What does coagulase mean?
Coagulase is an enzyme produced primarily by the bacterium Staphylococcus aureus and a few related microorganisms. Its defining effect is to accelerate the clotting of blood plasma: it converts fibrinogen into fibrin, the protein meshwork that forms a clot. For the bacterium this is a defensive strategy, since surrounding itself with a fibrin barrier helps shield it from the host's immune cells. Because of this behaviour, detection of coagulase has become a cornerstone of diagnostic microbiology — the 'coagulase test' distinguishes virulent, coagulase-positive S. aureus from the many benign, coagulase-negative staphylococci that normally inhabit human skin. The term belongs almost entirely to medical and scientific registers, appearing in laboratory reports, textbooks, and research papers rather than everyday conversation. Its study matters because it links a single enzymatic property directly to bacterial pathogenicity, making coagulase both a practical diagnostic marker and a subject of ongoing immunological and therapeutic interest.
nounAn enzyme produced chiefly by pathogenic staphylococci, notably Staphylococcus aureus, that accelerates the clotting of blood plasma by converting fibrinogen to fibrin.
- An enzyme, produced especially by Staphylococcus aureus and some other bacteria, that promotes the clotting of blood plasma by acting on fibrinogen.
"Laboratory tests for coagulase are routinely used to distinguish Staphylococcus aureus from less harmful staphylococcal species."
"Strains of S. aureus that produce abundant coagulase tend to be more virulent than those that do not."
"A positive slide coagulase test prompted the laboratory to confirm the isolate as Staphylococcus aureus by additional biochemical testing."
The plural appears mainly in scientific writing when comparing enzymes from different bacterial species or strains.
"Researchers have characterized coagulases from several staphylococcal species."
The coagulase test is how microbiologists tell the notorious Staphylococcus aureus apart from its harmless cousins — one drop of plasma can expose a killer bacterium.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of coagulase
Coagulase derives from the Latin coagulum ('a curdling'), the source also of English 'coagulate' and 'coagulation'. The word was formed in modern scientific usage from 'coagul-' plus '-ase', the standard suffix for enzymes coined in late nineteenth-century biochemistry. It entered English alongside the rise of bacteriology, as researchers identified the specific agent by which staphylococci clotted plasma.
How coagulase is actually used
Strictly a technical term of microbiology and medicine; it is rare outside laboratory reports, textbooks, and research literature. In clinical usage it most often appears adjectivally in the fixed phrases 'coagulase-positive' and 'coagulase-negative', which classify staphylococcal species by their production of the enzyme.
Easily confused with coagulase
'Coagulate' is a verb meaning to cause a liquid to clot or thicken, whereas 'coagulase' is the specific enzyme produced by certain bacteria that brings about that clotting.