Contribution of the 8-methoxy group to the activity of gatifloxacin against type II topoisomerases of Streptococcus pneumoniae.
The inhibitory activities (50% inhibitory concentrations [IC(50)s]) of gatifloxacin and other quinolones against both DNA gyrase and topoisomerase IV of the wild-type Streptococcus pneumoniae IID553 were determined. The IC(50)s of 10 compounds ranged from 4.28 to 582 microg/ml against DNA gyrase and from 1.90 to 35.2 microg/ml against topoisomerase IV. The inhibitory activity against DNA gyrase was more varied than that against topoisomerase IV among fluoroquinolones. The IC(50)s for DNA gyrase of the 8-methoxy quinolones gatifloxacin and AM-1147 were approximately seven times lower than those of their 8-H counterparts AM-1121 and ciprofloxacin, whereas the IC(50)s for topoisomerase IV were 1.5 times lower. Moreover, the IC(50) ratios (IC(50) for DNA gyrase/IC(50) for topoisomerase IV) of gatifloxacin, AM-1147, and moxifloxacin, which possess 8-methoxy groups, were almost the same. The 8-methoxy quinolones showed higher antibacterial activity and less mutant selectivity against IID553 than their 8-H counterparts. These results suggest that the 8-methoxy group enhances both target inhibition, especially for DNA gyrase, leading to potent antipneumococcal activity and dual inhibition against both DNA gyrase and topoisomerase IV in the bacterial cell.
Kishii
Ryuta
R
Discovery Research Laboratories, Kyorin Pharmaceutical Co., Ltd., Shimotsuga, Tochigi 329-0114, Japan. ryuuta.kishii@mb2.kyorin-pharm.co.jp
Takei
Masaya
M
Fukuda
Hideyuki
H
Hayashi
Katsuhiko
K
Hosaka
Masaki
M
D000890:Anti-Infective Agents / Q000494:pharmacology*; D001483:Base Sequence; D024841:Fluoroquinolones; D000077734:Gatifloxacin; D013296:Streptococcus pneumoniae / Q000201:enzymology* / Q000235:genetics; D013329:Structure-Activity Relationship; D059005:Topoisomerase II Inhibitors
D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D059005:Topoisomerase II Inhibitors; D000077734:Gatifloxacin