Viability of Mycobacterium leprae in skin and peripheral nerves and persistence of nerve destruction in multibacillary patients after 2 years of multidrug therapy.

The pathological changes, bacterial load, and viability of Mycobacterium leprae in the skin and nerves of nine lepromatous leprosy patients who had undergone 2 years of multidrug therapy (MDT) were studied. M. leprae and varying amounts of their remnants were present in the nerves and skin of all but one patient. M. leprae isolated from skin biopsies of six patients and nerve biopsies of nine patients were inoculated into mouse foot pads. No growth was obtained from any one of them. During the electron-microscopic examination of three nerve biopsies, only one specimen showed a small number of solid-staining M. leprae. These findings would explain the low relapse rate in patients treated with 2 years of fix-duration MDT. Results of a long-term follow up of patients is awaited with interest. The possibility of nerve paralysis due to intraneural microreaction and fibrosis consequent to the continued presence of dead bacterial remnants should be seriously considered.