Comparison of V. parahaemolyticus isolated from seafoods and cases of gastrointestinal disease in the UK

Virulence phenotypes differ between toxigenic Vibrio parahaemolyticus isolated from western coasts of Europe

Vibrio parahaemolyticus is the leading bacterial cause of gastroenteritis associated with seafood consumption worldwide. Not all members of the species are thought to be pathogenic, thus identification of virulent organisms is essential to protect public health and the seafood industry. Correlations of human disease and known genetic markers (e.g. thermostable direct hemolysin (TDH), TDH-related hemolysin (TRH)) appear complex. Some isolates recovered from patients lack these factors, while their presence has become increasingly noted in isolates recovered from the environment. Here, we used whole-genome sequencing in combination with mammalian and insect models of infection to assess the pathogenic potential of V. parahaemolyticus isolated from European Atlantic shellfish production areas. We found environmental V. parahaemolyticus isolates harboured multiple virulence-associated genes, including TDH and/or TRH. However, carriage of these factors did not necessarily reflect virulence in the mammalian intestine, as an isolate containing TDH and the genes coding for a type 3 secretion system (T3SS) 2α virulence determinant, appeared avirulent. Moreover, environmental V. parahaemolyticus lacking TDH or TRH could be assigned to groups causing low and high levels of mortality in insect larvae, with experiments using defined bacterial mutants showing that a functional T3SS1 contributed to larval death. When taken together, our findings highlight the genetic diversity of V. parahaemolyticus isolates found in the environment, their potential to cause disease and the need for a more systematic evaluation of virulence in diverse V. parahaemolyticus to allow better genetic markers.

Antibiotic Resistance and Genetic Profiles of Vibrio parahaemolyticus Isolated from Farmed Pacific White Shrimp (Litopenaeus vannamei) in Ningde Regions

To better understand the antibiotic resistance, virulence genes, and some related drug-resistance genes of Vibrio parahaemolyticus in farmed pacific white shrimp (Litopenaeus vannamei) in Ningde regions, Fujian province, we collected and isolated a total of 102 strains of V. parahaemolyticus from farmed pacific white shrimp in three different areas of Ningde in 2022. The Kirby-Bauer disk method was used to detect V. parahaemolyticus resistance to 22 antibiotics, and resistant genes (such as quinolones (qnrVC136, qnrVC457, qnrA), tetracyclines (tet A, tetM, tetB), sulfonamides (sulI, sulII, sulIII), aminoglycosides (strA, strB), phenicols (cat, optrA, floR, cfr), β-lactams (carB), and macrolides (erm)) were detected by using PCR. The findings in this study revealed that V. parahaemolyticus was most resistant to sulfamoxazole, rifampicin, and erythromycin, with resistance rates of 56.9%, 36.3%, and 33.3%, respectively. Flufenicol, chloramphenicol, and ofloxacin susceptibility rates were 97.1%, 94.1%, and 92.2%, respectively. In all, 46% of the bacteria tested positive for multi-drug resistance. The virulence gene test revealed that all bacteria lacked the tdh and trh genes. Furthermore, 91.84% and 52.04% of the isolates were largely mediated by cat and sulII, respectively, with less than 5% resistance to aminoglycosides and macrolides. There was a clear mismatch between the antimicrobial resistance phenotypes and genotypes, indicating the complexities of V. parahaemolyticus resistance.

The Viable but Non-Culturable (VBNC) State in Vibrio Species: Why Studying the VBNC State Now Is More Exciting than Ever

During periods that are not conducive for growth or when facing stressful conditions, Vibrios enter a dormant state called the Viable But Non-Culturable (VBNC) state. In this chapter, I will analyse the role of the VBNC state in Vibrio species survival and pathogenesis and the molecular mechanisms regulating this complex phenomenon. I will emphasise some of the novel findings that make studying the VBNC state now more exciting than ever and its significance in the epidemiology of these pathogens and critical role in food safety.

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.

