Serlogical, virulence, and molecular characterization of clinical and seafood Vibrio parahaemolyticus isolates

In this study, 42 clinical and 114 seafood isolates of V. parahaemolyticus from Shanghai, China, were investigated. Serotypes, Kanagawa phenomenon (KP), potential virulence factors, and phylogenetic relationship (gyrB gene) of these isolates were analyzed. In 156 isolates, a total of 28 serotypes were identified and only 3 predominant serotypes (O1:KUT, O3:K6, and O4:K2) were in common between clinical and seafood isolates. Of these, O1:KUT and O3:K6 were pandemic-associated. Results showed that 95.2% (40/42) clinical and 1.8% (2/114) seafood isolates were tdh⁺and thus KP. All clinical and seafood isolates tested positive for the enolase, MAM7, T3SS1, and T6SS2 genes. The T3SS2 gene encodes a Type III secretion system, while the T6SS1 gene encodes a Type IV secretion system. Both play an important role in the pathogenicity of V. parahaemolyticus. Data showed that 100% (42/42) of the clinical isolates, but only 2.6% (3/114) of the seafood isolates, tested positive for T3SS2, while 88.1% (37/42) of the clinical isolates and 21.1% (24/114) of the seafood isolates tested positive for the T6SS1 gene. This suggests that strains containing T3SS2 and T6SS1 could be highly pathogenic to humans and a public health threat. This study assists in elucidating the potential pathogenicity of V. parahaemolyticus, through which allele of certain virulence factors is present in the isolate genome. Thus, providing a new mechanism to facilitate monitoring of this disease during an epidemic, as well as helping to lay the foundation to prevent and control the disease.IMPORTANCEVibrio parahaemolyticus is a globally significant foodborne pathogen, with its ability to infect humans through seafood consumption often linked to specific serotypes and the presence of key virulence factors encoded in its genome. In this study, we analyzed 42 clinical isolates and 114 seafood isolates of V. parahaemolyticus obtained from Shanghai, China. Comparative analysis revealed a marked enrichment of several virulence-associated genes in the clinical isolates. Notably, the thermostable direct hemolysin gene (tdh) was detected in 95.2% of clinical isolates, but in only 1.8% of seafood isolates. Furthermore, the Type III Secretion System 2 (T3SS2) was present in all clinical isolates (42/42, 100%), whereas it was found in just 2.6% (3/114) of seafood isolates. These findings enhance our understanding of the pathogenic potential of V. parahaemolyticus and provide a foundation for predicting disease outbreaks through the surveillance of specific genetic markers.