FIG 1.

Selection of antibiotic-resistant mutants by high inoculum plating. A. baumannii clinical isolates were cultured in MHII or RPMI medium overnight, and mutants were selected by plating bacteria on MHII or RPMI drug plates containing 8 mg/liter of RBT, 16 mg/liter of COL, or the combination of both antibiotics. No CFU were observed in any of the combination treatment groups. (A) For HUMC1, there was a significant difference between the combination group and RBT alone in MHII (Kruskal-Wallis, P = 0.008) and RPMI (Kruskal-Wallis, P = 0.027). (B) For LAC-4, there was a significant difference between the combination group and RBT alone in MHII (Kruskal-Wallis, P = 0.008) and RPMI (Kruskal-Wallis, P = 0.017). n = 3 for all groups. The median and interquartile range were plotted for all graphs.