Bacterial adherence of Staphylococcus epidermidis to intraocular lenses: a bioluminescence and scanning electron microscopy study.

PURPOSE To analyze and compare the adherence of Staphylococcus epidermidis to intraocular lenses (IOLs) made of five different biomaterials (native or heparinized polymethylmethacrylate, silicone, hydrophilic acrylic, or hydrogel) and to detail the different steps and mechanisms of bacterial adhesion to a polymer. METHODS A clinical strain carrying the intercellular adhesion (ica) locus was used. In a previous study, the extent of bacterial binding was measured by counting. In this study, two different techniques, bioluminescence and scanning electron microscopy (SEM), were used to analyze the accuracy of each one, to obtain a comparison between the various IOLs, and to complete previous observations. The results were compared using both the Kruskal-Wallis and the Mann-Whitney nonparametric tests. RESULTS Bacterial adhesion was statistically weakest on hydrogel and then on hydrophilic acrylic polymer. Adhesion depended on the hydrophobicity or hydrophilicity of the biomaterials. Slight differences were found between the two methods, and these differences are explained. Furthermore, SEM observations highlighted two different patterns of bacterial adhesion (isolated bacteria and clusters of bacteria), assuming that hydrophobic IOLs (silicone and PMMA) probably facilitate bacterial colonization and biofilm production. CONCLUSIONS Attachment mechanisms may be different in each case, depending on the polymer material and the infecting organism, because there are various types of behavior among S. epidermidis strains. Hydrophilic polymer surfaces (hydrogel and probably hydrophilic acrylic) seem to be useful in avoiding the development of bacterial colonies and hence in preventing endophthalmitis. Fewer bacteria were attached, demonstrating inhibition or delay in bacterial colonization.