Fraser Broth

Fraser Broth Base is a liquid medium used for the selective enrichment of?Listeria?spp. This broth was first described by Fraser and Sperber, and is utilized with a Ferric Ammonium Citrate supplement for the rapid detection of?Listeria?from food and environmental samples. Tryptose, 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 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, thus resulting in the blackening of the medium.