Coagulase is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...

produced by several

microorganisms A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

that enables the conversion of

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

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

. 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. Laboratory services are provided in a variety of settings: physici ...

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

Staphylococcus ''Staphylococcus'' is a genus of Gram-positive bacteria in the family Staphylococcaceae from the order Bacillales. Under the microscope, they appear spherical ( cocci), and form in grape-like clusters. ''Staphylococcus'' species are facultat ...

'' 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 ''Staphylococcus epidermidis'' is a Gram-positive bacterium, and one of over 40 species belonging to the genus ''Staphylococcus''. It is part of the normal human microbiota, typically the skin microbiota, and less commonly the mucosal microbiota ...

'' or ''

S. saprophyticus ''Staphylococcus saprophyticus'' is a Gram-positive coccus belonging to the genus ''Staphylococcus''. ''S. saprophyticus'' is a common cause of community-acquired urinary tract infections. History ''Staphylococcus saprophyticus'' was not recogni ...

''. However, it is now known that not all ''S. aureus'' are coagulase-positive. Whereas coagulase-positive ''Staphylococci'' are usually

pathogen In biology, a pathogen ( el, πάθος, "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 ger ...

ic, coagulase-negative ''Staphylococci'' are more often associated with

opportunistic infection An opportunistic infection is an infection caused by pathogens (bacteria, fungi, parasites or viruses) that take advantage of an opportunity not normally available. These opportunities can stem from a variety of sources, such as a weakened immun ...

. It is also produced by ''

Yersinia pestis ''Yersinia pestis'' (''Y. pestis''; formerly '' Pasteurella pestis'') is a gram-negative, non-motile, coccobacillus bacterium without spores that is related to both '' Yersinia pseudotuberculosis'' and '' Yersinia enterocolitica''. It is a facu ...

''. Coagulase reacts with

prothrombin Thrombin (, ''fibrinogenase'', ''thrombase'', ''thrombofort'', ''topical'', ''thrombin-C'', ''tropostasin'', ''activated blood-coagulation factor II'', ''blood-coagulation factor IIa'', ''factor IIa'', ''E thrombin'', ''beta-thrombin'', ''gamma- ...

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 catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the form ...

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") adhesin proteins mediate the initial attachment of bacteria to host tissue, providing a critical step to establish infection. Examples include protein A, 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 posit ...

'' from coagulase-negative

staphylococci ''Staphylococcus'' is a genus of Gram-positive bacteria in the family Staphylococcaceae from the order Bacillales. Under the microscope, they appear spherical ( cocci), and form in grape-like clusters. ''Staphylococcus'' species are facultativ ...

. ''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) is an aminopolycarboxylic acid with the formula H2N(CH2CO2H)2sub>2. This white, water-soluble solid is widely used to bind to iron (Fe2+/Fe3+) and calcium ions (Ca2+), forming water-soluble complexes ev ...

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 t ...

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 ''

'' but only a more detailed identification test can confirm this, using biochemical tests as in

analytical profile index The analytical profile index or API is a classification of bacteria based on biochemical tests, allowing fast identification. This system is developed for quick identification of clinically relevant bacteria. Because of this, only known bacteria ...

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
*

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