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Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach
12:32

Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach

Published on: December 14, 2019

Quinolone resistance in bacteria: emphasis on plasmid-mediated mechanisms

Xian-Zhi Li1

  • 1Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA. xianzhi_li@hc-sc.gc.ca

International Journal of Antimicrobial Agents
|May 14, 2005
PubMed

Insights

The discovery of plasmid-borne qnr genes significantly expands understanding of bacterial quinolone resistance. These genes protect DNA gyrase, increasing resistance and facilitating rapid spread of antimicrobial resistance.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Bacterial resistance to quinolones/fluoroquinolones is a growing concern.
  • Traditionally, resistance was linked to chromosomal alterations in DNA gyrase/topoisomerase IV or efflux pumps.
  • The emergence of plasmid-mediated resistance mechanisms was previously underestimated.

Purpose of the Study:

  • To investigate the role of plasmid-borne quinolone resistance determinants (qnr).
  • To understand the molecular mechanisms and dissemination of qnr-mediated resistance.
  • To explore the implications of qnr in the context of overall antimicrobial resistance.

Main Methods:

  • Review of recent reports on Qnr and its homologues in Gram-negative bacteria.
  • Analysis of the molecular function of Qnr in protecting DNA gyrase.
  • Examination of the association of qnr-plasmids with integrons and other resistance genes.

Main Results:

  • The qnr gene, encoding a pentapeptide repeat protein, protects DNA gyrase from quinolones.
  • Qnr enhances resistance levels by interacting with chromosomal mechanisms.
  • Qnr-bearing strains exhibit higher mutation frequencies for quinolone resistance.
  • Qnr-plasmids are often integron-associated, carrying multiple antimicrobial resistance genes (e.g., beta-lactams, aminoglycosides).

Conclusions:

  • Plasmid-mediated qnr genes represent a significant and emerging mechanism of bacterial quinolone resistance.
  • Qnr facilitates the rapid dissemination of quinolone resistance determinants globally.
  • The presence of qnr, especially on mobile genetic elements, poses a substantial threat to quinolone efficacy and necessitates strategies to minimize resistance development.

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