Archive of SID Avicenna J Clin Microb Infec. 2016 November; 3(4):e39272. doi: 10.17795/ajcmi-39272. Published online 2016 August 22. Research Article Nasal Carriage of Methicillin-resistant Staphylococcus aureus among Elderly People in Lagos, Nigeria Solayide Abosede Adesida,1,* Abiola Olufunmilayo Okeyide,2 Adefunke Abioye,2 Ibilola Omolopo,2 Tenny Obiageli Egwuatu,1 Kehinde Olugbenga Amisu,3 and Akitoye Olusegun Coker2 1Department of Microbiology, Faculty of Sciences, University of Lagos, Nigeria 2Department of Medical Microbiology and Parasitology, College of Medicine, University of Lagos, Nigeria 3Department of Microbiology, Lagos State University, Apapa-Badagary Expressway, Ojo, Lagos, Nigeria *Corresponding author: Solayide Abosede Adesida, Department of Microbiology, Faculty of Sciences, University of Lagos, Akoka, Nigeria, E-mail: [email protected] Received 2016 May 23; Revised 2016 July 29; Accepted 2016 August 14. 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 proce- dures. 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 mul- tidrug resistance was common. Approximately 20% were resistant to gentamicin, ofloxacin, and mupirocin. Cloxacillin, amoxi- cillin/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, hyper- tension, 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 implemen- tation of measures to prevent the spread of this organism are necessary. Keywords: Antibiotic Resistance, Colonization, Elderly, Risk Factors, Staphylococcus aureus 1. Background with high requirements for healthcare and frequent con- tact with the general community. Thus, they are at risk Staphylococcus aureus is one of the commonest human of being colonized with different microorganisms, includ- pathogens, capable of causing a wide range of infections ing S. aureus, and may be source of transmission of this in susceptible hosts in communities and hospitals (1). The bacterium from the hospital environment to the commu- anterior nares are the principal niche of this organism, nity. Among the elderly, S. aureus has been implicated as from whence endogenous infections can occur. A previ- the cause of bacteremia, endocarditis, pneumonia, septic ous study demonstrated that S. aureus blood isolates from arthritis, and vertebral osteomyelitis (3,4). septicemic patients were clonally indistinguishable from those obtained from nasal specimens in approximately Infections associated with S. aureus are often compli- 82% of patients (2), thereby confirming the association cated by the remarkable ability of this pathogen to become between S. aureus nasal carriage and infection. Asymp- resistant to various classes of antibiotics and to become tomatic S. aureus carriers may transfer the organism to more virulent (5). MRSA has been a persistent pathogen in other members of the community or to susceptible per- hospitals but its changing epidemiological trend became sons, especially those with poor functional status, such as apparent in the 1990s (6). These strains are resistant to a the elderly. The elderly represent a heterogeneous group wide range of antimicrobials due to a penicillin-binding Copyright © 2016, Hamadan University of Medical Sciences. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited. www.SID.ir Archive of SID Adesida SA et al. protein (PBP2a) encoded for by the mecA gene (7). Methi- would likely be important reservoirs of S. aureus with re- cillin resistance in S. aureus is detectable phenotypically spect to antimicrobial resistance. and genotypically, and cefoxitin disk diffusion and chro- mogenic agar provide reliable evidence for the identifica- tion of S. aureus strains (8,9). 2. Objectives Presently, the proportion of nasal S. aureus isolates identified as methicillin-resistant has increased with vari- Our primary objective was to determine the nasal S. au- able prevalence data, ranging from Indian figures of 29% in reus carriage rates among elderly individuals in two hospi- preschool children (10) to 2.8% - 21.6% in long-term care fa- tals and a nursing home in Nigeria. The probable risk fac- cilities in Hong Kong (11), with an overall prevalence of 21% tors for nasal carriage were described and the prevalence among healthy individuals in urban and rural communi- of MSSA and MRSA and their antibiotic susceptibility pat- ties in Ghana (12). Undoubtedly, MRSA is not simply replac- terns were estimated. ing methicillin-susceptible S. aureus (MSSA) as a causative agent of infections, but is causing an escalation in the inci- dence of S. aureus infections, thereby adding to the disease 3. Methods burden. As in most other countries, staphylococcal infec- tions have been a major clinical and epidemiological prob- 3.1. Study Population and Approval lem in hospitals in Nigeria. MRSA was first noticed in the late 1980s (13). Subsequent data from a number of Nigerian The study was performed among outpatient adult pop- hospitals revealed that approximately 20% - 52% of individ- ulations in two general hospitals and residents of a nurs- uals were either colonized or infected with this pathogen ing home in Lagos, Nigeria, from May to September 2013. (14, 15). MRSA-associated colonization has been described The study population comprised males and females aged mostly in immunocompetent individuals (16, 17), but colo- 65 years and above. The project proposal was approved nization of hospitalized and/or immunocompromised pa- by the ethics and research grants committee, College tients (18, 19) may lead to invasive infections with possi- of Medicine of the University of Lagos (reference num- ble unfavorable outcomes as a result of the battery of vir- ber: CM/COM/08/VOL.XXIV). The hospitals and the nurs- ulence factors possessed by the organism (20, 21). These in- ing home management provided permission for the use of fections can impose a significant economic burden on in- their centers. Verbal informed consent was obtained from dividuals and society. all participants after the study was explained to them. Research evidences from other countries have also ad- dressed the problem of S. aureus carriage in elderly pa- 3.2. Data Collection tients in institutional settings or in residents of nursing homes and long-term care facilities (11, 22-24). A report Several potential risk factors were investigated, using on the impact of S. aureus carriage among elderly patients a well-structured questionnaire. These included the com- with end-stage renal disease in Saudi Arabia revealed se- mon demographic variables of age, gender, and marital rious complications and a prevalence of 38.05% (78/205) status. We evaluated the relationship between S. aureus car- for S. aureus nasal carriage; of these strains, 27.3% (56/205) riage and self-reported health status or a clinical diagno- were MSSA and 10.7% (22/205) were MRSA (22). MRSA car- sis of conditions such as hypertension, diabetes mellitus, riage in the elderly was significantly correlated with the arthritis, and pulmonary infections. The use of antibiotics presence of skin lesions, prior hospitalization within the in the preceding three months was also examined. previous six months, and antibiotic exposure within the previous six months. Although some studies in Nigeria 3.3. Sample Collection have evaluated the staphylococcal carriage rate among cer- tain vulnerable groups (19) and young adults (16), a sub- Nasal specimens were collected from the participants stantial proportion of data generated on S. aureus epidemi- using sterile cotton wool swabs. The swab-stick was in- ology are restricted to invasive infections (25, 26) and the serted into both nostrils to carefully sample the mucosa problem of S. aureus carriage is less defined in the elderly. of the nasal septum adjacent to the nasal ostium, which is Since the burden of S. aureus carriage could be driven by the preferred habitat of S. aureus (29). The sterile