ANTIBIOTICS AND CHEMICAL DISINFECTANTS 219 



A few antibiotic agents are fairly nontoxic to the animal body ; others are 

 somewhat more toxic but can still be utilized; and some are so highly 

 toxic that they offer little promise as chemotherapeutic agents. 



Antibiotic agents differ greatly in their solubility : some are water soluble ; 

 others are alcohol soluble and only slightly soluble in water; and 

 some are acids and react with alkali solution to form soluble salts. 



Some antibiotic agents are stable under a variety of conditions, whereas 

 others are unstable. 



Some antibiotic substances are hemolytic, others have apparently no in- 

 jurious effect upon blood cells. The latter can be used for general 

 body treatment, whereas the former are suitable only for local ap- 

 plications. 



Since antibiotic substances are selective in their action upon microorgan- 

 isms, none can be expected to be utilized as general agents against all 

 bacteria. This also points to the remarkable physiological differences 

 in the morphology and physiology of bacterial cells, and to the dif- 

 ferences in mode of action of the different antibiotics upon various 

 bacteria. 



A comparison of the antibacterial action of the antibiotic substances 

 produced by two bacteria will serve to illustrate some of the foregoing 

 points. Pyocyanin, produced by Ps. aeruginosa, inhibits the growth of 

 many gram-positive and gram-negative bacteria in dilutions as high as 

 I : lOOjOOOj pyocyanase and hemipyocyanin have less activity upon the 

 bacteria, but yeasts are more sensitive to them than to pyocyanin. Ty- 

 rothricin, produced by B. brevis, is far more specific in its action, which 

 is limited largely to gram-positive bacteria. The sensitivity of patho- 

 genic fungi to these compounds also differs markedly. Some other 

 striking differences are found on comparing two types of antibiotic sub- 

 stances produced by fungi, namely, penicillin and clavacln, and two 

 substances produced by actlnomycetes, namely, streptothricin and ac- 

 tlnomycln. The bacteriostatic spectra of these four substances are re- 

 corded In Table 't^S- The first of each pair has limited toxicity to ani- 

 mals, and the second is highly toxic. Whereas penicillin acts largely 

 upon gram-positive bacteria and only upon a few gram-negative organ- 

 isms, streptothricin acts alike upon certain bacteria within each group. 

 Clavacln and actlnomycin, both of which are highly toxic, differ simi- 

 larly In their action upon bacteria, the first being largely active against 



