Traceability analysis of a Staphylococcus aureus food poisoning incident based on whole-genome sequencing

ObjectiveTo perform molecular typing and traceability analysis on samples from a food poisoning incident caused by Staphylococcus aureus at a school in Boluo County， Huizhou City， and to provide guidance for future management and judgment of similiar epidemic events.MethodsSuspected samples were collected， and Staphylococcus aureus was identified using a VITEK MS mass spectrometer. Enzyme-linked immunosorbent assay （ELISA） was used to detect enterotoxin types. Whole-genome sequencing （WGS） was employed to identify resistance and virulence genes， and to perform multilocus sequence typing （MLST） and whole-genome single-nucleotide polymorphism （wgSNP） analysis. A phylogenetic tree was constructed to trace the origin of the pathogen.ResultsA total of 10 Staphylococcus aureus strains were isolated， including 6 from anal swabs， 3 from vomitus， and 1 from chicken steak. ELISA testing revealed that 8 patient-derived strains and 1 food-derived strain produced type A enterotoxin， while 1 patient-derived strain produced type B enterotoxin. The 9 strains producing type A enterotoxin were all ST6， and the 1 strain producing type B enterotoxin was ST338. The ST6 strains carried multiple resistance genes， and all harbored the enterotoxin A gene （sea） and several hemolysin genes. The ST338 strain carried the enterotoxin B gene （seb）. Phylogenetic analysis showed that the ST6 patient-derived strains and the food-derived strain belonged to the same cluster， with SNP differences ranging from 0 to 14.ConclusionThis food poisoning incident was caused by ST6 S. aureus contaminating the chicken steak. This study provides important data support for the prevention and control of foodborne diseases.