6i8 . Asiatic Cholera 



Detection of the Organism. — It often becomes a matter of im- 

 portance to detect the cholera spirilla in drinking-water, and, as 

 the number in which the bacteria exist in such a hquid may be 

 very small, difficulty may be experienced in finding them by ordi- 

 nary methods. One of the most expeditious methods is that 

 recommended by Loffler, who adds 200 cc. of the water to be 

 examined to 10 cc. of bouillon, allows the mixture to stand in an 

 incubator for from twelve to twenty-four hours, and then makes 

 plate cultures from the superficial layer of the hquid, where, if 

 present, the development of the spirilla will be most rapid because 

 of the free access of air. 



Castellani* recommends that a few drops of agglutinating sera for 

 such associated bacteria as may be expected to contaminate the 

 culture, be added to the medium. By this means they will grow 

 slowly and settle to the bottom of the tubes in clumps, leaving the 

 cholera organisms relatively more numerous and more easily obtained 

 from the surface. 



Gordon t employs a medium composed of lemco i gram, peptone 

 I gram, sodium bicarbonate o.i gram, starch i gram, and distilled 

 water 100 cc. for the differentiation of the cholera and Finkler- 

 Prior spirilla. If the medium be tinted with Htmus and the cultures 

 grown at 37°C., a strongly acid change is produced by the true 

 cholera organism in twenty-four hours. The Finkler-Prior spirillum 

 produces but slight acidity, which first appears about the third 

 day. 



The identification of the cholera spirillum, and its differen- 

 tiation from spiral organisms of similar morphology obtained 

 from feces or water in which no cholera organisms are expected, is 

 becoming less and less easy as our knowledge of the organisms 

 increases. The following points may be taken into consideration: 

 (i) The typical morphology. The true cholera organism is short, 

 has a single curve, is rounded at the ends, and possesses a single 

 flagellum. (2) The infectivity. Freshly isolated cultures should be 

 pathogenic for guinea-pigs, and harmless to pigeons. (3) Vegeta- 

 tive: The organism should liquefy 10 per cent, gelatin and should 

 not coagulate milk. (4) Metabolic: the indol reaction should be 

 marked. (5) Immunity reactions: the organism when injected 

 into guinea-pigs in ascending doses should occasion immunity against 

 the t)^ical cholera organism, and the serum of the immunized 

 guinea-pig, when introduced into a new guinea-pig, should protect 

 it from infection and produce Pfeiffer's phenomenon. The blood- 

 serum of animals immunized against the cholera organism should 

 agglutinate the doubtful organism in approximately the same 

 dilution, and that of animals immunized to the doubtful organism 

 should agglutinate the cholera organism reciprocally. Both organ- 



* "Brit. Med. Jour.," Oct. 13, 1917, p. 476. 

 t "Brit. Med. Jour.," July 28, 1906. 



