Platelet thrombus formation induced by S aureus and its fibrinogen-binding clumping factor.

(A) Schematic representation of clumping factor A (ClfA) and of the recombinant fragment containing the fibrinogen-binding region (rClfA) used in these experiments. (B) Blood, without or with addition of the anti-FcγRIIA antibody IV.3 (20 μg/mL) or the anti-α_IIbβ₃ antibody LJ-CP8 (50 μg/mL), as indicated (incubation: 15 minutes), was perfused over coverslips coated with a solution of rClfA (100 μg/mL). Surface coverage by platelets and platelet thrombi on an area of 45 000 μm²was measured after 8 minutes of perfusion at the indicated wall shear rates. Single frame images show the surface after 8 minutes of perfusion at 340 s⁻¹. (C) Coverslips were first coated with fibrinogen (200 μg/mL) or fibronectin (100 μg/mL), followed by wild-type or ΔClfA strains of S aureus(10⁸ bacteria/mL), or no bacteria in the control. Blood, treated as described in the legend to panel B, was perfused at 1500 s⁻¹ for 10 minutes before measuring the volume of platelet thrombi on an area of 45 000 μm².