Bacterial adhesion to conventional hydrogel and new silicone-hydrogel contact lens materials.
BACKGROUND
As bacterial adhesion to contact lenses may contribute to the pathogenesis of keratitis, the aim of our study was to investigate in vitro adhesion of clinically relevant bacteria to conventional hydrogel (standard HEMA) and silicone-hydrogel contact lenses using a bioluminescent ATP assay.


METHODS
Four types of unworn contact lenses (Etafilcon A, Galyfilcon A, Balafilcon A, Lotrafilcon B) were incubated with Staphylococcus epidermidis (two different strains) and Pseudomonas aeruginosa suspended in phosphate buffered saline (PBS). Lenses were placed with the posterior surface facing up and were incubated in the bacterial suspension for 4 hours at 37 degrees C. Bacterial binding was then measured and studied by bioluminescent ATP assay. Six replicate experiments were performed for each lens and strain.


RESULTS
Adhesion of all species of bacteria to standard HEMA contact lenses (Etafilcon A) was found to be significantly lower than that of three types of silicone-hydrogel contact lenses, whereas Lotrafilcon B material showed the highest level of bacterial binding. Differences between species in the overall level of adhesion to the different types of contact lenses were observed. Adhesion of P. aeruginosa was typically at least 20 times greater than that observed with both S. epidermidis strains.


CONCLUSIONS
Conventional hydrogel contact lenses exhibit significantly lower bacterial adhesion in vitro than silicone-hydrogel ones. This could be due to the greater hydrophobicity but also to the higher oxygen transmissibility of silicone-hydrogel lenses.
Kodjikian
Laurent
L
Department of Ophthalmology, Croix-Rousse University Hospital, 103, Grande rue de la Croix-Rousse, Lyon, France. kodjikian.laurent@wanadoo.fr
Casoli-Bergeron
Emmanuelle
E
Malet
Florence
F
Janin-Manificat
Hélène
H
Freney
Jean
J
Burillon
Carole
C
Colin
Joseph
J
Steghens
Jean-Paul
JP
D001422:Bacterial Adhesion / Q000502:physiology*; D001672:Biocompatible Materials; D015169:Colony Count, Microbial; D003263:Contact Lenses, Hydrophilic / Q000382:microbiology*; D006801:Humans; D020100:Hydrogels; D008163:Luminescent Measurements; D008689:Methacrylates; D011550:Pseudomonas aeruginosa / Q000502:physiology*; D012826:Silicone Elastomers; D012828:Silicones; D013212:Staphylococcus epidermidis / Q000502:physiology*
D001672:Biocompatible Materials; D020100:Hydrogels; D008689:Methacrylates; D012826:Silicone Elastomers; D012828:Silicones; C114176:etafilcon; C524582:lotrafilcon B