Simmons Citrate Agar

Simmons Citrate Agar is used as a differential medium for the identification of enteric bacteris, using citrate as the sole source of carbon. Koser developed a fluid medium to determine citrate utilization with Simmon further modifying the formula by adding 1.5% agar and bromthymol blue as an indicator. The medium can be used to distinguish between Escherichia coli and Enterobacter aerogenes and to assist in differentiating members of the Salmonella genus. Organisms able to metabolize the citrate grow well on the surface of the medium and alkalinize the medium changing it from green to blue.