Clinical manifestations and molecular epidemiology of Vibrio vulnificus infections in Denmark

Practical Review of Necrotizing Fasciitis: Principles and Evidence-based Management

Necrotizing fasciitis is a severe, life-threatening soft tissue infection that presents as a surgical emergency. It is characterized by a rapid progression of inflammation leading to extensive tissue necrosis and destruction. Nonetheless, the diagnosis might be missed or delayed due to variable and nonspecific clinical presentation, contributing to high mortality rates. Therefore, early diagnosis and prompt, aggressive medical and surgical treatment are paramount. In this review, we highlight the defining characteristics, pathophysiology, diagnostic modalities, current principles of treatment, and evolving management strategies of necrotizing fasciitis.

Fast and accurate identification by MALDI-TOF of the zoonotic serovar E of Vibrio vulnificus linked to eel culture

Vibrio vulnificus is a zoonotic pathogen that can cause death by septicaemia in farmed fish (mainly eels) and humans. The zoonotic strains that have been isolated from diseased eels and humans after eel handling belong to clade E (or serovar E (SerE)), a clonal complex within the pathovar (pv.) piscis. The aim of this study was to evaluate the accuracy of MALDI-TOF mass spectrometry (MS) in the identification of SerE, using the other two main pv. piscis-serovars (SerA and SerI) from eels as controls. MALDI-TOF data were compared with known serologic and genetic data of five pv. piscis isolates or strains, and with the non pv. piscis reference strain. Based on multiple spectra analysis, we found serovar-specific peaks that were of ~3098 Da and ~ 4045 Da for SerE, of ~3085 Da and ~ 4037 Da for SerA, and of ~3085 Da and ~ 4044 Da for SerI. Therefore, our results demonstrate that MALDI-TOF can be used to identify SerE and could also help in the identification of the other serovars of the species. This means that zoonosis due to V. vulnificus could be prevented by using MALDI-TOF, as action can be taken immediately after the isolation of a possible zoonotic V. vulnificus strain.

Correlation of High Seawater Temperature with Vibrio and Shewanella Infections, Denmark, 2010-2018

During 2010-2018 in Denmark, 638 patients had Vibrio infections diagnosed and 521 patients had Shewanella infections diagnosed. Most cases occurred in years with high seawater temperatures. The substantial increase in those infections, with some causing septicemia, calls for clinical awareness and mandatory notification policies.

Vibrio vulnificus, an Underestimated Zoonotic Pathogen

V. vulnificus, continues being an underestimated yet lethal zoonotic pathogen. In this chapter, we provide a comprehensive review of numerous aspects of the biology, epidemiology, and virulence mechanisms of this poorly understood pathogen. We will emphasize the widespread role of horizontal gene transfer in V. vulnificus specifically virulence plasmids and draw parallels from aquaculture farms to human health. By placing current findings in the context of climate change, we will also contend that fish farms act as evolutionary drivers that accelerate species evolution and the emergence of new virulent groups. Overall, we suggest that on-farm control measures should be adopted both to protect animals from Vibriosis, and also as a public health measure to prevent the emergence of new zoonotic groups.

A multiplex PCR for the detection of Vibrio vulnificus hazardous to human and/or animal health from seafood

Vibrio vulnificus is a zoonotic pathogen linked to aquaculture that is spreading due to climate change. The pathogen can be transmitted to humans and animals by ingestion of raw shellfish or seafood feed, respectively. The aim of this work was to design and test a new procedure to detect V. vulnificus hazardous to human and/or animal health in food/feed samples. For this purpose, we combined a pre-enrichment step with multiplex PCR using primers for the species and for human and animal virulence markers. In vitro assays with mixed DNA from different Vibrio species and Vibrio cultures showed that the new protocol was 100 % specific with a detection limit of 10 cfu/mL. The protocol was successfully validated in seafood using artificially contaminated live shrimp and proved useful also in pathogen isolation from animals and their ecosystem. In conclusion, this novel protocol could be applied in health risk studies associated with food/feed consumption, as well as in the routine identification and subtyping of V. vulnificus from environmental or clinical samples.

Epidemiological and microbiological investigation of a large increase in vibriosis, northern Europe, 2018

BackgroundVibriosis cases in Northern European countries and countries bordering the Baltic Sea increased during heatwaves in 2014 and 2018.AimWe describe the epidemiology of vibriosis and the genetic diversity of Vibrio spp. isolates from Norway, Sweden, Denmark, Finland, Poland and Estonia in 2018, a year with an exceptionally warm summer.MethodsIn a retrospective study, we analysed demographics, geographical distribution, seasonality, causative species and severity of non-travel-related vibriosis cases in 2018. Data sources included surveillance systems, national laboratory notification databases and/or nationwide surveys to public health microbiology laboratories. Moreover, we performed whole genome sequencing and multilocus sequence typing of available isolates from 2014 to 2018 to map their genetic diversity.ResultsIn 2018, we identified 445 non-travel-related vibriosis cases in the study countries, considerably more than the median of 126 cases between 2014 and 2017 (range: 87-272). The main reported mode of transmission was exposure to seawater. We observed a species-specific geographical disparity of vibriosis cases across the Nordic-Baltic region. Severe vibriosis was associated with infections caused by Vibrio vulnificus (adjOR: 17.2; 95% CI: 3.3-90.5) or Vibrio parahaemolyticus (adjOR: 2.1; 95% CI: 1.0-4.5), age ≥ 65 years (65-79 years: adjOR: 3.9; 95% CI: 1.7-8.7; ≥ 80 years: adjOR: 15.5; 95% CI: 4.4-54.3) or acquiring infections during summer (adjOR: 5.1; 95% CI: 2.4-10.9). Although phylogenetic analysis revealed diversity between Vibrio spp. isolates, two V. vulnificus clusters were identified.ConclusionShared sentinel surveillance for vibriosis during summer may be valuable to monitor this emerging public health issue.

The increased prevalence of Vibrio species and the first reporting of Vibrio jasicida and Vibrio rotiferianus at UK shellfish sites

Warming sea-surface temperature has led to an increase in the prevalence of Vibrio species in marine environments. This can be observed particularly in temperate regions where conditions for their growth has become more favourable. The increased prevalence of pathogenic Vibrio species has resulted in a worldwide surge of Vibriosis infections in human and aquatic animals. This study uses sea-surface temperature data around the English and Welsh coastlines to identify locations where conditions for the presence and growth of Vibrio species is favourable. Shellfish samples collected from three locations that were experiencing an increase in sea-surface temperature were found to be positive for the presence of Vibrio species. We identified important aquaculture pathogens Vibrio rotiferianus and Vibrio jasicida from these sites that have not been reported in UK waters. We also isolated human pathogenic Vibrio species including V. parahaemolyticus from these sites. This paper reports the first isolation of V. rotiferianus and V. jasicida from UK shellfish and highlights a growing diversity of Vibrio species inhabiting British waters.

Analysis of Community Composition of Bacterioplankton in Changle Seawater in China by Illumina Sequencing Combined with Bacteria Culture

OBJECTIVES

To characterize the abundance and relative composition of seawater bacterioplankton communities in Changle city using Illumina MiSeq sequencing and bacterial culture techniques.

