Coagulase test principle, procedure

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

1. 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.
2. 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

1. Fresh plasma (Human or Rabbit)
2. Normal saline

Coagulase test procedure

The coagulase test has two procedures which are below.

1. Slide method
2. 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.

1. Dilute plasma in a 1:6 ratio in normal saline.
2. Take the 3 test tubes and label them as a positive control, negative control, and test tube
3. Drop 0.5 ml diluted plasma in each tube.
4. 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.
5. Add five drops of sterile broth to the label as a negative control.
6. After mixing gently, incubate at 36-37 C.
7. 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.