Research – Prevalence, genomic characterization, and risk assessment of human pathogenic Vibrio species in seafood

Journal of Food Protection

Pathogenic Vibrio spp. are largely responsible for human diseases caused through consumption of contaminated seafood. The aim of this study was to determine the prevalence, population densities, species diversity and molecular characteristics of pathogenic Vibrio in various seafood commodities and its associated health risks. Samples of finfish and shellfish (oysters and sea urchins) were collected from different regions and analyzed for Vibrio using the Most Probable Number (MPN) technique. Genomic DNA of putative Vibrio isolates was analyzed by whole genome sequencing (WGS) for taxonomic identification and identification of genes responsible for virulence and antimicrobial resistance. The risk of vibrio-related illnesses due to the consumption of contaminated seafood was assessed using Risk Ranger. Population densities of presumptive Vibrio fell in the range of 2.6 – 4.4 Log MPN/g and correlated with seasonality, with the summer season favoring significantly (p < 0.05) higher Vibrio counts. A total of 15 Vibrio isolates were identified as V. alginolyticus (5), V . parahaemolyticus (6), V. harveyi (2) or V. diabolicus (2). Two of the six V. parahaemolyticus isolates (ST 2504 and ST 2505) originating from oysters were found to be either tdh + or trh + and thus considered a human pathogen due to elaboration of Thermostable Direct Hemolysin (TDH) or TDH-related hemolysin (TRH). In addition to virulence genes, the shellfish isolates also harbored genes encoding resistance to multiple antibiotics including tetracycline, penicillin, quinolone and beta-lactam antibiotics, thus arousing concern. The risk assessment exercise pointed to an estimated 21 annual cases of V. parahaemolyticus -associated gastroenteritis in the general population attributed to consumption of contaminated oysters. This study highlights not only the wide prevalence and diversity of Vibrio in seafood, but also the potential of certain strains to threaten public health.

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