Adherence of staphylococci to various intraocular lenses with different levels of hydrophobicity

Background: A major goal in research on intraocular lenses (101) is the development of new polymers and modifications to reduce foreign-body reactions after implantation. This effect may be achieved by a reduction in the surface hydrophobicity of the polymers. To illustrate the influence of surface modifications on bacterial adhesiveness, the most often isolated organism in "low-grade" postoperative endophthalmitis, Staphylococcus epidermidis, was used. Materials and methods: For this reason three strains of this species, the type strain ATCC 14990 and two clinical isolates (8687, 6579 1) with different hydrophobic surface properties were studied. 101, used in the ex periments were either made of PMMA or silicone with modified surfaces (unpolished, polished, heparinized). The adhesiveness of H-3-thymidin-labeled bacteria was calculated/mm(2) of lens surface. Each experiment was performed in triplicate and repeated three times. Results: The hydrophobic-type strain showed stronger adherence to unpolished PMMA surface (8000 bacteria per mm(2)) compared to the polished (5200 bacteria/mm(2)). In contrast, the hydrophilic strain adhered with 2000 bacteria/mm(2) to the unpolished and with 4200 bacteria/mm(2) to the polished surface. Polishing PMMA lenses diminished the differences between the three strains. However, surface passivation of silicone lenses increased the adhesion rate of the hydrophilic strain up to 9600 bacteria/mm(2). Treatment of PMMA lenses with heparin increased the adhesiveness of the hydrophilic strain and reduced the adhesion rate of the hydrophobic type strain to 250 bacteria/mm(2). Conclusions: It was demonstrated that bacterial adherence to IOL also involves hydrophobic interactions. Obviously, however, that adherence reflects a complex of interactions between the two surfaces.