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Buffered Listeria Enrichment Broth Base (BLEB)

Buffered Listeria Enrichment Broth Base (BLEB) is used with supplements for selective enrichment of Listeria spp. in foods in a laboratory setting. Buffered Listeria Enrichment Broth Base (BLEB) is not intended for use in the diagnosis of disease or other conditions in humans.

Listeria monocytogenes, described first in 1926 by Murray, Webb, and Swann, is an extensive problem in food industries. Evidence from outbreaks of listeriosis has indicated that the principle route of transmission is via consumption of foodstuffs contaminated with Listeria monocytogenes. Implicated vehicles of transmission include turkey, frankfurters, coleslaw, pasteurized milk, Mexican style cheese, and pate.

Buffered Listeria Enrichment Broth, a modification of the formula by Lovett et al. was developed after research concluded that enrichment properties can be improved by increasing the buffering capacity of the medium with the addition of disodium phosphate. BLEB Base is based upon the FDA/BAM recommendations where the medium is supplemented with selective agents after an initial 4 hour, non-selective, pre-enrichment.

 

Formula Liter
Enzymatic Digest of Casein 17 g
Enzymatic Digest of Soybean Meal 3 g
Yeast Extract 6 g
Dextrose 2.5 g
Sodium Chloride 5 g
Monpotassium Phosphate 1.35 g
Dipotassium Phosphate 2.5 g
Disodium Phosphate 9.6 g

Final pH: 7.3 ± 0.2 at 25°C
Formula may be adjusted and/or supplemented as required to meet performance specifications.

BLEB Supplement

Acriflavine HCl, 4.5 mg
Nalidixic Acid, 18 mg
Cycloheximide, 22.5 mg

Directions

  1. Dissolve 47 g of the medium in 1000 mL of purified water.
  2. Mix thoroughly.
  3. Autoclave at 121°C for 15 minutes.
  4. Aseptically add 11.1 mL of a 10% filter sterilized solution of sodium pyruvate.
  5. After four hours of incubation at 30 ± 2°C, aseptically add 2.5 mL Buffered Listeria Enrichment Supplement (FDA) (#7980) to 225 mL of Buffered Listeria Enrichment Broth Base containing 25 grams of the sample. OR, aseptically add 0.455 mL of a 0.5% aqueous solution of acriflavine, 1.8 mL of a 0.5% aqueous solution of nalidixic acid, and 1.15 mL of a 1.0% solution of cycloheximide in 40% ethanol to 225 mL of medium containing 25 g or 25 mL of food to be tested.

Order Details

Product # Product Description
7675A Buffered Listeria Enrichment Broth Base, 500 g
7675T Buffered Listeria Enrichment Broth Base, 5 kg