Abstract
Vibrio parahaemolyticus can cause gastrointestinal illness through consumption of seafood. Despite frequent food-borne outbreaks of V. parahaemolyticus, only 19 strains have subjected to complete whole-genome analysis. In this study, a novel strain of V. parahaemolyticus, designated FORC_022 (Food-borne pathogen Omics Research Center_022), was isolated from soy sauce marinated crabs, and its genome and transcriptome were analyzed to elucidate the pathogenic mechanisms. FORC_022 did not include major virulence factors of thermostable direct hemolysin (tdh) and TDH-related hemolysin (trh). However, FORC_022 showed high cytotoxicity and had several V. parahaemolyticus islands (VPaIs) and other virulence factors, such as various secretion systems (types I, II, III, IV, and VI), in comparative genome analysis with CDC_K4557 (the most similar strain) and RIMD2210633 (genome island marker strain). FORC_022 harbored additional virulence genes, including accessory cholera enterotoxin, zona occludens toxin, and tight adhesion (tad) locus, compared with CDC_K4557. In addition, O3 serotype specific gene and the marker gene of pandemic O3:K6 serotype (toxRS) were detected in FORC_022. The expressions levels of genes involved in adherence and carbohydrate transporter were high, whereas those of genes involved in motility, arginine biosynthesis, and proline metabolism were low after exposure to crabs. Moreover, the virulence factors of the type III secretion system, tad locus, and thermolabile hemolysin were overexpressed. Therefore, the risk of foodborne-illness may be high following consumption of FORC_022 contaminated crab. These results provided molecular information regarding the survival and pathogenesis of V. parahaemolyticus FORC_022 strain in contaminated crab and may have applications in food safety.
Highlights
Vibrio parahaemolyticus is curved rod-shape, Gram-negative halophilic bacterium with a single polar flagellum and is abundant in estuarine environments and various seafood, including shellfish, oysters, clams, cockles, crabs, and shrimps (Joseph et al, 1982; Newton et al, 2014; Rodgers et al, 2014; Xu et al, 2014; Malcom et al, 2015)
We performed complete whole-genome sequencing of V. parahaemolyticus FORC_022 strain, isolated from soy sauce marinated swimming crabs in South Korea, and compared with complete sequences of this species from the public database. The transcriptome of this strain was analyzed to elucidate the potential pathogenicity of this strain in crabs using an artificial contact experiment. These results provide a better understanding of the pathogenicity of V. parahaemolyticus in crab-based foods and could facilitate the prevention of foodborne illness
The levels detected by real-time PCR were consistent with the transcriptome results. These results suggested that the potential risk of foodborne illness by ingestion of contaminated crab with FORC_022 could be high due to its virulence factors
Summary
Vibrio parahaemolyticus is curved rod-shape, Gram-negative halophilic bacterium with a single polar flagellum and is abundant in estuarine environments and various seafood, including shellfish, oysters, clams, cockles, crabs, and shrimps (Joseph et al, 1982; Newton et al, 2014; Rodgers et al, 2014; Xu et al, 2014; Malcom et al, 2015). This bacterium causes seafood borne gastroenteritis, and its infection is usually associated with the consumption of raw or undercooked seafood (Daniels et al, 2000; Letchumanan et al, 2016). The complete genomes of 19 strains of V. parahaemolyticus have been sequenced and are currently available from the National Center for Biotechnology Information (NCBI) database
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