6i2 Typhoid Fever 



Jackson* prepares a medium for water examination when typhoid 

 and colon bacilli are suspected. It consists of undiluted ox-bile to 

 which I per cent, of peptone and i per cent, of lactose are added. 

 It is filled into fermentation- tubes of 40 cc. capacity and sterilized in 

 the Arnold apparatus. If fresh ox-bile cannot be secured, an 11 per 

 cent, solution of dry ox-bile can be made; 10 cc. of suspected water 

 or milk are planted in the tubes of this medium. The contained 

 micro-organisms grow rapidly, t)^hoid bacilli outgrowing all 

 others, and not fermenting the sugar; rapid fermentation and 

 copious gas-formation take place if colon bacilli are present. 



An excellent medium suggested by MacConkeyf has the following 

 composition: 



Agar I . S grams 



Sodium taurocholate 0.5 gram 



Peptone 2.0 grams 



Water 100. o cc. 



It is boiled, clarified, and filtered as usual, then receives an addition of i.o 

 gram of lactose, is tubed, and then sterilized three times on successive days. 



For determining fermentation by colon bacilli the same investiga- 

 tor advises a broth composed of : 



Sodium taurocholate (pure) 0.5 gram 



Peptone 2.0 grams 



Glucose 0.5 gram 



Water 100. o cc. 



Boil, filter, add sufficient neutral litmus, fill into fermentation-tubes, and steril- 

 ize at ioo°C. Colon colonies appear red; typhoid, blue. 



In a careful study of the bile-salt media MacConkeyf points out an 

 error, first discovered by Theobald Smith, that depends upon the 

 alkali production of the colon bacillus in the absence of sugar. If 

 too little sugar be added to the medium, the alkali production masks 

 the acid production unless the oxygen be removed, and red colonies 

 of the colon bacillus grown upon the medium may in time turn dis- 

 tinctly blue. It becomes obvious, therefore, that the medium 

 should be as neutral as possible to the indicator used. After trial he 

 found neutral red preferable to 'litmus, and makes the medium as 

 follows: 



I . A stock solution is made : 



Sodium taurocholate (commercial from ox-bile and 



neutral to neutral red) 0.5 per cent. 



Peptone (Witte's) 2.0 per cent. 



Water (distilled or tap) 100. o cc. 



(As calcium 0.03 per cent, is favorable to the growth of the organisms, 



it should be added if distilled water is used.) 



The ingredients should be mixed, steamed in a steam sterilizer for one to two 

 hours, filtered while hot, allowed to stand twenty-four to forty-eight hours, then 

 filtered cold through paper. A clear solution should then result, which will keep 

 indefinitely under proper conditions. The various bUe-salt media are prepared 



* "Biological Studies of the Pupils of W. T. Sedgwick," 1906, University of 

 Chicago Press. 



t"The Thompson-Yates Laboratory Reports," III, p. 151. 

 t "Journal of Hygiene," 1908, viii, p. 322. 



