High prevalence of nalidixic acid resistant, ciprofloxacin susceptible phenotype among clinical isolates of Escherichia coli and other Enterobacteriaceae.
Therapeutic failure of infections during their treatment with quinolones has been often described. This may be due to the development of resistance during treatment of an infecting strain which already had diminished susceptibility to quinolones, even though the initial MIC did not exceed the breakpoint. In this study the prevalence of the nalidixic acid resistant, ciprofloxacin susceptible phenotype among Enterobacteriaceae was analyzed. The results showed that 113 out of 151 (74.83%) strains of the Enterobacteriaceae with diminished susceptibility to ciprofloxacin (MICs from 0.06 to 1 microg/ml) were resistant to nalidixic acid (MICs > 32 microg/ml). The Escherichia coli strains presenting this phenotype already have a mutation in the amino acid codon Ser-83 of the gyrA gene, so that the possibility of developing a second mechanism of resistance during treatment is very high.
Ruiz
Joaquim
J
Departament de Microbiologia, IDIBAPS, Hospital Clínic, Facultat de Medicina, Universitat de Barcelona, Villarroel 170, 08036-Barcelona, Spain.
Gómez
Julián
J
Navia
Margarita M
MM
Ribera
Anna
A
Sierra
Josep M
JM
Marco
Francesc
F
Mensa
Josep
J
Vila
Jordi
J
D000890:Anti-Infective Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology*; D027081:DNA Gyrase / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009268:Nalidixic Acid / Q000494:pharmacology*; D010641:Phenotype
D000890:Anti-Infective Agents; D009268:Nalidixic Acid; D002939:Ciprofloxacin; D027081:DNA Gyrase