopQ virulence function is to suppress ETI and immunity-associated cell death by interacting with TFT4, which is an important component of ETI and a bona fide target of XopQ. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

A novel line immunoassay based on recombinant virulence factors enables highly specific and sensitive serologic diagnosis of Helicobacter pylori infection.

PubMed

Formichella, Luca; Romberg, Laura; Bolz, Christian; Vieth, Michael; Geppert, Michael; Göttner, Gereon; Nölting, Christina; Walter, Dirk; Schepp, Wolfgang; Schneider, Arne; Ulm, Kurt; Wolf, Petra; Busch, Dirk H; Soutschek, Erwin; Gerhard, Markus

2013-11-01

Helicobacter pylori colonizes half of the world's population, and infection can lead to ulcers, gastric cancer, and mucosa-associated lymphoid tissue (MALT) lymphoma. Serology is the only test applicable for large-scale, population-based screening, but current tests are hampered by a lack of sensitivity and/or specificity. Also, no serologic test allows the differentiation of type I and type II strains, which is important for predicting the clinical outcome. H. pylori virulence factors have been associated with disease, but direct assessment of virulence factors requires invasive methods to obtain gastric biopsy specimens. Our work aimed at the development of a highly sensitive and specific, noninvasive serologic test to detect immune responses to important H. pylori virulence factors. This line immunoassay system (recomLine) is based on recombinant proteins. For this assay, six highly immunogenic virulence factors (CagA, VacA, GroEL, gGT, HcpC, and UreA) were expressed in Escherichia coli, purified, and immobilized to nitrocellulose membranes to detect serological immune responses in patient's sera. For the validation of the line assay, a cohort of 500 patients was screened, of which 290 (58.0%) were H. pylori negative and 210 (42.0%) were positive by histology. The assay showed sensitivity and specificity of 97.6% and 96.2%, respectively, compared to histology. In direct comparison to lysate blotting and enzyme-linked immunosorbent assay (ELISA), the recomLine assay had increased discriminatory power. For the assessment of individual risk for gastrointestinal disease, the test must be validated in a larger and defined patient cohort. Taking the data together, the recomLine assay provides a valuable tool for the diagnosis of H. pylori infection.

Export of the Virulence Factors from Shigella Flexneri and Characterization of the mxi loci

DTIC Science & Technology

1992-07-20

steps in Shigella pathogenesis. To identify temperature-regulated virulence genes on the plasmid, lacZ protein fusions were randomly generated in S ...this locus conferred the Mxi- phenotype and was found to affect virulence of S . flexneri at the level of invasion, which correlated with reduced...excretion of IpaC. Protease protection experiments indicated the presence of high intracellular reservoirs of Ipa proteins in wild-type S . flexneri as

Metabolic adaptation via regulated enzyme degradation in the pathogenic yeast Candida albicans.

PubMed

Ting, S Y; Ishola, O A; Ahmed, M A; Tabana, Y M; Dahham, S; Agha, M T; Musa, S F; Muhammed, R; Than, L T L; Sandai, D

2017-03-01

The virulence of Candida albicans is dependent upon fitness attributes as well as virulence factors. These attributes include robust stress responses and metabolic flexibility. The assimilation of carbon sources is important for growth and essential for the establishment of infections by C. albicans. Previous studies showed that the C. albicans ICL1 genes, which encode the glyoxylate cycle enzymes isocitratelyase are required for growth on non-fermentable carbon sources such as lactate and oleic acid and were repressed by 2% glucose. In contrast to S. cerevsiae, the enzyme CaIcl1 was not destabilised by glucose, resulting with its metabolite remaining at high levels. Further glucose addition has caused CaIcl1 to lose its signal and mechanisms that trigger destabilization in response to glucose. Another purpose of this study was to test the stability of the Icl1 enzyme in response to the dietary sugars, fructose, and galactose. In the present study, the ICL1 mRNAs expression was quantified using Quantitative Real Time PCR, whereby the stability of protein was measured and quantified using Western blot and phosphoimager, and the replacing and cloning of ICL1 ORF by gene recombination and ubiquitin binding was conducted via co-immuno-precipitation. Following an analogous experimental approach, the analysis was repeated using S. cerevisiaeas a control. Both galactose and fructose were found to trigger the degradation of the ICL1 transcript in C. albicans. The Icl1 enzyme was stable following galactose addition but was degraded in response to fructose. C. albicans Icl1 (CaIcl1) was also subjected to fructose-accelerated degradation when expressed in S. cerevisiae, indicating that, although it lacks a ubiquitination site, CaIcl1 is sensitive to fructose-accelerated protein degradation. The addition of an ubiquitination site to CaIcl1 resulted in this enzyme becoming sensitive to galactose-accelerated degradation and increases its rate of degradation in the presence of fructose. It can be concluded that ubiquitin-independent pathways of fructose-accelerated enzyme degradation exist in C. albicans. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Cryptococcus neoformans Requires the ESCRT Protein Vps23 for Iron Acquisition from Heme, for Capsule Formation, and for Virulence

PubMed Central

Hu, Guanggan; Caza, Mélissa; Cadieux, Brigitte; Chan, Vivienne; Liu, Victor

2013-01-01

Iron availability is a key regulator of virulence factor elaboration in Cryptococcus neoformans, the causative agent of fungal meningoencephalitis in HIV/AIDS patients. In addition, iron is an essential nutrient for pathogen proliferation in mammalian hosts but little is known about the mechanisms of iron sensing and uptake in fungal pathogens that attack humans. In this study, we mutagenized C. neoformans by Agrobacterium-mediated T-DNA insertion and screened for mutants with reduced growth on heme as the sole iron source. Among 34 mutants, we identified a subset with insertions in the gene for the ESCRT-I (endosomal sorting complex required for transport) protein Vps23 that resulted in a growth defect on heme, presumably due to a defect in uptake via endocytosis or misregulation of iron acquisition from heme. Remarkably, vps23 mutants were also defective in the elaboration of the cell-associated capsular polysaccharide that is a major virulence factor, while overexpression of Vps23 resulted in cells with a slightly enlarged capsule. These phenotypes were mirrored by a virulence defect in the vps23 mutant in a mouse model of cryptococcosis and by hypervirulence of the overexpression strain. Overall, these results reveal an important role for trafficking via ESCRT functions in both heme uptake and capsule formation, and they further reinforce the connection between iron and virulence factor deployment in C. neoformans. PMID:23132495

A Family of Indoles Regulate Virulence and Shiga Toxin Production in Pathogenic E. coli

PubMed Central

Izrayelit, Yevgeniy; Bhatt, Shantanu; Cartwright, Emily; Wang, Wei; Swimm, Alyson I.; Benian, Guy M.; Schroeder, Frank C.; Kalman, Daniel

2013-01-01

Enteropathogenic Escherichia coli (EPEC), enterohemorrhagic E. coli (EHEC) and enteroaggregative E. coli (EAEC) are intestinal pathogens that cause food and water-borne disease in humans. Using biochemical methods and NMR-based comparative metabolomics in conjunction with the nematode Caenorhabditis elegans, we developed a bioassay to identify secreted small molecules produced by these pathogens. We identified indole, indole-3-carboxaldehyde (ICA), and indole-3-acetic acid (IAA), as factors that only in combination are sufficient to kill C. elegans. Importantly, although lethal to C. elegans, these molecules downregulate several bacterial processes important for pathogenesis in mammals. These include motility, biofilm formation and production of Shiga toxins. Some pathogenic E. coli strains are known to contain a Locus of Enterocyte Effacement (LEE), which encodes virulence factors that cause “attaching and effacing” (A/E) lesions in mammals, including formation of actin pedestals. We found that these indole derivatives also downregulate production of LEE virulence factors and inhibit pedestal formation on mammalian cells. Finally, upon oral administration, ICA inhibited virulence and promoted survival in a lethal mouse infection model. In summary, the C. elegans model in conjunction with metabolomics has facilitated identification of a family of indole derivatives that broadly regulate physiology in E. coli, and virulence in pathogenic strains. These molecules may enable development of new therapeutics that interfere with bacterial small-molecule signaling. PMID:23372726

Cryptococcus neoformans requires the ESCRT protein Vps23 for iron acquisition from heme, for capsule formation, and for virulence.

PubMed

Hu, Guanggan; Caza, Mélissa; Cadieux, Brigitte; Chan, Vivienne; Liu, Victor; Kronstad, James

2013-01-01

Iron availability is a key regulator of virulence factor elaboration in Cryptococcus neoformans, the causative agent of fungal meningoencephalitis in HIV/AIDS patients. In addition, iron is an essential nutrient for pathogen proliferation in mammalian hosts but little is known about the mechanisms of iron sensing and uptake in fungal pathogens that attack humans. In this study, we mutagenized C. neoformans by Agrobacterium-mediated T-DNA insertion and screened for mutants with reduced growth on heme as the sole iron source. Among 34 mutants, we identified a subset with insertions in the gene for the ESCRT-I (endosomal sorting complex required for transport) protein Vps23 that resulted in a growth defect on heme, presumably due to a defect in uptake via endocytosis or misregulation of iron acquisition from heme. Remarkably, vps23 mutants were also defective in the elaboration of the cell-associated capsular polysaccharide that is a major virulence factor, while overexpression of Vps23 resulted in cells with a slightly enlarged capsule. These phenotypes were mirrored by a virulence defect in the vps23 mutant in a mouse model of cryptococcosis and by hypervirulence of the overexpression strain. Overall, these results reveal an important role for trafficking via ESCRT functions in both heme uptake and capsule formation, and they further reinforce the connection between iron and virulence factor deployment in C. neoformans.

Virulence and antimicrobial resistance of Enterococcus faecium isolated from water samples.

PubMed

Enayati, M; Sadeghi, J; Nahaei, M R; Aghazadeh, M; Pourshafie, M R; Talebi, M

2015-10-01

The aim of this study was to determine the incidence of Enterococcus species and six virulence factors of Enterococcus faecium which were isolated from surface water and wells. Fifteen different water samples, which were used for drinking as well as agricultural irrigation, were collected from nine private wells and surface water from six rivers located at the east of Tehran. The Ent. faecium isolates were tested for their resistance to 10 antibiotics and their virulence factors were detected using multiplex PCR for esp, acm, gelE, asa1, cylA and hyl genes. The most predominant species in 315 isolates were Ent. faecium (n = 118) followed by Enterococcus galinarom (n = 110), Enterococcus mundeti (n = 18), Enterococcus hirea (n = 37) and Enterococcus casselifelavus (n = 32). The resistance rates were observed in 41·5, 27·1, 12·7, 6·8 and 1·7% isolates for tetracycline, erythromycin, ampicillin, ciprofloxacin and chloramphenicol respectively. None of the Ent. faecium isolates were resistant to vancomycin, teicoplanin, linezolid, gentamicin and quinuspristin-dalfopristin. Virulence determinant was found in 84·7, 33·9, 16·1 and 2·5% of isolates for acm, asa1, esp, cylA respectively. None of the isolates carried hyl and gelE gene. The presence of virulence factors and antibiotic resistance indicated that water might be an important source of dissemination of virulent enterococci. Contamination of drinking or recreational water by human or animal faecal waste is a major public health threat. In this study, we determine the incidence of Enterococcus species and six virulence factors of Enterococcus faecium which were isolated from surface water and wells. Results from this study suggest that the presence of Ent. faecium in natural and well waters was found to be significant in rural areas of Tehran. Resistant to erythromycin among Ent. faecium was relatively high and the incidence of acm and asa1 among our isolates was common overall. © 2015 The Society for Applied Microbiology.

Environmental History Modulates Arabidopsis Pattern-Triggered Immunity in a HISTONE ACETYLTRANSFERASE1-Dependent Manner.

PubMed

Singh, Prashant; Yekondi, Shweta; Chen, Po-Wen; Tsai, Chia-Hong; Yu, Chun-Wei; Wu, Keqiang; Zimmerli, Laurent

2014-06-01

In nature, plants are exposed to a fluctuating environment, and individuals exposed to contrasting environmental factors develop different environmental histories. Whether different environmental histories alter plant responses to a current stress remains elusive. Here, we show that environmental history modulates the plant response to microbial pathogens. Arabidopsis thaliana plants exposed to repetitive heat, cold, or salt stress were more resistant to virulent bacteria than Arabidopsis grown in a more stable environment. By contrast, long-term exposure to heat, cold, or exposure to high concentrations of NaCl did not provide enhanced protection against bacteria. Enhanced resistance occurred with priming of Arabidopsis pattern-triggered immunity (PTI)-responsive genes and the potentiation of PTI-mediated callose deposition. In repetitively stress-challenged Arabidopsis, PTI-responsive genes showed enrichment for epigenetic marks associated with transcriptional activation. Upon bacterial infection, enrichment of RNA polymerase II at primed PTI marker genes was observed in environmentally challenged Arabidopsis. Finally, repetitively stress-challenged histone acetyltransferase1-1 (hac1-1) mutants failed to demonstrate enhanced resistance to bacteria, priming of PTI, and increased open chromatin states. These findings reveal that environmental history shapes the plant response to bacteria through the development of a HAC1-dependent epigenetic mark characteristic of a primed PTI response, demonstrating a mechanistic link between the primed state in plants and epigenetics. © 2014 American Society of Plant Biologists. All rights reserved.

Enterococci in foods--a conundrum for food safety.

PubMed

Franz, Charles M A P; Stiles, Michael E; Schleifer, Karl Heinz; Holzapfel, Wilhelm H

2003-12-01

Enterococci form part of the lactic acid bacteria (LAB) of importance in foods. They can spoil processed meats but they are on the other hand important for ripening and aroma development of certain traditional cheeses and sausages, especially those produced in the Mediterranean area. Enterococci are also used as human probiotics. However, they are important nosocomial pathogens that cause bacteraemia, endocarditis and other infections. Some strains are resistant to many antibiotics, but antibiotic resistance alone cannot explain the virulence of some of these bacteria. Virulence factors such as adhesins, invasins and haemolysin have been described. The role of enterococci in disease has raised questions on their safety for use in foods or as probiotics. Studies on the incidence of virulence traits among enterococcal strains isolated from food showed that some harbour virulence traits and generally, Enterococcus faecalis harbours more of them than Enterococcus faecium. Regulations in Europe stipulate that safety of probiotic or starter strains is the responsibility of the producer; therefore, each strain intended for such use should be carefully evaluated. For numerous questions, immediate answers are not fully available. It is therefore suggested that when considering an Enterococcus strain for use as a starter or probiotic culture, it is imperative that each particular strain should be carefully evaluated for the presence of all known virulence factors. Ideally, such strains should harbour no virulence determinants and should be sensitive to clinically relevant antibiotics. In general, E. faecium appears to pose a lower risk for use in foods, because these strains generally harbour fewer recognised virulence determinants than E. faecalis. Generally, the incidence of such virulence determinants among E. faecium strains is low, as compared to E. faecalis strains, probably as a result of the presence of pheromone-responsive plasmids.

Functional Genomic Characterization of Virulence Factors from Necrotizing Fasciitis-Causing Strains of Aeromonas hydrophila

PubMed Central

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.

2014-01-01

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. PMID:24795370

ANALYSIS OF AEROMONAS BY MASS SPECTROMETRY: SPECIATION AND VIRULENCE FACTORS

EPA Science Inventory

Introduction:

A number of bacteria, including Aeromonas hydrophila, are listed on the Environmental Protection Agency's 1998 Contaminant Candidate List (CCL) as research needs. One research priority designated by the CCL is the identification of virulence activity facto...

Novel Burkholderia mallei Virulence Factors Linked to Specific Host-Pathogen Protein Interactions

DTIC Science & Technology

2013-06-23

Wallqvist‡ Burkholderia mallei is an infectious intracellular pathogen whose virulence and resistance to antibiotics makes it a potential bioterrorism agent ...experimental Burkholderia data to ini- tially select a small number of proteins as putative viru- lence factors. We then used yeast two-hybrid assays...causative agent of glan- ders, a disease primarily affecting horses but transmittable to humans; and Burkholderia pseudomallei, which is responsible for

Study of virulence factor of Candida species in oral lesions and its association with potentially malignant and malignant lesions.

PubMed

Castillo, Graciela Del Valle; Blanc, Silvia López de; Sotomayor, Claudia Elena; Azcurra, Ana Isabel

2018-07-01

The aim of this study was to explore the association between malignant and premalignant lesions and the virulence factor profile of Candida spp. recovered from different oral lesions. Candida spp. isolated from malignant lesions (squamous cell carcinoma, OC, n = 25), atypical lichen planus (AL, n = 11), chronic candidiasis (CC, n = 25), and asymptomatic carriers (WI, n = 15, control strains.) Isolates were identified in chromogenic medium, colony morphology and biochemical tests. The lipolytic and proteinase activity was determined on supplemented agar with olive oil and BSA, respectively. The biofilm formation with XTT reduction assay and cellular surface hydrophobicity (CSH) by water-hydrocarbon method were performed. All isolates recovered from oral lesions produced the four virulence factors studied with significantly higher levels than in WI isolates. Interestingly, lipolytic activity was absent in WI isolates. The proteolytic activity was similar in AL and OC isolates. OC isolates showed significantly higher CSH values than other clinical isolates. Non-albicans species showed higher biofilm formation than C.albicans (P = 0.03.) There were no significant differences in virulence factors among species. A strong positive correlation was found between proteinase and lipase activity (r = 0.90, P < 0.0001), and between hydrophobicity and biofilm (R = 0.81, P < 0.0001.) CONCLUSIONS: Our results indicate that OC Candida isolates exhibited a significant higher attributes of virulence than other lesions fungus isolates, providing evidence about the association between Candida pathogenicity and lesions severity. Copyright © 2018. Published by Elsevier Ltd.

Porphyromonas gingivalis Uses Specific Domain Rearrangements and Allelic Exchange to Generate Diversity in Surface Virulence Factors.

PubMed

Dashper, Stuart G; Mitchell, Helen L; Seers, Christine A; Gladman, Simon L; Seemann, Torsten; Bulach, Dieter M; Chandry, P Scott; Cross, Keith J; Cleal, Steven M; Reynolds, Eric C

2017-01-01

Porphyromonas gingivalis is a keystone pathogen of chronic periodontitis. The virulence of P. gingivalis is reported to be strain related and there are currently a number of strain typing schemes based on variation in capsular polysaccharide, the major and minor fimbriae and adhesin domains of Lys-gingipain (Kgp), amongst other surface proteins. P. gingivalis can exchange chromosomal DNA between strains by natural competence and conjugation. The aim of this study was to determine the genetic variability of P. gingivalis strains sourced from international locations over a 25-year period and to determine if variability in surface virulence factors has a phylogenetic basis. Whole genome sequencing was performed on 13 strains and comparison made to 10 previously sequenced strains. A single nucleotide polymorphism-based phylogenetic analysis demonstrated a shallow tri-lobed phylogeny. There was a high level of reticulation in the phylogenetic network, demonstrating extensive horizontal gene transfer between the strains. Two highly conserved variants of the catalytic domain of the major virulence factor the Kgp proteinase (Kgp cat I and Kgp cat II) were found. There were three variants of the fourth Kgp C-terminal cleaved adhesin domain. Specific variants of the cell surface proteins FimA, FimCDE, MfaI, RagAB, Tpr, and PrtT were also identified. The occurrence of all these variants in the P. gingivalis strains formed a mosaic that was not related to the SNP-based phylogeny. In conclusion P. gingivalis uses domain rearrangements and genetic exchange to generate diversity in specific surface virulence factors.

The dual nature of trehalose in citrus canker disease: a virulence factor for Xanthomonas citri subsp. citri and a trigger for plant defence responses

PubMed Central

Piazza, Ainelén; Zimaro, Tamara; Garavaglia, Betiana S.; Ficarra, Florencia A.; Thomas, Ludivine; Marondedze, Claudius; Feil, Regina; Lunn, John E.; Gehring, Chris; Ottado, Jorgelina; Gottig, Natalia

2015-01-01

Xanthomonas citri subsp. citri (Xcc) is a bacterial pathogen that causes citrus canker in susceptible Citrus spp. The Xcc genome contains genes encoding enzymes from three separate pathways of trehalose biosynthesis. Expression of genes encoding trehalose-6-phosphate synthase (otsA) and trehalose phosphatase (otsB) was highly induced during canker development, suggesting that the two-step pathway of trehalose biosynthesis via trehalose-6-phosphate has a function in pathogenesis. This pathway was eliminated from the bacterium by deletion of the otsA gene. The resulting XccΔotsA mutant produced less trehalose than the wild-type strain, was less resistant to salt and oxidative stresses, and was less able to colonize plant tissues. Gene expression and proteomic analyses of infected leaves showed that infection with XccΔotsA triggered only weak defence responses in the plant compared with infection with Xcc, and had less impact on the host plant’s metabolism than the wild-type strain. These results suggested that trehalose of bacterial origin, synthesized via the otsA–otsB pathway, in Xcc, plays a role in modifying the host plant’s metabolism to its own advantage but is also perceived by the plant as a sign of pathogen attack. Thus, trehalose biosynthesis has both positive and negative consequences for Xcc. On the one hand, it enables this bacterial pathogen to survive in the inhospitable environment of the leaf surface before infection and exploit the host plant’s resources after infection, but on the other hand, it is a tell-tale sign of the pathogen’s presence that triggers the plant to defend itself against infection. PMID:25770587

Rapid screening of pyogenic Staphylococcus aureus for confirmation of genus and species, methicillin resistance and virulence factors by using two novel multiplex PCR.

PubMed

Haque, Abdul; Haque, Asma; Saeed, Muhammad; Azhar, Aysha; Rasool, Samreen; Shan, Sidra; Ehsan, Beenish; Nisar, Zohaib

2017-01-01

Emergence of methicillin resistant Staphylococcus aureus (MRSA) is a major medical problem of current era. These bacteria are resistant to most drugs and rapid diagnosis can provide a clear guideline to clinicians. They possess specific virulence factors and relevant information can be very useful. We designed this study to develop multiplex PCRs to provide rapid information. We studied 60 Staphylococcus aureus isolates and detected methicillin resistance by cefoxitin sensitivity and targeting of mecA gene. After initial studies with uniplex PCRs we optimized two multiplex PCRs with highly reproducible results. The first multiplex PCR was developed to confirm genus, species and methicillin resistance simultaneously, and the second multiplex PCR was for screening of virulence factors. We found 38.33% isolates as methicillin resistant. α -toxin, the major cytotoxic factor, was detected in 40% whereas β-hemolysin was found in 25% cases. Panton Valentine leucocidin was detected in 8.33% and toxic shock syndrome toxin in5% cases. The results of uniplex and multiplex PCRs were highly compatible. These two multiplex PCRs when run simultaneously can provide vital information about methicillin resistance and virulence status of the isolate within a few hours as compared to several days needed by routine procedures.

Virulence Genes of S. aureus from Dairy Cow Mastitis and Contagiousness Risk.

PubMed

Magro, Giada; Biffani, Stefano; Minozzi, Giulietta; Ehricht, Ralf; Monecke, Stefan; Luini, Mario; Piccinini, Renata

2017-06-21

Staphylococcus aureus ( S. aureus ) is a major agent of dairy cow intramammary infections: the different prevalences of mastitis reported might be related to a combination of S. aureus virulence factors beyond host factors. The present study considered 169 isolates from different Italian dairy herds that were classified into four groups based on the prevalence of S. aureus infection at the first testing: low prevalence (LP), medium-low (MLP), medium-high (MHP) and high (HP). We aimed to correlate the presence of virulence genes with the prevalence of intramammary infections in order to develop new strategies for the control of S. aureus mastitis. Microarray data were statistically evaluated using binary logistic regression and correspondence analysis to screen the risk factors and the relationship between prevalence group and gene. The analysis showed: (1) 24 genes at significant risk of being detected in all the herds with infection prevalence >5%, including genes belonging to microbial surface components recognizing adhesive matrix molecules (MSCRAMMs), immune evasion and serine proteases; and (2) a significant correlation coefficient between the genes interacting with the host immune response and HP isolates against LP ones. These results support the hypothesis that virulence factors, in addition to cow management, could be related to strain contagiousness, offering new insights into vaccine development.

Virulence factors and mechanisms of antibiotic resistance of haemophilus influenzae.

PubMed

Kostyanev, Tomislav S; Sechanova, Lena P

2012-01-01

Haemophilus influenzae is a small gram-negative coccobacillus known as one of the major causes of meningitis, otitis media, sinusitis and epiglottitis, especially in childhood, as well as infections of the lower respiratory tract, eye infections and bacteremia. It has several virulence factors that play a crucial role in patient inflammatory response. Its capsule, the adhesion proteins, pili, the outer membrane proteins, the IgA1 protease and, last but not least, the lipooligosaccharide, increase the virulence of H. influenzae by participating actively in the host invasion the host by the microrganism. Some of these factors are used in vaccine preparations. In the post-vaccine era, an increase has been noticed in many European countries of invasive infections caused by non-encapsulated strains of H. influenzae which have a number of virulence factors, some of which are subject of serious research aiming at creating new vaccines. Numerous mechanisms of antibiotic resistance in H. influenzae are known which can compromise the empirical treatment of infections caused by this microorganism. The increasing incidence of resistance to aminopenicillins, induced not only by enzyme mechanisms but also by a change of their target is turning into a significant problem. Resistance to other antibiotics such as macrolides, tetracyclines, chloramphenicol, trimethoprim/sulfamethoxazole, and fluoroquinolones, commonly used to treat Haemophilus infections has also been described.

