• Christensen modified urea broth is a biochemical fluid medium used to test microorganisms for urease production.
• It can be prepared from a urea broth base available commercially in dehydrated form of culture medium. To this broth base, sterile solution of urea is added.
• Note: if preferred, urea agar (prepared from agar base) can be used as a slope or stab. When providing a narrow bore tube is used. A stab technique gives a more rapid result.

Composition of Christensen urea broth

To prepare about 33 bottles:

• Urea broth base (oxoid )………………………….95 ml
• Sterile urea solution, 40% w/v..………………….5 ml

Preparation of Urea broth:

• Prepare and sterilize the urea broth base as instructed by the manufacturer. Transfer to a 50-55°C water bath.
• When the medium has cooled to 50-55°C, add aseptically the sterile urea solution and mix well.
• Dispense aseptically in 3 ml amounts in sterile Bijou bottles or screw-cap tubes.
• Date the medium and give it a batch number.

Quality control

• pH of medium: this should be within the range pH 6.6-7.0 at room temperature.
• Test the medium with bacterial species of known positive and negative urease reactions.
• Store in a cool dark place or at 2-8°C.

Use of urea broth:

• Used to test organism for urease production
• *for broth medium use a sterile wire loop to inoculate the urea broth medium and for urea agar use a sterile straight wire to inoculate a urea agar stab.

Christensen urea broth (maslen modified):composition, preparation and uses

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