Accumulation of ciprofloxacin (A) and ethidium bromide (B) without (open bars) or with (shaded bars) CCCP by P270 (NCTC11168), P1048 (cmeB++ [overexpressed]), P1038 (cmeB::Kanr), P1035 (cmeB::Kanr MAR mutant), P1043 (cmeF::Kanr), and P1036 (cmeF::Kanr MAR mutant). The values are from five independent experiments expressed as means ± standard deviations and were obtained at the 15-min time point.