ELEMENTARY BACTERIOLOGY LABORATORY EXERCISES 57 
EXERCISE 86 
THE COLON-TYPHOID BACTERIA 
In the general class of the intestinal or colon-typhoid bacteria are included 
three divisions. 
(1) The coli-aerogenes group, includes Bacterium coli, Bacterium aero- 
genes and a number of other species which have been previously studied in con- 
nection with water and milk. These organisms are non-pathogenic, although 
Bacterium coli is occasionally associated with certain troubles, especially inflam- 
mation of the urinary and gall bladder. 
(2) The enteritidis-paratyphoid group includes a number of closely re- 
lated species. Bacterium enteritidis and Bacterium paratyphi (types A and B) 
are found especially as the causes of meat poisoning and are also spread to some 
extent by polluted milk and water. In this group belong a number of other very 
closely related species which are responsible for diseases in lower animals. The 
more important of these are: Bacterium suipestifer, a secondary invader in hog 
cholera; Bacterium pollorum, the cause of white diarrhea in chicks, and Bac- 
terium typhi-murium, the cause of mouse typhoid. 
(3) The typhoid-dysentery group includes the organism of typhoid fever, 
Bacterium typhosum, and the casual organism of bacterial dysentery in man, 
Bacterium dysenteriae. 
Study cultures of Bacterium coli, Bacterium aerogenes, Bacterium enteritidis, 
Bacterium paratyphi, Bacterium typhosum, and Bacterium dysenteriae as fol- 
lows: (1) Morphological study including motility and reaction to the Gram 
stain; (2) action on gelatin; (3) action on litmus milk; (4) fermentative char- 
acteristics in glucose and lactose broths in Durham tubes. 
From this study, what morphological and cultural characteristics appear to 
be common to all of the colon-typhoid organisms? According to the results ob- 
tained in glucose and lactose broths and litmus milk, what differences are found 
between the three divisions of the colon-typhoid organisms? 
EXERCISE 87 
TUBERCULOSIS 
Study the type of growth produced by Mycobacterium tuberculosis on the agar 
slope culture furnished. The agar used for this purpose is beef infusion agar with 
the addition of five per cent glycerol. Make a stained preparation using the acid- 
fast staining method outlined in Exercise 19, and study its morphology. 
Examine the samples of sputa supplied for the presence of the organism of 
tuberculosis, employing the method previously used (Exercise 19). 
Make a post-mortem examination of a tubercular guinea pig. Note the lo- 
cations and characteristics of the lesions. Make slide preparations from typical 
