Abstract:
Objective To understand the pathogens of a foodborne outbreak in Huzhou, Zhejiang province, in 2023, and identify the cause of this outbreak.
Methods Multiple enteropathogens were detected by FilmArray, and the pathogen was subsequently isolated and cultured by using anal swabs, stool samples and smears. The isolated strains were identified by using VITEK Mass Spectrometry, and antimicrobial susceptibility test, pulsed-field gel electrophoresis (PFGE) molecular typing, and whole genome sequencing (WGS) were performed for the isolates of V. parahaemolyticus. Gene annotation and sequence alignment were used to analyze the virulence genes and drug resistance genes of the strains. A phylogenetic tree was constructed based on single nucleotide polymorphism (SNP), and homology analysis was conducted to trace the origin of the pathogens.
Results A total of 8 strains of V. parahaemolyticus were isolated from the cases. Two serotypes, O10: K4 and O3: K6, were detected in the 8 strains, and the strains with same serotype had same PFGE pattern. All the 8 strains were resistant to cefazolin and carried same resistance gene. Less than 9 SNP variation loci were detected in the strains with same serotype. The phylogenetic tree based on SNP showed that the strains with same serotype were homologous.
Conclusion This foodborne disease outbreak was caused by V. parahaemolyticus. WGS can be used as a complementary method to PFGE for epidemiological investigations of disease outbreaks.
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