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Alantary N, Heaselgrave W, Hau S. Correlation of ex vivo and in vivo confocal microscopy imaging of Acanthamoeba. Br J Ophthalmol 2023; 107:1757-1762. [PMID: 35750477 DOI: 10.1136/bjophthalmol-2022-321402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 06/02/2022] [Indexed: 11/03/2022]
Abstract
BACKGROUND/AIMS The aim of this study was to correlate the various forms of Acanthamoeba on ex vivo confocal microscopy (EVCM) with in vivo confocal microscopy (IVCM) and findings from cultured positive cases of Acanthamoeba keratitis. METHODS Acanthamoeba live, dead and empty cysts, and live trophozoites were prepared in vitro and inoculated into porcine cornea using a sterile 26-gauge needle and examined ex vivo using the Heidelberg Retina Tomograph II/Rostock Corneal Module. IVCM images from 12 cultured positive Acanthamoeba cases, obtained using the same instrument, were compared with EVCM findings. Phase contrast images were also obtained to compare with both EVCM and IVCM findings. The change in cyst morphology with depth was evaluated by imaging the same cysts over a defined cornea depth measurement. RESULTS EVCM morphologies for live cysts included four main types-hyper-reflective central dot with hyper-reflective outer ring, hyper-reflective central dot with hyporeflective outer region, stellate shaped hyper-reflective centre with hyporeflective outer region and hyper-reflective round/polygonal shaped cyst; one main type for dead cysts-hyper-reflective central dot with hyporeflective outer region; two main types for empty cysts- hyper-reflective central dot with hyper-reflective outer ring/hyporeflective outer region; and one main type for trophozoites-large coarse speckled area of heterogeneous hyper-reflective material. Matching IVCM images show good correlation with EVCM. Cyst morphology altered when imaged at different depths. CONCLUSION EVCM demonstrated the various forms of Acanthamoeba cyst and trophozoites can be used as a reference to identify similar structures on IVCM.
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Affiliation(s)
- Noor Alantary
- Dept Biomedical Science, University of Wolverhampton Faculty of Science and Engineering, Wolverhampton, UK
- Aston Medical School, Aston University, Birmingham, UK
| | - Wayne Heaselgrave
- Dept Biomedical Science, University of Wolverhampton Faculty of Science and Engineering, Wolverhampton, UK
| | - Scott Hau
- External Disease, Moorfields Eye Hospital, London, UK
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2
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Lindsay RG, Watters G, Johnson R, Ormonde SE, Snibson GR. Acanthamoeba keratitis and contact lens wear. Clin Exp Optom 2021; 90:351-60. [PMID: 17697181 DOI: 10.1111/j.1444-0938.2007.00172.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Acanthamoeba keratitis is a rare but serious complication of contact lens wear that may cause severe visual loss. The clinical picture is usually characterised by severe pain, sometimes disproportionate to the signs, with an early superficial keratitis that is often misdiagnosed as herpes simplex virus (HSV) keratitis. Advanced stages of the infection are usually characterised by central corneal epithelial loss and marked stromal opacification with subsequent loss of vision. In this paper, six cases of contact lens-related Acanthamoeba keratitis that occurred in Australia and New Zealand over a three-year period are described. Three of the patients were disposable soft lens wearers, two were hybrid lens wearers and one was a rigid gas permeable lens wearer. For all six cases, the risk factors for Acanthamoeba keratitis were contact lens wear with inappropriate or ineffective lens maintenance and exposure of the contact lenses to tap or other sources of water. All six patients responded well to medical therapy that involved topical use of appropriate therapeutic agents, most commonly polyhexamethylene biguanide and propamidine isethionate, although two of the patients also subsequently underwent deep lamellar keratoplasty due to residual corneal surface irregularity and stromal scarring. Despite the significant advances that have been made in the medical therapy of Acanthamoeba keratitis over the past 10 years, prevention remains the best treatment and patients who wear contact lenses must be thoroughly educated about the proper use and care of the lenses. In particular, exposure of the contact lenses to tap water or other sources of water should be avoided.
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Affiliation(s)
- Richard G Lindsay
- Department of Optometry and Vision Sciences, The University of Melbourne, Melbourne, Australia.
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3
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Crary MJ, Walters R, Shannon P, Gabriel MM. Variables Affecting the Recovery of Acanthamoeba Trophozoites. Pathogens 2021; 10:221. [PMID: 33670669 PMCID: PMC7922685 DOI: 10.3390/pathogens10020221] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/15/2021] [Accepted: 02/16/2021] [Indexed: 11/28/2022] Open
Abstract
While the results of Acanthamoeba testing have been extensively published, laboratories conducting such testing are left to develop their own methods in the absence of a standardized methodology. The wide disparity of methods has resulted in equally inconsistent reported results for contact lens care (CLC) products. This study's objective was to determine the source of these discrepancies by evaluating basic Acanthamoeba biology and their impact on antimicrobial efficacy testing, including the ability of a recovery method to stimulate a single trophozoite to proliferate. Antimicrobial efficacy testing was conducted using well-published Acanthamoeba strains, storage conditions, and growth-based recovery methods. To identify variables that influence results, test solutions with low Acanthamoeba disinfection rates were utilized to prevent differences from being masked by high log reductions. In addition, single-cell proliferation assays were executed to understand the growth requirements to stimulate trophozoite propagation in two recovery methods. These studies indicated that both nutrient density (>106 CFU) and the length of plate incubation (at least 14 days) could significantly influence the accurate recovery of trophozoites. Together, this study emphasizes the need to understand how Acanthamoeba trophozoites biology can impact test methods to create divergent results.
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Affiliation(s)
- Monica J. Crary
- R&D Microbiology, Alcon Research, LLC, Fort Worth, TX 76134, USA; (R.W.); (P.S.); (M.M.G.)
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Mohd Hussain RH, Afiqah WN, Abdul Ghani MK, Khan NA, Siddiqui R, Anuar TS. In vitro effects of multi-purpose contact lens disinfecting solutions towards survivability of Acanthamoeba genotype T4 in Malaysia. Saudi J Biol Sci 2021; 28:2352-2359. [PMID: 33911949 PMCID: PMC8071914 DOI: 10.1016/j.sjbs.2021.01.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 01/09/2021] [Accepted: 01/12/2021] [Indexed: 12/05/2022] Open
Abstract
The incidence of Acanthamoeba keratitis has been increasing since the previous decades, especially among contact lens users. This infection is majorly caused by the use of ineffective contact lens disinfecting solution. Thus, this study was conducted to evaluate the in vitro effects of multi-purpose disinfecting solutions (MPDS) against Acanthamoeba trophozoites and cysts. Acanthamoeba genotype T4 isolated from contact lens paraphernalia and an environmental strains were propagated for trophozoite or cyst-containing culture and adjusted in final concentration of 1 × 105 cells/ml. Amoebicidal and cysticidal assays were conducted by incubating trophozoites and cysts with OPTI-FREE® Express®, ReNu® Fresh™, Complete® Multi-Purpose Solution and AVIZOR Unica® Sensitive according to the manufacturer’s minimum recommended disinfectant time (MMRDT) for up to 12 h at 30 ⁰C. Trypan blue hemocytometer-based microscopic counts determined amoebicidal and cysticidal effects. The viability of Acanthamoeba trophozoites and cysts was confirmed by re-inoculated them in the 1.5% non-nutrient agar plates. It was found that none of the MPDS showed amoebicidal and cysticidal effects during the MMRDT. However, OPTI-FREE® Express® demonstrated a significant differences in average cell reduction for both stages within MMRDT. When subjected to 12 h exposure, both OPTI-FREE® Express® and ReNu® Fresh™ led to significant reduction in the number of trophozoite and cyst cells. Notably, Complete® Multi-Purpose Solution and AVIZOR Unica® Sensitive did appreciably improve the solution effectiveness towards trophozoite cells when incubated for 12 h. All MPDS were largely ineffective, with 100% survival of all isolates at MMRDT, while OPTI-FREE® Express® showed limited amoebicidal activity against the contact lens paraphernalia isolate, however, it was more against the environmental strains after 12 h incubation time. The commercially available MPDS employed in this research offered minimal effectiveness against the protozoa despite the contact time. Improvement or development of new solution should consider the adjustment of the appropriate disinfectant concentration, adequate exposure time or the incorporation of novel chemical elements, which are effective against Acanthamoeba for accelerated disinfecting and more reduction of potential exposure of contact lens users to Acanthamoeba keratitis.
