Sewage Promotes Vibrio vulnificus Growth and Alters Gene Transcription in Vibrio vulnificus CMCP6.

Vibrio vulnificus is a naturally occurring, potentially lethal pathogen found in coastal waters, fish, and shellfish. Sewage spills in coastal waters occur when infrastructure fails due to severe storms or age, and may affect bacterial populations by altering nutrient levels. This study investigated effects of sewage on clonal and natural V. vulnificus populations in microcosms. Addition of 1% sewage to estuarine water caused the density of a pure culture of V. vulnificus CMCP6 and a natural V. vulnificus population to increase significantly, by two to three orders of magnitude, whether measured by quantitative PCR (qPCR) or culture and in batch and continuous cultures. Changes in the transcription of six virulence- and survival-associated genes in response to sewage were assessed using continuous culture. Exposure to sewage affected transcription of genes that may be associated with virulence, i.e., it modulated the oxidative stress response by altering superoxide dismutase transcription, significantly increasing sodB transcription while repressing sodA. Sewage also repressed transcription of nptA, which encodes a sodium-phosphate cotransporter. Sewage had no effect on sodC transcription or the putative virulence-associated genes hupA or wza. The effects of environmentally relevant levels of sewage on V. vulnificus populations and gene transcription suggest that sewage spills that impact warm coastal waters could lead to an increased risk of V. vulnificus infections. IMPORTANCE Vibrio vulnificus infections have profound impacts such as limb amputation and death for individuals with predisposing conditions. The warming climate is contributing to rising V. vulnificus prevalence in waters that were previously too cold to support high levels of the pathogen. Climate change is also expected to increase precipitation in many regions, which puts more pressure on wastewater infrastructure and will result in more frequent sewage spills. The finding that 1% wastewater in estuarine water leads to 100 to over 1,000-fold greater V. vulnificus concentrations suggests that human exposure to oysters and estuarine water could have greater health impacts in the future. Further, wastewater had a significant effect on gene transcription and has the potential to affect virulence during the initial environment-to-host transition.

Vibrio vulnificus PlpA facilitates necrotic host cell death induced by the pore forming MARTX toxin.

Opportunistic pathogen Vibrio vulnificus causes severe systemic infection in humans with high mortality. Although multiple exotoxins have been characterized in V. vulnificus, their interactions and potential synergistic roles in pathogen-induced host cell death have not been investigated previously. By employing a series of multiple exotoxin deletion mutants, we investigated whether specific exotoxins of the pathogen functioned together to achieve severe and rapid necrotic cell death. Human epithelial cells treated with V. vulnificus with a plpA deletion background exhibited an unusually prolonged cell blebbing, suggesting the importance of PlpA, a phospholipase A2, in rapid necrotic cell death by this pathogen. Additional deletion of the rtxA gene encoding the multifunctional autoprocessing repeats-in-toxin (MARTX) toxin did not result in necrotic cell blebs. However, if the rtxA gene was engineered to produce an effector-free MARTX toxin, the cell blebbing was observed, indicating that the pore forming activity of the MARTX toxin is sufficient, but the MARTX toxin effector domains are not necessary, for the blebbing. When a recombinant PlpA was treated on the blebbed cells, the blebs were completely disrupted. Consistent with this, MARTX toxin-pendent rapid release of cytosolic lactate dehydrogenase was significantly delayed in the plpA deletion background. Mutations in other exotoxins such as elastase, cytolysin/hemolysin, and/or extracellular metalloprotease did not affect the bleb formation or disruption. Together, these findings indicate that the pore forming MARTX toxin and the phospholipase A2, PlpA, cooperate sequentially to achieve rapid necrotic cell death by inducing cell blebbing and disrupting the blebs, respectively.

Regulator of ribonuclease activity modulates the pathogenicity of Vibrio vulnificus.

