Thermo Scientific™ Baird-Parker Agar (ISO) Base (Dehydrated)

Baird Parker Agar contains carefully balanced selective inhibitory agents, glycine, lithium, and tellurite, to suppress the growth of most of the bacteria present in foods without inhibiting coagulase positive staphylococci. The presence of egg yolk emulsion and sodium pyruvate aid the recovery of damaged cells for presumptive identification of Staphylococcus aureus in food specimens.

Baird-Parker Agar base is widely recommended by national and international bodies for the isolation of Staphylococcus aureus¹.

• Easy interpretation of test results as Staphylococcus aureus forms gray/black shiny colonies with surrounding clear zones.
• Adheres to ISO 6888-1:1999 standards.

Baird-Parker² developed this agar medium from the tellurite-glycine formulation of Zebovitz et al ³. and improved its reliability in isolating coagulase-positive staphylococci from foods. Baird-Parker added egg yolk emulsion as a diagnostic agent and sodium pyruvate to protect damaged cells and aid their recovery⁴.

Egg yolk emulsion makes the medium cream/yellow and opaque. Coagulase-positive staphylococci reduce tellurite to form black/grey shiny colonies which, after 48 hours, produce clear zones around the colonies caused by the proteolysis of egg yolk. On further incubation, most strains of coagulase-positive staphylococci form opaque haloes around the colonies.

Some strains of Staphylococcus saprophyticus may also produce both clear zones and opaque haloes but can be distinguished by the longer incubation required⁵.

Colonies typical of Staphylococcus aureus , but without an egg yolk reaction, should also be tested for coagulase production⁶. Egg yolk reaction negative Staphylococcus aureus may occur in some food, especially cheese.

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