In this study, we conducted serotyping, virulence gene detection and whole-genome sequencing on Vibrio parahaemolyticus strains collected from the Shanghai area between 2017 and 2021. A total of 369 genomic sequences of different serotypes were obtained, including 155 serotype O10:K4 strains. It was found that the O10:K4 serotype presents two subtypes (O10:K4 α and O10:K4 β ) co-circulated. They were both pandemic strains. Since 2020, the serotype O10:K4 has become the new dominant serotype in the Shanghai area. Among them, the O10:K4 α subtype first appeared in the Shanghai area in 2019, while the O10:K4 β subtype first appeared in 2020. However, the O10:K4 β subtype has a broader range of prevalence than the O10:K4 α subtype. Upon comparison, it was found that both the O10:K4 α subtype and the O10:K4 β subtype carry different unique genetic islands, and the compositions of the O antigen-determining region are also different. The O antigen-determining region has low similarity with the O10 group of V. parahaemolyticus , which is closer to the non-epidemic strain O4:K4. The SNP phylogenetic tree analysis revealed that the O10:K4 α subtype has a close genetic relationship with the O10:KUT serotype strains, while the O10:K4 β subtype has a closer relationship with the O10:K60 serotype strains, which is consistent with the results of core genome multilocus sequence typing analysis using the public database of V. parahaemolyticus genomes. The emergence of these two novel serotypes of V. parahaemolyticus is still in constant flux, so enhancing surveillance for V. parahaemolyticus is crucial for the prevention and control of foodborne illnesses it may cause.
Ni et al. (Mon,) studied this question.