Staphylococcus aureus Responds to the Central Metabolite Pyruvate To Regulate Virulence.

PubMed

Harper, Lamia; Balasubramanian, Divya; Ohneck, Elizabeth A; Sause, William E; Chapman, Jessica; Mejia-Sosa, Bryan; Lhakhang, Tenzin; Heguy, Adriana; Tsirigos, Aristotelis; Ueberheide, Beatrix; Boyd, Jeffrey M; Lun, Desmond S; Torres, Victor J

2018-01-23

Staphylococcus aureus is a versatile bacterial pathogen that can cause significant disease burden and mortality. Like other pathogens, S. aureus must adapt to its environment to produce virulence factors to survive the immune responses evoked by infection. Despite the importance of environmental signals for S. aureus pathogenicity, only a limited number of these signals have been investigated in detail for their ability to modulate virulence. Here we show that pyruvate, a central metabolite, causes alterations in the overall metabolic flux of S. aureus and enhances its pathogenicity. We demonstrate that pyruvate induces the production of virulence factors such as the pore-forming leucocidins and that this induction results in increased virulence of community-acquired methicillin-resistant S. aureus (CA-MRSA) clone USA300. Specifically, we show that an efficient "pyruvate response" requires the activation of S. aureus master regulators AgrAC and SaeRS as well as the ArlRS two-component system. Altogether, our report further establishes a strong relationship between metabolism and virulence and identifies pyruvate as a novel regulatory signal for the coordination of the S. aureus virulon through intricate regulatory networks. IMPORTANCE Delineation of the influence of host-derived small molecules on the makeup of human pathogens is a growing field in understanding host-pathogen interactions. S. aureus is a prominent pathogen that colonizes up to one-third of the human population and can cause serious infections that result in mortality in ~15% of cases. Here, we show that pyruvate, a key nutrient and central metabolite, causes global changes to the metabolic flux of S. aureus and activates regulatory networks that allow significant increases in the production of leucocidins. These and other virulence factors are critical for S. aureus to infect diverse host niches, initiate infections, and effectively subvert host immune responses. Understanding how environmental signals, particularly ones that are essential to and prominent in the human host, affect virulence will allow us to better understand pathogenicity and consider more-targeted approaches to tackling the current S. aureus epidemic. Copyright © 2018 Harper et al.

[Virulence determinant of Chromobacterium violaceum].

PubMed

Miki, Tsuyoshi

2014-01-01

Chromobacterium violaceum is a Gram-negative bacterium that infects humans and animals with fatal sepsis. The infection with C. violaceum is rare in case of those who are healthy, but once established, C. violaceum causes sever disease accompanied by abscess formation in the lungs, liver and spleen. Furthermore, C. violaceum is resistant to a broad range of antibiotics, which in some cases renders the antimicrobial therapy for this infection difficult. Thus, the infection with C. violaceum displays high mortality rates unless initial proper antimicrobial therapy. In contrast, the infection mechanism had completely remained unknown. To this end, we have tried to identify virulence factors-associated with C. violaceum infection. Two distinct type III secretion systems (TTSSs) were thought to be one of the most important virulence factors, which are encoded by Chromobacterium pathogenicity island 1/1a and 2 (Cpi-1/-1a and -2) respectively. Our results have shown that Cpi-1/-1a-encoded TTSS, but not Cpi-2, is indispensable for the virulence in a mouse infection model. C. violaceum caused fulminant hepatitis in a Cpi-1/-1a-encoded TTSS-dependent manner. We next have identified 16 novel effectors secreted from Cpi-1/-1a-encoded TTS machinery. From these effectors, we found that CopE (Chromobacterium outer protein E) has similarities to a guanine nucleotide exchange factor (GEF) for Rho GTPases. CopE acts as GEF for Rac1 and Cdc42, leading to induction of actin cytoskeletal rearrangement. Interestingly, C. violaceum invades cultured human epithelial cells in a CopE-dependent manner. Finally, an inactivation of CopE by disruption of copE gene or amino acid point mutation leading to loss of GEF activity attenuates significantly the mouse virulence of C. violaceum. These results suggest that Cpi-1/-1a-encoded TTSS is a major virulence determinant for C. violaceum infection, and that CopE contributes to the virulence in part of this pathogen.

Novel Burkholderia mallei Virulence Factors Linked to Specific Host-Pathogen Protein Interactions*

PubMed Central

Memišević, Vesna; Zavaljevski, Nela; Pieper, Rembert; Rajagopala, Seesandra V.; Kwon, Keehwan; Townsend, Katherine; Yu, Chenggang; Yu, Xueping; DeShazer, David; Reifman, Jaques; Wallqvist, Anders

2013-01-01

Burkholderia mallei is an infectious intracellular pathogen whose virulence and resistance to antibiotics makes it a potential bioterrorism agent. Given its genetic origin as a commensal soil organism, it is equipped with an extensive and varied set of adapted mechanisms to cope with and modulate host-cell environments. One essential virulence mechanism constitutes the specialized secretion systems that are designed to penetrate host-cell membranes and insert pathogen proteins directly into the host cell's cytosol. However, the secretion systems' proteins and, in particular, their host targets are largely uncharacterized. Here, we used a combined in silico, in vitro, and in vivo approach to identify B. mallei proteins required for pathogenicity. We used bioinformatics tools, including orthology detection and ab initio predictions of secretion system proteins, as well as published experimental Burkholderia data to initially select a small number of proteins as putative virulence factors. We then used yeast two-hybrid assays against normalized whole human and whole murine proteome libraries to detect and identify interactions among each of these bacterial proteins and host proteins. Analysis of such interactions provided both verification of known virulence factors and identification of three new putative virulence proteins. We successfully created insertion mutants for each of these three proteins using the virulent B. mallei ATCC 23344 strain. We exposed BALB/c mice to mutant strains and the wild-type strain in an aerosol challenge model using lethal B. mallei doses. In each set of experiments, mice exposed to mutant strains survived for the 21-day duration of the experiment, whereas mice exposed to the wild-type strain rapidly died. Given their in vivo role in pathogenicity, and based on the yeast two-hybrid interaction data, these results point to the importance of these pathogen proteins in modulating host ubiquitination pathways, phagosomal escape, and actin-cytoskeleton rearrangement processes. PMID:23800426

Molecular interaction of Siglecs (sialic acid-binding Ig-like lectins) with sialylated ligands on Trypanosoma cruzi.

PubMed

Jacobs, Thomas; Erdmann, Hanna; Fleischer, Bernhard

2010-01-01

The protozoan parasite Trypanosoma cruzi (T. cruzi) is transmitted by blood-sucking insect vectors. After transmission, parasites circulate in the blood as trypomastigotes and invade a variety of cells to multiply intracellularly as amastigotes. The acute phase triggers an immune response that restricts the dissemination and proliferation of parasites. However, parasites are able to persist in different tissues for decades causing the pathology of Chagas' disease. T. cruzi expresses a trans-sialidase (TS). This unique enzyme transfers sialic acid from host glycoconjugates to mucin-like molecules on the parasite and is supposed to be a major virulence factor. TS and sialylated structures were implicated in the persistence of parasites. We discuss here the recent findings on the function of sialylated structures on the surface of T. cruzi with a special emphasis on their property to interact with sialic acid-binding Ig-like lectins, which may allow the parasite to modulate the immune system of the host. Copyright (c) 2009 Elsevier GmbH. All rights reserved.

Stress responses in Streptococcus species and their effects on the host.

PubMed

Nguyen, Cuong Thach; Park, Sang-Sang; Rhee, Dong-Kwon

2015-11-01

Streptococci cause a variety of diseases, such as dental caries, pharyngitis, meningitis, pneumonia, bacteremia, endocarditis, erysipelas, and necrotizing fasciitis. The natural niche of this genus of bacteria ranges from the mouth and nasopharynx to the skin, indicating that the bacteria will inevitably be subjected to environmental changes during invasion into the host, where it is exposed to the host immune system. Thus, the Streptococcus-host interaction determines whether bacteria are cleared by the host's defenses or whether they survive after invasion to cause serious diseases. If this interaction was to be deciphered, it could aid in the development of novel preventive and therapeutic agents. Streptococcus species possess many virulent factors, such as peroxidases and heat-shock proteins (HSPs), which play key roles in protecting the bacteria from hostile host environments. This review will discuss insights into the mechanism(s) by which streptococci adapt to host environments. Additionally, we will address how streptococcal infections trigger host stress responses; however, the mechanism by which bacterial components modulate host stress responses remains largely unknown.

[Evasion of anti-infectious immunity by Brucella - A review].

PubMed

Quan, Wurong; Yang, Yongjie

2016-05-04

Brucellosis, caused by Brucella species, is a worldwide zoonosis. As facultative intracellular pathogens, Brucella possess non-classical virulence factor, but its virulence is very powerful and can elicit chronic infections of both animals and humans. Evasion of host anti-infectious immunity is a prerequisite for chronic infections, this ability appears increasingly crucial for Brucella virulence. As successful pathogens, Brucella can escape or suppress innate immunity and modulate adaptive immunity to establish long lasting infections in host cells. In this review, we address the molecular mechanisms of Brucella to evade anti-infectious immunity. This will shed new insights on Brucella virulence and will, potentially, open new prophylactic avenues.

The RNA-binding protein CsrA plays a central role in positively regulating virulence factors in Erwinia amylovora

PubMed Central

Ancona, Veronica; Lee, Jae Hoon; Zhao, Youfu

2016-01-01

The GacS/GacA two-component system (also called GrrS/GrrA) is a global regulatory system which is highly conserved among gamma-proteobacteria. This system positively regulates non-coding small regulatory RNA csrB, which in turn binds to the RNA-binding protein CsrA. However, how GacS/GacA-Csr system regulates virulence traits in E. amylovora remains unknown. Results from mutant characterization showed that the csrB mutant was hypermotile, produced higher amount of exopolysaccharide amylovoran, and had increased expression of type III secretion (T3SS) genes in vitro. In contrast, the csrA mutant exhibited complete opposite phenotypes, including non-motile, reduced amylovoran production and expression of T3SS genes. Furthermore, the csrA mutant did not induce hypersensitive response on tobacco or cause disease on immature pear fruits, indicating that CsrA is a positive regulator of virulence factors. These findings demonstrated that CsrA plays a critical role in E. amylovora virulence and suggested that negative regulation of virulence by GacS/GacA acts through csrB sRNA, which binds to CsrA and neutralizes its positive effect on T3SS gene expression, flagellar formation and amylovoran production. Future research will be focused on determining the molecular mechanism underlying the positive regulation of virulence traits by CsrA. PMID:27845410

The RNA-binding protein CsrA plays a central role in positively regulating virulence factors in Erwinia amylovora.

PubMed

Ancona, Veronica; Lee, Jae Hoon; Zhao, Youfu

2016-11-15

The GacS/GacA two-component system (also called GrrS/GrrA) is a global regulatory system which is highly conserved among gamma-proteobacteria. This system positively regulates non-coding small regulatory RNA csrB, which in turn binds to the RNA-binding protein CsrA. However, how GacS/GacA-Csr system regulates virulence traits in E. amylovora remains unknown. Results from mutant characterization showed that the csrB mutant was hypermotile, produced higher amount of exopolysaccharide amylovoran, and had increased expression of type III secretion (T3SS) genes in vitro. In contrast, the csrA mutant exhibited complete opposite phenotypes, including non-motile, reduced amylovoran production and expression of T3SS genes. Furthermore, the csrA mutant did not induce hypersensitive response on tobacco or cause disease on immature pear fruits, indicating that CsrA is a positive regulator of virulence factors. These findings demonstrated that CsrA plays a critical role in E. amylovora virulence and suggested that negative regulation of virulence by GacS/GacA acts through csrB sRNA, which binds to CsrA and neutralizes its positive effect on T3SS gene expression, flagellar formation and amylovoran production. Future research will be focused on determining the molecular mechanism underlying the positive regulation of virulence traits by CsrA.

Distribution of virulence determinants among antimicrobial-resistant and antimicrobial-susceptible Escherichia coli implicated in urinary tract infections.

PubMed

Stephenson, Sam; Brown, P D

2016-01-01

Uropathogenic Escherichia coli (UPEC) rely on the correlation of virulence expression with antimicrobial resistance to persist and cause severe urinary tract infections (UTIs). We assessed the virulence pattern and prevalence among UPEC strains susceptible and resistant to multiple antimicrobial classes. A total of 174 non-duplicate UPEC strains from patients with clinically significant UTIs were analysed for susceptibility to aminoglycoside, antifolate, cephalosporin, nitrofuran and quinolone antibiotics for the production of extended-spectrum β-lactamases and for the presence of six virulence determinants encoding adhesins (afimbrial, Type 1 fimbriae, P and S-fimbriae) and toxins (cytotoxic necrotising factor and haemolysin). Relatively high resistance rates to nalidixic acid, ciprofloxacin, cephalothin and trimethoprim-sulfamethoxazole (82%, 78%, 62% and 59%, respectively) were observed. Fourteen distinct patterns were identified for the virulence determinants such as afaBC, cnfI, fimH, hylA, papEF and sfaDE. The toxin gene, cnfI (75.3%), was the second most prevalent marker to the adhesin, fimH (97.1%). The significant association of sfaDE/hylA (P < 0.01) among antimicrobial resistant and susceptible strains was also observed notwithstanding an overall greater occurrence of virulence factors among the latter. This study provides a snapshot of UPEC complexity in Jamaica and highlights the significant clonal heterogeneity among strains. Such outcomes emphasise the need for evidence-based strategies in the effective management and control of UTIs.

Route of infection alters virulence of neonatal septicemia Escherichia coli clinical isolates

PubMed Central

Cole, Bryan K.; Scott, Edgar; Ilikj, Marko; Bard, David; Akins, Darrin R.; Dyer, David W.

2017-01-01

Escherichia coli is the leading cause of Gram-negative neonatal septicemia in the United States. Invasion and passage across the neonatal gut after ingestion of maternal E. coli strains produce bacteremia. In this study, we compared the virulence properties of the neonatal E. coli bacteremia clinical isolate SCB34 with the archetypal neonatal E. coli meningitis strain RS218. Whole-genome sequencing data was used to compare the protein coding sequences among these clinical isolates and 33 other representative E. coli strains. Oral inoculation of newborn animals with either strain produced septicemia, whereas intraperitoneal injection caused septicemia only in pups infected with RS218 but not in those injected with SCB34. In addition to being virulent only through the oral route, SCB34 demonstrated significantly greater invasion and transcytosis of polarized intestinal epithelial cells in vitro as compared to RS218. Protein coding sequences comparisons highlighted the presence of known virulence factors that are shared among several of these isolates, and revealed the existence of proteins exclusively encoded in SCB34, many of which remain uncharacterized. Our study demonstrates that oral acquisition is crucial for the virulence properties of the neonatal bacteremia clinical isolate SCB34. This characteristic, along with its enhanced ability to invade and transcytose intestinal epithelium are likely determined by the specific virulence factors that predominate in this strain. PMID:29236742

The Type IX Secretion System (T9SS): Highlights and Recent Insights into Its Structure and Function

PubMed Central

Lasica, Anna M.; Ksiazek, Miroslaw; Madej, Mariusz; Potempa, Jan

2017-01-01

Protein secretion systems are vital for prokaryotic life, as they enable bacteria to acquire nutrients, communicate with other species, defend against biological and chemical agents, and facilitate disease through the delivery of virulence factors. In this review, we will focus on the recently discovered type IX secretion system (T9SS), a complex translocon found only in some species of the Bacteroidetes phylum. T9SS plays two roles, depending on the lifestyle of the bacteria. It provides either a means of movement (called gliding motility) for peace-loving environmental bacteria or a weapon for pathogens. The best-studied members of these two groups are Flavobacterium johnsoniae, a commensal microorganism often found in water and soil, and Porphyromonas gingivalis, a human oral pathogen that is a major causative agent of periodontitis. In P. gingivalis and some other periodontopathogens, T9SS translocates proteins, especially virulence factors, across the outer membrane (OM). Proteins destined for secretion bear a conserved C-terminal domain (CTD) that directs the cargo to the OM translocon. At least 18 proteins are involved in this still enigmatic process, with some engaged in the post-translational modification of T9SS cargo proteins. Upon translocation across the OM, the CTD is removed by a protease with sortase-like activity and an anionic LPS is attached to the newly formed C-terminus. As a result, a cargo protein could be secreted into the extracellular milieu or covalently attached to the bacterial surface. T9SS is regulated by a two-component system; however, the precise environmental signal that triggers it has not been identified. Exploring unknown systems contributing to bacterial virulence is exciting, as it may eventually lead to new therapeutic strategies. During the past decade, the major components of T9SS were identified, as well as hints suggesting the possible mechanism of action. In addition, the list of characterized cargo proteins is constantly growing. The actual structure of the translocon, situated in the OM of bacteria, remains the least explored area; however, new technical approaches and increasing scientific attention have resulted in a growing body of data. Therefore, we present a compact up-to-date review of this topic. PMID:28603700

Loss of Regulatory Protein RfaH Attenuates Virulence of Uropathogenic Escherichia coli

PubMed Central

Nagy, Gábor; Dobrindt, Ulrich; Schneider, György; Khan, A. Salam; Hacker, Jörg; Emödy, Levente

2002-01-01

RfaH is a regulatory protein in Escherichia coli and Salmonella enterica serovar Typhimurium. Although it enhances expression of different factors that are proposed to play a role in bacterial virulence, a direct effect of RfaH on virulence has not been investigated so far. We report that inactivation of rfaH dramatically decreases the virulence of uropathogenic E. coli strain 536 in an ascending mouse model of urinary tract infection. The mortality rate caused by the wild-type strain in this assay is 100%, whereas that of its isogenic rfaH mutant does not exceed 18%. In the case of coinfection, the wild-type strain 536 shows higher potential to colonize the urinary tract even when it is outnumbered 100-fold by its rfaH mutant in the inoculum. In contrast to the wild-type strain, serum resistance of strain 536rfaH::cat is fully abolished. Furthermore, we give evidence that, besides a major decrease in the amount of hemin receptor ChuA (G. Nagy, U. Dobrindt, M. Kupfer, L. Emody, H. Karch, and J. Hacker, Infect. Immun. 69:1924-1928, 2001), loss of the RfaH protein results in an altered lipopolysaccharide phenotype as well as decreased expression of K15 capsule and alpha-hemolysin, whereas levels of other pathogenicity factors such as siderophores, flagella, Prf, and S fimbriae appear to be unaltered in strain 536rfaH::cat in comparison to the wild-type strain. trans complementation of the mutant strain with the rfaH gene restores wild-type levels of the affected virulence factors and consequently restitutes virulence in the mouse model of ascending urinary tract infection. PMID:12117951

The Posttranslocation Chaperone PrsA2 Contributes to Multiple Facets of Listeria monocytogenes Pathogenesis▿ †

PubMed Central

Alonzo, Francis; Port, Gary C.; Cao, Min; Freitag, Nancy E.

2009-01-01

Listeria monocytogenes is an intracellular bacterial pathogen whose virulence depends on the regulated expression of numerous secreted bacterial factors. As for other gram-positive bacteria, many proteins secreted by L. monocytogenes are translocated across the bacterial membrane in an unfolded state to the compartment existing between the membrane and the cell wall. This compartment presents a challenging environment for protein folding due to its high density of negative charge, high concentrations of cations, and low pH. We recently identified PrsA2 as a gene product required for L. monocytogenes virulence. PrsA2 was identified based on its increased secretion by strains containing a mutationally activated form of prfA, the key regulator of L. monocytogenes virulence gene expression. The prsA2 gene product is one of at least two predicted peptidyl-prolyl cis/trans-isomerases encoded by L. monocytogenes; these proteins function as posttranslocation protein chaperones and/or foldases. In this study, we demonstrate that PrsA2 plays a unique and important role in L. monocytogenes pathogenesis by promoting the activity and stability of at least two critical secreted virulence factors: listeriolysin O (LLO) and a broad-specificity phospholipase. Loss of PrsA2 activity severely attenuated virulence in mice and impaired bacterial cell-to-cell spread in host cells. In contrast, mutants lacking prsA1 resembled wild-type bacteria with respect to intracellular growth and cell-to-cell spread as well as virulence in mice. PrsA2 is thus distinct from PrsA1 in its unique requirement for the stability and full activity of L. monocytogenes-secreted factors that contribute to host infection. PMID:19451247

Analysis of Trigger Factors in Episodic Migraineurs Using a Smartphone Headache Diary Applications

PubMed Central

Park, Jeong-Wook; Chu, Min Kyung; Kim, Jae-Moon; Park, Sang-Gue; Cho, Soo-Jin

2016-01-01

Background Various stimuli can trigger migraines in susceptible individuals. We examined migraine trigger factors by using a smartphone headache diary application. Method Episodic migraineurs who agreed to participate in our study downloaded smartphone headache diary application, which was designed to capture the details regarding headache trigger factors and characteristics for 3 months. The participants were asked to access the smartphone headache diary application daily and to confirm the presence of a headache and input the types of trigger factors. Results Sixty-two participants kept diary entries until the end of the study. The diary data for 4,579 days were analyzed. In this data set, 1,099 headache days (336 migraines, 763 non-migraine headaches) were recorded; of these, 772 headache events had with trigger factors, and 327 events did not have trigger factors. The common trigger factors that were present on headache days included stress, fatigue, sleep deprivation, hormonal changes, and weather changes. The likelihood of a headache trigger was 57.7% for stress, 55.1% for sleep deprivation, 48.5% for fatigue, and 46.5% for any trigger. The headaches with trigger factors were associated with greater pain intensity (p<0.001), headache-related disability (p<0.001), abortive medication use (p = 0.02), and the proportion of migraine (p < 0.001), relative to those without trigger factors. Traveling (odd ratios [OR]: 6.4), hormonal changes (OR: 3.5), noise (OR: 2.8), alcohol (OR: 2.5), overeating (OR: 2.4), and stress (OR:1.8) were significantly associated with migraines compared to non-migraine headaches. The headaches that were associated with hormonal changes or noise were more often migraines, regardless of the preventive medication. The headaches due to stress, overeating, alcohol, and traveling were more often migraines without preventive medication, but it was not evident with preventive medication. Conclusion Smartphone headache diary application is an effective tool to assess migraine trigger factors. The headaches with trigger factors had greater severity or migraine features. The type of triggers and the presence of preventive medication influenced the headache characteristics; hence, an investigation of trigger factors would be helpful in understanding migraine occurrences. PMID:26901341

Analysis of Trigger Factors in Episodic Migraineurs Using a Smartphone Headache Diary Applications.

PubMed

Park, Jeong-Wook; Chu, Min Kyung; Kim, Jae-Moon; Park, Sang-Gue; Cho, Soo-Jin

2016-01-01

Various stimuli can trigger migraines in susceptible individuals. We examined migraine trigger factors by using a smartphone headache diary application. Episodic migraineurs who agreed to participate in our study downloaded smartphone headache diary application, which was designed to capture the details regarding headache trigger factors and characteristics for 3 months. The participants were asked to access the smartphone headache diary application daily and to confirm the presence of a headache and input the types of trigger factors. Sixty-two participants kept diary entries until the end of the study. The diary data for 4,579 days were analyzed. In this data set, 1,099 headache days (336 migraines, 763 non-migraine headaches) were recorded; of these, 772 headache events had with trigger factors, and 327 events did not have trigger factors. The common trigger factors that were present on headache days included stress, fatigue, sleep deprivation, hormonal changes, and weather changes. The likelihood of a headache trigger was 57.7% for stress, 55.1% for sleep deprivation, 48.5% for fatigue, and 46.5% for any trigger. The headaches with trigger factors were associated with greater pain intensity (p<0.001), headache-related disability (p<0.001), abortive medication use (p = 0.02), and the proportion of migraine (p < 0.001), relative to those without trigger factors. Traveling (odd ratios [OR]: 6.4), hormonal changes (OR: 3.5), noise (OR: 2.8), alcohol (OR: 2.5), overeating (OR: 2.4), and stress (OR:1.8) were significantly associated with migraines compared to non-migraine headaches. The headaches that were associated with hormonal changes or noise were more often migraines, regardless of the preventive medication. The headaches due to stress, overeating, alcohol, and traveling were more often migraines without preventive medication, but it was not evident with preventive medication. Smartphone headache diary application is an effective tool to assess migraine trigger factors. The headaches with trigger factors had greater severity or migraine features. The type of triggers and the presence of preventive medication influenced the headache characteristics; hence, an investigation of trigger factors would be helpful in understanding migraine occurrences.