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Affiliation(s)
- Rosnani Hanim Mohd Hussain
- Centre of Medical Laboratory Technology, Faculty of Health Sciences, Universiti Teknologi MARA, Puncak Alam Campus, Selangor, Malaysia
| | - Wan Nur Afiqah
- Centre of Medical Laboratory Technology, Faculty of Health Sciences, Universiti Teknologi MARA, Puncak Alam Campus, Selangor, Malaysia
| | - Mohamed Kamel Abdul Ghani
- Programme of Biomedical Sciences, School of Diagnostic and Applied Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, Kuala Lumpur, Malaysia
| | - Naveed Ahmed Khan
- Department of Clinical Sciences, College of Medicine, University of Sharjah, University City, Sharjah, United Arab Emirates
| | - Ruqaiyyah Siddiqui
- Department of Biology, Chemistry and Environmental Sciences, College of Arts and Sciences, American University of Sharjah, University City, Sharjah, United Arab Emirates
| | - Tengku Shahrul Anuar
- Centre of Medical Laboratory Technology, Faculty of Health Sciences, Universiti Teknologi MARA, Puncak Alam Campus, Selangor, Malaysia.,Integrative Pharmacogenomics Institute, Universiti Teknologi MARA, Puncak Alam Campus, Selangor, Malaysia
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Impact of Acanthamoeba Cysts on Stress Resistance of Salmonella enterica Serovar Typhimurium, Yersinia enterocolitica 4/O:3, Listeria monocytogenes 1/2a, and Escherichia coli O:26. Appl Environ Microbiol 2017; 83:AEM.00754-17. [PMID: 28526786 DOI: 10.1128/aem.00754-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 05/09/2017] [Indexed: 01/06/2023] Open
Abstract
The formation of robust resting cysts enables Acanthamoeba to resist harsh environmental conditions. This study investigated to what extent these cysts are resistant to physical and chemical stresses as applied in food industry cleaning and disinfection procedures. Moreover, it was assessed whether certain intracystic meat-borne bacterial pathogens are more stress resistant than free-living bacterial monocultures and if intracystic passage and subsequent association with trophozoites induces cross-tolerance toward other stressors. Several physical and chemical stressors (NaCl, H2O2, benzalkonium chloride, 55°C, heating until boiling, ethanol, dishwashing detergent, and sodium hypochlorite) frequently used in domestic and industrial food-related environments were tested against (i) Acanthamoeba castellanii cysts, (ii) single strains of bacterial monocultures, (iii) intracystic bacteria, and (iv) bacteria after intracystic passage (cyst-primed bacteria). Only heating until boiling and hypochlorite treatment were cysticidal. After boiling, no viable trophozoites could be recovered from the cysts, and hypochlorite treatment caused a 1.34- to 4.72-log10 cells/ml reduction in cyst viability. All treatments were effective in reducing or even eliminating the tested bacterial monocultures, whereas bacteria residing inside cysts were more tolerant toward these stressors. All cyst-primed bacteria exhibited an increased tolerance toward subsequent H2O2 (>92% decrease in median log10 CFU/ml reduction) and 70% ethanol (>99% decrease) treatments. Moreover, intracystic passage significantly increased the survival of Yersinia enterocolitica (74% decrease in median log10 reduction), Escherichia coli (58%), and Salmonella enterica (48%) after NaCl treatment and of E. coli (96%), S. enterica (99%), and Listeria monocytogenes (99%) after sodium hypochlorite treatment compared with that of nonprimed bacteria.IMPORTANCE The results from this study demonstrated that both viable and nonviable amoebal cysts can protect internalized bacteria against stressful conditions. Moreover, cyst passage can induce cross-tolerance in bacteria, increasing their survival when exposed to selected stressors. These findings underscore the potential importance of free-living amoebae in food-related environments and their impact on the persistence of meat-borne bacterial pathogens.
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Asiedu-Gyekye IJ, Mahmood AS, Awortwe C, Nyarko AK. Toxicological assessment of polyhexamethylene biguanide for water treatment. Interdiscip Toxicol 2015; 8:193-202. [PMID: 27486381 PMCID: PMC4961918 DOI: 10.1515/intox-2015-0029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 08/28/2015] [Accepted: 09/10/2015] [Indexed: 02/05/2023] Open
Abstract
Polyhexamethylene biguanide (PHMB) is an antiseptic with antiviral and antibacterial properties used in a variety of products including wound care dressings, contact lens cleaning solutions, perioperative cleansing products, and swimming pool cleaners. There are regulatory concerns with regard to its safety in humans for water treatment. We decided to assess the safety of this chemical in Sprague-Dawley rats. PHMB was administered in a single dose by gavage via a stomach tube as per the manufacturer's instruction within a dose range of 2 mg/kg to 40 mg/kg. Subchronic toxicity studies were also conducted at doses of 2 mg/kg, 8 mg/kg and 32 mg/kg body weight and hematological, biochemical and histopathological findings of the major organs were assessed. Administration of a dose of 25.6 mg/kg, i.e. 1.6 mL of 0.4% PHMB solution (equivalent to 6.4x10(3) mg/L of 0.1% solution) resulted in 50% mortality. Histopathological analysis in the acute toxicity studies showed that no histopathological lesions were observed in the heart and kidney samples but 30% of the animals had mild hydropic changes in zone 1 of their liver samples, while at a dosage of 32 mg/kg in the subchronic toxicity studies, 50% of the animals showed either mild hepatocyte cytolysis with or without lymphocyte infiltration and feathery degeneration. Lymphocyte infiltration was, for the first time, observed in one heart sample, whereas one kidney sample showed mild tubular damage. The acute studies showed that the median lethal dose (LD50) is 25.6 mg/kg (LC50 of 1.6 mL of 0.4% PHMB. Subchronic toxicological studies also revealed few deleterious effects on the internal organs examined, as seen from the results of the biochemical parameters evaluated. These results have implications for the use of PHMB to make water potable.
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Affiliation(s)
- Isaac J Asiedu-Gyekye
- Department of Pharmacology and Toxicology, University of Ghana School of Pharmacy, College of Health Sciences, Legon, Ghana
| | - Abdulai Seidu Mahmood
- Department of Pathology, School of Biomedical and Allied Health Sciences, College of Health Sciences, Korle-Bu, Ghana
| | - Charles Awortwe
- Division of Pharmacology, Faculty of Health Sciences, University of Stellenbosch, Cape Town, South Africa
| | - Alexander K Nyarko
- Department of Pharmacology and Toxicology, University of Ghana School of Pharmacy, College of Health Sciences, Legon, Ghana
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7
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Veríssimo CDM, Maschio VJ, Correa APF, Brandelli A, Rott MB. Infection in a rat model reactivates attenuated virulence after long-term axenic culture of Acanthamoeba spp. Mem Inst Oswaldo Cruz 2015; 108:832-5. [PMID: 24271042 PMCID: PMC3970641 DOI: 10.1590/0074-0276130099] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Accepted: 03/26/2013] [Indexed: 11/22/2022] Open
Abstract
Prolonged culturing of many microorganisms leads to the loss of virulence and a reduction of their infective capacity. However, little is known about the changes in the pathogenic strains of Acanthamoeba after long culture periods. Our study evaluated the effect of prolonged culturing on the invasiveness of different isolates of Acanthamoeba in an in vivo rat model. ATCC strains of Acanthamoeba, isolates from the environment and clinical cases were evaluated. The in vivo model was effective in establishing the infection and differentiating the pathogenicity of the isolates and re-isolates. The amoebae cultured in the laboratory for long periods were less virulent than those that were recently isolated, confirming the importance of passing Acanthamoeba strains in animal models.
