Coagulase is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

produced by several

microorganisms A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in ...

that enables the conversion of

fibrinogen Fibrinogen (coagulation factor I) is a glycoprotein protein complex, complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted Enzyme, enzymatically by thrombin to fibrin ...

fibrin Fibrin (also called Factor Ia) is a fibrous protein, fibrous, non-globular protein involved in the Coagulation, clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerization, polymerize. ...

. In the

laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratories are found in a variety of settings such as schools ...

, it is used to distinguish between different types of ''

Staphylococcus ''Staphylococcus'', from Ancient Greek σταφυλή (''staphulḗ''), meaning "bunch of grapes", and (''kókkos''), meaning "kernel" or " Kermes", is a genus of Gram-positive bacteria in the family Staphylococcaceae from the order Bacillale ...

'' isolates. Importantly, '' S. aureus'' is generally coagulase-positive, meaning that a positive coagulase test would indicate the presence of ''S. aureus'' or any of the other 11 coagulase-positive ''Staphylococci''. A negative coagulase test would instead show the presence of coagulase-negative organisms such as '' S. epidermidis'' or '' S. saprophyticus''. However, it is now known that not all ''S. aureus'' are coagulase-positive. Whereas coagulase-positive staphylococci are usually

pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...

ic, coagulase-negative staphylococci are more often associated with

opportunistic infection An opportunistic infection is an infection that occurs most commonly in individuals with an immunodeficiency disorder and acts more severe on those with a weakened immune system. These types of infections are considered serious and can be caused b ...

. It is also produced by ''

Yersinia pestis ''Yersinia pestis'' (''Y. pestis''; formerly ''Pasteurella pestis'') is a Gram-negative bacteria, gram-negative, non-motile bacteria, non-motile, coccobacillus Bacteria, bacterium without Endospore, spores. It is related to pathogens ''Yer ...

''. Coagulase reacts with

prothrombin Prothrombin (coagulation factor II) is encoded in the human by the F2-gene. It is proteolytically cleaved during the clotting process by the prothrombinase enzyme complex to form thrombin. Thrombin (Factor IIa) (, fibrose, thrombase, throm ...

in the blood. The resulting complex is called ''staphylothrombin'', which enables the enzyme to act as a

protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalysis, catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products ...

to convert fibrinogen, a plasma protein produced by the liver, to fibrin. This results in clotting of the blood. 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. Bound coagulase is part of the larger family of

MSCRAMM MSCRAMM (acronym for "microbial surface components recognizing adhesive matrix molecules") are adhesin proteins that mediate the initial attachment of bacteria to host tissue, providing a critical step to establish infection. Examples include cl ...

adhesin proteins.

Coagulase test

The coagulase test has traditionally been used to differentiate ''

Staphylococcus aureus ''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often posi ...

'' from coagulase-negative

staphylococci ''Staphylococcus'', from Ancient Greek σταφυλή (''staphulḗ''), meaning "bunch of grapes", and (''kókkos''), meaning "kernel" or " Kermes", is a genus of Gram-positive bacteria in the family Staphylococcaceae from the order Bacillale ...

. ''S.aureus'' produces two forms of coagulase (i.e., bound coagulase and free coagulase). Bound coagulase, otherwise known as "clumping factor", can be detected by carrying out a slide coagulase test, and free coagulase can be detected using a tube coagulase test.

Slide test

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. A drop of plasma (rabbit plasma anticoagulated with

EDTA Ethylenediaminetetraacetic acid (EDTA), also called EDTA acid, is an aminopolycarboxylic acid with the formula . This white, slightly water-soluble solid is widely used to bind to iron (Fe2+/Fe3+) and calcium ions (Ca2+), forming water-solubl ...

is recommended) is placed on the inoculated saline drop corresponding to test, and mixed well, then the slide is rocked gently for about 10 seconds. * If 'positive', macroscopic clumping would be observed in the plasma within 10 seconds, with no clumping in the saline drop. * If 'negative', no clumping will be observed. If the slide coagulase test is negative, a tube test should follow as a confirmation. Clumping in both drops is an indication of autoagglutination, so a tube test should be carried out. Tube test is not performed each institutions but most of the result depends on blood cultures from lab.

Tube test

The tube test uses rabbit plasma that has been inoculated with a staphylococcal colony (i.e., Gram-positive cocci which are

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting ...

positive). The tube is then incubated at 37 °C for 1.5 hours. If negative, then incubation is continued up to 18 hours. * If 'positive' (e.g., the suspect colony is ''S. aureus''), the plasma will coagulate, resulting in a clot (sometimes the clot is so pronounced, the liquid will completely solidify). * If 'negative', the plasma remains a liquid. The negative result may be '' S. epidermidis'' but only a more detailed identification test can confirm this, using biochemical tests as in analytical profile index tests methods. A false negative can be perceived if the sample is not allowed to cool for about 30 minutes at room temperature or 10 minutes in the freezer, given that the serum can melt. If truly negative, the serum will remain liquid after cooling. * List of coagulase-positive staphylococci: ''Staphylococcus aureus'' subsp. ''anaerobius'', ''S. aureus subsp. aureus'', ''S. delphini'', ''S. hyicus'', ''S. intermedius'', ''S. lutrae'', and ''Staphylococcus schleiferi'' subsp. ''coagulans''. * List of coagulase-negative staphylococci of clinical significance: ''S. saprophyticus'', ''S.cohnii'' subsp. ''cohnii'', ''S. cohnii'' subsp. ''urealyticum'', ''S. captitus'' subsp. ''captitus'', ''S. warneri'', ''S.hominis'', ''S.epidermidis'', ''S. caprae'', and ''S.lugdunensis''

References

External links

* Tube coagulase test - rabbit plasm
video
*

{{Portal bar, Biology, border=no Microbiology EC 3.4.23