Host cell interactions of outer membrane vesicle-associated virulence factors of enterohemorrhagic Escherichia coli O157: Intracellular delivery, trafficking and mechanisms of cell injury

PubMed Central

Greune, Lilo; Jarosch, Kevin-André; Steil, Daniel; Zhang, Wenlan; He, Xiaohua; Lloubes, Roland; Fruth, Angelika; Kim, Kwang Sik; Schmidt, M. Alexander; Dobrindt, Ulrich; Mellmann, Alexander; Karch, Helge

2017-01-01

Outer membrane vesicles (OMVs) are important tools in bacterial virulence but their role in the pathogenesis of infections caused by enterohemorrhagic Escherichia coli (EHEC) O157, the leading cause of life-threatening hemolytic uremic syndrome, is poorly understood. Using proteomics, electron and confocal laser scanning microscopy, immunoblotting, and bioassays, we investigated OMVs secreted by EHEC O157 clinical isolates for virulence factors cargoes, interactions with pathogenetically relevant human cells, and mechanisms of cell injury. We demonstrate that O157 OMVs carry a cocktail of key virulence factors of EHEC O157 including Shiga toxin 2a (Stx2a), cytolethal distending toxin V (CdtV), EHEC hemolysin, and flagellin. The toxins are internalized by cells via dynamin-dependent endocytosis of OMVs and differentially separate from vesicles during intracellular trafficking. Stx2a and CdtV-B, the DNase-like CdtV subunit, separate from OMVs in early endosomes. Stx2a is trafficked, in association with its receptor globotriaosylceramide within detergent-resistant membranes, to the Golgi complex and the endoplasmic reticulum from where the catalytic Stx2a A1 fragment is translocated to the cytosol. CdtV-B is, after its retrograde transport to the endoplasmic reticulum, translocated to the nucleus to reach DNA. CdtV-A and CdtV-C subunits remain OMV-associated and are sorted with OMVs to lysosomes. EHEC hemolysin separates from OMVs in lysosomes and targets mitochondria. The OMV-delivered CdtV-B causes cellular DNA damage, which activates DNA damage responses leading to G2 cell cycle arrest. The arrested cells ultimately die of apoptosis induced by Stx2a and CdtV via caspase-9 activation. By demonstrating that naturally secreted EHEC O157 OMVs carry and deliver into cells a cocktail of biologically active virulence factors, thereby causing cell death, and by performing first comprehensive analysis of intracellular trafficking of OMVs and OMV-delivered virulence factors, we provide new insights into the pathogenesis of EHEC O157 infections. Our data have implications for considering O157 OMVs as vaccine candidates. PMID:28158302

Typing and virulence factors of food-borne Candida spp. isolates.

PubMed

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.

The plant-specific transcription factors CBP60g and SARD1 are targeted by a Verticillium secretory protein VdSCP41 to modulate immunity

PubMed Central

Qin, Jun; Wang, Kailun; Sun, Lifan; Xing, Haiying; Wang, Sheng; Li, Lin; Chen, She

2018-01-01

The vascular pathogen Verticillium dahliae infects the roots of plants to cause Verticillium wilt. The molecular mechanisms underlying V. dahliae virulence and host resistance remain elusive. Here, we demonstrate that a secretory protein, VdSCP41, functions as an intracellular effector that promotes V. dahliae virulence. The Arabidopsis master immune regulators CBP60g and SARD1 and cotton GhCBP60b are targeted by VdSCP41. VdSCP41 binds the C-terminal portion of CBP60g to inhibit its transcription factor activity. Further analyses reveal a transcription activation domain within CBP60g that is required for VdSCP41 targeting. Mutations in both CBP60g and SARD1 compromise Arabidopsis resistance against V. dahliae and partially impair VdSCP41-mediated virulence. Moreover, virus-induced silencing of GhCBP60b compromises cotton resistance to V. dahliae. This work uncovers a virulence strategy in which the V. dahliae secretory protein VdSCP41 directly targets plant transcription factors to inhibit immunity, and reveals CBP60g, SARD1 and GhCBP60b as crucial components governing V. dahliae resistance. PMID:29757140

Vibrio parahaemolyticus strengthens their virulence through modulation of cellular reactive oxygen species in vitro

PubMed Central

El-Malah, Shimaa S.; Yang, Zhenquan; Hu, Maozhi; Li, Qiuchun; Pan, Zhiming; Jiao, Xinan

2014-01-01

Vibrio parahaemolyticus (Vp) is one of the emergent food-borne pathogens that are commensally associated with various shellfish species throughout the world. It is strictly environmental and many strains are pathogenic to humans. The virulent strains cause distinct diseases, including wound infections, septicemia, and most commonly, acute gastroenteritis, which is acquired through the consumption of raw or undercooked seafood, especially shellfish. Vp has two type three secretion systems (T3SSs), which triggering its cytotoxicity and enterotoxicity via their effectors. To better understand the pathogenesis of Vp, we established a cell infection model in vitro using a non-phagocytic cell line. Caco-2 cells were infected with different strains of Vp (pandemic and non-pandemic strains) and several parameters of cytotoxicity were measured together with adhesion and invasion indices, which reflect the pathogen's virulence. Our results show that Vp adheres to cell monolayers and can invade non-phagocytic cells. It also survives and persists in non-phagocytic cells by modulating reactive oxygen species (ROS), allowing its replication, and resulting in complete cellular destruction. We conclude that the pathogenicity of Vp is based on its capacities for adhesion and invasion. Surprisingly's; enhanced of ROS resistance period could promote the survival of Vp inside the intestinal tract, facilitating tissue infection by repressing the host's oxidative stress response. PMID:25566508

Smooth to Rough Dissociation in Brucella: The Missing Link to Virulence.

PubMed

Mancilla, Marcos

2015-01-01

Dissociation encompasses changes in a series of phenotypes: colony and cell morphology, inmunological and biochemical reactions and virulence. The concept is generally associated to the in vitro transition between smooth (S) and rough (R) colonies, a phenotypic observation in Gram-negative bacteria commonly made since the beginning of microbiology as a science. It is also well known that the loss of the O-polysaccharide, the most external lipopolysaccharide (LPS) moiety, triggers the change in the colony phenotype. Although dissociation is related to one of the most basic features used to distinguish between species, i.e., colony morphology, and, in the case of pathogens, predict their virulence behavior, it has been considered a laboratory artifact and thus did not gain further attention. However, recent insights into genetics and pathogenesis of members of Brucella, causative agents of brucellosis, have brought a new outlook on this experimental fact, suggesting that it plays a role beyond the laboratory observations. In this perspective article, the current knowledge on Brucella LPS genetics and its connection with dissociation in the frame of evolution is discussed. Latest reports support the notion that, by means of a better understanding of genetic pathways linked to R phenotype and the biological impact of this intriguing "old" phenomenon, unexpected applications can be achieved.

Analysis of the Bacterial Diversity in Liver Abscess: Differences between Pyogenic and Amebic Abscesses

PubMed Central

Reyna-Fabián, Miriam E.; Zermeño, Valeria; Ximénez, Cecilia; Flores, Janin; Romero, Miguel F.; Diaz, Daniel; Argueta, Jesús; Moran, Patricia; Valadez, Alicia; Cerritos, René

2016-01-01

Several recent studies have demonstrated that virulence in Entamoeba histolytica is triggered in the presence of both pathogenic and nonpathogenic bacteria species using in vitro and in vivo experimental animal models. In this study, we examined samples aspirated from abscess material obtained from patients who were clinically diagnosed with amebic liver abscess (ALA) or pyogenic liver abscess (PLA). To determine the diversity of bacterial species in the abscesses, we performed partial 16S rRNA gene sequencing. In addition, the E. histolytica and Entamoeba dispar species were genotyped using tRNA-linked short tandem repeats as specific molecular markers. The association between clinical data and bacterial and parasite genotypes were examined through a correspondence analysis. The results showed the presence of numerous bacterial groups. These taxonomic groups constitute common members of the gut microbiota, although all of the detected bacterial species have a close phylogenetic relationship with bacterial pathogens. Furthermore, some patients clinically diagnosed with PLA and ALA were coinfected with E. dispar or E. histolytica, which suggests that the virulence of these parasites increased in the presence of bacteria. However, no specific bacterial groups were associated with this effect. Together, our results suggest a nonspecific mechanism of virulence modulation by bacteria in Entamoeba. PMID:26572872

Smooth to Rough Dissociation in Brucella: The Missing Link to Virulence

PubMed Central

Mancilla, Marcos

2016-01-01

Dissociation encompasses changes in a series of phenotypes: colony and cell morphology, inmunological and biochemical reactions and virulence. The concept is generally associated to the in vitro transition between smooth (S) and rough (R) colonies, a phenotypic observation in Gram-negative bacteria commonly made since the beginning of microbiology as a science. It is also well known that the loss of the O-polysaccharide, the most external lipopolysaccharide (LPS) moiety, triggers the change in the colony phenotype. Although dissociation is related to one of the most basic features used to distinguish between species, i.e., colony morphology, and, in the case of pathogens, predict their virulence behavior, it has been considered a laboratory artifact and thus did not gain further attention. However, recent insights into genetics and pathogenesis of members of Brucella, causative agents of brucellosis, have brought a new outlook on this experimental fact, suggesting that it plays a role beyond the laboratory observations. In this perspective article, the current knowledge on Brucella LPS genetics and its connection with dissociation in the frame of evolution is discussed. Latest reports support the notion that, by means of a better understanding of genetic pathways linked to R phenotype and the biological impact of this intriguing “old” phenomenon, unexpected applications can be achieved. PMID:26779449

A molecular trigger for intercontinental epidemics of group A Streptococcus

PubMed Central

Zhu, Luchang; Olsen, Randall J.; Nasser, Waleed; Beres, Stephen B.; Vuopio, Jaana; Kristinsson, Karl G.; Gottfredsson, Magnus; Porter, Adeline R.; DeLeo, Frank R.; Musser, James M.

2015-01-01

The identification of the molecular events responsible for strain emergence, enhanced virulence, and epidemicity has been a long-pursued goal in infectious diseases research. A recent analysis of 3,615 genomes of serotype M1 group A Streptococcus strains (the so-called “flesh-eating” bacterium) identified a recombination event that coincides with the global M1 pandemic beginning in the early 1980s. Here, we have shown that the allelic variation that results from this recombination event, which replaces the chromosomal region encoding secreted NADase and streptolysin O, is the key driver of increased toxin production and enhanced infection severity of the M1 pandemic strains. Using isoallelic mutant strains, we found that 3 polymorphisms in this toxin gene region increase resistance to killing by human polymorphonuclear leukocytes, increase bacterial proliferation, and increase virulence in animal models of pharyngitis and necrotizing fasciitis. Genome sequencing of an additional 1,125 streptococcal strains and virulence studies revealed that a highly similar recombinational replacement event underlies an ongoing intercontinental epidemic of serotype M89 group A Streptococcus infections. By identifying the molecular changes that enhance upper respiratory tract fitness, increased resistance to innate immunity, and increased tissue destruction, we describe a mechanism that underpins epidemic streptococcal infections, which have affected many millions of people. PMID:26258415

The CebE/MsiK Transporter is a Doorway to the Cello-oligosaccharide-mediated Induction of Streptomyces scabies Pathogenicity

PubMed Central

Jourdan, Samuel; Francis, Isolde Maria; Kim, Min Jung; Salazar, Joren Jeico C.; Planckaert, Sören; Frère, Jean-Marie; Matagne, André; Kerff, Frédéric; Devreese, Bart; Loria, Rosemary; Rigali, Sébastien

2016-01-01

Streptomyces scabies is an economically important plant pathogen well-known for damaging root and tuber crops by causing scab lesions. Thaxtomin A is the main causative agent responsible for the pathogenicity of S. scabies and cello-oligosaccharides are environmental triggers that induce the production of this phytotoxin. How cello-oligosaccharides are sensed or transported in order to induce the virulent behavior of S. scabies? Here we report that the cellobiose and cellotriose binding protein CebE, and MsiK, the ATPase providing energy for carbohydrates transport, are the protagonists of the cello-oligosaccharide mediated induction of thaxtomin production in S. scabies. Our work provides the first example where the transport and not the sensing of major constituents of the plant host is the central mechanism associated with virulence of the pathogen. Our results allow to draw a complete pathway from signal transport to phytotoxin production where each step of the cascade is controlled by CebR, the cellulose utilization regulator. We propose the high affinity of CebE to cellotriose as possible adaptation of S. scabies to colonize expanding plant tissue. Our work further highlights how genes associated with primary metabolism in nonpathogenic Streptomyces species have been recruited as basic elements of virulence in plant pathogenic species. PMID:27250236

Putative Serine Protease Effectors of Clavibacter michiganensis Induce a Hypersensitive Response in the Apoplast of Nicotiana Species.

PubMed

Lu, You; Hatsugai, Noriyuki; Katagiri, Fumiaki; Ishimaru, Carol A; Glazebrook, Jane

2015-11-01

Clavibacter michiganensis subspp. michiganensis and sepedonicus cause diseases on solanaceous crops. The genomes of both subspecies encode members of the pat-1 family of putative serine proteases known to function in virulence on host plants and induction of hypersensitive responses (HR) on nonhosts. One gene of this family in C. michiganensis subsp. sepedonicus, chp-7, is required for triggering HR in Nicotiana tabacum. Here, further investigation revealed that mutation of the putative catalytic serine residue at position 232 to threonine abolished the HR induction activity of Chp-7, suggesting that enzymatic activity is required. Purified Chp-7 triggered an HR in N. tabacum leaves in the absence of the pathogen, indicating Chp-7 itself is the HR elicitor from C. michiganensis subsp. sepedonicus. Ectopic expression of chp-7 constructs in N. tabacum leaves revealed that Chp-7 targeted to the apoplast triggered an HR while cytoplasmic Chp-7 did not, indicating that Chp-7 induces the HR in the apoplast of N. tabacum leaves. Chp-7 also induced HR in N. sylvestris, a progenitor of N. tabacum, but not in other Nicotiana species tested. ChpG, a related protein from C. michiganensis subsp. michiganensis, also triggered HR in N. tabacum and N. sylvestris. Unlike Chp-7, ChpG triggered HR in N. clevelandii and N. glutinosa.

Human Infection with Burkholderia thailandensis, China, 2013.

PubMed

Chang, Kai; Luo, Jie; Xu, Huan; Li, Min; Zhang, Fengling; Li, Jin; Gu, Dayong; Deng, Shaoli; Chen, Ming; Lu, Weiping

2017-08-01

Burkholderia thailandensis infection in humans is uncommon. We describe a case of B. thailandensis infection in a person in China, a location heretofore unknown for B. thailandensis. We identified the specific virulence factors of B. thailandensis, which may indicate a transition to a new virulent form.

Toxoplasma's arms race with the host interferon response: a ménage à trois of ROPs.

PubMed

Zhao, Yanlin; Yap, George S

2014-05-14

The Toxoplasma gondii virulence factors ROP5 and ROP18 both target immunity-related GTPases (IRGs) to evade immunity. In this issue of Cell Host & Microbe, Etheridge et al. (2014) identify a third virulence factor, ROP17, which forms a complex and synergizes with ROP5/ROP18 to fully disable the IRG system of antiparasite defense. Copyright © 2014 Elsevier Inc. All rights reserved.

Photoreactivation of Ultraviolet-Irradiated, Plasmid-Bearing and Plasmid-Free Strains of Bacillus anthracis

DTIC Science & Technology

1985-12-19

positive bacterium Bacillus anthracis, is a virulent and highly contagious disease to which most warm-blooded animals, including man, are susceptible... Virulent strains of B. anthracis produce a capsule composed of poly-0-glutamic acid and an exotoxin. The toxin is composed of three proteins identified...as ederma factor (EF), protective antigen (PA), and lethal factor (LF) (17). Anthrax toxin and capsule production are associated with two separate

The alternative sigma factor sigma B of Staphylococcus aureus modulates virulence in experimental central venous catheter-related infections.

PubMed

Lorenz, Udo; Hüttinger, Christian; Schäfer, Tina; Ziebuhr, Wilma; Thiede, Arnulf; Hacker, Jörg; Engelmann, Susanne; Hecker, Michael; Ohlsen, Knut

2008-03-01

The impact of the alternative sigma factor sigma B (SigB) on pathogenesis of Staphylococcus aureus is not conclusively clarified. In this study, a central venous catheter (CVC) related model of multiorgan infection was used to investigate the role of SigB for the pathogenesis of S. aureus infections and biofilm formation in vivo. Analysis of two SigB-positive wild-type strains and their isogenic mutants revealed uniformly that the wild-type was significantly more virulent than the SigB-deficient mutant. The observed difference in virulence was apparently not linked to the capability of the strains to form biofilms in vivo since wild-type and mutant strains were able to produce biofilm layers inside of the catheter. The data strongly indicate that the alternative sigma factor SigB plays a role in CVC-associated infections caused by S. aureus.

Clonal Clusters and Virulence Factors of Group C and G Streptococcus Causing Severe Infections, Manitoba, Canada, 2012-2014.

PubMed

Lother, Sylvain A; Demczuk, Walter; Martin, Irene; Mulvey, Michael; Dufault, Brenden; Lagacé-Wiens, Philippe; Keynan, Yoav

2017-07-01

The incidence of group C and G Streptococcus (GCGS) bacteremia, which is associated with severe disease and death, is increasing. We characterized clinical features, outcomes, and genetic determinants of GCGS bacteremia for 89 patients in Winnipeg, Manitoba, Canada, who had GCGS bacteremia during 2012-2014. Of the 89 patients, 51% had bacteremia from skin and soft tissue, 70% had severe disease features, and 20% died. Whole-genome sequencing analysis was performed on isolates derived from 89 blood samples and 33 respiratory sample controls: 5 closely related genetic lineages were identified as being more likely to cause invasive disease than non-clade isolates (83% vs. 57%, p = 0.002). Virulence factors cbp, fbp, speG, sicG, gfbA, and bca clustered clonally into these clades. A clonal distribution of virulence factors may account for severe and fatal cases of bacteremia caused by invasive GCGS.

The RNA chaperone Hfq is important for the virulence, motility and stress tolerance in the phytopathogen Xanthomonas campestris.

PubMed

Lai, Jie-Ling; Tang, Dong-Jie; Liang, Yu-Wei; Zhang, Ren; Chen, Qi; Qin, Zhen-Ping; Ming, Zhen-Hua; Tang, Ji-Liang

2018-06-14

The RNA chaperone, Hfq, is known to play extensive roles in bacterial growth and development. More recently, it has been shown to be required for virulence in many human and animal bacterial pathogens. Despite these studies little is known about the role Hfq plays in phytopathogenic bacteria. In this study, we show Hfq is required for full virulence of the crucifer black rot pathogen Xanthomonas campestris pv. campestris (Xcc). We demonstrate that an Xcc hfq deletion strain is highly attenuated for virulence in Chinese radish and shows a severe defect in the production of virulence factors including extracellular enzymes and extracellular polysaccharide. Furthermore, the Xcc strain lacking Hfq had significantly reduced cell motility and stress tolerance. These findings suggest that Hfq is a key regulator of important aspects of virulence and adaptation of Xcc. Taken together, our findings are suggestive of a regulatory network placing Hfq at the center of virulence gene expression control in Xcc. This article is protected by copyright. All rights reserved. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

Interaction of extremophilic archaeal viruses with human and mouse complement system and viral biodistribution in mice

PubMed Central

Wu, Linping; Uldahl, Kristine Buch; Chen, Fangfang; Benasutti, Halli; Logvinski, Deborah; Vu, Vivian; Banda, Nirmal K.; Peng, Xu; Simberg, Dmitri; Moghimi, Seyed Moein

2017-01-01

Archaeal viruses offer exceptional biophysical properties for modification and exploration of their potential in bionanotechnology, bioengineering and nanotherapeutic developments. However, the interaction of archaeal viruses with elements of the innate immune system has not been explored, which is a necessary prerequisite if their potential for biomedical applications to be realized. Here we show complement activation through lectin (via direct binding of MBL/MASPs) and alternative pathways by two extremophilic archaeal viruses (Sulfolobus monocaudavirus 1 and Sulfolobus spindle-shaped virus 2) in human serum. We further show some differences in initiation of complement activation pathways between these viruses. Since, Sulfolobus monocaudavirus 1 was capable of directly triggering the alternative pathway, we also demonstrate that the complement regulator factor H has no affinity for the viral surface, but factor H deposition is purely C3-dependent. This suggests that unlike some virulent pathogens Sulfolobus monocaudavirus 1 does not acquire factor H for protection. Complement activation with Sulfolobus monocaudavirus 1 also proceeds in murine sera through MBL-A/C as well as factor D-dependent manner, but C3 deficiency has no overall effect on viral clearance by organs of the reticuloendothelial system on intravenous injection. However, splenic deposition was significantly higher in C3 knockout animals compared with the corresponding wild type mice. We discuss the potential application of these viruses in biomedicine in relation to their complement activating properties. PMID:28846925

Inhibition of Cronobacter sakazakii Virulence Factors by Citral.

PubMed

Shi, Chao; Sun, Yi; Liu, Zhiyuan; Guo, Du; Sun, Huihui; Sun, Zheng; Chen, Shan; Zhang, Wenting; Wen, Qiwu; Peng, Xiaoli; Xia, Xiaodong

2017-02-24

Cronobacter sakazakii is a foodborne pathogen associated with fatal forms of necrotizing enterocolitis, meningitis and sepsis in neonates and infants. The aim of this study was to determine whether citral, a major component of lemongrass oil, could suppress putative virulence factors of C. sakazakii that contribute to infection. Sub-inhibitory concentrations of citral significantly decreased motility, quorum sensing, biofilm formation and endotoxin production. Citral substantially reduced the adhesion and invasion of C. sakazakii to Caco-2 cells and decreased bacterial survival and replication within the RAW 264.7 macrophage cells. Citral also repressed the expression of eighteen genes involved in the virulence. These findings suggest that citral has potential to be developed as an alternative or supplemental agent to mitigate the infections caused by C. sakazakii.

Roles of Calcineurin and Crz1 in Antifungal Susceptibility and Virulence of Candida glabrata▿

PubMed Central

Miyazaki, Taiga; Yamauchi, Shunsuke; Inamine, Tatsuo; Nagayoshi, Yosuke; Saijo, Tomomi; Izumikawa, Koichi; Seki, Masafumi; Kakeya, Hiroshi; Yamamoto, Yoshihiro; Yanagihara, Katsunori; Miyazaki, Yoshitsugu; Kohno, Shigeru

2010-01-01

A Candida glabrata calcineurin mutant exhibited increased susceptibility to both azole antifungal and cell wall-damaging agents and was also attenuated in virulence. Although a mutant lacking the downstream transcription factor Crz1 displayed a cell wall-associated phenotype intermediate to that of the calcineurin mutant and was modestly attenuated in virulence, it did not show increased azole susceptibility. These results suggest that calcineurin regulates both Crz1-dependent and -independent pathways depending on the type of stress. PMID:20100876

The Virulence Plasmid of Yersinia, an Antihost Genome

PubMed Central

Cornelis, Guy R.; Boland, Anne; Boyd, Aoife P.; Geuijen, Cecile; Iriarte, Maite; Neyt, Cécile; Sory, Marie-Paule; Stainier, Isabelle

1998-01-01

The 70-kb virulence plasmid enables Yersinia spp. (Yersinia pestis, Y. pseudotuberculosis, and Y. enterocolitica) to survive and multiply in the lymphoid tissues of their host. It encodes the Yop virulon, an integrated system allowing extracellular bacteria to disarm the cells involved in the immune response, to disrupt their communications, or even to induce their apoptosis by the injection of bacterial effector proteins. This system consists of the Yop proteins and their dedicated type III secretion apparatus, called Ysc. The Ysc apparatus is composed of some 25 proteins including a secretin. Most of the Yops fall into two groups. Some of them are the intracellular effectors (YopE, YopH, YpkA/YopO, YopP/YopJ, YopM, and YopT), while the others (YopB, YopD, and LcrV) form the translocation apparatus that is deployed at the bacterial surface to deliver the effectors into the eukaryotic cells, across their plasma membrane. Yop secretion is triggered by contact with eukaryotic cells and controlled by proteins of the virulon including YopN, TyeA, and LcrG, which are thought to form a plug complex closing the bacterial secretion channel. The proper operation of the system also requires small individual chaperones, called the Syc proteins, in the bacterial cytosol. Transcription of the genes is controlled both by temperature and by the activity of the secretion apparatus. The virulence plasmid of Y. enterocolitica and Y. pseudotuberculosis also encodes the adhesin YadA. The virulence plasmid contains some evolutionary remnants including, in Y. enterocolitica, an operon encoding resistance to arsenic compounds. PMID:9841674

Yersinia pestis YopJ suppresses tumor necrosis factor alpha induction and contributes to apoptosis of immune cells in the lymph node but is not required for virulence in a rat model of bubonic plague.

