Bacterial adhesion to surface hydrophilic and hydrophobic contact lenses

The aim of this paper was to determine the adhesion of two physico-chemical ly characterized bacterial strains to a surface hydrophilic (CL A, water co ntact angle 57 degrees) and hydrophobic (CL B, water contact angle 106 degr ees) hydrogel contact lens (CL) with and without an adsorbed tear film in a parallel plate flow chamber. Hydrophobicity (by water contact angles), cha rge (by particulate microelectrophoresis) and elemental composition (by XPS ) of the surfaces of seven bacterial strains were characterized, after whic h two strains were selected for further studies. On CL surfaces, hydrophobi city, elemental composition, and mean surface roughness (by AFM) were deter mined, as well as the protein composition of tear films adsorbed on these l enses (by sodium dodecylsulphatepolyacrylamide gel electrophoresis (SDS-PAG E)). Bacterial cell surfaces were relatively uncharged and water contact an gles on lawns of different strains ranged from hydrophobic to hydrophilic. After adsorption of tear film components, N/C elemental surface concentrati ons increased on CL A and CL B and differences in water contact angles betw een both lenses reduced to range from 57 degrees (CL A) to 69 degrees (CL B ). However, different protein compositions were inferred. The surface rough ness of CL A increased from 4 to 13 nm, while it remained 16 nm for CL B. A dhesion of hydrophobic Pseudomonas aeruginosa #3 was more extensive than of hydrophilic Staphylococcus aureus 799, with no differences between both le nses. The hydrophobicity of P. aeruginosa #3 after cell surface damage decr eased and its adhesion was reduced on CL A and strongly on CL B. In additio n, passage of an air-liquid interface yielded more detachment of S. aureus 799 than of P. aeruginosa #3 from the CL surfaces. In conclusion, the hydro phobicity of CL surfaces dictates the composition of the adsorbed tear film and therewith plays an important role in bacterial adhesion to lenses. Adh esion of hydrophobic P. aeruginosa #3 was more tenacious than of hydrophili c S. aureus 799. (C) 2001 Elsevier Science Ltd. All rights reserved.