LENS-ON-SURFACE METHOD FOR INVESTIGATING ADHESION OF STAPHYLOCOCCUS-AUREUS TO SOLID-SURFACES INCUBATED IN BLOOD-PLASMA

Adhesion of Staphylococcus aureus was investigated on flat silicon oxi de surfaces that had been incubated in human plasma at different conce ntrations. Adhesion of bacteria did not occur at high incubation conce ntrations of plasma or when the surface had been incubated in egg albu min. However, significant adhesion was observed when plasma was dilute d. With the use of an antibody method, it was noted that the adhesion of the bacteria coincided with adsorbed fibrinogen, and possibly also with IgG. We also investigated the effect of ''narrow space'' on the a dsorption of blood plasma and subsequent adhesion of S. aureus. In the se experiments, blood plasma was incubated under a convex lens placed upside-down on the silicon oxide surface. This method creates a contin uous gradient of space from the contact point of the lens and outward. After rinsing off the plasma and the lens, the surface was incubated with a suspension of S. aureus followed by quantification of the attac hed bacteria by means of optical methods. Adhesion of bacteria occurre d in several circular zones that were easily detectable with the naked eye or by the means of simple optical methods. In addition, in these experiments, adhesion coincided with adsorbed fibrinogen or IgG at the surfaces. The increased bacterial adhesion to surfaces incubated in d iluted plasma, or plasma incubated in narrow space, is a variant of th e so-called ''Vroman effect.'' With a model protein system consisting of fibrinogen and IgG and the corresponding antibodies, we demonstrate that ''dilution'' and ''incubation in narrow space'' are two phenomen ologically similar methods. This methodologic investigation demonstrat ed that the lens-on-surface method is superior for the investigation o f these aspects of bacterial adhesion. (C) 1994 John Wiley and Sons, I nc.