Study On Serotype,molecular Characteristics And Traceability Of Vibrio Parahaemolyticus In Zibo From 2013 To 2016

Vibrio parahaemolyticus,a Gram-negative halophilic bacterium,is an important foodborne pathogen caused disease outbreaks in coastal areas of China,and may cause human sporadic and local epidemic of gastroenteritis.The scale of outbreaks and the crowd exposure in coastal areas and parts of inlands caused by Vibrio parahaemolyticus are rising,having ranked first in the microbial foodborne outbreaks.V.parahaemolyticus has been known to produce either thermostable direct hemolysin(TDH),TDH-related hemolysin(TRH),or both.The bacteria could be transmitted through seafood and freshwater products in food chains.The pathogenic mechanism of V.parahaemolyticus is not very clear,but some virulence genes have been confirmed.Moreover,pulse field gel electrophoresis,basing on the structure of the DNA in microbial identification,has more advantages on the typing ability,resolution,repeatability,comparability and sensitivity,compared to the traditional biochemical and serotyping not effectively for homology analysis.Therefore,in this study we investigated the distribution of virulence-associated genes of V.parahaemolyticus isolated in Zibo from 2013 to 2016.In order to deterimine genetic lineages and the source of V.parahaemolyticus isolated,PFGE typing was conducted,and analyzed the relationship between the PFGE subtypes and virulence-associated genes distribution characteristics,by which provided the scientific foundation for the early warning,monitoring and manipulation to prevent foodborne diseases caused by V.Parahaemolyticus.Objective: This study is to discuss the relationship of the target bacteria,analysis the regularty of epidemic of V.Parahaemolyticus in Zbio from 2013 to 2016.Methods: The characteristics of serotype distribution were discussed for the target bacteria.The TDH and TRH genes were tested by PCR and the homology of strain was detected by PFGE.Results: This study separated seven O antigen serotypes and the group O2 accounting for 29.41%.K antigen serotype has only 5 types and has no obvious trend.TDH carrying rate was 3.53% and TRH was 5.88%,TRH is higher than that of TDH.There are no relatives between separation strains carried virulence genes,and no obvious advantage zone type.Conclusion:(1)The Vibrio parahaemolyticus isolated in Zibo are mainly O2 group,K antigen was less identified.(2)The detection rates of virulence genes TDH and TRH were low,and only carried a single virulence gene.(3)The PFGE map of the two O2:K28 was different with each other.The others were also different and have lower similarity.The correlation between serotype and PFGE map of Vibrio parahaemolyticus was not obvious.They were far apart from each other.