Mitis Salivarius Agar is a medium used with supplements for the selective isolation of Streptococcus viridans, such as Streptococcus mitis and Streptococcus salivarius, and Enterococcus faecalis, from specimens containing mixed microbial flora. Streptococcus mitis, Streptococcus salivarius and Enterococcus spp. are part of the normal human flora. S. mitis and S. salivarius are known as streptococci viridans. These organisms play a role in cariogenesis and infectious endocarditis and are responsible for an increasing number of bacteremias. Enterococci cause urinary tract infections, wound infections, bacteremia, and can colonize the skin and mucous membranes. Enzymatic digestion of casein and enzymatic digestion of animal tissues provide amino acids, nitrogen, carbon, minerals, vitamins and other nutrients for the growth of organisms. Sucrose and dextrose are the fermentable carbohydrates. Dipotassium phosphate is the buffering agent. Trypan blue is absorbed by the colonies, giving them a blue color. Crystalline violet inhibits most Gram-negative bacilli and Gram-positive bacteria, with the exception of streptococci. It is also possible to add sodium azide to inhibit the growth of Gram-negative bacteria such as Proteus. Agar is the solidifying agent.