COLON-TYPHOID BACTERIA 95 



positive bacteria but not gram-negative organisms. Eisler and Jacobsohn 

 (230) ascribed the antagonistic action of Serratia not to the pigment but 

 to certain water-soluble, thermostable (70° C. for 30 minutes) lytic 

 substances. 



THE COLON-TYPHOID BACTERIA 



Members of the colon-typhoid group are not typical soil inhabitants, 

 although they find their way continuously into the soil and into water 

 basins. Various organisms belonging to this group have been said to 

 possess antagonistic properties (425). Bienstock (54) reported, in 1899, 

 that proteolytic bacteria are repressed by the presence of E. coU and 

 A. aerogenes. Tissier and Martelly (886) emphasized that this phe- 

 nomenon occurs only in the presence of sugar, the effect being due to 

 the fermentation of the sugar by E. colt, resulting in the production 

 of acid. 



Wathelet (954) observed in 1895 that in mixed culture the colon 

 bacterium gradually replaces the typhoid organism and this was later 

 fully confirmed (141, 383, 491, 619, 643, 799, 800, 876). The occur- 

 rence of slowly growing lactose-fermenting strains of E. coli in stools 

 has been ascribed to the phenomenon of antagonism (453), and the 

 inhibitory action upon E. tyfhosa added to certain stools was also as- 

 cribed to the antagonistic action of E. coli (643), 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 antagonis- 

 tic index 5 an index of 100:20 means that for every 100 colonies of the 

 colon organism, 20 colonies of typhoid developed. Manteufel (581), 

 however, ascribed this antagonistic action of E. coli to the exhaustion of 

 nutrients in the medium. 



Active colon strains were found to be inhibitive to other strains of 

 the same organism. The existence of strong and weak antagonistic 

 strains has been questioned frequently (1005). Nissle (642) ascribed 

 to many of these strains a strong antagonistic action against the patho- 

 genic intestinal flora. These results were contested, however (98, 512). 

 The action of E. coli of different origin varies (750), freshly isolated 

 strains being more active than stock cultures (837). It has also been 