METHODS

Seawater samples and physicochemical factors were collected from the coastal zone of Changle city on 8 September 2019. Nineteen filter membranes were obtained after using a suction filtration system. We randomly selected eight samples for total seawater bacteria (SWDNA group) sequencing and three samples for active seawater bacteria (SWRNA group) sequencing by Illumina MiSeq. The remaining eight samples were used for bacterial culture and identification. Alpha diversity including species coverage (Coverage), species diversity (Shannon-Wiener and Simpson index), richness estimators (Chao1), and abundance-based richness estimation (ACE) were calculated to assess biodiversity of seawater bacterioplankton. Beta diversity was used to evaluate the differences between samples. The species abundance differences were determined using the Wilcoxon rank-sum test. Statistical analyses were performed in R environment.

RESULTS

The Alpha diversity in the SWDNA group in each index was ACE 3206.99, Chao1 2615.12, Shannon 4.64, Simpson 0.05, and coverage 0.97; the corresponding index was ACE 1199.55, Chao1 934.75, Shannon 3.49, Simpson 0.09, and coverage 0.99. The sequencing results of seawater bacterial genes in the coastal waters of Changle city showed that the phyla of high-abundance bacteria of both the SWDNA and SWRNA groups included Cyanobacteria, Proteobacteria, and Bacteroidetes. The main classes included Oxyphotobacteria, Alphaproteobacteria, and Gammaproteobacteria. The main genera included Synechococcus CC9902, Chloroplast, and Cyanobium_PCC-6307. Beta diversity analysis showed a significant difference between the SWDNA and SWRNA groups (P < 0.05). The species abundance differences between SWDNA and SWRNA groups after Wilcoxon rank-sum test showed that, at the phylum level, Actinomycetes was more abundant in SWDNA group (9.17 vs 1.02%, P < 0.05); at the class level, Actinomycetes (δ- Proteus) was more abundant in SWDNA group (9.47% vs 1.01%, P < 0.05); and at the genus level, Chloroplast was more abundant in SWRNA group (13.07% vs 44.57%, P < 0.05). Nine species and 53 colonies were found by bacterial culture: 20 strains of Vibrio (37.74%), 22 strains of Enterobacter (41.51%), and 11 strains of non-fermentative bacteria (20.75%).

CONCLUSION

Illumi MiSeq sequencing of seawater bacteria revealed that the total bacterial community groups and the active bacterial community groups mainly comprised Cyanobacteria, Proteobacteria, and Bacteroides at the phylum level; Oxyphotobacteria, α-Proteobacteria, and γ-Proteobacteria at the class level; with Synechococcus_CC9902, Chloroplast, and Cyanobium_PCC-6307 comprising the predominant genera. Exploring the composition and differences of seawater bacteria assists understanding regarding the biodiversity and the infections related to seawater bacteria along the coast of the Changle, provides information that will aid in the diagnosis and treatment of such infections.

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.

Heatwave-associated Vibrio infections in Germany, 2018 and 2019

Background

Vibrio spp. are aquatic bacteria that prefer warm seawater with moderate salinity. In humans, they can cause gastroenteritis, wound infections, and ear infections. During the summers of 2018 and 2019, unprecedented high sea surface temperatures were recorded in the German Baltic Sea.

Aim

We aimed to describe the clinical course and microbiological characteristics of Vibrio infections in Germany in 2018 and 2019.

Methods

We performed an observational retrospective multi-centre cohort study of patients diagnosed with domestically-acquired Vibrio infections in Germany in 2018 and 2019. Demographic, clinical, and microbiological data were assessed, and isolates were subjected to whole genome sequencing and antimicrobial susceptibility testing.

Results

Of the 63 patients with Vibrio infections, most contracted the virus between June and September, primarily in the Baltic Sea: 44 (70%) were male and the median age was 65 years (range: 2–93 years). Thirty-eight patients presented with wound infections, 16 with ear infections, six with gastroenteritis, two with pneumonia (after seawater aspiration) and one with primary septicaemia. The majority of infections were attributed to V. cholerae (non–O1/non-O139) (n = 30; 48%) or V. vulnificus (n = 22; 38%). Phylogenetic analyses of 12 available isolates showed clusters of three identical strains of V. vulnificus, which caused wound infections, suggesting that some clonal lines can spread across the Baltic Sea.

Conclusions

During the summers of 2018 and 2019, severe heatwaves facilitated increased numbers of Vibrio infections in Germany. Since climate change is likely to favour the proliferation of these bacteria, a further increase in Vibrio-associated diseases is expected.

Sensitively and quickly detecting Vibrio vulnificus by real time recombinase polymerase amplification targeted to vvhA gene

Vibrio vulnificus (V. vulnificus) is a Gram-negative bacterium living in warm and salty water. This marine bacterium could produce hemolysin (VVH), which often causes serious gastroenteritis or septicemia when people contact to seawater or seafood containing V. vulnificus. Timely diagnosis is regard as essential to disease surveillance. In this paper, we aimed at developing a quick and sensitive method for the detection of Vibrio vulnificus using real time recombinase polymerase amplification (real time RPA). Specific primers and an exo probe were designed on the basis of the vvhA gene sequence available in GenBank. Target DNA could be amplified and labeled with specific fluorophore within 20 min at 38 °C. The method exhibited a high specificity, only detecting Vibrio vulnificus and not showing cross-reaction with other bacteria. The sensitivity of this method was 2 pg per reaction (20 μL) for DNA, or 200 copies per reaction (20 μL) for standard plasmid. The detection limit (LOD) stated as the target level that would be detected 95% of the time and estimated was 1.58 × 10² copies by fit of the probit to the results of 8 replicates in different concentration. For quantitative analysis of the real time RPA, the second order polynomial regression was adopted in our study. The results showed the correlation coefficients were raised above 0.98, which suggested this model might be a better choice for the quantitative analysis of real time RPA compared to the routine linear regression model. For artificially contaminated plasma samples, Vibrio vulnificus could be detected within 16 min by real time RPA at concentration as low as 1.2 × 10² CFU/mL or 2.4 CFU per reaction (20 μL). Thus, the real time RPA method established in this study shows great potential for detecting Vibrio vulnificus in the research laboratory and disease diagnosis.

Method for Specific Identification of the Emerging Zoonotic Pathogen Vibrio vulnificus Lineage 3 (Formerly Biotype 3)

Vibrio vulnificus is a zoonotic pathogen that is spreading worldwide due to global warming. Lineage 3 (L3; formerly biotype 3) includes the strains of the species with the unique ability to cause fish farm-linked outbreaks of septicemia. The L3 strains emerged recently and are particularly virulent and difficult to identify. Here, we describe a newly developed PCR method based on a comparative genomic study useful for both rapid identification and epidemiological studies of this interesting emerging group. The comparative genomic analysis also revealed the presence of a genetic duplication in the L3 strains that could be related to the unique ability of this lineage to produce septicemia outbreaks.

