Genomic analysis of two emergent Vibrio parahaemolyticus ecotypes

Vibrio parahaemolyticus [Vp] is a Gram-negative bacterium indigenous to marine coastal waters. Vp is also the causative agent of a mild to severe gastroenteritis associated with the consumption of raw or undercooked seafood. The majority of infections are caused by a genetically distinct ecotype commonly referred to as the pandemic clonal complex. However, localized outbreaks associated with non-pandemic ecotypes are frequently reported. In the East Pacific, two such ecotypes, identified as ST65 and ST417 by multilocus sequence typing, have been associated with outbreaks in Peru, Chile and the United States. In this study, we sequenced and assembled draft genomes from 4 clinical isolates (ST65: 3328, 3355; ST417: 3646, 3631) that were positive for both the thermostable direct hemolysin (tdh) and thermostable direct-related hemolysin (trh). When compared with the pandemic type strain (V. parahaemolyticus RIMD2210633), each of these isolates harbored more than 400 Kb of novel genetic material. Proteins encoded by this novel genetic material include CcdA-CcdB toxin-antitoxin systems, an efflux pump belonging to the multidrug and toxic efflux (MATE) family, and a repeats-in-toxin (RTX) gene cluster. These features share significant homology and synteny with virulence-associated features found in clinical V. vulnificus and Escherichia coli strains. We hypothesize that these features contribute to a pathogenic phenotype. The identification and characterization of multiple clinical ecotypes could improve efforts aimed at preventing V. parahaemolyticus infections. Further, a greater understanding of the species’ biogeography may lead to a more effective public health response.