PubMed

Lemaître, Nadine; Sebbane, Florent; Long, Daniel; Hinnebusch, B Joseph

2006-09-01

The virulence of the pathogenic Yersinia species depends on a plasmid-encoded type III secretion system that transfers six Yop effector proteins into host cells. One of these proteins, YopJ, has been shown to disrupt host cell signaling pathways involved in proinflammatory cytokine production and to induce macrophage apoptosis in vitro. YopJ-dependent apoptosis in mesenteric lymph nodes has also been demonstrated in a mouse model of Yersinia pseudotuberculosis infection. These results suggest that YopJ attenuates the host innate and adaptive immune response during infection, but the role of YopJ during bubonic plague has not been completely established. We evaluated the role of Yersinia pestis YopJ in a rat model of bubonic plague following intradermal infection with a fully virulent Y. pestis strain and an isogenic yopJ mutant. Deletion of yopJ resulted in a twofold decrease in the number of apoptotic immune cells in the bubo and a threefold increase in serum tumor necrosis factor alpha levels but did not result in decreased virulence, systemic spread, or colonization levels in the spleen and blood. Our results indicate that YopJ is not essential for bubonic plague pathogenesis, even after peripheral inoculation of low doses of Y. pestis. Instead, the effects of YopJ appear to overlap and augment the immunomodulatory effects of other Y. pestis virulence factors.

Interferon antagonist NSs of La Crosse virus triggers a DNA damage response-like degradation of transcribing RNA polymerase II.

PubMed

Verbruggen, Paul; Ruf, Marius; Blakqori, Gjon; Överby, Anna K; Heidemann, Martin; Eick, Dirk; Weber, Friedemann

2011-02-04

La Crosse encephalitis virus (LACV) is a mosquito-borne member of the negative-strand RNA virus family Bunyaviridae. We have previously shown that the virulence factor NSs of LACV is an efficient inhibitor of the antiviral type I interferon system. A recombinant virus unable to express NSs (rLACVdelNSs) strongly induced interferon transcription, whereas the corresponding wt virus (rLACV) suppressed it. Here, we show that interferon induction by rLACVdelNSs mainly occurs through the signaling pathway leading from the pattern recognition receptor RIG-I to the transcription factor IRF-3. NSs expressed by rLACV, however, acts downstream of IRF-3 by specifically blocking RNA polymerase II-dependent transcription. Further investigations revealed that NSs induces proteasomal degradation of the mammalian RNA polymerase II subunit RPB1. NSs thereby selectively targets RPB1 molecules of elongating RNA polymerase II complexes, the so-called IIo form. This phenotype has similarities to the cellular DNA damage response, and NSs was indeed found to transactivate the DNA damage response gene pak6. Moreover, NSs expressed by rLACV boosted serine 139 phosphorylation of histone H2A.X, one of the earliest cellular reactions to damaged DNA. However, other DNA damage response markers such as up-regulation and serine 15 phosphorylation of p53 or serine 1524 phosphorylation of BRCA1 were not triggered by LACV infection. Collectively, our data indicate that the strong suppression of interferon induction by LACV NSs is based on a shutdown of RNA polymerase II transcription and that NSs achieves this by exploiting parts of the cellular DNA damage response pathway to degrade IIo-borne RPB1 subunits.

Headache triggers in the US military.

PubMed

Theeler, Brett J; Kenney, Kimbra; Prokhorenko, Olga A; Fideli, Ulgen S; Campbell, William; Erickson, Jay C

2010-05-01

Headaches can be triggered by a variety of factors. Military service members have a high prevalence of headache but the factors triggering headaches in military troops have not been identified. The objective of this study is to determine headache triggers in soldiers and military beneficiaries seeking specialty care for headaches. A total of 172 consecutive US Army soldiers and military dependents (civilians) evaluated at the headache clinics of 2 US Army Medical Centers completed a standardized questionnaire about their headache triggers. A total of 150 (87%) patients were active-duty military members and 22 (13%) patients were civilians. In total, 77% of subjects had migraine; 89% of patients reported at least one headache trigger with a mean of 8.3 triggers per patient. A wide variety of headache triggers was seen with the most common categories being environmental factors (74%), stress (67%), consumption-related factors (60%), and fatigue-related factors (57%). The types of headache triggers identified in active-duty service members were similar to those seen in civilians. Stress-related triggers were significantly more common in soldiers. There were no significant differences in trigger types between soldiers with and without a history of head trauma. Headaches in military service members are triggered mostly by the same factors as in civilians with stress being the most common trigger. Knowledge of headache triggers may be useful for developing strategies that reduce headache occurrence in the military.

Functional characterization of the role of rpfA in Xylella fastidiosa

USDA-ARS?s Scientific Manuscript database

Xylella fastidiosa coordinates virulence in grapevines via quorum sensing signal molecules that are regulated and synthesized by the rpf gene cluster (regulation of pathogenicity factors). rpfA encodes aconitate hydratase and could play a regulator role involved in virulence. To elucidate the role o...

Extending the durability of cultivar resistance by limiting epidemic growth rates.

PubMed

Carolan, Kevin; Helps, Joe; van den Berg, Femke; Bain, Ruairidh; Paveley, Neil; van den Bosch, Frank

2017-09-27

Cultivar resistance is an essential part of disease control programmes in many agricultural systems. The use of resistant cultivars applies a selection pressure on pathogen populations for the evolution of virulence, resulting in loss of disease control. Various techniques for the deployment of host resistance genes have been proposed to reduce the selection for virulence, but these are often difficult to apply in practice. We present a general technique to maintain the effectiveness of cultivar resistance. Derived from classical population genetics theory; any factor that reduces the population growth rates of both the virulent and avirulent strains will reduce selection. We model the specific example of fungicide application to reduce the growth rates of virulent and avirulent strains of a pathogen, demonstrating that appropriate use of fungicides reduces selection for virulence, prolonging cultivar resistance. This specific example of chemical control illustrates a general principle for the development of techniques to manage the evolution of virulence by slowing epidemic growth rates. © 2017 The Author(s).

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

PubMed

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.

Profile of Virulence Factors in the Multi-Drug Resistant Pseudomonas aeruginosa Strains of Human Urinary Tract Infections (UTI).

PubMed

Habibi, Asghar; Honarmand, Ramin

2015-12-01

Putative virulence factors are responsible for the pathogenicity of UTIs caused by Pseudomonas aeruginosa (P. aeruginosa). Resistance of P. aeruginosa to commonly used antibiotics is caused by the extreme overprescription of those antibiotics. The goal of the present study was to investigate the prevalence of virulence factors and the antibiotic resistance patterns of P. aeruginosa isolates in UTI cases in Iran. Two hundred and fifty urine samples were collected from patients who suffered from UTIs. Samples were cultured immediately, and those that were P. aeruginosa-positive were analyzed for the presence of virulence genes using polymerase chain reaction (PCR) testing. Antimicrobial susceptibility testing (AST) was performed using the disk diffusion method. Of the 250 urine samples analyzed, 8 samples (3.2%) were positive for P. aeruginosa. The prevalence of P. aeruginosa in male and female patients was 2.7% and 3.5%, respectively, (P = 0.035). In patients less than 10 years old, it was 4.2%, and in patients more than 55 years old, it was 4.2%. These were the most commonly infected groups. The highest levels of resistance were seen against ampicillin (87.5%), norfloxacin (62.5%), gentamycin (62.5%), amikacin (62.5%), and aztreonam (62.5%), while the lowest were seen for meropenem (0%), imipenem (12.5%), and polymyxin B (12.5%). LasB (87.5%), pclH (75%), pilB (75%), and exoS (75%) were the most commonly detected virulence factors in the P. aeruginosa isolates. It is logical to first prescribe meropenem, imipenem, and polymyxin B in cases of UTIs caused by P. aeruginosa. Medical practitioners should be aware of the presence of levels of antibiotic resistance in hospitalized UTI patients in Iran.

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

PubMed

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.

Predation on multiple trophic levels shapes the evolution of pathogen virulence.

PubMed

Friman, Ville-Petri; Lindstedt, Carita; Hiltunen, Teppo; Laakso, Jouni; Mappes, Johanna

2009-08-25

The pathogen virulence is traditionally thought to co-evolve as a result of reciprocal selection with its host organism. In natural communities, pathogens and hosts are typically embedded within a web of interactions with other species, which could affect indirectly the pathogen virulence and host immunity through trade-offs. Here we show that selection by predation can affect both pathogen virulence and host immune defence. Exposing opportunistic bacterial pathogen Serratia marcescens to predation by protozoan Tetrahymena thermophila decreased its virulence when measured as host moth Parasemia plantaginis survival. This was probably because the bacterial anti-predatory traits were traded off with bacterial virulence factors, such as motility or resource use efficiency. However, the host survival depended also on its allocation to warning signal that is used against avian predation. When infected with most virulent ancestral bacterial strain, host larvae with a small warning signal survived better than those with an effective large signal. This suggests that larval immune defence could be traded off with effective defence against bird predators. However, the signal size had no effect on larval survival when less virulent control or evolved strains were used for infection suggesting that anti-predatory defence against avian predators, might be less constrained when the invading pathogen is rather low in virulence. Our results demonstrate that predation can be important indirect driver of the evolution of both pathogen virulence and host immunity in communities with multiple species interactions. Thus, the pathogen virulence should be viewed as a result of both past evolutionary history, and current ecological interactions.

Diversities in Virulence, Antifungal Activity, Pigmentation and DNA Fingerprint among Strains of Burkholderia glumae

PubMed Central

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. PMID:23028972

Imaging mass spectrometry and genome mining reveal highly antifungal virulence factor of mushroom soft rot pathogen.

PubMed

Graupner, Katharina; Scherlach, Kirstin; Bretschneider, Tom; Lackner, Gerald; Roth, Martin; Gross, Harald; Hertweck, Christian

2012-12-21

Caught in the act: imaging mass spectrometry of a button mushroom infected with the soft rot pathogen Janthinobacterium agaricidamnosum in conjunction with genome mining revealed jagaricin as a highly antifungal virulence factor that is not produced under standard cultivation conditions. The structure of jagaricin was rigorously elucidated by a combination of physicochemical analyses, chemical derivatization, and bioinformatics. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

FbpA, a novel multifunctional Listeria monocytogenes virulence factor.

PubMed

Dramsi, S; Bourdichon, F; Cabanes, D; Lecuit, M; Fsihi, H; Cossart, P

2004-07-01

Listeria monocytogenes is a Gram-positive intracellular bacterium responsible for severe opportunistic infections in humans and animals. Signature-tagged mutagenesis (STM) was used to identify a gene named fbpA, required for efficient liver colonization of mice inoculated intravenously. FbpA was also shown to be required for intestinal and liver colonization after oral infection of transgenic mice expressing human E-cadherin. fbpA encodes a 570-amino-acid polypeptide that has strong homologies to atypical fibronectin-binding proteins. FbpA binds to immobilized human fibronectin in a dose-dependent and saturable manner and increases adherence of wild-type L. monocytogenes to HEp-2 cells in the presence of exogenous fibronectin. Despite the lack of conventional secretion/anchoring signals, FbpA is detected using an antibody generated against the recombinant FbpA protein on the bacterial surface by immunofluorescence, and in the membrane compartment by Western blot analysis of cell extracts. Strikingly, FbpA expression affects the protein levels of two virulence factors, listeriolysin O (LLO) and InlB, but not that of InlA or ActA. FbpA co-immunoprecipitates with LLO and InlB, but not with InlA or ActA. Thus, FbpA, in addition to being a fibronectin-binding protein, behaves as a chaperone or an escort protein for two important virulence factors and appears as a novel multifunctional virulence factor of L. monocytogenes.

Integrated proteomics, genomics, metabolomics approaches reveal oxalic acid as pathogenicity factor in Tilletia indica inciting Karnal bunt disease of wheat.

PubMed

Pandey, Vishakha; Singh, Manoj; Pandey, Dinesh; Kumar, Anil

2018-05-18

Tilletia indica incites Karnal bunt (KB) disease in wheat. To date, no KB resistant wheat cultivar could be developed due to non-availability of potential biomarkers related to pathogenicity/virulence for screening of resistant wheat genotypes. The present study was carried out to compare the proteomes of T. indica highly (TiK) and low (TiP) virulent isolates. Twenty one protein spots consistently observed as up-regulated/differential in the TiK proteome were selected for identification by MALDI-TOF/TOF. Identified sequences showed homology with fungal proteins playing essential role in plant infection and pathogen survival, including stress response, adhesion, fungal penetration, invasion, colonization, degradation of host cell wall, signal transduction pathway. These results were integrated with T. indica genome sequence for identification of homologs of candidate pathogenicity/virulence related proteins. Protein identified in TiK isolate as malate dehydrogenase that converts malate to oxaloacetate which is precursor of oxalic acid. Oxalic acid is key pathogenicity factor in phytopathogenic fungi. These results were validated by GC-MS based metabolic profiling of T. indica isolates indicating that oxalic acid was exclusively identified in TiK isolate. Thus, integrated omics approaches leads to identification of pathogenicity/virulence factor(s) that would provide insights into pathogenic mechanisms of fungi and aid in devising effective disease management strategies.

Virulence factors in Proteus bacteria from biofilm communities of catheter-associated urinary tract infections.

PubMed

Hola, Veronika; Peroutkova, Tereza; Ruzicka, Filip

2012-07-01

More than 40% of nosocomial infections are those of the urinary tract, most of these occurring in catheterized patients. Bacterial colonization of the urinary tract and catheters results not only in infection, but also various complications, such as blockage of catheters with crystalline deposits of bacterial origin, generation of gravels and pyelonephritis. The diversity of the biofilm microbial community increases with duration of catheter emplacement. One of the most important pathogens in this regard is Proteus mirabilis. The aims of this study were to identify and assess particular virulence factors present in catheter-associated urinary tract infection (CAUTI) isolates, their correlation and linkages: three types of motility (swarming, swimming and twitching), the ability to swarm over urinary catheters, biofilm production in two types of media, urease production and adherence of bacterial cells to various types of urinary tract catheters. We examined 102 CAUTI isolates and 50 isolates taken from stool samples of healthy people. Among the microorganisms isolated from urinary catheters, significant differences were found in biofilm-forming ability and the swarming motility. In comparison with the control group, the microorganisms isolated from urinary catheters showed a wider spectrum of virulence factors. The virulence factors (twitching motility, swimming motility, swarming over various types of catheters and biofilm formation) were also more intensively expressed. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Genomes and Virulence Factors of Novel Bacterial Pathogens Causing Bleaching Disease in the Marine Red Alga Delisea pulchra

PubMed Central

Fernandes, Neil; Case, Rebecca J.; Longford, Sharon R.; Seyedsayamdost, Mohammad R.; Steinberg, Peter D.; Kjelleberg, Staffan; Thomas, Torsten

2011-01-01

Nautella sp. R11, a member of the marine Roseobacter clade, causes a bleaching disease in the temperate-marine red macroalga, Delisea pulchra. To begin to elucidate the molecular mechanisms underpinning the ability of Nautella sp. R11 to colonize, invade and induce bleaching of D. pulchra, we sequenced and analyzed its genome. The genome encodes several factors such as adhesion mechanisms, systems for the transport of algal metabolites, enzymes that confer resistance to oxidative stress, cytolysins, and global regulatory mechanisms that may allow for the switch of Nautella sp. R11 to a pathogenic lifestyle. Many virulence effectors common in phytopathogenic bacteria are also found in the R11 genome, such as the plant hormone indole acetic acid, cellulose fibrils, succinoglycan and nodulation protein L. Comparative genomics with non-pathogenic Roseobacter strains and a newly identified pathogen, Phaeobacter sp. LSS9, revealed a patchy distribution of putative virulence factors in all genomes, but also led to the identification of a quorum sensing (QS) dependent transcriptional regulator that was unique to pathogenic Roseobacter strains. This observation supports the model that a combination of virulence factors and QS-dependent regulatory mechanisms enables indigenous members of the host alga's epiphytic microbial community to switch to a pathogenic lifestyle, especially under environmental conditions when innate host defence mechanisms are compromised. PMID:22162749

The Eng1 β-Glucanase Enhances Histoplasma Virulence by Reducing β-Glucan Exposure

PubMed Central

Garfoot, Andrew L.; Shen, Qian; Wüthrich, Marcel; Klein, Bruce S.

2016-01-01

ABSTRACT The fungal pathogen Histoplasma capsulatum parasitizes host phagocytes. To avoid antimicrobial immune responses, Histoplasma yeasts must minimize their detection by host receptors while simultaneously interacting with the phagocyte. Pathogenic Histoplasma yeast cells, but not avirulent mycelial cells, secrete the Eng1 protein, which is a member of the glycosylhydrolase 81 (GH81) family. We show that Histoplasma Eng1 is a glucanase that hydrolyzes β-(1,3)-glycosyl linkages but is not required for Histoplasma growth in vitro or for cell separation. However, Histoplasma yeasts lacking Eng1 function have attenuated virulence in vivo, particularly during the cell-mediated immunity stage. Histoplasma yeasts deficient for Eng1 show increased exposure of cell wall β-glucans, which results in enhanced binding to the Dectin-1 β-glucan receptor. Consistent with this, Eng1-deficient yeasts trigger increased tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) cytokine production from macrophages and dendritic cells. While not responsible for large-scale cell wall structure and function, the secreted Eng1 reduces levels of exposed β-glucans at the yeast cell wall, thereby diminishing potential recognition by Dectin-1 and proinflammatory cytokine production by phagocytes. In α-glucan-producing Histoplasma strains, Eng1 acts in concert with α-glucan to minimize β-glucan exposure: α-glucan provides a masking function by covering the β-glucan-rich cell wall, while Eng1 removes any remaining exposed β-glucans. Thus, Histoplasma Eng1 has evolved a specialized pathogenesis function to remove exposed β-glucans, thereby enhancing the ability of yeasts to escape detection by host phagocytes. PMID:27094334

High levels of cyclic-di-GMP in plant-associated Pseudomonas correlate with evasion of plant immunity.

PubMed

Pfeilmeier, Sebastian; Saur, Isabel Marie-Luise; Rathjen, John Paul; Zipfel, Cyril; Malone, Jacob George

2016-05-01

The plant innate immune system employs plasma membrane-localized receptors that specifically perceive pathogen/microbe-associated molecular patterns (PAMPs/MAMPs). This induces a defence response called pattern-triggered immunity (PTI) to fend off pathogen attack. Commensal bacteria are also exposed to potential immune recognition and must employ strategies to evade and/or suppress PTI to successfully colonize the plant. During plant infection, the flagellum has an ambiguous role, acting as both a virulence factor and also as a potent immunogen as a result of the recognition of its main building block, flagellin, by the plant pattern recognition receptors (PRRs), including FLAGELLIN SENSING2 (FLS2). Therefore, strict control of flagella synthesis is especially important for plant-associated bacteria. Here, we show that cyclic-di-GMP [bis-(3'-5')-cyclic di-guanosine monophosphate], a central regulator of bacterial lifestyle, is involved in the evasion of PTI. Elevated cyclic-di-GMP levels in the pathogen Pseudomonas syringae pv. tomato (Pto) DC3000, the opportunist P. aeruginosa PAO1 and the commensal P. protegens Pf-5 inhibit flagellin synthesis and help the bacteria to evade FLS2-mediated signalling in Nicotiana benthamiana and Arabidopsis thaliana. Despite this, high cellular cyclic-di-GMP concentrations were shown to drastically reduce the virulence of Pto DC3000 during plant infection. We propose that this is a result of reduced flagellar motility and/or additional pleiotropic effects of cyclic-di-GMP signalling on bacterial behaviour. © 2015 THE AUTHORS MOLECULAR PLANT PATHOLOGY PUBLISHED BY BRITISH SOCIETY FOR PLANT PATHOLOGY AND JOHN WILEY & SONS LTD.

Production of the Catechol Type Siderophore Bacillibactin by the Honey Bee Pathogen Paenibacillus larvae

PubMed Central

Garcia-Gonzalez, Eva; Poppinga, Lena; Süssmuth, Roderich D.; Genersch, Elke

2014-01-01

The Gram-positive bacterium Paenibacillus larvae is the etiological agent of American Foulbrood. This bacterial infection of honey bee brood is a notifiable epizootic posing a serious threat to global honey bee health because not only individual larvae but also entire colonies succumb to the disease. In the recent past considerable progress has been made in elucidating molecular aspects of host pathogen interactions during pathogenesis of P. larvae infections. Especially the sequencing and annotation of the complete genome of P. larvae was a major step forward and revealed the existence of several giant gene clusters coding for non-ribosomal peptide synthetases which might act as putative virulence factors. We here present the detailed analysis of one of these clusters which we demonstrated to be responsible for the biosynthesis of bacillibactin, a P. larvae siderophore. We first established culture conditions allowing the growth of P. larvae under iron-limited conditions and triggering siderophore production by P. larvae. Using a gene disruption strategy we linked siderophore production to the expression of an uninterrupted bacillibactin gene cluster. In silico analysis predicted the structure of a trimeric trithreonyl lactone (DHB-Gly-Thr)3 similar to the structure of bacillibactin produced by several Bacillus species. Mass spectrometric analysis unambiguously confirmed that the siderophore produced by P. larvae is identical to bacillibactin. Exposure bioassays demonstrated that P. larvae bacillibactin is not required for full virulence of P. larvae in laboratory exposure bioassays. This observation is consistent with results obtained for bacillibactin in other pathogenic bacteria. PMID:25237888

A comparative proteome analysis reveals flagellin, chemotaxis regulated proteins and amylovoran to be involved in virulence differences between Erwinia amylovora strains.

PubMed

Holtappels, M; Vrancken, K; Schoofs, H; Deckers, T; Remans, T; Noben, J P; Valcke, R

2015-06-18

Erwinia amylovora is a Gram-negative bacterium that causes the destructive disease fire blight affecting most members of the Rosaceae family, of which apple and pear are economically the most important hosts. E. amylovora has been considered as a homogeneous species in whole, although significant differences in virulence patterns have been observed. However, the underlying causes of the differences in virulence remain to be discovered. In a first-time comparative proteomic approach using E. amylovora, 2D differential in-gel electrophoresis (DIGE) was used to identify proteins that could explain the gradual difference in virulence between four different strains. Two important proteins were identified, FliC and CheY, both involved in flagella structure, motility and chemotaxis, which were more abundant in the least virulent strain. In the highly virulent strains the protein GalF, involved in amylovoran production, was more abundant, which was consistent with the higher expression of the gene and the higher amylovoran content in this strain in vitro. Together, these results confirm the involvement of amylovoran in virulence, but also imply an indirect role of flagellin in virulence as elicitor of plant defence. This research provides new insights into our current understanding of the virulence of Erwinia amylovora. This plant-pathogen is considered a homogeneous species although different strains show differences in virulence. Despite the efforts made on the genomic level which resulted in the discovery of virulence factors, the reason for the different virulence patterns between strains has not yet been identified. In our lab we used a comparative proteomic approach, which has never been published before, to identify proteins involved in these differences between strains and hereby possibly involved in virulence. Our results provide interesting insights in virulence and present us with the opportunity to glance into the proteome of E. amylovora. Copyright © 2015. Published by Elsevier B.V.

Fungal phytotoxins as mediators of virulence.

PubMed

Möbius, Nadine; Hertweck, Christian

2009-08-01

Many phytopathogenic fungi exert their destructive effects by producing and secreting toxic low molecular weight compounds. In the past years a large number of novel fungal virulence factors and their modes of action have been identified. This review highlights effective phytotoxin-mediated strategies to distress, weaken or kill the plant host.

Chitin degradation and utilization by virulent Aeromonas hydrophila strain ML10-51K

USDA-ARS?s Scientific Manuscript database

Virulent Aeromonas hydrophila (vAh) is one of the most important bacterial pathogens that causes persistent outbreaks of motile Aeromonas septicemia (MAS) in warm-water fishes. Among factors associated with MAS outbreaks, the survivability of this pathogen in aquatic environments is of great concern...

Importance of Flagella and Enterotoxins for Aeromonas Virulence in a Mouse Model

EPA Science Inventory

A genetic characterization of eight virulence factor genes, elastase, lipase, polar flagella (flaA/flaB, flaG), lateral flagella (lafA), and the enterotoxins alt, act, and ast, was performed using polymerase chain reaction with 55 drinking water and nine clinical isolates. When 1...

Allele-dependent differences in quorum-sensing dynamics result in variant expression of virulence genes in Staphylococcus aureus.

