1022 BACTERIA IN AIR, SOIL, WATER, AND MILK 



distinctly pathogenic, such as the cholera spirillum and the typhoid 

 bacillus, or of other species probably emanating from contaminating 

 sources, such as a B. coli. Unfortunately there are no reliable 

 methods by which typhoid and cholera germs can be isolated from 

 water with any degree of regularity or certainty. Although fre- 

 quently the isolation of such organisms is possible, a negative result 

 in these cases is by no means eliminative of their presence. 



The isolation of typhoid bacilli from water is very difficult, chiefly 

 because of the great dilution which contaminations undergo upon 

 entering any large body of water. The difficulty of isolating typhoid 

 bacilli, even from the stools of infected patients, makes it clear that 

 such difficulties are enhanced when a considerable dilution of the 

 excreta takes place. Furthermore, water is by no means a favorable 

 medium for the typhoid bacillus. Russell and Fuller 10 have shown 

 that typhoid bacilli may die in water within five days, and it is 

 unquestionable that the rate of increase of these bacteria is by no 

 means equal to that of many other microorganisms for which pol- 

 luted water at the temperature encountered in streams and lakes 

 forms a much more favorable medium. 



It is thus clear that even in infected waters the number of typhoid 

 bacilli encountered can never be very great. 11 



A large number of methods for the isolation of the typhoid 

 bacillus from water have been devised. Most of the media used 

 are identical with those employed for the isolation of these bacteria 

 from the stools. These media have been discussed in the chapter 

 dealing with the typhoid bacillus. Success is rendered more likely 

 if 10 c.c. of the water is first planted into lactose-bile in fermentation 

 tubes holding 40 c.c. After forty-eight hours at 37.5 there will 

 be an enrichment of typhoid bacilli which can be then isolated by 

 plating in the usual manner on Endo 's medium, Conradi Drigulski or 

 any of the other usual differential media. 



A method which has proved useful in the hands of Adami and 

 Chapin 12 is one which depends upon the phenomenon of agglutina- 

 tion. They attempt to agglutinate the bacilli out of liter samples 

 of water by adding powerful agglutinating serum. 



Vallet and others have attempted to precipitate typhoid bacilli 

 out of water by chemical means. To two liters of water add 20 c.c. 



Eussell and Futter, Jour. Inf. Dis., Suppl. 2, 1908. 



11 Laws and Anderson, Rep. of Med. Officer, London County Council, 1894. 



J2 Adami and Chapin, Jour. Med. Res., xl, 1904. 



