282 DISEASE CONTROL 



enabled the animals to survive. The injection of lo mg. of tyrothricin 

 into the pleural cavity of normal rabbits produced certain local tissue re- 

 actions. More than lO mg. produced adhesions, thickening of the 

 pleura, sterile abscesses, and other disturbances (753). 



The susceptibility of fecal streptococci to tyrothricin varies from 

 strain to strain. Oral administration of the substance may produce in- 

 hibition of the growth of streptococci in the intestines of mice. This 

 inhibition was most readily demonstrated when sulfasuxidine was ad- 

 ministered together with the tyrothricin (799). Application of tyrothri- 

 cin to ulcers brought about sterilization and healing of local infections. 

 Application to the mastoid cavity following mastoidectomy also gave 

 favorable results. In staphylococcic infections, resistant strains may de- 

 velop during therapy. Certain sulfonamide-resistant strains of S. 

 pyogenes were eradicated by application of gramicidin (291). 



Tyrothricin and tyrocidine exert a bactericidal effect, and gramicidin 

 is largely bacteriostatic (Figure 28) j the first two are affected by blood 

 and serum, but not the last. In order to be effective against bacteria, 

 the organisms must be in contact with the material (790). Gramicidin 

 is more toxic than tyrocidine, the toxic dose being larger, however, than 

 the dose necessary to kill most gram-positive cocci. 



Both tyrothricin and tyrocidine cause hemolysis of erythrocytes, and 

 both are leucocytolytic, gramicidin being less so. Both tyrothricin and 

 gramicidin cause local and general toxic effects when injected into closed 

 cavities of the body. Small amounts may bring about the sterilization of 

 local infections without producing general toxic effects, giving only 

 minimal local reactions. When injected into the skin, tyrothricin and 

 gramicidin produce local reaction, the latter to a lesser degree. Oral ad- 

 ministration is ineffective in reducing or destroying organisms which are 

 susceptible in vitro. Local application of these substances has not been 

 attended by toxic reactions even when large amounts were applied 

 (758). Tyrothricin in high concentrations caused cytoplasmic and nu- 

 clear disintegration of the exudative rabbit polymorphonuclear leuco- 

 cytes} in lower concentrations, it brought about altered staining reac- 

 tions. When there was no apparent microscopic injury to the cells, 

 phagocytosis of pneumococci took place. The presence of serum brought 



