Zoiie.s of inhibition in mm. 



asiiin.st gram-positive and gram-negative 

 l)acteria, rickettsiae, and tlie larger viruses. 



Tetracyclines 



The tetracyclines comprise a group of 

 compounds that have found an important 

 place in the therapy of numerous infectious 

 diseases. They are amphoteric substances, 

 forming crystalline hydrochlorides and so- 

 dium salts. 



The first of the tetracyclines, chlortetra- 

 cycline, was isolated in 1948 by Duggar et al. 

 The culture producing this antibiotic was 

 designated as *S'. aureofaciens. Like chloram- 



phenicol, it inhibits the growth of gram-posi- 

 tive and gram-negative bacteria, rickettsiae, 

 and certain of the so-called larger viruses. 



Oxytetracycline was isolated, in 1950, by 

 Findlay et al. from a culture of S. rimosus. 

 Tetracycline can be obtained either by direct 

 fermentation of media low in chlorides by S. 

 aureofaciens or by the chemical modification 

 of chlortetracycline. In some respects, it ap- 

 pears to ha\'e more desirable properties than 

 the other tetracyclines. 



The anhydro derivative of chlortetracy- 

 cline was found to be particularly effective 

 against actinomycetes (Goodman et al.). 



