544 APPLICATION OF METHODS OF BACTERIOLOGY 



Boil and render neutral to phenolphthalein. 

 Add 1 gram of anhydrous sodium carbonate; boil and 

 filter through double filter paper. Add : 



Saccharose 5 grams 



Phenolphthalein (sat. sol. in 50 per cent, alcohol) 5 c.c. 



Tube and sterilize by steam at 100 C. 



The phenolphthalein in this alkaline solution gives to the 

 tubes a bright, rose-red color. 



As the vibrios ferment saccharose rapidly, with resultant 

 acid production, the tubes containing them are quickly 

 decolorized. One, therefore, discards all tubes that are 

 not decolorized after eight hours at. 37 C. Those that are 

 decolorized may contain cholera vibrios or other closely 

 allied spirilla or any of the group of bacteria having the 

 power to ferment saccharose. The isolation of the cholera 

 spirilla from this possible mixture is now accomplished by 

 differential or selective plating. 



3. Of the many differential plating media recommended, 

 that which gives uniformily satisfactory results is the 

 alkaline egg medium recommended by Krumwiede, Pratt 

 and Grund, 1 and slightly modified by Goldberg: 2 



(a) Alkaline Egg Solution. Beat up a whole egg with an 

 equal volume of distilled water. Mix an equal volume of 

 this with an equal volume of 6.5 per cent, solution of anhy- 

 drous sodium carbonate and steam for from one-half to one 

 hour. 



(b) Meat extract-glucose-agar 



Distilled water . 1000 c.c. 



Meat extract (Liebig) 3 grams 



Peptone (Witte) 10 grams 



Sodium chloride (c. p.) 5 grams 



Glucose 1 gram 



Agar-agar 30 grams 



1 Jour. Infect. Dis., 1912, x, 134. 



2 U. S. Pub. Health Service, Hygiene Lab. Bull., 1913, No. 91, p. 19. 



