The effect of concurrent pseudomonas or xanthomonas exposure on adherence of acanthamoeba castellanii to soft contact lenses

Abstract

• Background: Approximately 85% of Acanthamoeba-contaminated contact lens systems in asymptomatic patients have concurrent bacterial contamination. Pseudomonas aeruginosa and Xanthomonas maltophilia are common contect lens contaminants; we investigated the effect of coincubation of Acanthamoeba adherence to contact lenses. • Methods: A. castellanii, 1 × 10⁵ organisms/ml, was coincubated with P. aeruginosa or X. maltophilia, 1 × 10⁸ CFU/ml in phosphate-buffered saline. Sterile, unworn polymacon, etafilcon A or lidofilcon contact lens were investigated. The experimental groups were: (I) lenses exposed to bacteria for 1 h, then Acanthamoeba for 2 h; (II) lenses exposed concurrently to bacteria and Acanthamoeba for 2 h; (III) Acanthamoeba coincubated with bacteria for 24 h, then lenses exposed for 2 h; (IV) lenses exposed to Acanthamoeba for 2 h (control). • Results: For all experimental groups, Acanthamoeba adherence was greater to lidofilcon than to polymacon and etafilcon. For both P. aeruginosa and X. maltophilia, neither group I nor group II displayed greater Acanthamoeba adherence than group IV. Group III exhibited significantly less adherence than group IV for lidofilcon and polymacon. The decrease in group III adherence reflected an overall decrease in Acanthamoeba trophozoite concentration.

• Conclusion: Short bacteria/Acanthamoeba coincubation times did not result in increased Acanthamoeba adherence. Twenty-four-hour coincubation resulted in decreased adherence for Pseudomonas and unchanged adherence rates for Xanthomonas. This model suggests that Pseudomonas or Xanthomonas co-contamination does not necessarily facilitate quantitative Acanthamoeba contact lens adherence.