title: The influence of lens material and lens wear on the removal and viability of Staphylococcus epidermidis.
abstract: OBJECTIVE
  The aim of this study was to evaluate the influence of lens material and lens wear on the removal capability of Staphylococcus epidermidis. Assessment of viability of remaining adhered bacteria was another goal of this work. Four silicone hydrogel materials (galyfilcon A, balafilcon A, lotrafilcon A, lotrafilcon B) and one conventional hydrogel material (etafilcon A) were assayed.
  
  
  METHODS
  Detachment studies on S. epidermidis were carried out in a parallel plate flow chamber. Contact lenses (CLs) were fitted to the bottom of the flow chamber and a bacterial suspension was perfused into the system, promoting bacterial adhesion. Afterwards, detachment was stimulated using a multipurpose solution (MPS, ReNu Multiplus) and the percentage of removed bacteria estimated through microscopic observation and enumeration. Remaining adhered bacteria were stained with propidium iodide (PI) and enumerated in order to assess their viability. Additionally, the worn lenses were observed by confocal laser scanning microscopy (CLSM) to visualize bacterial distribution along the lens surfaces.
  
  
  RESULTS
  Bacterial removal was significant (p<0.05) for both unworn and worn galyfilcon A and etafilcon A. Galyfilcon A exhibited a detachment percentage of 59.1 and 63.5 while etafilcon A of 62.6 and 69.3, both for unworn and worn lenses, respectively. As far as bacterial viability is concerned, it was found that worn lenses exhibit a superior amount of non-viable bacteria than unworn CLs. Images obtained by CLSM revealed an irregular bacterial distribution for all lens materials.
  
  
  CONCLUSIONS
  It appears that surface and/or bulk structure of the lens material affects removal of S. epidermidis while CL wear influences their viability.
authors.affiliation: Institute for Biotechnology and Bioengenhary, Centre of Biological Engineering, University of Minho, Braga, 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-Pimentel
authors.initials: EY
authors.lastname: Vilar
authors.forename: Joana
authors.initials: J
authors.lastname: Azeredo
mesh_terms: D000328:Adult; D001422:Bacterial Adhesion / Q000187:drug effects / Q000502:physiology*; D018639:Contact Lens Solutions / Q000494:pharmacology; D003263:Contact Lenses, Hydrophilic / Q000382:microbiology*; D005260:Female; D006801:Humans; D020100:Hydrogels; D008297:Male; D008689:Methacrylates; D018613:Microscopy, Confocal; D012828:Silicones; D013212:Staphylococcus epidermidis / Q000502:physiology*
chemical_list: D018639:Contact Lens Solutions; D020100:Hydrogels; D008689:Methacrylates; D012828:Silicones; C005044:hydroxyethyl methacrylate