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.