Analysis and source tracing of a congregative foodborne disease outbreak caused by Vibrio parahaemolyticus

ObjectiveUsing different enrichment methods to isolation Vibrio parahaemolyticus （VP） from environmental samples for support source tracing of a congregative foodborne disease outbreak.MethodsCollected the epidemiological data clinical information and multiple types samples of the foodborne disease outbreak. Real time PCR and bacterial culture were performed in the samples and whole genome sequencing and bioinformatics analysis were performed on the isolates.ResultsSeven VP isolates with O10：K4 serotype and tdh+ isolated from 7 samples （ included 4 patients and 3 environmental smear samples）， and the SNPs among the 7 VP isolates ranged from 0 to 5 based on the core genome single nucleotide polymorphisms （cgSNP） analysis. All environmental smear samples were negative for VP by real time PCR and culture method based on 3%NaCl Alkaline Peptone Water （APW） enhancement. But 3 environmental smear samples included E1， E2 and E6 were toxR+/tdh+ by real time PCR method after brain heart infusion broth （BHI） enhancement， and the Ct values of toxR and tdh of E1 and E2 were >30. Then add the BHI broth enriched of E1 and E2 to 3%NaCl APW for second cultured， respectively， and the Ct values of toxR and tdh of E1 and E2 were <30 by real time PCR. Finally， VP isolate were obtained from E1，E2 and E6， respectively.ConclusionUsing different bacterial enrichment methods and finally successfully to isolated VP in 3 environmental smear samples， afterwards the source tracing for a congregative foodborne disease outbreak caused by VP was successfully completed. Meanwhile， this study suggests that further in-depth research is needed on effective enrichment methods for VP in environmental smear samples.