A Real-Time Recombinase Polymerase Amplification Method for Rapid Detection of Vibrio vulnificus in Seafood

As an important foodborne pathogen, Vibrio vulnificus gives a significant threat to food safety and public health. Rapid and accurate detection methods for V. vulnificus are required to control its spread. The conventional detection methods are time-consuming and labor-intensive, while the polymerase chain reaction (PCR)- and quantitative PCR (qPCR)-based methods are limited because of their dependence on laboratory equipment. Nucleic acid isothermal amplification technologies have been applied to develop simpler assays. In this study, a rapid detection method based on real-time recombinase polymerase amplification (RPA) targeting the extracellular metalloprotease (empV) gene of V. vulnificus has been established. The method finished the detection in 2–14 min at 39°C with good specificity. The limit of detection was 17 gene copies or 1 colony-forming unit (CFU) per reaction, or 1 CFU/10 g of spiked food with enrichment. In a clinical sample detection test, the results of real-time RPA were 100% consistent with bioassay and qPCR. Moreover, the method could resist the effect of food matrix and could tolerate crude templates. The real-time RPA method established in this study is rapid and simple and has the potential to be widely applied for V. vulnificus detection in food safety control.

An isothermal recombinase polymerase amplification and lateral flow strip combined method for rapid on-site detection of Vibrio vulnificus in raw seafood

Vibrio vulnificus is an important foodborne pathogenic bacterium that mainly contaminates seafood. Rapid and accurate technologies that suitable for on-site detection are critical for effective control of its spreading. Conventional detection methods and polymerase chain reaction (PCR)-based and qPCR-based approaches have application limitations in on-site scenarios. Application of loop-mediated isothermal amplification (LAMP) technology was a good step towards the on-site detection. In this study, a recombinase polymerase amplification (RPA)-based detection method for V. vulnificus was developed combining with lateral flow strip (LFS) for visualized signal. The method targeted the conservative empV gene encoding the extracellular metalloproteinase, and finished detection in 35 min at a conveniently low temperature of 37 °C. It showed good specificity and an excellent sensitivity of 2 copies of the genome or 10^-1 colony forming unit (CFU) per reaction, or 1 CFU/10 g in spiked food samples with enrichment. The method tolerated unpurified templates directly from sample boiling, which added the convenience of the overall procedure. Application of the RPA-LFS method for clinical samples showed accurate and consistent detection results compared to bioassay and quantitative PCR. This RPA-LFS combined method is well suited for on-site detection of V. vulnificus.

Phylogeography of the marine pathogen, Vibrio vulnificus, revealed the ancestral scenarios of its evolution

Vibrio vulnificus is the leading cause of seafood‐associated deaths worldwide. Despite the growing knowledge about the population structure of V. vulnificus, the evolutionary history and the ancestral relationships of strains isolated from various regions around the world have not been determined. Using the largest collection of sequence and isolate data of V. vulnificus to date, we applied ancestral character reconstruction to study the phylogeography of V. vulnificus. Multilocus sequence typing data from 10 housekeeping genes were used for the inference of ancestral states and reconstruction of the evolutionary history. The findings showed that the common ancestor of all V. vulnificus populations originated from East Asia, and later evolved into two main clusters that spread with time and eventually evolved into distinct populations in different parts of the world. While we found no meaningful insights concerning the evolution of V. vulnificus populations in the Middle East; however, we were able to reconstruct the ancestral scenarios of its evolution in East Asia, North America, and Western Europe.

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.

First findings of potentially human pathogenic bacteria Vibrio in the south-eastern Baltic Sea coastal and transitional bathing waters

Vibrio spp. are bacteria that inhabit fresh and marine waters throughout the world and can cause severe infections in humans. This study aimed to investigate the presence of potentially pathogenic Vibrio bacteria in the coastal waters of the Lithuanian Baltic Sea and the Curonian Lagoon. The results of cultivation on TCBS media showed that total abundance of Vibrio spp. varied from 1.2 × 10² to 6 × 10⁴ CFU L^-1. Real-time PCR revealed that the V. vulnificus vvhA gene varied from 2.8 × 10³ to 3.7 × 10⁴ copies L^-1, with the highest amounts in sites with average water salinity of 7.1 PSU. Both green and blue-green algae and lower salinity play a role in the growth and spread of total Vibrio spp. Although potential infection risk was low at the time of this study, regular monitoring of Vibrio spp. and infection risk assessments are recommended.

Application of gyrB targeted SYBR green based qPCR assay for the specific and rapid detection of Vibrio vulnificus in seafood

A SYBR green based qPCR assay targeting a unique region of gyrB was developed for the detection of Vibrio vulnificus. The specificity of the assay was studied using V. vulnificus and other bacterial strains belonging to Vibrio and non-Vibrio species. The assay unambiguously distinguished V.vulnificus with a sensitivity of 10¹ CFU/mL in pure culture while 10²CFU/g was detected in clam meat homogenate with an efficiency of ≥98%.The utility of the qPCR assay was validated with naturally incurred seafood samples, where 24 out of 59(40.67%) seafood samples tested positive for V. vulnificus after 6-8 h enrichment in APW-P broth. In contrast, conventional PCR could detect only 11 samples (18.64%). Our results showed that qPCR assay developed in this study could be used as a rapid method for screening seafood samples for the presence of V. vulnificus, as the assay can be completed within 9-12 h including the enrichment of seafood in APW-P broth. The gyrB targeted qPCR developed in this study can provide excellent results on the presence and load of V. vulnificus in naturally contaminated samples quickly and efficiently; thus it could find application as a routine test in the seafood industry for the analysis V. vulnificus.

Unexplored Opportunities: Use of Climate- and Weather-Driven Early Warning Systems to Reduce the Burden of Infectious Diseases

PURPOSE OF REVIEW

Weather and climate influence multiple aspects of infectious disease ecology. Creating and applying early warning systems based on temperature, precipitation, and other environmental data can identify where and when outbreaks of climate-sensitive infectious diseases could occur and can be used by decision makers to allocate resources. Whether an outbreak actually occurs depends heavily on other social, political, and institutional factors.

RECENT FINDINGS

Improving the timing and confidence of seasonal climate forecasting, coupled with knowledge of exposure-response relationships, can identify prior conditions conducive to disease outbreaks weeks to months in advance of outbreaks. This information could then be used by public health professionals to improve surveillance in the most likely areas for threats. Early warning systems are well established for drought and famine. And while weather- and climate-driven early warning systems for certain diseases, such as dengue fever and cholera, are employed in some regions, this area of research is underdeveloped. Early warning systems based on temperature, precipitation, and other environmental data provide an opportunity for early detection leading to early action and response to potential pathogen threats, thereby reducing the burden of disease when compared with passive health indicator-based surveillance systems.

Environmental Suitability of Vibrio Infections in a Warming Climate: An Early Warning System

BACKGROUND

Some Vibrio spp. are pathogenic and ubiquitous in marine waters with low to moderate salinity and thrive with elevated sea surface temperature (SST).

OBJECTIVES

Our objective was to monitor and project the suitability of marine conditions for Vibrio infections under climate change scenarios.

