Viability and drug sensitivity of M. leprae isolated from long-term WHO/MDT treated multibacillary leprosy patients.

The ALERT Leprosy Control Programme introduced WHOIMDT in Ethiopia in January 1 983 . Paucibacillary patients are treated for 6 months with self-administered daily dapsone and rifampicin once monthly under supervision. Multibacillary patients are treated for a period of at least 2 years or until the skin smears become negative. Treatment consists of self-administered dapsone, clofazimine and rifampicin and clofazimine monthly under supervision. In 1 990, the ALERT leprosy control and the ALERT Hospital Services observed multibacillary patients who were suspected to be unresponsive to the WHOIMDT regimen. The basis of this concern was that by the yearly skin slit examination, the bacteriological index (BI) did not decrease by 1 log unit per year, despite adequate compliance and above 80% attendance rate, with the WHO-recommended MDT. Using the mouse foot pad assay system, we tested for viable bacilli from some of these patients from 1 992 to 1 993 .