The 3M Petrifilm Staph Express Count system consists of a Petrifilm Staph Express Count Plate and a Petrifilm Staph Express Count Disk, which are packaged and sold separately. The Petrifilm Staph Express Plate is a sample-ready-culture-medium system that contains a chromogenic, modified Baird-Parker medium and a cold-water-soluble gelling agent.
The test requires only one incubation temperature and is equivalent to the BAM three-plate Baird-Parker agar and single tube-coagulase method. A chromogenic indicator in the Petrifilm Staph Express Count Plate identifies Staphylococcus aureus by producing red-violet colonies. When only red-violet colonies are seen, count the colonies and report as S. aureus; the test is complete. If you encounter background flora in your Staph testing, the Petrifilm Staph Express Disk may be used to identify S. aureus from all other suspect colonies. The Petrifilm Staph Express Disk contains toluidine blue-O to facilitate the visualization of deoxyribonuclease (DNase) reactions. The Petrifilm Staph Express Disk should be used whenever colonies other than red-violet are present on the plate.