Clumping factor

The clumping factor is an ectotoxin (coagulase) cell wall formed by Staphylococcus aureus. The binding of the clumping factor to the fibrinogen receptor leads to the activation of the fibrin monomers and the polymerisation of the fibrin.

The clumping factor is an important factor to classify the pathogenicity of Staphylococcus aureus. In medical microbiology, the clumping factor is the diagnostic criterion for differentiating Staphylococcus aureus from other coagulase-negative Staphylococci such as S. epidermidis. The coagulase reaction is used to detect the clumping factor.

The coagulase and the clumping factor A cause a local coagulation of fibrin and thus the formation of a fibrin wall with which S.aureus coats itself and is no longer recognised by antibodies. This allows the bacterium to multiply unhindered. The formation of fibrolysin then breaks down the protective barrier and, by means of the bacterial enzymes hyaluronidase, DNase, lipase and haemolysin, it is now able to lyse intercellular connective tissue and parenchyma cells and invasively penetrate the host organism. A number of SA-mediated infections are due to the formation of toxins: enterotoxins A-E cause vomiting and diarrhoea.