PubMed

Geisinger, Edward; Chen, John; Novick, Richard P

2012-06-01

Agr is an autoinducing, quorum-sensing system that functions in many Gram-positive species and is best characterized in the pathogen Staphylococcus aureus, in which it is a global regulator of virulence gene expression. Allelic variations in the agr genes have resulted in the emergence of four quorum-sensing specificity groups in S. aureus, which correlate with different strain pathotypes. The basis for these predilections is unclear but is hypothesized to involve the phenomenon of quorum-sensing interference between strains of different agr groups, which may drive S. aureus strain isolation and divergence. Whether properties intrinsic to each agr allele directly influence virulence phenotypes within S. aureus is unknown. In this study, we examined group-specific differences in agr autoinduction and virulence gene regulation by utilizing congenic strains, each harboring a unique S. aureus agr allele, enabling a dissection of agr locus-dependent versus genotype-dependent effects on quorum-sensing dynamics and virulence factor production. Employing a reporter fusion to the principal agr promoter, P3, we observed allele-dependent differences in the timing and magnitude of agr activation. These differences were mediated by polymorphisms within the agrBDCA genes and translated to significant variations in the expression of a key transcriptional regulator, Rot, and of several important exoproteins and surface factors involved in pathogenesis. This work uncovers the contribution of divergent quorum-sensing alleles to variant expression of virulence determinants within a bacterial species.

Bacterial Prostatitis: Bacterial Virulence, Clinical Outcomes, and New Directions.

PubMed

Krieger, John N; Thumbikat, Praveen

2016-02-01

Four prostatitis syndromes are recognized clinically: acute bacterial prostatitis, chronic bacterial prostatitis, chronic prostatitis/chronic pelvic pain syndrome, and asymptomatic prostatitis. Because Escherichia coli represents the most common cause of bacterial prostatitis, we investigated the importance of bacterial virulence factors and antimicrobial resistance in E. coli strains causing prostatitis and the potential association of these characteristics with clinical outcomes. A structured literature review revealed that we have limited understanding of the virulence-associated characteristics of E. coli causing acute prostatitis. Therefore, we completed a comprehensive microbiological and molecular investigation of a unique strain collection isolated from healthy young men. We also considered new data from an animal model system suggesting certain E. coli might prove important in the etiology of chronic prostatitis/chronic pelvic pain syndrome. Our human data suggest that E. coli needs multiple pathogenicity-associated traits to overcome anatomic and immune responses in healthy young men without urological risk factors. The phylogenetic background and accumulation of an exceptional repertoire of extraintestinal pathogenic virulence-associated genes indicate that these E. coli strains belong to a highly virulent subset of uropathogenic variants. In contrast, antibiotic resistance confers little added advantage to E. coli strains in these healthy outpatients. Our animal model data also suggest that certain pathogenic E. coli may be important in the etiology of chronic prostatitis/chronic pelvic pain syndrome through mechanisms that are dependent on the host genetic background and the virulence of the bacterial strain.

Comparative genomics reveals cotton-specific virulence factors in flexible genomic regions in Verticillium dahliae and evidence of horizontal gene transfer from Fusarium.

PubMed

Chen, Jie-Yin; Liu, Chun; Gui, Yue-Jing; Si, Kai-Wei; Zhang, Dan-Dan; Wang, Jie; Short, Dylan P G; Huang, Jin-Qun; Li, Nan-Yang; Liang, Yong; Zhang, Wen-Qi; Yang, Lin; Ma, Xue-Feng; Li, Ting-Gang; Zhou, Lei; Wang, Bao-Li; Bao, Yu-Ming; Subbarao, Krishna V; Zhang, Geng-Yun; Dai, Xiao-Feng

2018-01-01

Verticillium dahliae isolates are most virulent on the host from which they were originally isolated. Mechanisms underlying these dominant host adaptations are currently unknown. We sequenced the genome of V. dahliae Vd991, which is highly virulent on its original host, cotton, and performed comparisons with the reference genomes of JR2 (from tomato) and VdLs.17 (from lettuce). Pathogenicity-related factor prediction, orthology and multigene family classification, transcriptome analyses, phylogenetic analyses, and pathogenicity experiments were performed. The Vd991 genome harbored several exclusive, lineage-specific (LS) genes within LS regions (LSRs). Deletion mutants of the seven genes within one LSR (G-LSR2) in Vd991 were less virulent only on cotton. Integration of G-LSR2 genes individually into JR2 and VdLs.17 resulted in significantly enhanced virulence on cotton but did not affect virulence on tomato or lettuce. Transcription levels of the seven LS genes in Vd991 were higher during the early stages of cotton infection, as compared with other hosts. Phylogenetic analyses suggested that G-LSR2 was acquired from Fusarium oxysporum f. sp. vasinfectum through horizontal gene transfer. Our results provide evidence that horizontal gene transfer from Fusarium to Vd991 contributed significantly to its adaptation to cotton and may represent a significant mechanism in the evolution of an asexual plant pathogen. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Metabolic sensor governing bacterial virulence in Staphylococcus aureus.

PubMed

Ding, Yue; Liu, Xing; Chen, Feifei; Di, Hongxia; Xu, Bin; Zhou, Lu; Deng, Xin; Wu, Min; Yang, Cai-Guang; Lan, Lefu

2014-11-18

An effective metabolism is essential to all living organisms, including the important human pathogen Staphylococcus aureus. To establish successful infection, S. aureus must scavenge nutrients and coordinate its metabolism for proliferation. Meanwhile, it also must produce an array of virulence factors to interfere with host defenses. However, the ways in which S. aureus ties its metabolic state to its virulence regulation remain largely unknown. Here we show that citrate, the first intermediate of the tricarboxylic acid (TCA) cycle, binds to and activates the catabolite control protein E (CcpE) of S. aureus. Using structural and site-directed mutagenesis studies, we demonstrate that two arginine residues (Arg145 and Arg256) within the putative inducer-binding cavity of CcpE are important for its allosteric activation by citrate. Microarray analysis reveals that CcpE tunes the expression of 126 genes that comprise about 4.7% of the S. aureus genome. Intriguingly, although CcpE is a major positive regulator of the TCA-cycle activity, its regulon consists predominantly of genes involved in the pathogenesis of S. aureus. Moreover, inactivation of CcpE results in increased staphyloxanthin production, improved ability to acquire iron, increased resistance to whole-blood-mediated killing, and enhanced bacterial virulence in a mouse model of systemic infection. This study reveals CcpE as an important metabolic sensor that allows S. aureus to sense and adjust its metabolic state and subsequently to coordinate the expression of virulence factors and bacterial virulence.

Escherichia coli msbB gene as a virulence factor and a therapeutic target.

PubMed

Somerville, J E; Cassiano, L; Darveau, R P

1999-12-01

A mutation in the msbB gene of Escherichia coli results in the synthesis of E. coli lipopolysaccharide (LPS) that lacks the myristic acid moiety of lipid A. Although such mutant E. coli cells and their purified LPS have a greatly reduced ability to stimulate human immune cells, a minor reduction in the mouse inflammatory response is observed. When the msbB mutation is transferred into a clinical isolate of E. coli, there is a significant loss in virulence, as assessed by lethality in BALB/c mice. When a cloned msbB gene is provided to functionally complement the msbB mutant, virulence returns, providing direct evidence that the msbB gene product is an important virulence factor in a murine model of E. coli pathogenicity. In the genetic background of the clinical E. coli isolate, the msbB mutation also results in filamentation of the cells at 37 degrees C but not at 30 degrees C, a reduction in the level of the K1 capsule, an increase in the level of complement C3 deposition, and an increase in both opsonic and nonopsonic phagocytosis of the msbB mutant, phenotypes that can help to explain the loss in virulence. The demonstration that the inhibition of msbB gene function reduces the virulence of E. coli in a mouse infection model warrants further investigation of the msbB gene product as a novel target for antibiotic therapy.

Identification of virulence determinants for endocarditis in Streptococcus sanguinis by signature-tagged mutagenesis.

PubMed

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†

PubMed Central

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

The DSF Family of Cell–Cell Signals: An Expanding Class of Bacterial Virulence Regulators

PubMed Central

Ryan, Robert P.; An, Shi-qi; Allan, John H.; McCarthy, Yvonne; Dow, J. Maxwell

2015-01-01

Many pathogenic bacteria use cell–cell signaling systems involving the synthesis and perception of diffusible signal molecules to control virulence as a response to cell density or confinement to niches. Bacteria produce signals of diverse structural classes. Signal molecules of the diffusible signal factor (DSF) family are cis-2-unsaturated fatty acids. The paradigm is cis-11-methyl-2-dodecenoic acid from Xanthomonas campestris pv. campestris (Xcc), which controls virulence in this plant pathogen. Although DSF synthesis was thought to be restricted to the xanthomonads, it is now known that structurally related molecules are produced by the unrelated bacteria Burkholderia cenocepacia and Pseudomonas aeruginosa. Furthermore, signaling involving these DSF family members contributes to bacterial virulence, formation of biofilms and antibiotic tolerance in these important human pathogens. Here we review the recent advances in understanding DSF signaling and its regulatory role in different bacteria. These advances include the description of the pathway/mechanism of DSF biosynthesis, identification of novel DSF synthases and new members of the DSF family, the demonstration of a diversity of DSF sensors to include proteins with a Per-Arnt-Sim (PAS) domain and the description of some of the signal transduction mechanisms that impinge on virulence factor expression. In addition, we address the role of DSF family signals in interspecies signaling that modulates the behavior of other microorganisms. Finally, we consider a number of recently reported approaches for the control of bacterial virulence through the modulation of DSF signaling. PMID:26181439

The HD-GYP Domain Protein RpfG of Xanthomonas oryzae pv. oryzicola Regulates Synthesis of Extracellular Polysaccharides that Contribute to Biofilm Formation and Virulence on Rice

PubMed Central

Zhang, Yuanbao; Wei, Chao; Jiang, Wendi; Wang, Lei; Li, Churui; Wang, Yunyue; Dow, John Maxwell; Sun, Wenxian

2013-01-01

Bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola (Xoc) is one of the most important diseases in rice. However, little is known about the pathogenicity mechanisms of Xoc. Here we have investigated the function of three HD-GYP domain regulatory proteins in biofilm formation, the synthesis of virulence factors and virulence of Xoc. Deletion of rpfG resulted in altered production of extracellular polysaccharides (EPS), abolished virulence on rice and enhanced biofilm formation, but had little effect on the secretion of proteases and motility. In contrast, mutational analysis showed that the other two HD-GYP domain proteins had no effect on virulence factor synthesis and tested phenotypes. Mutation of rpfG led to up-regulation of the type III secretion system and altered expression of three putative glycosyltransferase genes gumD, pgaC and xagB, which are part of operons directing the synthesis of different extracellular polysaccharides. The pgaABCD and xagABCD operons were greatly up-regulated in the Xoc ΔrpfG mutant, whereas the expression of the gum genes was unaltered or slightly enhanced. The elevated biofilm formation of the Xoc ΔrpfG mutant was dramatically reduced upon deletion of gumD, xagA and xagB, but not when pgaA and pgaC were deleted. Interestingly, only the ΔgumD mutant, among these single gene mutants, exhibits multiple phenotype alterations including reduced biofilm and EPS production and attenuated virulence on rice. These data indicate that RpfG is a global regulator that controls biofilm formation, EPS production and bacterial virulence in Xoc and that both gumD- and xagB-dependent EPS contribute to biofilm formation under different conditions. PMID:23544067

The Absence of N-Acetyl-D-glucosamine Causes Attenuation of Virulence of Candida albicans upon Interaction with Vaginal Epithelial Cells In Vitro

PubMed Central

Manczinger, Máté; Bocsik, Alexandra; Kocsis, Gabriella F.; Vörös, Andrea; Hegedűs, Zoltán; Marton, Annamária; Vízler, Csaba; Tubak, Vilmos; Deli, Mária; Kemény, Lajos; Nagy, István; Lakatos, Lóránt

2015-01-01

To better understand the molecular events underlying vulvovaginal candidiasis, we established an in vitro system. Immortalized vaginal epithelial cells were infected with live, yeast form C. albicans and C. albicans cultured in the same medium without vaginal epithelial cells were used as control. In both cases a yeast to hyphae transition was robustly induced. Whole transcriptome sequencing was used to identify specific gene expression changes in C. albicans. Numerous genes leading to a yeast to hyphae transition and hyphae specific genes were upregulated in the control hyphae and the hyphae in response to vaginal epithelial cells. Strikingly, the GlcNAc pathway was exclusively triggered by vaginal epithelial cells. Functional analysis in our in vitro system revealed that the GlcNAc biosynthesis is involved in the adherence to, and the ability to kill, vaginal epithelial cells in vitro, thus indicating the key role for this pathway in the virulence of C. albicans upon vulvovaginal candidiasis. PMID:26366412

Expanded functions for a family of plant intracellular immune receptors beyond specific recognition of pathogen effectors

PubMed Central

Bonardi, Vera; Tang, Saijun; Stallmann, Anna; Roberts, Melinda; Cherkis, Karen; Dangl, Jeffery L.

2011-01-01

Plants and animals deploy intracellular immune receptors that perceive specific pathogen effector proteins and microbial products delivered into the host cell. We demonstrate that the ADR1 family of Arabidopsis nucleotide-binding leucine-rich repeat (NB-LRR) receptors regulates accumulation of the defense hormone salicylic acid during three different types of immune response: (i) ADRs are required as “helper NB-LRRs” to transduce signals downstream of specific NB-LRR receptor activation during effector-triggered immunity; (ii) ADRs are required for basal defense against virulent pathogens; and (iii) ADRs regulate microbial-associated molecular pattern-dependent salicylic acid accumulation induced by infection with a disarmed pathogen. Remarkably, these functions do not require an intact P-loop motif for at least one ADR1 family member. Our results suggest that some NB-LRR proteins can serve additional functions beyond canonical, P-loop–dependent activation by specific virulence effectors, extending analogies between intracellular innate immune receptor function from plants and animals. PMID:21911370

Conjugated Linoleic Acid Reduces Cholera Toxin Production In Vitro and In Vivo by Inhibiting Vibrio cholerae ToxT Activity.

PubMed

Withey, Jeffrey H; Nag, Drubhajyoti; Plecha, Sarah C; Sinha, Ritam; Koley, Hemanta

2015-12-01

The severe diarrheal disease cholera is endemic in over 50 countries. Current therapies for cholera patients involve oral and/or intravenous rehydration, often combined with the use of antibiotics to shorten the duration and intensity of the disease. However, as antibiotic resistance increases, treatment options will become limited. Linoleic acid has been shown to be a potent negative effector of V. cholerae virulence that acts on the major virulence transcription regulator protein, ToxT, to inhibit virulence gene expression. ToxT activates transcription of the two major virulence factors required for disease, cholera toxin (CT) and toxin-coregulated pilus (TCP). A conjugated form of linoleic acid (CLA) is currently sold over the counter as a dietary supplement and is generally recognized as safe by the U.S. Food and Drug Administration. This study examined whether CLA could be used as a new therapy to reduce CT production, which, in turn, would decrease disease duration and intensity in cholera patients. CLA could be used in place of traditional antibiotics and would be very unlikely to generate resistance, as it affects only virulence factor production and not bacterial growth or survival. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Bacterial Pathogens and Community Composition in Advanced Sewage Treatment Systems Revealed by Metagenomics Analysis Based on High-Throughput Sequencing

PubMed Central

Lu, Xin; Zhang, Xu-Xiang; Wang, Zhu; Huang, Kailong; Wang, Yuan; Liang, Weigang; Tan, Yunfei; Liu, Bo; Tang, Junying

2015-01-01

This study used 454 pyrosequencing, Illumina high-throughput sequencing and metagenomic analysis to investigate bacterial pathogens and their potential virulence in a sewage treatment plant (STP) applying both conventional and advanced treatment processes. Pyrosequencing and Illumina sequencing consistently demonstrated that Arcobacter genus occupied over 43.42% of total abundance of potential pathogens in the STP. At species level, potential pathogens Arcobacter butzleri, Aeromonas hydrophila and Klebsiella pneumonia dominated in raw sewage, which was also confirmed by quantitative real time PCR. Illumina sequencing also revealed prevalence of various types of pathogenicity islands and virulence proteins in the STP. Most of the potential pathogens and virulence factors were eliminated in the STP, and the removal efficiency mainly depended on oxidation ditch. Compared with sand filtration, magnetic resin seemed to have higher removals in most of the potential pathogens and virulence factors. However, presence of the residual A. butzleri in the final effluent still deserves more concerns. The findings indicate that sewage acts as an important source of environmental pathogens, but STPs can effectively control their spread in the environment. Joint use of the high-throughput sequencing technologies is considered a reliable method for deep and comprehensive overview of environmental bacterial virulence. PMID:25938416

Vanillic acid from Actinidia deliciosa impedes virulence in Serratia marcescens by affecting S-layer, flagellin and fatty acid biosynthesis proteins.

PubMed

Sethupathy, Sivasamy; Ananthi, Sivagnanam; Selvaraj, Anthonymuthu; Shanmuganathan, Balakrishnan; Vigneshwari, Loganathan; Balamurugan, Krishnaswamy; Mahalingam, Sundarasamy; Pandian, Shunmugiah Karutha

2017-11-27

Serratia marcescens is one of the important nosocomial pathogens which rely on quorum sensing (QS) to regulate the production of biofilm and several virulence factors. Hence, blocking of QS has become a promising approach to quench the virulence of S. marcescens. For the first time, QS inhibitory (QSI) and antibiofilm potential of Actinidia deliciosa have been explored against S. marcescens clinical isolate (CI). A. deliciosa pulp extract significantly inhibited the virulence and biofilm production without any deleterious effect on the growth. Vanillic acid was identified as an active lead responsible for the QSI activity. Addition of vanillic acid to the growth medium significantly affected the QS regulated production of biofilm and virulence factors in a concentration dependent mode in S. marcescens CI, ATCC 14756 and MG1. Furthermore vanillic acid increased the survival of Caenorhabditis elegans upon S. marcescens infection. Proteomic analysis and mass spectrometric identification of differentially expressed proteins revealed the ability of vanillic acid to modulate the expression of proteins involved in S-layers, histidine, flagellin and fatty acid production. QSI potential of the vanillic acid observed in the current study paves the way for exploring it as a potential therapeutic candidate to treat S. marcescens infections.

Phenotypic Characteristics Associated with Virulence of Clinical Isolates from the Sporothrix Complex

PubMed Central

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

Multiple activities of the plant pathogen type III effector proteins WtsE and AvrE require WxxxE motifs.

PubMed

Ham, Jong Hyun; Majerczak, Doris R; Nomura, Kinya; Mecey, Christy; Uribe, Francisco; He, Sheng-Yang; Mackey, David; Coplin, David L

2009-06-01

The broadly conserved AvrE-family of type III effectors from gram-negative plant-pathogenic bacteria includes important virulence factors, yet little is known about the mechanisms by which these effectors function inside plant cells to promote disease. We have identified two conserved motifs in AvrE-family effectors: a WxxxE motif and a putative C-terminal endoplasmic reticulum membrane retention/retrieval signal (ERMRS). The WxxxE and ERMRS motifs are both required for the virulence activities of WtsE and AvrE, which are major virulence factors of the corn pathogen Pantoea stewartii subsp. stewartii and the tomato or Arabidopsis pathogen Pseudomonas syringae pv. tomato, respectively. The WxxxE and the predicted ERMRS motifs are also required for other biological activities of WtsE, including elicitation of the hypersensitive response in nonhost plants and suppression of defense responses in Arabidopsis. A family of type III effectors from mammalian bacterial pathogens requires WxxxE and subcellular targeting motifs for virulence functions that involve their ability to mimic activated G-proteins. The conservation of related motifs and their necessity for the function of type III effectors from plant pathogens indicates that disturbing host pathways by mimicking activated host G-proteins may be a virulence mechanism employed by plant pathogens as well.

Inhibition of Cronobacter sakazakii Virulence Factors by Citral

PubMed Central

Shi, Chao; Sun, Yi; Liu, Zhiyuan; Guo, Du; Sun, Huihui; Sun, Zheng; Chen, Shan; Zhang, Wenting; Wen, Qiwu; Peng, Xiaoli; Xia, Xiaodong

2017-01-01

Cronobacter sakazakii is a foodborne pathogen associated with fatal forms of necrotizing enterocolitis, meningitis and sepsis in neonates and infants. The aim of this study was to determine whether citral, a major component of lemongrass oil, could suppress putative virulence factors of C. sakazakii that contribute to infection. Sub-inhibitory concentrations of citral significantly decreased motility, quorum sensing, biofilm formation and endotoxin production. Citral substantially reduced the adhesion and invasion of C. sakazakii to Caco-2 cells and decreased bacterial survival and replication within the RAW 264.7 macrophage cells. Citral also repressed the expression of eighteen genes involved in the virulence. These findings suggest that citral has potential to be developed as an alternative or supplemental agent to mitigate the infections caused by C. sakazakii. PMID:28233814

Cold Plasma Inactivation of Bacterial Biofilms and Reduction of Quorum Sensing Regulated Virulence Factors

PubMed Central

Ziuzina, Dana; Boehm, Daniela; Patil, Sonal; Cullen, P. J.; Bourke, Paula

2015-01-01

The main objectives of this work were to investigate the effect of atmospheric cold plasma (ACP) against a range of microbial biofilms commonly implicated in foodborne and healthcare associated human infections and against P. aeruginosa quorum sensing (QS)-regulated virulence factors, such as pyocyanin, elastase (Las B) and biofilm formation capacity post-ACP treatment. The effect of processing factors, namely treatment time and mode of plasma exposure on antimicrobial activity of ACP were also examined. Antibiofilm activity was assessed for E. coli, L. monocytogenes and S. aureus in terms of reduction of culturability and retention of metabolic activity using colony count and XTT assays, respectively. All samples were treated ‘inpack’ using sealed polypropylene containers with a high voltage dielectric barrier discharge ACP generated at 80 kV for 0, 60, 120 and 300 s and a post treatment storage time of 24 h. According to colony counts, ACP treatment for 60 s reduced populations of E. coli to undetectable levels, whereas 300 s was necessary to significantly reduce populations of L. monocytogenes and S. aureus biofilms. The results obtained from XTT assay indicated possible induction of viable but non culturable state of bacteria. With respect to P. aeruginosa QS-related virulence factors, the production of pyocyanin was significantly inhibited after short treatment times, but reduction of elastase was notable only after 300 s and no reduction in actual biofilm formation was achieved post-ACP treatment. Importantly, reduction of virulence factors was associated with reduction of the cytotoxic effects of the bacterial supernatant on CHO-K1 cells, regardless of mode and duration of treatment. The results of this study point to ACP technology as an effective strategy for inactivation of established biofilms and may play an important role in attenuation of virulence of pathogenic bacteria. Further investigation is warranted to propose direct evidence for the inhibition of QS and mechanisms by which this may occur. PMID:26390435

Genetic relatedness and virulence factors of bovine Staphylococcus aureus isolated from teat skin and milk.

PubMed

da Costa, L B; Rajala-Schultz, P J; Hoet, A; Seo, K S; Fogt, K; Moon, B S

2014-11-01

The objective of this study was to assess the role of teat skin colonization in Staphylococcus aureus intramammary infections (IMI) by evaluating genetic relatedness of Staph. aureus isolates from milk and teat skin of dairy cows using pulsed-field gel electrophoresis and characterizing the isolates based on the carriage of virulence genes. Cows in 4 known Staph. aureus-positive herds were sampled and Staph. aureus was detected in 43 quarters of 20 cows, with 10 quarters positive in both milk and skin (20 isolates), 18 positive only in milk, and 15 only on teat skin. Quarters with teat skin colonized with Staph. aureus were 4.5 times more likely to be diagnosed with Staph. aureus IMI than quarters not colonized on teat skin. Three main clusters were identified by pulsed-field gel electrophoresis using a cutoff of 80% similarity. All 3 clusters included both milk and skin isolates. The majority of isolates (72%) belonged to one predominant cluster (B), with 60% of isolates in the cluster originating from milk and 40% from teat skin. Genotypic variability was observed within 10 pairs (formed by isolates originating from milk and teat skin of the same quarter), where isolates in 5 out of the 10 pairs belonged to the same cluster. Forty-two virulence factors were screened using PCR. Some virulence factors were carried more frequently by teat skin isolates than by milk isolates or isolates from quarters with high somatic cell counts. Isolates in the predominant cluster B carried virulence factors clfA and clfB significantly more often than isolates in the minor clusters, which may have assisted them in becoming predominant in the herds. The present findings suggest that teat skin colonization with Staph. aureus can be an important factor involved in Staph. aureus IMI. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Effect of antibiotic prophylaxis on Coagulase-negative Staphylococcus virulence factor profiles in patients undergoing cataract surgery.

