UREA AGAR BASE (CHRISTENSEN) (IS:5887 (Part-I)-1976)

Urea Agar was described by Christensen which detected urease activity by all rapidly urease-positive Proteus organisms and also by other members of Enterobacteriaceae that exhibited a delayed urease reaction. This is accomplished by
a) adding glucose to the medium
b) decreasing the peptone concentration, and
c) decreasing the buffering system, as a less buffered medium detects even smaller amount of alkali.
ISO Committee has recommended Urea Agar Base, Christensen, with one phosphate, instead of two phosphates for detection of rapid urease activity. Heavy inoculum of growth is inoculated on the surface of the slants. On incubation urea is utilized to form ammonia, which makes the medium alkaline, showing a pink-red colour by the change in the phenol red indicator. Prolonged incubation may cause alkaline reaction in the medium. Check using medium without urea as the negative control.

for detection of urease production, particularly by Proteus vulgaris, Micrococci & paracolon organisms