Characterization of antibiotic resistant Staphylococcus aureus isolates from ready-to-eat foods in Korea

Heat-stable enterotoxins and coagulase type are the most notable virulence factors associated with Staphylococcus aureus, a common pathogen associated with serious community- and hospital-acquired disease. Thus enterotoxin gene profiles and the PFGE or coagulase patterns of antibiotic resistant S. aureus isolates from ready-to-eat foods in Korea were examined. Among 154 S. aureus isolates, antibiotic resistance to penicillin, gentamicin and tetracycline were 81.2% (125/154), 11.0% (17/154) and 11.7% (18/154), respectively. None of the strains were resistant to vancomycin. Two of three oxacillin-resistant strains were resistant to cephalothin and were mecA positive. Furthermore, 104 of 139 S. aureus isolates contained staphylococcal enterotoxin (SE) genes, and 13.5% of the SE strains were resistant to erythromycin and gentamicin. One oxacillin-resistant isolate had a pattern similar to NRS 123 (SCCmec IVa) according to pulsed-field gel electrophoresis (PFGE) using SmaI. Based on coagulase isotyping, type IV and VII were the most predominant, accounting for 30.9%, respectively. Coagulase type IV harbored the sea gene or the seg-sei-tst gene combination, and all of the type VII strains had the seh toxin gene. These data indicate that the enterotoxin gene profile correlates to coagulase type or antimicrobial resistance and can be used as a practical database for epidemiological purposes.