Originally intended for use in food laboratories as an aid to recovering Staphylococcus aureus, Baird Parker has become equally popular in clinical laboratories. The medium is made highly selective by the inclusion of Lithium Chloride and Potassium Tellurite. The tellurite inhibits most coliforms and is reduced by staphylococci to telluride giving rise to black colonies. Glycine and Sodium Pyruvate are included as growth enhancers while the pyruvate also acts as a neutraliser of toxic peroxides.