DYSENTERY BACILLUS 157 



The differentiation of the typhoid from the colon bacillus is largely 

 accomplished by noting the chemical reactions of both organisms 

 in culture media. The chief differences are: 



1. The typhoid bacillus has more flagella than the colon, and is 

 much more motile. 



2. On gelatine culture plates, the typhoid colonies develop more 

 slowly than the colon, and are much more delicate and transparent. 

 If litmus is present the colon colonies are red, the typhoid bluish. 



3. In media containing dextrose, or lactose, gas is produced by 

 the colon, but not by typhoid. 



4. In peptone solution the colon produces indol, while the typhoid 

 does ngt. 



5. Milk is coagulated by the colon, but not by the typhoid. 



6. On potatoes colon grows much more luxuriantly than typhoid. 



7. Typhoid reddens neutral red; colon changes it to bright yellow. 



8. The most important test is the agglutinative one. Typhoid is 

 clumped by anti-typhoid sera, highly diluted, while the colon is not. 



No anti-sera of value have been found for colon bacillus infection, 

 but bacterins have been used with much benefit. 



DYSENTERY BACILLUS. 



Bacterium Dysenteriae. 



Dysentery Bacillus of Shiga and Flexner. 



Supposed cause of one form of tropical dysentery. The group 

 to which this belongs comprises many closely related varieties some 

 of which are thought to be the cause of infant diarrhoea in this 

 country. There are various strains of this organism, the differentia- 

 tion of which depend upon their chemical activities, fermentation 

 of various carbohydrates being the most important, and agglutina- 

 tive properties with different sera. 



Morphology and Stains. The organism is, in many respects, 

 similar to the typhoid bacillus, but is plumper. It is said to be 

 flagellated, has no. spores, and exhibits pleomorphism. It stains 

 well with the common aniline dyes, but not by Gram's method. 



