170 DIFCO MANUAL 



One pound of Bacto-Lead Acetate Agar will make 12.6 liters of medium. 



1 Dissert. St. Petersburg, 1897. * J. Bact., 7:343:1922. 



2 J. Infectious Diseases, 21:554:1917. ^ J. Bact., 32:135:1936. 



3 Pure Culture Study of Bacteria, i:No. 8:1933. 



BACTO 



UREA BROTH (B272) 



DEHYDRATED 



Bacto- Yeast Extract 0.1 g. 



Monopotassium Phosphate 9.1 g. 



Disodium Phosphate 9.5 g. 



Urea, Difco 20 g. 



Bacto-Phenol Red 0.01 g. 



Bacto-Urea Broth is recommended for the identification of the genus Proteus. 

 It is prepared according to the formula of Stuart, Van Stratum and Rustigian^ 

 and provides all the essential growth factors for Proteus. 



The decomposition of urea by members of the Proteus group has been espe- 

 cially helpful to differentiate these organisms from other Gram negative intestinal 

 bacteria and to eliminate them from further study in various schema for the 

 identification of the Gram negative intestinal pathogens. Using their strongly 

 buffered medium, and under proper conditions, Stuart, Van Stratum and Rusti- 

 gian, reported that Proteus could be differentiated from all other members of 

 the enteric group by its ability to produce sufficient ammonia to give a reaction 

 more alkaline than pH 8.1 after 12-48 hours incubation at 37 °C. These investi- 

 gators pointed out that a large number of organisms other than Proteus were 

 capable of urease production and would give a positive test in weakly buffered 

 media. They also noted that by decreasing the amount of buffer in their standard 

 medium to one tenth or one hundredth that of the original concentration, the 

 time of incubation for identification of Proteus could be decreased from 12-48 

 hours to 2-4 hours. Rustigian and Stuart^ used urea decomposition as a limiting 

 characteristic for the identification of Proteus strains from other members of the 

 family Enter obacteriaceae. Ferguson and Hook^ also reported that urease pro- 

 duction, as indicated by the Rustigian and Stuart method, was an excellent means 

 of differentiating between members of the Proteus and Salmonella groups. 



According to the procedure recommended by Stuart, Van Stratum and Rusti- 

 gian^, the filter sterilized medium is distributed under aseptic conditions in 

 approximately 3 ml. amounts in tubes 14 mm. inside diameter and 125 mm. long. 

 Inoculation is made with a straight needle from 18-24 hour agar slant cultures, 

 and the tubes are incubated at 37° C. When possible, reactions are recorded after 

 8, 12, 24 and 48 hours incubation. A positive urease reaction (hydrolysis of urea) 

 is indicated by a change in color from yellow (pH 6.8) to a red to a cerise color 

 (pH 8.1 or more alkaline). 



To rehydrate the medium, dissolve 38.7 grams Bacto-Urea Broth, Dehydrated, 

 in 1000 ml. of distilled water, filter sterilize and distribute under aseptic condi- 

 tions in 3 ml. amounts into sterile plugged 14 x 125 mm. tubes. Final reaction 

 of the medium will be pH 6.8. 



One pound of Bacto-Urea Broth, Dehydrated, will make 11.7 liters of medium. 



ij. Bact., 49:437:1945. ^J- Lab. Clin. Med., 28:1715:1943. 



aProc. Soc. Exp. Biol. Med., 53:241:1943. 



