Oxford Listeria Agar, with addition of antibiotics, is used for the selective isolation ofListeriamonocytogenesfrom food. This medium is utilized with a Ferric Ammonium Citrate supplement for the rapid detection ofL. monocytogenesfrom food and environmental samples. Columbia Blood Agar Base is a general-purpose growth medium. Esculin is the main energy source. All members of theListeriaspp. hydrolyze Esculin to 6,7-dihydroxycoumarine. This compound reacts with Ferric Ammonium Citrate, resulting in the blackening of the medium. Selectivity forListeriais achieved through the Lithium Chloride included in the formulation and the addition of sterile antimicrobiotic supplements.L.monocytogenesis typically visible after 24 hours, but continued incubation may allow for the detection of slower growing strains.