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Fouque E, Yefimova M, Trouilhé MC, Quellard N, Fernandez B, Rodier MH, Thomas V, Humeau P, Héchard Y. Morphological Study of the Encystment and Excystment of Vermamoeba vermiformis
Revealed Original Traits. J Eukaryot Microbiol 2014; 62:327-37. [DOI: 10.1111/jeu.12185] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 08/19/2014] [Accepted: 08/25/2014] [Indexed: 11/30/2022]
Affiliation(s)
- Emilie Fouque
- Université de Poitiers; UMR CNRS 7267; Ecologie et Biologie des Interactions (EBI); 1 rue G. Bonnet 86073 Poitiers Cedex France
- Sechenov Institute of Evolutionary Physiology and Biochemistry; Russian Academy of Sciences; 194223 Saint-Petersburg Russia
| | - Marina Yefimova
- Université de Poitiers; ERL 7368 CNRS; Signalisation et Transports Ioniques Membranaires (STIM); 1 rue G. Bonnet 86073 Poitiers Cedex France
- Sechenov Institute of Evolutionary Physiology and Biochemistry; Russian Academy of Sciences; 194223 Saint-Petersburg Russia
| | - Marie-Cécile Trouilhé
- Scientific and Technical Center for Building; AQUASIM; 11 rue Henri Picherit BP 82341 44323 Nantes Cedex 3 France
| | - Nathalie Quellard
- Université de Poitiers; Service d'Anatomie et Cytologie Pathologiques; CHU de Poitiers; 2 rue de la Milétrie 86000 Poitiers France
| | - Béatrice Fernandez
- Université de Poitiers; Service d'Anatomie et Cytologie Pathologiques; CHU de Poitiers; 2 rue de la Milétrie 86000 Poitiers France
| | - Marie-Hélène Rodier
- Université de Poitiers; UMR CNRS 7267; Ecologie et Biologie des Interactions (EBI); 1 rue G. Bonnet 86073 Poitiers Cedex France
| | | | - Philippe Humeau
- Scientific and Technical Center for Building; AQUASIM; 11 rue Henri Picherit BP 82341 44323 Nantes Cedex 3 France
| | - Yann Héchard
- Université de Poitiers; UMR CNRS 7267; Ecologie et Biologie des Interactions (EBI); 1 rue G. Bonnet 86073 Poitiers Cedex France
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Padzik M, Chomicz L, Szaflik JP, Chruścikowska A, Perkowski K, Szaflik J. In vitro effects of selected contact lens care solutions on Acanthamoeba castellanii strains in Poland. Exp Parasitol 2014; 145 Suppl:S98-S101. [PMID: 24967738 DOI: 10.1016/j.exppara.2014.06.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 06/02/2014] [Accepted: 06/12/2014] [Indexed: 11/27/2022]
Abstract
Free-living, cosmopolitan amoebae of the Acanthamoeba genus may be the causative agents of Acanthamoeba keratitis (AK) - a progressive, vision-threatening infection of the human cornea described particularly among contact lens wearers. Use of contact lens care solutions, effective against these organisms, is important in preventing AK infections. 3 different strains of Acanthamoeba castellanii of the T4 genotype (Neff strain and two others, isolated from patients with AK) were exposed to 4 selected multipurpose contact lens care solutions available in Poland: Ciba Vision AoSept Plus, Bausch & Lomb ReNu MultiPlus, Alcon Opti-Free, Ciba Vision Solo Care Aqua. No amoebicidal effect was observed. The strongest amoebostatic effect was visible after 24h of exposition to Opti-Free and ReNu solution and associated with percentage increase of rounded, motionless forms. This is significantly longer than minimum disinfection time recommended by manufacturers of all tested multipurpose solutions. Surprisingly, no clear induction of the encystation process was observed.
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Affiliation(s)
- Marcin Padzik
- Department of Medical Biology, Medical University of Warsaw, 73 Nowogrodzka Str., 02-018 Warsaw, Poland.
| | - Lidia Chomicz
- Department of Medical Biology, Medical University of Warsaw, 73 Nowogrodzka Str., 02-018 Warsaw, Poland
| | - Jacek P Szaflik
- Department of Ophthalmology, SPKSO Ophthalmic Hospital, Medical University of Warsaw, 13 Sierakowskiego Str., 03-709 Warsaw, Poland
| | - Agnieszka Chruścikowska
- Department of Medical Biology, Medical University of Warsaw, 73 Nowogrodzka Str., 02-018 Warsaw, Poland
| | - Konrad Perkowski
- Department of Orthodontics, Medical University of Warsaw, 59 Nowogrodzka Str., 02-005 Warsaw, Poland
| | - Jerzy Szaflik
- Department of Ophthalmology, SPKSO Ophthalmic Hospital, Medical University of Warsaw, 13 Sierakowskiego Str., 03-709 Warsaw, Poland
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Fouque E, Trouilhé MC, Thomas V, Humeau P, Héchard Y. Encystment of Vermamoeba (Hartmannella) vermiformis: Effects of environmental conditions and cell concentration. Exp Parasitol 2014; 145 Suppl:S62-8. [PMID: 24721257 DOI: 10.1016/j.exppara.2014.03.029] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Revised: 03/24/2014] [Accepted: 03/31/2014] [Indexed: 11/28/2022]
Abstract
Vermamoeba vermiformis is a free-living amoeba (FLA) which is widely distributed in the environment. It is known to colonize water systems and to be a reservoir of pathogenic bacteria, such as Legionella pneumophila. For these reasons the control of V. vermiformis represents an important health issue. However, FLA may be resistant to disinfection treatments due to the process of encystment. Thereby, it is important to better understand factors influencing this process. In this aim, we investigated the effect of temperature, pH, osmotic pressure and cell concentration on the encystment of two V. vermiformis strains. Encystment was quite fast, with a 100% encystment rate being observed after 9h of incubation. For the two strains, an optimal encystment was obtained at 25 and 37°C. Concerning pH and osmotic pressure, there were different effects on the encystment according to the tested strains. For the reference strain (ATCC 50237), the patterns of encystment were similar for pH comprised between 5 and 9 and for KCl concentrations ranging from 0.05 to 0.2 mol L(-1). For the environmental strain (172A) an optimal encystment was obtained for basic pH (8 and 9) and for a concentration in KCl of 0.1 mol L(-1). The results also clearly demonstrated that the encystment rate increased with cell concentration, suggesting that there is an inter-amoebal communication. The present study establish for the first time environmental conditions favoring encystment and would lay the foundations to better control the encystment of V. vermiformis.
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Affiliation(s)
- Emilie Fouque
- Université de Poitiers, UMR CNRS 7267, Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, 1 rue G. Bonnet, 86073 Poitiers Cedex, France; Scientific and Technical Center for Building, AQUASIM, 11 rue Henri Picherit, BP 82341, 44323 Nantes Cedex 3, France
| | - Marie-Cécile Trouilhé
- Scientific and Technical Center for Building, AQUASIM, 11 rue Henri Picherit, BP 82341, 44323 Nantes Cedex 3, France
| | - Vincent Thomas
- Enterome, 94-96 Avenue Ledru Rollin, 75011 Paris, France
| | - Philippe Humeau
- Scientific and Technical Center for Building, AQUASIM, 11 rue Henri Picherit, BP 82341, 44323 Nantes Cedex 3, France
| | - Yann Héchard
- Université de Poitiers, UMR CNRS 7267, Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, 1 rue G. Bonnet, 86073 Poitiers Cedex, France.