PubMed

López, Yolanda; Samudio, Margarita; Fariña, Norma; Castillo, Verónica; Abente, Sonia; Nentwich, Martin M; González-Britez, Nilsa; Laspina, Florentina; Carron, Agustín; Cibils, Diógenes; de Kaspar, Herminia Miño

2017-08-01

In this prospective study, multiplex polymerase chain reaction (PCR) was used to identify genes encoding virulence factors (ica, atlE and mecA) in Coagulase-negative Staphylococcus (CNS) isolates from the ocular microbiota of patients undergoing cataract surgery and to investigate possible changes in the CNS profile due to antibiotic prophylaxis. Between 09/2011 and 08/2013, patients undergoing cataract surgery were recruited at the Department of Ophthalmology, National University of Asuncion, Paraguay. In the eye to be operated on, patients received moxifloxacin 0.5 % eye drops four times at the day before surgery and a last drop 1 hour before surgery (T1). The other eye remained as control (T0). Conjunctival swabs were taken from both eyes 1 hour after the last drop. The presence of genes encoding biofilm formation (ica and atlE) and methicillin resistance (mecA) was detected by a multiplex PCR. Of the 162 patients (162 study eyes, 162 fellow eye as control group), 87 (53.7 %) eyes were positive for CNS at T0 yielding 96 CNS isolates; 70 eyes (43.2 %) were positive at T1 yielding 77 CNS isolates. For this study, 43 CNS isolates (44.8 %) from T0 and 45 (64.3 %) from T1 were used. Of the total isolates, 81.8 % (72/88) had at least one virulence factor gene (37/43 from T0 and 35/45 from T1) (p = 0.314). Simultaneous detection of ica and atlE genes was higher in T0 (58.0 %) than T1 (46.7 %), but the difference was not significant (p = 0.28). A high frequency of genes encoding virulence factors was observed in the coagulase-negative Staphylococcus isolates. The use of moxifloxacin did not significantly modify the CNS virulence factor profiles.

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

PubMed

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.

PubMed

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.

Monitoring Seven Potentially Pathogenic Escherichia coli Serogroups in a Closed Herd of Beef Cattle from Weaning to Finishing Phases.

PubMed

Hallewell, Jennyka; Reuter, Tim; Stanford, Kim; Topp, Ed; Alexander, Trevor W

2016-12-01

The goal of this study was to monitor Shiga toxin-producing Escherichia coli (STEC) serogroups and virulence genes in cattle (n = 30) originating from a closed herd. Fecal samples were collected (1) at weaning, (2) upon arrival to a feedlot, (3) after 30 days on feed (DOF), and (4) after 135 DOF. DNA was extracted from feces for detection of virulence and serogroup genes by polymerase chain reaction (PCR) and immunomagnetic separation and pulsed-field gel electrophoresis (PFGE) were performed to collect and subtype STEC isolates. The prevalence of each serogroup measured by PCR from weaning to 135 DOF was 23.3-80.0% for O26, 33.3-46.7% for O45, 70.0-73.3% for O103, 36.7-86.7% for O111, 56.7-6.7% for O121, 26.7-66.7% for O145, and 66.7-90.0% for O157. Total fecal samples positive for virulence genes were 87.5% for ehxA, 85.8% for stx 1 , 60.0% for stx 2 , 52.5% for eae, and 44.2% for the autoagglutinating adhesion gene, saa. The prevalence of each serogroup and virulence gene tended to increase by 135 DOF, with the exception of O121, stx 2 , and saa. The frequency of detection of some virulence genes was largely affected over time, most notably with saa and stx 2 decreasing, and eae increasing when cattle were transitioned to concentrate-based diets. PFGE analysis of O157 and O103 fecal isolates revealed dominant pulsotypes, but the presence of identical O103 isolates, which differed in virulence profiles. Overall, this study showed that fecal shedding of E. coli serogroups and virulence-associated genes are highly variable over time as cattle move from ranch to feedlot. To mitigate STEC, it is important to understand the factors affecting both prevalence of individual serogroups and the presence of virulence factors.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Segelke, B; Hok, S; Lao, V

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 researchmore » 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 used to regulate virulence in Y. pestis. It is known that many bacteria use intercellular signaling molecules to orchestrate gene expression and cellular function. A fair amount is known about production and uptake of signaling molecules, but very little is known about how intercellular signaling regulates other pathways. Although several studies demonstrate that intercellular signaling plays a role in regulating virulence in other pathogens, the link between signaling and regulation of virulence has not been established. Very little work had been done directly with Y. pestis intercellular signaling apart from the work carried out at LLNL. The research we proposed was intended to both establish a causative link between AI-2 intercellular signaling and regulation of virulence in Y. pestis and elucidate the fate of the AI-2 signaling molecule after it is taken up and processed by Y. pestis. Elucidating the fate of AI-2 was expected to lead directly to the understanding of how AI-2 signal processing regulates other pathways as well as provide new insights in this direction.« less

Microgravity as a novel environmental signal affecting Salmonella enterica serovar Typhimurium virulence

NASA Technical Reports Server (NTRS)

Nickerson, C. A.; Ott, C. M.; Mister, S. J.; Morrow, B. J.; Burns-Keliher, L.; Pierson, D. L.

2000-01-01

The effects of spaceflight on the infectious disease process have only been studied at the level of the host immune response and indicate a blunting of the immune mechanism in humans and animals. Accordingly, it is necessary to assess potential changes in microbial virulence associated with spaceflight which may impact the probability of in-flight infectious disease. In this study, we investigated the effect of altered gravitational vectors on Salmonella virulence in mice. Salmonella enterica serovar Typhimurium grown under modeled microgravity (MMG) were more virulent and were recovered in higher numbers from the murine spleen and liver following oral infection compared to organisms grown under normal gravity. Furthermore, MMG-grown salmonellae were more resistant to acid stress and macrophage killing and exhibited significant differences in protein synthesis than did normal-gravity-grown cells. Our results indicate that the environment created by simulated microgravity represents a novel environmental regulatory factor of Salmonella virulence.

Diet and lifestyle as trigger factors for the onset of heartburn.

PubMed

Oliver, Katie; Davies, Gloria; Dettmar, Peter

To examine prospectively the role of reported trigger factors on symptom onset in patients with heartburn and highlight the role of these factors in the management of heartburn in the primary care setting. METHOD Twenty-two patients with heartburn and 50 controls were recruited in Bedfordshire, UK. A seven-day symptom and trigger diary was completed by patients and controls. Patients reported a collection of heartburn symptoms varying in severity and time of day. Aspects of diet and lifestyle perceived as trigger factors included large meals, time of eating and posture. Multiple trigger factors were reported for heartburn. Although symptom onset varies between individuals, consideration should be given to trigger factors in the management of heartburn symptoms.

Phospholipids Trigger Cryptococcus neoformans Capsular Enlargement during Interactions with Amoebae and Macrophages

PubMed Central

Chrisman, Cara J.; Albuquerque, Patricia; Guimaraes, Allan J.; Nieves, Edward; Casadevall, Arturo

2011-01-01

A remarkable aspect of the interaction of Cryptococcus neoformans with mammalian hosts is a consistent increase in capsule volume. Given that many aspects of the interaction of C. neoformans with macrophages are also observed with amoebae, we hypothesized that the capsule enlargement phenomenon also had a protozoan parallel. Incubation of C. neoformans with Acanthamoeba castellanii resulted in C. neoformans capsular enlargement. The phenomenon required contact between fungal and protozoan cells but did not require amoeba viability. Analysis of amoebae extracts showed that the likely stimuli for capsule enlargement were protozoan polar lipids. Extracts from macrophages and mammalian serum also triggered cryptococcal capsular enlargement. C. neoformans capsule enlargement required expression of fungal phospholipase B, but not phospholipase C. Purified phospholipids, in particular, phosphatidylcholine, and derived molecules triggered capsular enlargement with the subsequent formation of giant cells. These results implicate phospholipids as a trigger for both C. neoformans capsule enlargement in vivo and exopolysaccharide production. The observation that the incubation of C. neoformans with phospholipids led to the formation of giant cells provides the means to generate these enigmatic cells in vitro. Protozoan- or mammalian-derived polar lipids could represent a danger signal for C. neoformans that triggers capsular enlargement as a non-specific defense mechanism against potential predatory cells. Hence, phospholipids are the first host-derived molecules identified to trigger capsular enlargement. The parallels apparent in the capsular response of C. neoformans to both amoebae and macrophages provide additional support for the notion that certain aspects of cryptococcal virulence emerged as a consequence of environmental interactions with other microorganisms such as protists. PMID:21637814

Quantitative proteomics unravels that the post-transcriptional regulator Crc modulates the generation of vesicles and secreted virulence determinants of Pseudomonas aeruginosa.

PubMed

Reales-Calderón, Jose Antonio; Corona, Fernando; Monteoliva, Lucía; Gil, Concha; Martínez, Jose Luis

2015-09-01

Crc is a post-transcriptional regulator in Pseudomonas aeruginosa that modulates its metabolism, but also its susceptibility to antibiotics and virulence. Most of P. aeruginosa virulence factors are secreted or engulfed in vesicles. A Crc deficient mutant was created and the extracellular vesicles associated exoproteome and the vesicle-free secretome was quantified using iTRAQ. Fifty vesicles-associated proteins were more abundant and 14 less abundant in the Crc-defective strain, whereas 37 were more abundant and 17 less abundant in the vesicle-free secretome. Different virulence determinants, such as ToxA, protease IV, azurin, chitin-binding protein, PlcB and Hcp1, were less abundant in the Crc-defective mutant. We also observed that the crc mutant presented an impaired vesicle-associated secretion of quorum sensing signal molecules and less cytotoxicity than its wild-type strain, in agreement with the low secretion of proteins related to virulence. Our results offer new insights into the mechanisms by which Crc regulates P. aeruginosa virulence, through the modulation of vesicle formation and secretion of both virulence determinants and quorum sensing signals.

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

PubMed

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.

Virulence factors and resistance mechanisms of Serratia marcescens. A short review.

PubMed

Rodrigues, Ana P; Holanda, A R M; Lustosa, G P; Nóbrega, S M B; Santana, Willma J; Souza, Luciana B S; Coutinho, H D M

2006-03-01

Serratia marcescens, a Gram-negative bacillus that belongs to the family Enterobacteriaceae, is a human opportunistic pathogen bacterium that causes many diseases, such as urinary tract infections, respiratory tract infections, bacteremia, conjunctivitis, endocarditis, meningitis and wound infections. Many plasmides that confers multi-drug resistance were discovered, such as virulence factors, like cytotoxins that damage epithelial cells. The main topic of this paper presents a review about the molecular traits evolved in the pathogenic processes mediated by Serratia and its mechanism of resistance to drugs.

Phenotypic Characterization of a Novel Virulence-Factor Deletion Strain of Burkholderia mallei that Provides Partial Protection against Inhalational Glanders in Mice

DTIC Science & Technology

2016-02-26

minimal to mild expansion of the white pulp by lymphoid hyperplasia with variable numbers of plasma cells within the white and red pulp (Figures 8G–I... Cell . Infect. Microbiol. 6:21. doi: 10.3389/fcimb.2016.00021 Phenotypic Characterization of a Novel Virulence-Factor Deletion Strain of Burkholderia...respect to intracellular growth, macrophage uptake and phagosomal escape, actin-based motility, and multinucleated giant cell formation. Based on observed

Pravastatin inhibits farnesol production in Candida albicans and improves survival in a mouse model of systemic candidiasis.

PubMed

Tashiro, Masato; Kimura, Soichiro; Tateda, Kazuhiro; Saga, Tomoo; Ohno, Akira; Ishii, Yoshikazu; Izumikawa, Koichi; Tashiro, Takayoshi; Kohno, Shigeru; Yamaguchi, Keizo

2012-05-01

Candidemia remains a major cause of morbidity and mortality, especially in immunocompromised patients. A strategy of reducing virulence and virulence factors of Candida spp. is an attractive approach for the treatment of serious infections caused by these yeasts. Recently, farnesol has been reported to be a quorum-sensing autoinducer, as well as a virulence factor of C. albicans. In the present study, we examined the effects of pravastatin, a 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitor on the in vitro production of farnesol. In addition, the synergistic effects of pravastatin with fluconazole (FLC) were examined in a mouse model of systemic infections. In vitro experiments demonstrated that pravastatin had synergistic activity with FLC as judged by fractional inhibitory concentration index (FICI) and suppression of farnesol production at sub-minimum inhibitory concentrations. Furthermore, significant improvement of survival in systemic infection models was shown with pravastatin supplementation. The survival benefits of pravastatin were correlated with reductions of fungal burden. These data suggest the potential of pravastatin as a supportive therapy against C. albicans infections. Synergistic antifungal activity and suppression of HMG-CoA reductase-associated Candida virulence factors, including farnesol, may explain, at least in part, the in vivo efficacy of pravastatin.

Tasco®: a product of Ascophyllum nodosum enhances immune response of Caenorhabditis elegans against Pseudomonas aeruginosa infection.

PubMed

Kandasamy, Saveetha; Khan, Wajahatullah; Evans, Franklin; Critchley, Alan T; Prithiviraj, Balakrishnan

2012-01-01

The effects of Tasco®, a product made from the brown seaweed (Ascophyllum nodosum) were tested for the ability to protect Caenorhabditis elegans against Pseudomonas aeruginosa infection. A water extract of Tasco® (TWE) reduced P. aeruginosa inflicted mortality in the nematode. The TWE, at a concentration of 300 µg/mL, offered the maximum protection and induced the expression of innate immune response genes viz.; zk6.7 (Lypases), lys-1 (Lysozyme), spp-1 (Saponin like protein), f28d1.3 (Thaumatin like protein), t20g5.7 (Matridin SK domain protein), abf-1 (Antibacterial protein) and f38a1.5 (Lectin family protein). Further, TWE treatment also affected a number of virulence components of the P. aeuroginosa and reduced its secreted virulence factors such as lipase, proteases and toxic metabolites; hydrogen cyanide and pyocyanin. Decreased virulence factors were associated with a significant reduction in expression of regulatory genes involved in quorum sensing, lasI, lasR, rhlI and rhlR. In conclusion, the TWE-treatment protected the C. elegans against P. aeruginosa infection by a combination of effects on the innate immunity of the worms and direct effects on the bacterial quorum sensing and virulence factors.

Fibrinogen Is at the Interface of Host Defense and Pathogen Virulence in Staphylococcus aureus Infection

PubMed Central

Ko, Ya-Ping; Flick, Matthew J.

2017-01-01

Fibrinogen not only plays a pivotal role in hemostasis but also serves key roles in antimicrobial host defense. As a rapidly assembled provisional matrix protein, fibrin(ogen) can function as an early line of host protection by limiting bacterial growth, suppressing dissemination of microbes to distant sites, and mediating host bacterial killing. Fibrinogen-mediated host antimicrobial activity occurs predominantly through two general mechanisms, namely, fibrin matrices functioning as a protective barrier and fibrin(ogen) directly or indirectly driving host protective immune function. The potential of fibrin to limit bacterial infection and disease has been countered by numerous bacterial species evolving and maintaining virulence factors that engage hemostatic system components within vertebrate hosts. Bacterial factors have been isolated that simply bind fibrinogen or fibrin, promote fibrin polymer formation, or promote fibrin dissolution. Staphylococcus aureus is an opportunistic gram-positive bacterium, the causative agent of a wide range of human infectious diseases, and a prime example of a pathogen exquisitely sensitive to host fibrinogen. Indeed, current data suggest fibrinogen serves as a context-dependent determinant of host defense or pathogen virulence in Staphylococcus infection whose ultimate contribution is dictated by the expression of S. aureus virulence factors, the path of infection, and the tissue microenvironment. PMID:27056151

Contemporary Avian Influenza A Virus Subtype H1, H6, H7, H10, and H15 Hemagglutinin Genes Encode a Mammalian Virulence Factor Similar to the 1918 Pandemic Virus H1 Hemagglutinin

PubMed Central

Qi, Li; Pujanauski, Lindsey M.; Davis, A. Sally; Schwartzman, Louis M.; Chertow, Daniel S.; Baxter, David; Scherler, Kelsey; Hartshorn, Kevan L.; Slemons, Richard D.; Walters, Kathie-Anne; Kash, John C.

2014-01-01

ABSTRACT Zoonotic avian influenza virus infections may lead to epidemics or pandemics. The 1918 pandemic influenza virus has an avian influenza virus-like genome, and its H1 hemagglutinin was identified as a key mammalian virulence factor. A chimeric 1918 virus expressing a contemporary avian H1 hemagglutinin, however, displayed murine pathogenicity indistinguishable from that of the 1918 virus. Here, isogenic chimeric avian influenza viruses were constructed on an avian influenza virus backbone, differing only by hemagglutinin subtype expressed. Viruses expressing the avian H1, H6, H7, H10, and H15 subtypes were pathogenic in mice and cytopathic in normal human bronchial epithelial cells, in contrast to H2-, H3-, H5-, H9-, H11-, H13-, H14-, and H16-expressing viruses. Mouse pathogenicity was associated with pulmonary macrophage and neutrophil recruitment. These data suggest that avian influenza virus hemagglutinins H1, H6, H7, H10, and H15 contain inherent mammalian virulence factors and likely share a key virulence property of the 1918 virus. Consequently, zoonotic infections with avian influenza viruses bearing one of these hemagglutinins may cause enhanced disease in mammals. PMID:25406382

Tasco®: A Product of Ascophyllum nodosum Enhances Immune Response of Caenorhabditis elegans Against Pseudomonas aeruginosa Infection

PubMed Central

Kandasamy, Saveetha; Khan, Wajahatullah; Evans, Franklin; Critchley, Alan T.; Prithiviraj, Balakrishnan

2012-01-01

The effects of Tasco®, a product made from the brown seaweed (Ascophyllum nodosum) were tested for the ability to protect Caenorhabditis elegans against Pseudomonas aeruginosa infection. A water extract of Tasco® (TWE) reduced P. aeruginosa inflicted mortality in the nematode. The TWE, at a concentration of 300 µg/mL, offered the maximum protection and induced the expression of innate immune response genes viz.; zk6.7 (Lypases), lys-1 (Lysozyme), spp-1 (Saponin like protein), f28d1.3 (Thaumatin like protein), t20g5.7 (Matridin SK domain protein), abf-1 (Antibacterial protein) and f38a1.5 (Lectin family protein). Further, TWE treatment also affected a number of virulence components of the P. aeuroginosa and reduced its secreted virulence factors such as lipase, proteases and toxic metabolites; hydrogen cyanide and pyocyanin. Decreased virulence factors were associated with a significant reduction in expression of regulatory genes involved in quorum sensing, lasI, lasR, rhlI and rhlR. In conclusion, the TWE-treatment protected the C. elegans against P. aeruginosa infection by a combination of effects on the innate immunity of the worms and direct effects on the bacterial quorum sensing and virulence factors. PMID:22363222

The Trk Potassium Transporter Is Required for RsmB-Mediated Activation of Virulence in the Phytopathogen Pectobacterium wasabiae.

PubMed

Valente, Rita S; Xavier, Karina B

2016-01-15

Pectobacterium wasabiae (previously known as Erwinia carotovora) is an important plant pathogen that regulates the production of plant cell wall-degrading enzymes through an N-acyl homoserine lactone-based quorum sensing system and through the GacS/GacA two-component system (also known as ExpS/ExpA). At high cell density, activation of GacS/GacA induces the expression of RsmB, a noncoding RNA that is essential for the activation of virulence in this bacterium. A genetic screen to identify regulators of RsmB revealed that mutants defective in components of a putative Trk potassium transporter (trkH and trkA) had decreased rsmB expression. Further analysis of these mutants showed that changes in potassium concentration influenced rsmB expression and consequent tissue damage in potato tubers and that this regulation required an intact Trk system. Regulation of rsmB expression by potassium via the Trk system occurred even in the absence of the GacS/GacA system, demonstrating that these systems act independently and are both required for full activation of RsmB and for the downstream induction of virulence in potato infection assays. Overall, our results identified potassium as an essential environmental factor regulating the Rsm system, and the consequent induction of virulence, in the plant pathogen P. wasabiae. Crop losses from bacterial diseases caused by pectolytic bacteria are a major problem in agriculture. By studying the regulatory pathways involved in controlling the expression of plant cell wall-degrading enzymes in Pectobacterium wasabiae, we showed that the Trk potassium transport system plays an important role in the regulation of these pathways. The data presented further identify potassium as an important environmental factor in the regulation of virulence in this plant pathogen. We showed that a reduction in virulence can be achieved by increasing the extracellular concentration of potassium. Therefore, this work highlights how elucidation of the mechanisms involved in regulating virulence can lead to the identification of environmental factors that can influence the outcome of infection. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

The Trk Potassium Transporter Is Required for RsmB-Mediated Activation of Virulence in the Phytopathogen Pectobacterium wasabiae

PubMed Central

Valente, Rita S.

2015-01-01

ABSTRACT Pectobacterium wasabiae (previously known as Erwinia carotovora) is an important plant pathogen that regulates the production of plant cell wall-degrading enzymes through an N-acyl homoserine lactone-based quorum sensing system and through the GacS/GacA two-component system (also known as ExpS/ExpA). At high cell density, activation of GacS/GacA induces the expression of RsmB, a noncoding RNA that is essential for the activation of virulence in this bacterium. A genetic screen to identify regulators of RsmB revealed that mutants defective in components of a putative Trk potassium transporter (trkH and trkA) had decreased rsmB expression. Further analysis of these mutants showed that changes in potassium concentration influenced rsmB expression and consequent tissue damage in potato tubers and that this regulation required an intact Trk system. Regulation of rsmB expression by potassium via the Trk system occurred even in the absence of the GacS/GacA system, demonstrating that these systems act independently and are both required for full activation of RsmB and for the downstream induction of virulence in potato infection assays. Overall, our results identified potassium as an essential environmental factor regulating the Rsm system, and the consequent induction of virulence, in the plant pathogen P. wasabiae. IMPORTANCE Crop losses from bacterial diseases caused by pectolytic bacteria are a major problem in agriculture. By studying the regulatory pathways involved in controlling the expression of plant cell wall-degrading enzymes in Pectobacterium wasabiae, we showed that the Trk potassium transport system plays an important role in the regulation of these pathways. The data presented further identify potassium as an important environmental factor in the regulation of virulence in this plant pathogen. We showed that a reduction in virulence can be achieved by increasing the extracellular concentration of potassium. Therefore, this work highlights how elucidation of the mechanisms involved in regulating virulence can lead to the identification of environmental factors that can influence the outcome of infection. PMID:26483524

Antimicrobial resistance and virulence factors in Escherichia coli from swedish dairy calves

PubMed Central

2012-01-01

Background In Sweden, knowledge about the role of enteropathogenic Escherichia coli in neonatal calf diarrhea and the occurrence of antimicrobial resistance in E. coli from young calves is largely unknown. This has therapeutic concern and such knowledge is also required for prudent use of antimicrobials. Methods In a case control study Esherichia coli isolated from faecal samples from dairy calves were phenotyped by biochemical fingerprinting and analyzed for virulence genes by PCR. Antimicrobial susceptibility was tested by determination of minimum inhibitory concentration (MIC). Farm management data were collected and Fisher's exact test and univariable and multivariable logistic regression analysis were performed. Results Of 95 E. coli tested for antimicrobial susceptibility 61% were resistant to one or more substances and 28% were multi-resistant. The virulence gene F5 (K99) was not found in any isolate. In total, 21 out of 40 of the investigated virulence genes were not detected or rarely detected. The virulence genes espP, irp, and fyuA were more common in resistant E. coli than in fully susceptible isolates (P < 0.05). The virulence gene terZ was associated with calf diarrhea (P ≤ 0.01). The participating 85 herds had a median herd size of 80 lactating cows. Herds with calf diarrhea problems were larger (> 55 cows; P < 0.001), had higher calf mortality (P ≤ 0.01) and calf group feeders were more in use (P < 0.05), compared to herds without calf diarrhea problems. There was no association between calf diarrhea and diversity of enteric E. coli. Conclusions Antimicrobial resistance was common in E. coli from pre-weaned dairy calves, occurring particularly in calves from herds experiencing calf diarrhea problems. The results indicate that more factors than use of antimicrobials influence the epidemiology of resistant E. coli. Enteropathogenic E. coli seems to be an uncommon cause of neonatal calf diarrhea in Swedish dairy herds. In practice, calf diarrhea should be regarded holistically in a context of infectious agents, calf immunity, management practices etc. We therefore advice against routine antimicrobial treatment and recommend that bacteriological cultures, followed by testing for antimicrobial susceptibility and for virulence factors, are used to guide decisions on such treatment. PMID:22280887

Antimicrobial resistance and virulence factors in Escherichia coli from Swedish dairy calves.

