Molecular analysis of foodborne Vibrio parahaemolyticus strains isolated in Shenyang area by pulsed-field gel electrophoresis

Objective To detect the virulence genes of the Vibrio parahaemolyticus(V.parahaemolyticus)strains which were isolated from the stool specimens of patients in Shenyang city from July to August,2010,and to subtype the isolates by pulsed-field gel electrophoresis(PFGE)analysis.Methods The virulence genes,thermostable direct hemolysin(tdh),thermostable direct hemolysin-related hemolysin(trh),and thermolabile hemolysin(tl)were amplified by PCR technique.The isolates were subtyped by PFGE analysis and the PFGE banding patterns were analyzed.Results The 24 V.parahaemolyticus isolates contained tdh and tl genes.This results revealed that they were all virulent strains.Ten banding patterns were observed by PFGE analysis.Of the 24 isolates,17 strains of O3:K6 were typed into 4 genotypes,but they had only 1-3 band differences and thus they were regarded as closely related.The findings indicated that the epidemic or outbreak of V.parahaemolyticus may exist in Shenyang region.Conclusion The V.parahaemolyticus strains prevalent in the region showed serotype and genotype diversity,but the closely related O3:K6 was the pandemic serotype.The results provide technical and data support for the establishment of V.parahaemolyticus molecular typing database,the outbreak investigation and the source-tracking.