Inducible Clindamycin resistance in Staphylococcus aureus and its therapeutic implications

Background: Staphylococcus aureus is a major cause of hospital-acquired and community-acquired infections worldwide. It causes various types of infections from relatively benign skin infections to life threatening systemic illness. S. aureus can readily develop antibiotic resistance especially with emergence of MRSA strains. The increasing incidence of MRSA has led to the excessive use of Macrolide-Lincosamide-StreptograminB (MLSB) especially clindamycin due to its excellent pharmakinetic properties. Presently, inducible clindamycin resistance is a cause of concern for Clinicians and Microbiologists while treating patients with S.aureus infection. Aim: Hence, the study was undertaken to detect the incidence of inducible clindamycin resistance in clinical isolates of Staphylococcus aureus in our tertiary care hospital. Materials and Methods: 130 clinical isolates of S.aureus were studied. Antibiotic susceptibility test was done by Kirby Bauer disc diffusion method. MRSA strains were detected by Cefoxitin (30μg) disc. Inducible Clindamycin resistance was detected by D zone test using erythromycin (15 μg) and Clindamycin (2μg) disc. Results: 56.2% strains were MRSA. 28.5% S.aureus strains produced Inducible Clindamycin resistance and hence were designated as iMLSB phenotype. Conclusion: The phenotypic detection of MRSA and Inducible Clindamycin resistance must be done in Clinical Microbiology Laboratory to treat patients effectively with S.aureus infection.