METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS FROM READY-TO-EAT FOODS IN A HOSPITAL CANTEEN, SOUTHERN THAILAND: VIRULENCE CHARACTERIZATION AND GENETIC RELATIONSHIP

Due to the existence of sporadic cases caused by methicillin-resistant Staphylococcus aureus (MRSA) in Songklanagarind Hospital, Songkhla, southern Thailand where a canteen is located in close vicinity, this study investigated the presence of MRSA, including mecA-carrying S. aureus (MCSA), contamination in 105 ready-to-eat (RTE) food samples sold in this canteen. Coagulase-negative MRSA (MR-CoN) and coagulase-negative MCSA (MCSA-CoN) contaminations were observed in various RTE foods with unriped-papaya salad having significantly highest incidence of MCSA-CoN contamination (p < 0.05). The majority of MCSA-CoN isolates were resistant to clindamycin and fusidic acid. Two MCSA-CoN strains PSU172 and PSU180 were subsequently shown to be MR-CoN. Staphy- lococcal enterotoxins (SEs)-carrying MCSA-CoN strain PSU109 was isolated from seasoned rice. The SE-carrying MCSA-CoN strain PSU109, MR-CoN strain PSU172 and MCSA-CoN strain PSU173 were able to survive in the acidic unriped-papaya salad sauce (pH 4.0-4.5) for up to 6 hours. Typing by pulsed-field gel electrophoresis revealed 80% genetic relatedness among MCSA-CoN strains from RTE food and clinical strains. This study suggests the plausibility of RTE foods sold in a hospital canteen as vehicles of hospital-acquired MR-CoN and of MCSA-CoN.