Integrating genomic surveillance and policy intervention to reconstruct the antimicrobial resistance and zoonotic transmission dynamics of Vibrio parahaemolyticus.

Vibrio parahaemolyticus is a leading seafood foodborne pathogen of significant public health concern. This study conducted antimicrobial resistance (AMR) investigation and genomic surveillance of 239 V. parahaemolyticus isolates from 2378 seafood products across 12 major cities in China. Publicly available genomic data were also integrated to comprehensively characterize the pathogen's population structure, AMR trends, and human infection dynamics. Genomic analysis revealed high genomic diversity among seafood-derived V. parahaemolyticus and the presence of clinically significant ARGs such as blaNDM-1 and blaPER-3. A temporal shift in AMR was observed among V. parahaemolyticus in China, with AMR levels beginning to decline around 2016. This trend temporally coincided with the implementation of national antibiotic restriction policies, indicating a potential link between the observed trend and the policy implementation. Despite high genomic diversity of aquatic strains. Three dominant phylogenetic clades (C1-C3), primarily composed of sequence types ST3, ST2516, and ST332, consistently exhibited a strong association with human infections. These clades harbored fewer ARGs but were enriched in virulence genes, including T3SS2 and various environmental-adaptation determinants, offering a mechanistic explanation for their successful spread within human populations. Bayesian evolutionary analysis indicated a recent decline in the population sizes of these dominant clades. However, the thermostable direct hemolysin gene continued to enrich, indicating an elevated infection risk despite the population contraction. In summary, this study integrates genomic surveillance with policy interventions to provide comprehensive insights into the trends in AMR and the human infection characteristics of V. parahaemolyticus, offering valuable references for the prevention and control of foodborne infections caused by this pathogen.