Antimycobacterial activity in vivo of LM427 (rifabutin)

The activity of the rifampin derivative rifabutin (ansamycin; LM427) was tested in vivo against experimental infections of mice with members of the Mycobacterium avium complex (MAC) and a highly virulent strain of Mycobacterium tuberculosis. Rifabutin was moderately effective against an environmental serotype 8 strain of MAC and of significant effectiveness against low dose aerogenic infections with two strains of higher virulence. The drug was also highly effective in causing the rapid resolution of an intravenous M. tuberculosis infection. These data thus contest a previous negative report on the activity of rifabutin in mouse models of M. avium complex.