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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

Plasmid-mediated quinolone resistance in non-Typhi serotypes of Salmonella enterica

Kathryn Gay1, Ari Robicsek, Jacob Strahilevitz

  • 1Atlanta Research and Education Foundation, Atlanta, GA, USA. kgay@cdc.gov

Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America
|June 29, 2006
PubMed
Abstract

Insights

Plasmid-mediated quinolone resistance genes (qnr) were found in non-Typhi Salmonella human isolates in the US. This finding highlights the potential for spread through the food supply, posing a public health concern.

Area of Science:

  • Microbiology
  • Genetics
  • Public Health

Background:

  • Serious Salmonella infections are treated with fluoroquinolones or extended-spectrum beta-lactams.
  • Plasmid-mediated quinolone resistance, encoded by qnr genes, is increasingly recognized in Enterobacteriaceae.
  • This study investigated qnr variants in human non-Typhi Salmonella enterica isolates from the US.

Purpose of the Study:

  • To identify and characterize qnr genes in non-Typhi Salmonella isolates from the United States National Antimicrobial Resistance Monitoring System for Enteric Bacteria.
  • To assess the prevalence and distribution of plasmid-mediated quinolone resistance in these isolates.

Main Methods:

  • Screening of 233 non-Typhi Salmonella isolates with elevated ciprofloxacin MICs and 102 susceptible isolates for qnr genes (A, B, S) using PCR.
  • Sequencing of qnr and quinolone resistance-determining regions for positive isolates.
  • Characterization of plasmids carrying qnr genes via conjugation or transformation.

Main Results:

  • Conjugative plasmids with qnrB variants were found in Salmonella enterica serotypes Berta and Mbandaka.
  • The S. Mbandaka isolate also harbored an extended-spectrum beta-lactamase.
  • Nonconjugative plasmids with qnrS variants were detected in Salmonella enterica serotypes Anatum and Bovismorbificans.

Conclusions:

  • Plasmid-mediated quinolone resistance is present, though uncommon, in US non-Typhi Salmonella isolates, even susceptible ones.
  • The detection of qnr genes in human non-Typhi Salmonella suggests potential transmission via the food supply.
  • This represents a significant public health concern requiring ongoing surveillance.

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