CHAPTER XIII 
THE COLON-TYPHOID-DYSENTERY GROUP 
B. COLI COMMUNIS 
The reason all these bacteria are usually grouped to¬ 
gether although they produce quite different diseases, is 
that, morphologically (that is, by their appearance in 
stained preparations), they are almost indistinguishable, 
and in diagnosis our reliance is placed on cultural char¬ 
acteristics and agglutination. 
I. Historical 
The colon bacillus or, to give it its full name, bacillus 
coli communis (which means the common bacillus of colon 
—the large intestine), was first described by Buchner in 
1885, and thoroughly studied by Escherich in 1887. 
II. Morphology 
Colon bacillus is a short, plump, rod-like organism, 
Ys n long, usually occurring singly, is Gram-negative, 
has no spores, no capsules, is motile, and has flagella. 
(See Fig. 3.) 
III. Cultural Characteristics 
It is aerobic organism, grows well on simplest media, 
i. e., meat extract agar and broth; it grows at any tem¬ 
perature between 20° C. and 40°C. It does not liquefy 
gelatin, forms indol on peptone media, coagulates milk 
and forms acid in it; as to sugar fermentation, it both 
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