Occurrence and antibiogram signatures of some Vibrio species recovered from selected rivers in South West Nigeria

Vibrio species, widely distributed in water environments, has emerged as a prominent cause of water and food-related disease outbreaks posing significant risk to human and animal health worldwide. About 40% of presumptive isolates recovered from four selected rivers in Southwest Nigeria and, established as Vibrio species genus through polymerase chain reaction techniques., were subjected to antibiotic susceptibility testing against a panel of 18 commonly used antibiotics. The relative prevalence of key Vibrio species (V. parahaemolyticus, V. vulnificus, V. mimicus, V. harveyi, and V. cholerae) was in the order 17%, 13.3%, 4.4%, 2.2%, and 2.2% respectively. Antibiotic resistance by all Vibrio species was mostly observed against doxycycline (71-89%), erythromycin (86-100%), tetracycline (71-89%), rifampicin (86-100%), and sulfamethoxazole (87-100%), though susceptibility to meropenem (86-100%), cephalothin (60-100%), norfloxacin (93-100%), ciprofloxacin (88-100%), amikacin (64-100%), gentamicin (57-74%), and trimethoprim/sulfamethoxazole (57-81%) was equally observed in all species. Vibrio mimicus expressed highest resistance against streptomycin and chloramphenicol (64%), while V. vulnificus (52%) and V. cholerae (57%) had the highest resistance against cephalothin. High resistance against ampicillin (57%) and amoxicillin (50%) was exhibited by V. cholerae and V. mimicus respectively. Indexes of multiple antibiotic resistances (MARI) among Vibrio species ranged between 0.11 and 0.72 with the highest MAR index of 0.72 observed in one isolate of V. vulnificus. This study reveals high prevalence of Vibrio species in the selected rivers as well as elevated resistance against some first-line antibiotics, which suggests possible inappropriate antimicrobial usage around study communities. We conclude that the freshwater resources investigated are unfit for domestic, industrial, and recreational uses without treatment prior to use and are potential reservoirs of antibiotic-resistant Vibrio species in this environment.

Assessment of Vibrio parahaemolyticus levels in oysters (Crassostrea virginica) and seawater in Delaware Bay in relation to environmental conditions and the prevalence of molecular markers to identify pathogenic Vibrio parahaemolyticus strains

This study identified Vibrio parahaemolyticus in oyster and seawater samples collected from Delaware Bay from June through October of 2016. Environmental parameters including water temperature, salinity, dissolved oxygen, pH, and chlorophyll a were measured per sampling event. Oysters homogenate and seawater samples were 10-fold serially diluted and directly plated on CHROMagarᵀᴹ Vibrio medium. Presumptive V. parahaemolyticus colonies were counted and at least 20% of these colonies were selected for molecular chracterization. V. parahaemolyticus isolates (n = 165) were screened for the presence of the species-specific thermolabile hemolysin (tlh) gene, the pathogenic thermostable direct hemolysin (tdh)/ thermostable related hemolysin (trh) genes, the regulatory transmembrane DNA-binding gene (toxR), and V. parahaemolyticus metalloprotease (vpm) gene using a conventional PCR. The highest mean levels of the presumptive V. parahaemolyticus were 9.63×10³ CFU/g and 1.85×10³ CFU/mL in the oyster and seawater samples, respectively, during the month of July. V. parahaemolyticus levels in oyster and seawater samples were significantly positively correlated with water temperature. Of the 165 isolates, 137 (83%), 110 (66.7%), and 108 (65%) were tlh⁺, vpm⁺, and toxR⁺, respectively. Among the V. parahaemolyticus (tlh⁺) isolates, 7 (5.1%) and 15 (10.9%) were tdh⁺ and trh⁺, respectively, and 24 (17.5%), only oyster isolates, were positive for both genes. Potential pathogenic strains that possessed tdh and/or trh were notably higher in oyster (39%) than seawater (15.6%) isolates. The occurrence of total V. parahaemolyticus (tlh⁺) was not necessarily proportional to the potential pathogenic V. parahaemolyticus. Co-occurrence of the five genetic markers were observed only among oyster isolates. The co-occurrence of the gene markers showed a relatedness potential of tdh occurrence with vpm. We believe exploring the role of V. parahaemolyticus metalloprotease and whether it is involved in the toxic activity of the thermostable direct hemolysin (TDH) protein can be of significance. The outcomes of this study will provide some foundation for future studies regarding pathogenic Vibrio dynamics in relation to environmental quality.

