KM0046 – Fraser Half-Broth Strength

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KM0046 – Fraser Half-Broth Strength

Half-Fraser broth is a selective enrichment broth for the identification and isolation of Listeria spp, primarily from food and environmental samples. The antibiotics, nalidixic acid and acriflavine, are already included in the formulation so only ferric ammonium citrate (LS5004) need be added to make the complete Half-Fraser broth.
The peptones provide carbon, nitrogen and vitamins, sodium chloride provides osmotic balance and the phosphate buffer system maintains pH. Lithium chloride inhibits enterococci and the antibiotics make the medium highly selective. Listeria spp hydrolyse aesculin to aesculetin which forms a confirmatory dark brown or black complex with Fe3+ ions.

Additional Information

Shelf Life (days)

Storage Temp (°C)

Dehydrated Medium Appearance

Prepared Medium Appearance

Dehydrated Medium Colour

Prepared Medium Colour

Dehydrated PH

Prepared PH

Product Description

OrganismRef. No.Result
Listeria monocytogenesNCTC 11994Turbid growth
Listeria innocuaNCTC 11288Turbid growth
Escherichia coliNCTC 12241No growth
Enterococcus faecalisNCTC 12697No growth

Formula*

FORMULA*g/L
Enzymatic digest of animal tissue5
Enzymatic digest of casein5
Meat extract5
Yeast extract5
Sodium chloride20
Di-sodium hydrogen phosphate9.6
Potassium dihydrogen phosphate1.35
Aesculin1
Lithium chloride3
Nalidixic acid0.01
Acriflavin0.0125
Total55

Preparation

Suspend 55.0 g of the medium in one litre of deionised / purified water. Allow the medium to soak whilst mixing for 10 minutes.

Sterilise at 121°C for 15 minutes with frequent stirring to completely dissolve the medium. Cool to 42-46°C. To make Half-Fraser broth add 2 vials of LS5004 or to make Fraser broth add 2 vials of LS5003. Mix well and dispense into appropriate sterile containers