ANTIBIOTIC SUBSTANCES 243 



chronic mastoiditis, and acute and chronic sinusitis. The substance does 

 not damage the tissue or interfere with wound healing. The growth of 

 most staphylococci, streptococci, and pneumococci is inhibited or the or- 

 ganisms are killed. When applied locally, tyrothricin does not reach 

 the blood stream. It has also been found that tyrothricin has an excellent 

 therapeutic effect when used for urethral irrigations in the male (187). 



Tyrothricin possesses several limitations, from the point of view of 

 practical utilization: (a) development of bacterial, notably staphylococ- 

 cus, variants, which become resistant to this agent 5 (b) inhibition of its 

 action by phospholipinsj (c) hemolytic action, which prevents its intra- 

 venous use. 



Tyrothricin was found to produce no lesions in the gastro-intestinal 

 tract (728, 968), but it is not very active when administered by mouth, 

 since it is destroyed by the proteolytic enzymes of the digestive system. 



Streftothrkin 



The fourth agent that was found to offer practical possibilities is 

 streptothricin. This agent gave favorable results for the treatment of 

 Br. abortus grown on chicken egg embryos. Its toxicity is low enough 

 to make possible the administration of doses sufficient to destroy this 

 pathogen in the living tissues (Table 45). Both the in vitro and the in 

 vivo activities of streptothricin against gram-negative bacteria sug- 

 gested the probability that it will prove useful in the local treatment of 

 infected wounds and burns, bacillary dysentery, typhoid fever, and food 

 poisoning produced by Salmonella organisms (755, 756a). 



Other Agents 



The protective action of the specific enzyme (polysaccharidase) of a 

 soil bacterium against type III pneumococcus infection has also been 

 established (30, 293). The specific protection induced in experimental 

 animals is determined by the nature of the polysaccharide of the pneu- 

 mococcus type. The polysaccharidase destroys the protective capsular 

 substance of the pneumococcus, thus rendering it susceptible to phagocy- 

 tosis. 



The possibility of utilizing antagonistic bacteria for the control of 

 fungi causing skin infections has also been suggested (119). 



