Fig 5.

Colistin induces hydroxyl radical production in MDR clinical isolates. Cultures of colistin-sensitive MDR strain CI-2 (A) or CI-3 (B) or a colistin-resistant PDR A. baumannii strain CI-4 (C) were treated with 2 μg of colistin/ml or left untreated for 30 min. After treatment, the hydroxyl radical specific fluorescent dye 3′-(p-hydroxyphenyl) fluorescein was added, and fluorescence was measured (490 nm/515 nm). The data are representative of two independent experiments. Bars represent the means and standard deviations of triplicate samples. ***, P < 0.0001; *, P < 0.05.