FIG 1.

Effect of moxifloxacin on biosensor oxidation, ROS level, and bacterial survival. (A) Moxifloxacin increases oxidative stress, which increases the ratio of oxidized (MSSM) to reduced (MSH) mycothiol via mycothiol-dependent peroxiredoxin (Prx) or peroxidase (Mpx). Oxidation of Mrx1-roGFP2 increases fluorescence intensity for excitation at ~400 nm and decreases it for excitation at ~490 nm. (B) Strain M. tuberculosis roGFP2 was exposed to the indicated concentrations of moxifloxacin (1× MIC = 0.5 μM) for 48 h, and the ratiometric response of the biosensor and survival following treatment were determined. (C) Cells were treated as for panel B, and ROS were quantified by flow cytometry using CellROX deep red dye. Cumene hydroperoxide (CHP; 10 mM) served as a positive control. Data represent mean fluorescence intensity of the dye. (D) Exponentially growing M. tuberculosis H37Rv was treated with moxifloxacin at the indicated concentrations for the indicated times; survival was assessed by determining CFU. (E) Time-kill curves for M. tuberculosis treated with 10× MIC of moxifloxacin. Error bars represent standard deviations from the mean. Data represent at least two independent experiments performed in at least duplicate. Statistical significance was calculated against the no-treatment control (****, P < 0.0001; ***, P < 0.001; **, P < 0.01; *, P < 0.05).