Ten Years of Dapsone in Lepromatous Leprosy: Clinical, Bacteriological and Histological Assessment and the Finding of Viable Leprosy Bacilli

Abstract

Twelve lepromatous patients who had completed lOto 12.5 years' continuous chemotherapy, principal!y or entirely with dapsone, were assessed clinical!y, bacteriological!y and histol ogicaUy . In aU 12 the disease showed ful! clinicaI response to therapy , although three patients remained smear positive, and two of these still suffered from mild eryt hema nodosum lepros um. However, by mouse foot pad inoculation it was shown that seven of the 12 patients stil! harboured viable My co. leprae. Thus bacterial multiplication was ob tained in mice inoculated with 10 of 37 tissue suspensions prepared from extensor skin (4), striated musc1e (3), peripheral nerve (2) and smooth musc1e (I), although the numbers of positive foot pads in each group of mice were smaU, in keeping with the minute numbers of leprosy bacilli, of variable viability, inoculated. No bact erial enhancement was obtained in thy mectomised-irradiated mice, and three of six strains died out on passage; these findings recalling the difficulties encountered by McCune et ai. in culturing Myco bacterium tuberculosis in vitro from tuberculous mice subjected to effective chemotherapy. Three of these strains of My cobacterium leprae (two from skin and one from nerve) frem separate patients, were shown to be ful1y sensitive to dapsone. The importance of these findings is discussed, especial!y with regard to clinicaI relapse of leprosy after premature stopping of treatment and to the total duration of dapsone therapy required in lepromatous leprosy.