Contamination status and characteristics of Staphylococcus aureus in ready-to-eat foods in Guangzhou from 2009 to 2018

ObjectiveTo investigate the prevalence, antimicrobial susceptibility, and enterotoxin gene of Staphylococcus aureus (S. aureus) isolates in ready-to-eat (RTE) foods in Guangzhou from 2008 to 2019.MethodsRTE food samples were randomly collected from retail outlets and supermarkets in 11 districts of Guangzhou and the isolation and identification of S. aureus were performed. All isolated S. aureus were tested for antimicrobial susceptibility, enterotoxin genes and multilocus sequence typing (MLST). Methicillin resistant S. aureus (MRSA) isolates were further characterized by staphylococcal cassette chromosome mec (SCCmec) typing.ResultsA total of 157 S. aureus isolates(11.22%) were detected from 1 399 RTE food samples in Guangzhou from 2009 to 2018. The prevalence of S. aureus in cooked pork samples was significantly higher than those in non-meat samples (17.95% vs 9.43%, P<0.001). Of the 157 S. aureus isolates, seven were confirmed as MRSA by cefoxitin disc diffusion test. Among the 157 isolates, the highest resistance was to penicillin G (83.43%), followed by tetracycline (55.41%), erythromycin (41.40%), chloramphenicol (29.30%), clindamycin (21.02%), trimethoprim/sulphamethoxazole (20.40%) and gentamicin (14.01%), and 4.46%-10.83% isolates were resistant to cefoxitin, oxacillin and ciprofloxacin. All the isolates were sensitive to vancomycin, daptomycin and linezolid. Notably, 82.5% and 100% isolates were resistant to at least three antimicrobials in CC59 and CC398, respectively, and the resistance levels were significantly higher than that of CC6 isolates (14.81%) (P<0.001). The positive rates of seg, sei, sem, sen, seo and seu in CC6 and CC59 isolates were 100% and 42%, respectively (P<0.001).ConclusionCC59, CC6 and CC398 were the predominant S. aureus isolates in RTE food samples in Guangzhou, and these isolates had been linked to human infections and Staphylococcal food poisoning outbreaks in China. It was a serious public health risk and highlights the need to implement good hygiene practices.