BACILLUS COLI 49 



General Note. — ^Whilst the above desoriptiou applies to the 

 normal type of B. coli, it should be clearly understood that a large 

 number of bacilli have been described which possess some, but not 

 all, of the above characters. Eefik has described (Ann. de I'Inst. 

 Pasteur, x., 1896, 242), five varying types very similar to the normal 

 B. coli, but differing in one or more characters. Almost all forms, 

 however, have some features in common, e.g., motility, few flagella, 

 and characteristic growth on potato. Moreover, there are a group 

 of organisiQS allied to B. coli, and often associated with it. Like it 

 also, they are related, etiologically or otherwise, to similar pathological 

 processes. Eefik's types are briefly as follows : — 



A. Ferments lactose, coagulates milk, but gives no indol reaction. 



B. Ferments lactose, does not coagulate milk, gives indol reaction. 



C. Ferments lactose, does not coagulate milk, does not give indol 

 reaction. 



D. Does not ferment lactose, coagulates milk, does not give indol 

 reaction. 



E. Does not ferment lactose, does not coagulate milk, does not 

 give indol reaction. 



Mervyn Gordon has made a careful study of the B. coli and its 

 allies which he classified according to their reactions and their flagella. 

 He differentiated 16 varieties.* Horrocks studied the cultural char- 

 acters of 150 " varieties " of B. coli isolated partly from normal and 

 partly from typhoid stools.-f Other workers have observed an 

 enormous variety of minor differences. The important point is the 

 diagnosis of B. coli, and the following characters are now chiefly relied 

 upon (see also p. 472). 1. The B. coli group is non-sporing and non- 

 liquefying; 2. The members of the group rarely stain by Gram's 

 method ; 3. They produce acid and gas with both glucose and lactose ; 

 4. They produce acid in milk and they usually also coagulate it ; 5. 

 They produce acid and gas in bile-salt-glucose broth ; 6. They grow 

 well at a temperature of 42° C.J Other fairly reliable features are 

 motility, a small number of flagella, a fairly typical growth on potato, 

 and more rapid development on all media than the typhoid bacillus. 

 But there is not at the present time a complete unanimity of opinion 

 as to the most reliable characters for diagnostic purposes. § 



* Jour, of Path, and Bad., 1897, vol. iv., p. 438. 



t Bacteriological Exammation of Water, 1901, p. 94; Jour, of Hyg., 1901, p. 202. 



J Roy. Com. on Sewage Disposal, Second Report, 1902, p. 101. See also Brit. 

 Med. Jour., 1903, 1. 418 (Klein), for summary of characters of jB. coli. 



§ Houston considers the following the most useful tests for B. coli: (l)Gas 

 forma'tion in ordinary gelatine " shake " cultures ; (2) indol in broth cultures ; 

 (3) acid and clot in litmus milk - cultures ; (4) greenish-yellow fluorescence in 

 neutral-red broth cultures ; (5) gas and acid in lactose-peptone cultures ; (6) gas, 

 acid, and clot in peptone-lactose milk cultures ; (7) gas and acid in glucose-peptone 

 cultures ; (8) reduction of nitrate to nitrite in nitrate broth cultures ; (9) strong 

 acid in Proskauer and Capaldi's medium No. 1, and no definite production of acid 



D 



