EMB AGAR (VEG.)

Description

These media are prepared by using Veg peptone in place of peptic digest of animal tissue which is free of BSE/TSE risks. EMB Veg Media are the modification of Eosin Methylene Blue (EMB) Media which are originally devised by Holt-Harris and Teague and further modified by Levine. Methylene blue and Eosin-Y inhibit gram positive bacteria to a limited degree. These dyes serve as differential indicators in response to the fermentation of carbohydrates. The ratio of eosin and methylene blue is adjusted approximately to 6:1. Sucrose is added to the medium as an alternative carbohydrate source for typically lactose fermenting, gram-negative bacilli, which on occasion do not ferment lactose or do so slowly. The coliforms produce purplish black colonies due to taking up of methylene blue eosin dye complex, when the pH drops. The dye complex is absorbed into the colony. Non-fermenters probably raise the pH of surrounding medium by oxidative deamination of protein, which solubilizes the methylene blue-eosin complex resulting in colourless colonies.