Fraser Broth Base, Modified (Half Fraser Broth) is recommended for the selective enrichment of Listeria species from food. Listeria species hydrolyze esculin to glucose and esculetin. The latter combines with ferric ions of ferric ammonium citrate, resulting in the formation of 6-7 dihydroxycoumarin, a black brown complex. Ferric ammonium citrate also enhances the growth of L. monocytogenes. The high salt tolerance (of sodium chloride) of Listeria is used as means to inhibit the growth of Enterococci.
- Appearance: Cream to yellow homogeneous free flowing powder
- Color and Clarity of prepared medium: Fluorescent yellow colored clear solution
- Reaction of 5.5% w/v aqueous solution at 25°C. pH : 7.2±0.2
- Cultural characteristics observed on addition of FD141 after an incubation at 35 - 37°C for 24-48 hours