Viability of Mycobacterium leprae in lepromatous patients after five years of dapsone monotherapy supplemented with two years of multidrug therapy.

ABSTRACT

Eleven lepromatous leprosy (LL) patients with a bacterial index (BI) of three and above who had undergone two years of multidrug therapy (MDT) and yet had positive skin smears at the end of treatment were chosen for this study. Biopsies from the skin and lymphnodes were histopathologically evaluated for the presence of granulomas and M. leprae. M. leprae isolated from the skin and lymphnodes were inoculated into the foot-pads of normal mice to test their viability. On histopathological examination of the biopsy specimens, it was found that granulomas and M. leprae were present in the skin and lymphnode biopsies of all patients except two, in whom, although granulomas persisted, M. leprae were not found in skin biopsy specimens. No growth was obtained in the foot-pads of mice inoculated with organisms isolated from skin and lymphnode biopsies of all 11 patients indicating a near complete bacterial kill. That would account for the extremely low relapse rates reported until now in LL patients who had undergne two years of MDT.