title: Attachment of Acanthamoeba to first- and second-generation silicone hydrogel contact lenses.
abstract: OBJECTIVE
  To investigate the attachment of Acanthamoeba to first- and second-generation silicone hydrogel contact lenses, and to determine if patient wear or the presence of a bacterial biofilm coating affects attachment characteristics.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Attachment to the silicone hydrogel lenses was compared with that to a conventional hydrogel control lens. Sixteen replicates (n = 16) were carried out for unworn, worn, and biofilm-coated lenses of each type.
  
  
  METHODS
  Unworn, worn, and Pseudomonas aeruginosa biofilm-coated first-generation (lotrafilcon A) and second-generation (galyfilcon A) silicone hydrogel and conventional hydrogel (etafilcon A) lens quarters were incubated for 90 minutes in suspensions of plate-cultured Acanthamoeba castellanii trophozoites.
  
  
  METHODS
  Trophozoites attached to one surface of each lens quarter were counted by direct light microscopy. Logarithmic transformation of data allowed the use of parametric analysis of variance for statistical analysis.
  
  
  RESULTS
  Attachment of Acanthamoeba was affected significantly by lens material type (P<0.001), with higher numbers of trophozoites attaching to the first-generation lotrafilcon A silicone hydrogel lens, compared with the second-generation galyfilcon A lens and the conventional hydrogel lens. Attachments to the latter 2 lenses did not differ significantly from each other (P = 0.126). Patient wear and the presence of a bacterial biofilm had no significant effect on attachment to the lotrafilcon A lens (P = 0.426) but did significantly increase attachment to the galyfilcon A (P<0.001) and the etafilcon A (P = 0.009) lenses; attachment to the latter 2 lenses was still significantly less than that found with the first-generation silicone hydrogel (P<0.001).
  
  
  CONCLUSIONS
  Acanthamoeba demonstrated a significantly greater affinity for the first-generation silicone hydrogel lens as compared with the second-generation silicone hydrogel and the conventional hydrogel. If exposed to Acanthamoeba (e.g., when showering or swimming, through noncontinuous wear and ineffective lens care regimes), first-generation silicone hydrogel lenses may promote a greater risk of Acanthamoeba infection due to the enhanced attachment characteristics of this lens material. However, prospective studies in patients are required to determine if these experimental results are clinically significant.
authors.affiliation: Department of Vision Sciences, Glasgow Caledonian University, Glasgow, Scotland, United Kingdom. t.k.beattie@gcal.ac.uk
authors.forename: Tara K
authors.initials: TK
authors.lastname: Beattie
authors.forename: Alan
authors.initials: A
authors.lastname: Tomlinson
authors.forename: Angus K
authors.initials: AK
authors.lastname: McFadyen
mesh_terms: D048248:Acanthamoeba castellanii / Q000302:isolation & purification / Q000502:physiology*; D000818:Animals; D001672:Biocompatible Materials; D018441:Biofilms / Q000254:growth & development; D003263:Contact Lenses, Hydrophilic / Q000382:microbiology / Q000469:parasitology*; D011550:Pseudomonas aeruginosa / Q000502:physiology; D012826:Silicone Elastomers
chemical_list: D001672:Biocompatible Materials; D012826:Silicone Elastomers