Mode of Action
FRASER Listeria Supplement constits of 8 vials with ammonium iron(III) citrate and 8 vials with a selective supplement. The ammonium iron(III) citrate promotes the growth of the Listeria and, together wth esculin, permits the b-D-glucosidase detection in Listeria.
The selective supplement is a mixture of acriflavine and nalidixic acid in a lyophilised form. It largely inhibits the growth of accompanying bacteria by a selective enrichment of Listeria.
Composition (per vial)
Ammonium iron(III) citrate Supplement:
Ammonium iron(III) citrate 500 mg
Acriflavine 12.5 mg; nalidixic acid 10 mg.
The content is dissolved in each original vial by adding sterile distilled water (about 1 ml).
To prepare half-concentrated FRASER broth, the contents of 1vial of ammonium iron(III) citrate and 1 vial of selective supplement are evenly mixed into 1 litre of sterile FRASER broth base after it has cooled to about 45-50 °C.
FRASER broth is made by adding a further bottle of selective supplement to the half-concentrated FRASER broth.