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Susceptibility of Acanthamoeba to soft contact lens disinfection systems
Abstract:
Members of the genus Acanthamoeba are increasingly recognized as agents of indolent, chronic, infectious keratitis. Recently, Acanthamoeba corneal infection has been reported in some persons who wear soft contact lenses. In this study, three "heat" and three "cold" soft contact lens disinfection systems were tested according to the manufacturers' instructions against Acanthamoeba castellanii and Acanthamoeba polyphaga in separate trials, and with appropriate controls. Suspensions of Acanthamoeba cysts or trophozoites of each species were tested individually. Each of the three heat disinfection units killed all acanthamoebae in one cycle in all trials. A chlorhexidine 0.005%/thimerosal 0.001% solution killed A. castellanii trophozoites and cysts, but those of A. polyphaga survived. Trophozoites and cysts of both species survived an alkyl triethanol ammonium chloride 0.013%/thimerosal 0.002% solution and a hydrogen peroxide 3% preparation. Heat disinfection overall appears to be more effective in killing Acanthamoeba trophozoites and cysts as compared to cold disinfection methods.
Insights
Heat disinfection effectively kills Acanthamoeba (a cause of infectious keratitis) in soft contact lenses. Cold disinfection methods were less effective against Acanthamoeba castellanii and Acanthamoeba polyphaga.
Area of Science:
- Ophthalmology
- Microbiology
- Infectious Diseases
Background:
- Acanthamoeba infections cause chronic keratitis, particularly in soft contact lens wearers.
- The genus Acanthamoeba is increasingly recognized as a pathogen in ocular infections.
Purpose of the Study:
- To compare the efficacy of heat and cold soft contact lens disinfection systems against Acanthamoeba species.
- To determine the effectiveness of specific disinfection solutions against Acanthamoeba cysts and trophozoites.
Main Methods:
- Three heat and three cold soft contact lens disinfection systems were tested against Acanthamoeba castellanii and Acanthamoeba polyphaga.
- Disinfection systems were used according to manufacturer instructions, with Acanthamoeba cysts and trophozoites tested individually.
- Control groups were used to validate experimental results.
Main Results:
- All three heat disinfection systems eradicated Acanthamoeba cysts and trophozoites in a single cycle.
- A chlorhexidine/thimerosal solution eliminated Acanthamoeba castellanii but not Acanthamoeba polyphaga.
- Alkyl triethanol ammonium chloride/thimerosal and 3% hydrogen peroxide solutions failed to kill Acanthamoeba trophozoites and cysts.
Conclusions:
- Heat disinfection is superior to cold disinfection methods for eliminating Acanthamoeba from soft contact lenses.
- Certain cold disinfection solutions demonstrate limited efficacy against Acanthamoeba species, posing a potential risk to contact lens wearers.