Microbiology: Coagulase Test

The video tutorial explains the role of fibrinogen in blood clotting, highlighting how it is converted to fibrin during tissue injury. It discusses the enzyme coagulase, produced by Staphylococcus aureus, which can cause clotting without injury. The tutorial describes an experiment using plasma inoculated with bacteria to test for coagulase presence, explaining how to interpret positive and negative results. Real examples of coagulase tests are shown, demonstrating the appearance of clotted and unclotted samples.

What is the role of fibrinogen in the blood?

• It is responsible for carrying oxygen in the blood.

• It is a type of white blood cell.

• It is an inactive protein that is converted to fibrin during injury.

• It is an active protein that prevents clotting.

How does Staphylococcus aureus affect blood clotting?

• It dissolves existing blood clots.

• It uses coagulase to cause clotting without injury.

• It has no effect on blood clotting.

• It prevents blood from clotting.

Why is plasma used instead of whole blood in the coagulase test?

• Whole blood is too expensive.

• Whole blood clots too quickly.

• Plasma is easier to obtain.

• Plasma does not contain red blood cells, making results clearer.

What indicates a positive coagulase test result?

• The fluid evaporates.

• The fluid turns red.

• The fluid remains completely liquid.

• The presence of visible clumps or full clotting.

What does a negative coagulase test result look like?

• The fluid is completely clotted.

• The fluid remains liquid with no clumps.

• The fluid changes color.

• The fluid has visible clumps.

Which bacteria is commonly coagulase positive?

• Escherichia coli

• Bacillus subtilis

• Staphylococcus aureus

• Staphylococcus epidermidis

How can you differentiate between Staphylococcus aureus and Staphylococcus epidermidis in a coagulase test?

• Both show the same results.

• Staphylococcus aureus shows clumping or clotting.

• Staphylococcus epidermidis is coagulase positive.

• Staphylococcus aureus is coagulase negative.