Koagulaasi

Koagulaasi is an enzyme produced by certain bacteria, most notably Staphylococcus aureus. It catalyzes the transformation of soluble fibrinogen in blood plasma into insoluble fibrin, causing plasma to clot. This activity can aid the bacteria by creating a localized barrier against immune defenses.

Two forms of koagulaasi are recognized: bound coagulase, which is attached to the bacterial cell wall (also called clumping factor), and free coagulase, which is secreted into the surrounding environment. Bound coagulase interacts with fibrinogen to produce clumping of cells in slide tests, while free coagulase forms a complex with prothrombin (staphylothrombin) that converts fibrinogen to fibrin in tube tests, leading to clot formation.

In clinical microbiology, koagulaasi testing helps distinguish Staphylococcus aureus (koagulaasi-positive) from most koagulaasi-negative staphylococci. The tube coagulase test detects free coagulase activity, whereas the slide test assesses bound coagulase (clumping factor) directly on cells.

Virulence: Coagulase activity can contribute to pathogenicity by promoting clot formation around bacteria, potentially aiding immune evasion and persistence at infection sites.

Limitations and interpretation: Although koagulaasi positivity is a key trait of S. aureus, some strains or related species may vary in expression, and test results can be influenced by conditions such as the source of plasma and temperature. Therefore, coagulase testing is often used in conjunction with other biochemical and molecular tests for accurate identification.