MICROBES man's MIGHTY MIDGETS 45 



cations of the basic techniques developed for the manufacture of penicillin. 



The second major antibiotic was discovered by S. A. Waksman and 

 represented the first of a lengthening list of drugs derived from the Actino- 

 mycetes, a n^oup of soil microorganisms superficially intermediate between 

 the bacteria and the mold fungi but with true bacterial affinities. Strepto- 

 mycin is produced commercially by selected strains of Streptomyces griseus 

 and has been available to physicians since 1946. Like penicillin, it is cur- 

 rently manufactured in large quantities. The annual production of the drug 

 is in the neighborhood of 450,000 pounds, with a wholesale valuation of ap- 

 proximately $36 million in 1955. It finds important uses in combating dis- 

 eases caused by gram-negative bacteria that are unaffected by penicillin; its 

 greatest application is in the treatment of tuberculosis. However, nerve and 

 kidney toxicity limit its usefulness somewhat, and even more than penicillin, 

 it tends to promote the development of drug-resistant pathogens. In common 

 with penicillin, it is ineffective against the rickettsiae and viruses, hence it 

 narrows but does not remove the area of uncontrolled infections. 



Following the discovery of streptomycin, particular attention was centered 

 upon the actinomycetes as possible sources of additional new and valuable 

 antibiotics. Five new drugs of major importance have been discovered. 

 Whereas these have different characteristics which often commend them for 

 specific applications, they possess to a considerable degree common curative 

 properties. All of them are active against both gram-positive and gram-nega- 

 tive bacteria and, in addition, have proved quite effective in combating dis- 

 eases caused by the rickettsiae (e.g., typhus fever and Rocky Mountain 

 spotted fever). They are referred to as broad-spectrum antibiotics because 

 of the wide range of microorganisms that they inhibit. 



The first of these newer drugs, Chloromycetin (chloramphenicol) was dis- 

 covered independently by two research teams in 1947. It was developed and 

 is now manufactured in quantity by Parke, Davis and Company. It has 

 particular merit in the treatment of typhoid fever, bacillary dysentery, and 

 other intestinal diseases. A chemical synthesis was early achieved for this 

 drug, and it can be produced alternatively by synthetic processes or by 

 fermentation. The actinomycete used for its production by fermentation 

 processes is 5. venezuelae. 



The second antibiotic of this series, aureomycin (chlortetracycline) was 

 discovered in 1948 by B. M. Duggar of the Lederle Laboratories. It is inter- 

 esting to recall that this was accomplished after the retirement of this emi- 

 nent mycologist and plant physiologist from his academic position at the 

 University of Wisconsin. Aureomycin is produced by the actinomycete S. 

 aureojaciens. It is manufactured in large amounts and finds important ap- 

 plications in the treatment of a wide range of different diseases caused by 

 gram-negative and gram-positive bacteria, rickettsiae and the larger viruses, 