METHODS

The European Centre for Disease Prevention and Control (ECDC) developed a platform (the ECDC Vibrio Map Viewer) to monitor the environmental suitability of coastal waters for Vibrio spp. using remotely sensed SST and salinity. A case-crossover study of Swedish cases was conducted to ascertain the relationship between SST and Vibrio infection through a conditional logistic regression. Climate change projections for Vibrio infections were developed for Representative Concentration Pathway (RCP) 4.5 and RCP 8.5.

RESULTS

The ECDC Vibrio Map Viewer detected environmentally suitable areas for Vibrio spp. in the Baltic Sea in July 2014 that were accompanied by a spike in cases and one death in Sweden. The estimated exposure-response relationship for Vibrio infections at a threshold of 16°C revealed a relative risk (RR)=1.14 (95% CI: 1.02, 1.27; p=0.024) for a lag of 2 wk; the estimated risk increased successively beyond this SST threshold. Climate change projections for SST under the RCP 4.5 and RCP 8.5 scenarios indicate a marked upward trend during the summer months and an increase in the relative risk of these infections in the coming decades.

CONCLUSIONS

This platform can serve as an early warning system as the risk of further Vibrio infections increases in the 21st century due to climate change. https://doi.org/10.1289/EHP2198.

Lrp, a global regulator, regulates the virulence of Vibrio vulnificus

Background

An attenuated mutant (designated NY303) of Vibrio vulnificus, which causes serious wound infection and septicemia in humans, was isolated fortuitously from a clinical strain YJ016. This mutant was defective in cytotoxicity, migration on soft agar and virulence in the mouse. The purpose of this study was to map the mutation in this attenuated mutant and further explore how the gene thus identified is involved in virulence.

Methods

The whole genome sequence of mutant NY303 determined by next-generation sequencing was compared with that of strain YJ016 to map the mutations. By isolating and characterizing the specific gene-knockout mutants, the gene associated with the phenotype of mutant NY303 was identified. This gene encodes a global regulator, Lrp. A mutant, YH01, deficient in Lrp was isolated and examined in vitro, in vivo and ex vivo to find the affected virulence mechanisms. The target genes of Lrp were further identified by comparing the transcriptomes, which were determined by RNA-seq, of strain YJ016 and mutant YH01. The promoters bound by Lrp were identified by genome footprinting-sequencing, and those related with virulence were further examined by electrophoretic mobility shift assay.

Results

A mutation in lrp was shown to be associated with the reduced cytotoxicity, chemotaxis and virulence of mutant NY303. Mutant YH01 exhibited a phenotype resembling that of mutant NY303, and was defective in colonization in the mouse and growth in mouse serum, but not the antiphagocytosis ability. 596 and 95 genes were down- and up-regulated, respectively, in mutant YH01. Many of the genes involved in secretion of the MARTX cytotoxin, chemotaxis and iron-acquisition were down-regulated in mutant YH01. The lrp gene, which was shown to be negatively autoregulated, and 7 down-regulated virulence-associated genes were bound by Lrp in their promoters. A 14-bp consensus sequence, mkCrTTkwAyTsTG, putatively recognized by Lrp was identified in the promoters of these genes.

Conclusions

Lrp is a global regulator involved in regulation of cytotoxicity, chemotaxis and iron-acquisition in V. vulnificus. Down-regulation of many of the genes associated with these properties may be responsible, at least partly, for loss of virulence in mutant NY303.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-017-0361-9) contains supplementary material, which is available to authorized users.

Vibrio vulnificus: An Environmental and Clinical Burden

Vibrio vulnificus is a Gram negative, rod shaped bacterium that belongs to the family Vibrionaceae. It is a deadly, opportunistic human pathogen which is responsible for the majority of seafood-associated deaths worldwide. V. vulnificus infection can be fatal as it may cause severe wound infections potentially requiring amputation or lead to sepsis in susceptible individuals. Treatment is increasingly challenging as V. vulnificus has begun to develop resistance against certain antibiotics due to their indiscriminate use. This article aims to provide insight into the antibiotic resistance of V. vulnificus in different parts of the world as well as an overall review of its clinical manifestations, treatment, and prevention. Understanding the organism's antibiotic resistance profile is vital in order to select appropriate treatment and initiate appropriate prevention measures to treat and control V. vulnificus infections, which should eventually help lower the mortality rate associated with this pathogen worldwide.

Distribution of Fatal Vibrio Vulnificus Necrotizing Skin and Soft-Tissue Infections: A Systematic Review and Meta-Analysis

Vibrio vulnificus necrotizing skin and soft tissue infections (VNSSTIs), which have increased significantly over the past few decades, are still highly lethal and disabling diseases despite advancing antibiotic and infection control practices. We, therefore, examined the spatiotemporal distribution of worldwide reported episodes and associated mortality rates of VNSSTIs between 1966 and 2014. The PubMed and Cochrane Library databases were systematically searched for observational studies on patients with VNSSTIs. The primary outcome was all-cause mortality. We did random-effects meta-analysis to obtain estimates for primary outcomes; the estimates are presented as means plus a 95% confidence interval (CI). Data from the selected studies were also extracted and pooled for correlation analyses.Nineteen studies of 2227 total patients with VNSSTIs were analyzed. More than 95% of the episodes occurred in the subtropical western Pacific and Atlantic coastal regions of the northern hemisphere. While the number of cases and the number of deaths were not correlated with the study period (rs = 0.476 and 0.310, P = 0.233 and 0.456, respectively), the 5-year mortality rate was significantly negatively correlated with them (rs = -0.905, P = 0.002). Even so, the pooled estimate of total mortality rates from the random-effects meta-analysis was as high as 37.2% (95% CI: 0.265-0.479).These data suggest that VNSSTIs are always an important public health problem and will become more critical and urgent because of global warming. Knowing the current distribution of VNSSTIs will help focus education, policy measures, early clinical diagnosis, and appropriate medical and surgical treatment for them.

Septic arthritis and subsequent fatal septic shock caused by Vibrio vulnificus infection

Vibrio vulnificus is a rare but potential fatal bacterium that can cause severe infections. Wound infections, primary sepsis and gastroenteritis are the most common clinical features. Septic arthritis caused by V. vulnificus is an atypical presentation that has been reported in only two case reports; however, it has not been previously noted in Denmark. The authors report a case of septic arthritis caused by V. vulnificus in an immunocompromised patient. The disease progressed to severe sepsis and subsequent death within 10 h of admission.

The emergence of Vibrio pathogens in Europe: ecology, evolution, and pathogenesis (Paris, 11-12th March 2015)

Global change has caused a worldwide increase in reports of Vibrio-associated diseases with ecosystem-wide impacts on humans and marine animals. In Europe, higher prevalence of human infections followed regional climatic trends with outbreaks occurring during episodes of unusually warm weather. Similar patterns were also observed in Vibrio-associated diseases affecting marine organisms such as fish, bivalves and corals. Basic knowledge is still lacking on the ecology and evolutionary biology of these bacteria as well as on their virulence mechanisms. Current limitations in experimental systems to study infection and the lack of diagnostic tools still prevent a better understanding of Vibrio emergence. A major challenge is to foster cooperation between fundamental and applied research in order to investigate the consequences of pathogen emergence in natural Vibrio populations and answer federative questions that meet societal needs. Here we report the proceedings of the first European workshop dedicated to these specific goals of the Vibrio research community by connecting current knowledge to societal issues related to ocean health and food security.

