FIG 1.

Fitness loss in colistin-resistant A. baumannii was due to enhanced susceptibility to oxidative stress and a defect in catalase activity. (A) Mass spectra of lipid A of A. baumannii clinical isolates. The peak at 2,034 m/z represents phosphoethanolamine. (B) A. baumannii clinical isolates competed for growth in LB for 24 h. Each symbol represents a single replicate. Data are representative of those from three independent experiments. (C) The survival of CR A. baumannii clinical isolates in the presence of 0.001% hydrogen peroxide was measured after 2 h. The percent survival was assessed as the CFU ratio of treated and untreated samples. Total catalase activity was quantified using in-gel catalase assays. Statistical analyses of competition experiments (one sample t test) were performed using GraphPad Prism. ***, P < 0.0005.