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11
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Goudot S, Herbelin P, Mathieu L, Soreau S, Banas S, Jorand F. Biocidal efficacy of monochloramine against planktonic and biofilm-associated Naegleria fowleri
cells. J Appl Microbiol 2014; 116:1055-65. [DOI: 10.1111/jam.12429] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 12/17/2013] [Accepted: 12/30/2013] [Indexed: 11/30/2022]
Affiliation(s)
- S. Goudot
- EDF Recherche et Développement; Laboratoire National d'Hydraulique et Environnement; Chatou Cedex France
- Université de Lorraine; LCPME; UMR 7564 CNRS - UL; Institut Jean Barriol; Villers-lès-Nancy France
- CNRS; LCPME; UMR 7564 CNRS - UL; Villers-lès-Nancy France
| | - P. Herbelin
- EDF Recherche et Développement; Laboratoire National d'Hydraulique et Environnement; Chatou Cedex France
| | - L. Mathieu
- CNRS; LCPME; UMR 7564 CNRS - UL; Villers-lès-Nancy France
- Ecole Pratique des Hautes Etudes (EPHE); LCPME; UMR 7564 CNRS-UL; Vandoeuvre-lès-Nancy France
| | - S. Soreau
- EDF Recherche et Développement; Laboratoire National d'Hydraulique et Environnement; Chatou Cedex France
| | - S. Banas
- Université de Lorraine; LCPME; UMR 7564 CNRS - UL; Institut Jean Barriol; Villers-lès-Nancy France
- CNRS; LCPME; UMR 7564 CNRS - UL; Villers-lès-Nancy France
| | - F.P.A. Jorand
- Université de Lorraine; LCPME; UMR 7564 CNRS - UL; Institut Jean Barriol; Villers-lès-Nancy France
- CNRS; LCPME; UMR 7564 CNRS - UL; Villers-lès-Nancy France
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12
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Dupuy M, Berne F, Herbelin P, Binet M, Berthelot N, Rodier MH, Soreau S, Héchard Y. Sensitivity of free-living amoeba trophozoites and cysts to water disinfectants. Int J Hyg Environ Health 2013; 217:335-9. [PMID: 23932411 DOI: 10.1016/j.ijheh.2013.07.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 07/10/2013] [Accepted: 07/11/2013] [Indexed: 11/26/2022]
Abstract
Free-living amoebae are naturally present in water. These protozoa could be pathogenic and could also shelter pathogenic bacteria. Thus, they are described as a potential hazard for health. Also, free-living amoebae have been described to be resistant to biocides, especially under their cyst resistant form. There are several studies on amoeba treatments but none of them compare sensitivity of trophozoites and cysts from different genus to various water disinfectants. In our study, we tested chlorine, monochloramine and chlorine dioxide on both cysts and trophozoites from three strains, belonging to the three main genera of free-living amoebae. The results show that, comparing cysts to trophozoites inactivation, only the Acanthamoeba cysts were highly more resistant to treatment than trophozoites. Comparison of the disinfectant efficiency led to conclude that chlorine dioxide was the most efficient treatment in our conditions and was particularly efficient against cysts. In conclusion, our results would help to adapt water treatments in order to target free-living amoebae in water networks.
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Affiliation(s)
- Mathieu Dupuy
- Université de Poitiers, Laboratoire Ecologie et Biologie des Interactions, CNRS UMR 7267, 1 rue Georges Bonnet, 86022 Poitiers Cedex, France
| | - Florence Berne
- Université de Poitiers, IC2MP, CNRS UMR 7285, 1 rue Marcel Doré, 86022 Poitiers Cedex, France
| | - Pascaline Herbelin
- EDF, Division Recherche et Développement, 6 Quai Watier, 78401 Chatou, France
| | - Marie Binet
- EDF, Division Recherche et Développement, 6 Quai Watier, 78401 Chatou, France
| | - Nelsie Berthelot
- VERI, Veolia Environnement, Chemin de la digue BP76, 78603 Maisons Laffitte Cedex, France
| | - Marie-Hélène Rodier
- Université de Poitiers, Laboratoire Ecologie et Biologie des Interactions, CNRS UMR 7267, 1 rue Georges Bonnet, 86022 Poitiers Cedex, France
| | - Sylvie Soreau
- EDF, Division Recherche et Développement, 6 Quai Watier, 78401 Chatou, France
| | - Yann Héchard
- Université de Poitiers, Laboratoire Ecologie et Biologie des Interactions, CNRS UMR 7267, 1 rue Georges Bonnet, 86022 Poitiers Cedex, France.
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Potential resistant morphotypes of Acanthamoeba castellanii expressed in multipurpose contact lens disinfection systems. Eye Contact Lens 2013; 38:400-5. [PMID: 22858984 DOI: 10.1097/icl.0b013e318261ab1f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES The free-living amoeba Acanthamoeba castellanii is a rare cause of contact lens-associated microbial keratitis. The cyst stage of this amoeba is noted for its resistance to disinfection by multipurpose contact lens solutions (MPS). This report examines and reviews the potential survival modes of A. castellanii in MPS. METHODS Trophozoites of A. castellanii (ATCC 30234) at densities from 10 to near 10 were incubated in 3 different MPS in a laminar flow hood for 24 hours at ambient temperatures. The dried films of MPS and phosphate-buffered saline (PBS) controls were examined before and after the addition of a peptone-yeast extract-glucose recovery broth (PYG) for the presence of amoeboid trophozoites and resistance stages over at least 7 days. The parallel exposure of trophozoites to MPS without evaporation or addition of PYG was similarly examined. RESULTS Amoeboid trophozoites were not recovered in PYG nor were cyst-like structures observed in any MPS with near 10 densities. Progressively with 10 to 10 trophozoites, varied survival modes, particularly aggregates of trophozoites associated with cyst-like structures and occasional amoeboid forms and double-walled cysts with ostioles, became more evident. These morphotypes were most prominent after evaporation and typically first observed in the PYG. CONCLUSIONS Trophozoites of A. castellanii near 10 and progressively to 10 densities are capable of expressing a variety of "short-term" survival modes in MPS, notably with the added stress of evaporation. Expression of these alternate survival modes in MPS may relate, in part, to contamination of contact lens cases and difficulties in developing standardized MPS efficacy tests.
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Abstract
PURPOSE To compare the traditional manual hemacytometer method and an automated counter (Vi-cell) to enumerate and distinguish between viable and non-viable amoeba, and to determine the efficacies of contact lens (CL) disinfecting solutions against three species of Acanthamoeba. The efficacies in the presence of a bacterial food source and bovine serum albumin (BSA) were investigated. METHODS Four brands of multipurpose solutions and a hydrogen peroxide disinfecting system (Oxysept) for soft CLs, and four disinfecting solutions for Rigid Gas Permeable (RGP) lenses were tested against three species of Acanthamoeba. Page's amoebic saline was included as a negative control and standard solutions of disinfecting agents, 6% hydrogen peroxide and 0.5% chlorhexidine, as positive controls. The effects of the presence of Pseudomonas aeruginosa and BSA on effectiveness were assessed. RESULTS None of the CL solutions tested achieved a 1-log reduction in viability of all three Acanthamoeba species within the manufacturer's recommended disinfection times. The presence of P. aeruginosa did not significantly affect disinfecting capacity of multipurpose solution solutions but reduced activity of RGP solutions and the hydrogen peroxide system. BSA reduced trophozoicidal activity of all solutions. Bland and Altman analysis showed good agreement between Vi-cell and hemacytometer. CONCLUSIONS The Vi-Cell analyzer offers a simple and effective method of determining amoebicidal activity. Our results show that the CL solutions tested could not satisfactorily kill Acanthamoeba.
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Vaerewijck MJM, Sabbe K, Baré J, Spengler HP, Favoreel HW, Houf K. Assessment of the efficacy of benzalkonium chloride and sodium hypochlorite against Acanthamoeba polyphaga and Tetrahymena spp. J Food Prot 2012; 75:541-6. [PMID: 22410229 DOI: 10.4315/0362-028x.jfp-11-359] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The efficacy of benzalkonium chloride and sodium hypochlorite against Acanthamoeba polyphaga and two Tetrahymena spp. was determined based on the European Standard EN 1276:2009 suspension test. Trophozoite viability was assessed by determination of the membrane integrity using flow cytometry as a fast screening technique. Bovine serum albumin was added to simulate clean (0.3 g/liter) and dirty (3 g/liter) conditions. Benzalkonium chloride caused cell lysis at concentrations above 50 mg/liter under clean and dirty conditions. A concentration of 50 mg of free chlorine per liter had a strong biocidal effect on acanthamoebae and tetrahymenae after 15 min under clean and dirty conditions. Our results suggest that benzalkonium chloride and sodium hypochlorite were effective against the three microorganisms at concentrations commonly applied in the food industry.
