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. There is a choice of 3 sizes - 500g, 2kg, and 10kg.

PREPARATION: Mix 55 grams of the medium in one liter of purified water until evenly dispersed. Distribute and autoclave at 121°C for 15 minutes. Cool to room temperature. Aseptically add 10mL of Fraser Broth Supplement.