Analysis of antimicrobial resistance and virulence of Vibrio parahaemolyticus.

Vibrio parahaemolyticus poses dual threats to marine ecosystems and human health through seafood-borne transmission. This study reveals critical links between antibiotic resistance and virulence phenotypes in 95 V. parahaemolyticus isolates recovered from 284 retail seafood samples and 12 aquaculture samples (9 diseased shrimp and 3 water samples) collected from multiple coastal regions in Eastern and Southern China. All isolates exhibited multidrug resistance, with ubiquitous resistance to critically important antibiotics including polymyxins (100 %) and sulfonamides (100 %). Phenotypic analysis demonstrated near-universal strong biofilm formation (91/95 isolates) and heterogeneous motility profiles among strains. Crucially, significant correlations emerged that biofilm formation positively associated with tetracycline-class resistance, while swimming motility showed contrasting relationships that positively correlated with aminoglycoside/cephalosporin resistance but negatively linked to sulfonamide and tetracycline resistance. Hemolytic capacity inversely correlated with polymyxin and cephalosporin resistance. Experimental evolution of resistant strains confirmed collateral antibiotic cross-resistance and altered motility phenotypes. Our results provide mechanistic insights into pathogen persistence in polluted marine systems and highlight the ecological risks of antibiotic misuse in aquaculture, urging integrated countermeasures against this evolving threat.