ANTIMYCOBACTERIAL SYNERGISM OF CLARITHROMYCIN AND RIFABUTIN

Clarithromycin and rifabutin are among the most promising drugs for th e therapy of infections caused by Mycobacterium avium or other atypica l mycobacteria. Since synergism of combined drugs is important in orde r to achieve strong antimycobacterial activity, the combined inhibitor y effects of antibacterial agents should also be investigated when age nts are evaluated for possible use in antimycobacterial drug therapy. In the present study we examined the antimycobacterial activity of cla rithromycin, rifabutin, and their combination against 51 clinical isol ates of the M. avium complex from patients with acquired immune defici ency syndrome (AIDS) with disseminated mycobacteriosis. A concentratio n-dependent inhibition was seen for each drug. The antibacterial effec t was significantly more pronounced for the combined drugs than for th e agents tested separately. Synergism, against up to 88% of the strain s tested, mas seen for the tested drugs combined at different concentr ations. All 51 M. avium strains mere susceptible to the combination of 4 mg/l clarithromycin and 2 mg/l rifabutin.