CHARACTERIZATION OF STAPHYLOCOCCUS SPP FROM MEAT AND READY-TO-EAT FOOD, HAT YAI CITY, SONGKHLA, THAILAND

Staphylococcus aureus contamination in food is considered important for food safety as its virulence factors are able to cause illnesses in humans. Screening of 100 meat and 30 ready-to-eat (RTE) food samples from open markets, Hat Yai city, Songkhla Province, Thailand during June 2015 to January 2017 revealed 11 samples contaminated with 27 methicillin-susceptible S. aureus (MSSA) isolates, of which 52% and 67% carried spa and femB, respectively, with only a minority (3 and 4 strains) carrying sec and vWbp, respectively. Staphyloxanthin production on tryptic soy agar was observed in 7 strains but not auto-aggregation. All but two strains were resistant to tetracycline, the exception being strains resistant to both tetracycline and gentamicin and another sensitive to all 8 antimicrobial agents tested. Biofilm formation using crystal violet binding assay showed an average biofilm formation for all strains ranging from. A(570) nm 0.35 (strain PSN-27) to 3.08 (strain PSN-4) (p < 0.05). Virulence as determined by a whole-blood phagocytosis assay demonstrated that bacterial number after incubated in whole blood varied from-0.5 fold to 82 folds comparing to their controls. In addition, one strain each of mecA(+) S. epidermidis and S. haemolyticus, is capable of producing yellow pigment, high biofilm formation, and of auto-aggregation, were isolated from RTE foods. These staphylococci have the potential to cause illness in humans and should be included in any survey of bacterial contamination in foods.