CHOLERA VIBRIO 509 



these conditions is fairly conclusive. It should be remembered that 

 an occasional strain of the cholera vibrio is met with which does not 

 agglutinate when freshly isolated; prolonged cultivation in artificial 

 media frequently leads to a typical agglutination. 



4. Identification of Cholera Vibrios by the Pfeiffer Phenomenon. 

 If cholera vibrios are introduced directly into the peritoneal cavity 

 of an immunized guinea-pig and samples of the peritoneal exudate 

 containing vibrios are removed from the peritoneal cavity with a 

 capillary pipette after ten minutes, sixty minutes and ninety minutes, 

 it will be found that usually after ten minutes, almost invariably 

 within an hour, the vibrios will become very much granulated and will 

 eventually dissolve. A normal guinea-pig similarly infected intra- 

 peritoneally with a mixture of cholera vibrios and immune serum 

 will exhibit the same granulation and lysis of the organisms. The 

 reaction does not occur when the vibrios alone are introduced into 

 the peritoneal cavity of a normal pig. It is much simpler to introduce 

 the immune serum and vibrios into test-tubes, incubate them at 36 

 C. and examine the contents of the tubes for granulated and partly 

 dissolved organisms after intervals up to two hours. The test is 

 carried out as follows: a series of dilutions of fresh immune serum, 

 1 to 50 to 1 to 500, is prepared in small sterile test-tubes, 0.5 c.c. to 

 each tube. A suspension of cholera vibrios, one loopful of an eighteen- 

 hour agar slant growth to 1 c.c. of sterile salt solution, is also prepared; 

 usually 10 c.c. are sufficient. This is thoroughly shaken and 0.5 c.c. 

 added to each tube of diluted serum. Control tubes of normal serum 

 and bacterial suspension are incubated uuder parallel conditions. 

 The entire set of tubes is incubated at 37 C. and examined at intervals 

 up to four hours. The control tubes swarm with vibrios. The immune 

 serum tubes up to the limits of potency contain vibrios in various 

 stages of solution. Only true cholera vibrios will be thus dissolved. 

 The various cholera-like vibrios are unaffected. 



The bacteriological diagnosis of the cholera vibrio is one of the 

 most difficult known to bacteriology. The large number of closely 

 related forms introduces complications in the diagnosis which have 

 frequently led to error. In general it may be stated that a vibrio 

 which agglutinates 2"oW with a specific anticholera serum of high 

 potency, and exhibits the Pfeiffer phenomenon in a perfectly typical 

 manner may be safely diagnosed as positive. Departure from this 

 standard should cause the organism to be regarded with suspicion, 

 but should not lead to relaxation of appropriate hygienic measures in 

 relation to the case. 



