Listeria Oxford Medium Base, Modified is recommended for isolation and differentiation of Listeria species from clinical and food specimens. Cycloheximide is used to reduce fungal contamination; cefotetan and fosfomycin are inhibitors of bacterial overgrowth. Acriflavin, colistin sulphate and lithium chloride inhibit bacteria other than Listeria species. Alternatively moxalactam (FD266) can be added which inhibits both gram-positive and gram-negative bacteria. Listeria monocytogenes hydrolyses esculin thereby blackening the medium.