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. 2011 Mar;55(3):1266-9.
doi: 10.1128/AAC.00927-10. Epub 2010 Dec 20.

In vitro effect of qnrA1, qnrB1, and qnrS1 genes on fluoroquinolone activity against isogenic Escherichia coli isolates with mutations in gyrA and parC

A Briales  1 , J M Rodríguez-Martínez, C Velasco, P Díaz de Alba, J Domínguez-Herrera, J Pachón, A Pascual
Affiliations

In vitro effect of qnrA1, qnrB1, and qnrS1 genes on fluoroquinolone activity against isogenic Escherichia coli isolates with mutations in gyrA and parC

A Briales et al. Antimicrob Agents Chemother. 2011 Mar.

Abstract

This article provides an analysis of the in vitro effect of qnrA1, qnrB1, and qnrS1 genes, combined with quinolone-resistant Ser83Leu substitutions in GyrA and/or Ser80Arg in ParC, on fluoroquinolone (FQ) resistance in isogenic Escherichia coli strains. The association of Ser83Leu substitution in GyrA, Ser80Arg substitution in ParC, and qnr gene expression increased the MIC of ciprofloxacin to 2 μg/ml. qnr genes present in E. coli that harbored a Ser83Leu substitution in GyrA increased mutant prevention concentration (MPC) values to 8 to 32 μg/ml. qnr gene expression in E. coli may play an important role in selecting for one-step FQ-resistant mutants.

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Figures

FIG. 1.
FIG. 1.
Viable bacterial counts in time-kill curve assays with ciprofloxacin (CIP) 1 μg/ml. (A) Isogenic wild-type E. coli ATCC 25922, with and without qnrA1, qnrB1, or qnrS1 gene expression; (B) isogenic mutant E. coli ATCC 25922-S83L, with and without qnrA1, qnrB1, or qnrS1 gene expression.
See this image and copyright information in PMC

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