Survey of a foodborne outbreak caused by multi type Vibrio parahaemolyticus

Objective To understand the etiological characteristics of a foodborne outbreak caused by Vibrio parahaemolyticus. Methods A suspected foodborne disease outbreak occurred in a township of Guangxi Zhuang autonomous region in September 2017. Thirteen anal swabs were collected from the patients for the pathogen isolation in field survey and 10 V. parahaemolyticus strains were isolated. O and K diagnosis sera were used for the subtyping of the strains in slide agglutination test. Taqman fluorescent PCR was conducted to detect the four toxic gene(tlh,tdh,trh and ORF8)of V. parahaemolyticus. The clustering analysis was performed with software Bionumerics 6.6 after pulsed field gel electrophoresis(PFGE)with restriction endonuclease Not Ⅰ and Sfi Ⅰ respectively. Results The 10 V. parahaemolyticus isolates belonged to 5 serotypes. Among them,6 were O3:K6 strains,and the other 4 were O4:K8,O1:KUT,O2:KUT and O10:K19 strains respectively. All the strains were positive for tlh gene and negative for trh gene. Six O3:K6 strains and one O4:K8 strain were tdh gene positive,the other strains were tdh gene negative. Clustering analysis indicated that the strains had 8 molecular types of PFGE after restriction with enzyme Not Ⅰ and Sfi Ⅰ respectively. And six O3:K6 strains could be divided into 4 PFGE patterns. Comprehensive analysis of the 3 indicators showed that only 2 V. parahaemolyticus strains among the 10 isolates had the same serotype,toxic gene and PFGE pattern. Conclusion The outbreak was caused by pathogenic or non-pathogenic V. parahaemolyticus with different serotypes and PFGE patterns.