Co-existence of multiple distinct lineages in Vibrio parahaemolyticus serotype O4:K12.

Lin Zhao,Bo Pang,Yinghui Li,Hongyou Chen,Jie Li,Yu Du,Xavier Didelot,Meiling Chen,Zhenpeng Li,Hongqun Zhao,Min Chen,Qinghua Hu,Biao Kan

doi:10.1099/mgen.0.000287

Abstract

Vibrio parahaemolyticus is an important cause of foodborne gastroenteritis globally. Thermostable direct haemolysin (TDH) and the TDH-related haemolysin are the two key virulence factors in V. parahaemolyticus. Vibrio pathogenicity islands harbour the genes encoding these two haemolysins. The serotyping of V. parahaemolyticus is based on the combination of O and K antigens. Frequent recombination has been observed in V. parahaemolyticus , including in the genomic regions encoding the O and K antigens. V. parahaemolyticus serotype O4:K12 has caused gastroenteritis outbreaks in the USA and Spain. Recently, outbreaks caused by this serotype of V. parahaemolyticus have been reported in China. However, the relationships among this serotype of V. parahaemolyticus strains isolated in different regions have not been addressed. Here, we investigated the genome variation of the V. parahaemolyticus serotype O4:K12 using the whole-genome sequences of 29 isolates. We determined five distinct lineages in this strain collection. We observed frequent recombination among different lineages. In contrast, little recombination was observed within each individual lineage. We showed that the lineage of this serotype of V. parahaemolyticus isolated in America was different from those isolated in Asia and identified genes that exclusively existed in the strains isolated in America. Pan-genome analysis showed that strain-specific and cluster-specific genes were mostly located in the genomic islands. Pan-genome analysis also showed that the vast majority of the accessory genes in the O4:K12 serotype of V. parahaemolyticus were acquired from within the genus Vibrio . Hence, we have shown that multiple distinct lineages exist in V. parahaemolyticus serotype O4:K12 and have provided more evidence about the gene segregation found in V. parahaemolyticus isolated in different continents.

Highlights

Vibrio parahaemolyticus, a Gram-negative halophilic bacterium, is recognized as an important cause of foodborne gastroenteritis globally
In order to explore the population diversity of V. parahaemolyticus serotype O4:K12, we performed multilocus sequence typing (MLST) analysis of the 25 V. parahaemolyticus serotype O4:K12 isolated in routine surveillance in China between 2006 and 2014 (Table S2)
V. parahaemolyticus represents a population of high diversity and frequent recombination [12]

Summary

Introduction

A Gram-negative halophilic bacterium, is recognized as an important cause of foodborne gastroenteritis globally. The tdh and trh genes, Zhao et al, Microbial Genomics 2019 which encode TDH and TRH, respectively, are harboured on Vibrio pathogenicity islands (VPaIs). Besides these two VPaIs, several other VPaIs have been determined and some of these VPaIs have been considered to give advantages to the bacterium that carries them [4]. In pathogenic V. parahaemolyticus, TTSS2α and TTSS2β are genetically linked to tdh1/tdh and trh, respectively [4, 7, 9]. The VPaI-7 that harbour TTSS2 variants and their corresponding haemolysin genes are named VPaIα, VPaIβ and VPaIγ systematically [8]

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Results

Conclusion