FACTORS AFFECTING STAPHYLOCOCCUS-EPIDERMIDIS ADHESION TO CONTACT-LENSES

Background. Staphylococcus epidermidis is a major causative agent of i nfectious keratitis associated with contact lens wear. Adhesion of thi s bacterium to contact lenses may contribute to the pathogenesis of in fection and could be influenced by lens surface properties, packaging/ storage solutions, and vary among different strains according to the l evel or type of adhesins expressed. Methods. Adhesion of six clinical isolates of S. epidermidis to three different contact lens materials w as tested. Adhesion assays were performed on lenses immediately after removal from their packages, and also after lenses were soaked in ster ile phosphate buffered saline (PBS) for 7 days to dilute the packaging solution. Results. For lenses tested immediately upon removal from th eir packaging, adhesion to polymacon (in PBS with 0.1% polyvinyl alcoh ol) was significantly greater than to etafilcon A (in borate buffered saline) and vifilcon A (in PBS). After soaking, adhesion to polymacon lenses was significantly less than to the other lens materials. This p attern was consistent for all strains, although major differences in b aseline adhesion levels existed between strains, with exopolysaccharid e (slime)-positive bacteria being more adherent to lenses. Conclusions . Properties of contact lens materials were not the sole determinant o f viable S. epidermidis adhesion to lenses. Strain variability, includ ing levels of exopolysaccharide expression, and the solution used for lens immersion also influenced adhesion.