STUDY AND IDENTIFICATION OF BACTERIA 



ling glass) colony can be separated into a granular center, a striated 

 periphery, and a clear external ring of liquefaction. 



On gelatin stabs the liquefaction produces a turnip-like hollow at the top of the 

 puncture the air bubble appearance. It gives the nitroso-indol reaction with sul- 

 phuric acid alone (cholera red). Kraus attaches importance to the fact that cholera 

 does not produce a haemolytic ring on blood agar as do the pseudocholera spirilla; 

 a difficulty is that many pseudospirilla do not haemolize. Furthermore, true cholera 

 strains may occasionally show haemolysis, especially in laboratory cultures. Quite 

 a discussion has arisen in connection with a spirillum isolated from cases of diarrhoea 

 (no symptoms of cholera) in pilgrims at El Tor. This organism gave the immunity 

 reactions (agglutination) of true cholera but on account of its haemolytic power has 

 been considered as distinct from cholera. Such a view would seem to be untenable. 

 Sp. choleras grows very rapidly on peptone solution and this is the medium for the 

 enrichment test to be later described. On this it may form a pellicle. On agar 

 the colony is more opalescent (more of a translucent grayish blue) than the typhoid. 

 It does not grow on potato except at incubator temperature. It 

 does not coagulate or turn acid litmus milk. The spirilla are 

 found in myriads in the rice-water discharges, these white 

 flakes being desquamated epithelial cells. They penetrate the 

 crypts of Lieberkuhn, but rarely extend to the submucosa. 

 The symptoms are due to an endotoxin. 



Cholera may be transmitted from water supplies, 

 when the outbreak is apt to be widespread and in 

 great numbers from the start. Also by indirect con- 

 tagion, as by flies or on lettuce, etc. A very im- 

 portant point is that we have well persons whose faeces 

 contain virulent cholera spirilla (cholera carriers). 



Cholera spirilla disappear from the stools of cholera 

 patients very rapidly, usually in five to ten days. 

 Cholera carriers are therefore of less importance epi- 

 riUum of cholera demiologically than typhoid carriers, 

 stab c u 1 1 u r e in j t j s we ^ to remem ber however that cases have been reported 

 oW. atl CFrTe n kll of P ositive findings after a period approximating two months 

 and Pjeifer.} from the onset of the attack of cholera. Another important 



consideration is that the vibrios may be absent at one examina- 

 tion and be present at a later one. Purgatives seem to influence the reappearance 

 of the spirilla. An acid reaction of the faeces, such as that induced by lactic acid 

 bacteria, would apparently be of value in the prophylaxis of cholera carriers. 



Greig has found infection of the bile of the gall-bladder or ducts in 80 cases in 

 271 cholera autopsies. While cholera spirilla are soon crowded out by intestinal 

 bacteria, thus explaining the short period during which cholera spirilla are excreted 

 by convalescents, this is not true when the cholera vibrio gets into the bile ducts or 

 gall-bladder, where ideal conditions prevail for a prolonged life. In fact bile has 



FIG. 38. Spi- 