RraA, a protein regulator of RNase E activity, plays a unique role in modulating the mRNA abundance in Escherichia coli. The marine pathogenic bacterium Vibrio vulnificus also possesses homologs of RNase E (VvRNase E) and RraA (VvRraA1 and VvRraA2). However, their physiological roles have not yet been investigated. In this study, we demonstrated that VvRraA1 expression levels affect the pathogenicity of V. vulnificus. Compared to the wild-type strain, the VvrraA1-deleted strain (ΔVvrraA1) showed decreased motility, invasiveness, biofilm formation ability as well as virulence in mice; these phenotypic changes of ΔVvrraA1 were restored by the exogenous expression of VvrraA1. Transcriptomic analysis indicated that VvRraA1 expression levels affect the abundance of a large number of mRNA species. Among them, the half-lives of mRNA species encoding virulence factors (e.g., smcR and htpG) that have been previously shown to affect VvrraA1 expression-dependent phenotypes were positively correlated with VvrraA1 expression levels. These findings suggest that VvRraA1 modulates the pathogenicity of V. vulnificus by regulating the abundance of a subset of mRNA species.

The widespread presence of a family of fish virulence plasmids in Vibrio vulnificus stresses its relevance as a zoonotic pathogen linked to fish farms.

Vibrio vulnificus is a pathogen of public health concern that causes either primary septicemia after ingestion of raw shellfish or secondary septicemia after wound exposure to seawater. In consequence, shellfish and seawater are considered its main reservoirs. However, there is one aspect of its biology that is systematically overlooked: its association with fish in its natural environment. This association led in 1975 to the emergence of a zoonotic clade within phylogenetic lineage 2 following successive outbreaks of vibriosis in farmed eels. Although this clade is now worldwide distributed, no new zoonotic clades were subsequently reported. In this work, we have performed phylogenetic, genomic and functional studies to show that other zoonotic clades are in fact present in 4 of the 5 lineages of the species. Further, we associate these clades, most of them previously but incompletely described, with the acquisition of a family of fish virulence plasmids containing genes essential for resistance to the immune system of certain teleosts of interest in aquaculture. Consequently, our results provide several pieces of evidence about the importance of this species as a zoonotic agent linked to fish farms, as well as on the relevance of these artificial environments acting as drivers that accelerate the evolution of the species.

Ecological diversification reveals routes of pathogen emergence in endemic Vibrio vulnificus populations.

Pathogen emergence is a complex phenomenon that, despite its public health relevance, remains poorly understood. Vibrio vulnificus, an emergent human pathogen, can cause a deadly septicaemia with over 50% mortality rate. To date, the ecological drivers that lead to the emergence of clinical strains and the unique genetic traits that allow these clones to colonize the human host remain mostly unknown. We recently surveyed a large estuary in eastern Florida, where outbreaks of the disease frequently occur, and found endemic populations of the bacterium. We established two sampling sites and observed strong correlations between location and pathogenic potential. One site is significantly enriched with strains that belong to one phylogenomic cluster (C1) in which the majority of clinical strains belong. Interestingly, strains isolated from this site exhibit phenotypic traits associated with clinical outcomes, whereas strains from the second site belong to a cluster that rarely causes disease in humans (C2). Analyses of C1 genomes indicate unique genetic markers in the form of clinical-associated alleles with a potential role in virulence. Finally, metagenomic and physicochemical analyses of the sampling sites indicate that this marked cluster distribution and genetic traits are strongly associated with distinct biotic and abiotic factors (e.g., salinity, nutrients, or biodiversity), revealing how ecosystems generate selective pressures that facilitate the emergence of specific strains with pathogenic potential in a population. This knowledge can be applied to assess the risk of pathogen emergence from environmental sources and integrated toward the development of novel strategies for the prevention of future outbreaks.

Analysis of Gene Expression Profiles, Cytokines, and Bacterial Loads Relevant to Alcoholic Liver Disease Mice Infected With V. vulnificus.

