Like the mannitol salts agar, the coagulase test is another method for differienting between pathogenic and non-pathogenic strains of Staphylococcus. Bacteria that produce coagulase use it as a defense mechanism by clotting the areas of plasma around them, thereby enabling themselves to resist phagocytosis by the host's immune system. The sample in question is usually inoculated onto 0.5 ml of rabbit plasma and incubated at 37 degrees celsius for one to four hours. A positive test is denoted by a clot formation in the test tube after the allotted time.
