Original article / research
Phenotypic Expression of erm Gene Among Staphylococcus aureus
Dr. Gaurav Dalela,
Associate Professor and HOD, Department of Microbiology, RUHS College of Medical Sciences, Jaipur – 302033,
Introduction: The increasing frequency of MRSA infections and rapidly changing patterns in antimicrobial resistance, led to renewed interest in the use of macrolide lincosamide– streptogramin B (MLSB) antibiotics to treat such infections.
Aim: To assess the prevalence of phenotypic expression of inducible resistance for clindamycin due to expression of erm genes, in clinical isolates of Methicillin resistant Staphylococcus aureus from various clinical samples using modified D test.
Materials and Methods: A total of 101 Methicillin resistant Staphylococcus aureus (MRSA) strains were included for induction tests which utilize closely approximated erythromycin, clindamycin and azithromycin discs (modified D test); the flattening or indentation of the clindamycin zone of inhibition adjacent to the erythromycin and / or azithromycin disk indicates inducible MLSB (macrolide lincosamide– streptogramin B) resistance.
Results: Among the 101 clinical isolates, 37 (36.63%) isolates shows D test positive using Erythromycin, Clindamycin and Azithromycin combination. Inducible resistance to clindamycin using azithromycin was found in 5.94% isolates which was the major achievement of the study, which will be confirmed by genotyping in future.
Conclusion: D-test should be performed on all MRSA isolates, to avoid erroneous reporting resulting in treatment failure, a partial modification in the D test can be made using azithromycin as it was helpful in our study, must be confirmed using genotyping.
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