SURVIVAL OF PATHOGENS IN SOIL AND WATER 31 



killed, and in the course of a few more days all the cells tended to dis- 

 appear entirely from the soil. Under conditions less favorable to the 

 growth of antagonists, the typhoid organism survived not only for 

 many days, but even for months. The conclusion was reached that when 

 soil bacteria are given a chance to develop by-products, there results a 

 marked destruction of typhoid organisms brought into contact with 

 them. 



Among the factors responsible for the disappearance of E. tyfhosa 

 in water, the presence of certain water bacteria was found to be of spe- 

 cial importance (924). Rochaix and Vieux (798) demonstrated that 

 when an achromogenic strain of Pseudomonas aeruginosa was present in 

 drinking water, it was not accompanied by any other bacteria. Media 

 inoculated with this organism and E. coli gave, after 1 3 days' incubation, 

 only cultures of the former. That the two organisms could coexist, how- 

 ever, was shown by inoculation into sterilized water. Only the actual 

 development of the antagonist led to the repression of the fecal organ- 

 ism. The supply of oxygen in the water is important. E. typhosa 

 added to activated sludge increased within the first 4 to 6 hours j this was 

 followed by a reduction in 24 hours, and a 99 per cent destruction in sev- 

 eral days (422). The survival period was shorter in sewage-polluted 

 than in unpolluted waters, especially when the sewage was aerated. 

 About 80 per cent reduction of typhoid bacteria was obtained in the 

 Netherlands East Indies by the passage of sewage through Imhoff 

 tanks. Digestion of sludge reduced the number further but did not 

 eliminate the bacteria completely 5 after the sludge was dried no typhoid 

 bacteria could be found {6S'i)' 



A study of microorganisms antagonistic to E. coli resulted in the iso- 

 lation of organisms from 5 of 44 samples of well water, i of 1 2 sam- 

 ples of spring water, and 6 of 1 6 samples of surface water. The antag- 

 onists included 3 strains of Pseudomonas, i each of Sarcina, Micro- 

 coccus, Flavobacterium, and yeast, 2 actinomycetes, and 3 unidentified 

 nonspore-forming, gram-negative rods (455). 



The survival of E. tyfhosa in manure and in soil is known to be af- 

 fected decidedly by various saprophytic bacteria. When a carrier was 

 induced to urinate on a soil, E. fyphosa could be recovered within 



