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Journal of Pathogens
Volume 2017 (2017), Article ID 3256952, 5 pages
Research Article

Analysis of Aminoglycoside Modifying Enzyme Genes Responsible for High-Level Aminoglycoside Resistance among Enterococcal Isolates

Department of Microbiology, Armed Forces Medical College, Pune, India

Correspondence should be addressed to Vishal Shete; moc.liamg@49etehslahsiv

Received 14 August 2017; Accepted 17 October 2017; Published 24 December 2017

Academic Editor: Patrizia Messi

Copyright © 2017 Vishal Shete et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Enzymatic modification results in high-level resistance to aminoglycoside (HLAR), which eliminates the synergistic bactericidal effect of combined exposure to a cell wall-active agent and an aminoglycoside. So aim of the study was to determine prevalence of HLAR enterococcal isolate and to study distribution of aminoglycoside modifying enzyme genes in them. A total of 100 nonrepeat isolates of enterococci from various clinical samples were analyzed. As per Clinical and Laboratory Standards Institute guidelines enterococci were screened for HLAR by Kirby-Bauer disc diffusion method. Minimum inhibitory concentration of all isolates for gentamicin and streptomycin was determined by E-test. Multiplex polymerase chain reaction (PCR) was carried out for HLAR enterococcal isolates to identify aminoglycoside modifying enzymes genes responsible for resistance. 60% isolates were found to be high-level gentamicin resistant (HLGR) whereas 45% isolates were found to be high-level streptomycin resistant (HLSR). By multiplex PCR 80% HLGR isolates carried bifunctional aminoglycoside modifying enzyme gene aac(6)-Ie-aph(2′′)-Ia whereas 18 out of 45 high-level streptomycin resistant, that is, 40%, isolates carried aph(3)-IIIa. However, aph(2′′)-Ib, aph(2′′)-Ic, aph(2′′)-Id, and ant(4)-Ia genes which encode other aminoglycosides modifying enzymes were not detected. Bifunctional aminoglycoside modifying enzyme gene aac(6)-Ie-aph(2′′)-Ia is the predominant gene responsible for HLAR.