Patients with liver disease are susceptible to infection with Vibrio vulnificus (V. vulnificus), but the specific reasons remain elusive. Through RNA-seq, we found that when mice with alcoholic liver disease (ALD) were infected with V. vulnificus by gavage, compared with the Pair group, the small intestinal genes affecting intestinal permeability were upregulated; and the number of differentially expressed genes related to immune functions (e.g., such as cell chemotaxis, leukocyte differentiation, and neutrophil degranulation) decreased in the liver, spleen, and blood. Further analysis showed that the number of white blood cells decreased in the Pair group, whereas those in the ALD mice did not change significantly. Interestingly, the blood bacterial load in the ALD mice was about 100 times higher than that of the Pair group. After the ALD mice were infected with V. vulnificus, the concentrations of T cell proliferation-promoting cytokines (IL-2, IL-23) decreased. Therefore, unlike the Pair group, ALD mice had weaker immune responses, lower T cell proliferation-promoting cytokines, and higher bacterial loads post-infection, possibly increasing their susceptibility to V. vulnificus infection. These new findings we presented here may help to advance the current understanding of the reasons why patients with liver disease are susceptible to V. vulnificus infection and provides potential targets for further investigation in the context of treatment options for V. vulnificus sepsis in liver disease patient.

Injectable Nanosponge-Loaded Pluronic F127 Hydrogel for Pore-Forming Toxin Neutralization.

PURPOSE: Pore-forming toxins (PFTs) perform important functions during bacterial infections. Among various virulence-targeting therapies, nanosponges (NSs) have excellent neutralization effects on multiple PFTs. To enhance treatment efficacy, NSs tend to be incorporated into other biomaterials, such as hydrogels. METHODS: In the present work, red blood cell (RBC) vesicles were harvested to wrap polymer nanoparticles, leading to the formation of NSs, and the optimal Pluronic F127 hydrogel concentration was determined for gelation. Then, a novel detoxification system was constructed by incorporating NSs into an optimized Pluronic F127 hydrogel (NS-pGel). Next, the system was characterized by rheological and sustained release behavior as well as micromorphology. Then, the in vitro neutralization effect of NS-pGel on various PFTs was examined by a hemolysis protocol. Finally, therapeutic and prophylactic detoxification efficiency was evaluated in a mouse subcutaneous infection model in vivo. RESULTS: A thermosensitive, injectable detoxification system was successfully constructed by loading NSs into a 30% Pluronic F127 hydrogel. Characterization results demonstrated that the NS-pGel hybrid system sustained an ideal fluidity and viscosity at lower temperatures but exhibited a quick sol-gel transition capacity near body temperature. In addition, this hybrid system had a sustained release behavior accompanied by good biocompatibility and biodegradability. Finally, the NS-pGel system showed neutralization effects similar to those of NSs both in vitro and in vivo, indicating a good preservation of NS functionality. CONCLUSION: In conclusion, we constructed a novel temperature-sensitive detoxification system with good biocompatibility and biodegradability, which may be applied to the clinical treatment of PFT-induced local lesions and infections.

Reduced virulence of the MARTX toxin increases the persistence of outbreak-associated Vibrio vulnificus in host reservoirs.

Opportunistic bacteria strategically dampen their virulence to allow them to survive and propagate in hosts. However, the molecular mechanisms underlying virulence control are not clearly understood. Here, we found that the opportunistic pathogen Vibrio vulnificus biotype 3, which caused an outbreak of severe wound and intestinal infections associated with farmed tilapia, secretes significantly less virulent multifunctional autoprocessing repeats-in-toxin (MARTX) toxin, which is the most critical virulence factor in other clinical Vibrio strains. The biotype 3 MARTX toxin contains a cysteine protease domain (CPD) evolutionarily retaining a unique autocleavage site and a distinct ß-flap region. CPD autoproteolytic activity is attenuated following its autocleavage because of the ß-flap region. This ß-flap blocks the active site, disabling further autoproteolytic processing and release of the modularly structured effector domains within the toxin. Expression of this altered CPD consequently results in attenuated release of effectors by the toxin and significantly reduces the virulence of V. vulnificus biotype 3 in cells and in mice. Bioinformatic analysis revealed that this virulence mechanism is shared in all biotype 3 strains. Thus, these data provide new insights into the mechanisms by which opportunistic bacteria persist in an environmental reservoir, prolonging the potential to cause outbreaks.

Characteristics of Vibrio vulnificus isolates from clinical and environmental sources.

