Citrate utilization is a metabolic test used to determine an organism’s ability to utilize citrate as its lone source of carbon. Simmons citrate agar is a synthetic medium containing citrate, ammonium ions, and the pH indicator bromthymol blue. This indicator is green below pH 7.6 and blue above pH 7.6.

Why is the citrate utilization test important?

The citrate test is performed along with the other IMViC tests to differentiate Gram-negative bacilli of the Enterobacteriaceae family. It is an important test that allows the species-level identification of the members of the Enterobacteriaceae family.

What organisms are positive for citrate utilization?

Klebsiella pneumoniae and Proteus mirabilis are examples of citrate positive organisms. Escherichia coli and Shigella dysenteriae are citrate negative.