Identification of a conserved pathogenicity island architecture in prevalent Vibrio parahaemolyticus clinical strains from North America and its application for pathogen enumeration in oysters

The incidences of gastric infections caused by V. parahaemolyticus, the most common seafood-borne bacterial pathogen, continue to rise, most notably in northern latitudes where infections have previously been rare. In the... [ view full abstract ]

The incidences of gastric infections caused by V. parahaemolyticus, the most common seafood-borne bacterial pathogen, continue to rise, most notably in northern latitudes where infections have previously been rare. In the northeastern United States, infections are primarily attributed to the ecologically invasive ST36 strain, which originated from the Pacific. While ST36 remains the most prevalent strain among clinical cases in the US and Canada, our analysis of clinical isolates from four reporting US States indicates an unrelated strain, ST631, is emerging as the predominant pathogenic lineage endemic to the northwest Atlantic. Analysis of the genomes of ST631 isolates revealed that this strain only recently evolved and appears to have rapidly spread along the North American Atlantic Coast where it has now been traced to shellfish harvest areas of five US states and Canada. Here we report that even though ST631 shares no recent ancestry with ST36, these strains have a strikingly similar organization of their virulence genes within a pathogenicity island. Phylogenetic analysis indicates a common origin for the island, despite the geographic barriers to the mixing of their populations. Similar islands were also present in most other emergent pathogen lineages from the Northeast US. We have developed a specific PCR-based assay to detect all pathogens harboring this island. If applied in parallel with standard assays for total and hemolysin-producing V. parahaemolyticus this assay could improve the accuracy of pathogen quantification in coastal areas of the US, aid in risk assessment, and inform management practices.