Evaluation of Ice Slurries as a Control for Postharvest Growth of Vibrio spp. in Oysters and Potential for Filth Contamination

Raw oyster consumption is the most common route of exposure for Vibrio spp. infections in humans. Vibriosis has been increasing steadily in the United States despite efforts to reduce the incidence of the disease. Research has demonstrated that ice is effective in reducing postharvest Vibrio spp. growth in oysters but has raised concerns of possible contamination of oyster meat by filth (as indicated by the presence of fecal coliform bacteria or Clostridium perfringens). This study examined the use of ice slurries (<4.5°C) to reduce Vibrio growth. Ice slurries showed rapid internal cooling of oysters, from 23.9°C (75°F) to 10°C (50°F) within 12 min. The initial bacterial loads in the ice slurry waters were near the limits of detection. Following repeated dipping of oysters into ice slurries, water samples exhibited significant (P < 0.05) increases in median levels of fecal coliforms (9.5 most probable number [MPN]/100 ml), C. perfringens (280 MPN/100 ml), Vibrio vulnificus (11,250 MPN/ml), and total Vibrio parahaemolyticus (3,900 MPN/ml). The microbial load in oyster meat, however, was unchanged after 15 min of submergence, with no significant differences (P < 0.05) in levels of filth indicator (range, 250 to 720 MPN/100 g) or Vibrio spp. (range, 9,000 to 20,000 MPN/g) bacteria. These results support the use of ice slurries as a postharvest application for rapid cooling of oysters to minimize Vibrio growth.

The Fish Pathogen Vibrio vulnificus Biotype 2: Epidemiology, Phylogeny, and Virulence Factors Involved in Warm-Water Vibriosis

Vibrio vulnificus biotype 2 is the etiological agent of warm-water vibriosis, a disease that affects eels and other teleosts, especially in fish farms. Biotype 2 is polyphyletic and probably emerged from aquatic bacteria by acquisition of a transferable virulence plasmid that encodes resistance to innate immunity of eels and other teleosts. Interestingly, biotype 2 comprises a zoonotic clonal complex designated as serovar E that has extended worldwide. One of the most interesting virulence factors produced by serovar E is RtxA1 3 , a multifunctional protein that acts as a lethal factor for fish, an invasion factor for mice, and a survival factor outside the host. Two practically identical copies of rtxA1 3 are present in all biotype 2 strains regardless of the serovar, one in the virulence plasmid and the other in chromosome II. The plasmid also contains other genes involved in survival and growth in eel blood: vep07 , a gene for an outer membrane (OM) lipoprotein involved in resistance to eel serum and vep20 , a gene for an OM receptor specific for eel-transferrin and, probably, other related fish transferrins. All the three genes are highly conserved within biotype 2, which suggests that they are under a strong selective pressure. Interestingly, the three genes are related with transferable plasmids, which emphasizes the role of horizontal gene transfer in the evolution of V. vulnificus in nutrient-enriched aquatic environments, such as fish farms.

Comparative genomic analysis of clinical and environmental Vibrio vulnificus isolates revealed biotype 3 evolutionary relationships

In 1996 a common-source outbreak of severe soft tissue and bloodstream infections erupted among Israeli fish farmers and fish consumers due to changes in fish marketing policies. The causative pathogen was a new strain of Vibrio vulnificus, named biotype 3, which displayed a unique biochemical and genotypic profile. Initial observations suggested that the pathogen erupted as a result of genetic recombination between two distinct populations. We applied a whole genome shotgun sequencing approach using several V. vulnificus strains from Israel in order to study the pan genome of V. vulnificus and determine the phylogenetic relationship of biotype 3 with existing populations. The core genome of V. vulnificus based on 16 draft and complete genomes consisted of 3068 genes, representing between 59 and 78% of the whole genome of 16 strains. The accessory genome varied in size from 781 to 2044 kbp. Phylogenetic analysis based on whole, core, and accessory genomes displayed similar clustering patterns with two main clusters, clinical (C) and environmental (E), all biotype 3 strains formed a distinct group within the E cluster. Annotation of accessory genomic regions found in biotype 3 strains and absent from the core genome yielded 1732 genes, of which the vast majority encoded hypothetical proteins, phage-related proteins, and mobile element proteins. A total of 1916 proteins (including 713 hypothetical proteins) were present in all human pathogenic strains (both biotype 3 and non-biotype 3) and absent from the environmental strains. Clustering analysis of the non-hypothetical proteins revealed 148 protein clusters shared by all human pathogenic strains; these included transcriptional regulators, arylsulfatases, methyl-accepting chemotaxis proteins, acetyltransferases, GGDEF family proteins, transposases, type IV secretory system (T4SS) proteins, and integrases. Our study showed that V. vulnificus biotype 3 evolved from environmental populations and formed a genetically distinct group within the E-cluster. The unique epidemiological circumstances facilitated disease outbreak and brought this genotype to the attention of the scientific community.

Genome-wide SNP-genotyping array to study the evolution of the human pathogen Vibrio vulnificus biotype 3

Vibrio vulnificus is an aquatic bacterium and an important human pathogen. Strains of V. vulnificus are classified into three different biotypes. The newly emerged biotype 3 has been found to be clonal and restricted to Israel. In the family Vibrionaceae, horizontal gene transfer is the main mechanism responsible for the emergence of new pathogen groups. To better understand the evolution of the bacterium, and in particular to trace the evolution of biotype 3, we performed genome-wide SNP genotyping of 254 clinical and environmental V. vulnificus isolates with worldwide distribution recovered over a 30-year period, representing all phylogeny groups. A custom single-nucleotide polymorphism (SNP) array implemented on the Illumina GoldenGate platform was developed based on 570 SNPs randomly distributed throughout the genome. In general, the genotyping results divided the V. vulnificus species into three main phylogenetic lineages and an additional subgroup, clade B, consisting of environmental and clinical isolates from Israel. Data analysis suggested that 69% of biotype 3 SNPs are similar to SNPs from clade B, indicating that biotype 3 and clade B have a common ancestor. The rest of the biotype 3 SNPs were scattered along the biotype 3 genome, probably representing multiple chromosomal segments that may have been horizontally inserted into the clade B recipient core genome from other phylogroups or bacterial species sharing the same ecological niche. Results emphasize the continuous evolution of V. vulnificus and support the emergence of new pathogenic groups within this species as a recurrent phenomenon. Our findings contribute to a broader understanding of the evolution of this human pathogen.

