Nasal methicillin-resistant staphylococcus aureus carriage in tertiary hospitals: Evidence of hospitalacquired transmission in Nigeria

Methicillin-resistant staphylococcus aureus (MRSA) nasal carriage is a significant source of infection and transmission in hospital environments. Effective infection control and antimicrobial stewardship are hampered in low-and middleincome countries by a lack of local monitoring data. This study investigated the prevalence, antimicrobial resistance pattern and genetic determinants of MRSA in patients and healthcare in two tertiary hospitals in Nigerian. A total 1, 309 nasal swabs specimens were collected from in-patients, healthcare workers and out-patients from two different tertiary hospitals. Staphylococcus aureus was identified and isolated using standard biochemical methods. The MRSA were phenotypically detected using Brilliance MRSA chromagar and cefoxitin and latter subjected to antimicrobial susceptibility testing following the standard Kirby–Bauer disk diffusion method. PCR-specific primers were used to screen for mecA and pvl genes in ten randomly selected MRSA. Out of the 1,309 nasal samples collected, 575 S. aureus representing 43.9% were isolated from the nasal samples of which 96 (17%) were MRSA, 81 from in-patients/out-patients and 15 from health care workers. The in-patients and doctors habour the highest number of MRSA, 73/81 and 8/15 respectively. All the MRSA isolates resistant to cefoxitin were also found to be resistant to tetracycline, amoxicillin, and amoxicillin-clavulanic acid. The mecA and pvl genes were detected in five of the isolates. However, pvl gene was detected in one isolate without corresponding detection of mecA gene. The high frequency of MRSA carriage among patients and healthcare personnel underscores the potential for hospital-acquired transmission and highlights the need for strengthened infection control and antibiotic stewardship in Nigerian tertiary hospitals.