Prevalence, risk factors and multidrug resistance of community-associated methicillin-resistant Staphylococcus aureus nasal carriage among healthy individuals in Ibadan, Nigeria

Abstract

Nasal carriage of Community-Acquired Methicillin-resistant Staphylococcus aureus (CA-MRSA) is recognised for its rapid community spread and tendency to cause various infections especially in communities with large populations and poor personal hygiene. The study investigated the prevalence and antimicrobial-resistance profile of CA-MRSA and evaluated possible risk factors among the healthy population. Using a multi-stage sampling technique, nasal swabs were collected from 700 apparently healthy residents of Ibadan during a 9-month period. All nasal swab samples were cultured on Mannitol Salt agar and Blood Agar. The recovered isolates were identified using standard biochemical tests and the Microbact™ Staphylococcal 12 S kit. Polymerase chain reaction was carried out to further characterise the isolates; the 16 S rRNA gene was used as a genus-level marker, while detection of the nuc gene was used to confirm Staphylococcus aureus. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disc diffusion method following the CLSI guidelines. Vancomycin susceptibility was determined using broth microdilution as described by EUCAST. Methicillin resistance was confirmed phenotypically by cefoxitin disc diffusion and genotypically by detection of the mecA gene. Of the 700 participants screened (392 males, 308 females), a total of 223 (31.9%) S. aureus isolates were recovered, of which 66 (9.4%) were confirmed MRSA. Low educational background (p˂0.001), age group > 40–50 years (p = 0.003), recent antibiotics use (p = 0.006), recent hospital visits (p = 0.003) and male gender (p = 0.002) were significantly associated with CA-MRSA carriage. All MRSA isolates harboured the mecA gene and exhibited high multidrug resistance, particularly to clindamycin (62%) and cotrimoxazole (59%). The study established a relatively high prevalence and resistance burden of CA-MRSA in the population. This poses a serious public health concern in the region and necessitates continuous surveillance on the colonization state of CA-MRSA. Not applicable.