Urease

Sample type:

A biopsy of mucosa is taken from the antrum of the stomach.

Uses:

1) This test is used to differentiate organisms based on their ability to hydrolyze urea with the enzyme urease.

2) This test can be used as part of the identification of several genera and species of Enterobacteriaceae, including Proteus, Klebsiella, and some Yersinia and Citrobacter species, as well some Corynebacterium species.

3) It is also useful to identify Cryptococcus spp., Brucella, Helicobacter pylori, and many other bacteria that produce the urease enzyme.

4) Directly, this test is performed on gastric biopsy samples to detect the presence of H. pylori.

Precautions:

1) Some organisms rapidly split urea (Brucella and H. pylori), while others react slowly.

2) When performing overnight tests from medium that contains peptone, the alkaline reaction may be due not to urease but to hydrolysis of peptone.

3) Urea is light sensitive and can undergo autohydrolysis. Store at 2 to 8°C in the dark.

4) The test is less sensitive if the medium is not buffered.

Interfering Factors:

1) Prolonged incubation times a false-positive alkaline reaction may be seen.

2) Failure to incubate this medium with loose caps may cause erroneous results to occur.

3) Urea is light sensitive and can undergo autohydrolysis. Store at 2 to 8C in the dark.

Pre analytical errors:

1) The biochemical and/or serological tests be performed on colonies from unpure culture lead to incomplete identification.

2) Put urea reagent in light in light, urea is light sensitive and can undergo autohydrolysis.

Corrective action:

1) After prolonged incubation times a false-positive alkaline reaction may be seen. To rule out this occurrence, check the test with a control (an uninoculated tube of Urea Agar) along with the inoculated tube during prolonged incubation.

2) Do not heat the Urea Agar Slants, as urea decomposes very readily when heated.

3) To detect Proteus species, the Urea Agar, Slants must be examined within 6 hours of inoculation for a reaction.

Post analytical errors:

1) Send the report to the wrong person.

2) Write wrong results in report.

Corrective action:

1) Send the report to the right person.

2) Write correct results in report.