Here you will learn about the “Coagulase test principle procedure”. The main purpose of this test is to differentiate the staph aureus from other types of staph. Staph aureus contains a coagulase enzyme that coagulates plasma.
Note: Coagulase is an enzyme that exists in one type of staph (Staph aureus). Therefore this test named as coagulase test.
Coagulase has two types
- Free coagulase: This kind of coagulase converts fibrinogen to fibrin by activating coagulase-reacting factors in the plasma. Such a kind of coagulase is detected by the TUBE method.
- Bound coagulase: It directly converts the fibrinogen to fibrin. The slide method is used for its detection.
Principle of coagulase test
The principle of coagulase is simple. It (Coagulase) produces a clot in the plasma by converting the FIBRINOGEN to FIBRIN.
Reagents of coagulase test
- Fresh plasma (Human or Rabbit)
- Normal saline
Coagulase test procedure
The coagulase test has two procedures which are below.
- Slide method
- Tube method
Slide method of coagulase test
In this method following 3 steps are performed.
- 1. Place a drop of normal saline on the slide.
- 2. Emulsify the colony from the culture, to make the suspension.
- 3. Add one drop of plasma to the suspension and look for clumping within 10 seconds.
Coagulase test tube method
It has the following steps Coagulase test tube method.
- Dilute plasma in a 1:6 ratio in normal saline.
- Take the 3 test tubes and label them as a positive control, negative control, and test tube
- Drop 0.5 ml diluted plasma in each tube.
- Add five drops of a saline broth culture of the organism to the labeled tube. add 5 drops of staph aureus suspension in a positive control tube.
- Add five drops of sterile broth to the label as a negative control.
- After mixing gently, incubate at 36-37 C.
- Look for clumping after one hour, three hours, and after six hours.
Coagulase Positive bacteria
Staph aureus bacteria is known as coagulase-positive bacteria. Because it has a coagulase enzyme and makes a clot while converting fibrinogen to fibrin.
Coagulase Negative Bacteria
Staphylococcus bacteria other than staph aureus are Known as Coagulase-negative bacteria because these bacteria lack coagulase enzymes, so they cannot make a clot in the plasma.