THE BACILLUS COLI 457 



The sub-cultures on agar are incubated overnight and some of 

 the cultures may then be excluded by the macroscopic appearance 

 of the growth. Those finally selected are sub-cultured into 

 Durham's tubes of the following sugars, etc. ; 1 per cent, glucose, 

 lactose, maltose, saccharose, mannitol and dulcitol in litmus 

 peptone water. These are then incubated overnight and some- 

 may again be rejected owing to fermentation of lactose. The 

 likely strains are then agglutinated with specific sera according to 

 the indications given by the sugar reactions. Any sugar tubes 

 which show no change should be incubated for a further period. 



Bacillus | Bacterium] coli 



The Bacillus coli (B. coli communis), or colon bacillus, 

 is, as its names implies, a constant inhabitant of the 

 intestinal tract in man and animals (except perhaps in 

 certain arctic animals), and is one of the most widely 

 distributed organisms in nature. It is an organism of 

 considerable importance in pathological processes, and 

 its presence serves as an indication of pollution in water, 

 shell-fish, milk and other foodstuffs. 



Although the term " colon bacillus " is applied to a 

 fairly well-defined organism (the " typical B. coli "), a 

 number of allied organisms occur differing from the type 

 in one or more characters e.g. motility, indole production, 

 fermentation reactions, rate and extent of milk curdling, 

 etc. and these varieties are said to belong to the " colon 

 group," or are termed " coliform." 



The B. coli may be readily isolated by inoculating litmus 

 lactose bile-salt peptone-water tubes with a trace of a 

 suspension of fresh faeces, growing for from twenty-four 

 to forty-eight hours at 37-42 C., and plating the culture 

 on litmus lactose agar, on gelatin, or on Conradi-Drigalski 

 agar, or by direct plating of the faeces suspension on the 

 last-named medium (see also " Water "). 



Morphology. The B. coli is a short rod averaging 

 2 or 3 jit long and 0-5 p broad, frequently linked in pairs 



