Demi Fraser Broth Base
A modification of Fraser Broth Base, this medium was developed by Fraser and Sperber for the rapid detection of Listeria from food and environmental samples. The addition of Ferric Ammonium Citrate allows for the selective enrichment of Listeria spp. Enzymatic Digest of Casein, Beef Extract, and Yeast Extract provide nutrients like amino acids, peptides, carbohydrates and vitamins for bacterial growth. Esculin is the main energy source. Sodium Chloride provides essential electrolytes and maintains the osmotic equilibrium. Disodium Phosphate and Monopotassium Phosphate act as pH buffers. Lithium Chloride, Nalidixic Acid and Acriflavine are selective agents for Listeria growth. All members of the Listeria spp. hydrolyze Esculin to 6,7-dihydroxycoumarine. This compound reacts with Ferric Ammonium Citrate, resulting in the blackening of the medium.