362 



TYPHOID FEVER 



THE BACILLUS COLI COMMUNIS. 



Although the discovery of the bacillus coli communis was 

 subsequent to that of the bacillus typhosus, it is convenient to 

 commence with a description of the former, as it presents more 

 positive characters than any other member of the group to which 

 it belongs. 



Bacillus Coli Communis. Morphological Characters. These 

 are best seen in cultures. The bacillus is ordinarily from 2 to 

 4 //, long and about *5 /x broad; longer forms up to 8 or 10 /JL 

 are not infrequent (Fig. 109). It is usually found to be motilej 



but the motility varies 

 in different strains and 

 under different growth 

 conditions in the same 

 strain. Here it is best 

 to use bouillon cultures 

 incubated at 37 C. for 

 from six to twelve hours. 

 The organism may stain 

 somewhat faintly with 

 watery dyes, but is 

 readily demonstrated 

 with carbol-fuchsin even 

 in fairly weak solution 

 (1 of the Ziehl-Neelsen 

 stain in 20 of water) ; 

 it is Gram-negative. By 

 appropriate staining b. 

 coli derived from cul- 

 tures can be shown to 



possess fiagella springing from all round the organism, varying 

 in number and occasionally rather short. 



Culture Reactions on Ordinary Media. The following are 

 the appearances of the b. coli in the ordinary culture media : 



In bouillon, it produces a uniform turbidity. When grown in 

 fluid gelatin, it is stated by Klein to tend to form nocculi floating 

 on the surface rather than a uniform turbidity. In stab cultures 

 on peptone gelatin an abundant film-like growth takes place on 

 the surface, and there is a whitish or brownish-white line along 

 the stab. No liquefaction of the gelatin occurs, but occasionally 

 a few bubbles of gas develop (Fig. 113, C). In sloped agar 

 tubes a somewhat dense, glistening, white or brownish- white 

 growth occurs along the stroke. When agar plates are used 



FIG. 109. Bacillus coli communis. Film 

 preparation from a young culture on agar. 

 Stained with weak carbol-fuchsiii. x 1000. 



