Methicillin- and vancomycin-resistant Staphylococcus aureus in chicken carcasses, ready-to-eat chicken meat sandwiches, and buffalo milk

Methicillin-resistant Staphylococcus aureus (MRSA) is a growing public health concern; however, there is limited information about MRSA and VRSA (Vancomycin-resistant S. aureus) among animal-origin food. Therefore, this study intended to elucidate the prevalence, enterotoxin existence, antimicrobial resistance profiles, and antimicrobial resistance genes of S. aureus strains isolated from chicken carcasses, ready-to-eat (RTE) chicken meat sandwiches, and buffalo milk samples marketed in Mansoura City, Egypt. Of the 240 samples examined, 52.1 % were contaminated with S. aureus, with a mean count of 4.11 log₁₀ CFU/g. A total of 250 isolates were verified as S. aureus by PCR targeting nuc gene, of which 39.2 % (98/250) harbored at least one S. aureus enterotoxin (SE) gene. The predominant SE genes were sea (61.2 %, 60/98), followed by sed (58.2 %, 57/98), sec (38.8 %, 38/98), and seb (27.6 %, 27/98). All isolates were resistant to at least one antimicrobial, with an average MAR (multiple antibiotic resistance) index of 0.530. Four isolates exhibited resistance to all antimicrobial agents tested. Interestingly, 100 %, 76.4 %, 35.6 %, 30.8, 10.4 %, 6 %, and 1.6 % of isolates were resistant to penicillin, azithromycin, oxacillin, ceftaroline, vancomycin, linezolid, and daptomycin, respectively. Of the 250 S. aureus strains tested, 38 % were confirmed as MRSA by mecA gene, while 10.4 % were identified as VRSA by vanA gene. The high prevalence of MRSA and VRSA isolates among samples tested is worrisome. Hence, monitoring antimicrobial usage in veterinary medicine and applying strict hygienic measures during food handling and processing is imperative to prevent the spread of such resistant bacteria and protect public health.