Plasma coagulase is an enzyme produced by most pathogenic bacteria that infect the human body and can cause coagulation of plasma containing anticoagulants such as heparin in the human body, and only the more pathogenic bacteria are able to produce plasma coagulase. Therefore, it is an indicator for the differential diagnosis of pathogenicity of bacteria. Plasma coagulase, which is contained in most pathogenic bacteria, causes soluble fibrinogen in the body to become insoluble fibrin and form clots, which are wrapped around the surface of the bacteria and protected from bactericidal substances in the blood, and also resist phagocytosis by macrophages. Therefore, the plasma coagulase test is an important indicator to identify the pathogenicity of pathogenic bacteria. A positive plasma coagulase test indicates that the infected bacteria are highly pathogenic.