The Effects of Magnesium, Calcium, EDTA, and pH on the <i>In Vitro</i> Adhesion of <i>Staphylococcus epidermidis</i> to Plastic

J-STAGE
  • DUNNE Jr. Wm. Michael
    Department of Pathology, Children's Hospital of Wisconsin, Medical College of Wisconsin
  • BURD Eileen M.
    Department of Pediatrics, Children's Hospital of Wisconsin, Medical College of Wisconsin

抄録

The effects of increasing concentrations of magnesium (Mg2+), calcium (Ca2) or EDTA, and pH on the adhesion of five slime-positive strains of Staphylococcus epidermidis (Se+) to plastic were examined using an in vitro microwell assay. The addition of Mg2+ (as either MgSO4 or MgCl2) to the bacterial suspension in concentrations as low as 16μM significantly enhanced the adhesion of all test strains to plastic (P<0.001). Similarly, the addition of Ca2+ (as CaCl2) in concentrations exceeding 128μM produced a significant increase in the adhesion of all test strains, but not to the extent observed with Mg2+. In contrast, the adhesion of all test strains to plastic was significantly reduced in the presence of EDTA at concentrations greater than 8mM. However, EDTA in concentrations as low as 0.25mM caused a significant decrease in the adhesion of two strains of Se+. The effect of pH was variable, but at a pH of 5.0 and 6.0, the adhesion of all test strains was significantly reduced compared to control values at a pH of 7.0. Two strains showed a significant increase in adhesion at a pH of 8.0. We also compared the effects of these variables on the adherence of a slime-negative phase variant derived from a slime-positive parent strain. With the exception of pH, the adhesion of both strains in response to increasing divalent cations or EDTA was similar. These data indicate that, in addition to hydrophobic interactions, ligand-specific binding, and slime production, pH and divalent cations, especially Mg2+, are important determinants of the adhesion of S. epidermidis to plastic surfaces in vitro. This has possible implications in the pathogenesis of biomedical implant infections caused by these organisms.

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