Listeria (Oxford) Agar

One of several media available as a selective identification medium for the isolation and identification of Listeria monocytogenes in food & clinical laboratories. Using Columbia Agar as the base Lithium Chloride is included to inhibit enterococci and Acriflavine to inhibit some other gram positive and gram negative organisms that may be present in such specimens. It is made further selective by the addition of the antimicrobials Cefoxitin, Colistin & Fosfomycin with Amphotericin included to inhibit any yeasts present. Aesculin is present as an indicator since Listeria monocytogenes will hydrolyse it and the associated reaction with the Ferric Ammonium Citrate gives rise to a black precipitate around the colonies.