Description
Amyl LISTERIA PALCAM Agar, AM 784, is a selective, differential medium designed for the isolation and presumptive identification of Listeria monocytogenes. The medium is formulated according to the specifications of van Netten et al1, and conforms to the specifications required by Standards Australia for the detection of Listeria monocytogenes in food products2.
The composition of PALCAM Agar is based on that of Columbia Agar enriched with yeast extract and glucose, and further supplemented with the carbohydrates mannitol and aesculin as fermentable substrates, the former producing acid when fermented by strains of Staphylococcus, which appear as yellow colonies due to the alteration of Phenol Red indicator, and the latter giving rise to a black halo around colonies of Listeria monocytogenes due to the reaction between aesculitin, a product of aesculin hydrolysis, and the ferric ions of Ferric Ammonium Citrate.
Selective substances incorporated into PALCAM agar include Lithium Chloride and Acriflavine Hydrochloride to inhibit the growth of strains of enterococci and other gram positive cocci, the third generation cephalosporin antibiotic, Ceftazidime, active against a broad spectrum of gram negative organisms, including Pseudomonas sp. and Polymixin B which is also active against Pseudomonas sp.
