Pathogenic characteristics of Staphylococcus aureus isolates from a foodborne disease outbreak in Zhuhai City in August, 2021

Abstract

ObjectiveTo characterize the pathogenic characteristics and homology of Staphylococcus aureus （SA） isolated from a foodborne outbreak.MethodsA selection medium was applied to culture the possible infectious agent according to national standard methods， and the micro broth dilution method was applied to determined the isolate’s sensitivity to 16 drugs. Whole genome sequencing and bioinformatics analysis were employed to investigate the isolates’ molecular genetic characteristics and homology.ResultsA total of 16 SA strains were isolated in this outbreak， including eight strains isolated from patients， one from the kitchen worker， and seven from food. MLST and Spa typing analysis identified five distinct types in this outbreak， namely ST7-t91， ST5-t548， ST398-t588 and ST965-t62， in which the ST7-t91 and ST5-t548 types account for strains from humans； All ST7 isolates were resistant to tetracycline and penicillin， carrying resistance genes aadD， tet （K）， blaZ， and lnu （A） respectively， while the ST5 strain was sensitive to all tested antibiotics； cgMLST analysis revealed that the difference of these ST7 strains was less than three loci. Gene annotation revealed that ST7 strains contained the sea， chp， scn， and sak virulence genes， while ST5 possessed chp， scn， sak， seg， selk， selm， selo， and seln genes.ConclusionThis outbreak was caused by mixed infections of multiple ST types of SA， with ST7-t91 as the predominant type， and this clone present a high pathogenicity and was sensitive to somefirst-line clinical antibiotics tested，such as cephalosporins and quinolones.

Keywords

• foodborne outbreak
• staphylococcus aureus
• whole genome sequencing
• cgmlst
• enterotoxin