Population structure and genetic diversity of Vibrio parahaemolyticus from a coastal area of China based on a multi-locus sequence typing (MLST) scheme

The Gram-negative marine bacterium Vibrio parahaemolyticus has been identified as a major cause of bacterial food poisoning in China. Here, the population structure and genetic diversity of V. parahaemolyticus from Weihai, a coastal city in China, was studied by the multi-locus sequence typing (MLST) method. In this survey, we isolated 40 strains including environmental and clinical samples of patients with acute gastroenteritis or diarrhea; isolates from other countries were also included for comparison. DnaSP Version5, START V2, eBURST version3 and Mega 6 were used to analyse the data. We found that ST3 and ST332 were the most prevalent clones and that they were closely associated with acute diarrhoeal diseases. These STs showed a low dN/dS ratio and significant linkage disequilibrium. All isolates were divided into four clonal complexes, six groups and nine singletons, showing a high degree of genetic diversity. 18 STs, mostly from environmental isolates, were recognised by the MLST analysis for the first time. In conclusion, ST3 and ST332 were the epidemic STs in the coastal area. ST332 might be a region-specific ST, which needs to be confirmed by further analysis. Thus, the long-term monitoring of V. parahaemolyticus plays an important role in preventing and controlling the transmission between environment and people in Weihai.