Coagulase

Coagulase is used by pathogenic bacteria to activate clotting mechanisms found in blood serum. The fibrin formed by this reaction coats bacteria and acts as a shield against immune reaction. The test is performed in media or on a slide. In either case, blood plasma collected from rabbits is used and mixed with anti clotting chemicals to stop it from forming clots on its own. The media is inoculated with the organism and examined after 4 hours (for a quick reaction) and after 24 hours (normal reaction). Visible fibers in the media or solidification of the media means a positive reaction. There is also a test performed by applying serum to a slide or comparable surface and then adding the organism to that. Visible clumps forming on the slide shows a coagulase positive reaction.