A comparison of the bactericidal activity of a series of rifampicins against Mycobacterium leprae.

The bactericidal activity against Mycobacterium leprae of six 3-(4-methylpiperazin-1-yl-iminomethyl)rifamycin SV (rifampicin) derivatives was compared with that of rifampicin in a modified proportional bactericidal test, using a smaller number of experimental animals and allowing the administration of a single dose of the drugs. No correlation was found between the in vitro activity of the rifamycin derivatives against M. tuberculosis or rapidly growing Mycobacteria in vitro and the activity against M. leprae in he mouse. The procedure is valuable for the screening against M. leprae of very potent bactericidal drugs available in only small quantities.