Streptomycin, a Substance Exhibiting Antibiotic Activity Against Gram-Positive and Gram-Negative Bacteria.* 

A new antibacterial substance, designated as streptomycin, was isolated from two strains of an actinomyces related to an organism described as Actinomyces griseus. This substance resembles streptothricin in its solubility in water, mode of isolation and concentration from culture medium, its selective activity against gram-negative bacteria, and its limited toxicity to animals. However, the two substances differ in the nature of their respective bacteriostatic spectra as well as in their quantitative action upon different bacteria. It is suggested that one is dealing here with two closely related chemical compounds.