CULTURE MEDIA FOR CULTIVATION OF MICROORGANISMS 



541 



1757. Bacto Litmus Lactose Agar 

 (Dehydrated) 



Constituents: 



1. Distilled water 



2. Beef extract (Bacto) 3.0 g. 



3. Peptone (Bacto) 5.0 g. 



4. Agar (Bacto) 10.0 g. 



5. Lactose (Bacto) 10.0 g. 



6. Azolitmin 10 g. 



Preparation : 



(1) Dissolve 29.0 g. of Bacto Litmus 

 Lactose Agar (Dehydrated) in 1000 

 cc. of distilled water by boiling or 

 autoclaving. 



(2) Restore the loss if necessary. 



(3) If sterilized at 15 pounds for 20 

 minutes pH = 7.0±. 



Sterilization : Sterilize in the usual manner. 

 Use: To determine fermentation of lactose. 

 Reference: Digestive Ferments Co. (1925 

 p. 12). 



1758. A.P.H.A, Litmus Lactose Extract 

 Agar (1917) 



Constituents: 



1. Distilled water 1000.0 cc. 



2. Beef extract 3.0 g. 



3. Peptone 5.0 g. 



4. Agar 12.0 g. 



5. Lactose (1.0%) 10.0 g. 



6. Litmus 100.0 cc. 



Preparation : 



(1) Add 3.0 g. beef extract, 5.0 g. peptone 

 and 12.0 g. agar, dried for 30 minutes 

 at 105°C. before weighing, to 1000.0 

 cc. distilled water. 



(2) Boil over a water bath until solution 

 is complete. Make up lost weight. 



(3) Cool to 45°C. in a cold water bath and 

 warm to 65°C. in the same bath 

 without stirring. 



(4) Restore lost weight, titrate and 

 adjust the reaction to neutral to 

 phenolphthalein. 



(5) Filter thru cloth and cotton until 

 clear. 



(6) Add 1.0% lactose. 



(7) Tube in 10.0 cc. quantities. 



(8) Add 1.0 cc. of sterilized litmus or 

 azolitmin solution to each 10.0 cc. of 

 sterile agar just before it is poured 

 into the Petri dish. The mixture 

 may occur in the plate itself if desired. 



Sterilization: Sterilize (6) in the autoclave 

 at 15 pounds pressure (120°C.) for 15 

 minutes. 



Use: To determine the fermentation of 

 lactose. 



Variants: The following investigators pre- 

 pared similar media as indicated below: 



(a) Meyer. 



(1) Dissolve 10.0 g. peptone, 10.0 g. 

 meat extract and 30.0 g. agar (3.0%) 

 in 1000.0 cc. of water. 



(2) Distribute in 400.0 cc. portions. 



(3) Sterilization not given. 



(4) To each 400.0 cc. lot add 16.0 g. 

 of a sterile 25.0% lactose solution 

 and 12.0 cc. of a sterile 8.0% litmus 

 solution. 



(5) Pour into sterile plates and allow to 

 harden in open air. 



(b) Bendick (Tanner). 



(1) Dissolve 15.0 g. agar, 5.0 g. beef 

 extract, 10.0 g. NaCl and 10.0 g. 

 peptone in 1000.0 cc. of water. 



(2) Clarify with egg and filter. 



(3) Adjustment of reaction is not 

 necessary. 



(4) Distribute in 250.0 cc. lots in 500.0 

 cc. flasks. 



(5) Add 1.0 g. CaCOa to each flask. 



(6) Sterilize— method not given. 



(7) Add 25.0 cc. of Kahlbaum's aqueous 

 litmus solution and 5.0 g. lactose to 

 each flask. 



(8) Tube by pouring directly into the 

 tube from the flask, keeping the 

 contents mixed well. 



(c) Stitt. 



(1) Prepare nutrient agar by dissolving 

 5.0 g. Liebig's extract, 5.0 g. NaCl, 

 10.0 g. peptone and 30.0 g. agar in 

 1000.0 cc. water. 



(2) Adjust the reaction to or +0.2 

 to phenolphthalein. 



(3) Keep this agar base in 100.0 cc. 

 quantities in Erlenmeyer flasks. 



(4) Color 100.0 cc. of neutral agar base 

 to a lilac color with azolitmin. 



(5) Add 5.0 cc. of a hot freshly prepared 

 20.0% lactose solution in distilled 

 water. 



(6) Tube in 10.0 cc. quantities or dis- 

 tribute in 50.0 or 100.0 cc. Erlen- 

 meyer flasks. 



(7) Sterilize in the autoclave at 10 