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Affiliation(s)
- M J M Vaerewijck
- Department of Veterinary Public Health and Food Safety, Ghent University, Merelbeke, Belgium
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Coulon C, Dechamps N, Meylheuc T, Collignon A, McDonnell G, Thomas V. The effect of in vitro growth conditions on the resistance of Acanthamoeba cysts. J Eukaryot Microbiol 2012; 59:198-205. [PMID: 22353167 DOI: 10.1111/j.1550-7408.2012.00612.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Accepted: 12/19/2011] [Indexed: 11/29/2022]
Abstract
Despite increasing concerns of direct pathogenicity and/or their role as hosts for other microorganisms there are currently no standard methods for the inactivation of amoebae that belong to the genus Acanthamoeba. Methods used to grow amoebae and produce cysts for these tests may be important as they can dramatically modify cyst susceptibility. We compared resistance of cysts produced from trophozoites grown in peptone-yeast extract-glucose broth or by feeding on HEp-2 cells and then encysted in Neff's medium. We observed that trophozoites grown using HEp-2 cells as a nutrient source produce cysts that are significantly more resistant to SDS and to most biocides tested, including heat. Increased resistance is likely due to a higher proportion of mature cysts presenting thicker cell walls as demonstrated using transmission electron microscopy. This was confirmed by calcofluor white staining demonstrating higher cellulose content in cysts produced from trophozoites grown using HEp-2 cells as a feeding source. These results demonstrate that not only methods used to produce cysts from trophozoites are critical, but that methods used to grow trophozoites before encystment should also be chosen carefully. This should be taken into account for the development of protocols to evaluate biocides and antimicrobials against amoebal cysts.
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Kobayashi T, Gibbon L, Mito T, Shiraishi A, Uno T, Ohashi Y. Efficacy of commercial soft contact lens disinfectant solutions against Acanthamoeba. Jpn J Ophthalmol 2011; 55:547-557. [DOI: 10.1007/s10384-011-0062-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2010] [Accepted: 04/19/2011] [Indexed: 10/18/2022]
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Kilvington S, Powell CH, Lam A, Lonnen J. Antimicrobial efficacy of multi-purpose contact lens disinfectant solutions following evaporation. Cont Lens Anterior Eye 2011; 34:183-7. [PMID: 21393050 DOI: 10.1016/j.clae.2011.02.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 02/10/2011] [Accepted: 02/10/2011] [Indexed: 11/26/2022]
Abstract
PURPOSE Non-compliance is a significant factor in contact lens related microbial keratitis and includes solution reuse and failure to recap the lens storage case resulting in evaporation effects. To address this, impact of partial evaporation on the antimicrobial efficacy of multipurpose contact lens care solutions was investigated. METHODS Solutions were evaporated under a stream of air to 2× and 4× concentration and challenged with Fusarium solani (ATCC 36031), Candida albicans (ATCC 10231) and Acanthamoeba castellanii (ATCC 50370). The level of organism kill at 6h was compared to the non-evaporated product. RESULTS ReNu with MoistureLoc(®) (RML) lost 90-100% of biocidal activity against C. albicans on evaporation, 75-99% for F. solani and 29-33% with A. castellanii at 2× or 4× concentration, respectively. OPTI-FREE(®) RepleniSH(®) lost 72-90% efficacy against C. albicans and F. solani, and 61% at 2× and 10% at 4× concentration with A. castellanii. ReNu(®) MultiPlus, AQuify(®) Multi-Purpose and Biotrue™ showed only loss in efficacy with C. albicans at 4× concentration giving 79%, 34.5% and 48% reduction, respectively. No loss in biocidal activity on evaporation was obtained with Complete(®) Revitalens for all organisms. CONCLUSION Partial evaporation can affect biocidal efficacy of multi-purpose solutions and may have been a significant factor in an outbreak of Fusarium keratitis cases associated with RML. Evaporation results in increased binding of cationic disinfectants to counter-ions in the formulation, reducing ability to attach and rupture anionic microbial cell walls. Interaction may also occur between the biocidal ingredient and other components, such as surfactants, resulting in sequestration of activity through micelle formation.
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Reindel W, Cairns G, Merchea M. Assessment of patient and practitioner satisfaction with Biotrue™ multi-purpose solution for contact lenses. Cont Lens Anterior Eye 2010; 33 Suppl 1:S12-7. [DOI: 10.1016/j.clae.2010.06.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Revised: 04/24/2010] [Accepted: 06/11/2010] [Indexed: 10/18/2022]
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Mycobacterium avium infections of Acanthamoeba strains: host strain variability, grazing-acquired infections, and altered dynamics of inactivation with monochloramine. Appl Environ Microbiol 2010; 76:6685-8. [PMID: 20709834 DOI: 10.1128/aem.00644-10] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Stable Mycobacterium avium infections of several Acanthamoeba strains were characterized by increased infection resistance of recent environmental isolates and reduced infectivity in the presence of other bacteria. Exposure of M. avium in coculture with Acanthamoeba castellanii to monochloramine yielded inactivation kinetics markedly similar to those observed for A. castellanii alone.
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Coulon C, Collignon A, McDonnell G, Thomas V. Resistance of Acanthamoeba cysts to disinfection treatments used in health care settings. J Clin Microbiol 2010; 48:2689-97. [PMID: 20519477 PMCID: PMC2916629 DOI: 10.1128/jcm.00309-10] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 05/14/2010] [Accepted: 05/21/2010] [Indexed: 11/20/2022] Open
Abstract
Free-living amoebae that belong to the genus Acanthamoeba are widespread in the environment, including water. They are responsible for human infections and can host pathogenic microorganisms. Under unfavorable conditions, they form cysts with high levels of resistance to disinfection methods, thus potentially representing a threat to public health. In the present study we evaluated the efficacies of various biocides against trophozoites and cysts of several Acanthamoeba strains. We demonstrated that disinfectant efficacy varied depending on the strains tested, with environmental strains demonstrating greater resistance than collection strains. Trophozoites were inactivated by all treatments except those using glutaraldehyde as an active compound: for these treatments, we observed resistance even after 30 min exposure. Cysts resisted many treatments, including certain conditions with glutaraldehyde and other biocides. Moist heat at 55 degrees C was not efficient against cysts, whereas exposure at 65 degrees C was. Several chemical formulations containing peracetic acid, hydrogen peroxide, or ortho-phthalaldehyde presented greater efficacy than glutaraldehyde, as did ethanol and sodium hypochlorite; however, some of these treatments required relatively long incubation times to achieve cyst inactivation. Amoebal cysts can be highly resistant to some high-level disinfectants, which has implications for clinical practice. These results highlight the need to consider the effective disinfection of protozoa in their vegetative and resistant forms due to their intrinsic resistance. This is important not only to prevent the transmission of protozoa themselves but also due to the risks associated with a range of microbial pathogens that are found to be associated intracellularly with these microorganisms.
