Thermo Scientific™ Remel™ Demi-Fraser Broth Base

Description

• Selectively isolate and cultivate Listeria monocytogenes from food and environmental samples using Thermo Scientific™ Remel™ Demi-Fraser Broth Base (Dehydrated)
• Demi-Fraser Broth Base is a modification of Fraser Broth Base developed by Fraser and Sperber and used for rapid detection of Listeria in food and environmental samples 1
• The nalidixic acid and acriflavine concentrations in this medium have been reduced to 10 mg/L and 12.5 mg/L respectively in accordance with L'association française de normalisation (AFNOR) guidelines 2
• Listeria monocytogenes is a common contaminant in raw milk, meats, vegetables, seafood and in the food processing environment 3,4
• Isolation of Listeria species presents a grave challenge because it can grow in pH environments ranging from 5.0 – 9.6 and even under refrigeration
• Successful recovery of Listeria from food and environmental sources requires a medium which can promote the growth of potentially injured cells while inhibiting the growth of non- Listeria background organisms
• The isolation of low numbers of L
• monocytogenes can be improved by enrichment procedures using a broth medium
• Selective Medium : Contains lithium chloride, nalidixic acid and acriflavine Lithium chloride – inhibits most enterococci which can also hydrolyse esculin
• Nalidixic acid – blocks DNA replication of susceptible bacteria
• Acriflavine – inhibits growth of secondary gram-positive microflora
• Easy-to-interpret : Color change on visual inspection - blackening of the solution Conforms to L’association française de normalisation (AFNOR) guidelines Demi-Fraser Broth Base contains casein peptone, meat peptone and beef extract that provide essential amino acids, peptides, and nitrogen necessary for growth of Listeria species
• Yeast extract supplies B-complex vitamins, sodium chloride provides essential electrolytes and maintains osmotic equilibrium
• Disodium phosphate and monosodium phosphate act as buffers and maintain the pH
• Lithium chloride, nalidixic acid, and acriflavine act as selective agents
• 0.1 mL of Fraser Broth Additive (REF R450361) is added to every 10 mL of prepared Demi-Fraser Broth Base immediately before use
• This supplies the ferric ions in form of ferric ammonium citrate
• All Listeria species hydrolyse esculin to form 6,7-dihydroxycoumarin, which combines with ferric ions to blacken the medium
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• Remel™ and Oxoid™ products are now part of the Thermo Scientific brand.