Chemical Studies on Antibiotic Substances Ii. On Streptothricin Bi and Bii.

1), during their experiment of classifying antibiotic streptomyces on the basis of antibacterial spectra, found that one group of strains produced an antibiotic which was extracted by streptothricin extraction process, and that to this antibiotic, streptothricin-fact E. coli was found to be more resistant than the normal culture. But, this antibiotic was different from streptothricin in the relative resistances of B. subtilis and B. anthracis. The antibiotic of this group of strains which were recognized to be belonging to Strcptomyces fradiae was named streptothricin B. Simultaneously they found that the antibiotic substances, similar to streptothricin produced by S.lavocndulae in the antibacterial spectrum and in the later-appearing toxicity, are produced also by various other kinds of streptomyces. Therefore, they named those antibiotics streptothricin A group substances.