Thanks to the Simmon's agar mineral composition its meets the needs of the microorganisms. But the only source of carbon in the environment is citrate in the form of sodium salt. Due to this environment favors the growth of citrate-positive microorganisms. During their development the waste products raise pH, is manifested by a color change indicator (bronchiology blue) from green to blue. The analysis is conducted within 72 hours, although preliminary results can already be seen in a day.