INGREDIENTS OF CULTURE MEDIA 289 



entirely different purpose and is not interchangeable with Bacto-Beef Heart for 

 Infusions. 



1 Am. J. Trop. Med., 12:301:1932. s Am. J. Syphilis Gonorrh. Venereal Diseases, 



2 Diagnostic Procedures and Reagents, 3rd Edi- 35:361:1951- 

 1100:417:1950. 



BAGTO-LIVER (B133) 



Bacto-Liver is prepared from large quantities of carefully trimmed fresh beef 

 liver and is recommended for use in preparing liver infusion media. The nutritive 

 factors of fresh liver tissue are retained in infusions prepared from Bacto-Liver. 



The equivalent of 500 grams of fresh liver is obtained with 135 grams of 

 Bacto-Liver. An excellent infusion can be prepared by using 75, or even 50, grams 

 of Bacto-Liver per 1000 ml. of distilled water. The latter concentration is recom- 

 mended for media for general culture purposes. The infusion is made by warm- 

 ing the mixture to 50° C. and holding it at this temperature with frequent agita- 

 tion for one hour. The mixture is heated to boiling for a few minutes to coagulate 

 a portion of the proteins, and is filtered. Peptone and other ingredients of the 

 medium are then added to the filtrate. After adjustment of the reaction to pH 

 7.5-7.8 and subsequent boiling, there will be a further coagulation which should 

 be removed by filtration before the medium is sterilized. 



BAGTO-VEAL (B134) 



Bacto-Veal is desiccated powdered fresh lean veal, retaining the growth- 

 promoting properties of the fresh tissue, and is recommended for use in the 

 preparation of veal infusion media. 



Eighty-five grams of Bacto-Veal are the equivalent of 500 grams of fresh lean 

 veal. An excellent infusion can be prepared by using 50 grams of Bacto-Veal per 

 1000 ml. of distilled water, but larger quantities may be used if desired. Bacto- 

 Veal should be infused at 50° C. for 1 hour, then heated to boiling for a few 

 minutes to coagulate some of the proteins, and filtered. Peptone and the other 

 ingredients may then be added to the filtrate and the reaction adjusted to pH 

 7.5-7.8. The medium is boiled and filtered before sterilization. 



Veal Broth for the preparation of diphtheria toxin can be prepared by infusing 

 80 grams of Bacto-Veal in 1000 ml. of distilled water at 38°C. for 1 hour. To 

 remove the muscle sugars the infusion is then inoculated with a vigorously grow- 

 ing culture of Escherichia coli and incubated overnight at room temperature. 

 After heating to 85 °C. and filtering, 20 grams of peptone and 5 grams of sodium 

 chloride are added and the reaction adjusted to pH 8.0. The medium is then 

 boiled for 5 minutes, filtered and the filtrate distributed in 100 ml. amounts in 

 300 ml. Erlenmeyer flasks and sterilized in the autoclave for 15 minutes at 15 

 pounds pressure (121°C.). The sterile medium is inoculated with an 18-hour 

 culture of Corynebacterium diphtheriae which has been previously acclimated to 

 the medium. A potent toxin can usually be harvested after incubation at 36°G. 

 for 4-7 days. 



