In vitro synergistic activity between ofloxacin and ansamycins against Mycobacterium leprae.

The antimicrobial effects of ofloxacin, alone and in combination with either rifampicin or rifabutin, were evaluated against M. leprae, using in vitro cell-free culture system. The minimum inhibitory concentration (MIC) of ofloxacin against M. leprae was 1.5 micrograms/ml, while MICs of rifampicin and rifabutin were 0.4 and 0.2 microgram/ml, respectively. Combination of 0.375 microgram/ml ofloxacin and 0.05 microgram/ml of rifabutin exhibited synergistic bactericidal activity while the effect of combination of 0.75 microgram/ml ofloxacin and 0.2 microgram/ml rifampicin was additive bactericidal. Thus, combination of ofloxacin and rifabutin deserves further attention in multi-drug therapy of leprosy.