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Survival of Acanthamoeba in contact lens rinse solutions
R C Nauheim1, R J Brockman, S S Stopak
1Eye & Ear Institute of Pittsburgh, Department of Ophthalmology, University of Pittsburgh, PA 15213.
Abstract:
Acanthamoeba may cause a severe keratitis in contact lens wearers. Since most sterilization techniques require rinsing the lenses prior to insertion, contaminated solutions represent a potential vector for transmission of Acanthamoeba. The ability of rinse solutions to sustain an inoculum of Acanthamoeba polyphaga was investigated. A. polyphaga was exposed to 0.1% benzalkonium chloride, 0.001% thimerosal/0.1% edetate disodium, 0.1% edetate disodium, saline, tap water, and distilled water. The status of the organism was evaluated with direct microscopic counts and cultures to confirm viability. Incubation with 0.1% edetate disodium, saline, tap water, and distilled water resulted in the maintenance of reduced populations of viable organisms for 7 days. Benzalkonium chloride preserved saline and solutions containing thimerosal with edetate rendered the Acanthamoeba nonviable.
Insights
Contact lens solutions like saline, tap water, and distilled water can sustain viable Acanthamoeba polyphaga. However, benzalkonium chloride and thimerosal-containing solutions effectively kill these organisms, preventing Acanthamoeba keratitis.
Area of Science:
- Ophthalmology
- Microbiology
- Infectious Diseases
Background:
- Acanthamoeba keratitis is a severe eye infection primarily affecting contact lens wearers.
- Contaminated contact lens solutions are a potential transmission route for Acanthamoeba.
- Standard lens care often involves rinsing, increasing reliance on solution efficacy.
Purpose of the Study:
- To investigate the ability of various contact lens rinse solutions to sustain Acanthamoeba polyphaga viability.
- To determine which common solutions can support Acanthamoeba survival.
- To identify effective disinfectants against Acanthamoeba in lens care.
Main Methods:
- Acanthamoeba polyphaga were exposed to different solutions: 0.1% benzalkonium chloride, 0.001% thimerosal/0.1% edetate disodium, 0.1% edetate disodium, saline, tap water, and distilled water.
- Organism viability was assessed using direct microscopic counts and cultures.
- The duration of viability assessment was 7 days.
Main Results:
- Solutions containing 0.1% edetate disodium, saline, tap water, and distilled water maintained reduced populations of viable Acanthamoeba for 7 days.
- 0.1% benzalkonium chloride and solutions with thimerosal and edetate disodium rendered Acanthamoeba nonviable.
- Certain common rinsing solutions fail to eliminate Acanthamoeba, posing a risk.
Conclusions:
- Saline, tap water, and distilled water are inadequate for eliminating Acanthamoeba and may support low-level survival.
- Antimicrobial agents like benzalkonium chloride and thimerosal are crucial for inactivating Acanthamoeba in contact lens solutions.
- Proper disinfection protocols are essential to prevent Acanthamoeba keratitis transmission via contact lens care products.