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Affiliation(s)
- Céline Coulon
- STERIS SA R&D, Fontenay-aux-Roses, France, Université de Paris-Sud XI, Faculté de Pharmacie, Département de Microbiologie, Châtenay-Malabry, France, STERIS Ltd., Basingstoke, United Kingdom
| | - Anne Collignon
- STERIS SA R&D, Fontenay-aux-Roses, France, Université de Paris-Sud XI, Faculté de Pharmacie, Département de Microbiologie, Châtenay-Malabry, France, STERIS Ltd., Basingstoke, United Kingdom
| | - Gerald McDonnell
- STERIS SA R&D, Fontenay-aux-Roses, France, Université de Paris-Sud XI, Faculté de Pharmacie, Département de Microbiologie, Châtenay-Malabry, France, STERIS Ltd., Basingstoke, United Kingdom
| | - Vincent Thomas
- STERIS SA R&D, Fontenay-aux-Roses, France, Université de Paris-Sud XI, Faculté de Pharmacie, Département de Microbiologie, Châtenay-Malabry, France, STERIS Ltd., Basingstoke, United Kingdom
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Kilvington S, Huang L, Kao E, Powell CH. Development of a new contact lens multipurpose solution: Comparative analysis of microbiological, biological and clinical performance. JOURNAL OF OPTOMETRY 2010; 3:134-142. [PMCID: PMC3974296 DOI: 10.1016/s1888-4296(10)70019-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Accepted: 06/09/2010] [Indexed: 06/10/2023]
Abstract
Purpose Antimicrobial, cytotoxicity and clinical performance of a new soft contact lens multi-purpose solution (COMPLETE® RevitaLens) based on polyquaternium-1 and alexidine dihydrochloride (NuMPS) was evaluated. Methods Antimicrobial efficacy was assessed according to ISO 14729 for both biocidal and regimen performance against bacteria and fungi. Acanthamoeba efficacy was tested along with ability to retain antimicrobial activity on partial evaporation. In vitro cytotoxicity of NuMPS and OPTI-FREE® RepleniSH® MPS (MPS-3) was assessed based on ISO 10993-5 and United States Pharmacopeia (USP) methods. In addition, a 3 month, double-masked, parallel group clinical trial comparing safety and acceptability with respect to MPS-3 was conducted with 4 silicone hydrogel (SiHy) and FDA Group IV lens types. Results NuMPS showed broad antimicrobial efficacy, including Acanthamoeba, giving a 3–4 log10 reduction in viability after 6 hours contact time. NuMPS also passed ISO 14729 regimens with SiHy and etafilcon lenses for bacteria, fungi and also Acanthamoeba. The cytotoxicity of NuMPS was equivalent or better compared to MPS-3. In the clinical trial, there was no statistically significant between-group difference in corneal staining (p > 0.05). Patients using MPS-3 had more adverse events than patients using NuMPS: 11.8 % (11/93) versus 2.8 % (5/177), respectively, (p < 0.05). There were no differences noted in cleanliness or wearing comfort (p > 0.05). Conclusion Taken together, the results of these studies indicate that the NuMPS is a novel and effective soft contact lens care solution.
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Affiliation(s)
- Simon Kilvington
- Corresponding author: Abbott Medical Optics Inc. 1700 E. St. Andrew Place, Santa Ana, CA 92705-4933, USA. Phone: +1 (714) 247 8254 Fax: +1 (714) 247 8673.
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The disinfection efficacy of MeniCare soft multipurpose solution against Acanthamoeba and viruses using stand-alone biocidal and regimen testing. Eye Contact Lens 2010; 36:90-5. [PMID: 20107417 DOI: 10.1097/icl.0b013e3181d13c2d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To assess the disinfection efficacy of MeniCare Soft contact lens multipurpose solution against Acanthamoeba and viruses in suspension and when inoculated on to contact lenses and subjected to rub-and-rinse or no-rub-and-rinse care regimes. METHODS MeniCare Soft was challenged with Acanthamoeba spp trophozoites or cysts, herpes simplex virus (type 1), adenovirus (type 8), and poliovirus (type 2) and the log reduction in Acanthamoeba viability and viral infectivity determined over time. In addition, contact lenses were incubated with Acanthamoeba and viruses and the number of viable organisms determined after the lenses were processed using rub-and-rinse or no-rub-and-rinse care regimes followed by a 4 hr soaking time. RESULTS MeniCare Soft showed >3 log reduction against Acanthamoeba spp trophozoites and cysts after 6 hr exposure. Approximately 1 log reduction was found against the 3 viruses after 4 hr exposure. No surviving Acanthamoeba trophozoites or cysts were recovered from any of the contact lens tested when MeniCare Soft was used in a rub-and-rinse or no-rub-and-rinse care regimes (>5.0 log reduction). Rub-and-rinse regimen resulted in a 4.5 to 5.0 log reduction in viruses compared with 3.7 to 5.2 log when no-rub-and-rinse was used. CONCLUSIONS MeniCare Soft showed effective disinfection efficacy against Acanthamoeba trophozoites and cysts using solution and regimen assays. The viruses were more resistant to disinfection in solution but were removed effectively from contact lenses using a rub-and-rinse or no-rub-and-rinse care regimen.
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Thomas V, McDonnell G, Denyer SP, Maillard JY. Free-living amoebae and their intracellular pathogenic microorganisms: risks for water quality. FEMS Microbiol Rev 2010; 34:231-59. [DOI: 10.1111/j.1574-6976.2009.00190.x] [Citation(s) in RCA: 208] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Koehsler M, Leitsch D, Duchêne M, Nagl M, Walochnik J. Acanthamoeba castellanii : growth on human cell layers reactivates attenuated properties after prolonged axenic culture. FEMS Microbiol Lett 2009; 299:121-7. [PMID: 19732153 PMCID: PMC2810444 DOI: 10.1111/j.1574-6968.2009.01680.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The free-living, but potentially pathogenic, bacteriovorous amoebae of the genus Acanthamoeba can be easily grown axenically in a laboratory culture. This, however, often leads to considerable losses in virulence, and encystment capacity, and to changes in drug susceptibility. We evaluated potential options for a reactivation of a number of physiological properties, attenuated by prolonged axenic laboratory culture, including encystment potential, protease activity, heat resistance, growth rates and drug susceptibility against N-chlorotaurine (NCT). Toward this end, a strain that had been grown axenically for 10 years was repeatedly passaged on human HEp-2 cell monolayers or treated with 5′-azacytidine (AzaC), a methyltransferase inhibitor, and trichostatin A (TSA), a histone deacetylase inhibitor, in order to uplift epigenetic gene regulation. Culture on human cell monolayers resulted in significantly enhanced encystment potentials and protease activities, and higher susceptibility against NCT, whereas the resistance against heat shock was not altered. Treatment with AzaC/TSA resulted in increased encystment rates and protease activities, indicating the participation of epigenetic mechanisms. However, lowered resistances against heat shock indicate that possible stress responses to AzaC/TSA have to be taken into account. Repeated growth on human cell monolayers appears to be a potential method to reactivate attenuated characteristics in Acanthamoeba.
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Affiliation(s)
- Martina Koehsler
- Department of Medical Parasitology, Clinical Institute of Hygiene and Medical Microbiology, Medical University of Vienna, Kinderspitalgasse 15, Vienna, Austria
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Resistance of Acanthamoeba cysts to disinfection in multiple contact lens solutions. J Clin Microbiol 2009; 47:2040-5. [PMID: 19403771 DOI: 10.1128/jcm.00575-09] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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.
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Acanthamoeba: a review of its potential to cause keratitis, current lens care solution disinfection standards and methodologies, and strategies to reduce patient risk. Eye Contact Lens 2009; 34:247-53. [PMID: 18779663 DOI: 10.1097/icl.0b013e31817e7d83] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND The recent outbreaks of Acanthamoeba keratitis (AK), a rare but serious infection of the cornea, has increased the attention on the pathology of the organism and safety standards as they relate to soft contact lens (SCL) disinfection and solution formulations. OBJECTIVE To review the pathologic potential of Acanthamoeba to produce keratitis in patients at risk, discuss the complex issues involved in Acanthamoeba SCL disinfection efficacy standards and testing methods, and present strategies for patients as well as governmental agencies to reduce the risk for future outbreaks of this organism. METHODS Studies that investigated the pathology and occurrence of AK and the various methods for testing SCL disinfection products for efficacy against Acanthamoeba were reviewed and the results were summarized. RESULTS.: Acanthamoeba is a ubiquitous organism in nature and has pathogenic and nonpathogenic strains. Trophozoites--not cysts--bind to specific mannosylated proteins on the corneal surface abraded by SCL wear. These bound trophozoites produce a cytotoxic serine protease enzyme that destroys corneal integrity and provides the mechanism for Acanthamoeba to produce keratitis. To date, nowhere in the world are Acanthamoeba challenges included in product approval of SCL disinfection products. Nonstandardized microbiologic methods for SCL disinfection efficacy against Acanthamoeba continue to produce highly variable data from study to study. There are no detailed and standardized methods as yet for trophozoite cell culture, trophozoite-to-cyst conversion, product challenge with amoeba, neutralization of the test sample's antimicrobial activity, and accurate quantification of viable survivor cells. CONCLUSIONS Reducing the incidence of AK is multifaceted and includes education of SCL wearers in the hygienic wear and care of their lenses, implementation of standardized and rigorous SCL solution disinfection requirements, and can also include improvements in the antimicrobial quality of municipal water supplies.
