Use of NASBA RNA amplification for detection of Mycobacterium leprae in skin biopsies from untreated and treated leprosy patients.

This study was performed to assess the value of NASBA RNA amplification of a 16S rRNA target for the detection of presumably viable Mycobacterium leprae in sections of skin biopsies from leprosy patients. The NASBA positivity rate was 90.4% (84/93) for untreated multibacillary (MB) patients [bacterial index (BI) > or = 2] and 16.7% (8/48) for the untreated paucibacillary (PB) patients (BI < 2). NASBA positivity showed a good concordance with the presence of solidly stained M. leprae [morphological index (MI)] in skin biopsies from leprosy patients, but no relationship could be demonstrated between the strength of the NASBA signals and the BI. Furthermore, the usefulness of the detection of 16S rRNA by NASBA to monitor the efficacy of leprosy treatment was investigated using an additional 154 biopsy specimens analyzed from 80 MB patients during the course of treatment. The NASBA positivity rate declined during treatment. A significant decrease was observed after only 1-3 months. These results favor the view that detection of RNA by NASBA may reflect the viability of M. leprae.