In-Vitro Activity of Erythromycin against Atypical Mycobacteria

Two hundred and eleven strains of atypical mycobacteria were examined for susceptibility to erythromycin by the proportion method, in Middlebrook 7H-10 agar (pH adjusted to 7.1). All strains of Mycobacterium kansasii, Mycobacterium terrae, Mycobacterium triviale, Mycobacterium borstelense, and tap water scotochromogens were inhibited by 0.5-2 μg/ml of the drug. Eighty-four percent of the strains of Mycobacterium scrofulaceum were susceptible to 0.5-2 μg/ml; the other strains were inhibited by 4-16 μg/ml. Strains of Mycobacterium intracellulare and Mycobacterium gastri varied considerably in susceptibility to erythromycin. Nearly all strains of Mycobacterium f ortuitum were resistant to the drug. The results of this study suggest that erythromycin may be a valuable drug, when used alone or together with other tuberculostatic compounds, for the treatment of some types of atypical mycobacterial infections.