COLON-TYPHOID BACTERIA 101 



to the fermentation of the sugar by E. coli, resulting in the production 

 of acid. 



Wathelet (983) observed in 1895 that in mixed culture the colon 

 bacterium gradually replaces the typhoid organism and this was later 

 fully confirmed. The occurrence of slowly growing lactose-fermenting 

 strains of E. colt in stools has been ascribed to the phenomenon of an- 

 tagonism (462), and the inhibitory action upon E. tyfhosa added to 

 certain stools was also ascribed to the antagonistic action of E. coli 

 (681). Different strains of E. coli repress the typhoid organism to a 

 different extent. The ratio of the two organisms developing on agar was , 

 designated as the antagonistic index j an index of 100:20 means that 

 for every lOO colonies of the colon organism, 20 colonies of typhoid 

 developed. 



Active colon strains may be inhibitive to other strains of the same 

 organism. The existence of strong and weak antagonistic strains has 

 been questioned frequently (1034). Many of these strains were ob- 

 served to have a strong antagonistic action against the pathogenic in- 

 testinal flora j these results were contested, however (97, 543). The ac- 

 tion of E. coli of different origin varies, freshly isolated strains being 

 more active than stock cultures (783, 866). It has also been reported 

 that fresh, actively growing cultures of E. typhosa inhibit the growth 

 of E. coli, but that older cultures are not antagonistic (936). 



The production by smooth strains of E. coli of a highly specific bac- 

 teriolytic substance which lyses the cells of a rough strain of this organ- 

 ism has also been indicated (1045) j this substance was ineffective 

 against other rough and smooth strains, whereas the filtrates of the 

 rough strains were inactive upon the smooth strain. The substance is 

 readily destroyed by heating at 70° to 80° C. E. coli antagonism has 

 also been correlated (632) with the greater resistance of the strains to 

 environmental factors, their greater rate of multiplication, and their 

 greater adaptation to nutrient media. 



A bacteriophage was found (574) to develop as a result of the an- 

 tagonistic action of E. coli against the Shiga bacillus and was said to 

 ocpur in the intestines where antagonistic conditions are always present. 

 Gratia (355) found that the filtrates of one race of E. coli inhibited 



