262 DISEASE CONTROL 



faradysenteriae. These studies led to the development of pyocyanase 

 preparations of varying degrees of activity. Pyocyanase has been used 

 in the treatment of a variety of diseases including diphtheria and men- 

 ingitis. In some of these cases, especially of anthrax, treatment was 

 rather successful (278), in others it was not, due largely to the low 

 potency of the product (529, 801). 



The lack of recognition of the existence of more than one antibiotic 

 agent in the culture of Ps. aeruginosa led to the disrepute of pyocyanase. 

 It was soon reported (69), for example, that a Berkefeld filtrate of the 

 culture had only a weak therapeutic effect, an observation later con- 

 firmed by Wagner (938). The facts that some strains of Ps. aeruginosa 

 do not form any pyocyanase and that even active strains may lose the 

 capacity to produce this antibiotic (529) were other contributing factors 

 to the gradual disappearance of pyocyanase as a chemotherapeutic 

 agent. 



Various methods of treating severe infections, like anthrax or ma- 

 lignant tumors, with mild infective agents have been suggested. The 

 reduction in pathogenicity of one organism by the presence of others 

 has thus been well recognized. Nonpathogenic organisms apparently 

 have specific effects upon the pathogens, the development of which was 

 prevented or even suppressed. The very occurrence of specific types of 

 pneumococci in healthy individuals and the causation of specific forms 

 of pneumonia were found to be controlled by the antagonistic effects of 

 other microorganisms (371). 



It was thus definitely established that the growth of B. anthracis 

 could be inhibited by antagonists (49). Guinea pigs survived large in- 

 jections of washings from soil previously contaminated by B. anthracis 

 through the slaughtering of a diseased cow. When cultures of this or- 

 ganism were isolated from the soil and injected, however, characteristic 

 disease symptoms resulted. It was suggested that the anthrax spores are 

 digested by the leucocytes which have been attracted to the site of in- 

 jection by the accompanying bacteria (32). 



Seitz (849), in discussing the problem of mixed infections, cited 

 many cases not only of decreased but also of increased virulence of the 

 pathogen as a result of accompanying bacteria. He warned, therefore, 

 against too sweeping generalizations concerning the healing effect of 



