High-level gentamicin resistance mediated by Aac(6′)-Ie-aph(2”)-Ia gene in Enterococcus species isolated from clinical samples in Northern India

CONTEXT: Enterococci are known to cause life-threatening infections which are difficult to treat as the organism harbors innate resistance to many antibiotics and can amass resistance toward many others through plasmid-mediated genetic exchange. AIMS: The study evaluates the drug susceptibility profile of various Enterococcus species isolated from various patient specimens submitted for bacteriological analysis and check the incidence of aac(6′) Ie-aph(2”) Ia gene. SETTING AND DESIGN: This in vitro cross-sectional study was executed at bacteriology laboratory of a 470 bedded hospital in New Delhi. MATERIALS AND METHODS: Drug susceptibility testing was carried out on enterococcal isolates. High-level gentamicin-resistant (HLGR) isolates detected by micro broth dilution assay were then subjected to molecular detection of aac(6′) Ie-aph(2”) Ia gene. STATISTICAL ANALYSIS USED: The level of significance was established by Chi-square test. RESULTS: Among the 182 enterococcal stains detected, 76.9% were Enterococcus faecalis and 20.3% were Enterococcus faecium. 12.08% strains were vancomycin resistant. 39% expressed resistance toward high-level gentamicin (HLG) and this finding was significantly higher in E. faecium than E. faecalis. HLGR strains expressed a higher degree of resistance to other drugs in contrast to non-HLGR isolates. In 67 out of 71 HLGR isolates the bifunctional gene was detected. CONCLUSION: Considerable presence of HLG and vancomycin resistance in the clinical isolates is alarming and should be taken seriously. The study shows high dissemination of aac(6′)-Ie-aph(2”)-Ia gene among Enterococci isolated from the region.