Baird-Parker Agar Base

Test

• Dry the surface of the culture plate before inoculation as quickly as possible.
• Soak the desired food sample in water or Buffered Peptone Water culture medium and prepare a dilution according to the relevant protocol.
• Add 0.1 to 0.5 milliliters of the sample onto the agar plate and spread it completely on the surface of the plate.
• Incubate the inoculated plates at 35 ± 2°C for 24-48 hours.

Results and Interpretation

• Typical colonies of Staphylococcus aureus (which are coagulase positive) on Baird-Parker Agar culture medium are black in color, convex, and have a clear halo around them. Staphylococcus strains that are coagulase-negative usually do not grow on this medium, and if they do, they are usually lacking the clear halo around them.
• Other bacteria usually do not grow in this medium, and if they grow, they form white or brown colonies that do not have a clear halo around them.

Note:

• All suspected colonies of Staphylococcus aureus, despite negative reactions, should be isolated from the culture medium and subjected to further confirmatory tests.
• Some non-target bacteria colonies that are present in the sample and grow near coagulase-positive colonies may partially or completely digest the coagulase halo reaction.
• Baird-Parker Agar medium is highly toxic due to the presence of lithium chloride in its composition. Avoid contact of the medium with skin, eyes, and inhalation of the medium powder.

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Quality Control

• Dehydrated Appearance: Light tan, free-flowing, homogeneous.
• Prepared Appearance: Yellow, opaque.
• Cultural response was observed after adding Egg Yolk Tellurite Emulsion, for 24-48 hours of incubation at 35 ± 2˚C.