Simmons citrate agar tests the ability of organisms to utilize citrate as a carbon source. Simmons citrate agar contains sodium citrate as the sole source of carbon, ammonium dihydrogen phosphate as the sole source of nitrogen, other nutrients, and the pH indicator bromthymol blue.
This test is part of the IMViC tests and is helpful in differentiating the Enterobacteriaceae . If the medium turns blue, the organism is citrate positive. If there is no color change, the organism is citrate negative. Some citrate negative organisms may grow weakly on the surface of the slant, but they will not produce a color change.
- A: Example of citrate – bacterium – E. coli, S. typhi
- B: Example of citrate + bacterium – Klebsiella
Simmons citrate agar test
