A Typhoid Bacteriophage. 



159 



The lytic principle thus obtained corresponds, for the most 

 part, to those described by d'Herelle. The action is non-specific. 

 It acts on Shiga and Mt. Desert dysentery cultures, as well as 

 on the homologous strain of typhoid and on other typhoid strains. 

 It has no action on the strains of Para A and B that I have tried, 

 and I have not undertaken any experiments to see whether the 

 lytic principle could become acclimatized to these organisms as 

 described by d'Herelle. It also has no action on B. Coli communis, 

 or communior. It does not seem to dissolve or inhibit Gram 

 positive organisms such as the pneumococcus. 



It is fairly thermostable. It is not destroyed by a temperature 

 of 70 0 C. for 30 minutes. It loses its activity, however, after an 

 exposure at 75 0 C. for 30 minutes. The lytic principle does not 

 maintain its activity for any length of time in sterile broth, and 

 cannot be transmitted in series in this medium. It does not 

 dissolve killed cultures, whether killed by heat or by the action 

 of ether, and is not transmissible from killed cultures. The 

 lytic principle, furthermore, does not persist and cannot be 

 transmitted in Berkfeld filtrates of young typhoid cultures, 

 which contain a certain amount of bacterial protein in solution. 

 Actively growing young typhoid cultures are essential for the 

 activity of the lytic principle. 



The dissolved or inhibited cultures usually do not become 

 absolutely sterile. If subcultures are made, it will be found that 

 the control will give a typical confluent growth, whereas the 

 tubes containing the lytic principle will give a small number of 

 discrete colonies, usually occurring at the very margin of the 

 slant. These discrete colonies are usually of two types, one the 

 round typical typhoid colony, the other an extremely irregular 

 jagged colony. If these two types are fished to broth, it will be 

 found that the fishing from the round colony will cloud the broth, 

 whereas the fishing of the irregular colony will often remain clear 

 after 12 to 18 hours in the incubator. The lytic principle can be 

 transmitted in series from the broth fishing of the irregular colony 

 in the same way as from the original stool filtrate. Two types of 

 colonies are also obtained from dissolved or inhibited Shiga and 

 Mt. Desert cultures, one the bearer of the lytic principle, the other 

 apparently a normal colony. The lytic action of these irregular 



