ABSTRACT
Methicillin-resistant Staphylococcus aureus is recognized as one of the major causes of infections in humans, occurring in both the community and the hospital settings. Colonizing strains may serve as endogenous reservoirs for overt clinical infections or may spread to other patients. Periodic surveillance remains a key component of MRSA infection control both in the hospital and the community setting. This research was therefore, carried out to determine the prevalence and antibiotic susceptibility pattern of methicillin-resistant Staphylococcus aureus (MRSA) isolated from both hospital and non-hospital subjects.
Nasal swab samples were collected from a hundred and ten (110) persons, 55- hospital samples and 55-non-hospital samples. Each nasal swab sample was inoculated into peptone water which was then streaked aseptically on already cooled mannitol salt agar plates and incubated at 37°C for 24-48 hr. Colonies that were golden-yellow in appearance and fermented mannitol salt agar were then subcultured on nutrient agar plates to obtain a pure culture of isolates and then incubated at 37°C for 24 hr. Staphylococcus aureus isolates were identified by standard bacteriological procedures based on their cultural, morphological and biochemical characteristics. Methicillin-resistant test was carried out using the oxacillin disc diffusion method. S. aureus isolates were then tested for susceptibility to ten commonly used antibiotics: pefloxacin 10 µg, gentamycin 10 µg, ampiclox 30 µg, zinnacef 20 µg, amoxicillin 30 µg, rocephin 25 µg, ciprofloxacin 10 µg, septrin 30 µg, streptomycin 30 µg and erythromycin 10 µg:using the Kirby-Bauer disc diffusion method.
A total of 110 samples were collected, out of which 14(12.7%) were identified and confirmed as S. aureus,while 10(9.1%) were methicillin-resistant Staphylococcus aureus (MRSA) and 4(3.6%) were methicillin-sensitive Staphylococcus aureus (MSSA). Of the S. aureus isolated from hospital subjects, 7 (87.5%) were MRSA, while that from non-hospital subjects, 3 (50%) were MRSA. The overall prevalence of MRSA in S. aureus isolates was 71.4%. The nasal carriage rate of MRSA isolates in the study population was 8 (12.5%) for males and 2 (4.3%) for females. The MRSA isolates varied in their antibiotic susceptibility pattern when tested for their sensitivity to 10 commonly used antibiotics. All the MRSA isolates showed 100% sensitivity to pefloxacin and 100% resistance to zinacef. The MRSA isolates from non-hospital subjects showed 100% sensitivity to pefloxacin, gentamycin, rocephin, ciprofloxacin, streptomycin, and erythromycin and 100% resistance to ampiclox, zinacef and amoxicillin. The MRSA isolates from hospital subjects showed 100% sensitivity to pefloxacin and 100% resistance to zinacef. The findings of this study has shed epidemiological light on MRSA colonization level among hospital and non-hospital subjects, efforts should therefore be put in place to stem the tide of MRSA and chemotherapy should be guided by sensitivity of the probable causative organism.
