106 THE BACTERIOPHAGE 



All strains isolated, active for the Flexner bacillus, have like- 

 wise been active for B. coli, although with some, activity for 

 other varieties of dysentery bacilli was lacking. 



With reference to the bacteriophage, Flexner bacilli constitute 

 a homogeneous species. Resistant bacilli ferment glucose, levu- 

 lose, maltose, and mannite. They do not ferment lactose, do 

 not blacken lead acetate in an agar medium, and do not react on 

 neutral red. They form indol. They are inagglutinable by a 

 specific serum and possess a high viability. 



The atypical character of certain strains of B. dysenteriae when 

 freshly isolated from the organism may surely be ascribed to 

 their resistance to the bacteriophage. Elsewhere we will con- 

 sider a typical case. Furthermore, this observation is of general 

 significance, applicable not to dysentery bacilli alone. 



B. dysenteriae "X" 



During the course of these investigations a very great number 

 of specimens of feces, derived from patients with intestinal dis- 

 turbances, have been examined. And in many cases of gastro- 

 enteritis in adults as well as in infants a bacillus having the fol- 

 lowing characteristics has been isolated: 



When inoculated on litmus sugar agar media it fails to ferment 

 any of the sugars tested (lactose, glucose, levulose, saccharose, 

 maltose, mannite, galactose). It causes no change in lactose 

 and maltose Barsiekow medium, but this medium containing 

 glucose and mannite is turned red. It is agglutinated by con- 

 valescent serum in titres of 1:100 to 1:500, is not agglutinated 

 by anti-Flexner or anti-Shiga sera. With a serum which agglu- 

 tinates the Hiss strain to 1:2500 the "X" strain is agglutinated 

 in dilutions of 1:200. It is non-motile, is morphologically like 

 the other dysentery organisms, is Gram-negative, and is toxic 

 for rabbits. 



Several strains of bacteriophage active for this bacillus have 

 been isolated. This bacteriophage is constantly present in the 

 intestine in convalescents who have shown B. dysenteriae "X" 

 in their stools during the infection. Strains have also been 

 recovered from the intestinal tracts of healthy animals, both 

 man and other animals. The "X" bacillus constitutes a homo- 

 geneous species as regards the bacteriophage. 