Current concepts in the management of necrotizing fasciitis

Necrotizing fasciitis (NF) is a severe, rare, potentially lethal soft tissue infection that develops in the scrotum and perineum, the abdominal wall, or the extremities. The infection progresses rapidly, and septic shock may ensue; hence, the mortality rate is high (median mortality 32.2%). Prognosis becomes poorer in the presence of co-morbidities, such as diabetes mellitus, immunosuppression, chronic alcohol disease, chronic renal failure, and liver cirrhosis. NF is classified into four types, depending on microbiological findings. Most cases are polymicrobial, classed as type I. The clinical status of the patient varies from erythema, swelling, and tenderness in the early stage to skin ischemia with blisters and bullae in the advanced stage of infection. In its fulminant form, the patient is critically ill with signs and symptoms of severe septic shock and multiple organ dysfunction. The clinical condition is the most important clue for diagnosis. However, in equivocal cases, the diagnosis and severity of the infection can be secured with laboratory-based scoring systems, such as the laboratory risk indicator for necrotizing fasciitis score or Fournier's gangrene severity index score, especially in regard to Fournier's gangrene. Computed tomography or ultrasonography can be helpful, but definitive diagnosis is attained by exploratory surgery at the infected sites. Management of the infection begins with broad-spectrum antibiotics, but early and aggressive drainage and meticulous debridement constitute the mainstay of treatment. Postoperative management of the surgical wound is also important for the patient's survival, along with proper nutrition. The vacuum-assisted closure system has proved to be helpful in wound management, with its combined benefits of continuous cleansing of the wound and the formation of granulation tissue.

The interaction of human microbial pathogens, particulate material and nutrients in estuarine environments and their impacts on recreational and shellfish waters

Anthropogenic activities have increased the load of faecal bacteria, pathogenic viruses and nutrients in rivers, estuaries and coastal areas through point and diffuse sources such as sewage discharges and agricultural runoff. These areas are used by humans for both commercial and recreational activities and are therefore protected by a range of European Directives. If water quality declines in these zones, significant economic losses can occur. Identifying the sources of pollution, however, is notoriously difficult due to the ephemeral nature of discharges, their diffuse source, and uncertainties associated with transport and transformation of the pollutants through the freshwater-marine interface. Further, significant interaction between nutrients, microorganisms and particulates can occur in the water column making prediction of the fate and potential infectivity of human pathogenic organisms difficult to ascertain. This interaction is most prevalent in estuarine environments due to the formation of flocs (suspended sediment) at the marine-freshwater interface. A range of physical, chemical and biological processes can induce the co-flocculation of microorganisms, organic matter and mineral particles resulting in pathogenic organisms becoming potentially protected from a range of biotic (e.g. predation) and abiotic stresses (e.g. UV, salinity). These flocs contain and retain macro- and micro- nutrients allowing the potential survival, growth and transfer of pathogenic organisms to commercially sensitive areas (e.g. beaches, shellfish harvesting waters). The flocs can either be transported directly to the coastal environment or can become deposited in the estuary forming cohesive sediments where pathogens can survive for long periods. Especially in response to storms, these sediments can be subsequently remobilised releasing pulses of potential pathogenic organisms back into the water column leading to contamination of marine waters long after the initial contamination event occurred. Further work, however, is still required to understand and predict the potential human infectivity of pathogenic organisms alongside the better design of early warning systems and surveillance measures for risk assessment purposes.

Vibrio vulnificus outbreaks in Dutch eel farms since 1996: strain diversity and impact

Vibrio vulnificus is a potentially zoonotic bacterial pathogen of fish, which can infect humans (causing necrotic fasciitis). We analysed 24 V. vulnificus isolates (from 23 severe eel disease outbreaks in 8 Dutch eel farms during 1996 to 2009, and 1 clinical strain from an eel farmer) for genetic correlation and zoonotic potential. Strains were typed using biotyping and molecular typing by high-throughput multilocus sequence typing (hiMLST) and REP-PCR (Diversilab®). We identified 19 strains of biotype 1 and 5 of biotype 2 (4 from eels, 1 from the eel farmer), that were subdivided into 8 MLST types (ST) according to the international standard method. This is the first report of V. vulnificus biotype 1 outbreaks in Dutch eel farms. Seven of the 8 STs, of unknown zoonotic potential, were newly identified and were deposited in the MLST database. The REP-PCR and the MLST were highly concordant, indicating that the REP-PCR is a useful alternative for MLST. The strains isolated from the farmer and his eels were ST 112, a known potential zoonotic strain. Antimicrobial resistance to cefoxitin was found in most of the V. vulnificus strains, and an increasing resistance to quinolones, trimethoprim + sulphonamide and tetracycline was found over time in strain ST 140. Virulence testing of isolates from diseased eels is recommended, and medical practitioners should be informed about the potential risk of zoonotic infections by V. vulnificus from eels for the prevention of infection especially among high-risk individuals. Additional use of molecular typing methods such as hiMLST and Diversilab® is recommended for epidemiological purposes during V. vulnificus outbreaks.

Vibrio vulnificus biotype 3 multifunctional autoprocessing RTX toxin is an adenylate cyclase toxin essential for virulence in mice

Vibrio vulnificus is an environmental organism that causes both food-borne and wound infections with high morbidity and mortality in humans. The annual incidence and global distribution of infections associated with this pathogen are increasing with climate change. In the late 1990s, an outbreak of tilapia-associated wound infections in Israel was linked to a previously unrecognized variant of V. vulnificus designated biotype 3. The sudden emergence and clonality of the outbreak suggest that this strain may be a true newly emergent pathogen with novel virulence properties compared to those of other V. vulnificus strains. In a subcutaneous infection model to mimic wound infection, the multifunctional autoprocessing RTX (MARTX) toxin of biotype 3 strains was shown to be an essential virulence factor contributing to highly inflammatory skin wounds with severe damage affecting every tissue layer. We conducted a sequencing-based analysis of the MARTX toxin and found that biotype 3 MARTX toxin has an effector domain structure distinct from that of either biotype 1 or biotype 2. Of the two new domains identified, a domain similar to Pseudomonas aeruginosa ExoY was shown to confer adenylate cyclase activity on the MARTX toxin. This is the first demonstration that the biotype 3 MARTX toxin is essential for virulence and that the ExoY-like MARTX effector domain is a catalytically active adenylate cyclase.

PVv3, a new shuttle vector for gene expression in Vibrio vulnificus

An efficient electroporation procedure for Vibrio vulnificus was designed using the new cloning vector pVv3 (3,107 bp). Transformation efficiencies up to 2 × 10(6) transformants per μg DNA were achieved. The vector stably replicated in both V. vulnificus and Escherichia coli and was also successfully introduced into Vibrio parahaemolyticus and Vibrio cholerae. To demonstrate the suitability of the vector for molecular cloning, the green fluorescent protein (GFP) gene and the vvhBA hemolysin operon were inserted into the vector and functionally expressed in Vibrio and E. coli.

Host-nonspecific iron acquisition systems and virulence in the zoonotic serovar of Vibrio vulnificus

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.

