A modification of Fraser Broth Base, this medium was developed by Fraser and Sperber for the rapid detection ofListeriafrom food and environmental samples. The addition of Ferric Ammonium Citrate allows for the selective enrichment ofListeriaspp. 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 forListeriagrowth. All members of theListeriaspp. hydrolyze Esculin to 6,7-dihydroxycoumarine. This compound reacts with Ferric Ammonium Citrate, resulting in the blackening of the medium.