Coagulase
（重定向自Coagulase test）
![(TEM cryomicroscopy technique) - S. aureus forms a fibrin capsule that protects it from the immune system of cattle](/Images/godic/202501/05/Staphylococcus_aureus,_50,000x,_USDA,_ARS,_EMU2401.jpg")
![A fibrin clot formed in a test tube by the coagulase reaction](/Images/godic/202501/05/Coagulase+2401.JPG")
Coagulase is a protein enzyme produced by several microorganisms that enables the conversion of fibrinogen to fibrin. In the laboratory, it is used to distinguish between different types of Staphylococcus isolates. Importantly, S. aureus is generally coagulase-positive, meaning that coagulase negativity usually excludes S. aureus. However it is now known that not all S. aureus are coagulase-positive.