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Encystment of Acanthamoeba During Incubation in Multipurpose Contact Lens Disinfectant Solutions and Experimental Formulations. Eye Contact Lens 2008; 34:133-9. [DOI: 10.1097/icl.0b013e3181772c95] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Sökmen M, Değerli S, Aslan A. Photocatalytic disinfection of Giardia intestinalis and Acanthamoeba castellani cysts in water. Exp Parasitol 2008; 119:44-8. [DOI: 10.1016/j.exppara.2007.12.014] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Revised: 12/13/2007] [Accepted: 12/17/2007] [Indexed: 10/22/2022]
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Acanthamoeba strains lose their abilities to encyst synchronously upon prolonged axenic culture. Parasitol Res 2008; 102:1069-72. [PMID: 18247052 DOI: 10.1007/s00436-008-0885-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Accepted: 01/11/2008] [Indexed: 10/22/2022]
Abstract
To evaluate the influence of prolonged axenic culture on the encystment capacity of Acanthamoeba spp., the encystment potential of four closely related Acanthamoeba strains, subcultured axenically for different periods of time, was evaluated comparing five encystment media. Media with more alkaline pH values were slightly more effective; however, the composition of the respective encystment medium had only limited influence on the encystment potential, while a strong correlation of losses in encystment potential and times strains had been cultured axenically was demonstrated. Furthermore, our results indicate that losses in encystment potential occur shortly after transfer into axenic culture to remain constant over many years.
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Abstract
PURPOSE Acanthamoeba castellani, ATCC 30234, cysts, and trophozoites after a 6-hour exposure. METHODS Trophozoite cultures were prepared at Bio-Concept Laboratories in vented tissue culture flasks containing peptone yeast glucose broth by incubation (35 degrees C +/- 1 degrees C for 11 days). Cyst suspensions were prepared by incubation of trophozoites in phosphate-buffered saline plus heat-killed yeast on Page's saline agar plates (35 degrees C +/- 1 degrees C for 14 days). The solutions were inoculated in triplicate in respective lens cases. After the 6-hour exposure, aliquots of challenged solutions were transferred to Dey-Engley neutralizing broth and further diluted in peptone yeast glucose broth in tissue culture plates to the -7 dilution. Flasks and plates were incubated for 14 days at 35 degrees C +/- 1 degrees C and were examined with an inverted light microscope at day 14 for the presence of viable trophozoites. The most probable number method was used for approximate enumeration of the number of survivors. RESULTS Mean log reductions for cysts were 1.8 for Clear Care/AOSEPT Plus, 2.0 for BLUE Vision/BLUE SEPT, 0.7 for Oxysept 1 Step, 0.5 for OPTI-FREE Express with Aldox, and 0.2 for easyvision one step+. Mean log reductions for trophozoites were 2.2 for Clear Care/AOSEPT Plus, 2.7 for BLUE Vision/BLUE SEPT, 2.5 for Oxysept 1 Step, 2.5 for OPTI-FREE Express with Aldox, and 1.8 for easyvision one step+. CONCLUSIONS Only Clear Care/AOSEPT Plus and BLUE Vision/BLUE SEPT showed high levels of antimicrobial activity against the cyst form of A. castellani. Oxysept 1 Step showed mild activity against the cysts and easyvision one step+ and OPTI-FREE Express with Aldox showed virtually no antiacanthamoeba activity against the cyst form after 6 hours of exposure.
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Thomas V, McDonnell G. Relationship between mycobacteria and amoebae: ecological and epidemiological concerns. Lett Appl Microbiol 2007; 45:349-57. [PMID: 17897376 DOI: 10.1111/j.1472-765x.2007.02206.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Since the discovery that Legionella pneumophila can survive and grow within free-living amoebae, there has been an increasing number of microbial species shown to have similar relationships. These include many bacterial species, fungi, other protozoa (e.g. Cryptosporidium) and viruses. Among bacteria, mycobacteria are of particular importance because of their role in human and animal infections. This review will consider the progress made in understanding the relationships between mycobacteria and amoebae, and their consequences in terms of ecology and epidemiology.
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Affiliation(s)
- V Thomas
- STERIS Laboratory, CEA/DSV/IMETI/SEPIA, 18 route du Panorama, 92260 Fontenay-aux-Roses, France.
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Heaselgrave W, Patel N, Kilvington S, Kehoe SC, McGuigan KG. Solar disinfection of poliovirus and Acanthamoeba polyphaga cysts in water – a laboratory study using simulated sunlight. Lett Appl Microbiol 2006; 43:125-30. [PMID: 16869893 DOI: 10.1111/j.1472-765x.2006.01940.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS To determine the efficacy of solar disinfection (SODIS) in disinfecting water contaminated with poliovirus and Acanthamoeba polyphaga cysts. METHODS AND RESULTS Organisms were subjected to a simulated global solar irradiance of 850 Wm(-2) in water temperatures between 25 and 55 degrees C. SODIS at 25 degrees C totally inactivated poliovirus after 6-h exposure (reduction of 4.4 log units). No SODIS-induced reduction in A. polyphaga cyst viability was observed for sample temperatures below 45 degrees C. Total cyst inactivation was only observed after 6-h SODIS exposure at 50 degrees C (3.6 log unit reduction) and after 4 h at 55 degrees C (3.3 log unit reduction). CONCLUSIONS SODIS is an effective means of disinfecting water contaminated with poliovirus and A. polyphaga cysts, provided water temperatures of 50-55 degrees C are attained in the latter case. SIGNIFICANCE AND IMPACT OF THE STUDY This research presents the first SODIS inactivation curve for poliovirus and provides further evidence that batch SODIS provides effective protection against waterborne protozoan cysts.
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Affiliation(s)
- W Heaselgrave
- Department of Infection, Immunity and Inflammation, School of Medicine, University of Leicester, UK
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Vasseneix C, Gargala G, François A, Hellot MF, Duclos C, Muraine M, Benichou J, Ballet JJ, Brasseur G, Favennec L. A Keratitis Rat Model for Evaluation of Anti-Acanthamoeba Polyphaga Agents. Cornea 2006; 25:597-602. [PMID: 16783150 DOI: 10.1097/01.ico.0000214213.37447.11] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To develop a rat model of chronic Acanthamoeba polyphaga keratitis suitable for pharmacologic assessment of therapeutic agents. METHODS An A. polyphaga isolate (ATCC #50495) was grown in peptone-yeast extract-glucose medium. Five-weeks-old, Sprague-Dawley male rats were injected with 10(3) or 10(4) trophozoites in the left cornea stromal layer. A subconjunctival injection of 0.14, 0.28, or 0.57 mg long-acting betamethasone was performed weekly. At the end of experiments, rats were killed; the superficial corneal epithelium gently scraped and cultured; and globes histologically examined. Topical polyhexamethylene biguanide (PHMB), hexamidine diisethionate, and miltefosine (hexadecylphosphocholine) were administered topically as eye drops 3 times a day at concentrations of 0.02%, 0.1%, and 0.01% respectively. In vitro minimal inhibitory concentration (MIC) and fractional inhibitory concentration values were measured in A. polyphaga cultures. RESULTS In infected eyes, lesions consisted of the sequential appearance within 2 weeks of edema, infiltrates, and/or abscesses. On day 35 postinfection, a combination of 10(4) parasites with a regimen of 0.28 mg/week betamethasone resulted in the highest ratio of rats with abscesses. Presence of A. polyphaga was confirmed histologically and inconsistently in cultures. In rats optimally prepared as said earlier, agents were administered on day 6 postinfection. A combination of PHMB and hexamidine diisethionate exerted a synergistic effect and was more effective than PHMB, hexamidine diisethionate, or miltefosine alone. In vitro, PHMB (MIC = 14.6 microM) and hexamidine diisethionate (MIC = 555 microM) exerted a synergistic effect (fractional inhibitory concentration = 0.06), and miltefosine exhibited antiamoebal activity (MIC = 27.4 microM). CONCLUSIONS In this study, a rat model of chronic A. polyphaga keratitis was obtained and found suitable for assessment of pharmacologic agents. It provides an in vivo approach of drug resistance, pathogenicity, and physiopathologic mechanisms of chronic amoebic keratitis.
