Vogel-Johnson Agar is a selective and differential medium used for the early detection of Staphylococcus aureus through the identification of coagulaseous and mannitol fermentable strains. The medium is excellent for the detection of staphylococcus carriers as well as for health studies. S. aureus reduces potassium tellurite to metallic tellurium and leads to the growth of black colonies. The fermentation of mannitol is indicated by the yellow areas around the black colonies and changes the red color of the medium to yellow. Tryptone provides nitrogen, vitamins, minerals and essential amino acids for growth. Yeast extract is a source of vitamins, especially of the B group. Mannitol is the fermentable carbohydrate that provides carbohydrate and energy; potassium tellurite, lithium chloride and high concentration of glycine inhibit most microorganisms other than staphylococci. Phenol red is the indicator of pH. Dipotassium phosphate is a buffer. Bacteriological agar is the solidifying agent.