QUANTITATIVE COMPARISON OF CLUMPING FACTOR-MEDIATED AND COAGULASE-MEDIATED STAPHYLOCOCCUS-AUREUS ADHESION TO SURFACE-BOUND FIBRINOGEN UNDERFLOW

The contributions of clumping factor and coagulase in mediating Staphy lococcus aureus adhesion to surface-adsorbed fibrinogen have been quan tified by using a new methodology and analysis. The attachment or deta chment kinetics of bacteria were directly observed in a radial flow ch amber with a well-defined laminar flow field and a spatially varying s hear rate and were quantified by recursively scanning the chamber surf ace and counting cells via automated video microscopy and image analys is with a motorized stage and focus control. Intrinsic rate constants for attachment or detachment were estimated. as functions of shear rat e for the wild-type Newman strain of S. aureus and for mutants lacking clumping factor, coagulase, or both proteins on surfaces coated with plasma, fibrinogen, or albumin. Clumping factor, but not coagulase, in creased the probability of attachment and decreased. the probability o f detachment of S. aureus on plasma-coated surfaces; however, both clu mping factor and, to a lesser extent, coagulase increased the probabil ity of attachment on the purified-fibrinogen-coated surface. All mutan ts were resistant to detachment on the purified-fibrinogen-coated surf ace, suggesting the possibility of an additional adhesion mechanism wh ich was independent of coagulase or clumping factor and effective only for fully attached cells. Together, these results suggest that the pr esence of clumping factor plays the primary role in enhancing adhesion to surfaces with adsorbed fibrinogen, not only by enhancing the proba bility of cell attachment but also by increasing the strength of the r esulting adhesion.