CHAPTER IX. 



STUDY AND IDENTIFICATION OF BACTERIA. SPIRILLA. 

 KEY AND NOTES. 



Key to recognition of gelatin-liquefying, motile and Gram negative 

 spiral or comma-shaped organisms. 



A. Do not give the nitroso-indol reaction with sulphuric acid alone in 24 



hours. 



1. Produce an abundant moist cream-colored growth on potato at room 

 temperature. 



a. Finkler and Prior's spirillum. Liquefaction of gelatin very rapid. 

 No air-bubble appearance at top of liquefied area. Cultures have 

 foul odor. Milk coagulated. Thicker spirillum than cholera. 

 Isolated from cholera nostras. 



2. Scanty growth or none at all on potato at room temperature. Only 



a moderate yellowish growth when incubated about incubator 

 temperature. 



a. Spirillum tyrogenum. Does not liquefy gelatin so rapidly as 

 Finkler Prior. Thinner and smaller spirillum than cholera. 



B. Give the nitroso-indol reaction with sulphuric acid within 24 hours. 



1. Very pathogenic for pigeons. 



a. Spirillum metschnikovi. Liquefies gelatin about twice as rapidly 

 as cholera. Gives bubble appearance at top of stab. 



2. Scarcely pathogenic for pigeons. 



a. Spirillum cholerse asiaticas. Milk not coagulated. 



Nonmotile, nonliquefying gelatin and Gram positive spirilla have also been 

 described. There is also a large group of phosphorescent spirilla. 



Spirillum Choleras Asiaticae (Koch, 1884). Typically, the 

 morphology of this organism is that of the comma (Comma bacillus 

 of Koch). It also frequently shows S shapes, and often appears in 

 long threads showing turns. When freshly isolated from cholera 

 material they, as a rule, show a fairly typical morphology, but after 

 subcultures in the laboratory variations are common, so that red forms 

 and round involution shapes give a picture altogether at variance 

 with the comma shape. Even in recent cultures of undoubted cholera 

 we may have different types, as coccoid forms and slender rods. 



The cholera spirillum is very motile and liquefies gelatin fairly 



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