COLON GROUP r 203 



strains; sometimes in young cultures it is quite active; in 

 others it may be so sluggish as to be hardly distinguishable from 

 Brownian movement. B. coli communis stains readily with the 

 ordinary aniline dyes, is Gram negative, and does not form spores. 



Cultivation. The organism is an aerobic and facultative 

 anaerobe. It grows best at 37 C., but multiplication will occur 

 as low as 10 C. It develops on the simplest culture media; in 

 broth it grows rapidly causing a general clouding of the medium. 

 In gelatin stabs growth occurs along the line of inoculation and 

 spreads along the surface of the medium almost to the sides of 

 the tube. Surface colonies on agar are of a grayish color, round 

 and glistening, and often showing a peculiar structure somewhat 

 resembling a grape leaf. Colonies growing deep in the medium 

 may be oval or the shape of a whetstone. On potato growth is 

 abundant, changing from a grayish white in young cultures to a 

 yellowish brown in older ones. In milk coagulation occurs from 

 one to four days, principally due to the production of lactic and 

 acetic acid from the lactose present. In lactose-litmus-agar the 

 medium becomes red and gas bubbles frequently appear by the 

 side or under the colonies. The organism is able to ferment a 

 number of carbohydrates; it produces acid and gas in media 

 containing dextrose, levulose, galactose, lactose, maltose, and man- 

 nite. It develops especially well on media containing urine or bile. 



B. coli communis does not peptonize albumins; it does, how- 

 ever, break down some of the higher nitrogenous compounds into 

 smaller molecules. Indol is one of the most important products 

 of its activity, although little appears to be formed in the intestinal 

 canal in health. Nitrates are reduced to nitrites and from them 

 ammonia and free nitrogen are produced. 



Resistance. The organisms are able to resist a higher degree 

 of acidity or alkalinity than most non-spore-bearing forms. They 

 are killed in from five to ten minutes by a temperature of 60 C. 

 Frozen in ice, a certain percentage will live for six months. In 

 carbolic acid 1 to 100 they are destroyed in five to fifteen minutes. 



Pathogenesis. Intraperitoneal injections of 1 c.c. or more of 

 a broth culture into a guinea pig or rabbit may cause death within 



