CHAPTER XXVII 



SPIRILLUM CHOLERA ASIATICS, VIBRIO CHOLERA 

 ASIATICS (COMMA BACILLUS) 



The cholera spirillum occurs in water polluted with dejecta from cholera 

 patients and from this source probably gets to some articles of food. Epidemics 

 of cholera occur from time to time in all densely populated regions where 

 pollution of drinking water occurs, especially in the temperate zones. 



Morphology. The cholera spirillum usually appears as a curved rod, from 

 1.5 to 3 n long, 0.5 /j. wide; it is to this common appearance that the descriptive 

 name comma bacillus is due. Long spirals are also observed, having two, three 

 or more curls like a corkscrew. The cholera spirillum has a single terminal 

 flagellum and is actively motile. 



Staining. The cholera spirillum stains with all the usual stains and is 

 Gram negative. 



Growth. The cholera spirillum is aerobic and to a slight degree facultative 

 anaerobic. It grows at temperatures between i5C. and 4OC., best at 37C. 



Bouillon incubated at 37C. shows cloudiness in 6 to 8 hours; later, a deli- 

 cate whitish pellicle forms. In 48 to 72 hours a flocculent precipitate occurs. 



Agar. Round, grayish colonies, with granular centers and smooth edges, 

 appear in 24 hours. Growth on agar is luxuriant and may cover the entire 

 surface with a whitish film in 18 to 36 hours. 



Gelatin. -In gelatin stabs growth first appears at the surface of the stab, 

 causing a zone of liquefaction; growth progresses along the stab, more slowly 

 the further from the surface, causing a funnel-shaped tract of liquefaction. 

 Eventually all the gelatin is liquefied. 



On gelatin plates yellowish, granular, irregular colonies, surrounded with a 

 more highly refractile, whitish zone appear in 24 hours. 



The medium is liquefied. 



Potato shows an abundant, clear, brownish growth if the medium is alkaline. 

 On neutral or acid potato, growth is scant or absent. 



Milk is coagulated by some and not coagulated by other strains of the 

 cholera spirillum. 



Indol is nearly always produced. 



There is no spore formation. 



Fermentation of all the sugars in common use occurs. 



Dunham's solution is especially favorable for the cultivation and isolation 

 of the cholera spirillum. Incubated at 37C., growth accumulates at the 

 surface in 6 to 12 hours. 



Resistance. The cholera spirillum is less resistant to germicidal agents 

 than the typhoid bacillus. Freezing does not injure it. Drying rapidly de- 



