title: Bacterial adhesion to worn silicone hydrogel contact lenses.
abstract: OBJECTIVE
  The aim of this study was to, firstly, investigate whether silicone-hydrogel contact lenses (CL) are more or less susceptible to bacterial adhesion than conventional ones and, secondly, assess the influence of lens wear in the extent of bacterial adhesion. Four silicone-hydrogel CL (galyfilcon A, balafilcon A, lotrafilcon A, and lotrafilcon B) and one conventional hydrogel (etafilcon A) CL were tested.
  
  
  METHODS
  Bacterial adhesion experiments were performed on unworn and worn CL using the strain Staphylococcus epidermidis 9142. Worn lenses were obtained from a group of 31 subjects fitted with a silicone-hydrogel CL in one eye and a conventional hydrogel CL as contralateral pair. These lenses were used on a daily basis in combination with a multipurpose lens care solution. Adhesion assays were carried out in a parallel plate flow chamber, followed by image analysis. Hydrophobicity, roughness, and topography of the lenses surfaces were assessed through contact angle measurements and atomic force microscopy.
  
  
  RESULTS
  Unworn conventional and silicone-hydrogel CL were equally susceptible to bacterial adhesion of S. epidermidis. Conversely, worn conventional hydrogel (etafilcon A) were more prone to bacterial adhesion than worn silicone-hydrogel materials, which exhibited similar adhesion extents among them. The results also showed that the lens surface properties such as hydrophobicity, roughness, and surface topography changed during wear. The alteration of surface hydrophobicity of silicone and conventional hydrogel CL during wear had a great impact on lens bacterial adhesion susceptibility. Accordingly, balafilcon A becomes significantly less hydrophobic and less prone to bacterial adhesion after lens wear, whereas etafilcon A becomes more hydrophobic and also more susceptible to bacterial adhesion (p < 0.05).
  
  
  CONCLUSIONS
  Worn silicone-hydrogel galyfilcon A, balafilcon A, lotrafilcon A, and lotrafilcon B are equally prone to microbial adhesion of S. epidermidis and generally less susceptible than the conventional hydrogel.
authors.affiliation: Centro de Engenharia Biológica, Universidade do Minho, Portugal.
authors.forename: Lívia
authors.initials: L
authors.lastname: Santos
authors.forename: Diana
authors.initials: D
authors.lastname: Rodrigues
authors.forename: Madalena
authors.initials: M
authors.lastname: Lira
authors.forename: M Elisabete C D
authors.initials: ME
authors.lastname: Real Oliveira
authors.forename: Rosário
authors.initials: R
authors.lastname: Oliveira
authors.forename: Eva Yebra-Pimente
authors.initials: EY
authors.lastname: Vilar
authors.forename: Joana
authors.initials: J
authors.lastname: Azeredo
mesh_terms: D000328:Adult; D001422:Bacterial Adhesion / Q000502:physiology*; D015169:Colony Count, Microbial; D003263:Contact Lenses, Hydrophilic / Q000382:microbiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D018625:Microscopy, Atomic Force; D012826:Silicone Elastomers; D013212:Staphylococcus epidermidis / Q000502:physiology*; D013499:Surface Properties
chemical_list: D012826:Silicone Elastomers