Researchers have developed multiple methods to characterize clinical and environmental strains of Vibrio vulnificus. The aim of our study was to use four assays to detect virulence factors in strains from infected patients and those from surface waters/sediments/oysters of South Carolina and the Gulf of Mexico. Vibrio vulnificus strains from clinical (n = 81) and environmental (n = 171) sources were tested using three real-time PCR methods designed to detect polymorphisms in the 16S rRNA, vcg and pilF genes and a phenotypic method, the ability to ferment D-mannitol. Although none of the tests correctly categorized all isolates, the differentiation between clinical and environmental isolates was similar for the pilF, vcgC/E and 16S rRNA assays, with sensitivities of 74.1-79.2% and specificities of 77.4-82.7%. The pilF and vcgC/E assays are comparable in efficacy to the widely used 16S rRNA method, while the D-mannitol fermentation test is less discriminatory (sensitivity = 77.8%, specificity = 61.4%). Overall percent agreement for the D-mannitol fermentation method was also lower (66.7%) than overall percent agreement for the 3 molecular assays (78.0%-80.2%). This study demonstrated, using a large, diverse group of Vibrio vulnificus isolates, that three assays could be used to distinguish most clinical vs environmental isolates; however, additional assays are needed to increase accuracy.

Protective Effects of Chicken Egg Yolk Immunoglobulins (IgYs) against Vibrio vulnificus Infections.

Vibrio (V.) vulnificus infection is a rare disease whose death rates exceed 50% despite aggressive antibiotic treatment and surgical debridement. The aim of this study was to assess the ability of specific anti-V. vulnificus immunoglobulins Y (IgYs) for preventing and treating V. vulnificus infections. IgYs were produced by immunizing egg laying hens with inactivated whole cell bacteria. Peritoneal cytokines, blood's bacterial load, and survival curves were obtained from both prophylactic and therapeutic mouse models. The results showed that the specific IgYs (i) inhibited the growth of V. vulnificus in vitro, (ii) dramatically reduced the inflammatory response and blood's bacterial load, and (iii) improved the survival rate of V. vulnificus-infected mice. These results prove that anti-V. vulnificus IgYs can be markedly effective means for the prophylaxis and the therapy of V. vulnificus infections.

Vibrio vulnificus Hemolysin: Biological Activity, Regulation of vvhA Expression, and Role in Pathogenesis.

The Vibrio vulnificus (V. vulnificus) hemolysin (VVH) is a pore-forming cholesterol-dependent cytolysin (CDC). Although there has been some debate surrounding the in vivo virulence effects of the VVH, it is becoming increasingly clear that it drives different cellular outcomes and is involved in the pathogenesis of V. vulnificus. This minireview outlines recent advances in our understanding of the regulation of vvhA gene expression, the biological activity of the VVH and its role in pathogenesis. An in-depth examination of the role of the VVH in V. vulnificus pathogenesis will help reveal the potential targets for therapeutic and preventive interventions to treat fatal V. vulnificus septicemia in humans. Future directions in VVH research will also be discussed.

MARTX Toxin-Stimulated Interplay between Human Cells and Vibrio vulnificus.

To understand toxin-stimulated host-pathogen interactions, we performed dual-transcriptome sequencing experiments using human epithelial (HT-29) and differentiated THP-1 (dTHP-1) immune cells infected with the sepsis-causing pathogen Vibrio vulnificus (either the wild-type [WT] pathogen or a multifunctional-autoprocessing repeats-in-toxin [MARTX] toxin-deficient strain). Gene set enrichment analyses revealed MARTX toxin-dependent responses, including negative regulation of extracellular related kinase 1 (ERK1) and ERK2 (ERK1/2) signaling and cell cycle regulation in HT-29 and dTHP-1 cells, respectively. Further analysis of the expression of immune-related genes suggested that the MARTX toxin dampens immune responses in gut epithelial cells but accelerates inflammation and nuclear factor κB (NF-κB) signaling in immune cells. With respect to the pathogen, siderophore biosynthesis genes were significantly more highly expressed in WT V. vulnificus than in the MARTX toxin-deficient mutant upon infection of dTHP-1 cells. Consistent with these results, iron homeostasis genes that limit iron levels for invading pathogens were overexpressed in WT V. vulnificus-infected dTHP-1 cells. Taken together, these results suggest that MARTX toxin regulates host inflammatory responses during V. vulnificus infection while also countering host defense mechanisms such as iron limitation.IMPORTANCEV. vulnificus is an opportunistic human pathogen that can cause life-threatening sepsis in immunocompromised patients via seafood poisoning or wound infection. Among the toxic substances produced by this pathogen, the MARTX toxin greatly contributes to disease progression by promoting the dysfunction and death of host cells, which allows the bacteria to disseminate and colonize the host. In response to this, host cells mount a counterattack against the invaders by upregulating various defense genes. In this study, the gene expression profiles of both host cells and V. vulnificus were analyzed by RNA sequencing to gain a comprehensive understanding of host-pathogen interactions. Our results suggest that V. vulnificus uses the MARTX toxin to subvert host cell immune responses as well as to oppose host counterattacks such as iron limitation.

