Resistance of Acanthamoeba Cysts to Disinfection in Multiple Contact Lens Solutions

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.Acanthamoebae, which are free-living amoebae, occur worldwide in soil and water. It has been isolated from ponds, lakes, brackish water. and seawater; filters of heating, ventilating, and air-conditioning units; medical equipment, such as gastric wash tubing, dental irrigation units, contact lenses, and contact lens solutions; as well as vegetables, cell cultures, and even human and animal tissues (7,23,39). It has also been isolated from toxic waste dumpsites with high levels of pesticides, herbicides, pharmaceuticals, heavy metals, and polychlorinated biphenyls (35). Acanthamoeba species have two stages in their life cycle: a vegetative or trophozoite stage that reproduces by binary fission and that feeds voraciously on the bacteria and detritus present in the environment and a nondividing, cyst stage that is resistant to environmental stress. Acanthamoeba amoebae cause different types of human disease, including central nervous system infections (granulomatous amebic encephalitis, cutaneous infections) Acanthamoeba dermatitis, and ocular infections (Acanthamoeba keratitis [AK]). Granulomatous amebic encephalitis and cutaneous infections principally occur in immunocompromised individuals, including patients with human immunodeficiency virus infection or AIDS (17,23,37,43). In contrast, AK principally occurs in immunocompetent individuals.

Resistance of Acanthamoeba Cysts to Disinfection Treatments Used in Health Care Settings

“…Conversely, a hydrogen peroxide-based product, despite having lower concentrations of peroxide (2%), showed greater efficacy (P Ͻ 0.001). Differences in the cysticidal activities of lens care solutions containing 3% hydrogen peroxide have already been demonstrated (26), thus highlighting the critical importance of nonactive ingredients, notably surfactants, for the microbicidal activities of formulations. The same remark applies to peracetic acid alone compared to peracetic acid in formulation: two strains resisted very well exposure to 0.2% PAA alone for 10 min, whereas only one strain showed slight resistance after exposure to STERIS-20 for 10 min at 55°C (identical PAA concentration; recommended contact time, 12 min).…”

“…Their potential role as vehicles for various pathogenic microbial species and their intrinsic resistance to high-level disinfectants highlight the need to better evaluate and understand the actions of these treatments against these Trojan horses of the microbial world (6). Standardized procedures for determining the efficacies of contact lens solutions are under investigation by various working groups (26); such procedures should also be investigated for testing the disinfection treatments used for other purposes.…”

Use of 5-Cyano-2,3-Ditolyl-Tetrazolium Chloride Staining as an Indicator of Biocidal Activity in a Rapid Assay for Anti-Acanthamoeba Agents

“…Conventional culture-dependent methods have been used to evaluate the effectiveness of various disinfectants against Acan- thamoeba (1,2,11,12,15,20,24). Among these, methods using the MPN method or the Spearman-Karber method have been considered suitable methods to quantify the number of living organisms (1,18,24) because they are simple, reliable, and reproducible for standardized efficacy tests (1,18).…”

Kerentanan Acanthamoeba spp. terhadap Larutan Disinfektan Pelbagai Guna Kanta Sentuh

“…Acanthamoeba boleh menyebabkan pelbagai jenis penyakit, antaranya Granulamatous Amoebic Encephalitis (GAE), cutaneous acanthamoebiasis dan Keratitis Acanthamoeba (AK) (Johnston et al 2009;Rocha-Azevedo et al 2009). Menurut kajian Kamel dan Norazah (1995), kes pertama keratitis Acanthamoeba yang berlaku di Malaysia telah dilaporkan pada tahun 1995.…”

“…Renu® fresh™ mempunyai bahan aktif DYMED (polyaminopropyl biguanide) 0.0001%. Dalam satu kajian lepas, tiada perbezaan statistik yang signifikan pada aktiviti anti-Acanthamoeba larutan Bausch & Lomb ReNu MultiPlus terhadap A. castellani, A. hatchetti dan A. polyphaga (Johnston et al 2009). …”