Jul 7, 2011
Listeria monocytogenes (left) and Listeria innocua (right), both on Oxford Agar. Listeria bacteria are the causative agents of listeriosis, a relatively rare food-borne illness.
Oxford Agar "is selective and diagnostic and used for the detection of Listeria. The selective and inhibitory components included in the medium are lithium chloride, acriflavin, colistin sulphate, cefotetan, cycloheximide and phosphomycin. Gram-negative and most Gram-positive bacteria are inhibited. The medium contains ferrous ions and aesculin, the latter of which Listeria hydrolyses producing black zones under and around the colonies." (source)