DEHYDRATED CULTURE MEDIA 171 



BACTO 



UREA BROTH CONCENTRATE (B280) 

 (Filter Sterilized Solution) 



Bacto-Urea Broth is also supplied in a filter sterilized concentrated solution as 

 Bacto-Urea Broth Concentrate. The dehydrated medium is recommended for 

 those laboratories using large amounts of medium and equipped with filter 

 sterilizing apparatus. For laboratories requiring only small amounts of medium 

 Bacto-Urea Broth Concentrate is recommended. 



Bacto-Urea Broth Concentrate is a filter sterilized concentrated solution of 

 Bacto-Urea Broth, 10 ml. being sufficient for the preparation of 100 ml. final 

 medium. It is especially recommended for use by those laboratories desiring to 

 save time, or requiring smaller quantities of medium. 



To prepare the medium from Bacto-Urea Broth Concentrate, add the contents 

 of one 10 ml. tube of Bacto-Urea Broth Concentrate to 90 ml. of sterile cold 

 distilled water, under aseptic conditions. The distilled water should be sterilized 

 in the autoclave for 15 minutes at 15 pounds pressure (121°C.). The water must 

 be cooled to below 55 °C. before adding Bacto-Urea Broth Concentrate. This 

 complete medium is distributed under aseptic conditions in 3 ml. amounts into 

 sterile plugged 14 x 125 mm. tubes. 



One 10 ml. tube of Bacto-Urea Broth Concentrate will make 100 ml. of 

 medium. 



BACTO 



UREA AGAR BASE (B283) 



DEHYDRATED 



Bacto-Peptone 1 g. 



Bacto-Dextrose 1 g. 



Sodium Chloride 5 g. 



Monopotassium Phosphate 2 g. 



Urea, Difco 20 g. 



Bacto-Phenoi Red 0.012 g. 



Bacto-Urea Agar Base is recommended for use in the preparation of a differ- 

 ential medium for the detection of Proteus and most members of paracolon 

 aerobacter and paracolon intermediate groups. It aids in the elimination of these 

 cultures from further study in schema for the identification of intestinal patho- 

 gens. 



Christensen^ considered the well buffered liquid Urea Medium described by 

 Rustigian and Stuart,^ as discussed under Bacto-Urea Broth above, as being 

 suited only for the identification of Proteus. However, other Gram negative in- 

 testinal bacteria which are capable of splitting urea cannot do so in this medium 

 because of the small amount of nutritive material and increased amount of buffer 

 present. In order to overcome these limitations, Christensen^ devised the Urea 

 Agar Medium in which he included peptone and dextrose and reduced the buffer 

 content. His medium supported a more vigorous growth of many of the Gram- 

 negative enteric bacilli and readily permitted observation of urease production 

 by Proteus and members of the paracolon aerobacter and paracolon intermediate 

 groups. 



Ewing^ used Urea Agar as a differential medium in the examination of many 

 cultures from stool specimens and confirmed the findings of Christensen. Ewing 

 and Bruner* utilized the urease reaction as a screening medium in the selection 



