272 



VETERINARY BACTERIOLOGY 



shown by the fact that the filtrate was quite incapable of infecting 

 culture-media. By the subsequent work of Dorset, Bolton, and 

 McBryde it was shown quite conclusively that the B. cholerce suis 

 is not the cause of hog-cholera in the Mississippi Valley, and but a 

 secondary invader at most. Hog-cholera and its virus will be 

 considered, therefore, under the heading of Diseases Caused by 

 Ultramicroscopic Organisms. The Bacillus cholerce suis, however, 

 doubtless plays some part in the disease as a secondary invader, 

 and is, therefore, worthy of consideration. 



Morphology and Staining. This organism differs morpho- 

 logically in no essential character from B. enteritidis. 



Isolation and Culture. 

 B. choleroe suis may 

 frequently be isolated at 

 once in pure culture from 

 the organs of infected 

 animals, particularly 

 from the spleen. It has 

 likewise been isolated 

 by plating the intestinal 

 contents of normal and 

 infected animals. The 

 organism grows upon 

 agar and gelatin, form- 

 ing a grayish, glistening, 

 non-viscid growth, which 

 is not particularly char- 

 acteristic. No growth 

 occurs upon potatoes 



having a decided acid reaction, but upon those which are neutral 

 or alkaline a thin, glistening, usually yellowish, layer is formed. 

 Bouillon is uniformly clouded; a slight pellicle may appear in 

 time. A grayish, friable sediment is formed. Milk shows a 

 slight initial acidity, but soon becomes alkaline, and gradually 

 becomes opalescent and finally translucent. It will be noted that 

 there are no marked cultural differences between B. enteritidis 

 and B. choleras suis. 



Physiology. B. choleroe suis is aerobic and facultative anaerobic. 



Fig. 112. Bacillus cholerce suis, organisms 

 from a young culture (deSchweinitz, Bureau 

 Animal Industry). 



