FIG 6.

N-acetyl cysteine increases oxidative stress and moxifloxacin-mediated killing of M. tuberculosis. NAC (1 mM) was administered 1 h before addition of moxifloxacin (MOXI; 1× MIC = 0.5 μM) at the indicated concentrations followed by 48 h of incubation. (A) Experimental plan. (B) Oxidative stress, measured by the ratiometric response of the Mrx1-roGFP2 biosensor. (C) Bacterial survival, measured by plating on 7H11 agar. (D) Effect of NAC and moxifloxacin combination with dormant bacilli. M. tuberculosis cultures were starved of nutrients for 14 days and then treated with moxifloxacin for 5 days in the presence or absence of NAC (1 mM) before determination of survival. Rifampicin (Rif; 25 μM) served as a positive control. (E) NAC (1 mM) was added when cultures were placed in Vacutainer tubes followed by the treatment conditions indicated in Fig. S2A and D. Metronidazole (Mtz; 10 mM) served as a positive control. Statistical considerations were as for Fig. 1.