152 ESSENTIALS OF BACTERIOLOGY 



Products "Cholera red." Indol Reaction. Present in 

 peptone water cultures containing nitrates. The indol is 

 shown by the addition of a few drops of pure sulphuric acid, 

 the solution turning red the so-called " cholera red." Once 

 thought distinctive, but other bacteria also give rise to indol, 

 and the same reaction. 



Serum Agglutination Test. The agglutination test is made 

 in the same way as the Widal test for typhoid fever. Ag- 

 glutinins appear in the blood five to ten days after infection. 



** 



1 



V 



Fig. 67. Comma bacillus in mucus, from a case of Asiatic cholera. 



Cultures in serum dilutions of 1:1000 up to i: 10,000 are 

 agglutinated. 



Detection of Cholera Organisms in Drinking-water. When 

 a few bacteria are supposed to be present in fecal matter or 

 drinking-water, it is best to add a large quantity of the ma- 

 terial (200 c.c. of drinking-water) to about 10 c.c. of bouillon 

 or peptone-water, and place the mixture for twenty-four hours 

 in an incubator, which will cause rapid reproduction, and then 

 the organisms can be readily discovered. 



