Recovery of coliforms in milk and water. Description: Deoxycholate Lactose Agar was formulated by Leifson for the detection of coliforms in water, dairy products and other food materials. USBio recommends Violet Red Bile Agar as the medium of choice for isolating coliforms from food products. Growth of coliforms which ferment lactose produce red colonies surrounded by a zone of red precipitate. The fermentation of lactose produces acid products which lowers the pH of the medium and the neutral red dye in the medium turns bright red. Sodium citrate and sodium deoxycholate are added to inhibit the growth of Gram positive bacteria.