PubMed

de Verdier, Kerstin; Nyman, Ann; Greko, Christina; Bengtsson, Björn

2012-01-26

In Sweden, knowledge about the role of enteropathogenic Escherichia coli in neonatal calf diarrhea and the occurrence of antimicrobial resistance in E. coli from young calves is largely unknown. This has therapeutic concern and such knowledge is also required for prudent use of antimicrobials. In a case control study Esherichia coli isolated from faecal samples from dairy calves were phenotyped by biochemical fingerprinting and analyzed for virulence genes by PCR. Antimicrobial susceptibility was tested by determination of minimum inhibitory concentration (MIC). Farm management data were collected and Fisher's exact test and univariable and multivariable logistic regression analysis were performed. Of 95 E. coli tested for antimicrobial susceptibility 61% were resistant to one or more substances and 28% were multi-resistant. The virulence gene F5 (K99) was not found in any isolate. In total, 21 out of 40 of the investigated virulence genes were not detected or rarely detected. The virulence genes espP, irp, and fyuA were more common in resistant E. coli than in fully susceptible isolates (P < 0.05). The virulence gene terZ was associated with calf diarrhea (P ≤ 0.01).The participating 85 herds had a median herd size of 80 lactating cows. Herds with calf diarrhea problems were larger (> 55 cows; P < 0.001), had higher calf mortality (P ≤ 0.01) and calf group feeders were more in use (P < 0.05), compared to herds without calf diarrhea problems.There was no association between calf diarrhea and diversity of enteric E. coli. Antimicrobial resistance was common in E. coli from pre-weaned dairy calves, occurring particularly in calves from herds experiencing calf diarrhea problems. The results indicate that more factors than use of antimicrobials influence the epidemiology of resistant E. coli.Enteropathogenic E. coli seems to be an uncommon cause of neonatal calf diarrhea in Swedish dairy herds. In practice, calf diarrhea should be regarded holistically in a context of infectious agents, calf immunity, management practices etc. We therefore advice against routine antimicrobial treatment and recommend that bacteriological cultures, followed by testing for antimicrobial susceptibility and for virulence factors, are used to guide decisions on such treatment.

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

PubMed

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 of the mutant is more responsible for attenuation than differences in host immunological factors. These results complement previous studies by providing data of high-granularity describing tissue-specific tropism of FMDV and by demonstrating microscopic localization of virulent and attenuated clones of the same field-strain FMDV.

Distribution of Classical and Nonclassical Virulence Genes in Enterotoxigenic Escherichia coli Isolates from Chilean Children and tRNA Gene Screening for Putative Insertion Sites for Genomic Islands▿†

PubMed Central

Del Canto, Felipe; Valenzuela, Patricio; Cantero, Lidia; Bronstein, Jonathan; Blanco, Jesús E.; Blanco, Jorge; Prado, Valeria; Levine, Myron; Nataro, James; Sommerfelt, Halvor; Vidal, Roberto

2011-01-01

Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrhea. Three adhesins (Tia, TibA, EtpA), an iron acquisition system (Irp1, Irp2, and FyuA), a GTPase (LeoA), and an autotransporter (EatA) are ETEC virulence-related proteins that, in contrast to the classical virulence factors (enterotoxins and fimbrial colonization factors) have not heretofore been targets in characterizing isolates from epidemiological studies. Here, we determined the occurrence of these nonclassical virulence genes in 103 ETEC isolates from Chilean children with diarrhea and described their association with O serogroups and classical virulence determinants. Because tia, leoA, irp2, and fyuA are harbored by pathogenicity islands inserted into the selC and asnT tRNA genes (tDNAs), we analyzed the regions flanking these loci. Ten additional tDNAs were also screened to identify hot spots for genetic insertions. Associations between the most frequent serogroups and classical colonization factor (CF)-toxin profiles included O6/LT-STh/CS1-CS3-CS21 (i.e., O6 serogroup, heat-labile [LT] and human heat-stable [STh] enterotoxins, and CFs CS1, -3 and -21), O6/LT-STh/CS2-CS3-CS21, and O104-O127/STh/CFAI-CS21. The eatA and etpA genes were detected in more than 70% of the collection, including diverse serogroups and virulence profiles. Sixteen percent of the ETEC strains were negative for classical and nonclassical adhesins, suggesting the presence of unknown determinants of adhesion. The leuX, thrW, and asnT tDNAs were disrupted in more than 65% of strains, suggesting they are hot spots for the insertion of mobile elements. Sequences similar to integrase genes were identified next to the thrW, asnT, pheV, and selC tDNAs. We propose that the eatA and etpA genes should be included in characterizations of ETEC isolates in future epidemiological studies to determine their prevalence in other geographical regions. Sequencing of tDNA-associated genetic insertions might identify new ETEC virulence determinants. PMID:21775541

A Xanthomonas uridine 5'-monophosphate transferase inhibits plant immune kinases.

PubMed

Feng, Feng; Yang, Fan; Rong, Wei; Wu, Xiaogang; Zhang, Jie; Chen, She; He, Chaozu; Zhou, Jian-Min

2012-04-15

Plant innate immunity is activated on the detection of pathogen-associated molecular patterns (PAMPs) at the cell surface, or of pathogen effector proteins inside the plant cell. Together, PAMP-triggered immunity and effector-triggered immunity constitute powerful defences against various phytopathogens. Pathogenic bacteria inject a variety of effector proteins into the host cell to assist infection or propagation. A number of effector proteins have been shown to inhibit plant immunity, but the biochemical basis remains unknown for the vast majority of these effectors. Here we show that the Xanthomonas campestris pathovar campestris type III effector AvrAC enhances virulence and inhibits plant immunity by specifically targeting Arabidopsis BIK1 and RIPK, two receptor-like cytoplasmic kinases known to mediate immune signalling. AvrAC is a uridylyl transferase that adds uridine 5'-monophosphate to and conceals conserved phosphorylation sites in the activation loop of BIK1 and RIPK, reducing their kinase activity and consequently inhibiting downstream signalling.

Behind the lines–actions of bacterial type III effector proteins in plant cells

PubMed Central

Büttner, Daniela

2016-01-01

Pathogenicity of most Gram-negative plant-pathogenic bacteria depends on the type III secretion (T3S) system, which translocates bacterial effector proteins into plant cells. Type III effectors modulate plant cellular pathways to the benefit of the pathogen and promote bacterial multiplication. One major virulence function of type III effectors is the suppression of plant innate immunity, which is triggered upon recognition of pathogen-derived molecular patterns by plant receptor proteins. Type III effectors also interfere with additional plant cellular processes including proteasome-dependent protein degradation, phytohormone signaling, the formation of the cytoskeleton, vesicle transport and gene expression. This review summarizes our current knowledge on the molecular functions of type III effector proteins with known plant target molecules. Furthermore, plant defense strategies for the detection of effector protein activities or effector-triggered alterations in plant targets are discussed. PMID:28201715

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

PubMed Central

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

2017-01-01

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 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. Results 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. Conclusion 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. PMID:28945190

Subinhibitory quinupristin/dalfopristin attenuates virulence of Staphylococcus aureus.

PubMed

Koszczol, Carmen; Bernardo, Katussevani; Krönke, Martin; Krut, Oleg

2006-09-01

The semi-synthetic streptogramin quinupristin/dalfopristin antibiotic exerts potent bactericidal activity against Staphylococcus aureus. We investigated whether, like other bactericidal antibiotics used at subinhibitory concentrations, quinupristin/dalfopristin enhances release of toxins by Gram-positive cocci. The activity of quinupristin/dalfopristin on exotoxin release by S. aureus was investigated by 2D SDS-PAGE combined with MALDI-TOF/MS analysis and by western blotting. We show that quinupristin/dalfopristin at subinhibitory concentrations reduces the release of S. aureus factors that induce tumour necrosis factor secretion in macrophages. Furthermore, quinupristin/dalfopristin but not linezolid attenuated S. aureus-mediated killing of infected host cells. When added to S. aureus cultures at different stages of bacterial growth, quinupristin/dalfopristin reduced in a dose-dependent manner the release of specific virulence factors (e.g. autolysin, protein A, alpha- and beta-haemolysins, lipases). In contrast, other presumably non-toxic exoproteins remained unchanged. The results of the present study suggest that subinhibitory quinupristin/dalfopristin inhibits virulence factor release by S. aureus, which might be especially helpful for the treatment of S. aureus infections, where both bactericidal as well as anti-toxin activity may be advantageous.

Calcium hydroxide suppresses Porphyromonas endodontalis lipopolysaccharide-induced bone destruction.

PubMed

Guo, J; Yang, D; Okamura, H; Teramachi, J; Ochiai, K; Qiu, L; Haneji, T

2014-05-01

Porphyromonas endodontalis and its main virulence factor, lipopolysaccharide (LPS), are associated with the development of periapical diseases and alveolar bone loss. Calcium hydroxide is commonly used for endodontic therapy. However, the effects of calcium hydroxide on the virulence of P. endodontalis LPS and the mechanism of P. endodontalis LPS-induced bone destruction are not clear. Calcium hydroxide rescued the P. endodontalis LPS-suppressed viability of MC3T3-E1 cells and activity of nuclear factor-κB (NF-κB) in these cells, resulting in the reduced expression of interleukin-6 and tumor necrosis factor-α. In addition, calcium hydroxide inhibited P. endodontalis LPS-induced osteoclastogenesis by decreasing the activities of NF-κB, p38, and ERK1/2 and the expression of nuclear factor of activated T-cell cytoplasmic 1 in RAW264.7 cells. Calcium hydroxide also rescued the P. endodontalis LPS-induced osteoclastogenesis and bone destruction in mouse calvaria. Taken together, our present results indicate that calcium hydroxide suppressed bone destruction by attenuating the virulence of P. endodontalis LPS on bone cells.

Antimicrobial resistance, biofilm formation and virulence reveal Actinobacillus pleuropneumoniae strains' pathogenicity complexity.

PubMed

Pereira, Monalessa Fábia; Rossi, Ciro César; Seide, Larissa Eler; Martins Filho, Sebastião; Dolinski, Cláudia de Melo; Bazzolli, Denise Mara Soares

2018-05-07

Porcine pleuropneumonia is an important cause of lowered productivity and economic loss in the pig industry worldwide, associated primarily with Actinobacillus pleuropneumoniae infection. Its colonization and persistence within the upper respiratory tract of affected pigs depends upon interactions between a number of genetically controlled virulence factors, such as pore-forming repeats-in-toxin exoproteins, biofilm formation, and antimicrobial resistance. This study investigated correlations between biofilm-forming capacity, antimicrobial resistance, and virulence of A. pleuropneumoniae obtained from clinical outbreaks of disease, using a Galleria mellonella alternative infection model. Results suggest that virulence is diverse amongst the 21 strains of A. pleuropneumoniae examined and biofilm formation correlated with genetic control of antimicrobial resistance. Copyright © 2018 Elsevier Ltd. All rights reserved.

Trichomoniasis

USGS Publications Warehouse

Cole, Rebecca A.

1999-01-01

Avian trichomoniasis is caused by a single celled protozoan, Trichomonas gallinae. Avirulent T. gallinae strains that do not cause disease and highly virulent strains are found in nature and circulate within bird populations. The factors that make a strain virulent are not known, but they are thought to be controlled genetically within the parasite. Similarly, the reasons why an avirulent or a virulent form of the parasite is found within a bird population at any period of time also remain unknown. Virulent strains of T. gallinae have caused major mortality events or epizootics in doves and pigeons in addition to less visible, chronic losses (Table 25.1). Infection typically involves the upper digestive tract of doves and pigeons but other species have also been infected (Fig. 25.1).

Contemporary avian influenza A virus subtype H1, H6, H7, H10, and H15 hemagglutinin genes encode a mammalian virulence factor similar to the 1918 pandemic virus H1 hemagglutinin.

PubMed

Qi, Li; Pujanauski, Lindsey M; Davis, A Sally; Schwartzman, Louis M; Chertow, Daniel S; Baxter, David; Scherler, Kelsey; Hartshorn, Kevan L; Slemons, Richard D; Walters, Kathie-Anne; Kash, John C; Taubenberger, Jeffery K

2014-11-18

Zoonotic avian influenza virus infections may lead to epidemics or pandemics. The 1918 pandemic influenza virus has an avian influenza virus-like genome, and its H1 hemagglutinin was identified as a key mammalian virulence factor. A chimeric 1918 virus expressing a contemporary avian H1 hemagglutinin, however, displayed murine pathogenicity indistinguishable from that of the 1918 virus. Here, isogenic chimeric avian influenza viruses were constructed on an avian influenza virus backbone, differing only by hemagglutinin subtype expressed. Viruses expressing the avian H1, H6, H7, H10, and H15 subtypes were pathogenic in mice and cytopathic in normal human bronchial epithelial cells, in contrast to H2-, H3-, H5-, H9-, H11-, H13-, H14-, and H16-expressing viruses. Mouse pathogenicity was associated with pulmonary macrophage and neutrophil recruitment. These data suggest that avian influenza virus hemagglutinins H1, H6, H7, H10, and H15 contain inherent mammalian virulence factors and likely share a key virulence property of the 1918 virus. Consequently, zoonotic infections with avian influenza viruses bearing one of these hemagglutinins may cause enhanced disease in mammals. Influenza viruses from birds can cause outbreaks in humans and may contribute to the development of pandemics. The 1918 pandemic influenza virus has an avian influenza virus-like genome, and its main surface protein, an H1 subtype hemagglutinin, was identified as a key mammalian virulence factor. In a previous study, a 1918 virus expressing an avian H1 gene was as virulent in mice as the reconstructed 1918 virus. Here, a set of avian influenza viruses was constructed, differing only by hemagglutinin subtype. Viruses with the avian H1, H6, H7, H10, and H15 subtypes caused severe disease in mice and damaged human lung cells. Consequently, infections with avian influenza viruses bearing one of these hemagglutinins may cause enhanced disease in mammals, and therefore surveillance for human infections with these subtypes may be important in controlling future outbreaks. Copyright © 2014 Qi et al.

Genetic and metabolic variability in autotrophic and heterotrophic bacteria

NASA Technical Reports Server (NTRS)

Decicco, B. T.

1972-01-01

The studies to evaluate an organism's ability to maintain normal physiological activities over a long period of time in a bioregenerative system are presented. Studies reviewed include: heat tolerant mutants of Pseudomonas fluoresceins, virulence factors of the Staphylococci, and the effect of mutations on the virulence for man in common and ubiquitous microorganisms.

Correlates of virulence in a frog-killing fungal pathogen: evidence from a California amphibian decline.

PubMed

Piovia-Scott, Jonah; Pope, Karen; Worth, S Joy; Rosenblum, Erica Bree; Poorten, Thomas; Refsnider, Jeanine; Rollins-Smith, Louise A; Reinert, Laura K; Wells, Heather L; Rejmanek, Dan; Lawler, Sharon; Foley, Janet

2015-07-01

The fungal pathogen Batrachochytrium dendrobatidis (Bd) has caused declines and extinctions in amphibians worldwide, and there is increasing evidence that some strains of this pathogen are more virulent than others. While a number of putative virulence factors have been identified, few studies link these factors to specific epizootic events. We documented a dramatic decline in juvenile frogs in a Bd-infected population of Cascades frogs (Rana cascadae) in the mountains of northern California and used a laboratory experiment to show that Bd isolated in the midst of this decline induced higher mortality than Bd isolated from a more stable population of the same species of frog. This highly virulent Bd isolate was more toxic to immune cells and attained higher density in liquid culture than comparable isolates. Genomic analyses revealed that this isolate is nested within the global panzootic lineage and exhibited unusual genomic patterns, including increased copy numbers of many chromosomal segments. This study integrates data from multiple sources to suggest specific phenotypic and genomic characteristics of the pathogen that may be linked to disease-related declines.

A genomic window into the virulence of Histophilus somni.

PubMed

Sandal, Indra; Inzana, Thomas J

2010-02-01

Histophilus somni is an obligate inhabitant of the respiratory and genital mucosal surfaces of bovines and ovines. An individual strain can be a primary pathogen, an opportunistic pathogen, or a commensal, but can also move between these classifications if introduced into an appropriate site (e.g. the lungs) under conditions that favor bacterial persistence. H. somni is one of the bacterial agents responsible for bovine respiratory disease complex and can also cause a variety of systemic diseases in cattle and sheep. Isolates from disease sites, such as the lungs, heart, and brain, express a wide array of virulence factors (including biofilm formation) designed to evade host defense mechanisms. By contrast, some isolates from the healthy genital tract often lack many of these virulence factors. The genomic sequences of two bovine isolates, one from pneumonic lung and the other from healthy prepuce, have aided in deciphering the differences in phenotype and virulence between the two strains, and reveal their striking genetic similarity to Haemophilus influenzae and other members of the Pasteurellaceae. (c) 2009 Elsevier Ltd. All rights reserved.

A rhamnose-rich O-antigen mediates adhesion, virulence, and host colonization for the xylem-limited phytopathogen Xylella fastidiosa.

PubMed

Clifford, Jennifer C; Rapicavoli, Jeannette N; Roper, M Caroline

2013-06-01

Xylella fastidiosa is a gram-negative, xylem-limited bacterium that causes a lethal disease of grapevine called Pierce's disease. Lipopolysaccharide (LPS) composes approximately 75% of the outer membrane of gram-negative bacteria and, because it is largely displayed on the cell surface, it mediates interactions between the bacterial cell and its surrounding environment. LPS is composed of a conserved lipid A-core oligosaccharide component and a variable O-antigen portion. By targeting a key O-antigen biosynthetic gene, we demonstrate the contribution of the rhamnose-rich O-antigen to surface attachment, cell-cell aggregation, and biofilm maturation: critical steps for successful infection of the host xylem tissue. Moreover, we have demonstrated that a fully formed O-antigen moiety is an important virulence factor for Pierce's disease development in grape and that depletion of the O-antigen compromises its ability to colonize the host. It has long been speculated that cell-surface polysaccharides play a role in X. fastidiosa virulence and this study confirms that LPS is a major virulence factor for this important agricultural pathogen.

Streptococcus iniae beta-hemolysin streptolysin S is a virulence factor in fish infection.

PubMed

Locke, Jeffrey B; Colvin, Kelly M; Varki, Nissi; Vicknair, Mike R; Nizet, Victor; Buchanan, John T

2007-06-07

Streptococcus iniae is a leading pathogen of intensive aquaculture operations worldwide, although understanding of virulence mechanisms of this pathogen in fish is lacking. S. iniae possesses a homolog of streptolysin S (SLS), a secreted, pore-forming cytotoxin that is a proven virulence factor in the human pathogen S. pyogenes. Here we used allelic exchange mutagenesis of the structural gene for the S. iniae SLS precursor (sagA) to examine the role of SLS in S. iniae pathogenicity using in vitro and in vivo models. The isogenic Delta sagA mutant was less cytotoxic to fish blood cells and cultured epithelial cells, but comparable to wild-type (WT) S. iniae in adherence/invasion of epithelial cell monolayers and resisting phagocytic killing by fish whole blood or macrophages. In a hybrid striped bass infection model, loss of SLS production led to marked virulence attenuation, as injection of the Delta sagA mutant at 1000x the WT lethal dose (LD80) produced only 10% mortality. The neutralization of SLS could represent a novel strategy for control of S. iniae infection in aquaculture.

Streptococcus mutans autolysin AtlA is a fibronectin-binding protein and contributes to bacterial survival in the bloodstream and virulence for infective endocarditis.

PubMed

Jung, Chiau-Jing; Zheng, Quan-Hau; Shieh, Ya-Hsiung; Lin, Chi-Shuan; Chia, Jean-San

2009-11-01

Streptococcus mutans, a commensal of the human oral cavity, can survive in the bloodstream and cause infective endocarditis (IE). However, the virulence factors associated with this manifestation of disease are not known. Here, we demonstrate that AtlA, an autolysin of S. mutans is a newly identified fibronectin (Fn) binding protein and contributes to bacterial resistance to phagocytosis and survival in the bloodstream. Interestingly, prior exposure to plasma at low concentrations was sufficient to enhance bacterial survival in the circulation. Calcium ions at physiological plasma concentrations induced maturation of AtlA from the 104-90 kDa isoform resulting in increased Fn binding and resistance to phagocytosis. An isogenic mutant strain defective in AtlA expression exhibited reduced survival and virulence when tested in a rat model of IE compared with the wild-type and complemented strains. The data presented suggest that plasma components utilized by S. mutans enhanced survival in the circulation and AtlA is a virulence factor associated with infective endocarditis.

Type I IFN triggers RIG-I/TLR3/NLRP3-dependent inflammasome activation in influenza A virus infected cells.

PubMed

Pothlichet, Julien; Meunier, Isabelle; Davis, Beckley K; Ting, Jenny P-Y; Skamene, Emil; von Messling, Veronika; Vidal, Silvia M

2013-01-01

Influenza A virus (IAV) triggers a contagious and potentially lethal respiratory disease. A protective IL-1β response is mediated by innate receptors in macrophages and lung epithelial cells. NLRP3 is crucial in macrophages; however, which sensors elicit IL-1β secretion in lung epithelial cells remains undetermined. Here, we describe for the first time the relative roles of the host innate receptors RIG-I (DDX58), TLR3, and NLRP3 in the IL-1β response to IAV in primary lung epithelial cells. To activate IL-1β secretion, these cells employ partially redundant recognition mechanisms that differ from those described in macrophages. RIG-I had the strongest effect through a MAVS/TRIM25/Riplet-dependent type I IFN signaling pathway upstream of TLR3 and NLRP3. Notably, RIG-I also activated the inflammasome through interaction with caspase 1 and ASC in primary lung epithelial cells. Thus, NS1, an influenza virulence factor that inhibits the RIG-I/type I IFN pathway, strongly modulated the IL-1β response in lung epithelial cells and in ferrets. The NS1 protein derived from a highly pathogenic strain resulted in increased interaction with RIG-I and inhibited type I IFN and IL-1β responses compared to the least pathogenic virus strains. These findings demonstrate that in IAV-infected lung epithelial cells RIG-I activates the inflammasome both directly and through a type I IFN positive feedback loop.

Heterogeneity among Isolates Reveals that Fitness in Low Oxygen Correlates with Aspergillus fumigatus Virulence.

PubMed

Kowalski, Caitlin H; Beattie, Sarah R; Fuller, Kevin K; McGurk, Elizabeth A; Tang, Yi-Wei; Hohl, Tobias M; Obar, Joshua J; Cramer, Robert A

2016-09-20

Previous work has shown that environmental and clinical isolates of Aspergillus fumigatus represent a diverse population that occupies a variety of niches, has extensive genetic diversity, and exhibits virulence heterogeneity in a number of animal models of invasive pulmonary aspergillosis (IPA). However, mechanisms explaining differences in virulence among A. fumigatus isolates remain enigmatic. Here, we report a significant difference in virulence of two common lab strains, CEA10 and AF293, in the murine triamcinolone immunosuppression model of IPA, in which we previously identified severe low oxygen microenvironments surrounding fungal lesions. Therefore, we hypothesize that the ability to thrive within these lesions of low oxygen promotes virulence of A. fumigatus in this model. To test this hypothesis, we performed in vitro fitness and in vivo virulence analyses in the triamcinolone murine model of IPA with 14 environmental and clinical isolates of A. fumigatus Among these isolates, we observed a strong correlation between fitness in low oxygen in vitro and virulence. In further support of our hypothesis, experimental evolution of AF293, a strain that exhibits reduced fitness in low oxygen and reduced virulence in the triamcinolone model of IPA, results in a strain (EVOL20) that has increased hypoxia fitness and a corresponding increase in virulence. Thus, the ability to thrive in low oxygen correlates with virulence of A. fumigatus isolates in the context of steroid-mediated murine immunosuppression. Aspergillus fumigatus occupies multiple environmental niches, likely contributing to the genotypic and phenotypic heterogeneity among isolates. Despite reports of virulence heterogeneity, pathogenesis studies often utilize a single strain for the identification and characterization of virulence and immunity factors. Here, we describe significant variation between A. fumigatus isolates in hypoxia fitness and virulence, highlighting the advantage of including multiple strains in future studies. We also illustrate that hypoxia fitness correlates strongly with increased virulence exclusively in the nonleukopenic murine triamcinolone immunosuppression model of IPA. Through an experimental evolution experiment, we observe that chronic hypoxia exposure results in increased virulence of A. fumigatus We describe here the first observation of a model-specific virulence phenotype correlative with in vitro fitness in hypoxia and pave the way for identification of hypoxia-mediated mechanisms of virulence in the fungal pathogen A. fumigatus. Copyright © 2016 Kowalski et al.

Evaluation of the Contributions of Individual Viral Genes to Newcastle Disease Virus Virulence and Pathogenesis

PubMed Central

Paldurai, Anandan; Kim, Shin-Hee; Nayak, Baibaswata; Xiao, Sa; Shive, Heather; Collins, Peter L.

