Cultivation of M. leprae

A peculiar yeast-like microorganism, isolated from leprous lesions, was discovered to produce the growth promoting factor for M. leprae. From the mass culture of this organism, the oil substance stimulating M. leprae growth was extracted with hot acid ethanol and purified using organic solvents. The final product was considered to be a kind of siderophore. When inoculating M. leprae on the special solid medium, contained chemically defined materials and supplemented with the growth factor, and incubating for 7 days in 35-36 degrees C, light yellow R type colonies were observed. The colony was composed of the acid fast bacilli which were morphologically indistinguishable from bacilli in the tissues. Successive cultivation of the bacilli was possible only on the special medium used but not on the ordinary media for general mycobacterial species. The whole identification studies are not yet finished, however, the cultivated organism was expected as M. leprae from several view-points including the high frequency of positive cultures.