Use AL (Agar Listeria according to Ottaviani and Agosti) Agar for the detection and enumeration of Listeria spp., including L. monocytogenes and L. ivanovii, in food products and environmental samples. The chromogenic identification and differentiation of Listeria spp. is based on both PI-PLC phosphatidylinositol-specific phospholipase C) and of β-D-glucosidase (β-gal) activities.