Activity of drug combinations against dormant Mycobacterium tuberculosis

Abstract

Aerobic (5-day-old cultures) and nonreplicating (dormant) Mycobacterium tuberculosis (5-, 12-, and 19-day-old cultures) bacteria were treated with rifampin (R), moxifloxacin (MX), metronidazole (MZ), amikacin (AK), or capreomycin (CP) for 7, 14, and 21 days. R-MX-MZ-AK and R-MX-MZ-CP killed both aerobic and dormant bacilli in 21 days, as shown by lack of regrowth in solid and liquid media. R-MX-MZ-AK and R-MX-MZ-CP also caused a strong decrease of nonreplicating bacilli in 7 days in a cell-based dormancy model.

FIG. 1.

Survival of M. tuberculosis in the Wayne dormancy culture model after 7, 14, and 21 days of exposure to drugs, as estimated by CFU counts. Five-day-old aerobic (A5), replicating cultures were incubated with drugs. Five-, 12-, and 19-day-old hypoxic (H5, H12, and H19, respectively), nonreplicating cultures were incubated with drugs. Dashed lines indicated the limits of log₁₀ CFU per milliliter detected on Middlebrook 7H10 plates (5 CFU/ml). R, rifampin; MX, moxifloxacin; MZ, metronidazole; AK, amikacin; CP, capreomycin. Error bars, standard deviations.

FIG. 2.

Survival of M. tuberculosis in the Wayne dormancy culture model after 7, 14, and 21 days of exposure to drugs, as estimated by regrowth in liquid medium (day to positivity [DTP]) by using the BACTEC MGIT 960 system. Five-day-old aerobic (A5), replicating cultures were incubated aerobically with drugs. Five-, 12-, and 19-day-old hypoxic (H5, H12, and H19, respectively), nonreplicating cultures were incubated anaerobically with drugs. R, rifampin; MX, moxifloxacin; MZ, metronidazole; AK, amikacin; CP, capreomycin. In panels G to L, DTP of R-MX and R-MX-MZ are shown (dashed lines) for a better comparison of overall results. Means and standard deviations from three experiments are shown.

FIG. 3.

Survival of nonreplicating M. tuberculosis bacilli inside adipocytes after 7 days of exposure to drugs, as estimated by CFU counts. R, rifampin; MX, moxifloxacin; MZ, metronidazole; AK, amikacin; CP, capreomycin. Means and standard deviations from triplicate plates of one representative experiment out of two are shown.