Temporal and spatial distribution patterns of potentially pathogenic Vibrio spp. at recreational beaches of the German north sea

The number of reported Vibrio-related wound infections associated with recreational bathing in Northern Europe has increased within the last decades. In order to study the health risk from potentially pathogenic Vibrio spp. in the central Wadden Sea, the seasonal and spatial distribution of Vibrio vulnificus, Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio cholerae were investigated at ten recreational beaches in this area over a 2-year period. V. alginolyticus and V. parahaemolyticus were found to be omnipresent all year round in the study area, while V. vulnificus occurrence was restricted to summer months in the estuaries of the rivers Ems and Weser. Multiple linear regression models revealed that water temperature is the most important determinant of Vibrio spp. occurrence in the area. Differentiated regression models showed a species-specific response to water temperature and revealed a particularly strong effect of even minor temperature increases on the probability of detecting V. vulnificus in summer. In sediments, Vibrio spp. concentrations were up to three orders of magnitude higher than in water. Also, V. alginolyticus and V. parahaemolyticus were found to be less susceptible towards winter temperatures in the benthic environment than in the water, indicating an important role of sediments for Vibrio ecology. While only a very small percentage of tested V. parahaemolyticus proved to be potentially pathogenic, the presence of V. vulnificus during the summer months should be regarded with care.

Genotypic diversity and virulence characteristics of clinical and environmental Vibrio vulnificus isolates from the Baltic Sea region

The genetic diversity of Vibrio vulnificus isolates from clinical and environmental sources originating from the Baltic Sea region was evaluated by multilocus sequence typing (MLST), and possible relationships between MLST clusters, potential genotypic and phenotypic traits associated with pathogenicity, and source of isolation were investigated. The studied traits included genotyping of polymorphic loci (16S rRNA, vcg, and pilF), presence/absence of potential virulence genes, including nanA, nab, and genes of pathogenicity regions, metabolic features, hemolytic activity, resistance to human serum, and cytotoxicity to human intestinal cells. MLST generated 35 (27 new) sequence types and divided the 53 isolates (including four reference strains) into two main clusters, with cluster I containing biotype 1 and 2 isolates of mainly environmental origin and cluster II containing biotype 1 isolates of mainly clinical origin. Cluster II isolates were further subdivided into two branches. Branch IIB included isolates from recent cases of wound infections that were acquired at the German Baltic Sea coastline between 2010 and 2011 and isolates from seawater samples of the same regions isolated between 1994 and 2010. Comparing the MLST data with the results of genotyping and phenotyping showed that strains of MLST cluster II possess a number of additional pathogenicity-associated traits compared to cluster I strains. Rapid microbiological methods such as matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry combined with typing of selected virulence-associated traits (e.g., serum resistance, mannitol fermentation, nanA, and pathogenicity region XII) could be used for risk assessment purposes regarding V. vulnificus strains isolated from the Baltic Sea region.

Distribution of virulence markers among Vibrio vulnificus isolates of clinical and environmental origin and regional characteristics in Japan

Background

Vibrio vulnificus is an opportunistic human pathogen that is widely distributed in estuarine environments and is capable of causing necrotizing fasciitis and sepsis. In Japan, based on epidemiological research, the incidences of V. vulnificus were concentrated in Kyusyu, mainly in coastal areas of the Ariake Sea. To examine the virulence potential, various genotyping methods have recently been developed. This study aimed to investigate the distribution of virulence markers among V. vulnificus isolates of clinical and environmental origin in three coastal areas with different infection incidences and to determine whether these isolates have the siderophore encoding gene viuB.

Methodology/Principal Findings

We examined the distribution of genotypes of the 16S ribosomal ribonucleic acid (rRNA) gene, vvhA, vcg, and capsular polysaccharide (CPS), and the presence of viuB in 156 isolates collected from patients and environmental samples in Japan. The environmental samples were collected from three coastal areas: the Ariake Sea, Ise & Mikawa Bay, and Karatsu Bay. The results showed disparity in the ratios of genotypes depending on the sample origins. V. vulnificus isolates obtained from patients were classified into the clinical type for all genotypes. In the environmental isolates, the ratios of the clinical type for genotypes of the 16S rRNA gene, vvhA, and vcg were in the order of the Ariake Sea>Ise & Mikawa Bay>Karatsu Bay. Meanwhile, CPS analysis showed no significant difference. Most isolates possessed viuB.

Conclusions

Many V. vulnificus belonging to the clinical type existed in the Ariake Sea. Three coastal areas with different infection incidences showed distinct ratios of genotypes. This may indicate that the distribution of clinical isolates correlates with the incidence of V. vulnificus infection.

Prevalence and population structure of Vibrio vulnificus on fishes from the northern Gulf of Mexico

The prevalence of Vibrio vulnificus on the external surfaces of fish from the northern Gulf of Mexico was determined in this study. A collection of 242 fish comprising 28 species was analyzed during the course of 12 sampling trips over a 16-month period. The prevalence of V. vulnificus was 37% but increased up to 69% in summer. A positive correlation was found between the percentages of V. vulnificus-positive fish and water temperatures, while salinity and V. vulnificus-positive fish prevalence were inversely correlated. A general lineal model (percent V. vulnificus-positive fish = 0.5930 - 0.02818 × salinity + 0.01406 × water temperature) was applied to best fit the data. Analysis of the population structure was carried out using 244 isolates recovered from fish. Ascription to 16S rRNA gene types indicated that 157 isolates were type A (62%), 72 (29%) were type B, and 22 (9%) were type AB. The percentage of type B isolates, considered to have greater virulence potential, was higher than that previously reported in oyster samples from the northern Gulf of Mexico. Amplified fragment length polymorphism (AFLP) was used to resolve the genetic diversity within the species. One hundred twenty-one unique AFLP profiles were found among all analyzed isolates, resulting in a calculated Simpson's index of diversity of 0.991. AFLP profiles were not grouped on the basis of collection date, fish species, temperature, or salinity, but isolates were clustered into two main groups that correlated precisely with 16S rRNA gene type. The population of V. vulnificus associated with fishes from the northern Gulf of Mexico is heterogeneous and includes strains of great virulence potential.

[Vibrio infections from food and sea water. Introducing the "VibrioNet"]

Vibrio is a genus of bacteria present in surface and coastal waters as well as in marine organisms worldwide. In many countries, pathogenic Vibrio species are a main cause of bacterial diarrhea, which may result from comsumption of contaminated seafood and fish products or from drinking contaminated water. Vibrio infections may also gain in importance in our regions due to global warming and the increase in the world trade of seafood. The research network "VibrioNet" studies pathogenic Vibrios in the marine environment and in seafood consumed by humans as a potential, new emerging zoonotic agent. An assessment of the risk arising from pathogenic non-cholera-vibrios in central Europe is the target of a multidisciplinary research effort. The research network will be strengthened by cooperations with international partners from countries in which Vibrio infections play a major role (Bangladesh, Chile, India, Thailand, and Vietnam).

