Clinical significance of DNA gyrase gyrA mutations in quinolone-resistant urinary isolates of Pseudomonas aeruginosa

Abstract

The clinical significance of DNA gyrase gyrA mutations in quinolone-resitant strains of Pseudomonas aeruginosaisolated from patients with complicated urinary tract infection (UTI) was studied by investigating annual changes in ofloxacin (OFLX) resistance, incidence of DNA gyrase gyrA mutations, and the relation between gyrA mutation and bacteriological response to the fluoroquinolone treatment. OFLX-resistant (MIC≥25μg/ml) strains increased from 11.8% in 1978 to 58.6% in 1993. DNA gyrasegyrAmutation was observed in 27 (57.4%) of 47 strains isolated before fluoroquinolone treatment and in 100% of 30 strains isolated after treatment. Mutation was observed in 1 (4.8%) of the 21 strains for which the MIC of OFLX was 12.5 μg/ml or lower and in 100% of the 32 strains for which the MIC of OFLX was 25μg/ml, ughni or higher. The eradication rate for the 20 strains without mutations was 90.0%, versus 11.1% for the 27 strains with mutations. This difference was statistically significant (p<0.01). The bacteriological and clinical breakpoint of OFLX MIC was considered to be 12.5 μg/ml, and this was also the concentration at which gyrA mutations began to appear. DNA gyrase gyrAmutation was considered to be clinically important as a mechanism of the fluoroquinolone resistance of urinary isolates of P. aeruginosa.