Analysis on serotypes of Vibrio parahaemolyticus isolated from foodborne diarrhea cases in Huzhou, Zhejiang, 2017−2022

Objective To understand the serotype and molecular characteristics of Vibrio parahaemolyticus strains isolated from foodborne diarrhea cases in Huzhou, Zhejiang province, and provide evidence for the prevention and control of foodborne diseases.

Methods Serological typing, virulence gene testing, and multilocus sequence typing (MLST) were performed for the V. parahaemolyticus strains isolated from diarrhea cases.

Results From 2017 to 2022, a total of 688 strains of V. parahaemolyticus were isolated from foodborne diarrhea cases in Huzhou, and 33 serotypes were identified, in which O3: K6 (48.84%), O10: K4 (16.72%), and O4: KUT (12.79%) were predominant. The main virulence genotype was tlh+tdh+trh- (96.51%). Serotypes O3: K6 and O10: K4 all belonged to ST3, while serotype O4: KUT was divided into 3 STs, ST3, ST332 and ST2516/265. Core-genome MLST clustering analysis showed that O3:K6 and O10:K4 were basically clustered together. O4: KUT was clearly divided into three parts, and only the strains isolated in 2020 and 2022 could be divided into 2 clades. Sequence analysis revealed that 69 strains of V. parahaemolyticus carried 8 resistance related genes, involving 4 antibiotic categories.

Conclusion The predominant serotypes of V. parahaemolyticus in Huzhou had shifted obviously. It is necessary to carry out consecutive surveillance for serotypes and molecular characteristics of V. parahaemolyticus and pay attention to the possibility of a pandemic caused by serotypes O10: K4 and O4: KUT with increased detection in recent years.