Mitis Salivarius Agar is a solid medium used for the selective isolation ofStreptococcusmitis,Streptococcussalivarius, andEnterococcifrom heavily contaminated specimens. Enzymatic Digest of Casein and Peptic Digest of Animal Tissue provide nitrogenous sources. Dextrose and Sucrose are the fermentable carbohydrates.S.salivariusmetabolizes Sucrose and forms big colonies with a “gum-drop” appearance, whileS.mitisandEnterococcido not ferment this sugar and form smaller colonies. Trypan Blue and Crystal Violet are selective agents that inhibit the growth of most Gram-negative and Gram-positive microorganisms. The former is absorbed byStreptococci, resulting in the formation of blue colonies. Dipotassium Phosphate serves as pH buffer. Agar is the gelifying agent.