Staphylococcus aureus in animal-derived food products: the prevalence, virulence, enterotoxin-encoding genes, antibiotic resistance and PFGE profiles in northern Turkey

The aim of this research was to investigate the prevalence of Staphylococcus aureus (S. aureus) in raw milk, Tulum cheese, and ground beef samples, and to determine their virulence, enterotoxins, antibiotic resistance, and genetic relatedness. A total of 300 food samples were purchased from public markets within different districts of Giresun, Turkey. Fifty-two (17.3%) of these food samples tested positive for S. aureus isolation. Fifty-two S. aureus isolates were further analyzed for the presence of virulence genes. The virulence genes detected were icaA (9.6%) and icaD (84.6%). Enterotoxin-encoding genes of the sea, seb, sec, sed, see, seg, seh, sei, sej, sek, sel, sem, sen, seo, seq, ser, and seu groups were detected individually or in combination. Of the 52 S. aureus isolates, 1 methicillin-resistant S. aureus strain (1.9%) was isolated as having the mecA. The antibiotic susceptibility test of positive isolates showed resistance to cefoxitin (1.92%), tetracycline (11.5%), erythromycin (3.84%), ciprofloxacin (1.92%), gentamicin (1.92%), and fusidic acid (5.76%). Pulsed -field gel electrophoresis (PFGE) of the 52 isolates revealed 46 PFGE types, with 21 (40.3%) isolates grouped into 7 clusters. Some of the isolates from different districts showed clonal relatedness. The high occurrence of S. aureus strains in these products indicated a potential risk to humans. The results of this study indicated that dairy and meat products could be reservoirs of S. aureus strains that harbor several virulence factors and enterotoxin genes and the presence of these bacteria in foods may be a cause of concern for human health from food poisoning; therefore, hygienic measures and periodic bacteriological controls are necessary in all areas that provide these foods to the public, such as bazaars and butchers, to reduce contamination with foodborne pathogens.