Characterization of non-O1 and non-O139 Vibrio cholerae from seafood in Atlantic Canada

This study reports on a comprehensive genomic analysis of Vibrio cholerae strains isolated from shellfish grown in Atlantic Canada, specifically the non-choleragenic non-O1/non-O139 serogroups (NOVC), with the aim to provide a baseline in research of these bacteria and inform risk characterization to human exposure. Seafood homogenates were enriched using both standard saline and modified salt-free protocols, for recovery of V. cholerae. Isolates were identified by MALDI-TOF mass spectrometry (MS), and relatedness was assessed using composite correlation index (CCI) analysis and multilocus sequence typing (MLST). Genomic characterization through whole-genome sequencing revealed that Canadian NOVC isolates cluster with environmental strains previously reported from coastal New Hampshire, USA, while CCI and MLST analyses confirmed that the isolates are closely related to each other, with several representing novel sequence types. Bioinformatic screening identified gene clusters encoding secretion systems, adherence factors, and accessory toxins, although cholera toxin genes (ctx) and the toxin-coregulated pilus (tcp) were absent. Antimicrobial susceptibility testing indicated that all isolates were sensitive to the antibiotics tested and exhibited β-hemolysis. In light of the evidence of increase in sea surface water temperature, these findings provide the first comprehensive genomic and phenotypic baseline of NOVC strains from Canadian shellfish and underscore the importance of continued surveillance as a potential increase in NOVC prevalence and human exposure risk.