PALCAM Agar , 250g

Description: 

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. 

The heightened awareness and concern surrounding the presence of Listeria monocytogenes in food has resulted in the development of many media for its isolation^2,3,4,5. However, Cassiday and Brackett⁶ conclude that no single method currently available at the time was suitable for use with all types of food. 

PALCAM Medium is highly selective due to the presence of lithium chloride, ceftazidime, polymyxin B and acriflavine hydrochloride. It allows the easy differential diagnosis of Listeria monocytogenes by utilising 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. Listeria monocytogenes does not ferment mannitol so easy differentiation from contaminants, such as enterococci and staphylococci, can be made as these will ferment mannitol. This formulation produces a change from red to yellow in the pH indicator phenol red. The addition of egg yolk to PALCAM medium has been reported to aid rep air of damaged cells³. 

Incubation under microaerophilic conditions serves to inhibit strict aerobes such as Bacillus spp. and Pseudomonas spp. that might otherwise appear on the medium. A modification to PALCAM medium in which incubated plates are overlaid with medium containing blood enables haemolytic Listeria spp. to be differentiated and enumerated⁷. Incubation under microaerobic conditions serves to inhibit strict aerobes such as Bacillus spp. and Pseudomonas spp. that might otherwise appear on the medium. 

Specification: 

250g