BACILLUS-COLI-LlKE BACTERIA FROM FECES AND SEWAGE 33 



subdivision of the colon-bacillus group, but Rogers 7 questions the 

 value of salicin in view of the very large number of his strains which 

 attacked it. In this connection it might be well to point out that 

 organisms studied by Rogers consisted of bovine strains, grain strains 

 (probably Voges-Proskauer-positive organisms), and milk strains 

 (which may be considered for the most part as a mixture of bovine 

 and grain strains). In view of the results obtained here with bovine 

 and Voges-Proskauer-positive strains, and by Kligler with Voges- 

 Proskauer-positive strains, it would be expected that more than 90% 

 of Rogers' cultures would attack salicin. It appears then that salicin- 

 fermentation is somewhat correlated with the source. 



Glycerol is also fermented by almost all the Voges-Proskauer- 

 positive and bovine strains and less frequently by organisms from the 

 other animals, but the difference is less marked than with salicin. 



Dulcitol is only occasionally fermented by the human and Voges- 

 Proskauer-positive strains, but there seems to be very little relation 

 between dulcitol-fermentation and the animal source. 



Indol-production is not correlated with the animal source. 



In motility there is a marked contrast between the strains from 

 horse, sheep, cow, and pig on the one hand, and those from man and 

 sewage on the other. Less than one-third of the sewage and human 

 strains are motile, as. compared with more than four-fifths of the 

 other animal strains. McWeeney 9 found nonmotile B. coli abundant 

 in feces, and notes that Stocklin also had observed many nonmotile 

 forms among fecal strains. Just what significance is to be attached 

 to motility is hard to say at present, because so few bacteriologists 

 determine this character in routine work. MacConkey, however, 

 strongly advocates the test. As determined in the 0.5% agar medium 

 the motility test is simple, quick, and not at all burdensome. 



Sucrose and raffinose are so well correlated that a consideration 

 of either will suffice for both. The Voges-Proskauer-positive and 

 sheep strains are practically all sucrose- fermenters (100% and 95.5% 

 respectively). Of the horse strains 79%, and of the organisms from 

 the cow 50% form gas from sucrose; only 32.3% of strains from the 

 pig, 26.6% of those from sewage (Voges-Proskauer-negative strains), 

 and 12% of those from man form gas from sucrose. That such a 

 small number of human strains attack sucrose is particularly interest- 

 ing, and a review of the literature indicates that similar results have 



9 Cited by Prescott and Winslow, Elements oi: Water Bacteriology, 1913. 



