尿素酶試驗在鑒別沙門氏菌的時候很重要。
　　This image depicts negative and positive results when testing for bacterial production of urease. The negative tube contains Salmonella, while the positive was inoculated with Proteus（變形桿菌）.Urease, an enzyme produced by some organisms, splits urea into ammonia and carbon dioxide. Ammonia, which is alkaline, causes the pH to rise. Phenol red, a pH indicator present in urea broth, turns cerise when the pH rises above 8.1. This slide may be used in a discussion of microbial metabolism as a tool for identifying microorganisms and/or distinguishing between intestinal pathogens (e.g., Salmonella) and nonpathogens (e.g., Proteus).

The age of the culture is 24 h.

Margaret (Peg) Johnson, Mesa Community College, Mesa, Ariz., USA