Prevalence, Virulence Characterization, AMR Pattern and Genetic Relatedness of Vibrio parahaemolyticus Isolates From Retail Seafood of Kerala, India

Vibrio parahaemolyticus, a halophilic bacterium often found in the marine or estuarine environment is a well-known enteropathogen responsible for foodborne outbreaks associated with seafood. The pathogenic strains of V. parahaemolyticus are marked by the presence of thermostable direct hemoylsin (tdh) and/or TDH related hemolysin (trh) genes. This study aimed to investigate the prevalence and characteristics of potentially pathogenic V. parahaemolyticus in selected retail markets of Cochin, Kerala, along the south-western coast of the Indian subcontinent. One hundred samples collected from 10 retail markets were analyzed for the presence of pathogenic isolates of V. parahaemolyticus. Out of the 721 presumptive isolates, 648 were confirmed to be V. parahaemolyticus by toxR gene amplification, among which 29 were Kanagawa phenomenon (KP) positive. Among these potentially pathogenic isolates, 17 possessed the tdh gene whereas none of them had the trh gene. The faint amplification bands produced during the amplification of tdh gene from two isolates was confirmed by sequencing. Multiplex O serotyping identified O1 serotype as the most prevalent serotype among the 29 potentially pathogenic isolates. Further, studies on the pandemic nature of these isolates revealed that 14 of the 29 were positive for the PGS-PCR, whereas all the isolates were negative for GS-PCR and HU-α PCR. The antibiogram of the isolates revealed that three isolates had significant Multiple Antibiotic Resistance (MAR) index of 0.2 or above. Pathogenic isolates resistant to second, third and fourth generation Cephalosporins were found to be present in the seafood studied. The molecular fingerprinting studies using ERIC-PCR, and PFGE revealed that three of these isolates shared close genetic similarities with the clinical strains. The environmental and seafood isolates that produced faint amplification bands during the amplification of tdh gene suggests that the tdh gene often goes undetected in environmental isolates. The conventional methods used to identify the pathogenic V. parahaemolyticus would be good for clinical isolates, but a more elaborate method is recommended for the detection of tdh gene in environmental isolates. This is the first comprehensive study on pathogenic V. parahaemolyticus in Kerala, India and demonstrates for the first time, the isolation of potentially pathogenic V. parahaemolyticus, carrying tdh gene from seafood collected from retail markets in Kerala.

Detection and Quantification of Total and Pathogenic Vibrio parahaemolyticus in Anadara subcrenata in the Zhoushan Archipelago

This study aimed to investigate the prevalence of total and pathogenic Vibrio parahaemolyticus in Anadara subcrenata sampled from aquafarms and retail markets in the Zhoushan islands during June 2013 to March 2015, using the most probable number-polymerase chain reaction (MPN-PCR) method. Total V. parahaemolyticus was detected in 265 (83.86%) samples with the density 0.3 to 2400 MPN/g. In total, 30.70% and 17.41% of the samples exceeded 100 MPN/g and 1,000 MPN/g, respectively. Both highest positive rate (98.99%) and highest prevalence (median = 210.0 MPN/g) were recorded in summer. Samples from aquafarms had a higher positive rate and median than those from retail markets. Pathogenic V. parahaemolyticus was detected both in aquafarms and retail markets in all seasons but not in winter. Among the 265 tlh-positive samples, 20 (7.55%) of the samples harbored tdh, and 5 (1.89%) of the samples harbored both tdh and trh. These results indicate that the Zhoushan archipelago is severely contaminated with V. parahaemolyticus in Anadara subcrenata; these results are applicable in risk assessment and to control the risk of food-borne disease caused by V. parahaemolyticus.

Genome Sequences of Four Vibrio parahaemolyticus Strains Isolated from the English Channel and the River Thames

Vibrio parahaemolyticus is the lead causative agent for seafood-borne human gastroenteritis. While its occurrence has traditionally been uncommon in Europe and the United Kingdom, rising sea surface temperatures have resulted in an increased prevalence. Here, we present the complete genome sequences of four novel V. parahaemolyticus strains isolated in the United Kingdom.

Vibrio parahaemolyticus is the lead causative agent for seafood-borne human gastroenteritis. While its occurrence has traditionally been uncommon in Europe and the United Kingdom, rising sea surface temperatures have resulted in an increased prevalence. Here, we present the complete genome sequences of four novel V. parahaemolyticus strains isolated in the United Kingdom.

