FIG. 2.

Bacteriostatic action of fluoroquinolones against resistant mutants. Isogenic strains of E. coli containing the indicated alleles of gyrA (A) or gyrA parC (B) were applied to LB agar plates containing various concentrations of the fluoroquinolones for determination of the MIC₉₉s. The MIC₉₉ for each mutant was then divided by the MIC₉₉ of wild-type or parC (S80L) cells to generate the normalized MIC₉₉ (the MIC₉₉s with wild-type cells were 0.038, 0.013, and 0.011 μg/ml for gatifloxacin [C-8-methoxy; solid bars], AM1121 [C-8-H; shaded bars], and ciprofloxacin [C-8-H; open bars], respectively. The data shown are the averages of two determinations.