Serology, virulence and molecular characteristics of Vibrio parahaemolyticus isolated from seafood in Zhejiang province

Abstract

Vibrio parahaemolyticus is a leading foodborne pathogen in southeastern China. In this study, 105 strains of V. parahaemolyticus were isolated from fresh seafood in 2013 and 2014. The serotypes, virulence-associated genes and sequence types (STs) of these strains were analyzed. 26 defined serotypes were identified and 69 strains (65.7%) had untypeable O or K antigen. 8 strains (7.6%) had the virulence-associated gene tdh and no strain carried the trh gene. 45.7% (48/105) of isolates contained all four T3SS1 genes and 50% (4/8) tdh+ trh- V. parahaemolyticus isolates lacked at least one of the four tested T3SS2α genes. 105 strains could be categorized into 84 STs and only 3 STs (ST3, ST8, ST675) had appeared in clinical strains. V. parahaemolyticus strains from seafood have more diverse and untypeable serotypes, less virulence-associated genes and more STs than strains from clinical sources.

Fig 1. Minimum spanning tree (MST) analysis of 105 seafood V. parahaemolyticus strains based on MLST data.

Each circle corresponds to a ST, and the size of each circle corresponds to the number of isolates. The relationships between strains are indicated by the lengths of the linking branches. Different colors indicate different serotypes and the number of isolates is expressed in brackets. Three MST figures were generated separately based on the available subtyping information. (A) ST vs serotypes; (B) ST vs pathogenic / non-pathogenic strains; (C) ST vs pandemic / non-pandemic strains.