Experimental Observations on the Antimycobacterial Activity of Rifampin

Abstract

Experimental studies in vitro and in vivo indicated that rifampin is highly active against both isoniazid-susceptible and isoniazid-resistant strains of M. tuberculosis. Although less active in vivo than isoniazid, at least in the dosages employed, it was highly active in combination with streptomycin, isoniazid, or ethambutol, or in combination with both streptomycin and isoniazid, against experimental tuberculosis in mice produced by intravenous challenge with the H37Rv strain of M. tuberculosis. Emergence of microbial resistance to rifampin was not observed during a 3-week course of treatment nor during a 3-week followup period after cessation of therapy. Antagonism, moreover, between rifampin and streptomycin, isoniazid, or ethambutol was not observed.