Occurrence and potential pathogenesis of Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus on the South Coast of Sweden

During the summer of 2006, several wound infections - of which three were fatal - caused by Vibrio cholerae were reported from patients who had been exposed to water from the Baltic Sea. Before these reports, we initiated a sampling project investigating the occurrence of potential human pathogenic V. cholerae, Vibrio vulnificus and Vibrio parahaemolyticus in The Sound between Sweden and Denmark. The Blue mussel (Mytilus edulis) was used as an indicator to follow the occurrence of vibrios over time. Molecular analyses showed high frequencies of the most potent human pathogenic Vibrio spp.; 53% of mussel samples were positive for V. cholerae (although none were positive for the cholera toxin gene), 63% for V. vulnificus and 79% for V. parahaemolyticus (of which 47% were tdh(+) and/or trh(+)). Viable vibrios were also isolated from the mussel meat and screened for virulence by PCR. The mortality of eukaryotic cells when exposed to bacteria was tested in vivo, with results showing that the Vibrio strains, independent of species and origin, were harmful to the cells. Despite severe infections and several deaths, no report on potential human pathogenic vibrios in this area had been published before this study.

Biological characteristics and pathogenicity of a highly pathogenic Shewanella marisflavi infecting sea cucumber, Apostichopus japonicus

Shewanella marisflavi isolate AP629 is described as a novel pathogen of sea cucumber. The LD(50) values (14 days) in sea cucumber, mice and swordtail fish were 3.89 × 10(6) , 6.80 × 10(4) and 4.85 × 10(4) CFU g(-1) body weight, respectively. Studies on S. marisflavi were conducted, including morphology, physiological and biochemical characteristics, haemolysis, whole-cell protein and 16S rDNA gene sequence. Colonies of S. marisflavi appeared faint red on marine agar and green on thiosulphate-citrate-bile salt-sucrose media. Shewanella marisflavi had polar flagella. The cells were Gram-negative, oxidase- and catalase-positive and not sensitive to O/129. The bacterium exhibited β-haemolysis on sheep blood agar and produced H(2) S. Shewanella marisflavi survived and grew at 4-35°C, pH 6.0-9.2 and in the presence of 0-8% NaCl. The whole-cell proteins included 13 discrete bands, and proteins of molecular weight 87, 44 and 39 kDa were found in all five strains of Shewanella spp. The difference in 16S rDNA gene sequences in S. marisflavi was at the 446 bp site: S. marisflavi (KCCM 41822) - G, isolate AP629 - A. This is the first report that Shewanella is pathogenic to sea cucumber.

A comparative epizootiologic study of the two fish-pathogenic serovars of Vibrio vulnificus biotype 2

Vibrio vulnificus biotype 2 is subdivided into two main serovars, serovar E, able to infect fish and humans, and serovar A, only virulent for fish. Serovar E emerged in 1976 as the causative agent of a haemorrhagic septicaemia (warm-water vibriosis) affecting eels cultured in brackish water. Serovar A emerged in 2000 in freshwater-cultured eels vaccinated against serovar E, causing warm-water vibriosis with fish showing a haemorrhagic intestine as the main differential sign. The aim of the present work was to compare the disease caused by both serovars in terms of transmission routes, portals of entry and host range. Results of bath, patch-contact and oral-anal challenges demonstrated that both serovars spread through water and infect healthy eels, serovar A entering mainly by the anus and serovar E by the gills. The course of the disease under laboratory conditions was similar for both serovars in terms of transmission and dependence of degree of virulence on water parameters (temperature and salinity). However, the decrease in degree of virulence in fresh water was significantly greater in serovar E than in serovar A. Finally, both serovars proved pathogenic for tilapia, sea bass and rainbow trout, but not for sea bream, with significant differences in degree of virulence only in rainbow trout. In conclusion, serovar A seems to represent a new antigenic form of V. vulnificus biotype 2 with an unusual portal of entry and is better adapted to fresh water than serovar E.

Environmental occurrence and clinical impact of Vibrio vulnificus and Vibrio parahaemolyticus: a European perspective

Vibrio vulnificus and Vibrio parahaemolyticus are ubiquitous Gram-negative bacterial pathogens found naturally in marine and estuarine waters, and are a leading cause of seafood-associated bacterial illness. These pathogens are commonly reported in the USA and in many Asian countries, including China, Japan and Taiwan; however, there is growing concern that V. vulnificus and V. parahaemolyticus may represent an important and increasing clinical problem in Europe. Several factors underlie the need for a greater understanding of these non-cholera vibrios within a European context. First, there is a growing body of evidence to suggest that V. vulnificus and V. parahaemolyticus infections are increasing, and tend to follow regional climatic trends, with outbreaks typically following episodes of unusually warm weather. Such findings are especially alarming given current predictions regarding warming of marine waters as a result of global climatic change. Second, a myriad of epidemiological factors may greatly increase the incidence as well as clinical burden of these pathogens - including increasing global consumption and trade of seafood produce coupled to an increase in the number of susceptible individuals consuming seafood produce. Finally, there is currently a lack of detailed surveillance information regarding non-cholerae Vibrio infections in Europe, as these pathogens are not notifiable in many countries, which probably masks the true clinical burden of many human infections. This review will present a pertinent overview of both the environmental occurrence and clinical impact of V. vulnificus and V. parahaemolyticus in Europe.

Necrotizing fasciitis

Necrotizing fasciitis (NF) is a necrotizing soft tissue infection that can cause rapid local tissue destruction, necrosis and life-threatening severe sepsis. Predisposing conditions for NF include diabetes, malignancy, alcohol abuse, and chronic liver and kidney diseases. NF is classified into two categories (types 1 and 2) based on causative microorganisms. The initial clinical picture of NF mimics that of cellulitis or erysipelas, including fever, pain, tenderness, swelling and erythema. The cardinal manifestations of NF are severe pain at onset out of proportion to local findings, hemorrhagic bullae and/or vital sign abnormality. In such cases, NF should be strongly suspected and immediate surgical intervention should be considered, along with broad-spectrum antimicrobials and general supportive measures, regardless of the findings of imaging tests.

Evaluation of genotypic and phenotypic methods to distinguish clinical from environmental Vibrio vulnificus strains

Vibrio vulnificus is a heterogeneous bacterial species that comprises virulent and avirulent strains from environmental and clinical sources that have been grouped into three biotypes. To validate the typing methods proposed to distinguish clinical from environmental isolates, we performed phenotypic (API 20E, API 20NE, and BIOLOG tests) and genetic (ribotyping and DNA polymorphism at several loci) studies with a large strain collection representing different biotypes, origins, and host ranges. No phenotypic method was useful for biotyping or grouping strains with regard to the origin of an isolate, and only the BIOLOG system was reliable for identifying the strains at the species level. DNA polymorphisms divided the population into three major profiles. Profile 1 strains were vcg type C, 16S rRNA type B, and vvh type 1 and included most of the biotype 1 human septicemic isolates; profile 2 strains were vcg type E, 16S rRNA type A, and vvh type 2 and included all biotype 2 isolates together with biotype 1 isolates from fish and water and some human isolates; and profile 3 strains were vcg type E, 16S rRNA type AB, and vvh type 2 and included biotype 3 strains. Ribotyping divided the species into two groups: one group that included profile 1 biotype 1 isolates and one group that included isolates of all three biotypes with the three profiles described above. In conclusion, no genotyping system was able to distinguish either clinical strains from environmental strains or biogroups within the species V. vulnificus, which suggests that new typing methodologies useful for public health have to be developed for this species.