Prevalence of clindamycin inducible resistance among methicillin-resistant Staphylococcus aureus at Bugando Medical Centre, Mwanza, Tanzania

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) has been recognized world wide as an important causative agent of nosocomial and community acquired infections. Clindamycin has been considered as an alternative drug for the treatment of such strains. However, the possibility of clindamycin inducible resistance complicates the choice of treatment. The aim of this study was to determine the prevalence of clindamycin inducible resistance of MRSA at Bugando Medical Centre (BMC) in Mwanza Tanzania. A total of 600 clinical specimens of pus, wound swabs and aspirates from patients admitted at BMC surgical wards were processed over a period of 4 months. Of these, 160 of S. aureus clinical isolates were analysed. MRSA was identified using cefoxitin disc, oxacillin disc and oxacillin agar. Inducible clindamycin resistance was detected using erythromycin (15µg) and clindamycin (2µg) discs placed 15mm apart on Muller Hinton agar. Of the 160 isolates, 26 (16.3%) were found to be MRSA. Overall prevalence of inducible clindamycin resistance (iMLS B) was 28.8% (46/160), with 22% (30/134) of methicillin-susceptible S. aureus (MSSA) and 61% (16/26) of MRSA exhibiting inducible clindamycin resistance (P=0.0001). Constitutive resistance (cMLS B) was found in 1 (3.7%) of the MRSA isolates and was not detected among MSSA. MS B phenotype was detected in 1 (3.8%) of MRSA isolates and 2 (1.5%) of MSSA. Eight (29.6%) of the MRSA isolates were sensitive to both clindamycin and erythromycin. In conclusion, a high prevalence of inducible clindamycin resistance was observed among S. aureus with significant association between MRSA and inducible clindamycin resistance. It is important that susceptibility test of staphylococci is routinely done to facilitate early detection of clindamycin inducible resistance in the country. ________________________________________________________________________________________________