Ethyl Violet Azide HiVeg™ Broth (E.V.A. HiVeg™ Broth)

Principle And Interpretation

Ethyl Violet Azide Broth is based on the formulation of Litsky et al (1) and the present medium is a modification of medium developed by Litsky et al (2) with reduced amount of dextrose and increased dye concentration, making the medium highly specific for Enterococci. The presence of Enterococci acts as a valuable index of faecal or sewage pollution in water (3). E.V.A. HiVeg™ Broth is used in conjunction with Azide Dextrose HiVeg™ Broth (MV345). Larkin et al (4) used Azide Dextrose Broth as a presumptive medium and E.V.A. Broth for the confirmation of the presence of Streptococci in frozen foods. They found that generally faecal Streptococci were recovered more consistently and in greater number than the coliforms and could be used in preference to coliforms as an indicator bacteria in frozen foods. Litsky et al (1) studied a variety of dyes and selective agents for Streptococci and developed a confirmatory medium using ethyl violet and sodium azide as selective agents. Combination of 0.0083gm% of ethyl violet dye and 0.04gm% of azide provided the best selective action favouring growth of Streptococci (1).

Ethyl Violet Azide HiVeg™ Broth (E.V.A. HiVeg™ Broth) is prepared by using vegetable peptones in place of animal based peptones which make the media free of BSE/TSE risks. EVA Broth contains HiVeg™ hydrolysate as source of carbon, nitrogen, vitamins and minerals. Dextrose is the fermentable carbohydrate. Sodium azide and ethyl violet inhibit gram-positive bacilli and gram-positive cocci other than Enterococci. Potassium dihydrogen phosphate and Dipotassium hydrogen phosphate buffer the medium. Sodium chloride provides osmotic balance.