A database for risk assessment and comparative genomic analysis of foodborne Vibrio parahaemolyticus in China.

Vibrio parahaemolyticus is a major foodborne pathogen worldwide. The increasing number of cases of V. parahaemolyticus infections in China indicates an urgent need to evaluate the prevalence and genetic diversity of this pathogenic bacterium. In this paper, we introduce the Foodborne Vibrio parahaemolyticus genome database (FVPGD), the first scientific database of foodborne V. parahaemolyticus distribution and genomic data in China, based on our previous investigations of V. parahaemolyticus contamination in different kinds of food samples across China from 2011 to 2016. The dataset includes records of 2,499 food samples and 643 V. parahaemolyticus strains from supermarkets and marketplaces distributed over 39 cities in China; 268 whole-genome sequences have been deposited in this database. A spatial view on the risk situations of V. parahaemolyticus contamination in different food types is provided. Additionally, the database provides a functional interface of sequence BLAST, core genome multilocus sequence typing, and phylogenetic analysis. The database will become a powerful tool for risk assessment and outbreak investigations of foodborne pathogens in China.

Plasmid dynamics in Vibrio parahaemolyticus strains related to shrimp Acute Hepatopancreatic Necrosis Syndrome (AHPNS).

Vibrio parahaemolyticus is a causative agent of acute hapatopancreatic necrosis syndrome (AHPNS) which causes early mortality in white shrimp. Emergence of AHPNS has caused tremendous economic loss for aquaculture industry particularly in Asia since 2010. Previous studies reported that strains causing AHPNS harbor a 69-kb plasmid with possession of virulence genes, pirA and pirB. However, genetic variation of the 69-kb plasmid among AHPNS related strains has not been investigated. This study aimed to analyze genetic composition and diversity of the 69-kb plasmid in strains isolated from shrimps affected by AHPNS. Plasmids recovered from V. parahaemolyticus strain VPE61 which represented typical AHPNS pathogenicity, strain VP2HP which did not represent AHPNS pathogenicity but was isolated from AHPNS affected shrimp and other AHPNS V. parahaemolyticus isolates in Genbank were investigated. Protein coding genes of the 69-kb plasmid from the strain VPE61 were identical to that of AHPNS strain from Vietnam except the inverted complement 3.4-kb transposon covering pirA and pirB. The strain VP2HP possessed remarkable large 183-kb plasmid which shared similar protein coding genes to those of the 69-kb plasmid from strain VPE61. However, the 3.4-kb transposon covering pirA and pirB was absent from the 183-kb plasmid in strain VP2HP. A number of protein coding genes from the 183-kb plasmid were also detected in other AHPNS strains. In summary, this study identified a novel 183-kb plasmid that is related to AHPNS causing strains. Homologous recombination of the 69-kb AHPNS plasmid and other naturally occurring plasmids together with loss and gain of AHPNS virulence genes in V. parahaemolyticus were observed. The outcome of this research enables understanding of plasmid dynamics that possibly affect variable degrees of AHPNS pathogenicity.

Prevalence of Vibrio parahaemolyticus in seafood products from hypermarkets in Shanghai.

BACKGROUND: Vibrio parahaemolyticus is an important gastroenteritis pathogen contaminating seafood in China. In this study a total of 992 seafood samples from major hypermarkets in Shanghai were monitored for prevalence and burden of V. parahaemolyticus from January 2011 to December 2012. Additionally, appropriate probability distributions for describing V. parahaemolyticus concentrations were assessed based on these surveillance data. RESULTS: Seventeen of 992 samples were positive for V. parahaemolyticus and the geometric mean was 0.1581 most probable number (MPN) g-1 . The variation in prevalence of V. parahaemolyticus was seasonal and the burden of contamination in August (0.1942 MPN g-1 ) was significant (P < 0.01) between 2011 and 2012. Also, the prevalence of V. parahaemolyticus was higher in shellfish and cephalopods than in other seafood (P < 0.05). By comparison, the lognormal distribution and integrated distribution showed no obvious difference for characterizing V. parahaemolyticus contamination. CONCLUSION: The low prevalence and burden found indicated that seafood from hypermarkets may not be an important risk source for V. parahaemolyticus infection in Shanghai, and more attention should be paid to other areas for selling seafood, such as farmlands or farmers' markets. The simple and effective lognormal distribution is recommended as a better choice for describing V. parahaemolyticus contamination in future risk assessment studies. © 2016 Society of Chemical Industry.

Epidemiological evidence of lesser role of thermostable direct hemolysin (TDH)-related hemolysin (TRH) than TDH on Vibrio parahaemolyticus pathogenicity.

