Urea Broth is a liquid medium used for differentiating Enterobacteriaceae, especially Proteus, based on urease activity. This medium, buffered with Di- and Monopotassium Phosphates, contains Urea and Phenol Red as pH indicator. Urease activity alkalinizes the environment, thus producing a color shift from pale yellow to pink-red. Yeast Extract provides the nitrogenous sources essential for bacterial growth.