Half Fraser (Demi-Fraser) Broth (ISO), 500g

Half Fraser (Demi-Fraser) Broth is used with ferric ammonium citrate for the selective enrichment of Listeria species and is not intended for use in the diagnosis of disease or other conditions in humans. Primary enrichment broth for the isolation of Listeria spp. formulated according to ISO 11290. The selective components acriflavine and nalidixic acid are blended into the base powder and the ferric ammonium citrate is added to the tempered broth after sterilization. Half Fraser (Demi-Fraser) Broth, NCM0001 was developed to give improved results for the isolation of Listeria spp. with both traditional and ELISA methods. As with the sister product, Fraser Broth, NCM0050 the selective components acriflavine and nalidixic acid are blended into the base powder and the Ferric Ammonium Citrate is added to the tempered broth after autoclaving. This format has been shown to give improved selectivity with pure cultures and food samples. Furthermore, more stable ELISA results are seen, resulting in fewer false positive results when the ferric ammonium citrate is omitted from the complete media. Developed as a modification of UVM medium (NCM0012) and made according to ISO 11290, Fraser Broth is a secondary enrichment broth for the isolation of Listeria spp. and is similar to Palcam Broth (NCM0049) in that it contains esculin to indicate the presence of a potential Listeria isolate. It also contains lithium chloride in an attempt to suppress the growth of Enterococci in the medium (as does Palcam). Listeria spp. hydrolyze the esculin to form esculetin, which reacts with the ferric ammonium citrate in resulting in a black precipitate and a visible positive reaction. However, Enterococci can also perform this reaction so further plating is required onto an isolation medium such as Harlequin® Listeria Chromogenic Agar (NCM1004).

Typical Formulation

Formula Litre
Enzymatic Digest of Animal Tissues 5.0 g/L
Enzymatic Digest of Casein 5.0 g/L
Meat Extract 5.0 g/L
Yeast Extract 5.0 g/L
Esculin 1.0 g/L
Disodium Hydrogen Phosphate 9.6 g/L*
Potassium Dihydrogen Phosphate 1.35 g/L
Sodium Chloride 20.0 g/L
Lithium Chloride 3.0 g/L
Acriflavine 0.0125 g/L
Nalidixic Acid 0.01 g/L
*Equivalent to Disodium Hydrogen Phosphate Dihydrate 12.0 g/L

Preparation

Dissolve 55 grams of the medium in one liter of purified water.
Mix thoroughly.
Autoclave at 121°C for 15 minutes
Cool to 45-50°C.
Aseptically add 2 vials of NCM4009-0.5* Ferric Ammonium Citrate Supplement.

*Larger vials may be available. Please see appropriate supplement data sheet for availability and preparation instructions.