Mutant selection window. (A) Recovery of resistant mutants from agar plates containing various concentrations of fluoroquinolone (adapted from data presented in Dong et al., Antimicrob. Agents Chemother. 43:1756-1758, 1999). Adding a methoxy group to the C-8 position shifts the curve to lower concentrations and shortens the plateau. (B) Pharmacokinetic representation of mutant selection window. MIC and MPC were determined as shown in panel A. Double-headed arrows indicate mutant selection windows. Source: Xilin Zhao, unpublished.