Baird-Parker Agar

Baird-Parker Agar is a selective medium used for the isolation and enumeration of Staphylococcus aureus in food and dairy products. It was developed to improve the recovery of damaged S. aureus from food samples and is formulated in compliance with ISO 6888-1:1999+A1:2003, ISO 6888-2:2003+A1:2003, and ISO 6888-3:2003.

Selectivity is achieved through potassium tellurite and lithium chloride, which suppress competing flora. Tellurite reduction produces the typical black, shiny colonies of S. aureus. Glycine and sodium pyruvate further support staphylococcal growth, with pyruvate also neutralizing toxic peroxides.

When supplemented with Egg Yolk Tellurite, presumptive S. aureus colonies appear black with lecithinase activity (opaque zones) and lipase activity (zones of clearing around opaque zones). Colonies require confirmation using RPF coagulase or latex agglutination.

Rabbit plasma fibrinogen (RPF) is an alternative supplement that enables direct detection of coagulase-positive S. aureus, producing black colonies surrounded by a precipitation zone. This approach is considered the reference standard and reduces the need for further confirmatory testing.

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