Inducible Clindamycin Resistance: A Potential Threat in Treating Staphylococcus aureus Infection

Clindamycin is an aminoglycoside used in treatment of skin & soft tissue infections caused by both Methicillin resistant Staphylococcus aureus (MRSA) and Methicillin sensitive Staphylococcus aureus (MSSA). Staphylococcus aureus becomes resistant to erythromycin through either erm or msr A genes. Strains with erm-mediated erythromycin resistance may possess inducible clindamycin resistance but appear susceptible to clindamycin by disc diffusion test. The objective was to determine the prevalence of erythromycin induced clindamycin resistance among clinical isolates of S. aureus in our tertiary care hospital. A total of 243 Staphylococcus aureus isolates from various clinical samples submitted in the dept. of Microbiology at our tertiary care hospital were studied. Inducible clindamycin resistance was detected by erythromycin and clindamycin disc approximation test (D-zone test) as per CLSI guidelines. Among the 243 S. aureus isolates, 73.1% and 28.7% of MRSA and MSSA respectively showed erythromycin resistance. 31.2% and 14.8% of MRSA and MSSA were found to be positive for D test. Along with conventional antibiogram routine D-zone testing for detection of clindamycin resistance can reduce hospital acquired Staphylococcal infection.