Thermo Scientific™ PALCAM Agar Base (Dehydrated)

Listeria monocytogenes is the most common pathogenic Listeria spp. and has been shown to be pathogenic to both humans and animals. PALCAM Medium is based on the formulation described by Van Netten et al.¹ and is recommended for the isolation of Listeria monocytogenes from foods.

• Selective: the addition of lithium chloride, ceftazidime, polymyxin B and acriflavine hydrochloride make the medium highly selective for Listeria monocytogenes.
• Easy-to-read: monocytogenes forms brown/black colonies with a black halo while mannitol positive accompanying flora, such as staphylococci and enterococci, grow as yellow colonies.

PALCAM Medium allows easy differential diagnosis of L. monocytogenes by utilizing the double indicator system.

1. Aesculin and ferrous iron
2. Mannitol and phenol red

Listeria monocytogenes hydrolyses aesculin resulting in the formation of a black halo around colonies. L. monocytogenes does not ferment mannitol so can be easily differentiated from contaminants, such as enterococci and staphylococci, which ferment mannitol producing a change from red to yellow in the pH indicator phenol red.

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