Macconkey Agar is used for the isolation, enumeration and enrichment of Enterobacteriaceae. MacCONKEY AGAR (as per USP/EP/BP/JP) is used for the isolation, enumeration and enrichment of Enterobacteriaceae. The medium for bacteria designed to selectively isolate Gram-negative and enteric (normally found in the intestinal tract) bacilli and differentiate them based on lactose fermentation. Subsequently, MacConkey Agar was recommended for use in microbiological examination of foodstuffs and for direct plating / inoculation of water samples for coliform counts. These media are also accepted by the Standard Methods for the Examination of Milk and Dairy Products and pharmaceutical preparations
Peptic digest of animal tissue supply the necessary amino acids and polypeptides, while infusions supply vitamins, coenzymes and minerals as well as additional nitrogen compounds. Lactose has been used at a concentration of 1% (wt/vol.) to detect acidification against the alkalinization caused by peptone catabolism. pH indicator is added to differential media to detect changes in hydrogen ion concentration during the growth of an organism as lactose fermentation. Neutral red will change color as the pH changes. MacConkey Agar is a solidifying agent. Bile salt is a selective agent. Lactose fermenting strains grow as red or pink whereas non lactose fermenters grow as colourless.