31.11: Urease Test
- Page ID
- 165421
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The Urease test is used to determine whether a bacterial organism produces the enzyme urease, which catalyzes the hydrolysis of urea into ammonia and carbon dioxide. This test is especially useful in identifying certain enteric bacteria and is often included in diagnostic workflows to distinguish among members of the Enterobacteriaceae family.
Urease activity results in the accumulation of ammonia, a basic compound that raises the pH of the medium. The urea broth contains a pH indicator, phenol red, which is yellow-orange under neutral conditions and turns bright pink or violet in an alkaline environment. A positive test is indicated by a color change from the original pale yellow to bright pink or magenta, reflecting the presence of ammonia and confirming urease activity.
Organisms that produce urease rapidly, such as Proteus species, can cause a noticeable color change within just a few hours. Slower urease producers may require a longer incubation period to achieve a visible result. The test is particularly useful in clinical settings, as urease-producing bacteria are often associated with urinary tract infections. These organisms can thrive in the urinary environment by alkalinizing their surroundings, contributing to the characteristic ammonia odor of stale urine.
Attribution: Sources from 12: Protein Metabolism of Unknowns is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Valeria Hochman Adler.
Procedure
- Inoculate a small amount of the test culture into the urea medium. Avoid using much inoculum. Inoculating too much of the inoculum may overwhelm the system resulting in an inaccurate result.
- Incubate at 30°C for 48 hours.
Interpretation of Results
- Bright pink or magenta broth: positive result, indicating urease production and ammonia accumulation
- No color change (yellow or light orange broth): negative result, indicating no urease activity or activity below detectable levels
Attribution: Sourced from 12: Protein Metabolism of Unknowns is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Valeria Hochman Adler.