BLE Broth Base (Buffered Listeria Enrichment Broth Base)

Principle and Interpretation

BLE HiVeg Broth Base (Buffered Listeria Enrichment HiVeg Broth Base) is the modification of conventional formula formulated as per APHA (1) for the selective enrichment of Listeria monocytogenes from foods. The original broth has been modified by buffering the medium, thereby making it possible for the medium to be used successfully in conjunction with DNA probe and other methods that are more sensitive than conventional cultural procedures. HiVeg hydrolysate and papaic digest of soyabean meal provide amino acids and other complex nitrogenous substances. Dextrose is the energy source. Phosphates act as buffering system to control pH. Yeast extract is the rich source of vitamin B complex.

According to FDA's enrichment procedure (4) for isolation of Listeria monocytogenes from dairy products, the sample to be tested is inoculated in enrichment broth and incubated at 30°C for 4 hours without the selective supplement. After 4 hours the selective supplement is added and further kept for incubation for additional 44 hours at 30°C. At 24hrs and 48hrs the enriched culture is streaked on Oxford Listeria HiVeg Medium Base (MV1145) and LPM HiVeg Agar (MV1228) / Listeria identification HiVeg Agar Base, PALCAM (MV1064) and incubated at 35°C for 24-48 hours. Presumptive Listeria colonies are selected and colonies are further purified on Tryptone Soya Yeast Extract HiVeg Agar (MV1214). Purified isolates are then subjected to a variety of biochemical tests to confirm the presence of L.monocytogenes.