Etiological characteristics of Vibrio parahaemolyticus in two foodborne disease outbreaks in a county of Ningbo City: a genomic and phylogenetic analysis

ObjectiveTo analyze the etiological characteristics and homology of Vibrio parahaemolyticus strains isolated from two foodborne outbreaks in July 2024 in a county of Ningbo City.MethodsWhole genome sequencing was performed using the MGI sequencing platform to analyze virulence factors and antibiotic resistance genes. Sequence types （STs） were determined by multilocus sequence typing （MLST）， and cluster analysis was conducted by constructing phylogenetic trees based on core genome MLST （cgMLST）.ResultsAmong 22 isolates from two outbreaks， 10 STs were identified with ST3 being predominant. Antibiotic resistance profiling revealed 11 resistance genes from 7 categories， with all strains carrying CRP， tet（35）， rsmA and CRAB（Carbapenem-Resistant Acinetobacter baumannii）-associated β-lactamase genes. The tlh gene was detected in 9 strains， tdh in 16 strains， while trh was absent. cgMLST-based phylogenetic analysis showed significant clustering of case strains with ≤12 core allele differences， indicating highly close genetic distance between isolates across the two outbreaks.ConclusionThe Vibrio parahaemolyticus isolates exhibited diversity in STs， serotypes， and virulence/resistance gene profiles of isolates from two cases. cgMLST analysis provided high-resolution evidence for inter-outbreak homology determination， offering critical clues for tracing foodborne disease sources.