THE PREPARATION OF CULTURE MEDIA 165 



Sharper results' are obtained with this medium if 1 per cent of the 

 Andrade indicator (described above), is substituted for the litmus. When 

 Andrade is used, the final reaction of agar should be about P^ 7.2. It ib 

 best to standardize the reaction against the particular solution of Andrade 

 used. The reaction of the medium is satisfactory when the mixture containing 

 1 per cent of the indicator is red when hot, and colorless when cold. Typhoid 

 ,and paratyphoid A and B, and dysentery, on this medium show colorless 

 growths on the slant, the butts, however, where partial anaerobiosis exists, 

 show a deep red color, due to acid fermentation. Typhoid may be dis- 

 tinguished from paratyphoid A and B by the fact that typhoid, since it 

 ferments glucose without the production of gas, forms no gas bubbles in 

 the butt, whereas, there is gas formation with paratyphoid A and B. Typhoid 

 and dysentery give the identical reaction on Russell's medium colorless growth 

 on the slant, and acid formation without gas in the butt, and must be 

 distinguished by the motility test. There is no reliable way of distinguishing 

 between paratyphoid A and B, unless lead acetate is added to the medium (see 

 below). Krumwiede recommends the addition of 1 per cent saccharose to 

 the 1 per cent lactose, and 0.1 per cent glucose as a means of ruling out 

 some .of the "paratyphoid-like" intermediates that ferment saccharose more 

 rapidly than lactose. The non-pathogenic types fermenting lactose, or lactose 

 and saccharose, which are present in 1 per cent concentrations, produce acid 

 on the slant, as well as in the butt, with the formation of gas^ and are thus 

 easily eliminated. 



Russell Double Sugar Agar with Lead Acetate. 40 The 'best basis for this 

 medium is an infusion agar which has been rendered sugar free and adjusted 

 to P^ 7.4, or neutrality to Andrade indicator. To this medium add 1 per 

 cent Andrade indicator, tube and sterilize in quantities of 5 c.c. to each tube. 



Make up a solution containing 20 per cent lactose and 2 per cent glucose. 

 Sterilize. 



Make up a solution of 0.25 basic lead acetate. Sterilize. 



To each tube of the agar add 0.25 c.c. of the double sugar solution and 

 1 c.c. of the lead acetate solution. 



Add both the solutions to the agar at 60 C. under sterile precautions 

 and slant. 



Typhoid bacilli cause a brown color near the surface of the stab. Para- 

 typhoid "A" and dysentery do not cause any browning. Paratyphoid "B" 

 and other members of the group cause browning. (The volume of agar per 

 tube is not given in the article, but the sugar percentage works out for 5 c.c.) 



40 Kligler, Jour, of Experimental Medicine, September, 1918. 



