Violet Red Bile Agar (VRBA), a modification of MacConkey's original formulation is used for the enumeration of coliaerogenes bacterial group. VRBA is recommended by APHA. It is also recommended by ISO.Violet Red Bile HiCynthâ„¢ Agar is a modification wherein animal based peptones are replaced with chemically defined peptones to avoid BSE/TSE/GMO risks associated with animal peptones.