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Title: Mechanisms involved in the development of resistance to fluoroquinolones in Escherichia coli isolates
Authors: Del Mar Tavío, María 
Vila, Jordi
Ruiz, Joaquím
Ruiz, José
Martín-Sánchez, Antonio Manuel 
Jiménez De Anta, María Teresa
Keywords: Quinolone Resistance
Polyacrylamide Gels
Dna Gyrase
Pare Gene
Mutants, et al
Issue Date: 1999
Publisher: 0305-7453
Journal: Journal of Antimicrobial Chemotherapy 
Abstract: Eighteen quinolone-resistant isolates of Escherichia coli were selected by exposing ten clinical isolates to increasing concentrations of norfloxacin and lomefloxacin. The mutant isolates showed a multiple-antibiotic-resistance phenotype. All of them contained single mutations in gyrA consisting of the substitution of Ser-83-->Leu (n = 14), Val (n = 1) or Ala (n = 1) and the substitution of Asp-87-->Asn (n = 2). Only one concomitant mutation in parC(Ser-80-->Arg) was detected. Four parent isolates exhibited a single mutation in gyrA which required less than or equal to 1 mg/L of norfloxacin to be inhibited. Fluoroquinolone resistance, in the 18 quinolone-resistant mutants, was a result of mutations affecting DNA gyrase plus decreased fluoroquinolone uptake. This latter mechanism of resistance was a combined effect of an absence of OmpF and an increase in active efflux in eight isolates, or an increased active efflux alone in the remaining ten selected mutants.
ISSN: 0305-7453
Source: Journal of Antimicrobial Chemotherapy[ISSN 0305-7453],v. 44, p. 735-742
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