384 A MANUAL OF BACTERIOLOGY 



the addition of a nitrite in twenty-four to forty-eight 

 hours. 



The fermentation reactions are given in the Table, 

 p. 381 . It will be seen that the B. coli is an active fermenter 

 of many carbohydrates, alcohols, and glucosides, 1 e.g. 

 glucose, lactose, galactose, mannitol and dulcitol, but not 

 of adonit. Cane-sugar may or may not be fermented ; 

 sometimes only acid is formed, sometimes both acid and 

 gas are produced. To the variety producing both acid 

 and gas from cane-sugar Durham gave the name B. coli 

 communior. Prescott and Winslow consider that the term 

 B. coli should be applied only to an organism that does not 

 attack ketonic sugars. Neutral red in glucose broth is 

 changed to a fluorescent yellow, and Houston describes 

 a typical B. coli as " flaginac," i.e. producing fluorescence 

 in neutral red glucose pep tone- water (fl), acid and gas from 

 glucose (ag), indole in pep tone- water (in), and acid and 

 curd in milk (ac). The colonies on Conradi-Drigalski agar 

 are large and red (see " Water "). The B. coli does not 

 give the Voges-Proskauer reaction (p. 389). 



The differentiation of the B. coli from the B. typhosus 

 should present no difficulty if the morphology and motility 

 of the organisms and their fermentation and agglutination 

 reactions be compared. Bacteriologists usually make use 

 of the following tests for the differentiation of B. coli : 

 (1) Morphology, (2) motility, (3) Gram staining, (4) char- 

 acter of growth and colonies on gelatin, (5) non-lique- 

 faction of gelatin, (6) action on milk, (7) indole formation, 

 (8) fermentation of glucose, (9) fermentation of lactose 

 and saccharose, (10) action on neutral red. MacConkey 

 suggests that instead of tests Nos. 4, 6, 7, 8, and 10, the 

 following should be substituted : (a) fermentation of 

 dulcitol, but not of adonit and inulin ; (6) the Voges- 

 Proskauer reaction. 



1 Sec Twort, Proc. Roy. Soc. Lond., B, vol. Ixxviii, p. 329. 



