The proprietary BCM Listeria monocytogenes Plating Medium contains a substrate for phosphotidylinositol-specific phospholipase C (PlcA) enzymes that differentiates L. monocytogenes and L. ivanovii from other Listeria species. It can be obtained commercially as a dehydrated basal medium plus supplements. Differential activity for all Listeria species is due to the addition of a chromogenic substrate. One source is Biosynth International, Inc., Naperville, IL.