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Phenotypic and genotypic antimicrobial resistance traits of foodborne Staphylococcus aureus isolates from Shanghai

Jie Xu, Chunlei Shi, Minhui Song, Xuebin Xu, Puyu Yang, George Paoli, Xianming Shi
Journal of food science 2014 v.79 no.4 pp. 635-642
Staphylococcus aureus, raw milk, cross infection, genes, vancomycin, genetic resistance, phenotype, clindamycin, genotype, screening, humans, meat, polymerase chain reaction, human food chain, antibiotic resistance, food availability, food pathogens, foodborne illness, benzylpenicillin, vegetables, erythromycin, supply chain, frozen foods, China
Staphylococcus aureus is a recognized pathogen in humans, which causes nosocomial infections and food poisoning. The transmission of antibiotic resistant S. aureus (ARSA), especially methicillin-resistant S. aureus, between food products and humans has become a serious problem. Hence, it is necessary to monitor S. aureus through the food supply chain. In this study, the disk diffusion method and epsilometer test were performed to determine the prevalence of ARSA in 78 foodborne isolates using 18 antibiotics. The highest resistance frequency was found for penicillin G(74.4%),followed by erythromycin (59.0%) and clindamycin (44.9%), whereas no vancomycin-resistant isolates were found. The 78 isolates could be subtyped into 31 resistance profiles and 11 clusters based on their antimicrobial susceptibility. Furthermore, Polymerase chain reaction (PCR) screening for the presence of 13 genes conferring antibiotic resistance was conducted. The presence of resistance genes was relatively high: blaTEM (80.8%), ermB (41.0%), grlA (38.5%), ermC (35.9%), and aac6’/aph2” (35.9%). The incidence of antibiotic resistance was significantly correlated to food types (p = 0.018), with isolates from meat and raw milk more resistant to antibiotics than those from frozen food and vegetables.