Coagulase Test | Staphylococcus aureus detection | Pathogen Detection | Basic Science Series

• Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. Here we will not go in to molecular details of clotting but to explain the function of coagulase, you need to know the basic concepts of coagulation or clotting. • • Coagulation or clotting is process of protease-driven chain reaction reactions. It occurs in four main steps. Step-1 i.e formation of prothrombin activator. After injury dozen of chemical factors are activated in blood that chemical reaction leads to the formation of prothrombin activator. • • Step-2. Activation of prothrombin to thrombin: Prothrombin cannot perform its function because it is inactivated form of the enzyme. Prothrombin activators catalyze the formation of thrombin, which is a highly efficient protease.

• Step 3 i.e Formation of fibrin: Thrombin cuts the tail ends of the individual fibrinogen molecules and that allows fibrinogen molecules to bond together to form chain-like polymeric structure.

• Step 4: i.e formation of clot After the formation of fibrin there is an induction of crosslinking of these chains that leads to the formation of a complex structure known as a clot. This is induced by the factor X111a. A clot or cross-linked fibrin is the gel-like structure that is formed on the site of injury and blocks the flow of blood. Thrombin plays a very important role in the process of coagulation and is designated as a human coagulase enzyme. This was a brief introduction to the process of coagulation. After understanding the process of coagulation, We will now discuss the bacterial coagulases.

• Most studied coagulase is Staphylococcus coagulase also referred to as staphylocoagulase, which is an extracellular protein composed of a variable number of 600–700 amino acid residues, and encoded by the CoQ gene. 10 serotypes of staphylocoagulase were identified.

• The staphylocoagulase-associated clotting is quite different from the physiological coagulation pathway. staphylocoagulase binds to prothrombin and its derivatives in a 1:1 ratio, to form a complex referred to as staphyloprothrombin. During host infection, staphylocoagulase activates the central coagulation zymogen, that is, prothrombin. The staphylocoagulase-prothrombin complex recognizes fibrinogen as a specific substrate, thereby converting it directly into fibrin. This is how the Staphylocoagulase induce fibrin formation during infection without activating the prothrombin to thrombin.

• Based on the production of staphylocoagulase the staphylococcus is divided into two different types. Coagulase positive staphylococci and coagulase-negative staphylococci. Coagulase positive staphylococci is S. aureus and coagulase-negative staphylococci are S. epidermid ... https://www.youtube.com/watch?v=9uJRb-GqcGM