112 LABORATORY GUIDE IN BACTERIOLOGY 



SECTION 3 

 THE GROUP OF COLON-TYPHOID BACILLI 



This chapter is devoted to the study of the group 

 of intestinal organisms. This collective group may 

 conveniently be subdivided into three subgroups: 



Subgroup I : the colon group. — ^This group includes 

 different varieties of Bacillus coli and B. aerogenes. 



Subgroup 2 : the B. enteritidis group. — ^This group 

 includes B. suipestifer, B. paratyphosus, B. enteritidis, 

 and B. icteroides. The term "intermediate" is assigned 

 to this group, because it resembles in part the colon 

 group and the typhoid group. 



Subgroup 3: the typhoid-dysentery group. — This 

 group includes B. typhosus, varieties of B. dysenteriae, 

 and B. fecalis alkaligenes. 



EXERCISE I. STUDY OF SUBGROUP I 

 THE COLON GROUP 



Inoculate agar slants from laboratory cultures of 

 B. coli, B. coli anaerogenes,' and B. aerogenes. Also 

 inoculate one tube of broth with B. coli for the prepara- 

 tion of sugar-free broth. 



References — 



Smith, The Wilder Quarter Century Book, Ithaca, 1893, p. 187. 

 Smith, Amer. Jour. Med. Sci., 1895, N.S. no, p. 283. 

 Rogers, L. A., Clark, W. M., and Davis, B. J., "The Colon 

 Group of Bacteria," Jour. Inf. Dis., 14, p. 411. 



' There are many varieties of B. coli, distinguished from each 

 other chiefly by their ability to produce gas from various car- 

 bohydrates. Most varieties produce gas from dextrose and 

 lactose, some also from saccharose, and a few from dextrose only, 

 while there is one variety, known as B. coli anaerogenes, which 

 does not produce gas from any one of the three sugars. 