Vibrio Parahaemolyticus: A Review on Distribution, Pathogenesis, Virulence Determinants and Epidemiology

Vibrio parahaemolyticus is a Gram-negative, halophilic bacterium isolated from marine environments globally. After the consumption of contaminated seafood, V. parahaemolyticus causes acute gastroenteritis. To initiate infection, a wide range of virulence factors are required. A complex group of genes is known to participate in the pathogenicity of V. parahaemolyticus; however, to understand the full mechanism of infection, extensive research is yet required. V. parahaemolyticus has become the leading cause of seafood-related gastroenteritis in Japan, the United States and several other parts of the world. In addition, outbreaks caused by the pandemic clone of this organism are escalating and spreading universally. To minimize the risk of V. parahaemolyticus infection and warrant the safety of seafood, collaboration between governments and scientists is required. We herein provide an updated review of the pathogenicity determinants and distribution of V. parahaemolyticus to deliver a better understanding of the significance of V. parahaemolyticus and its host-pathogen interactions.

Characterization of Vibrio parahaemolyticus clinical strains from Maryland (2012-2013) and comparisons to a locally and globally diverse V. parahaemolyticus strains by whole-genome sequence analysis

Vibrio parahaemolyticus is the leading cause of foodborne illnesses in the US associated with the consumption of raw shellfish. Previous population studies of V. parahaemolyticus have used Multi-Locus Sequence Typing (MLST) or Pulsed Field Gel Electrophoresis (PFGE). Whole genome sequencing (WGS) provides a much higher level of resolution, but has been used to characterize only a few United States (US) clinical isolates. Here we report the WGS characterization of 34 genomes of V. parahaemolyticus strains that were isolated from clinical cases in the state of Maryland (MD) during 2 years (2012-2013). These 2 years saw an increase of V. parahaemolyticus cases compared to previous years. Among these MD isolates, 28% were negative for tdh and trh, 8% were tdh positive only, 11% were trh positive only, and 53% contained both genes. We compared this set of V. parahaemolyticus genomes to those of a collection of 17 archival strains from the US (10 previously sequenced strains and 7 from NCBI, collected between 1988 and 2004) and 15 international strains, isolated from geographically-diverse environmental and clinical sources (collected between 1980 and 2010). A WGS phylogenetic analysis of these strains revealed the regional outbreak strains from MD are highly diverse and yet genetically distinct from the international strains. Some MD strains caused outbreaks 2 years in a row, indicating a local source of contamination (e.g., ST631). Advances in WGS will enable this type of analysis to become routine, providing an excellent tool for improved surveillance. Databases built with phylogenetic data will help pinpoint sources of contamination in future outbreaks and contribute to faster outbreak control.

Biochemical and molecular heterogeneity among isolates of Yersinia ruckeri from rainbow trout (Oncorhynchus mykiss, Walbaum) in North West Germany

Background

Enteric Redmouth Disease (ERM), caused by Yersinia ruckeri, is one of the most important infectious diseases in rainbow trout (Oncorhynchus mykiss) aquaculture in Europe. More recently, non-motile vaccine resistant isolates appear to have evolved and are causing disease problems throughout Europe, including Germany. The aim of this study was to analyse the variation of biochemical and molecular characteristics of Y. ruckeri isolates collected in north west Germany as a basis for strain differentiation. The isolates originated mainly from rainbow trout and were characterised by biochemical profiling, 16S rDNA sequencing, repetitive sequence-based PCRs, including (GTG)₅-PCR, BOX-PCR, ERIC-PCR and REP-PCR, and pulsed-field gel electrophoresis (PFGE).

Results

In total, 83 isolates were characterised, including 48 isolates collected during a field study in north west Germany. All isolates were confirmed as Y. ruckeri by the API 20E system. Five isolates were additionally confirmed as Y. ruckeri by Y. ruckeri-specific PCR and 16S rDNA sequencing. Only 17 isolates hydrolyzed Tween 80/20. Sixty-six isolates (79.5%) were non-motile. Two different patterns were obtained by REP-PCR, five patterns by ERIC-PCR, four patterns by (GTG)₅-PCR and three patterns by BOX-PCR. NotI-directed PFGE resulted in 17 patterns that differed from each other by 25–29 fragments. Isolates from the field study clustered together as PFGE type C. According to the results of API 20E, repetitive sequence-based PCRs and PFGE, these isolates could be subdivided into 27 different groups.

