CHAPTER 10 



CHEMICAL NATURE OF ANTIBIOTIC SUBSTANCES 



Antimicrobial agents are of either chemical or biological origin. The 

 first comprise inorganic (heavy metals, halogens) and organic (phenols, 

 arsenicals, dyes, aromatic oils) compounds. The second include a variety 

 of products of higher plants (quinine, chaulmoogra oil, wheat flour pro- 

 tein, allicin), higher animals (lactenin, lysozyfne), and microorgan- 

 isms, to which the term "antibiotic" Is specifically applied. 



The property possessed by culture filtrates of many bacteria of inhib- 

 iting the growth of bacterial cells has long been recognized. The sug- 

 gestion has even been made that all bacteria, when tested at the right 

 age and under proper conditions of culture, are able to produce anti- 

 bacterial substances (71). It is now definitely established, however, 

 that this property Is characteristic of only certain strains of specific bac- 

 teria, fungi, and actinomycetes. 



The production of antibiotic substances by microorganisms is influ- 

 enced by the strain of the organism, composition of the medium, incu- 

 bation temperature, age of the culture, aeration, and certain other 

 factors. 



The more Important antibiotic substances are described briefly in 

 Table 32. They may be classified on the basis of their origin from spe- 

 cific microorganisms, their chemical properties, or their biological ac- 

 tion. Differences between various compounds may often be in degree 

 rather than In kind. Different organisms may produce the same anti- 

 biotic j frequently the substance may show minor variations from the 

 general type, these variations being both chemical and biological. Some 

 organisms are able to produce more than one antibiotic: B. brevis pro- 

 duces tyrocldlne and gramicidin j P. notatum, penicillin and penatin; 

 A. fumigatusy fumlgatin, fumlgacin, splnulosin, and gllotoxinj A. 

 fiavusj aspergilllc acid and penicillin. 



Since the name of an antibiotic often designates only a crude prepara- 

 tion, considerable confusion has arisen because different names have 

 been given to the same preparation, or the same name has been applied 



