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 oxide surfaces that had been incubated in human plasma at different concentrations. Adhesion of bacteria did not occur at high incubation concentrations of plasma or when the surface had been incubated in egg albumin. However, significant adhesion was observed when plasma was diluted. With the use of 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 adsorption of blood plasma and subsequent adhesion of S. aureus. In these experiments, blood plasma was incubated under a convex lens placed upside-down on the silicon oxide surface. This method creates a continuous 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 attached bacteria by means of optical methods. Adhesion of bacteria occurred 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 diluted plasma, or plasma incubated in narrow space, is a variant of the 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 phenomenologically similar methods.(ABSTRACT TRUNCATED AT 250 WORDS)