Development of Streptomycin Resistant Strains of Tubercle Bacilli in Pulmonary Tuberculosis: Results of Simultaneous Sensitivity Tests in Liquid and on Solid Media

Abstract

Simultaneous sensitivity tests in liquid and solid media were run on the tubercle bacilli from the sputum of 18 patients. All had acute progressive disease treated with streptomycin. Herrold''s glycerol egg-agar medium, pH 7.3, and Tween 80-albumin medium were the solid and liquid media employed. More streptomycin was required to inhibit growth in the solid than the liquid medium, initially 0.5 or 0.25 ug. usually inhibited growth in liquid medium and 4 ug. or more was required by the solid. In all cases some degree of resistance appeared and persisted during the 6 mos. of therapy. In 10 of the 18 cases, resistance was maintained at a low degree, the remaining group demonstrated a change from low to high degree of resistance. Bacilli count dropped during the phase of sensitivity, but rose following the development of resistant strains. All strains of tubercle bacilli showed about equal tendency to become resistant to streptomycin. In the type of cases studied, resistant strains developed within 60 days of streptomycin treatment; the persistence of a truly sensitive strain after this is improbable.