Ferric Ammonium Citrate Supplement

This supplement is used in selective media in order to detect the hydrolization of esculin, typical, for example, of Listeria spp.
For this reason this supplement is added to Listeria enrichment broth base in order to obtain Fraser broth or Half Fraser broth.
This medium is also supplemented with specific antibiotics.
In the complete medium any darkness of the medium can be taken as presumptive presence of Listeria , because in the same time the growth of enterococci, which are also able to hydrolyze esculin, is suppressed by the inclusion of lithium chloride and the companion flora is inhibited by Nalidixic acid and Acriflavine hydrochloride .