Genomic and phenotypic analysis of virulence, antimicrobial resistance, and transmission routes of Vibrio vulnificus from food and clinical sources in China

Abstract

Vibrio vulnificus is a zoonotic pathogen that imposes significant economic burdens on healthcare and aquaculture. It represents a serious public health threat by causing primary septicemia through the consumption of raw shellfish and secondary septicemia via wound exposure to contaminated seawater. In this study, we aimed to compare the genomic features and virulence of foodborne V. vulnificus isolates with clinical strains to assess their public health threat. V. vulnificus isolates from Shenzhen (24 from seafood and meat, 4 clinical) were subjected to Whole-genome sequencing (WGS) and phenotypic assays including antibiotic susceptibility testing, human serum resistance, and a mouse infection model to evaluate virulence. Our results show that only a few food-derived isolates harbored antibiotic resistance genes (ARGs) encoding resistance towards rifamycin, aminoglycoside, trimethoprim, phenicol, quinolone, sulfonamide, and tetracycline; whereas all isolates possessed an extensive array of virulence factors (VFs) related to motility, adherence, and exotoxins. Two-thirds of food isolates were serum resistant and were able to survive in human serum like clinical isolates. In vivo experiments further confirmed that food-derived isolates can cause mouse mortality comparable to a clinical isolate. Genomic analysis of 685 V. vulnificus genomes from different provinces of China (including 28 genomes sequenced in this study and 657 publicly available genomes in China) revealed that V. vulnificus has an open pan-genome and there is no clear separation between clinical isolates and food isolates, either in phylogeny or VF profiles. Phylogeographic analysis indicated that Guangdong and Zhejiang provinces might play a key role in spreading V. vulnificus nationally. Collectively, this study highlights foodborne V. vulnificus isolates exhibit virulence potential equivalent to clinical strains and underscores the need for strict food safety monitoring and interventions to prevent severe infections.