Urease test for Mycobacteria

DESCRIPTION
The method used for determination of urease activity is a modification of one used by Toda and associates, which is based on
pH change associat
ed with the large amount of  ammonia released by urease positive organisms.

PROCEDURE
Difco-Bacto Urea Agar Base (containing no agar)
is diluted 1:10 in sterile water and dispensed in 3-ml amounts to sterile 13- by
100-mm screwcapped tubes. A generous loop or spadeful of growth from a fresh Lowenstein-Jensen culture is suspended in the
substrate solution and incubated at 36 to 37° C for 3 days.
Reaction is positive (urease activity) if a pink color appears within 3 days.
Urea Hydrolysis Test  (Urease Activity)
DESCRIPTION
Testing the ability  to produce urease, an enzyme that hydrolyse urea providing a source of nitrogen for bacteria.
NOTES
False positives may result due to protein hydrolysis when incubation is prolonged.
REFERENCES:
1. H
elgomar Raducanescu, Valeria Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
2. Murray, P.R., Baron, E. J., Jorgensen, J.J., Pfaller, M.A., and Yolken, R.H. Manual of Clinical Microbiology, 8th ed. ASM Press:
Washington, DC, 2003.
3. Lawrence G. Wayne 1973. Simple Pyrazinamidase and Urease Tests for Routine Identification of Mycobacteria. American Review of
Respiratory Disease, Volume 109, Issue 1, 147-151.
Christensen's urea agar
positive (left) & negative (right)
PROCEDURE
Pick a well isolated colony and inoculate medium. Incubate 24 hours at 37 °C.
Reaction is positive if the medium become red (urea is decomposed resulting ammonia which changes the pH).
Antibiogram
Encyclopedia
Culture media
Biochemical tests
Stainings
Images
Movies
Articles
Identification
Software
(c) Costin Stoica
MEDIUM PREPARATION
Composition of Christensen's  urea agar medium:
Glucose ................................................................................1g
Peptone ................................................................................1g
KH2PO4 ...............................................................................2g
NaCl ......................................................................................5g
Phenol red ...................................................................0.012g
Agar ....................................................................................20g
H
2O ad 1000 ml,  pH = 6.8

To base medium add 20 ml urea solution 20% before solidification. Initial color of the
medium must be yellow.
MIU medium may also be used for urease testing. To MIU base medium add 10 ml
urea sol. 40%.
R E G N U M
PROKARYOTAE
Previous page
Back