It is chromogenic differential medium for selective isolation of Shiga toxin producing Escherichia coli from clinical and nonclinical samples. Chromogenic mixture in the medium imparts mauve to
purple colour to Shiga toxin producing Escherichia coli strains. Shiga toxin producing Escherichia coli O157 are usually non fluorescent while
Shiga toxin producing Escherichia coli non O157 are fluorescent while a few may not fluoresce.