What is the significance of coagulase test?

Coagulase test is used to differentiate Staphylococcus aureus (positive) which produce the enzyme coagulase, from S. epidermis and S. saprophyticus (negative) which do not produce coagulase.

Is coagulase test a diagnostic test?

Today, even though a variety of diagnostic tests are available to identify S. aureus in the clinical microbiology laboratory, the coagulase tests remain simple, reliable methods of identification.

What is the difference between the slide and tube test for coagulase?

Slide coagulase test is done to detect bound coagulase or clumping factor. Tube coagulase test is done to detect free coagulase.

Which coagulase-negative staphylococci are considered more significant and might need to be identified to the species level?

S epidermidis is the most important coagulase-negative staphylococcus (CNS) species and is the major cause of infections associated with prosthetic devices and catheters.

What are the two types of coagulase test?

The enzyme coagulase, produced by a few of the Staphylococcus species, is a key feature of pathogenic Staph. The enzyme produces coagulation of blood, allowing the organism to “wall ” its infection off from the host’s protective mechanisms rather effectively. There are 2 methods: slide test and tube test.

How is coagulase test performed?

A slide coagulase test is run with a negative control to rule out autoagglutination. Two drops of saline are put onto the slide labeled with sample number, Test (T) and control (C). The two saline drops are emulsified with the test organism using a wire loop, straight wire, or wooden stick.

What is the substrate of the coagulase test?

Several animal plasmas including hu- man plasma will serve as a satisfactory substrate for coagulase testing. 1 We in- vestigated the nature and action of coagu- lase activity by ten isolates of Staphy- lococcus aureus and tested the suitability of four human plasma pools and rabbit plasma as substrates.

Why is coagulase a virulence factor?

Coagulase is tightly bound to the surface of the bacterium S. aureus and can coat its surface with fibrin upon contact with blood. The fibrin clot may protect the bacterium from phagocytosis and isolate it from other defenses of the host. The fibrin coat can therefore make the bacteria more virulent.

Why do we inspect coagulase test tubes after 4 hours is this a critical time frame?

3. When checking results of the Coagulase Test, tubes should be observed every 30 minutes during the first four hours of incubation. Some strains of Staphylococcus aureus produce fibrinolysin which may lyse clots formed earlier.

Which bacteria is the coagulase test useful for identification?

Coagulase testing is the single most reliable method for identifying Staphylococcus aureus[9]. Coagulase production can be detected using either the slide coagulase test (SCT) or the tube coagulase test (TCT).

What are the limitations of a coagulase test?

Limitations of Coagulase Test. Slide Test. Equivocal: Clumping in both drops indicates that the organism autoagglutinates and is unsuitable for the slide coagulase test. Tube Test. Test results can be positive at 4 hours and then revert to negative after 24 hours.

What are the limitations of the slide coagulase test for Staphylococcus aureus?

Interpretation: Slide coagulase test is the main method used to identify S. aureus in clinical laboratories but it has some limitations. About 15% of ordinary strains of S. aureus and many more of MRSA give negative reactions. Few species of coagulase-negative staphylococci give positive reactions.

What does a positive coagulase test look like?

Picture 2 : A slide coagulase test; one slide is negative and the other one has clumping which indicates a positive coagulase test. (The actual glass slide coagulase test; one is completely smooth while the other has visible clumping indicative of a positive coagulase test.)

What is a coagulase test for rabbits?

The primary purpose of the coagulase test is to find out if a particular bacterium produces coagulase, which is an enzyme that can coagulate rabbit plasma into a solid clot. (3, 4) Coagulase test can be done in two ways: slide and tube coagulase test.