Objective To understand the etiological and genomic characteristics of a rare serotype Vibrio parahaemolyticus O1:K36 strains isolated in a food poisoning event.

Methods In July 2024, a total of 12 anal swabs were collected from the food poisoning cases in Qingshanhu district of Nanchang, Jiangxi province. The 12 samples were subjected to bacteria enrichment and isolation. The isolated strains were biochemically identified, and virulence gene detection was performed by using polymerase chain reaction, along with antibiotic susceptibility testing. Pulse-field gel electrophoresis (PFGE) was used for molecular typing and clustering analysis on the strains detected in this food poisoning event. Whole-genome sequencing (WGS) was used to obtain the genomic sequences of the strains, and molecular serotyping was conducted to identify the K antigens of the strains.

Results Five Vibrio parahaemolyticus strains were isolated from the 12 anal swabs. All the strains belonged to serotype O1:K36 and carried the virulence genes tdh, toxRSnew, orf8, T3SS1, and T3SS2. All the 5 V. parahaemolyticus strains were sensitive to 17 antibiotics, but they all carried gene blaCARB-22. PFGE analysis revealed that all the strains had identical banding patterns, with the homology of 100.00%. WGS analysis showed that all the 5 V. parahaemolyticus strains belonged to ST3 and exhibited the closest genetic relationship with strains isolated in China in 2010.

Conclusion The food poisoning in Qingshanhu was caused by a rare serotype V. parahaemolyticus O1:K36, which belonged to ST3, indicating that it is necessary to strengthen the surveillance for this type strain.