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Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
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Smaqnr, a new chromosome-encoded quinolone resistance determinant in Serratia marcescens

C Velasco1, J M Rodríguez-Martínez, A Briales

  • 1Department of Microbiology, University of Seville, Seville, Spain. cvelasco@us.es

The Journal of Antimicrobial Chemotherapy
|November 28, 2009
PubMed
Abstract

Insights

A novel quinolone resistance gene, SmaQnr, identified in Serratia marcescens, confers reduced susceptibility to fluoroquinolones when expressed in Escherichia coli. This finding suggests S. marcescens may be a reservoir for quinolone resistance genes.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Quinolone antibiotics are crucial for treating bacterial infections.
  • Emerging resistance mechanisms threaten their efficacy.
  • Qnr-like proteins are known to confer reduced susceptibility to quinolones.

Purpose of the Study:

  • To identify and characterize a novel quinolone resistance determinant in Serratia marcescens.
  • To investigate the role of the identified protein, SmaQnr, in quinolone resistance.
  • To explore the prevalence of similar genes within the Serratia genus.

Main Methods:

  • In silico analysis to identify Qnr-like genes.
  • Gene cloning and expression in Escherichia coli.
  • Determination of Minimum Inhibitory Concentration (MIC) values for various quinolones.
  • Reverse transcription-PCR (RT-PCR) for gene expression analysis.
  • Southern hybridization for gene prevalence studies.

Main Results:

  • A novel Qnr-like protein, SmaQnr, was identified in Serratia marcescens.
  • Expression of SmaQnr in E. coli reduced susceptibility to fluoroquinolones and nalidixic acid.
  • The SmaQnr gene is transcribed in its natural host, S. marcescens.
  • Southern blot analysis indicated the presence of similar genes in other Serratia species.

Conclusions:

  • SmaQnr confers reduced susceptibility to fluoroquinolones in E. coli.
  • S. marcescens may play a role in the dissemination of quinolone resistance.
  • The genus Serratia could be a reservoir for qnr-like quinolone resistance genes.

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