Effect of Streptomycin on the Metabolism of Certain Mycobacteria

Abstract

Resistance to streptomycin was induced in Mycobacterium tuberculosis No. 607 by successive passage in Long''s medium containing increasingly higher concns. of the drug. Suspensions of the resistant strain and the normal parent strain were prepd. from 3-day cultures on Long''s medium. The bacteria were resus-pended in [image]/20 phosphate buffer pH 6.7 so that 1 ml. of buffer contained 0.1 ml. of the packed centrifuged organisms, and 0.5 ml. of this suspension was used in each Warburg vessel, which contained a final volume of 2 ml. Ten [gamma] of streptomycin completely inhibited the oxidation of 1 mg. of benzoic acid by the normal strain, whereas 100 [gamma] was without effect on the oxidation by the resistant strain. The oxidation of pyruvic acid by the normal strain as well as its oxygen uptake without added substrate was not affected by 100 [gamma] of streptomycin. This indicates that the inhibition of benzoic acid oxidation by streptomycin may be fairly specific. However, the increased oxygen uptake of the virulent H37 strain in the presence of benzoic acid was not affected by 300 [gamma] of streptomycin. Other mechanisms must, therefore, be inhibited in this pathogenic strain.