Overview:
Buffered Listeria Enrichment Broth is the internationally recognized selective enrichment broth for the detection of Listeria monocytogenes and other Listeria spp. from foods, dairy, meat, environmental samples, and clinical specimens. It is the mandatory primary enrichment step in ISO 11290-1:2017, FDA-BAM Chapter 10, and USDA-FSIS MLG 8. The formulation includes buffering agents to neutralize acidic foods and selective agents (acriflavine, nalidixic acid, cycloheximide) that are added after 4 h to allow resuscitation of injured cells.
Applications:
Official primary enrichment for Listeria in all major global methods
Detection of L. monocytogenes in dairy, meat, poultry, seafood, vegetables, ready-to-eat foods
Environmental monitoring in food-production facilities
Key Features:
High buffering capacity (prevents pH drop in acidic foods)
4-hour non-selective pre-enrichment ? maximum recovery of stressed cells
Selective supplements added after 4 h ? excellent selectivity without inhibiting injured Listeria
Composition (per liter � Base only):
Trypticase/Tryptone 17.0 g
Soy Peptone/Papaic Digest of Soybean Meal 3.0 g
Yeast Extract 6.0 g
NaCl 5.0 g
KH?PO? 1.35 g
Na?HPO? 9.6�12.0 g (buffer)
Sodium Pyruvate 1.1 g (protects injured cells)
Glucose 1.0�2.0 g
Final pH: 7.3 � 0.1 at 25�C
Selective Supplement (added after 4 h incubation):
Acriflavine HCl 10 mg
Nalidixic acid (sodium salt) 40 mg
Cycloheximide 50 mg
Preparation & Procedure (ISO/FDA):
Suspend 43.0�46.0 g base in 1 L purified water.
Autoclave at 121�C for 15 min.
Cool to room temperature.
Aseptically add 2250 mL sample homogenate (1:10 dilution).
Incubate at 30�C for 4 h (non-selective phase).
Add filter-sterilize and add selective supplement.
Continue incubation at 30�C for total 24 h and 48 h.
Subculture at 24 h and 48 h onto ALOA, Oxford, PALCAM, or chromogenic agars.
Storage:
Dehydrated base: cool, dry place below 30�C
Prepared base (without supplement): 2�8�C, use within 7 days
Complete broth with supplement: use same day
For food and environmental microbiology only.
Official reference: ISO 11290-1:2017, FDA-BAM Ch.10, USDA-FSIS MLG 8.12, Lovett et al. (1987).