Production of 



Antibiotics by Actinomycetes 



During the last 14 years, more than 100 substances and preparations 

 which possess antibiotic properties, i.e., have the capacity to inhibit the 

 growth of and even to destroy various microorganisms, in dilute solutions, 

 have been isolated from cultures of actinomycetes. Most of them have 

 been isolated from the culture broth, and a few from the mycelium. These 

 antibiotics vary greatly in their physical and chemical properties, their 

 antibiotic spectra, their toxicity to animals, and their chemotherapeutic 

 utilization. Some have very wide spectra, being active against bacteria and 

 fungi, or gram-positive, gram-negative and acid-fast bacteria, or bacteria 

 and larger viruses; some have somewhat narrower spectra, being active only 

 against certain gram-positive bacteria or yeast-like fungi ; still others have 

 very narrow spectra, and are active only or largely against limited groups 

 of organisms, such as mycobacteria or certain few viruses. Antibiotics vary 

 in their antimicrobial action not only qualitatively but also quantitatively, 

 one antibiotic being many times more active against a certain organism 

 than is another antibiotic. 



About 10 antibiotics produced by actinomycetes have already found 

 application in chemotherapy, i.e., in treatment of human and animal in- 

 fections. These include streptomycin and its derivative dihydrostreptomy- 

 cin, chloramphenicol, chlortetracycline, viomycin, oxytetracycline, ne- 

 omycin, erythromycin, and carbomycin. They are used in the treatment of 

 a great variety of infections, caused largely by gram-positive and gram- 

 negative bacteria, mycobacteria, rickettsiae, some of the larger viruses, 

 some protozoa, and certain fungi. Some, such as streptomycin and cyclo- 

 heximide, have found application in the treatment of plant diseases. 



The isolation of these antibiotics has been a result of extensive screening 

 programs. Large numbers of cultures of actinomycetes were isolated from 

 soils, composts, river beds, peat bogs, and other natural substrates. 

 They were tested systematically on different media, under different condi- 

 tions of culture, and against different test organisms. Nakhimovskaia (38) 

 and Krassilnikov and Koreniako (33) were responsible for the first screen- 

 ing programs, in 1937 and 1939, respectively. These studies did not yield 

 any true antibiotic, although an enzyme-like preparation ("actinomyces 

 lysozyme") which resulted from them may have contained or actually been 

 an antibiotic substance (34) . The same is true of another preparation ob- 

 tained from a culture of an actinomyces by Gratia and Dath (24) in 1925; 



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