Conclusions

The detailed molecular and phenotypic characterisation scheme developed in this study could be used to help trace the dissemination of Y. ruckeri isolates, and thus may represent part of improved disease monitoring plans in the future.

Genetic relationships of Vibrio parahaemolyticus isolates from clinical, human carrier, and environmental sources in Thailand, determined by multilocus sequence analysis

Vibrio parahaemolyticus is a seafood-borne pathogenic bacterium that is a major cause of gastroenteritis worldwide. We investigated the genetic and evolutionary relationships of 101 V. parahaemolyticus isolates originating from clinical, human carrier, and various environmental and seafood production sources in Thailand using multilocus sequence analysis. The isolates were recovered from clinical samples (n = 15), healthy human carriers (n = 18), various types of fresh seafood (n = 18), frozen shrimp (n = 16), fresh-farmed shrimp tissue (n = 18), and shrimp farm water (n = 16). Phylogenetic analysis revealed a high degree of genetic diversity within the V. parahaemolyticus population, although isolates recovered from clinical samples and from farmed shrimp and water samples represented distinct clusters. The tight clustering of the clinical isolates suggests that disease-causing isolates are not a random sample of the environmental reservoir, although the source of infection remains unclear. Extensive serotypic diversity occurred among isolates representing the same sequence types and recovered from the same source at the same time. These findings suggest that the O- and K-antigen-encoding loci are subject to exceptionally high rates of recombination. There was also strong evidence of interspecies horizontal gene transfer and intragenic recombination involving the recA locus in a large proportion of isolates. As the majority of the intragenic recombinational exchanges involving recA occurred among clinical and carrier isolates, it is possible that the human intestinal tract serves as a potential reservoir of donor and recipient strains that is promoting horizontal DNA transfer, driving evolutionary change, and leading to the emergence of new, potentially pathogenic strains.

Molecular typing of Vibrio parahaemolyticus isolates from the middle-east coastline of China

The occurrence of outbreaks of Vibrio parahaemolyticus gastroenteritis in China highlights the need for strain characterization and subtyping of this pathogenic species. A total of 56 epidemiologically-unrelated strains of V. parahaemolyticus were isolated from clinical samples, seafood and various environmental sites in the middle-east coastline of China from 2006 to 2008. The isolates were characterized using four molecular typing methods, including ribotyping, enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR), pulsed-field gel electrophoresis (PFGE), and sequence analysis of the gyrB gene. Genetic profiles of cluster analysis from these molecular typing tests clearly showed that there were differences in potential pathogenicity among isolates from seafood and its environments. Genetic characterization of two isolates (F13 and QS2) that originated from seafood demonstrated that they were potentially pathogenic. Discriminatory indices of four typing methods for the 56 V. parahaemolyticus isolates were differentiated by Simpson's Index of Diversity. The discriminatory index of ERIC-PCR typing was maximal (D=0.942), while that of sequence analysis of the gyrB gene was minimal (D=0.702). The discriminatory ability was greatly enhanced (D=0.966) when ERIC-PCR was coupled with sequence analysis of the gyrB gene. These results suggest that ERIC-PCR combined with sequence analysis of gyrB gene may be a reliable, rapid typing strategy for V. parahaemolyticus strains.

Occurrence of Vibrio spp. in fish and shellfish collected from the Swiss market

The genus Vibrio includes gram-negative bacteria that inhabit estuarine ecosystems. V. cholerae, V. parahaemolyticus, and V. vulnificus pose a considerable public health threat as agents of sporadic and epidemic foodborne infections associated with the consumption of raw or undercooked contaminated fish or shellfish. In this study, we analyzed 138 fish and shellfish samples collected from the Swiss market (fish fillets [n = 102], bivalves [n = 34], and squid [n = 2]). Microbiological analysis was done according to International Organization for Standardization method 21872-1/21872-2:2007, using thiosulfate citrate bile sucrose agar and chromID Vibrio agar as selective agar. Presumptive-positive colonies on thiosulfate citrate bile sucrose agar or chromID Vibrio agar were picked and were identified by the API 20E and species-specific PCR systems. V. cholerae isolates were tested further by PCR for the presence of the cholera toxin A subunit gene (ctxA). V. parahaemolyticus isolates were tested by PCR for genes encoding for thermostable direct hemolysin (tdh) and TDH-related hemolysin (trh). V. cholerae was isolated from three samples and V. parahaemolyticus from eight samples. None of these strains harbored species-specific virulence factors. Further, V. alginolyticus was isolated from 40 samples, and V. fluvialis was isolated from 1 sample. Our study provides, for the first time, data for the assessment of exposure to Vibrio spp. in raw fish and bivalves consumed in Switzerland.

