Urease Test for Mycobacteria – Principle, Procedure, Media and Results
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Principle Urease is an enzyme possessed by many Mycobacterium species that can hydrolyze urea to form ammonia and carbon dioxide. The ammonia reacts in solution to form ammonium carbonate, resulting in alkalinisation and an increase in the pH of the medium. Specimen Type of Specimen Mature colony of the unknown Mycobacterium species recovered from clinical material, grown on a Lowenstein–Jensen slant. Materials Equipment Biologic safety hood 37°C incubator Medium Urea Broth Preparation Add 10 g of Difco (Detroit, MI) Bacto urea agar base concentrate to 90 mL of sterile deionized water. Mix well to dissolve. Aseptically aliquot 3.0 mL portions into sterile screw-capped test tubes. Store at 2°C–8°C; shelf life is 1 month. Quality Control Positive control: M. kansasii American Type Culture Collection (ATCC) 12478 Negative control: M. avium/M. intracellulare ATCC 13950 Procedure Inoculate each substrate tube with a loopful of growt...