Chromosomal mutations that accompany qnr in clinical isolates of Escherichia coli.

ABSTRACT: We examined 13 qnr-positive and 14 qnr-negative clinical isolates of Escherichia coli for mutations previously seen in a qnr-containing laboratory strain exposed to supra minimum inhibitory concentrations (MICs) of ciprofloxacin. Among the qnr-positive strains, those with ciprofloxacin MICs of ≥ 2 µg/mL had at least one mutation in gyrA. Mutations in parC were present in strains with a ciprofloxacin MIC of ≥ 128 µg/mL. The 6 most ciprofloxacin-resistant strains contained additional plasmid-mediated quinolone resistance determinants. aac(6')-Ib-cr was found in 5 of the 6 strains. Eleven of the 13 strains had alterations in MarR, 9 in SoxR, and 5 had mutations in AcrR. All had elevated expression of at least one efflux pump gene, predominantly acrA (92% of the strains), followed by mdtE (54%

SUBMITTER: Vinue L 

PROVIDER: S-EPMC5849519 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature