DEHYDRATED CULTURE MEDIA 85 



mination of proteolytic activity of organisms, and for carrying stock cultures of 

 anaerobes. 



The use of a combination of meat and egg white as a culture medium was 

 reported by Rettger^ in his studies on Escherichia coli and Aerobacter aerogenes. 

 Later he^ described the use of this medium in studies of intestinal putrefaction. 

 In 1923, Reddish and Rettger^ used it in their detailed study of Clostridium 

 putrificurn, and in the following year they* employed it in a study of other spore- 

 forming anaerobes. 



The medium is prepared from fresh meat and egg white, retaining the coagu- 

 lated portion of the meat and egg white as a part of the medium. The experi- 

 ments of Reddish and Rettger, using twelve different spore-forming anaerobes, 

 indicate that a final reaction of pH 7.0 is satisfactory for the organisms, and that 

 the range of pH 7.0-7.4 favors abundant growth and consistent development of 

 typical morphological forms. 



Bacto-Egg Meat Medium was developed with the cooperation of Dr. Reddish. 

 The use of this dehydrated medium eliminates a tedious and disagreeable task 

 that confronted the bacteriologist interested in the study of anaerobes. This 

 medium is of particular value in studies of morphology and the proteolytic 

 properties, as demonstrated by the digestion of meat, of these organisms. Bacto- 

 Egg Meat Medium is recommended for carrying stock cultures of anaerobes, 

 since even when the medium has evaporated to a practically water-free consist- 

 ency the organisms still retain their original pathogenicity, morphological, cul- 

 tural and biochemical characteristics to a remarkable degree. 



To rehydrate the medium, suspend 15 grams of Bacto-Egg Meat Medium in 

 100 ml. distilled water. The suspension is allowed to stand, with frequent agita- 

 tion, for at least 15 minutes or until all the particles are thoroughy wetted. It is 

 essential that this step be adhered to closely, since the final medium will not 

 be sterile unless all the meat particles are thoroughly wetted before heating. 

 An even suspension of the particles should be maintained while dispensing into 

 tubes. The medium is then sterilized in the autoclave for 15 minutes at 15 

 pounds pressure (121°C.). Special precautions must be taken to prevent too 

 quick a decrease in pressure at the end of the sterilization period, since a too 

 rapid cooling of the autoclave produces a vigorous boiling of the medium which 

 results in excessive turbidity of the supernatant liquid and may even occasionally 

 blow the medium and plugs from the tubes. The final reaction of the medium 

 will be pH 7.2. 



If not used immediately after sterilization, the tubes should be heated in a 

 boiling water bath or flowing steam for a few minutes and cooled without agita- 

 tion, just prior to inoculation. 



One pound of Bacto-Egg Meat Medium will make 3 liters of medium. 



»Am. J. Physiol., 8:284:1903. 3 J. Bact., 8:375:1923. 



2 J. Biol. Chem., 2:71:1906. * J. Bact., 9:13:1924. 



BACTO 



COOKED MEAT MEDIUM (B267) 



DEHYDRATED 



Beef Heart 454 g. 



Proteose Peptone, Difco 20 g. 



Bacto-Dextrose 2 g. 



Sodium Chloride 5 g. 



Bacto-Cooked Meat Medium was developed for studies of contaminated 

 wounds carried on by investigators working under contract with the Office of 



