I'KonrCTION OF ANTIHI()TI("S 



239 



>^^-o— AA/^ — o — W — o 



8 



UNITS 



10 

 OF 



12 14 (6 20 



ANTIBIOTIC / mi 



i— AW ' 



40 60 



Figure 91. Effect of antibiotic concentration on development of resistance by E. roli in agar media: 

 D, Streptomycin; O, Grisein; A, Streptomycin + 1 unit grisein/ml; X, Streptomycin + 5 units gri- 

 sein/ml. (Reproduced from: Reynolds, D. M. and Waksman, S. A. J. Bacteriol. 55: 749, 1948). 



tain general properties that may he summa- 

 rized as follows : 



1 . They inhibit the growth of a wide range 

 of fungi, including yeasts, hut are inactive 

 against bacteria. 



2. They show a relatively high toxicity 

 when injected into animals, but are much 

 less toxic when gi\'en by mouth. 



3. They are of low solubility in water, dis- 

 solve more readily in a(iueous solutions of the 

 lower alcohols, and are easily solul)le in aciue- 

 ous pyridine. 



4. They exhibit characteristic ultra \'iolet 

 al)sorpti()n spectra typical of polyenic chro- 

 mophores (Table ()()). 



\'anek d al. (1958) isolated from soil sam- 

 ples obtained from China a total of 739 ac- 

 tinomycetes; of these, 515 (()9.7 per cent) 

 were antil)iotically active. A total of 386 cul- 



Table 66 



Classijication of polyene antibiotics according to 

 their ultraviolet absorptions (Ball et al.) 



