Question

What are the two types of staphylococcal coagulase? Explain.

Answer 1

Answer.

Coagulase:

• Coagulase is a bacterial enzyme produced by disease-causing forms of staphylococcus.
• It has the ability to stimulate clot formation in plasma.
• It enables the conversion of fibrinogen to fibrin.
• This means it triggers blood clotting.

Genus Staphylococcus can be divided into two subgroups (Based on coagulase production):

1. Coagulase-positive
   • Example: Staphylococcus aureus
2. Coagulase-negative
   • Example: Staphylococcus epidermidis

Staphylococcus aureus strains possess two forms of coagulase (two types of staphylococcal coagulase):

• Bound coagulase
• Free coagulase

Bound coagulase:

• Also called clumping factor.
• It is attached to the staphylococcal cell wall.
• Bound coagulase can directly convert fibrinogen to insoluble fibrin and cause the staphylococci to clump.

Free coagulase:

• Free coagulase is liberated free into the surrounding medium.
• Free coagulase reacts with a globulin plasma factor to form staphylothrombin.
  • Globulin plasma factor is also known as the coagulase reacting factor or CRF.
• Staphylothrombin catalyzes the breakdown of fibrinogen to insoluble fibrin.
• Then forms the clot.

Additional information

Coagulase test:

This test is used to differentiate Staphylococcus aureus from Coagulase-negative Staphylococcus.

Principle:

• Coagulase causes the plasma to clot by converting fibrinogen to fibrin.
• Staphylococcus aureus strains possess two forms of coagulase
  • Bound coagulase
  • Free coagulase

Bound coagulase:

• Bound coagulase can directly convert fibrinogen to insoluble fibrin.
• It can be detected by the clumping of bacterial cells in the RAPID SLIDE TEST.

Free coagulase:

• Which converts fibrinogen to fibrin by activating a Globulin plasma factor or coagulase reacting factor present in the plasma.
• Free coagulase is detected by clotting in the TUBE TEST.

Note: A tube test always performs when the result of the slide test is not clear.