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CC BY-NC-ND 4.0 · J Lab Physicians 2022; 14(03): 290-294
DOI: 10.1055/s-0042-1742423
Original Article

Molecular Characterization of High-Level Aminoglycoside Resistance among Enterococcus Species

Autor*innen

  • Harish Manoharan 

    1   Department of Microbiology, Sri Ramachandra Institute for Higher Education and Research, Chennai, Tamil Nadu, India

  • Aishwarya K.V. Lalitha

    1   Department of Microbiology, Sri Ramachandra Institute for Higher Education and Research, Chennai, Tamil Nadu, India

  • Shanthi Mariappan

    1   Department of Microbiology, Sri Ramachandra Institute for Higher Education and Research, Chennai, Tamil Nadu, India

  • Uma Sekar

    1   Department of Microbiology, Sri Ramachandra Institute for Higher Education and Research, Chennai, Tamil Nadu, India

  • Geetha P. Venkataramana

    1   Department of Microbiology, Sri Ramachandra Institute for Higher Education and Research, Chennai, Tamil Nadu, India
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Abstract

Background Enterococci are nosocomial pathogen. They can develop high-level resistance to aminoglycoside by producing aminoglycoside modifying enzymes (AMEs). In enterococci, high level resistance to aminoglycosides is mediated by acquisition of plasmid mediated genes encoding for aminoglycoside modifying enzymes (AMEs). High level gentamicin resistance (MIC ≥ 500μg /mL) is predominantly mediated by aac(6′)-Ie-aph(2″)-Ia, encoding the bifunctional aminoglycoside modifying enzyme AAC(6′)-APH(2″). This enzyme eliminates the synergistic activity of gentamicin when combined with a cell wall active agent. Other AME genes such as aph(2″)-Ib, aph(2″)-Ic, aph(2″)-Id and ant(4′)-1a have also been detected in enterococci.

Objective This study was carried out to determine the diverse prevalence of AME and their pattern of occurrence in the clinical isolates of Enterococci.

Materials and Methods A total number of 150 clinical isolates were included in this study. Susceptibility to various antibiotics was determined by disc diffusion. Minimum Inhibitory Concentration (MIC) was ascertained by agar dilution method. Polymerase chain reaction was done to screen the following AMEs (aac(6′)-Ie-aph(2″)-Ia; aph(2″)-Ib; aph(2″)-Ic; aph(2″)-Id and aph(3′)- IIIa genes).

Results 51.3% of the study isolates exhibited high level gentamicin resistance. Polymerase chain reaction revealed that aph(3′)-111a is the most prevalent AME, followed by aac(6′)-1e-aph(2″)-1a. The combination of both the genes were detected in 44.1% of the study isolates. The rest of the AMEs and their combinations were not encountered in this study. 8.6% of the study isolates did not harbour any AME genes screened for, but was phenotypically resistant to gentamicin. In contrast 31.3% anchored the AME genes but phenotypically appeared susceptible to gentamicin.

Conclusion This study indicates the high- level aminoglycoside resistance disseminated among Enterococci in our geographical region. It also emphasizes the detection of AMEs by PCR is mandatory because strains that appear susceptible by disc diffusion and/or MIC method may harbour one or more AMEs genes leading to therapeutic failure.

Keywords

AMEs - Enterococcus species - high-level aminoglycoside resistance - encoding genes


Publikationsverlauf

Artikel online veröffentlicht:
23. Februar 2022

© 2022. The Indian Association of Laboratory Physicians. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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