BACILLUS COLI 357 



sionally isolated from the centre of gall-stones; it is surmised that 

 the organism, or clusters of them, act as nuclei around which the 

 cholesterin is gradually deposited. Colon bacilli have been isolated 

 in rare instances from purulent cerebrospinal fluids, and they may 

 cause bronchopneumonia. Perirectal abscesses also may contain pure 

 cultures of colon bacilli. 



Immunity and Immunization. The constant occurrence of B. coli in 

 large numbers in the normal intestinal tract is an index of the rela- 

 tive immunity of man to infection with this organiaji. Occasionally 

 very small numbers of bacilli may gain entrance to the tissues, par- 

 ticularly in young children. The blood serum usually contains agglu- 

 tinins in small amounts for the organism. In practice no attempt is 

 made to increase the immunity to colon bacilli, except in cases of 

 cystitis or other local infection. Vaccines of the homologous strain 

 of B. coli are occasionally administered in such instances. The results 

 have been variously interpreted. 



Bacteriological Diagnosis. The methods of isolation, identification 

 and significance of B. coli in water supplies will be discussed in the 

 chapter on water. Isolation of colon bacilli from the intestinal con- 

 tents or feces is readily accomplished by plating methods. The 

 organisms far outnumber any others normally present, and even in 

 severe diarrheal disorders colon bacilli do not entirely disappear. 

 Prolonged starvation does not eliminate B. coli from the intestinal 

 canal. 1 The morphology and staining reactions are not distinctive. 

 Plating methods principle involved: lactose agar, containing lit- 

 mus or decolorized fuchsin (Endo medium) as an indicator is infected 

 with material suspected to contain B. coli. The organism ferments 

 the lactose with the production of acid; the acid changes the color 

 of the indicator immediately surrounding the colon bacilli, red if 

 litmus is used, pink if fuchsin is employed. The red colonies are 

 inoculated into broth and incubated to obtain sufficient organisms 

 for their identification by cultural methods. 



Cultural Identification. A Gram-negative bacillus which produces 

 gas in dextrose, lactose and mannite (optionally in saccharose), coagu- 

 lates but does not 'peptonize milk, does not liquefy gelatin, and is 

 without action upon starches is Bacillus coli. 



1 At the end of thirty-one days' abstinence from all food, typical colon bacilli were 

 present in the lower part of the large intestine. Kendall, Observations upon the Bacterial 

 Intestinal Flora of a Starving Man, Publication No. 203 of the Carnegie Institute of 

 Washington, 1915, p. 232. This experiment emphasizes the fallacy of "starving out" 

 intestinal bacteria by withdrawing food. 



