Prevalence of MLSB Resistance and Observation of erm A & erm C Genes At A Tertiary Care Hospital

Background: The increasing resistance to macrolide, lincosamide, streptogramin B (MLSB) agents among Staphylococcus aureus is becoming a challenge to microbiologist. Clindamycin has been a useful drug for treatment of infection caused by the staphylococcus aureus, but change in clindamycin sensitivity pattern due to various mechanisms is leading to therapeutic failure. One of the important mechanisms is mediation of resistance by erm genes. Staphylococcus strains which have erm genes show inducible clindamycin resistance that cannot be determined by routine disk diffusion test resulting in treatment failure. Aim: This study was aimed to detect the prevalence of MLSBi and MLSBc resistance and observation of erm A & erm C genes among MLSBi isolates. Materials and Methods: A total 500 Staphylococcus aureus were isolated; they were checked by disk induction test (D-Test). Those isolates which showed inducible clindamycin resistance were randomly selected and subjected to PCR for the observation of erm A and erm C genes. Results: Prevalence of MLSBi and MLSBc isolates were almost similar that is 10.8% and 11.6% respectively. MLSBi isolates showed more resistance to drugs when compared to MLSBc isolates. Neither of MLSBi and MLSBc isolates was resistant to Vancomycin and Linezolid. Inducible clindamycin was mainly due to presence of erm A gene. Conclusion: D-test should be mandatory at every microbiology laboratory and should be used in routine antibiotic procedure which will minimize the misuse of drug ultimately minimize the risk of treatment failure. PCR should be performed for the detection of genes responsible for erythromycin resistance as it is a quick and most sensitive method.