50 BACTERIA IN WATER 



The significance of B. coli is of course its potential pathogenicity, 

 and its similarity to the typhoid bacillus, but above all its relation 

 to sewage. Roux, Rodet, and others have stated that B. coli, under 

 certain circumstances, may assume a character not distinguishable 

 from B. typhosus, both in its biological and cultural characteristics 

 and in its pathogenic properties. Chantemesse, Widal, and others 

 have held that polluted waters owe their power to produce typhoid 

 fever to the presence of B. coli, and that possibly the organisms 

 are transformable the one into the other. Klein and many other 

 bacteriologists, as the result of very numerous experiments, have 

 been unable to effect any transformation of one form into the 

 other. Each organism has retained unimpaired its differential 

 characters. 



Certain strains of B. coli are distinctly pathogenic for lower 

 animals, and there is some ground for considering the organism a 

 cause of disease (epidemic diarrhoea and other conditions) in man, 

 either by itself or in association with other organisms (Delepine). 

 In the third place, as is pointed out elsewhere, B. coli is a sewage 

 organism, and the chief importance of its detection in water is an 

 indication of sewage pollution and therefore of possible contamination 

 of the water with specific bacteria. It is therefore a most reliable 

 test of pollution. Klein and Houston have emphasised the importance 

 of the presence of B. coli and the B. cnteritides sporogencs in water as 

 indication of sewage pollution, and by this means a demonstration of 

 the presence of sewage in ~ water can be carried to an incomparably 

 higher degree than by chemical examination. Chemistry is powerless 

 to detect pollution ' by pathogenic germs or the small amount of 

 organic pollution which can be detected by bacteriology, which is ten 



in Proskauer and Capaldi's medium No. 2 ; (10) presence of motility ; (11) 

 non-liquefaction of gelatine ; and (12) acidity in litmus whey cultures, varying from 



about 20-40 c.c. Na 2 CO 3 per 100 c.c. of culture. In dealing with sewage, 



effluents, and non-drinking-water streams, Houston employs the first three tests, 

 but in dealing with drinking-water, the first five tests (Fourth Report of Royal 

 Commission Sewage Disposal, 1904, p. 106). 



McWeeney relies chiefly upon '(a) the character of gelatin colony and non- 

 liquefaction of that medium, even after a long time ; (6) non-retention of Gram's 

 stain ; (c) fermentation of lactose with gas and acid formation ; (d) coagulation of 

 milk within four days at 37 C. ; (e) production of yellowish-green fluorescence in 

 neutral-red-agar-shake culture ; and (/) production of indol in liquid peptone media. 

 (Report of Local Government Board for Ireland, 1904). Klein describes B. coli 

 as a motile, non-spore-bearing bacillus, possessing a limited number of flagella, 

 capable of fermenting glucose and lactose, of curdling milk with the production of 

 acid, of forming indol in broth culture, reducing neutral red with the production of 

 a green fluorescence^producing gas-bubbles in nutrient jelly, of forming a more or 

 less brownish growth ran steamed potato, and of producing on the surface of gelatin 

 a dry, translucent growth which does not liquefy the gelatin. The bacilli, under the 

 microscope, appear asfcylindrical rods, showing more or less pronounced motility, 

 and they do not stainjby the method of Gram (see also Appendix, pp. 466 and 472). 



