Methicillin and Inducible Clindamycin-resistant Staphylococcus aureus Isolates from Clinical Samples in Abia State

Abstract

Staphylococcus aureus is a major bacterial pathogen that causes different community and hospital-acquired infections. S. aureus resistant to methicillin has become a big and expanding problem of concern in many developing countries. Clindamycin has also been discovered to be a preferred therapeutic alternative for the treatment of both methicillin susceptible and resistant staphylococcal infections. This study examined the prevalence of Methicillin-resistant Staphylococcus aureus (MRSA) in clinical samples of patients in Abia state, Nigeria using standard recommended procedures. A total of 750 clinical specimens of blood and urine samples, wound, ear, nasal, high vaginal and ear swabs were collected from three major health facilities in Abia state, Nigeria. Each sample was cultured for bacterial isolates and examined for colonial and cellular morphology while biochemical identification was performed. Antimicrobial susceptibility test was performed on Mueller-Hinton agar (MHA) by disc diffusion method and MRSA screening was done using cefoxitin disc.  A total of 265 (35.3%) S. aureus isolates were recovered, out of which 126(47.5%) were from males and 139(52.5%) were from females, however there was no association between the prevalence and gender (p-value = 0.05) and also prevalence and age (p-value = 0.52). Of the 265 S. aureus isolates recovered, 164(61.9%) were MRSA. All 100% of the MRSA were susceptible to vancomycin, 120(73.2%) to clindamycin, 92(56.1%) to gentamycin. All 100% were resistant to ceftazidine, 157(95.7%) to cloxacillin, 146(89.0%) to augmentin, 136(82.9%) to ceftriaxone and 103(61.6%) to erythromycin. The MRSA strains showed much higher resistance rate than their MSSA counterparts to all tested antibiotic except clindamycin. 64(39.0%) of the MRSA were resistant to 4 classes of antibiotics indicating multi drug resistance (MDR). The overall prevalence of inducible clindamycin resistance among methicillin resistant isolates was 29(17.7%). This implies that 17.7% could have been misidentified as clindamycin susceptible by Kirby-Bauer disk diffusion method. In conclusion prevalence of MRSA was high and it is important to routinely carry out the D-test for detection of inducible clindamycin resistance if clindamycin is considered as a treatment option.