Urea hydrolysis/ Urease test (Christensen’s method)

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Urea hydrolysis/Urease test is used to detect the ability of an organism to produce urease that hydrolyses urea contained in the medium. Hydrolysis of urea produces ammonia and carbon dioxide  The formation of ammonia makes the medium alkaline and the shift in pH is detected by the change of color of indicator phenol red from light orange (pH 6.8) to pink or magenta color (pH 8.1).
Procedure:
  1. Pick the organism with a straight wire and touch a isolated colony and streak the surface of urea agar or inoculate slant with 1 or 2 drops of overnight incubated brain heart infusion broth.
  2. Leave the cap loose and incubate at 35oC for 48 hours to 7 days.
Expected result:
Positive: change in color of slant from light orange to pink or magenta
Negative: No change in color (color of slant and butt remains light orange)
Quality control:
Positive: Proteus vulgaris

 

Negative: Escherichia coli  

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