DIDS inhibits Vibrio vulnificus cytotoxicity by interfering with TolC-mediated RtxA1 toxin secretion.

Vibrio vulnificus (V. vulnificus) infection, frequently resulting in fatal septicemia, has become a growing health concern worldwide. The present study aimed to explore the potential agents that could protect against V. vulnificus cytotoxicity, and to analyze the possible underlying mechanisms. First, we observed that 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid disodium salt hydrate (DIDS) significantly suppressed V. vulnificus cytotoxicity to host cells by using a lactate dehydrogenase (LDH) assay. DIDS did not exhibit any effect on host cell viability, bacterial growth, microbial adhesion and swarming motility. DIDS effectively lowered V. vulnificus RtxA1 toxin-induced calcium influx into host mitochondria and RtxA1 binding to host cells. To further elucidate the underlying mechanism, the synthesis and secretion of RtxA1 toxin were investigated by Western blotting. Intriguingly, DIDS selectively inhibited the secretion of RtxA1 toxin, but did not influence its synthesis. Consequently, the outer membrane portal TolC, a key conduit for RtxA1 export coupled with tripartite efflux pumps, was examined by RT-PCR and Western blotting. We found that DIDS significantly reduced the expression of TolCV1 protein at the transcriptional level. Taken together, these results suggest that DIDS is a promising new paradigm as an antimicrobial drug that targets TolC-mediated toxin.

Dual expression of transgenic delta-5 and delta-6 desaturase in tilapia alters gut microbiota and enhances resistance to Vibrio vulnificus infection.

Omega-3 polyunsaturated fatty acids (n-3 PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), exhibit antibacterial and anti-inflammatory activities. Furthermore, diets rich in n-3 PUFAs are known to improve disease resistance and limit pathogen infection in commercial aquaculture fishes. In this study, we examined the effects of transgenic overexpression of n-3 PUFA biosynthesis genes on the physiological response to bacterial infection in tilapia. We first established tilapia strains with single or dual expression of salmon delta-5 desaturase and/or delta-6 desaturase and then challenged the fish with Vibrio vulnificus infection. Interestingly, our data suggest that n-3 PUFA-mediated alterations in gut microbiota may be important in determining disease outcome via effects on immune response of the host. Both liver- and muscle-specific single and dual expression of delta-5 desaturase and delta-6 desaturase resulted in higher n-3 PUFA content in transgenic fish fed with a LO basal diet. The enrichment of n-3 PUFAs in dual-transgenic fish is likely responsible for their improved survival rate and comparatively reduced expression of inflammation- and immune-associated genes after V. vulnificus infection. Gut microbiome analysis further revealed that dual-transgenic tilapia had high gut microbiota diversity, with low levels of inflammation-associated microbiota (i.e., Prevotellaceae). Thus, our findings indicate that dual expression of transgenic delta-5 and delta-6 desaturase in tilapia enhances disease resistance, an effect that is associated with increased levels of n-3 PUFAs and altered gut microbiota composition.

[Vibrio vulnificus, an increasing threat of sepsis in Germany?] / Vibrio vulnificus, eine zunehmende Sepsisgefahr in Deutschland?

