An antibacterial antibiotic was isolated from the culture filtrate of Streptomyces thaeochromogenes R-719. The antibiotic, which is basic in nature, has a broad antibacterial spectrum, though the minimum inhibitory concentrations are in the order of 10 mcg/ml. Such antibacterial spectrum and the physicochemical properties suggested that the antibiotic differs from those previously known. Later, another antibiotic, quite related to the above in both chemical and biological properties, was found to be produced in the same culture filtrate. The former antibiotic was designated as kikumycin A and the latter, kikumycin B.

This paper describes the taxonomy of the kikumycin-producing strain, production and purification of kikumycins A and B, and characterization and biological properties of the antibiotics.

A new antibiotic of macrolide group was isolated from fermentation broth of a strain of Streptomyces flavochromogenes, R-903 in our culture collection. The antibiotic is a white, basic, needle crystal and shares several common properties with angolamycin, which was discovered by Corbazet al. in 1955¹⁾. Further studies on the production of our antibiotic resulted in the discovery of related antibiotic in the same culture fluid. Thus the major component, found earlier and related to angolamycin, was designated as shincomycin A and the minor one, which is quite different from either angolamycin or shincomycin A was designated as shincomycin B. This paper presents characteristics of Streptomyces R-903, isolation and properties of shincomycin A. Isolation and characteristics of shincomycin B will be reported elsewhere⁶⁾.