Genetic Basis of Multiple Drug Resistance in Staphylococcus aureus Isolates from Hospitals in Cross River State

Methicillin-resistant Staphylococcus aureus (MRSA) and multiply drug-resistant S. aureus strains represent critical nosocomial pathogens in Nigerian healthcare settings. The genetic mechanisms underlying drug resistance, particularly the mecA gene and plasmid-encoded resistance determinants, are important targets for surveillance. This study characterised the drug resistance profile and genetic basis of resistance in S. aureus isolates collected from clinical specimens at two tertiary hospitals in Cross River State, South South Nigeria. One hundred and twenty S. aureus isolates from wound swabs, blood cultures, and nasal swabs were subjected to standard antimicrobial susceptibility testing using the Kirby-Bauer disc diffusion method. PCR amplification was used to detect the mecA gene, tetracycline resistance tet(K), and erythromycin resistance erm(C) genes. Sixty percent of isolates were classified as MRSA based on cefoxitin disc testing confirmed by mecA PCR. Multiple resistance gene co-occurrence was common, particularly mecA and tet(K). These findings raise serious infection control concerns for hospitals in Cross River State and argue for rapid molecular diagnostics and an antimicrobial stewardship programme. Keywords: MRSA, mecA gene, drug resistance, Staphylococcus aureus, Cross River State