CHAPTER XXV. 
THE CHOLERA GROUP. 
Cholera Vibrio. I Vibrio Metchnikovi. 
Vibrio of Finkler and Prior (Vibrio Pro- Vibrio Massaua. 
teus). I Vibrio Tyrogenum (Spirillum Deneke). 
Many vibrios have been described which possess in common with 
the cholera vibrio a number of cultural characters. They are all 
comma-shaped organisms, Gram-negative,, possess a terminal flagellum, 
form no spores or capsules, and liquefy gelatin more or less rapidly. 
They differ among themselves culturally chiefly with respect to the 
intensity M'ith which these reactions occur. Some produce nitroso 
indol in sugar-free culture media, others produce indol only. They 
may be sharply differentiated from the true cholera vibrio by serum 
reactions. So far as is known, none of these organisms will agglutinate 
with a specific cholera immune serum in high dilution, 1 to 2000 to 
1 to 5000, depending upon the titer. Xone of these organisms are 
dissolved by cholera immune serum (Pfeiffer reaction). The true 
cholera vibrio gives these serum reactions. Most of these organisms 
have been isolated from water.^ Even within the group of the true 
cholera cultures, that is, those which react with a specific cholera 
immune serum, there appear to be varieties which are distinguishable 
from the type organism with great difficulty. The principal variants 
are described below. 
CHOLERA VIBRIO. 
Synonyms.— Mbrio cholera^ asiaticte, Spirillum cholerse asiatica', 
comma bacillus, cholera vibrio. 
Historical.— The cholera vibrio was first isolated in pure culture 
by Koch in 1883.'- For some years the organism was not iniiversally 
accepted as the causative agent in Asiatic cholera, and some weight 
was attached to the frequent isolation of vibrios very similar in mor- 
phological and cultural characters to the true cholera vibrio from the 
dejecta of normal individuals. These cholera-like vibrios were not 
sharply dift'erentiated from the true cholera vibrio with the imperfect 
methods available in the early days of bacteriology, when these obser- 
vations were made. It is now universally held that the cholera vibrio 
is the causative organism of the disease. 
1 Greig (The Serological Investigation and Classification of Cholera-like Vibrios 
Isolated from Water in Calcutta, Indian Jour. Med. Research, 1916, 3, No. 4) for details. 
- Deutseh. med. Wchnschr., 1883, 9, 743; 1884, 10, 63, 111, 221, 496, 519; British 
Med. Jour., 1884, ii, 403, 453. 
