Clindamycin as a plausible treatment option for methicillin resistant Staphylococci: Significance of inducible clindamycin resistance

Abstract

Introduction: There has been renewed interest in use of Macrolide-Lincosamide-Streptogramin B (MLSB) due to increasing resistance in methicillin resistant Staphylococcus aureus (MRSA). Clinical failure of clindamycin therapy has been reported due to multiple mechanisms that confer resistance to MLSB antibiotics. We report different resistant phenotypes of MLSB in Staphylococcus aureus (S. aureus) and coagulase negative Staphylococcus species (CONS). Material and Methods: A total of 277 Staphylococcal isolates were collected from invasive clinical samples over a period of one year. Isolates were identified by standard microbiological procedures and subjected to antimicrobial susceptibility testing as per CLSI guidelines. Staphylococcal isolates were screened for methicillin resistance and Macrolide-Lincosamide-Streptogramin B (MLSB) phenotypes.Results: Out of 277 isolates, 253 were S. aureus and 24 were CONS. Among 163(58.14%) MRSA isolates, 55(33.74%) and 34(20.86%) isolates showed inducible (iMLSB) and constitutive (cMLSB) clindamycin resistance respectively, while 19(11.11%) isolates presented with M/MSB phenotype. Inducible and constitutive clindamycin resistance was found to be greater in MRSA isolates than in methicillin sensitive Staphylococcus aureus (MSSA) (11.11% iMLSB, 13.33% cMLSB, 17.78% M/MSB). Conclusion: Higher prevalence of iMLSB and cMLSB phenotypes specially among MRSA emphases the need of D-test to be performed while using clindamycin as an alternative to higher and parenteral antistaphylococcal antimicrobials.