Positive Tween hydrolysis control: Mycobacterium kansasii. Negative Tween hydrolysis control: Use an unlnoculated tube of substrate.
Testing for urease enzyme activity is important in differentiating entrobacteria. Proteus strains are strong urease producers. Y.enterocolitica also shows urease activity (Weakly a 35-37 Oc) Salmonellae and shigellae do not produce urease.
The test organism is cultured in a medium which contains urea and the indicator phenol red. If the strain is urease-producing, the enzyme will beak down the urea (by hydrolysis) to give ammonia and carbon diaoxide. With the release of ammonia, the medium becomes alkaline as shown by a change iin colour of the indicator to red-pink. The method described is that which uses the combined motility indole urea (MIU) medium, urease production can also be detected by culturing the organisms in Christensen’s urea broth.
Motility indole urea (MIU) medium.
. Using a sterile straight wire, inoculate a tube of sterile MIU medium with a smooth colony of the test organism.