STAPHYLOCOCCUS AGAR
Staphylococcus Agar is a selective medium for the isolation and differentiation of pathogenic Staphylococci. Enzymatic Digest of Casein and Yeast Extract provide amino acids, proteins, carbohydrates, vitamins, and electrolytes. D-Mannitol is the main carbohydrate source, while Lactose is the supplementary one. Dipotassium Phosphate acts as a pH buffer. Sodium Chloride provides electrolytes, maintains osmotic equilibrium, and makes the medium selective for Gram-positive bacteria. Gelatin is included to test liquefaction. Pathogenic Staphylococci grow well on this medium and form golden yellow colonies. Mannitol fermentation is detected by adding a few drops of Bromothymol Blue and looking for a yellow halo on the areas where colonies have been removed. Gelatin liquefaction can be observed as clear zones after flooding the plates with an aqueous solution of Ammonium Sulfate and incubating 10 min at 37 ºC. Agar is the gelifying agent.