In vitro activity of thiacetazone on mycobacterial species belonging to the Mycobacterium tuberculosis complex.

Thiacetazone, despite frequent side-effects, may still be considered for the treatment of new tuberculosis cases when there is a shortage of drugs and for the management of multidrug-resistant tuberculosis. Fifty-four strains of M. tuberculosis complex were characterised based on the minimum inhibitory concentration (MIC) of thiacetazone and the growth pattern in the presence of different concentrations of the drug. The results showed that the MIC of thiacetazone to type II M. africanum strains was significantly higher than for other strains in the study (P < 0.01). Thiacetazone showed a paradoxical effect on 63% of strains where lower concentrations exhibited a better inhibiting activity than higher concentrations.