Why does S aureus cause most cases of septic arthritis?
S. aureus preferentially localizes to joints due to microbial surface components recognizing adhesive matrix molecules that are embedded in the cell wall peptidoglycan. These bind to host proteins including collagen, fibrinogen, fibronectin, and others. A collagen-binding protein, under the influence of a cna gene, has been found to be the most important virulence factor contributing to joint localization. Clumping factors (A and B) bind to fibrinogen, and fibronectin-binding protein (A and B) binds to fibronectin. Exotoxins produced by the bacteria contribute to the inflammatory response and bacteria survival.