THE BACTERIOPHAGE IN DISEASE 189 



COLON BACILLUS INFECTIONS 



Sometimes the colon bacillus may become pathogenic and 

 may be encountered as the etiological agent in diverse localized 

 infections, or even in septicemias. It at first appears strange 

 that so common an organism, a normal inhabitant of the intestine, 

 should at a particular time develop pathogenicity. There must 

 be "a something" which differentiates the pathogenic B. coli 

 from the banal B. coli. It is this which I have tried to determine. 



Five specimens of infected urine secured from individuals 

 with pyelonephritis have been examined. In all of these cases 

 not only was the colon bacillus present, but there was a mixed 

 culture of B. coli and the bacteriophage, as shown by inoculation 

 of the urine on agar. In one of the cases simple plating of the 

 urine on agar gave a colon culture studded with plaques, in the 

 other four, agar cultures made after a bouillon growth gave the 

 same appearance. The colon bacillus possessed a high resistance, 

 although it was not entirely refractory. Thus the struggle con- 

 tinued in the organism. The ordinary B. coli is not pathogenic. 

 The resistant B. coli becomes so because of its resistance to the 

 action of the bacteriophage. 



The history of a morbid condition is the history of the struggle 

 between the bacteriophage which attacks with its virulence, on 

 one side, and a bacterium susceptible of resistance on the other. 

 Moreover, the struggle can be continued as long as the bacterium 

 secretes products toxic for the infected body, but in the last 

 analysis, it is the issue of this conflict which decides the fate of the 

 individual. 



We will have occasion to return to the case of pyelonephritis 

 when we discuss "carriers." 



TYPHOID FEVER AND THE PARATYPHOID FEVERS 



Several cases of typhoid fever of varied severity have been 

 studied by the same method as that employed in bacillary dys- 

 entery. Fourteen of these were in the Pasteur Hospital for 

 treatment, and of these the stools were examined at least once 

 a day throughout the course of the disease and in convalescence. 

 Fourteen more under treatment in other hospitals were followed 



