Molecular Characterization of Macrolide Resistance Genes among the Clinical Isolates of Enterococci.

Abstract

Enterococci have emerged as an important pathogen due to their intrinsic and acquired resistance to several antibiotics. Macrolides were used to treat most of the gram positive infections. However, recently there is an increase in acquired resistance towards these antibiotics which leads to therapeutic challenge. This study was carried out to screen clinical isolates of enterococci for erythromycin resistance phenotypes and molecular characterization of macrolide resistance genes. A total of 97 enterococcal isolates were included, among which 60.8% of isolates were identified as E. faecium followed by 30.9% of E .faecalis. 75.2% (70/97) were identified as MDR isolates. 3.09% were iMLSB, 55.6% were cMLSB and 38.8% isolates neither belong to iMLSB/cMSLB phenotypes when tested by double disk diffusion method. The MIC50 and MIC90 are > 256 µg/ml concentration. Molecular analysis of ermgenes revealed that 48.45% isolates were positive for erm B gene while other tested genes such aserm A, erm C and mef A genes were not amplified by PCR. In our study, the predominant species identified was E. faecium. Constitutive erythromycin resistance was higher and only erm B gene was amplified among our isolates. Relatively, higher percentage of erythromycin resistance with higher MIC value was observed among our isolates.