148 BACTERIOLOGY FOR NURSES 



Cholera spirilla are short, slightly curved rods 



having the general appearance of a comma and 



sometimes called " comma bacillus." The rods 



, usually occur singly, but may appear in 



O '^'^ pairs, curving in an opposite direction 



J^f'^i <* like the letter s. Longer forms fre- 



"^ ^^ quently develop in cultures, but are 



Spirilla of Asi- rarely found in the intestines. They 



atic cholera. , ■ i j -i i • • i 



are actively motile, having a single 

 flagellum at one end only. They do not form 

 spores, and stain readily with aniline dyes, losing 

 their color in Gram's method. 



The spirilla grow readily on all ordinary media. 

 An alkaline reaction is necessary for all media, the 

 spirilla being extremely sensitive to the action of 

 acids. 



At the end of twenty-four hours the colonies 

 become visible to the naked eye, showing a round, 

 even contour, which later becomes irregular, and a 

 granular surface. At the end of forty-eight hours 

 liquefaction of the gelatin occurs, resulting in 

 a characteristic funnel-shaped depression in the 

 colony. ^ 



Cholera spirilla are strictly aerobic organisms; 

 they possess no great powers of resistance, being 

 quickly killed by drying, by chemical disinfectants^ 



