254 



BACTERIOLOGY FOR NURSES 



FIG. 36. Cholera Spirilla, enlarged to 

 show Flagella. 



it possesses only a single long fine flagellum attached to one 

 end (Fig. 36). Small highly refractile bodies are sometimes noted, 

 but true spores are not formed. Staining is best accomplished 

 with Loeffler's methylene blue or a weak solution of carbol 



fuchsin. The organisms are 

 Gram negative. 



Cultivation. The cholera 

 spirillum is an aerobe and 

 grows on all ordinary media 

 provided the reaction is dis- 

 tinctly alkaline to litmus. De- 

 velopment is most luxuriant at 

 37 C. although multiplication 

 will occur at a temperature as 

 low as 16 C. In gelatin stab 

 cultures growth appears along 

 the needle tract, and in about 

 twenty-four hours liquefaction 

 commences on the surface as a small bell-shaped area which 

 deepens until by the end of the week the entire medium may be 

 fluid. On gelatin plates the colonies appear as minute whitish 

 points with a granular surface somewhat resembling a layer of 

 powdered glass. After twenty-four to forty-eight hours liquefac- 

 tion of the gelatin commences around each colony and as it pro- 

 gresses the colony sinks to the bottom of the cup-like depression 

 thus formed. On agar the colonies have a characteristic opalescent 

 appearance ; on potato growth takes place only at 37 C. and then 

 it appears as a dirty moist layer. Acid is rapidly produced from 

 glucose, saccharose, and maltose ; coagulated blood serum is lique- 

 fied. In milk growth takes place without producing any visible 

 change. 



Indol is produced in peptone water medium by all true cholera 

 spirilla ; certain other organisms have the same ability, but they 

 are comparatively few. The cholera spirillum produces nitrites 

 at the same time as indol, so that in applying the test it is only 

 necessary to add a few drops of sulphuric acid to a peptone water 



