Pseudomonas attachment to low-water and high-water, ionic and nonionic, new and rabbit-worn soft contact lenses

The authors determined the attachment of a single strain of Pseudomonas aeruginosa to seven brands of hydrogel soft contact lenses (SCLs): nonionic, low-water (polymacon and crofilcon); nonionic, high-water (lidofilcon); ionic, high-water (bufilcon, etafilcon, and perfilcon); and surface-neutralized, high-water (bufilcon). The lenses were exposed to a 1 X 10(8) colony-forming units (CFU)/ml P. aeruginosa suspension either when new and sterile or after 24 hr of continuous wear in rabbit eyes. Quantitative scanning electron microscopy showed that, regardless of lens type, significantly fewer bacteria attached to worn than to new SCLs (P less than 0.05). The bacterial attachment on new, unworn SCLs was significantly lower (Wilcoxon rank-sum test) (P less than 0.05) on polymacon and crofilcon than on all other lenses tested except perfilcon; on etafilcon than on bufilcon; and on perfilcon than on all SCLs tested except polymacon. The bacterial attachment on rabbit-worn SCLs was significantly lower (P less than 0.05) on polymacon than on all other lenses tested except crofilcon and perfilcon; on crofilcon than on bufilcon; on lidofilcon and on surface-neutralized bufilcon than on crofilcon and perfilcon; on etafilcon than on crofilcon, bufilcon, and perfilcon; and on perfilcon than on crofilcon and bufilcon. The results did not show a consistent relationship between hydration and surface charge and P. aeruginosa adherence. Among the SCLs tested, no one lens had a decisive advantage over another, because all, both new and worn, can bind amounts of P. aeruginosa that could potentially produce bacterial keratitis on predisposed eyes.