Lysine Arginine Iron HiVeg™ Agar

Principle and Interpretation

Lysine Arginine Iron HiVeg Agar is prepared by using HiVeg peptone in place of Peptic digest of animal tissue which makes the medium free of BSE/TSE risks. Lysine Arginine Iron HiVeg Agar is the modification of Lysine Arginine Iron Agar which is formulated as recommended by APHA (1) for isolation and identification of Yersinia species from milk and milk products. Some Yersinia species have been implicated in human disease with a variety of clinical syndromes (2).

HiVeg peptone and yeast extract provide the necessary nitrogenous nutrients and vitamin B complex to the organisms. Ferric ammonium citrate and sodium thiosulphate are the indicators for hydrogen sulphide (H₂S) production. This medium contains two amino acids L-Arginine and L-Lysine. The organisms which do not decarboxylate L-Lysine but ferment glucose, gives an alkaline slant and an acid butt (yellow colour, as bromo cresol purple is the pH indicator).

The sample suspected of Yersinia can be inoculated on MacConkey HiVeg Agar (MV081) rather than directly streaking on Lysine Arginine Iron HiVeg Agar. Inoculate the suspected Yersinia colony from MacConkey HiVeg Agar (MV081) on Lysine Arginine Iron HiVeg Agar and incubate at 22-26°C upto 48 hours. Organisms which give a alkaline slant, acidic butt, no gas and no hydrogen sulphide (H2S) production on Lysine Arginine Iron HiVeg Agar and urease-positive are considered to be presumptive Yersinia (1).