M-Tetrathionate HiVeg™ Broth Base

Principle and Interpretation

M-Tetrathionate HiVeg Broth Base is prepared by using vegetable peptones which are free of BSE/TSE risks. This medium is the modification of M-Tetrathionate Broth Base prepared as per the formulation of Kabler and Clark (1) for selective enrichment of Salmonella using membrane filter technique. M-Tetrathionate HiVeg Borth Base is same as Tetrathionate Broth Base except calcium carbonate.

HiVeg peptone No. 3 provides nitrogenous nutrients, vitamins, amino acids and carbon for bacterial metabolism. Tetrathionate is formed in the medium by the iodide and iodine reaction. Along with sodium thiosulphate, tetrathionate inhibits the normal flora of intestine from the faecal organisms (2). Only those organisms which have the tetrathionate reductase enzyme can grow in this medium. Synthetic detergents inhibit many gram-negative organisms and coliforms.

Soak the absorbent pads in 5 - 6 cm petri plates with 2 ml of M-Tetrathionate HiVeg Broth Base and place membrane filter inoculum on them. Incubate at 35 - 37°C for 3 hours and then transfer inoculum membrane filter onto absorbent pads soaked with 2 ml M-Brilliant Green HiVeg Broth (MV1102). Incubate at 35-37°C for 15 - 21 hours. After M-BGB incubation add urease test reagent (Urease test reagent- Urea 20 gm, bromothymol blue 0.16 gm and phenol red 0.2 gm in 1000 ml distilled water) to pad and allow to set for 15-20 mins to permit reagent to diffuse throughout the medium for development of colour.