Vibrio parahaemolyticus carrying the tdh gene, encoding the thermostable direct hemolysin (TDH), or the trh gene, encoding the TDH-related hemolysin (TRH), are both considered virulent strains. There are, however, disproportionally fewer reports of infections caused by seafood contaminated with trh-positive strains than by seafood contaminated with tdh-positive strains. Bivalves such as clams and oysters are the major seafood varieties associated with the infections. In this study, the prevalence of strains possessing the tdh and trh genes was investigated in Japan in 74 samples collected in 2007-2008 and in 177 samples collected in 2010 of domestic bivalves, bloody clams, hen clams, short-neck clams, and rock oysters. The tdh-positive and trh-negative, tdh-negative and trh-positive, and tdh-positive and trh-positive samples represented 5.4%, 12.2%, and 4.1% of all samples collected in 2007-2008, and 5.1%, 18.6%, and 5.6% of all samples collected in 2010, respectively. As determined by polymerase chain reaction, the prevalence of tdh negative and trh positive in all samples was two to four times higher than that of tdh positive and trh negative. In the samples collected in 2010, the tdh-negative and trh-positive V. parahaemolyticus (20 samples) was more often isolated than tdh-positive and trh-negative V. parahaemolyticus (7 samples). The most common serotype of tdh-positive isolates (22 of 24 strains) was pandemic O3:K6. The trh-positive isolates (61 strains) were various serotypes including OUT:KUT. In 330 V. parahaemolyticus outbreaks and sporadic infections in Japan, most outbreaks and sporadic infections were caused by tdh-positive and trh-negative strains (89.4%). The frequencies of infections caused by tdh-negative and trh-positive, and both tdh- and trh-positive strains were 1.2% and 3.0%, respectively. This finding suggests that the virulence of trh might be less than that of tdh, although trh-positive V. parahaemolyticus frequently contaminated bivalves.

Multipurpose assessment for the quantification of Vibrio spp. and total bacteria in fish and seawater using multiplex real-time polymerase chain reaction.

BACKGROUND: This study describes the first multiplex real-time polymerase chain reaction assay developed, as a multipurpose assessment, for the simultaneous quantification of total bacteria and three Vibrio spp. (V. parahaemolyticus, V. vulnificus and V. anguillarum) in fish and seawater. The consumption of raw finfish as sushi or sashimi has been increasing the chance of Vibrio outbreaks in consumers. Freshness and quality of fishery products also depend on the total bacterial populations present. RESULTS: The detection sensitivity of the specific targets for the multiplex assay was 1 CFU mL⁻¹ in pure culture and seawater, and 10 CFU g⁻¹ in fish. While total bacterial counts by the multiplex assay were similar to those obtained by cultural methods, the levels of Vibrio detected by the multiplex assay were generally higher than by cultural methods of the same populations. Among the natural samples without Vibrio spp. inoculation, eight out of 10 seawater and three out of 20 fish samples were determined to contain Vibrio spp. CONCLUSION: Our data demonstrate that this multiplex assay could be useful for the rapid detection and quantification of Vibrio spp. and total bacteria as a multipurpose tool for surveillance of fish and water quality as well as diagnostic method.

Assessment of polyaromatic hydrocarbon degradation by potentially pathogenic environmental Vibrio parahaemolyticus isolates from coastal Louisiana, USA.

A presumed Vibrio parahaemolyticus isolate from Chesapeake Bay, Maryland, USA was previously reported to grow on phenanthrene, a polyaromatic hydrocarbon (PAH) found in crude oil. Following the Deepwater Horizon oil spill in the Gulf of Mexico, concerns were raised that PAH-degrading V. parahaemolyticus could increase in abundance, leading to elevated risks of disease derived from shellfish consumption. To assess this possibility, we examined responses to naphthalene and phenanthrene of 17 coastal Louisiana environmental V. parahaemolyticus isolates representing five distinct genotypes. Isolates were obtained immediately after the spill began and after oil had reached the Louisiana coast. None of the isolates grew on or oxidized either substrate and a naphthalene degradation product, 1-naphthol, substantially inhibited growth of some isolates. The use of PAH by V. parahaemolyticus is unusual, and an increase in human health risks due to stimulation of V. parahaemolyticus growth by oil-derived PAH under in situ conditions appears unlikely.

Evaluation of restriction enzymes for standardizing pulsed-field gel electrophoresis protocol for rapid subtyping of Vibrio parahaemolyticus.

We evaluated the cost-effectiveness of the restriction enzymes with rare-cutting sites in the genome of Vibrio parahaemolyticus RIMD 2210633 for pulsed-field gel electrophoresis (PFGE) analysis. The evaluation indicated that PFGE with both NotI and SfiI was discriminatory, but NotI was more cost-effective. Based on the results of this study, we suggest using NotI and SfiI as the 1st and the 2nd restriction enzyme for standardizing the PulseNet PFGE protocol for molecular subtyping and global surveillance of V. parahaemolyticus.