INTESTINAL OR COLON-TYPHOID GROUP 



263 



Emmerich, in 1885, isolated an organism, which he named 

 Bacillus neapolitanus, from the feces. of patients suffering from 

 Asiatic cholera. Escherich, in 1886, isolated a similar organism, 

 which he termed Bacterium coli commune, from normal feces. 

 Since that time the organism has been found to be constantly 

 present in the intestines of man, most animals, and even some 

 birds. The question of its occurrence in nature independent of 

 fecal contamination is a moot one. That it may maintain a sapro- 

 phytic existence outside the body for some time seems to be well 

 established, but the evidence that it does not usually long so main- 

 tain itself is increasing. Examination of water for the presence of 

 B. coli to determine its potability is quite universally practised, 

 and when properly interpreted, 

 has led to valuable results. 

 The presence of B. coli in water 

 in any considerable numbers is 

 sufficient to condemn it for 

 drinking purposes, not because 

 of a pathogenic property of this 

 organism, but simply because 

 it indicates contamination with 

 surface wash or with sewage. 



Morphology and Staining. 

 The B. coli is a rod, varying 

 from 0.4 to 0.7 by 2 to 4 u, 

 sometimes shorter and almost 

 coccus-like, with rounded ends, 



usually single, but occasionally in short chains. It does not 

 produce spores or capsules. It is rather sluggishly motile, at 

 least in young cultures, usually with 2 to 8 flagella, rarely more. 

 It stains readily with the ordinary anilin dyes, sometimes show- 

 ing some vacuolization and polar granules. It is gram-negative. 



Isolation and Culture. B. coli may be readily isolated from 

 feces or sewage by plating the material in various dilutions in 

 litmus-lactose agar, and incubating at blood-heat. The colonies 

 of B. coli appear surrounded by a zone of red, due to the formation 

 of acids from the lactose. The colonies must be differentiated 

 from those of the organism next to be described. Upon gelatin 



Fig. 108. Bacillus coli, stained 

 preparation from a twenty-four-hour 

 agar slant (X 650) (Heim). 



