Multivariate analysis of the activity of rifamycins against rapidly growing Mycobacteria, to define an in vitro screening model for their activity against mycobacterium leprae.

In an attempt to select a group of rapidly growing Mycobacteria which could serve as a model for the in vitro screening of rifamycin derivatives for their activity against Mycobacterium leprae, the MIC values of 237 strains of rapidly growing Mycobacteria were determined for 4 reference rifamycins with known activity against M. leprae and 19 rifamycins with unknown activity against M. leprae. Study of the results by a multivariate statistical technique, the principal components analysis, defined a group of 16 rapidly growing Mycobacteria (7 strains of M. phlei, 4 strains of M. thermoresistible, 3 strains of M. fortuitum and 2 strains of M. vaccae) showing the lowest distance to M. leprae. The analysis detected among rifamycin derivatives with different activities M. tuberculosis, compounds which should be active against M. leprae, and allows the selection of a limited number of rifamycins for the in vivo screening in the mouse model.