Buffered Listeria Enrichment Broth Base acc. to FDA/BAM 1995

Buffered Listeria Enrichment Broth Base (BLEB)

Cat. No. 1.09628.0500/5007
(500 g, 5kg)

For the selective enrichment of Listeria spp.

This medium complies with the modifications made by FDA/BAM (1995).

Mode of Action	Quality Control
Typical Composition (g/liter)	Additives/Reagents
Preparation	Literature
Experimental Procedure and Evaluation

Mode of Action
The enrichment broth is a modification of the formulation of Tryptic Soy Broth (CASO) with the addition of 6 g/l yeast extract and by increasing its buffering strength. Dextrose is the carbohydrate source. Sodium chloride maintains the osmotic balance of the medium. Phosphate acts as a buffer. Sodium pyruvate mediates the recovery of sublethally damaged Listeria spp.
The addition of acriflavine, cycloheximide and nalidixic acid inhibits the growth of the accompanying flora.

Typical Composition (g/liter)
Tryptic Soy Broth 30 g; yeast extract 6.0; di-sodium hydrogen phosphate 9.6; potassium dihydrogen phosphate 1.35; sodium pyruvate 1.1.

Preparation
Suspend 24 g in 500 ml of purified water, dissolve and dispense 225 ml aliquots. Autoclave (15 min at 121°C).
pH: 7.3 ± 0.2 at 25°C.
The prepared broth is clear.

Experimental Procedure and Evaluation
Inoculate Listeria Enrichment broth (usually add 25 g of a representative sample to 225 ml broth) and homogenize.
For the recovery of sublethally injured Listeria spp. incubate at 30°C for 4 h.

Thereafter, the appropriate aliquot of supplement (0.5 ml from a vial of Listeria enrichment supplement reconstituted by adding of 1 ml sterile purified water) is added. The sample is thoroughly mixed and incubation is continued for another 44 h at 30°C.
After 24 and 48 h of incubation streak a loopful of incubated broth onto both Oxford and Palcam agar (alternatively LPM agar). Incubate Oxford and Palcam agar at 35°C, LPM agar
at 30°C for 24-48 h.

Quality control

Test strains	Growth
Listeria monocytogenes ATCC 19114	good
Listeria monocytogenes ATCC 19116	good
Listeria innocua ATCC 33090	good
Staphylococcus aureus ATCC 25923	good
Enterococccus faecalis ATC 19433	good
Escherichia coli ATCC 25922	none

Additives

EMD Cat. No.	Product	Pack Size
1.07004.0500	OXFORD Listeria Selective Agar (Base)	500 g
1.07006.0001	Oxford Listeria Selective Supplement	1 x 13 vials
1.09628.0500	Buffered Listeria Enrichment Broth (Base) acc. to FDA/BAM 1995	500 g
1.11755.0500	PALCAM Listeria Selective Agar (Base)	500 g
1.11781.0001	Listeria Selective Enrichment Supplement acc. to FDA-BAM 1995/IDF-FIL	16 vials
1.12122.0001	PALCAM Listeria Selective Supplement acc. to VAN NETTEN et al.	1 x 16 vials

Literature

LOVETT, J., FRANCES, D.W., a. HUNT, J.M.: Listeria in raw milk, detection, incidence and pathogenecity. - Journal of Food Protection, 50; 188-192 (1987).
International Diary Federation: Milk and milk products-detection of Listeria monocytogenes. - IDF Provesional International Standard No. 143 International Diary Federation, Brussels (1990).
HITCHINS, A.D.: Listeria monocytogenes - In FDA-Bacteriological Analytical Manual 8^th EDITION, AOAC International Arlington V.A. (1995).
SWAMINATHAN, B., ROCOURT, J., a. BILLE, J.: Listeria - In MURRAY, P.R., BARRON, E.J., PFALLER, M.A., TANOVER, F.C. a. YOLKEN, R.H. (Eds.) - Manual of Clinical microbiology, 6^th ed. American Society of Microbiology, Washington D.C., 342-343 (1995).
FLOWERS, R.S., ANDREWS, W., DONNELLY, C.W., a. KOENING, E.: Pathogens in milk and milk products. - In MARSHAL, R.T. (ed.) Standard methods for the examination of dairy products, 16^th ed. American Public Health Association, Washington D.C. (1993).