The Effect of Rifampicin on Mycobacterium leprae in Mice

Rifampicin was shown to be highly active against Mycobacterium leprae in mice, completely inhibiting the in vivo multiplication of this organism at a dosage of 0.1 mg per day by gavage. When drug administration was started after the establishment of M. leprae in mice (30 weeks after infection), rifampicin stopped any further bacillary increase. A second inoculation of the organisms from treated mice showed complete loss of viability. Exposure of M. leprae to rifampicin for a short period before infection significantly reduced the viability of the organism.