adhesiinid

Adhesins (adhesiinid in Estonian) are microbial surface proteins that mediate adhesion to host tissues or abiotic surfaces. They play a key role in colonization, tissue tropism, and the initiation of many infections by enabling pathogens to attach to specific receptors on host cells and to resist removal by fluids or mechanical forces.

Adhesins are diverse in form. They include fimbrial (pili) adhesins, such as type 1 fimbriae with FimH that bind to mannose-containing receptors, and P fimbriae that recognize glycolipid receptors in the urinary tract, as well as afimbrial outer membrane proteins. In Gram-positive bacteria, adhesins commonly take the form of surface proteins known as MSCRAMMs (microbial surface components recognizing adhesive matrix molecules) that bind extracellular matrix components such as fibronectin, fibrinogen, and collagen (examples include Staphylococcus aureus FnBPs and ClfA).

Adhesin–receptor interactions determine host range and tissue tropism. Receptors include glycoproteins and glycolipids on epithelial or endothelial cells, as well as extracellular matrix proteins. Some adhesins recognize carbohydrate moieties, others bind protein receptors such as integrins or collagen. Variation in adhesin expression or sequence—through phase variation or antigenic variation—can help pathogens adapt to hosts and evade immune responses.

Clinical relevance: adhesins are critical virulence factors and serve as targets for vaccines and anti-adhesion therapies designed to block attachment. Studying adhesins informs understanding of colonization, infection dynamics, and the design of interventions to prevent bacterial establishment on host surfaces or medical devices.