Lysine Iron Cystine HiVeg™ Broth Base

Principle and Interpretation

Lysine Iron Cystine HiVeg Broth Base is prepared by using HiVeg hydrolysate in place of Casein enzymic hydrolysate which makes the medium free of BSE/TSE risks.

Lysine Iron Cystine HiVeg Broth Base is a modification of the formula of Hoben, Aston and Peterson (1). They described the usefulness of this medium for detecting Salmonellae in food samples in three days, thus reducing the holding time for foods and food ingredients.

HiVeg hydrolysate and L-Cystine provide carbonaceous and nitrogenous compounds. Yeast extract supplies Vitamin B complex. Dextrose, mannitol and salicin are the fermentable carbohydrates. Ferric ammonium citrate and sodium thiosulphate are the indicators of hydrogen sulphide formation. Lysine is the substrate which is either decarboxylated or deaminated.

25 g of the test sample is added to Lactose HiVeg Broth (MV026) and blended and incubated for 24 hours at 35 ± 2°C and 1 ml of this culture is added to 10 ml of Tetrathionate HiVeg Broth (MV032) and incubated at 35 ± 2°C for 24 hours. From this secondary culture, 1 ml is added to 10 ml Lysine Iron Cystine HiVeg Broth Base with Novobiocin and incubated at 35 ± 2°C for 24 hours. To eliminate the possibility of non H₂S (hydrogen sulphide) producing Salmonellae, incubate for an additional 16 - 24 hours. 0.1 ml. bromo thymol blue solution (0.3%) in 0.1 N NaOH and 50% ethanol is added to each tube. If the colour changes from yellow to dark green or blue, it indicates an alkaline reaction and the presence of Salmonella species.