A Study of Inducible Clindamycin Resistance among Staphylococcus aureus Skin and Soft Tissue Infections in A Tertiary Care Hospital

Objectives: Drug resistant phenotypes like MRSA are difficult to treat requiring higher group of antibiotics. Topical agents like clindamycin can be used for the therapy of MRSA. The knowledge of prevalence of inducible clindamycin resistance phenotype is essential to prevent treatment failure. Methods : A total of 204 staphylococcal isolates obtained from skin and soft tissue infections and MRSA was detected by Cefoxitin disc diffusion method and detection of Mec A gene by Polymerase chain reaction (PCR). Antibiotic susceptibility testing was performed by Kirby Baeur disc diffusion method. The Erythromycin resistant isolates were tested for D test. The differences in antibiotic susceptibility pattern between MRSA and MSSA was compared by Chi Square test using Graph pad Quick Calcs software and p value less than 0.05 was considered as significant Results : Out of the 204 Staphylococcus aureus isolates, 48 (23.5%) were identified as MRSA by Cefoxitin disc diffusion method. All these 48(23.5%) of isolates were also positive for Mec A gene by PCR. Inducible clindamycin resistance (iMLSB resistance phenotype) was observed among 24(11.7%) of the isolates. MRSA showed comparatively lesser susceptibility than MSSA (p ≤0.05). Among the MRSA inducible clindamycin resistance was seen among 11 (22.9%). Conclusions : Emergence of drug resistance warrants antibiotic susceptibility testing for all the isolates in the laboratory. Cefoxitin disc diffusion method can be used in resource constraint laboratory where PCR facilities are not available. Inducible clindamycin resistance phenotype (iMLS phenotype) must be checked for all isolates showing erythromycin resistance to prevent treatment failure. J Microbiol Infect Dis 2019; 9(3):125-128.