Download User's Guide

DIATABS ™
05-2007 Ch. 3
Page 117 of 130
3.41 UREASE (URE)
REF No. 57511
The hydrolysis of urea is catalyzed by a specific enzyme, urease, to yield two molecules of ammonia. In the presence of
the indicator phenol red there is a change of colour from yellow/orange to red/ purple in case of a positive reaction.
Procedure
Prepare a dense “milky” suspension (at least McFarland No. 4) from the strain to be tested in 0.25 ml saline in a tube.
Add one Urease diagnostic tablet, close the tube and incubate at 35-37 °C for 4 hours or 18-24 hours.
Reading of the test
Positive reaction:
Negative reaction:
Red/purple
Yellow/orange
After overnight incubation only strong red or purple should be considered as a positive reaction!
Results
1) Enterobacteriaceae
The rapidity by which there is a change of colour (urease pos.) may have a diagnostic interest.
Morg. morganii show in most cases a positive reaction within 30 min.
The following species of Enterobacteriaceae usually show a positive reaction within 4 hours: Proteus spp.,
Morg. morganii, Enterobact. gergoviae.
Klebsiella pneumoniae/Klebs. oxytoca and Yersinia spp. show also a positive reaction, but in most cases after
overnight incubation.
The remaining Enterobacteriaceae show a negative reaction.
2) Staphylococci
The following staphylococci usually show a positive reaction:
Staph. epidermidis, Staph. hominis, Staph. warneri, Staph. simulans, Staph. saprophyticus, Staph. xylosus, Staph.
aureus (V), S. lugdunensis (V), Staph. capitis subsp. ureolyticus, Staph. cohnii subsp. urealyticum.
The following staphylococci show a negative reaction:
Staph. capitis, Staph. haemolyticus, Staph. auricularis, Staph. schleiferi, Staph. cohnii, Staph. sciuri, Staph. lentus.
3) Non-fermenters
The following non-fermenters usually show a positive reaction:
Flav. odoratum, Ochrobactrum anthropi (Group Vd), Sph. multivorum, CDC group IV c-2, Oligella ureolytica
(IVe), Bordetella bronchiseptica, Agrob. tumefaciens (radiobacter).
4) Differentiation of Actinobacillus from Pasteurella
Actinobacillus spp.
Pasteurella spp.
URE
+
0+
IND
0
+
ONPG
+
0
URE = Urease D.T., IND = Indole D.T.
5) Useful in identification of gram-negative anaerobes:
Bact. ureolyticus (+), Bilophila spp. (+0), Desulfomonas pigra (V). Others are negative.
© Copyright Rosco Diagnostica A/S