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Experiences and methods in the search for new antibiotics

, : Experiences and methods in the search for new antibiotics. Journal of Hygiene, Epidemiology, Microbiology, and Immunology 1(4): 397-412

After isolating actinomycetes from samples of soil, a centrifugation method was elaborated, permitting the easy and rapid separation of the actinomycetes from other microorganisms. The antibiotic spectrum of the isolated actinomycetes was determined by a block method on agar. After determining the solubility of unknown antibiotics, a papergram method was elaborated, using a system of 10 solvents. The ionic character of inknown antibiotics was first determined by block tests on agar plates containing ion exchangers. A plate test method was elaborated for determination of dialyzing properties. Studies on resistant bacteria were conducted and the method used, noted above, entailed agar blocks bearing the mature actinomycete. From 739 strains recovered from soil from South China, antibiotic activity was demonstrated in 515 (69.7%). Of these, 43.7% were active against Sarcina lutea, 36.4% against Bacillus subtilis, 23.8% against Staphylococcus, 7.8% against Escherichia coli, 5.8% against Pseudomonas aeruginosa and 5.5% against Serratia marcescens; 20-30% were active against fungi and yeasts, the most sensitive of which was Rhizopus nigricans. The actinomycetes were divided into 5 groups in relation to antibiotic production against: gram-positives; gram-positives, yeasts and fungi; gram-positives, gram-negatives, yeasts and fungi; yeasts and fungi only, and bacteria only. Forty-eight percent inhibited gram-positives, yeasts and fungi. Since the number of antibiotics which inhibit both bacteria and fungi is small, it was assumed that the secreting organisms in this series produced largely mixtures of antibiotic substances. Of the 515 antibiotic strains isolated, 386 produced more than 1 antibiotic. Polyene antibiotics were determined by UV absorption spectra, etc. 50.5%,produced an antibiotic of a polyene character, and most of these were heptenes (89.9%) with occasional hexenes (0.5%), pentenes (2.6%), tetrenes (3%), a mixture of hexenes and tetrenes (1.0%) and a mixture of heptenes and pentenes (3.0%), 40.1% formed antibiotics which were water-soluble, most probably belonging to the streptothricin group; 15.3% of these belonged to the aetinomycin group (orange pigment, etc.); 7.3%. were non-polyene in character and had anti-fungal activity; 21.4% were not identified. Two crystalline aetinomycin preparations were isolated (B and 154), the crystalline preparation picromycin, 2 antibiotics with a high molecular weight (BU 271 and BU 306), antibiotic BU 607, which resembles actinoleukin, and antibiotics BU 943, which is of heptene type.


PMID: 13525741

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