Fraser Broth Base
Fraser Broth Base is used with Fraser Broth Supplement in selectively enriching and detecting Listeria.
Principles Peptones, beef extract and yeast extract provide nitrogen, vitamins and minerals. Sodium phosphate and potassium phosphate are buffering agents. Differentiation is aided by including ferric ammonium citrate in the final medium. Since all Listeria species hydrolyze esculin, the addition of ferric ions to the medium will detect the reaction. A blackening of the medium by cultures containing esculin-hydrolyzing bacteria is the result of the formation of 6,7-dihydroxycoumarin that reacts with the ferric ions.7 Selectivity is provided by the presence of lithium chloride, nalidixic acid and acriflavine in the formula. The high salt tolerance of Listeria is used as a means to inhibit growth of enterococci.
Note Fraser Broth Supplement (sold separately) is required when using this medium. This product can be found at the link below.