In vitro activity of a new rifamycin derivative against Mycobacterium leprae.

The antimicrobial effects of T9 (3-(4-cinamyl-1-piperazinyl)iminomethyl rifamycin SV) alone and in combination with ofloxacin, against strains of M. leprae were evaluated, using an in vitro cell-free culture system. The minimum inhibitory concentrations (MICs) of T9 against rifampin-sensitive and rifampin-resistant strains of M. leprae were 0.1 microgram/ml and 0.4 microgram/ml, respectively. Furthermore, in common with rifabutin, but not with rifamycin, T9 demonstrated synergy with ofloxacin against both rifampin-sensitive rifampin-resistant strains of M. leprae. The results suggest that T9, in combination with ofloxacin as part of multidrug regimens, warrants further evaluation as treatment for patients with leprosy.