Description

Listeria monocytogenes is the most common pathogenic Listeria spp. and has been shown to be pathogenic to both man and animals. Some Listeria ivanovii strains also possess lecithinase activity and, although Listeria ivanovii are primarily pathogenic to animals, there are strains which have been shown to cause infection in humans.

Brilliance Listeria Agar uses the chromogen X-glucoside for presumptive identification of Listeria spp. This chromogen is cleaved by β-glucosidase which is common to all Listeria species. Other organisms that possess this enzyme, such as enterococci, are inhibited by the selective agents within the medium; lithium chloride, polymyxin B and nalidixic acid, while amphotericin inhibits the growth of any yeasts and moulds present in the sample. Listeria monocytogenes and pathogenic Listeria ivanovii are then further differentiated by their ability to produce the phospholipase enzyme, lecithinase. This enzyme hydrolyses the lecithin in the medium, producing an opaque white halo around the colony.

Brilliance Listeria Agar is a modification of the formulation described by Ottaviani and Agosti. As in the original formulation, the medium is designed to identify Listeria spp. based on their utilization of a chromogenic substrate. However, in this modification, the pathogenic Listeria spp. are then further differentiated by the detection of lecithinase (phosphotidylcholine phospholipase C (PCPLC) activity, rather than phosphotidylinositol phospholipase C (PIPLC) activity. Both enzymes, PCPLC and PIPLC, are associated with virulence in Listeria spp., and, therefore, the presence of either enzyme is a useful indicator of pathogenicity. Also available Chromogenic Listeria Selective Supplement, Part No. SR0227E and Chromogenic Listeria Differential Supplement, Part No. SR0228E.

Appearance

• Dehydrated medium: Straw coloured, free-flowing powder
• Prepared medium: Translucent, white gel

Quality Control

Positive Controls - Expected Results: 

• Listeria monocytogenes ATCC™ 7644™ - Good growth; blue/green colonies with haloes
• Listeria innocua ATCC™ 33090™ - Good growth; blue/green colonies with no halo

Negative Control - Expected Results:

• Enterococcus feacalis ATCC™ 29212™ - Inhibited

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