Half Fraser Standard broth is used for the enrichment of Listeria monocytogenes and other Listeria spp. in food products and enviromental samples. This broth can be used as primary enrichment broth following the ISO 11290-1 or as the single enrichment broth of many alternative methods for the detection of Listeria monocytogenes and other Listeria spp according to ISO Standard. This media doesn’t required any supplement anymore.
Principle
Half Fraser Standard broth contains a particular mix of nutrient to optimize the growth of Listeria spp.
strains including Listeria monocytogenes. Due to the combined action of lithium chloride, acriflavine, and
nalidixic acid, this broth inhibits non-Listeria flora. The balance between nutritivity and selectivity ensure
the good growth of Listeria monocytogenes and other Listeria spp. in all types of matrices.
Theoretical Composition
| Peptone | 5 g |
| Tryptone | 5 g |
| Yeast extract | 5 g |
| Meat extract | 5 g |
| Sodium chloride | 20 g |
| Disodium hydrogen phosphate dihydrate | 12 g |
| Potassium dihydrogen phosphate | 1.35 g |
| Esculin | 1 g |
| Lithium chloride | 3 g |
| Acriflavine hydrochloride | 12.5 mg |
| Nalidixic acid | 10 mg |
| Ferric ammonium citrate (III) | 500 mg |
| Distilled water | 1,000 ml |
| Final pH at 25 ⁰C = 7.2 ± 0.2 |
Reconstitution Ratio
57.9 g/L (500 g of powder makes 8.6 L of medium)
Storage
Store dehydrated medium at 15-25 ⁰C in carefully sealed bottles in a dry and dark place
References
– ISO 11290-1:2017
– ISO 11290-2:2017