GENOTYPIC CHARACTERISATION OF MLS (MACROLIDE–LINCOSAMIDE–STREPTOGRAMIN B) RESISTANCE IN CLINICAL ISOLATES OF STAPHYLOCOCCUS AUREUS
Main Article Content
Keywords
Staphylococcus aureus, MLSB resistance, ermA, ermC, inducible clindamycin resistance, PCR.
Abstract
Background:
Resistance to macrolide–lincosamide–streptogramin B (MLSB) antibiotics in Staphylococcus aureus is primarily mediated by erm genes encoding rRNA methyltransferases. Among these, ermA and ermC are the major determinants conferring inducible or constitutive resistance. Phenotypic identification of inducible clindamycin resistance using D-test has clinical relevance, but genotypic detection provides confirmatory insights into resistance mechanisms.
Methods:
A cross-sectional study was conducted at Index Medical College Hospital & Research Centre (IMCHRC), Indore (2021–2024). A total of 250 S. aureus isolates from various clinical specimens were processed. Phenotypic detection of MLSB resistance was performed using D-test and VITEK-2 system. Genotypic characterization for ermA and ermC genes was carried out using PCR.
Results:
Among 250 isolates, 59 % were MRSA and 41 % MSSA. iMLSB phenotype was observed in 26 % MRSA and 11 % MSSA isolates, while cMLSB was seen in 40 % MRSA and 11 % MSSA. ermC was the predominant gene, followed by ermA. D-test sensitivity and specificity were 57.6 % and 100 %, respectively, compared to VITEK-2.
Conclusion:
The predominance of ermC among iMLSB isolates suggests plasmid-mediated dissemination. Routine molecular surveillance of erm genes is essential to prevent clindamycin treatment failure and guide antibiotic stewardship.
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Ms Tripti Mani Tripathi
PhD Scholar, Department of Microbiology, Index Medical College Hospital & Research Centre, Indore, India. (Malwanchal University)
Dr Ramanath Karicheri
Professor, Department of Microbiology, Index Medical College Hospital & Research Centre, Indore, India. (Malwanchal University)