Staphylococcus Epidermidis Attachment To Human Endothelial Cells Is Mediated Through Its 20-Kda Ps

Background: The way by which bacteria attach to eukaryotic host cells is very critical to microbial pathogenesis. It has been shown that one mode of staphyloccocal attachment utilizes glycosaminoglycan (GAG) chains which extend from the surface membrane of host cells. This attachment can be partially decreased by preincubation of the bacteria with various polysulfated agents. We have isolated an acidic sulphated polysaccharide (20-kDa PS) from S. epidermidis’ slime that constitutes its major antigenic component. Since 20-kDa PS bears sulphate groups we wanted to clarify whether the polysaccharide could block the GAG-binding sites on the surface of the bacteria and diminish the bacterial attachment. Therefore, we studied the effect of 20-kDa PS on bacterial attachment of human umbilical vein endothelial cells (HUVEC). Methods: A modified ELISA which uses biotinylated bacteria for the estimation of attached bacteria onto fixed HUVEC was used. A slime-producing S. epidermidis reference strain (ATCC35983) and a non-slime-producing (ATCC12228) were utilized. HUVEC were harvested from human umbilical veins by treatment with collagenase. Results: Differences in attachment of the two reference strains to HUVEC was observed. More specifically, adherence of slime producing S. epidermidis was greater (over 40%) as compared to non slime-producing strain. Furthermore, preincubation of bacteria with 20-kDa PS resulted to a significant increase of the attachment of both bacterial strains. A stimulation of the bacterial attachment appeared to be dose-dependent for the slime-producing strain. Also, the presence of 20-kDa PS accelerated attachment of non-slime-producing S. epidermidis to HUVEC. Conclusion: Attachment of slime-producing S. epidermidis to HUVEC is greater than its slime-negative counterpart. The presence of 20-kDa PS is favorable to bacterial attachment to HUVEC suggesting that this polysaccharide binds to S. epidermidis and uses a different mechanism in order to adhere on the surface of endothelial cells and its blocking may be of great therapeutic value.