Nasal Carriage of Methicillin-resistant Staphylococcus aureus among Elderly People in Lagos, Nigeria

Abstract

Objectives: Staphylococcus aureus is a lethal opportunistic pathogen capable of causing a wide range of infections, especially in debilitated hosts such as the elderly. Nasal carriers of this organism have an increased risk of becoming infected with the pathogen. The purpose of this study was to assess the prevalence of S. aureus nasal carriage, to determine the probable risk factors, and to examine the frequency of methicillin-resistant S. aureus (MRSA) among elderly people in hospital and nursing home settings in Lagos, Nigeria. Methods: Two hundred thirty nasal samples were collected from the anterior nares of individuals aged 65 years and older. Possible risk factors were assessed using well-structured questionnaires, and the samples were subjected to standard bacteriological procedures. Antibiotic susceptibility of the isolates was determined with the disk diffusion method. Detection of methicillin resistance was done with the disk diffusion test using cefoxitin 30 µg, and confirmed with OXOID MRSA CHROMagar. Results: Fifty (21.7%) S. aureus strains were identified among the samples, and antibiotic susceptibility testing showed that multidrug resistance was common. Approximately 20% were resistant to gentamicin, ofloxacin, and mupirocin. Cloxacillin, amoxicillin/clavulanate, and ceftazidime showed the least anti-staphylococcal activity, and almost half of the isolates were resistant to ceftriaxone and cefuroxime. The MRSA nasal carriage rate was 10% and colonization was favored by previous antibiotic use, hypertension, and tuberculosis. Conclusions: The occurrence of multidrug-resistant S. aureus in the elderly cohort indicates their capacity to serve as reservoirs for these strains, which could facilitate the dissemination of MRSA into the community. Therefore, decolonization and the implementation of measures to prevent the spread of this organism are necessary.