Cat. no. K650 Urease Test Tablets 50 tablets/bottle


Several species of Enterobacteriaceae, including Proteus, Klebsiella, and some Citrobacter species, as well as some Haemophilus species and several other bacteria, fungi, and yeast species produce the enzyme urease. This enzyme hydrolyzes urea into ammonia, water and carbon dioxide.(1) Since most stool pathogens, particularly Salmonella, Shigella, and Escherichia coli, are urease-negative, it can be useful to determine an organism's urease activity. A notable exception to this is Yersinia enterocolitica, which is urease-positive. Urease Test tablets indicate the presence of the alkaline ammonia end product by a color change from straw color to pink or red.


Each tablet contains 10.0mg of urea or less than 2.0mg of urea. This product does not contain any material known at this time to be hazardous.


Urease test tablets require preliminary growth on certain culture media. Consult a reference manual such as the Manual of Clinical Microbiology for the appropriate media to use.

Test tubes
Loop for harvesting colonies
Distilled water, neutral pH


Urease tablets should be tested prior to use with organism of known reactivity. Discard used tests in a manner conforming with accepted laboratory procedures for biohazardous materials.


1. Add Urease Test Tablet to 1ml of distilled water in a small test tube.

2. Inoculate heavily from a culture grown on a slant or plate. Kligler, Russell, or TSI Agar may be used without affecting the results.

3. Incubate at 37ºC. (Proteus spp. give a positive test in 1-8 hours. Some Klebsiella spp. strains produce urease in smaller amounts and may require up to 24 hours to show a positive reaction. Any pink or red color is a positive result).


Organism Reaction % Positive
Citrobacter spp. (+) (78)
Edwardsiella spp. (-) (0)
Enterobacter spp.* (-) (10)
Escherichia coli (-) (1)
Hafnia spp. (-) (0)
Klebsiella pneumoniae (+) (96)
Morganella spp. (+) (98)
Proteus mirabilis (+) (98)
Proteus vulgaris (+) (98)
Providencia spp.* (+/-) (30)
Salmonella spp. (-) (99)
Shigella spp. (-) (0)
Yersinia spp.* (+) (80)

* Reactions vary within spp.

Positive Urease Test

Proteus vulgaris (ATCC® 13315) suspension incubated with a Urease Test Tablet (Cat. no. K650) for one hour at 35ºC. The pink color change was indicative as a positive urease test.

Negative Urease Test

Escherichia coli (ATCC® 25922) suspension incubated with a Urease Test Tablet (Cat. no. K650) for 24 hours at 35ºC. No pink color change was indicative as a negative urease test.


1. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.