Occurrence of pathogenic Vibrio parahaemolyticus in seafood distribution channels and their antibiotic resistance profiles in S. Korea.

This study investigated the occurrence of Vibrio parahaemolyticus in seafood distribution channels, and the incidence of pathogenic and antibiotic-resistant strains. One hundred sixty-seven samples (126 fishery samples and 41 environmental samples) were collected from fishery auction markets, fish markets and online markets in S. Korea from March to September, 2017. The samples were enriched in polymyxin broth and plated on CHROM agar Vibrio to isolate typical colonies. These were analysed by PCR to identify V. parahaemolyticus strains containing the hns gene and to examine the presence of pathogenic genes (tdh and trh). The isolates were screened for antibiotic susceptibility (amoxycillin/clavulanic acid, ampicillin (AMP), ampicillin/sulbactam, chloramphenicol, ciprofloxacin, erythromycin, gentamicin and tetracycline). Twenty-eight samples (16·8%) were V. parahaemolyticus-positive, and from the positive samples, three isolates (SMFM201708-OY1, SMFM201709-CO2-2 and SMFM201709-CO1-2) were pathogenic which contained thermostable direct haemolysin or thermostable direct-related haemolysin. These are the virulence factors associated with gastrointestinal symptoms. These three isolates were also resistant to AMP. These results indicate that there is high incidence of V. parahaemolyticus in seafood distribution channels, and three of the isolates were pathogenic, and the pathogenic strains showed AMP resistance. Therefore, food safety measures are necessary in a seafood distribution channel. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides evidence for the incidence of pathogenic Vibrio parahaemolyticus in seafood distribution channels, especially for a fishery auction market, which showed the highest contamination and is a first place for a seafood distribution channel. Thus, V. parahaemolyticus in a fishery auction market may be cross-contaminated during distribution, underlying the need of food safety regulation to control this pathogen in fishery auction market. Therefore, food safety regulation for fishery auction market should be established to control V. parahaemolyticus.