2014-01-01

ABSTRACT Naturally occurring Newcastle disease virus (NDV) strains vary greatly in virulence. The presence of multibasic residues at the proteolytic cleavage site of the fusion (F) protein has been shown to be a primary determinant differentiating virulent versus avirulent strains. However, there is wide variation in virulence among virulent strains. There also are examples of incongruity between cleavage site sequence and virulence. These observations suggest that additional viral factors contribute to virulence. In this study, we evaluated the contribution of each viral gene to virulence individually and in different combinations by exchanging genes between velogenic (highly virulent) strain GB Texas (GBT) and mesogenic (moderately virulent) strain Beaudette C (BC). These two strains are phylogenetically closely related, and their F proteins contain identical cleavage site sequences, 112RRQKR↓F117. A total of 20 chimeric viruses were constructed and evaluated in vitro, in 1-day-old chicks, and in 2-week-old chickens. The results showed that both the envelope-associated and polymerase-associated proteins contribute to the difference in virulence between rBC and rGBT, with the envelope-associated proteins playing the greater role. The F protein was the major individual contributor and was sometimes augmented by the homologous M and HN proteins. The dramatic effect of F was independent of its cleavage site sequence since that was identical in the two strains. The polymerase L protein was the next major individual contributor and was sometimes augmented by the homologous N and P proteins. The leader and trailer regions did not appear to contribute to the difference in virulence between BC and GBT. IMPORTANCE This study is the first comprehensive and systematic study of NDV virulence and pathogenesis. Genetic exchanges between a mesogenic and a velogenic strain revealed that the fusion glycoprotein is the major virulence determinant regardless of the identical virulence protease cleavage site sequence present in both strains. The contribution of the large polymerase protein to NDV virulence is second only to that of the fusion glycoprotein. The identification of virulence determinants is of considerable importance, because of the potential to generate better live attenuated NDV vaccines. It may also be possible to apply these findings to other paramyxoviruses. PMID:24850737

The significance of virulence factors in Helicobacter pylori.

PubMed

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.

A unique virulence factor for proliferation and dwarfism in plants identified from a phytopathogenic bacterium

PubMed Central

Hoshi, Ayaka; Oshima, Kenro; Kakizawa, Shigeyuki; Ishii, Yoshiko; Ozeki, Johji; Hashimoto, Masayoshi; Komatsu, Ken; Kagiwada, Satoshi; Yamaji, Yasuyuki; Namba, Shigetou

2009-01-01

One of the most important themes in agricultural science is the identification of virulence factors involved in plant disease. Here, we show that a single virulence factor, tengu-su inducer (TENGU), induces witches' broom and dwarfism and is a small secreted protein of the plant-pathogenic bacterium, phytoplasma. When tengu was expressed in Nicotiana benthamiana plants, these plants showed symptoms of witches' broom and dwarfism, which are typical of phytoplasma infection. Transgenic Arabidopsis thaliana lines expressing tengu exhibited similar symptoms, confirming the effects of tengu expression on plants. Although the localization of phytoplasma was restricted to the phloem, TENGU protein was detected in apical buds by immunohistochemical analysis, suggesting that TENGU was transported from the phloem to other cells. Microarray analyses showed that auxin-responsive genes were significantly down-regulated in the tengu-transgenic plants compared with GUS-transgenic control plants. These results suggest that TENGU inhibits auxin-related pathways, thereby affecting plant development. PMID:19329488

In vivo insertion pool sequencing identifies virulence factors in a complex fungal–host interaction

PubMed Central

Uhse, Simon; Pflug, Florian G.; Stirnberg, Alexandra; Ehrlinger, Klaus; von Haeseler, Arndt

2018-01-01

Large-scale insertional mutagenesis screens can be powerful genome-wide tools if they are streamlined with efficient downstream analysis, which is a serious bottleneck in complex biological systems. A major impediment to the success of next-generation sequencing (NGS)-based screens for virulence factors is that the genetic material of pathogens is often underrepresented within the eukaryotic host, making detection extremely challenging. We therefore established insertion Pool-Sequencing (iPool-Seq) on maize infected with the biotrophic fungus U. maydis. iPool-Seq features tagmentation, unique molecular barcodes, and affinity purification of pathogen insertion mutant DNA from in vivo-infected tissues. In a proof of concept using iPool-Seq, we identified 28 virulence factors, including 23 that were previously uncharacterized, from an initial pool of 195 candidate effector mutants. Because of its sensitivity and quantitative nature, iPool-Seq can be applied to any insertional mutagenesis library and is especially suitable for genetically complex setups like pooled infections of eukaryotic hosts. PMID:29684023

Cinnamic acid attenuates quorum sensing associated virulence factors and biofilm formation in Pseudomonas aeruginosa PAO1.

PubMed

Rajkumari, Jobina; Borkotoky, Subhomoi; Murali, Ayaluru; Suchiang, Kitlangki; Mohanty, Saswat Kumar; Busi, Siddhardha

2018-04-21

Anti-quorum sensing and anti-biofilm efficacy of Cinnamic acid against Pseudomonas aeruginosa was comparatively assessed with respect to potent quorum sensing inhibitor, Baicalein. At sub-lethal concentration, Cinnamic acid effectively inhibited both the production of the QS-dependent virulence factors and biofilm formation in P. aeruginosa without affecting the viability of the bacterium. The phytocompound interfered with the initial attachment of planktonic cells to the substratum thereby causing reduction in biofilm development. In addition, the in vivo study indicated that the test compound protected Caenorhabditis elegans from the virulence factors of P. aeruginosa leading to reduced mortality. The in silico analysis revealed that Cinnamic acid can act as a competitive inhibitor for the natural ligands towards the ligand binding domain of the transcriptional activators of the quorum sensing circuit in P. aeruginosa, LasR and RhlR. The findings suggest that Cinnamic acid may serve as a novel quorum sensing based anti-infective in controlling P. aeruginosa infections.

Characterization of highly virulent multidrug resistant Vibrio cholerae isolated from a large cholera outbreak in Ghana.

PubMed

Feglo, Patrick Kwame; Sewurah, Miriam

2018-01-18

The purpose of this study was to investigate the virulent factors of Vibrio cholerae which caused an unprecedented large cholera outbreak in Ghana in 2014 and progressed into 2015, affected 28,975 people with 243 deaths. The V. cholerae isolates were identified to be the classical V. cholerae 01 biotype El Tor, serotype Ogawa, responsible for the large cholera outbreak in Ghana. These El Tor strains bear CtxAB and Tcp virulent genes, making the strains highly virulent. The strains also bear SXT transmissible element coding their resistance to antibiotics, causing high proportions of the strains to be multidrug resistant, with resistant proportions of 95, 90 and 75% to trimethoprim/sulfamethoxazole, ampicillin and ceftriaxone respectively. PFGE patterns indicated that the isolates clustered together with the same pattern and showed clusters similar to strains circulating in DR Congo, Cameroun, Ivory Coast and Togo. The strains carried virulence genes which facilitated the disease causation and spread. This is the first time these virulent genes were determined on the Ghanaian Vibrio strains.

The Streptococcus sanguinis competence regulon is not required for infective endocarditis virulence in a rabbit model.

PubMed

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.

Designed Reduction of Streptococcus pneumoniae Pathogenicity via Synthetic Changes in Virulence Factor Codon-pair Bias

PubMed Central

Coleman, J. Robert; Papamichail, Dimitris; Yano, Masahide; García-Suárez, María del Mar

2011-01-01

In this study, we used a previously described method of controlling gene expression with computer-based gene design and de novo DNA synthesis to attenuate the virulence of Streptococcus pneumoniae. We produced 2 S. pneumoniae serotype 3 (SP3) strains in which the pneumolysin gene (ply) was recoded with underrepresented codon pairs while retaining its amino acid sequence and determined their ply expression and pneumolysin production in vitro and their virulence in a mouse pulmonary infection model. Expression of ply and production of pneumolysin of the recoded SP3 strains were decreased, and the recoded SP3 strains were less virulent in mice than the wild-type SP3 strain or a Δply SP3 strain. Further studies showed that the least virulent recoded strain induced a markedly reduced inflammatory response in the lungs compared with the wild-type or Δply strain. These findings suggest that reducing pneumococcal virulence gene expression by altering codon-pair bias could hold promise for rational design of live-attenuated pneumococcal vaccines. PMID:21343143

Shiga toxin-producing Escherichia coli isolated from chicken meat in Iran: serogroups, virulence factors, and antimicrobial resistance properties.

PubMed

Momtaz, Hassan; Jamshidi, Alireza

2013-05-01

The aim of the current study was to determine the virulence factors, serogroups, and antibiotic resistance properties of Shiga toxin-producing Escherichia coli isolated from chicken meat samples. A total of 422 chicken meat samples were collected from 5 townships of Iran. Specimens were immediately transferred to the laboratory in a cooler with an ice pack. Samples were cultured, and the positive culture samples were analyzed by PCR assays. Finally, the antimicrobial susceptibility test was performed using the disk diffusion method in Mueller-Hinton agar. According to the results, out of 422 samples, 146 (34.59%) were confirmed to be E. coli positive and among E. coli-positive samples, 51 (34.93%) and 31 (21.23%) were from attaching and effacing E. coli (AEEC) and enterohemorrhagic E. coli (EHEC) subgroups, respectively. All of the EHEC-positive samples had all stx1, eaeA, and ehly virulence genes, whereas only 5 (9.80%) of AEEC subgroup had all stx1, stx2, and eaeA genes. As the data revealed, O157 was the most prevalent and O111 was the least prevalent strains in the Shiga toxin-producing E. coli (STEC) population. Among STEC strains, sulI and blaSHV had the highest and lowest incidence rate, respectively. There was a high resistance to tetracycline (76.82%), followed by chloramphenicol (73.17%) and nitrofurantoin (63.41%), but there was low resistance to cephalotine (7.31%) antibiotics in isolated strains. Results shows that the PCR technique has a high performance for detection of serogroups, virulence genes, and antibiotic resistance genes in STEC strains. This study is the first prevalence report of detection of virulence genes, serogroups, and antibiotic resistance properties of STEC strains isolated from chicken meat samples in Iran. Based on the results, chicken meat is one of the main sources of STEC strains and its virulence factors in Iran, so an accurate meat inspection would reduce disease outbreaks.

Characterization of Asymptomatic Bacteriuria Escherichia coli Isolates in Search of Alternative Strains for Efficient Bacterial Interference against Uropathogens

PubMed Central

Stork, Christoph; Kovács, Beáta; Rózsai, Barnabás; Putze, Johannes; Kiel, Matthias; Dorn, Ágnes; Kovács, Judit; Melegh, Szilvia; Leimbach, Andreas; Kovács, Tamás; Schneider, György; Kerényi, Monika; Emödy, Levente; Dobrindt, Ulrich

2018-01-01

Asymptomatic bacterial colonization of the urinary bladder (asymptomatic bacteriuria, ABU) can prevent bladder colonization by uropathogens and thus symptomatic urinary tract infection (UTI). Deliberate bladder colonization with Escherichia coli ABU isolate 83972 has been shown to outcompete uropathogens and prevent symptomatic UTI by bacterial interference. Many ABU isolates evolved from uropathogenic ancestors and, although attenuated, may still be able to express virulence-associated factors. Our aim was to screen for efficient and safe candidate strains that could be used as alternatives to E. coli 83972 for preventive and therapeutic bladder colonization. To identify ABU E. coli strains with minimal virulence potential but maximal interference efficiency, we compared nine ABU isolates from diabetic patients regarding their virulence- and fitness-associated phenotypes in vitro, their virulence in a murine model of sepsis and their genome content. We identified strains in competitive growth experiments, which successfully interfere with colonization of ABU isolate 83972 or uropathogenic E. coli strain 536. Six isolates were able to outcompete E. coli 83972 and two of them also outcompeted UPEC 536 during growth in urine. Superior competitiveness was not simply a result of better growth abilities in urine, but seems also to involve expression of antagonistic factors. Competitiveness in urine did not correlate with the prevalence of determinants coding for adhesins, iron uptake, toxins, and antagonistic factors. Three ABU strains (isolates 61, 106, and 123) with superior competitiveness relative to ABU model strain 83972 display low in vivo virulence in a murine sepsis model, and susceptibility to antibiotics. They belong to different phylogroups and differ in the presence of ExPEC virulence- and fitness-associated genes. Importantly, they all lack marked cytotoxic activity and exhibit a high LD50 value in the sepsis model. These strains represent promising candidates for a more detailed assessment of relevant fitness traits in urine and their suitability for therapeutic bladder colonization. PMID:29491858

Distribution of genes encoding virulence factors and molecular analysis of Shigella spp. isolated from patients with diarrhea in Kerman, Iran.

PubMed

Hosseini Nave, Hossein; Mansouri, Shahla; Emaneini, Mohammad; Moradi, Mohammad

2016-03-01

Shigella is one of the important causes of diarrhea worldwide. Shigella has several virulence factors contributing in colonization and invasion of epithelial cells and eventually death of host cells. The present study was performed in order to investigate the distribution of virulence factors genes in Shigella spp. isolated from patients with acute diarrhea in Kerman, Iran as well as the genetic relationship of these isolates. A total of 56 isolates including 31 S. flexneri, 18 S. sonnei and 7 S. boydii were evaluated by polymerase chain reaction (PCR) for the presence of 11 virulence genes (ipaH, ial, set1A, set1B, sen, virF, invE, sat, sigA, pic and sepA). Then, the clonal relationship of these strains was analyzed by multilocus variable-number tandem repeat analysis (MLVA) method. All isolates were positive for ipaH gene. The other genes include ial, invE and virF were found in 80.4%, 60.7% and 67.9% of the isolates, respectively. Both set1A and set1B were detected in 32.3% of S. flexneri isolates, whereas 66.1% of the isolates belonging to different serogroup carried sen gene. The sat gene was present in all S. flexneri isolates, but not in the S. sonnei and S. boydii isolates. The result showed, 30.4% of isolates were simultaneously positive and the rest of the isolates were negative for sepA and pic genes. The Shigella isolates were divided into 29 MLVA types. This study, for the first time, investigated distribution of 11 virulence genes in Shigella spp. Our results revealed heterogeneity of virulence genes in different Shigella serogroups. Furthermore, the strains belonging to the same species had little diversity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Emergence of non-albicans Candida among candidal vulvovaginitis cases and study of their potential virulence factors, from a tertiary care center, North India.

PubMed

Kumari, Varsha; Banerjee, Tuhina; Kumar, Pankaj; Pandey, Sulekha; Tilak, Ragini

2013-01-01

The purpose of this study was to determine the prevalence of various Candida species and study some of their virulence factors among thevulvovaginal candidiasis(VVC)patients. The study was conducted in a Tertiary Care University Hospital in North India. This study was carried out prospectively for a period of 1 year. High vaginal swabs (HVSs) were collected from women in childbearing age group attending the gynecology and obstetrics out-patient departments with the complaints suggestive of vulvovaginitis. Samples were plated on Sabouraud's dextrose agar slope. Candida spp. isolated was further speciated based on microscopy, biochemical tests and culture characteristics on special media. Virulence factors of these strains were determined by biofilm formation and phospholipase activity. A total of 464 HVS from 232 patients with the complaints of vulvovaginitis were included in this study. Following laboratory workup, 71 specimens were positive for genus Candida (30.6%). Further speciation showed 32.4% as Candida albicans, 45.07% Candida parapsilosis and 22.53% of Candida glabrata. Biofilm production was shown by 50 candidal strains (70.4%) and phospholipase activity was given by 41 candidal strains (57.74%). Our study suggests increasing prevalence of non-albicans Candida among the VVC cases along with their virulence factors. Therefore, we recommend that microbiological investigation upto species level should be mandatory to determine the emergence of non-albicans Candida as a major cause of VVC.

The response regulator expM is essential for the virulence of Erwinia carotovora subsp. carotovora and acts negatively on the sigma factor RpoS (sigma s).

PubMed

Andersson, R A; Palva, E T; Pirhonen, M

1999-07-01

The main virulence factors of Erwinia carotovora subsp. carotovora, the secreted, extracellular cell-wall-degrading enzymes, are controlled by several regulatory mechanisms. We have isolated transposon mutants with reduced virulence on tobacco. One of these mutants, with a mutation in a gene designated expM, was characterized in this study. This mutant produces slightly reduced amounts of extracellular enzymes in vitro and the secretion of the enzymes is also affected. The expM wild-type allele was cloned together with an upstream gene, designated expL, that has an unknown function. The expM gene was sequenced and found to encode a protein with similarity to the RssB/SprE protein of Escherichia coli and the MviA protein of Salmonella typhimurium. These proteins belong to a new type of two-component response regulators that negatively regulate the stability of the Sigma factor RpoS (sigma s) at the protein level. The results of this study suggest that ExpM has a similar function in E. carotovora subsp. carotovora. We also provide evidence that the overproduction of RpoS in the expM mutant is an important factor for the reduced virulence phenotype and that it partly causes the observed phenotype seen in vitro. However, an expM/rpoS double mutant is still affected in secretion of extracellular enzymes, suggesting that ExpM in addition to RpoS also acts on other targets.

Epidemiology and virulence of VIM-4 metallo-beta-lactamase-producing Pseudomonas aeruginosa isolated from burn patients in eastern Algeria.

PubMed

Meradji, Samah; Barguigua, Abouddihaj; Bentakouk, Mohamed Cherif; Nayme, Kaotar; Zerouali, Khalid; Mazouz, Dekhil; Chettibi, Houria; Timinouni, Mohammed

2016-06-01

In this study, we investigated the prevalence of carbapenem-resistant Pseudomonas aeruginosa (CRPA) in burn patients from eastern Algeria, CRPA virulence factors and the molecular epidemiology of CRPA. The overall prevalence of CRPA was 48.38%. Seven (46.66%) isolates were metallo-β-lactamases (MBL) producers and contained the MBL genes blaVIM-4 (n=6) and blaVIM-2 (n=1). Risk factors for CRPA infection were urinary catheter use and intubation (p=0.008). A high percentage of virulence factors (86.6% of these isolates were able to produce protease; 73.3% of isolates has DNase; and 66.6% were haemolysin positive) was observed in CRPA isolates. Among the seven MBL-producing isolates, four had the same clonal profile. The class 1 integrons, which contained the aadA7 gene cassette, were detected in six isolates. The 16SrRNA methylase gene, rmtB, was detected in one strain. All CRPA isolates were biofilm formers. A study on the kinetics of biofilm production revealed that biofilm production increased when the concentration of imipenem or ciprofloxacin and the incubation time increased. This is the first study to report the presence of VIM-4-producing P. aeruginosa from North Africa and also of the high prevalence of CRPA isolates. Based on our study of burn unit patients, the high percentage of P. aeruginosa with virulence factors and multi-drug resistance is alarming. Copyright © 2016 Elsevier Ltd and ISBI. All rights reserved.

Inhibitory effect of Thymus vulgaris and Origanum vulgare essential oils on virulence factors of phytopathogenic Pseudomonas syringae strains.

PubMed

Carezzano, M E; Sotelo, J P; Primo, E; Reinoso, E B; Paletti Rovey, M F; Demo, M S; Giordano, W F; Oliva, M de Las M

2017-07-01

Pseudomonas syringae is a phytopathogenic bacterium that causes lesions in leaves during the colonisation process. The damage is associated with production of many virulence factors, such as biofilm and phytotoxins. The essential oils of Thymus vulgaris (thyme) and Origanum vulgare (oregano) have been demonstrated to inhibit P. syringae. The aim of this study was to investigate the effects of T. vulgaris and O. vulgare essential oils on production of virulence factors of phytopathogenic P. syringae strains, including anti-biofilm and anti-toxins activities. The broth microdilution method was used for determination of MIC and biofilm inhibition assays. Coronatine, syringomycin and tabtoxin were pheno- and genotypically evaluated. Both oils showed good inhibitory activity against P. syringae, with MIC values from 1.43 to 11.5 mg·ml -1 for thyme and 5.8 to 11.6 mg·ml -1 for oregano. Biofilm formation, production of coronatine, syringomycin and tabtoxin were inhibited by thyme and oregano essential oil in most strains. The results presented here are promising, demonstrating the bactericidal activity and reduction of virulence factor production after treatment with thyme and oregano oil, providing insight into how they exert their antibacterial activity. These natural products could be considered in the future for the control of diseases caused by P. syringae. © 2017 German Botanical Society and The Royal Botanical Society of the Netherlands.

Species distribution, virulence factors, and antimicrobial resistance of Acinetobacter spp. isolates from dogs and cats: a preliminary study.

PubMed

Kimura, Yui; Harada, Kazuki; Shimizu, Takae; Sato, Tomomi; Kajino, Akari; Usui, Masaru; Tamura, Yutaka; Tsuyuki, Yuzo; Miyamoto, Tadashi; Ohki, Asami; Watarai, Masahisa

2018-05-12

We investigated the prevalence of virulence factors and antimicrobial resistance among 67 Acinetobacter spp. isolates, consisting of 21 Acinetobacter baumannii and 46 non-baumannii Acinetobacter from companion animals. The PCR analysis showed that the most prevalent virulence gene was afa/draBC (29.9%), followed by papC (22.4%) and cvaC (20.9%). Antimicrobial susceptibility testing revealed that resistance to gentamicin (14.9%) and ciprofloxacin (11.9%) was relatively prevalent. Five gentamicin- and/or ciprofloxacin-resistant A. baumannii strains were assigned to ST25, ST149, ST164, ST203, and ST1198. All ciprofloxacin-resistant isolates harbored point mutations in gyrA and/or parC. This is the first preliminary monitoring of animal-origin Acinetobacter spp. in Japan. © 2018 The Societies and John Wiley & Sons Australia, Ltd.

Strain-associated virulence factors of Streptococcus iniae in hybrid-striped bass.

PubMed

Buchanan, John T; Colvin, Kelly M; Vicknair, Mike R; Patel, Silpa K; Timmer, Anjuli M; Nizet, Victor

2008-09-18

Streptococcus iniae is a major fish pathogen producing invasive infections that result in economic losses in aquaculture. Development of in vitro models of S. iniae virulence may provide insight to the pathogenesis of infection in vivo. Three S. iniae strains (K288, 94-426, and 29178) were tested for virulence in a hybrid-striped bass (HSB) model using intraperitoneal injection. S. iniae strains K288 and 94-426 caused high levels of mortality in HSB (lethal dose 2x10(5)CFU) while strain 29178 was avirulent even upon IP challenge with 1000-fold higher inocula. In vitro assays were developed to test for the presence of characteristics previously associated with virulence in other species of pathogenic Streptococcus in animals and humans. In vitro differences relevant to virulence were not detected for beta-hemolysin activity, sensitivity to antimicrobial peptides, or adherence and invasion of epithelial cell layers. However, in whole-blood killing assays, the pathogenic strains were resistant to blood clearance, while 29178 was cleared (P<0.001) and more sensitive to complement (P<0.001). The avirulent strain 29178 was most efficiently phagocytosed and was most susceptible to intracellular killing (P<0.01) by the carp leukocyte cell line (CLC). When exposed to reactive oxygen species, strain 29178 was most susceptible. When the oxidative burst of CLC cells was inhibited, intracellular survival of 29178 was rescued fivefold, while no significant enhancement in survival of K288 or 94-426 was detected. Our results indicate that resistance to phagocytosis, oxidative killing, and associated phagocytic clearance is a significant factor in S. iniae virulence.

Probiotic Enterococcus faecalis Symbioflor® down regulates virulence genes of EHEC in vitro and decrease pathogenicity in a Caenorhabditis elegans model.

PubMed

Neuhaus, Klaus; Lamparter, Marina C; Zölch, Benjamin; Landstorfer, Richard; Simon, Svenja; Spanier, Britta; Ehrmann, Matthias A; Vogel, Rudi F

2017-03-01

Enterohemorrhagic E. coli O157:H7 (EHEC) shorten the lifespan of Caenorhabditis elegans compared to avirulent bacteria. Co-feeding EHEC with Enterococcus faecalis Symbioflor ® significantly increased the worms' lifespan. The transcriptome of EHEC grown in vitro with or without Symbioflor ® was analyzed using RNA-seq. The analysis revealed downregulation of several virulence-associated genes in the presence of Symbioflor ® , including virulence key genes (e.g., LEE, flagellum, quorum-sensing). The downregulation of the LEE genes was corroborated by lux-transposon mutants. Upregulated genes included acid response genes, due to a decrease in pH exerted by Symbioflor ® . Further genes indicate cellular stress in EHEC (e.g. prophage/mobile elements involved in excision, cell lysis, and cell division inhibition). Thus, the observed protection of C. elegans during an EHEC infection by the probiotic Symbioflor ® is suggested to be caused by triggering concomitant transcriptomic changes. To verify the biological relevance of this modulation, exemplary genes found to be influenced by Symbioflor ® were knocked out (fliD, espB, Z3136, Z3917, and L7052). The lifespan of nematodes changed when using knock-outs as food source and the effect could be complemented in trans. In summary, Symbioflor ® appears to be a protective probiotic in the nematode model.