In Vitro and In Vivo Chemotherapeutic Activity of Rifabutin (LM 427) on Mycobacterium avium-intracellulare Complex

Abstract

In vitro chemotherapeutic activity of rifabutin against Mycobacterium avium (-intracellulare) complex was studied with 20 Japanese disease-associated strains. In vitro superiority of rifabutin to rifampin (RMP) was clearly demonstrated in three different kinds of media. A tendency of parallelism in susceptibility of individual strains between rifabutin and RMP was confirmed in a correlation analysis of MICs of the both drugs in Kirchner's liquid medium, but not in a modified Dubos Tween^[○!R] albumin liquid medium. The murine experimental infection with a mouse-virulent strain 31F093T was used to evaluate in vivo activity of rifabutin in comparison with that of RMP with 3 treatment dosages. Rifabutin suppressed moderately the total number of grossly visible lung disease. In the evaluations of consecutive viable bacilli in the organs of mice, neither superiority of rifabutin to RMP, no dose responses of the both drugs were demonstrated. This challenging results could be mostly due to a high resistance of 31F093T strain to rifabutin.