Whole genome sequencing reveals great diversity of Vibrio spp in prawns at retail

Abstract

Consumption of prawns as a protein source has been on the rise worldwide with seafood identified as the predominant attributable source of human vibriosis. However, surveillance of non-cholera <i>Vibrio</i> is limited both in public health and in food. Using a population- and market share-weighted study design, 211 prawn samples were collected and cultured for <i>Vibrio</i> spp. Contamination was detected in 46 % of samples, and multiple diverse <i>Vibrio</i> isolates were obtained from 34 % of positive samples. Whole genome sequencing (WGS) and phylogenetic analysis illustrated a comprehensive view of <i>Vibrio</i> species diversity in prawns available at retail, with no known pathogenicity markers identified in <i>Vibrio parahaemolyticus</i> and <i>V. cholerae</i>. Antimicrobial resistance genes were found in 77 % of isolates, and 12 % carried genes conferring resistance to three or more drug classes. Resistance genes were found predominantly in <i>V. parahaemolyticus</i>, though multiple resistance genes were also identified in <i>V. cholerae</i> and <i>V. vulnificus</i>. This study highlights the large diversity in <i>Vibrio</i> derived from prawns at retail, even within a single sample. Although there was little evidence in this study that prawns are a major source of vibriosis in the UK, surveillance of non-cholera <i>Vibrio</i> is very limited. This study illustrates the value of expanding WGS surveillance efforts of non-cholera Vibrios in the food chain to identify critical control points for food safety through the production system and to determine the full extent of the public health impact.