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Updated: Jun 23, 2026
Quantification of Acanthamoeba spp. Motility
Published on: September 20, 2024
Resistance of Acanthamoeba cysts to disinfection in multiple contact lens solutions
Stephanie P Johnston1, Rama Sriram, Yvonne Qvarnstrom
1Division of Parasitic Diseases, Centers for Disease Control and Prevention, Public Health Service, US Department of Health and Human Services, Atlanta, GA 30341-3724, USA. sjohnston@cdc.gov
Abstract:
Acanthamoebae are free-living amoebae found in the environment, including soil, freshwater, brackish water, seawater, hot tubs, and Jacuzzis. Acanthamoeba species can cause keratitis, a painful vision-threatening infection of the cornea, and fatal granulomatous encephalitis in humans. More than 20 species of Acanthamoeba belonging to morphological groups I, II, and III distributed in 15 genotypes have been described. Among these, Acanthamoeba castellanii, A. polyphaga, and A. hatchetti are frequently identified as causing Acanthamoeba keratitis (AK). Improper contact lens care and contact with nonsterile water while wearing contact lenses are known risk factors for AK. During a recent multistate outbreak, AK was found to be associated with the use of Advanced Medical Optics Complete MoisturePlus multipurpose contact lens solution, which was hypothesized to have had insufficient anti-Acanthamoeba activity. As part of the investigation of that outbreak, we compared the efficacies of 11 different contact lens solutions against cysts of A. castellanii, A. polyphaga, and A. hatchetti (the isolates of all species were genotype T4), which were isolated in 2007 from specimens obtained during the outbreak investigation. The data, generated with A. castellanii, A. polyphaga, and A. hatchetti cysts, suggest that the two contact lens solutions containing hydrogen peroxide were the only solutions that showed any disinfection ability, with 0% and 66% growth, respectively, being detected with A. castellanii and 0% and 33% growth, respectively, being detected with A. polyphaga. There was no statistically significant difference in disinfection efficacy between the 11 solutions for A. hatchetti.
Insights
Hydrogen peroxide contact lens solutions demonstrated disinfection ability against Acanthamoeba species, crucial for preventing Acanthamoeba keratitis (AK). Other solutions showed limited efficacy, highlighting the need for effective contact lens care to avoid infections.
Area of Science:
- Microbiology
- Ophthalmology
- Infectious Diseases
Background:
- Acanthamoebae are ubiquitous free-living amoebae that can cause severe human infections like Acanthamoeba keratitis (AK) and granulomatous encephalitis.
- Acanthamoeba keratitis is often linked to contact lens wear, improper hygiene, and exposure to contaminated water.
- Specific Acanthamoeba species, including *Acanthamoeba castellanii*, *A. polyphaga*, and *A. hatchetti*, are frequently implicated in AK cases.
Purpose of the Study:
- To evaluate the efficacy of 11 different contact lens solutions against Acanthamoeba species.
- To identify contact lens solutions with effective anti-Acanthamoeba activity, particularly in light of a multistate AK outbreak linked to a specific multipurpose solution.
Main Methods:
- Comparison of 11 contact lens solutions against cysts of *Acanthamoeba castellanii*, *A. polyphaga*, and *A. hatchetti* (all genotype T4).
- Isolates were obtained from specimens during a 2007 multistate outbreak investigation.
- Disinfection efficacy was assessed by measuring cyst growth after exposure to the solutions.
Main Results:
- Only two contact lens solutions containing hydrogen peroxide showed significant disinfection ability against *A. castellanii* and *A. polyphaga* cysts.
- Hydrogen peroxide solutions resulted in 0% and 66% growth for *A. castellanii*, and 0% and 33% growth for *A. polyphaga*.
- No statistically significant difference in disinfection efficacy was observed among the 11 solutions tested against *A. hatchetti* cysts.
Conclusions:
- Hydrogen peroxide-based contact lens solutions appear to be the most effective in controlling Acanthamoeba contamination among the tested products.
- The findings underscore the importance of proper contact lens hygiene and solution selection to prevent sight-threatening Acanthamoeba keratitis.
- Further research may be needed to optimize contact lens solutions for comprehensive Acanthamoeba disinfection.
