PFGE analysis of a food poisoning event caused by multi-serotype Vibrio parahemolyticus

Objective To understand the infection source of a food poisoning event by using pulsed-field gel electrophoresis (PFGE) to detect three serotypes of Vibrio parahemolyticus isolates to know their homology and virulence factors. Methods According to WS 271-2007 and other standards, the isolation, biochemical and serological identification, KP test, drug susceptibility test and virulence gene detection of Vibrio parahemolyticus strains were conducted and PFGE molecular typing was conducted. Results Vibrio parahemolyticus strains were isolated from 17 samples, which belonged to three serotypes. Serotype O3:K6 was predominant, accounting for 70.59%. The serotypes O2:K3 and O2:K28 had different proportions. Six genotypes were detected by PFGE molecular typing, based on 100% similarity. Genotype XC12001 was predominant, accounting for 58.82%, while genotypes XC12002-XC12006 had different proportions. Cluster analysis showed that XC12001 and XC12002,XC12004 and XC12005 had close genetic relationship. The susceptibility test results of 17 strains of Vibrio parahemolyticus were similar. The ampicillin and amoxicillin resistance rates of all strains were 100%. Ten strains of Vibrio parahemolyticus O3:K6 carried tdh virulence genes, while the test results of tdh, trh1 and trh2 gens of other Vibrio parahemolyticus strains were all negative. Conclusion This food poisoning event was caused by co-infections of different clonal Vibrio parahemolyticus, with serotype O3:K6 being predominant. PFGE can be used in the source tracing and molecular epidemiological study of food poisoning.