370 VETERINARY BACTERIOLOGY 



parts of China. It has swept in epidemics over Europe several 

 times within the last century. 



Morphology and Staining. The cholera spirillum is a short, 

 slightly curved rod, whence the common designation of " comma 

 bacillus." Longer filaments and involution forms are frequently 

 observed. It is motile by means of a single polar flagellum. 

 Spores and capsules are not produced. It stains readily with 

 the common anilin dyes and is gram-negative. 



Isolation and Culture. It may be readily isolated from the 

 stools of cholera patients by plating upon nutrient gelatin. The 

 cultural characters are very similar to those of Sp. metchnikovi. 



., 



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: *-- 



' < 

 - 



- % ^ 









- >v 



o < . 



Fig. 158. Spirillum cholera (Kiihne- Fig. 159. Spirillum cholera, showing 

 maim). flagella (Giinther). 



Physiology. It is an aerobic organism. Growth occurs readily 

 at room-temperatures, although the optimum is blood-heat. The 

 thermal death-point is 60. Desiccation, disinfectants, and sun- 

 light quickly destroy it. Blood-serum and gelatin are liquefied. 

 Milk is not coagulated. Nitrates are reduced to nitrites. Indol 

 is produced. The organism requires a neutral or slightly alkaline 

 medium for its development. 



Pathogenesis. Experimental Evidence. Asiatic cholera, in the 

 form found in man, usually cannot be transmitted to laboratory 

 animals. The etiologic relation of Sp. choleras to the disease, how- 

 ever, has been established by accidental and intentional infection 

 of several laboratory workers. Intraperitoneal injection of the 



