28 THE BACTERIOPHAGE 



strain of the bacteriophage when it comes from the organism it 

 can be enhanced in vitro. 



2. The first or first and second tubes only give a culture of the 

 dysentery bacillus. Here the filtrate contains a bacteriophage 

 of average or high activity. It is only necessary to proceed as 

 is indicated in the following case to secure areas of bacteriophagous 

 growth on agar. 



3. All three tubes remain clear. This indicates the presence 

 of a bacteriophage of extremely high activity. Confirmation is 

 simple. It consists in taking three tubes of bouillon, in adding 

 to them a suspension of young bacilli taken from an agar slant 

 in a concentration to give a slight turbidity. Introduce into each 

 of these tubes a drop of the fluid from each of the three tubes 

 which had remained clear, shake, and then immediately distribute 

 a loopful of each upon the surface of an agar slant. Both sets 

 of tubes are incubated. After twelve to eighteen hours the 

 three bouillon tubes will be limpid; the three agar slants will 

 present the appearance already described for cultures of B. 

 dysenteriae admixed with the bacteriophage. 



B. dysenteriae Shiga has been taken as an example, although 

 whatever may be the bacterial type against which an active 

 bacteriophage is sought the technic for isolation remains essen- 

 tially the same. The medium is inoculated with the bacterium 

 in question, as, for example, with B. pestis if a bacteriophage active 

 for the plague bacillus is sought. 



B. Instead of determining if a given material contains a bac- 

 teriophage active for a certain bacterium, it may be desirable 

 to ascertain if a bacteriophage which has been isolated possesses 

 an activity for several bacterial types at the same time. In 

 this instance three tubes with each of the bacterial types to be 

 investigated may be prepared. Thus, to investigate the activity 

 of an intestinal bacteriophage against B. dysenteriae Shiga, B. 

 dysenteriae Flexner, B. dysenteriae Hiss, B. typhosus, and B. 

 coli, five series of three tubes are prepared. The first set is inocu- 

 lated with B. dysenteriae Shiga, the second with B. dysenteriae 

 Flexner, the third with the Hiss strain, and the fourth and fifth 

 sets with B. typhosus and B. coli respectively. To the first tube 

 of each series one drop of the filtrate is added, to the second, ten 



