Effect of surface modifications of intraocular lenses on the adherence of Staphylococcus epidermidis

The development of polymers with different surface properties and surface modifications of intraocular lenses (IOL) should reduce foreign body reactions after implantation by reducing the surface hydrophobicity of the lenses. It was examined how far such surface variations influenced the adhesiveness of bacteria. The most common organism isolated from cases of postoperative endophthalmitis is Staphylococcus epidermidis. For this reason, three strains of this species, the type strain ATCC 14990 and two clinical isolates (8687, 6579 I), with different hydrophobic surfaces, were studied. IOL made of PMMA, silicone, and a copolymer as well as PMMA lenses with modified surfaces (unpolished, polished, silanized, and heparinized) were used. Bacteria were radiolabelled with 3H-thymidine and the adherent bacteria were calculated per mm2 of lens surface. The three strains adhered better to the unpolished surface of silicone than to PMMA. Treatment of PMMA surface by polishing diminished the differences between the strains. An influence of hydrophobic interactions on the adherence of S. epidermidis ATCC 14990 was demonstrated. The adherence of this hydrophobic type strain was clearly reduced by heparinization of the PMMA surface. In contrast, the hydrophilic catheter isolate 6579 I adhered better to modified surfaces. This strain differed clearly in its PFGE pattern from both hydrophobic strains. Hydrophobic interactions play a role in the bacterial adherence to intraocular lenses in vitro and in vivo. Modifications of polymer surfaces, however, can result in rather different effects depending on the bacterial surface composition and properties.