484 THE BACTERIOPHAGE AND ITS BEHAVIOR 



Five specimens of infected urine secured from individuals with pyelo- 

 nephritis 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 pos- 

 sessed a high resistance, although it was not entirely refractory. Thus 

 the struggle continued 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. 



Tomaselli examined 5 urines derived from patients with pyelo- 

 nephritis, and in the 5 cases he found, as had I in other cases of this type, 

 a mixed culture of bacteriophage-5. coli. On the contrary, in cases of 

 simple cystitis without renal lesions he observed that the bladder con- 

 tained only an ultrapure culture of B. coli, that is, the bacteriophage 

 was not present. As an incidental point this author suggests that this 

 fact may perhaps be of diagnostic significance in detecting the presence 

 of a renal lesion. 



My own studies permit me to confirm the statement that the bacterio- 

 phage is absent from the urines of cases with a simple cystitis, although 

 the number of cases which I have examined (eight) does not warrant a 

 final conclusion. Aside from the 5 cases of pyelonephritis mentioned 

 above, I have since seen 7 other cases of B. coli infection of the urinary 

 tract in which the cystitis was accompanied by renal lesions, and in all 

 of these a mixed culture was found. 



This introduces a new idea as to the behavior of the bacteriophage,— 

 to be added to those which we have acquired in the study of the diseases 

 previously discussed. B. coli certainly does not possess a highly de- 

 veloped pathogenic tendency. We know, for example, that in certain 

 animals (horses) this bacUlus normally passes into the blood during 

 the digestive period, and that in spite of this, it never causes any lesions, 

 a proof that it is quickly eliminated, — probably by phagocytosis. For 

 what reason, then, does this bacillus sometimes become implanted in a 

 lesion? 



The observations recorded above offer the answer to this question. 

 The infection occurs, — and persists, — because the bacillus is introduced 

 as a mixed culture, and consequently is a bacterium resistant to bacterio- 

 phagy. Against such a bacterium the body is powerless. We have 

 already shown by in vitro experiments that a bacterium resistant to the 

 bacteriophage is likewise resistant to phagocytosis. 



