Cultivable precursors of Mycobacterium leprae

During attempts at test tube culture of M. leprae in our laboratory we have repeatedly isolated a non-acid fast, coccoid organism from lepromatous tissue and skin smears (Chatterjee, 1976). These organisms show a tendency to generate acid fast mycobacteria in test tube passages and in mice experimentally infected with these organisms, and a number of stable, pigmented mycobacterial cultures have been obtained from them that are being maintained in test tube media. In the first report cited above it was postulated that these coccoid organisms of leprous origin were a cultivable precursor phase of the non-cultivable M. leprae, and further that M. leprae was a pleomorphic organism that has a cultivable non-mycobacterial phase (Chatterjee, 1978). Since these reports, further studies have been made on these precursor organisms, as well as mycobacteria that either grew out of the coccoid precursors, or isolated in pure culture form lepromatous tissues and appeared to be identical. This paper deals with the biochemical and drug sensitivity patterns, and infectivity in experimentally inoculated mice, of a few of these non-acid fast coccoid strains, and their mycobacterial progenies, i.e, mycobacterial converts from the coccoids, and a few mycobacterial strains isolated straight away from lepromatous nodules that showed quite identical characteristics.