Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2014
Publication Date: 4/1/2014
Publication URL: http://handle.nal.usda.gov/10113/58791
Citation: Xu, J., Song, M., Yang, P., Shi, C., Paoli, G., Shi, X. 2014. Phenotypic and genotypic antimicrobial resistance traits of foodborne Staphylococcus aureus isolates from Shanghai. Journal of Food Science. 79:635-642. Interpretive Summary: Staphylococcus aureus is an important human pathogen that can cause food poisoning or hospital acquired infections. Strains of Staphylococcus aureus that are resistant to antibiotics, particularly those resistant to methicillin (i.e, methicillin resistant Staphylococcus aureus; or MRSA), have become a particular concern. In this study, several strains of Staphylococcus aureus isolated from a variety of foods were studied to determine their resistance to several antibiotics. The presence of the specific genes responsible for the antibiotic resistance was also examined. Approximately 86% of the Staphylococcus aureus were resistant to at least one antibiotic, about 10% of the strains were MRSA, and about 41% of the strains were resistant to multiple antibiotics. The incidence of antibiotic resistance was significantly correlated to food type, with isolates from meat and raw milk more likely to be resistant to antibiotics than those from vegetables or frozen foods. The results underscore the association of antibiotic resistant bacteria with foods of animal origin and the importance of screening of those foods for Staphylococcus aureus and MRSA.
Technical Abstract: 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 (MRSA), 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 E-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 seventy-eight isolates could be subtyped into 31 resistance profiles and 11 clusters based on their antimicrobial susceptibility. Furthermore, 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%), gyrA (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.