This medium is cited as Agar medium O in British Pharmacopoeia, 2009 (1) recommended for isolation and enumeration of coagulase positive S. aureus. This medium was developed by Baird-Parker (2,3) from the Tellurite-glycine formulation of Zebovitz et.al.(4) for isolation of Staphylococcus aureus from foods. Staphylococcus species are common contaminants in food, dairy, pharmaceutical and cosmetics related products (9). This medium is recommended for sterility checking of materials to detect Staphylococcus aureus. Baird Parker medium was reported to be the best medium for selective detection of coagulase positive and entero-toxigenic Staphylococcus (5). This medium was found to be less inhibitory to Staphylococcus aureus than other media, at the same time being more selective (6,7). Subsequently it was officially adapted by the AOAC and British Pharmacopoeia (1,8).
Beef extract, yeast extract and pancreatic digest of casein provide essential mineral, vitamin and other growth requirements. Sodium pyruvate protects injured cells and helps recovery. Lithium chloride and potassium tellurite inhibit most of contaminating microflora except Staphylococcus aureus. Glycine, pyruvate enhances growth of Staphylococcus. With the addition of egg yolk the medium becomes yellow and opaque. Glycine neutralizes aldehyde, while egg yolk neutralizes phenolic compounds, if any, in the test samples.
Proteolytic bacteria produce a clear zone around colony in egg yolk containing media also known as Lecithinase reaction. A clear zone and grey-black colonies on this medium are diagnostic for coagulase positive Staphylococci. Upon further incubation, an opaque zone is developed around colonies, which can be due to lipolytic activity. Identity of Staphylococcus aureus isolated on Baird-Parker Agar must be confirmed with a coagulase reaction and deoxyribonuclease test. The sterility of product is confirmed by absence of growth of Staphylococcus aureus on this medium.
Storage and Shelf-life:
Store below 30°C in tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label.
References:
1. British Pharmacopoeia, 2009, The Stationery office British Pharmacopoeia.
2. Baird-Parker,A.C. 1962, J.Appl. Bact.,25: 12.
3. Baird-Parker,A.C. and Davenport,E., 1965,J.Appl.Bact.,28: 390.
4. Zebovitz, E., Evans J.B. & Niven C.F., (1955), J. Bact; 70:686.
5. Niskanean A and Aalto M, App. Env. Microbiol., 1978, 35:1233
6. Tardio and Baer, 1971, J.Assoc.Off. Anal. Chem., 54:728.
7. Baer, 1971, J.Assoc. Off. Anal. Chem., 54:732.
8. J. Assoc. off. Anal. Chem, 1971, 54:401.
9. FDA Bacteriological Analytical Manual, 2005, 18th ed., AOAC, Washington, DC.