Parallel induction by glucose of adherence and a polysaccharide antigen specific for plastic-adherent Staphylococcus epidermidis: evidence for functional relation to intercellular adhesion

Abstract

The initial attachment and the accumulation of Staphylococcus epidermidis on polymer surfaces in multilayered cell clusters embedded in amorphous slime, which together lead to the plastic-adherent phenotype detected by the adherence assay used in this study, have been proposed to be major virulence factors of these bacteria. An antigen specific for plastic-adherent S. epidermidis strains was detected by an indirect immunofluorescence test using absorbed antiserum raised against the strongly plastic-adherent S. epidermidis 1457. A coagglutination assay was established, which allowed the quantitation of the antigen in bacterial extracts under different physiologic growth conditions. Expression of the antigen and of plastic adherence depended significantly on the presence of glucose in the growth medium. Parallel to increased plastic adherence, a 32- to 64-fold increase in the amount of the antigen was detected in bacterial extracts of cells grown in tryptone soya broth (TSB) compared with that in extracts of cells grown in TSB lacking glucose. A parallel time-dependent increase of plastic adherence and expression of the antigen was observed after stimulation by glucose of stationary-phase cultures of plastic-adherent S. epidermidis strains grown in TSB lacking glucose. The antigen consisted most probably of polysaccharide, because its immunologic reactivity was completely abolished by periodate oxidation but was resistant to protease digestion. A significant proportion of cells of plastic-adherent as compared with nonadherent S. epidermidis strains grown in TSB were located in large cell clusters exceeding 50 cells, which completely disintegrated after periodate oxidation of the cell preparations. Periodate oxidation of adherent bacterial films in situ led to release of the adherent cells from the plastic surface. These results strongly indicate a functional relation of the antigen to adherence of S. epidermidis to polymer surfaces, most probably by mediating intercellular adhesion of cells leading to accumulation in multilayered cell clusters.