Vol.63 No.3 May 2015
The drug susceptibility of major causative urinary tract infection bacteria, and molecular characterisation of the quinolone resistance-determining regions (QRDR) including gyrA and parC
1)Department of Urology, Juntendo University Faculty of Medicine, 3-1-3 Hongo, Tokyo, Japan
2)Department of Bacteriology, Center of Excellence for Infection Control Science, Juntendo University Faculty of Medicine
Abstract
We examined the drug susceptibilities to the bacteria isolated from urine of the patients suffering from urinary tract infection and their relation with patient's history. The major causative agents were Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa.
The results of susceptibility testing in gram-negative bacteria showed the increase of drug-resistant strains. Especially in E. coli, it was showed the increase of Fluoroquinolone (FQL) resistance strains.
To ascertain whether mutations were occurring in the quinolone resistance-determining regions of targets of quinolones, the gyrA and parC genes, nucleotide sequences of the Quinolone Resistance Determining Region (QRDR) were determined by choosing 46 E. coli isolates, the MIC values of which were more than 0.25 μg/mL. The QRDR regions of 46 isolates were classified into 4 types as follows based on the numbers of amino acid substitutions: 8, no substitution; 14, a substitution either in gyrA(S83L) or parC(S80I); 9,3 substitutions in gyrA(S83L and D87N/S83L and D87G) and parC(S80I) or gyrA(S83L) and parC(S80I and E84V); 15, 4 substitutions in gyrA(S83L and D87N) and parC(S80I and E84V/S80I or E84G/S80I and E84K). Generally, the MIC values of FQLs increased with the increase of the numbers of amino-acid substitutions, but at the higher MICs, e.g., 64-128 μg/mL, the numbers of substitutions were not always as many as expected.
Key word
urinary tract infection, Escherichia coli, fluoroquinolone, gyrA genes, parC genes
Received
September 22, 2014
Accepted
January 5, 2015
Jpn. J. Chemother. 63 (3): 343-349, 2015