BACKGROUND: The prevalence of Vibrio vulnificus heavily depends on the temperature and salinity of the sea water. In the course of climate change an increase in cases of fatal sepsis caused by V. vulnificus at the German Baltic Sea coast could be detected. OBJECTIVE: To generate awareness for a life-threatening infection with increasing incidence in Germany. MATERIAL AND METHODS: This article presents an overview of the current state of the literature followed by an exemplary description of cases with V vulnificus sepsis caused by contact with water in the Baltic Sea, which were treated at the Medical University in Greifswald in summer 2018. RESULTS: In the presence of risk factors, such as liver and kidney diseases, immunosuppression and male sex, there is a danger of severe sepsis if damaged skin comes into contact with contaminated sea water. A pronounced organ dysfunction can frequently be found on admission. In these cases the diagnosis must be made promptly and timely surgical cleansing and antibiotic treatment should be initiated (e.g. a combination of tetracyclines and third generation cephalosporins). CONCLUSION: Sepsis due to V. vulnificus will probably increase over the coming years. Because there is a latency in some cases between infection and onset of sepsis, physicians beyond the coastal region must also be informed about this disease.

A MARTX Toxin rtxA Gene Is Controlled by Host Environmental Signals through a CRP-Coordinated Regulatory Network in Vibrio vulnificus.

A multifunctional autoprocessing repeats-in-toxin (MARTX) toxin plays an essential role in the virulence of many pathogens, including a fulminating human pathogen Vibrio vulnificus H-NS and HlyU repress and derepress expression of the MARTX toxin gene rtxA in V. vulnificus, respectively. However, little is known about other regulatory proteins and environmental signals involved in rtxA regulation. In this study, we found that a leucine-responsive regulatory protein (Lrp) activates rtxA by binding directly and specifically to the rtxA promoter, P rtxA Phased hypersensitivity resulting from DNase I cleavage of the P rtxA regulatory region suggests that Lrp probably induces DNA bending in P rtxA Lrp activates P rtxA independently of H-NS and HlyU, and leucine inhibits Lrp binding to P rtxA and reduces the Lrp-mediated activation. Furthermore, a cyclic AMP receptor protein (CRP) represses P rtxA , and exogenous glucose relieves the CRP-mediated repression. Biochemical and mutational analyses demonstrated that CRP binds directly and specifically to the upstream region of P rtxA , which presumably alters the DNA conformation in P rtxA and thus represses rtxA Moreover, CRP represses expression of lrp and hlyU by binding directly to their upstream regions, forming coherent feed-forward loops with Lrp and HlyU. In conclusion, expression of rtxA is controlled by a regulatory network comprising CRP, Lrp, H-NS, and HlyU in response to changes in host environmental signals such as leucine and glucose. This collaborative regulation enables the elaborate expression of rtxA, thereby enhancing the fitness and pathogenesis of V. vulnificus during the course of infection.IMPORTANCE A MARTX toxin, RtxA, is an essential virulence factor of many pathogens, including Vibrio species. H-NS and HlyU repress and derepress, respectively, rtxA expression of a life-threatening pathogen, Vibrio vulnificus We found that Lrp directly activates rtxA independently of H-NS and HlyU, and leucine inhibits the Lrp-mediated activation of rtxA Furthermore, we demonstrated that CRP represses rtxA but derepresses in the presence of exogenous glucose. CRP represses rtxA not only directly by binding to upstream of rtxA but also indirectly by repressing lrp and hlyU This is the first report of a regulatory network comprising CRP, Lrp, H-NS, and HlyU, which coordinates the rtxA expression in response to environmental signals such as leucine and glucose during infection. This elaborate regulatory network will enhance the fitness of V. vulnificus and contribute to its successful infection within the host.

Chemotactic invasion in deep soft tissue by Vibrio vulnificus is essential for the progression of necrotic lesions.

