Thermo Scientific™ Oxoid™ Baird-Parker Agar

Description

Isolate and enumerate Staphylococcus aureus with ready-to-use, highly selective and sensitive Thermo Scientific™ Baird-Parker Agar. The medium aids the recovery of damaged cells for presumptive identification of Staphylococcus aureus in food specimens.

Baird-Parker Agar medium is widely recommended by national and international bodies (ISO 6888-1) for the isolation of Staphylococcus aureus¹.

• Staphylococcus aureus forms distinctive grey-black shiny colonies with surrounding clear zones
• Ready-to-use convenience of prepared media
• The formulation conforms to ISO 6888-1

Baird-Parker² developed this medium from the tellurite-glycine formulation of Zebovitz et al.³ and improved its reliability in isolating Staphylococcus aureus from foods. The addition of sodium pyruvate protects damaged cells and aids their recovery⁴ and egg yolk emulsion acts as a diagnostic agent.

The selective agents, glycine, lithium and tellurite, have been carefully balanced to suppress the growth of most bacteria present in foods, without inhibiting Staphylococcus aureus.

Egg yolk emulsion makes the medium yellow and opaque. Staphylococcus aureus reduces tellurite to form grey-black shiny colonies and then produces clear zones around the colonies by proteolytic action. On further incubation, most strains of Staphylococcus aureus 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 time required⁵.

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