Urea Agar Base (Christensen) (Autoclavable)
This medium detects urease activity by all rapidly urease-positive Proteus organisms and also by other members of Enterobacteriaceae that exhibits a delayed urease reaction. Prolonged incubation may cause alkaline reaction in the medium. A medium without urea serves as negative control to rule out false positive results. Also, all urea test media rely on the alkalinity formation and so they are not specific for determining the absolute rate of urease activity. The utilization of proteins may raise the pH to alkalinity due to protein hydrolysis and excess of amino acids liberation results in false positive reaction.