Pulsed-field gel electrophoresis and PCR characterization of environmental Vibrio parahaemolyticus strains of different origins

The present study used pulsed-field gel electrophoresis (PFGE) characterization to examine the intraspecies variability and genetic relationships among environmental isolates of Vibrio parahaemolyticus from different European countries. This is first study performed on environmental V. parahaemolyticus that included more than one European country.

Vibrio parahaemolyticus-associated gastroenteritis in Italy: persistent occurrence of O3:K6 pandemic clone and emergence of O1:KUT serotype

We report 2 cases of O3:K6 and O1:KUT Vibrio parahaemolyticus gastroenteritis associated with consumption of local mussels in Italy in 2008. Serotypic, antibiogram, toxigenic, and pulsed-field gel electrophoresis patterns of these strains were compared to those of other isolates collected from local clinical and seafood samples in 2007 to 2008. We underline the recurrent presence of O3:K6 pandemic clone and the emergence of trh-positive O1:KUT serotype in Italy.

Pathogenic Vibrio species in dutch shellfish destined for direct human consumption

Vibrio parahaemolyticus is a common cause of shellfish-related gastroenteritis all over the world. V. parahaemolyticus and Vibrio alginolyticus have previously been detected in water samples from the Oosterschelde, a large inlet on the North Sea, which is used for both recreational purposes and shellfish production. In 2006, oysters (Crassostrea gigas) from a noncommercial oyster bed in the Oosterschelde and oysters bought in Dutch fish shops were tested for the presence of pathogenic Vibrio species; in 2007 and 2008, oysters (C. gigas) and mussels (Mytilus edulis) from Oosterschelde production areas were examined. Total Vibrio numbers were related to water temperatures to study joint patterns. Vibrio was found in oysters and mussels from the production areas, and levels ranged from 6 to 622 most probable number (MPN) per g in oysters and 6 to 62 MPN/g in mussels. Vibrio levels in oysters from fish shops were 231 to >333 MPN/g, whereas levels in noncommercial oysters ranged from 231 to >2,398 MPN/g. About 80% of the isolated strains were V. alginolyticus, and approximately 10% were identified as V. parahaemolyticus. Vibrio counts in shellfish samples increased with increasing water temperature and declined when water temperatures dropped; Vibrio was not detected when water temperatures declined to <13.5 degrees C. Based on the obtained results and the known high V. parahaemolyticus dose (>10(4) cells per serving of oysters) required for infection, it is concluded that the risk of gastrointestinal infections with V. parahaemolyticus through consumption of shellfish from the Oosterschelde production sites is presumably low.

Prevalence, serotyping and molecular characterization of Vibrio parahaemolyticus in mussels from Italian growing areas, Adriatic Sea

The aims of this study were to investigate the prevalence of total and pathogenic Vibrio parahaemolyticus strains in Italian mussels from different geographical areas of the Adriatic Sea and to determine their serotypes, toxigenic profiles and pandemic potential. Out of 559 samples analysed during 2007, 65 (11.6%) were positive for V. parahaemolyticus. None of the isolates had the genes for thermostable direct haemolysin (tdh) and pandemic marker (toxRS), while five strains (7.7%) had that for TDH-related haemolysin (trh). Regarding geographical location of the toxigenic strains, three were from the Adriatic coast of Puglia, one from Veneto, and one from the Marches. The trh-positive V. parahaemolyticus isolates from Puglia belonged to O1:KUT (2/3) and O1:K37(1/3) serotypes, the trh-positive isolate from the Marches to OUT(O untypeable):KUT serotype, and that from Veneto to O3:KUT. The prevalence of trh-positive V. parahaemolyticus obtained from mussels in this study was higher respect to that reported in previous studies from other European and Extraeuropean countries. The Health Authorities should be more aware of the epidemiological role of environmental V. parahaemolyticus in local food-borne diseases, and increase the microbial surveillance on these microorganisms isolated from shellfish.

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.