Isolation and Identification of Methicillin Resistant Staphylococcus aureus (MRSA) Associated with Infected Wounds

Methicillin-resistant Staphylococcus aureus (MRSA) is an important multidrug-resistant pathogen associated with wound infections and poses a significant challenge to effective antimicrobial therapy. This study was conducted to isolate and identify Staphylococcus aureus and determine the occurrence of methicillin-resistant strains among infected wound patients in Gusau, Zamfara State, Nigeria. A total of 150 wound abscess samples were collected and processed using standard microbiological techniques. Samples were cultured on nutrient agar and Mannitol Salt Agar, while presumptive S. aureus isolates were identified based standard microbiological techniques. Antimicrobial susceptibility testing was performed using the Kirby–Bauer disc diffusion method against oxacillin, vancomycin, tetracycline, levofloxacin and cotrimoxazole. Multidrug-resistant (MDR) isolates were further screened for methicillin resistance using a 30 µg cefoxitin disc. Molecular detection of the mecA resistance gene was carried out using polymerase chain reaction (PCR), followed by agarose gel electrophoresis. The results showed that 54 (36.0%) of the 150 samples yielded presumptive S. aureus. Of the 41 isolates subjected to antimicrobial susceptibility testing, resistance was highest to cotrimoxazole (70.7%), followed by vancomycin (65.9%), tetracycline (61.0%) and oxacillin (56.1%), while levofloxacin demonstrated the highest susceptibility (87.8%). Twenty-five (61.0%) isolates were classified as multidrug resistant. Among these MDR isolates, 7 (28.0%) were resistant to cefoxitin and were classified as MRSA. Molecular analysis demonstrated the presence of the mecA gene in six tested samples, with the expected amplicon observed at approximately 265 bp. It is concluded that the detection of the mecA gene further confirms the genetic basis of methicillin resistance in the identified isolates.