You can use Listeria Enrichment Medium Base (UVM Medium) Listeria Enrichment Medium Base (UVM Medium) is used for selective isolation and cultivation of Listeria monocytogenes from clinical specimens. Composition Ingredients g / L.

Casein enzymic hydrolysate 5.g Proteose peptone 5.g Beef extract 5.g Yeast extract 5.g Sodium chloride 20.gMonopotassium dihydrogen phosphate 1.35g Disodium hydrogen phosphate 12g Esculin 1.gFinal pH (at 25°C) 7.4

is BPW-iso or BHI Broth with some modifications recommended to be used as primary enrichment broth?

Just see if this reference would do any good:

Int J Food Microbiol. 1995 Jun;26(1):1-13.

I advise Fraser...If this food material is high contamined; I advise to use UVM medium. Add this food material to to UVM medium and incube 30 min. After add supplement to this broth.