Rapid Bactericidal Effect of Rifampin on Mycobacterium Leprae *

Abstract

Rifampin was rapidly bactericidal for Mycobacterium leprae. Leprosy responds very slowly to current therapy, so there is a special need for more rapidly effective drugs. In mice rifampin exerted a bactericidal-type effect with single administration by gavage; the effect increased with dosage in the range 10 to 40 mg/kg of body weight. Five patients with lepromatous disease were treated with 600 mg rifampin daily, and the viability of the bacilli in their skin lesions was tested by inoculation of mice. Infectivity for mice had completely disappeared in the 1st specimen collected after the start of therapy—at 7 days in 4 patients and 14 days in 1. In 4 control patients treated with dapsone, infectivity for mice was lost much more slowly and in 1 was still present, though decreased, 112 days after the start of treatment. The slower loss of infectivity with dapsone is in accord with our previous experience in which the same methods were used.