MacConkey Agar w/o CV,NaCl, w/ Sodium Taurocholate

MacConkey Agar is the earliest selective and differential medium for cultivation of enteric microorganisms from a variety of clinical and non clinical specimens.

Original medium contains protein, bile salts, sodium chloride and two dyes. The selective action of this medium is attributed to bile salts, which are inhibitory to most species of gram-positive bacteria. MacConkey Agar w/o CV, NaCl and w/0.5% Sodium taurocholate is a modification of the original formulation with the exclusion of crystal violet and inclusion of sodium taurocholate instead of bile salts. Gram-negative bacteria usually grow well on the medium and are differentiated by their ability to ferment lactose. Lactose fermenting strains grow as red or pink and may be surrounded by a zone of acid precipitated bile. The red colour is due to production of acid from lactose, absorption of neutral red and a subsequent colour change of the dye when the pH of medium falls below 6.8. Lactose non fermenting strains, such as Shigella and Salmonella are colourless and transparent and typically do not alter appearance of the medium.