Bactericidal Action of Streptomycin

Abstract

Streptomycin was bactericidal for both multiplying and non-multiplying cultures of Klebsiella pneumoniae, but not for washed spores of Bacillus sp. #290 whose vegetative cells were inhibited by very low conens. of this antibiotic substance. K. pneumoniae cells, surviving the bactericidal effect of 0.25 U. of streptomycin per ml. after 6 hrs.'' incubation, were more resistant to its action. This resistance persisted through 4 subcultures in the absence of streptomycin and could be increased 5-fold by serial transfers in broth containing it. Washed organisms surviving after 5 hrs.'' incubation with 7.5 U. of streptomycin per ml. were not more resistant.