Study of drug interaction, mutant frequency and mutant prevention concentration of DFMBT against Mycobacterium tuberculosis H37RV.

In the present study 7,7-Dimethyl-4-(4-trifluoromethyl-phenylamino)-2,4,4a,6,7,8-hexahydro-benzo[d] [1,3]thiazin-5-one (DFMBT) was synthesized and evaluated for in vitro activity against Mycobacterium tuberculosis (M.tb) H37RV. Results demonstrated that at 64x MIC, DFMBT completely sterilized the TB culture from day 4 of the incubation whereas at 32 and 16x MIC, it sterilized the TB culture from day 8. The bacterial cultures were completely sterilized by DFMBT at 8x MIC from day 16 of incubation. DFMBT showed 1.5 μg/mL MIC value as compared to the standard anti-tuberculosis drugs using broth macro-dilution method. The MBC value of DFMBT was found to be 6.0 μg/mL whereas for INH, RIF, AMK and LVX the values were found to be 0.312, 0.156, 5.0 and 5.0 μg/mL, respectively. The DFMBT in combination with INH/RIF or AMK showed the ∑FIC value of 0.258, 0.252 and 0.453, respectively indicating synergistic interaction. Moreover, the value of ∑FIC for the combination of DFMBT with LVX was found to be 1.33 suggesting and additive interaction. The post antibiotic effect of DFMBT at 1x and 64x MIC was found to be 29.89 ± 10.12 and 158.75 ± 17.50 h, respectively. The DFMBT showed an MPC value of 150 μg/mL which was intermediate between INH and RIF. In summary, DFMBT exhibits bacteriostatic as well as bactericidal effect on Mycobacterium tuberculosis H37RV. It has synergistic interaction with INH, RIF and AMK anti-TB drugs, descent post antibiotic effect, mutation frequency and mutant prevention concentration. Thus, DFMBT may be developed as an effective agent as anti-TB compound.