1994 Volume 17 Issue 7 Pages 927-930
Q-35, 1-cyclopropy-6-fluoro-1, 4-dihydro-8-methoxy-7-(3-methylaminopiperidine-1-yl)-4-oxoquinoline-3-car-boxylic acid, has excellent activity against gram-positive bacteria and inhibits S. aureus gyrase at concentrations more than 10-fold lower than those of other quinolones. In this paper, the effect of the C-7 and C-8 substituents of Q-35 on the inhibitory activity of gyrase purifled from S. aureus, M. luteus, E. coli, and P. aeruginosa are described. In addition, intracellular accumulation of Q-35 was examined. The 50% inhibitory concentrations (IC50) of Q-35, 8-fluoro-Q-35, and 8-hydro-Q-35 on DNA gyrase purified from S. aureus were 2.5, 7.8, and 68μg/ml, respectively. The IC50 on gyrase from P. aeruginosa were 11, 5.2, and 17 μg/ml, respectively. It is concluded that the introduction of a methoxy group into the 8 position of the quinolone leads to greater antibacterial activity against gram-positive bacteria. The concentrations of Q-35 which accumulated in S. aureus and E. coli were almost equal to ciprofloxacin, but in P. aeruginosa, Q-35 was lower than ciprofloxacin.