Modified McBride Listeria Agar Base is recommended for selective isolation and cultivation of Listeria monocytogenes, from foodtuffs, clinical samples etc. Glycine present in the media inhibits certain gram-negative and gram positive bacteria including Escherichia coli and Enterococcus faecalis, the common accompanying contaminants. Listeria colonies are dense white to iridescent white appearing as crushed glass. Small colonies tend to be blue, while non- Listeria show yellowish orange colonies that are further purified.