Oganomycin GA is a fermentation product from the bacterium Streptomyces (Streptomyces str. oganonensis YG 19Z). By introducing sodium p-hydroxycinnamate into the fermentation medium, Oganomycin A is produced. Under the influence of D-amino acid oxidase, Oganomycin A is converted into the glutaric acid derivative Oganomycin GA, which exhibits greater efficacy against Gram-negative bacteria than against Gram-positive bacteria.