Necrotizing soft tissue infections (NSTI) progress to severe necrosis and result in fatal sepsis within a short time. Vibrio vulnificus is a causative agent and can spread from the initial infection site through soft tissue finally to the systemic circulation of the host. The motility and chemotaxis of this bacterium are essential for proliferation and lethality in a murine model of the infection, but their role in pathogenicity has not been characterized. In this study, we revealed the roles of motility and chemotaxis during the process of V. vulnificus infection. We compared a nonmotile mutant and two nonchemotactic mutants with their parent strain (WT) with regard to bacterial spread using an in vivo imaging system (IVIS) and invasion by detection of bacteria from the muscle and spleen of a murine infection model. WT rapidly spread throughout the infected thigh and invaded deep muscle causing severe tissue damage. The detection rate in the systemic circulation and the lethality were high. On the other hand, the nonmotile mutant stayed at the inoculation site, and the nonchemotactic mutants spread only slowly through the soft tissue of the infected thigh. Detection in the systemic circulation, the degree of tissue damage, and the lethality of nonchemotactic mutants were significantly reduced in mice compared with WT. This study demonstrated that chemotaxis is essential for invasion from the infection site to the deep and distant tissues and the main pathogenic factor for the rapid progression leading to sepsis in V. vulnificus NSTI.

Phylogeny and life cycle of the zoonotic pathogen Vibrio vulnificus.

Vibrio vulnificus is a zoonotic pathogen able to cause diseases in humans and fish that occasionally result in sepsis and death. Most reviews about this pathogen (including those related to its ecology) are clearly biased towards its role as a human pathogen, emphasizing its relationship with oysters as its main reservoir, the role of the known virulence factors as well as the clinic and the epidemiology of the human disease. This review tries to give to the reader a wider vision of the biology of this pathogen covering aspects related to its phylogeny and evolution and filling the gaps in our understanding of the general strategies that V. vulnificus uses to survive outside and inside its two main hosts, the human and the eel, and how its response to specific environmental parameters determines its survival, its death, or the triggering of an infectious process.

Structure, Function, and Regulation of the Essential Virulence Factor Capsular Polysaccharide of Vibrio vulnificus.

Vibrio vulnificus populates coastal waters around the world, where it exists freely or becomes concentrated in filter feeding mollusks. It also causes rapid and life-threatening sepsis and wound infections in humans. Of its many virulence factors, it is the V. vulnificus capsule, composed of capsular polysaccharide (CPS), that plays a critical role in evasion of the host innate immune system by conferring antiphagocytic ability and resistance to complement-mediated killing. CPS may also provoke a portion of the host inflammatory cytokine response to this bacterium. CPS production is biochemically and genetically diverse among strains of V. vulnificus, and the carbohydrate diversity of CPS is likely affected by horizontal gene transfer events that result in new combinations of biosynthetic genes. Phase variation between virulent encapsulated opaque colonial variants and attenuated translucent colonial variants, which have little or no CPS, is a common phenotype among strains of this species. One mechanism for generating acapsular variants likely involves homologous recombination between repeat sequences flanking the wzb phosphatase gene within the Group 1 CPS biosynthetic and transport operon. A considerable number of environmental, genetic, and regulatory factors have now been identified that affect CPS gene expression and CPS production in this pathogen.

Vibiro vulnificus hemolysin associates with gangliosides.

BACKGROUND: Vibrio vulnificus hemolysin (VVH) is a pore-forming toxin secreted by Vibrio vulnificus. Cellular cholesterol was believed to be the receptor for VVH, because cholesterol could bind to VVH and preincubation with cholesterol inhibited cytotoxicity. It has been reported that specific glycans such as N-acetyl-D-galactosamine and N-acetyl-D-lactosamine bind to VVH, however, it has not been known whether these glycans could inhibit the cytotoxicity of VVH without oligomer formation. Thus, to date, binding mechanisms of VVH to cellular membrane, including specific receptors have not been elucidated. RESULTS: We show here that VVH associates with ganglioside GM1a, Fucosyl-GM1, GD1a, GT1c, and GD1b by glycan array. Among them, GM1a could pulldown VVH. Moreover, the GD1a inhibited the cytotoxicity of VVH without the formation of oligomers. CONCLUSION: This is the first report of a molecule able to inhibit the binding of VVH to target cells without oligomerization of VVH.