Oxoid™ Fraser Broth Base 500g

PALCAM Agar Base (Dehydrated) is a highly selective medium designed for the detection and isolation of Listeria monocytogenes from food samples. It incorporates a dual indicator system to facilitate the clear differentiation of L. monocytogenes based on aesculin hydrolysis, mannitol non-fermentation, and associated pH changes.

Listeria monocytogenes is the most common pathogenic species within the Listeria genus and is known to cause illness in both humans and animals. The formulation of PALCAM Medium is based on the method described by Van Netten et al.¹, and is widely recommended for recovering L. monocytogenes from food products.

Features and Benefits

• Highly selective formulation: The inclusion of lithium chloride, ceftazidime, polymyxin B, and acriflavine hydrochloride suppresses the growth of competing organisms, enhancing selectivity for Listeria monocytogenes.

• Clear colony differentiation:

  • L. monocytogenes forms brown to black colonies with a black halo due to aesculin hydrolysis in the presence of ferrous iron.

  • Mannitol-fermenting flora, such as staphylococci and enterococci, produce yellow colonies through a color shift in phenol red, the pH indicator.

Dual Indicator System

• Aesculin + Ferrous Iron – Detects aesculin hydrolysis (black halo)

• Mannitol + Phenol Red – Detects mannitol fermentation (yellow color change)

This combination enables precise and reliable identification of L. monocytogenes, even in the presence of background flora.