[Directed screening of aminoglycoside antibiotic producers on selective media with gentamycin].

The method of directed screening of aminoglycoside antibiotics is based on the natural phenomenon that fresh isolates of Micromonospora are highly resistant to the antibiotics produced by them. The method consists of plating of the soil samples on selective media with gentamicin (10--25 micrograms/ml). The frequency of Micromonospora against the total number of the isolated actinomycetes increased from 3.3--11.4 to 30.6--78 per cent. The number of the cultures isolated from the control medium and active against gramnegative test-bacteria amounted to 13.4 per cent, while the number of Micromonospora isolated from the selective medium with gentamicin and active against gramnegative test-bacteria amounted to 69.4 per cent. 37 crude antibiotics were isolated with the method of ion exchange concentration usually used for aminoglycoside antibiotics. The new antibiotics were identified as 2-desoxy amine-containing aminoglycosides by cross resistance of aminoglycoside resistant strains of Staphylococci to them, the methods of paper and thin-layer chromatography and mass spectrometry. The majority of the aminoglycosides belonged to the gentamicin group. 2 compounds with molecular weights not described in the literature for aminoglycosides were isolated.