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Affiliation(s)
- Caroline Vasseneix
- Laboratoire de Parasitologie, ADEN EA-3234, CHU Charles Nicolle, Rouen, France
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Borazjani RN, Kilvington S. Efficacy of multipurpose solutions against Acanthamoeba species. Cont Lens Anterior Eye 2005; 28:169-75. [PMID: 16332501 DOI: 10.1016/j.clae.2005.10.001] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2005] [Revised: 08/18/2005] [Accepted: 10/23/2005] [Indexed: 10/25/2022]
Abstract
AIM The disinfection efficacy of contact lens multipurpose solutions (MPSs) against Acanthamoeba polyphaga (Ros) and Acanthamoeba castellanii (ATCC30868) cysts and trophozoites was determined by both biocidal and manufacturer-recommended no-rub/rinse regimen testing. METHODS A biocidal assay using four MPSs (ReNu with MoistureLoc, Opti-free Express, Solo-care Plus, and Complete MoisturePlus) was conducted with or without the presence of organic soil. A second test procedure compared the ability of five MPSs (ReNu with MoistureLoc MPS, ReNu MultiPlus, Opti-free Express, Solo-care Aqua, and Complete MoisturePlus) to remove and kill Acanthamoeba species cysts and trophozoites from SofLens 38 and Surevue conventional hydrogel lenses, and Focus Night & Day silicone hydrogel lenses using the manufacturer-recommended regimen. RESULTS In the biocidal assay, only ReNu with MoistureLoc successfully killed both trophozoites and cysts (>3 log) within the manufacturer-recommended soak time. A >3 log decrease in trophozoites, but not cysts, was reported for Opti-free Express; however, Solo-care Plus and Complete MoisturePlus did not reduce the number of cysts or trophozoites by >3 log during the manufacturer-recommended soak time. In the no-rub/rinse regimen tests, only ReNu with MoistureLoc removed an inoculum of 2 x 10(5) trophozoites or cysts from SofLens 38 and Surevue hydrogel lenses, as well as Focus Night & Day silicone hydrogel lenses. Less than 10 viable organisms were recovered from the lenses after the 10s rinse and 4h soak. Opti-free Express, Solo-care Aqua, and ReNu MultiPlus were effective at removing trophozoites and cysts from SofLens 38 and Surevue conventional hydrogel lenses, but not from Focus Night & Day silicone hydrogel lenses. In excess of 10 viable organisms were recovered from all lenses after the manufacturer-recommended regimen using Complete MoisturePlus. CONCLUSIONS These data suggest that some MPSs, when used as recommended by the manufacturer, are more effective at killing representative strains of Acanthamoeba than others.
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Affiliation(s)
- R N Borazjani
- Research Group, Bausch & Lomb, 1400 N Goodman Street, Rochester, NY 14609, USA.
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Abstract
PURPOSE To compare the amoebicidal activity of two commercially available multipurpose contact lens care systems, by using cyst and trophozoite growth of two strains each of Acanthamoeba castellanii and Acanthamoeba polyphaga. METHODS Trophozoites and cysts of Acanthamoeba species, isolated from corneal ulcers and an ATCC strain, were exposed to two commonly used multipurpose solutions and a saline control for 4 or 6 hours at ambient temperature. After neutralization of the disinfecting solution, track forming units were enumerated on Escherichia coli-seeded nutrient agar plates. RESULTS There were significant differences (P<0.01) between solutions, strains, and cysts or trophozoites, but not between the different periods. Solution 2, containing polyquaternium-1 and myristamidopropyl dimethylamine (among other ingredients), gave greater mean log reductions than did solution 1, containing polyaminopropyl biguanide and poloxamine (among other ingredients). Both solutions generally reduced more trophozoites than cysts. CONCLUSIONS The multipurpose solution containing polyquaternium-1 and myristamidopropyl dimethylamine reduced more cysts and trophozoites than did the alternative solution tested. Because there were differences in the effect of the multipurpose solutions on strains, it is recommended that more than one strain or species of Acanthamoeba be tested to determine efficacy of disinfecting solutions. The lack of difference between disinfection times may indicate that 4 hours could be considered as an adequate disinfecting time to ensure sufficient kill of Acanthamoeba species.
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Affiliation(s)
- Sally L Buck
- Alcon Research, Ltd., Fort Worth, TX 76134, USA.
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Lonnen J, Kilvington S, Kehoe SC, Al-Touati F, McGuigan KG. Solar and photocatalytic disinfection of protozoan, fungal and bacterial microbes in drinking water. WATER RESEARCH 2005; 39:877-883. [PMID: 15743634 DOI: 10.1016/j.watres.2004.11.023] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2003] [Revised: 09/16/2004] [Accepted: 11/17/2004] [Indexed: 05/24/2023]
Abstract
The ability of solar disinfection (SODIS) and solar photocatalytic (TiO(2)) disinfection (SPC-DIS) batch-process reactors to inactivate waterborne protozoan, fungal and bacterial microbes was evaluated. After 8 h simulated solar exposure (870 W/m(2) in the 300 nm-10 microm range, 200 W/m(2) in the 300-400 nm UV range), both SPC-DIS and SODIS achieved at least a 4 log unit reduction in viability against protozoa (the trophozoite stage of Acanthamoeba polyphaga), fungi (Candida albicans, Fusarium solani) and bacteria (Pseudomonas aeruginosa, Escherichia coli). A reduction of only 1.7 log units was recorded for spores of Bacillus subtilis. Both SODIS and SPC-DIS were ineffective against the cyst stage of A. polyphaga.
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Affiliation(s)
- J Lonnen
- Department of Infection, Immunity & Inflammation, Maurice Shock Building, School of Medicine, University of Leicester, Leicester LE1 9HN, UK
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Borazjani RN, Kilvington S. Effect of a Multipurpose Contact Lens Solution on the Survival and Binding of Acanthamoeba Species on Contact Lenses Examined With a No-Rub Regimen. Eye Contact Lens 2005; 31:39-45. [PMID: 15665671 DOI: 10.1097/01.icl.0000146303.00326.69] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To determine the effect of a multipurpose contact lens solution (ReNu MultiPlus Multi-Purpose Solution [RMP]) on the relative survival and binding of trophozoites and cysts of Acanthamoeba on hydrogel lenses with a no-rub regimen. METHODS A stand-alone test procedure with RMP was conducted with and without the presence of organic soil (1 x 10(7) colony-forming units/mL heat-killed cells of Saccharomyces cerevisiae in heat-inactivated fetal bovine serum). Survival of amoebae on hydrogel contact lenses exposed to RMP was determined with a no-rub care regimen. RESULTS ReNu MultiPlus Multi-Purpose Solution reduced the number of recoverable amoebae by more than 95% within 4 hours of inocula of 10(5) trophozoites and cysts, regardless of the presence or absence of an organic soil. Amoebae, particularly cysts, were readily rinsed from contact lenses, including silicone hydrogels, without rubbing after exposure to RMP. CONCLUSIONS The efficacy of RMP for Acanthamoeba was not appreciably altered in the presence of organic soil in a no-rub protocol. The antimicrobial activity, in part, appeared to be a combination of reducing the capacity for binding of representative Acanthamoeba to the lens by alteration of morphology, often followed by lysis of the amoebae.
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Affiliation(s)
- Roya N Borazjani
- Research, Development & Engineering, Research Group, Bausch & Lomb, Rochester NY 14609, USA.
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Hiti K, Walochnik J, Faschinger C, Haller-Schober EM, Aspöck H. One- and two-step hydrogen peroxide contact lens disinfection solutions against Acanthamoeba: How effective are they? Eye (Lond) 2004; 19:1301-5. [PMID: 15543174 DOI: 10.1038/sj.eye.6701752] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Effective contact lens disinfection solutions are important to keep the storage case free of acanthamoebae and thus prevent an infection of the eye. The aim of our study was to evaluate the effectivity of two new one-step hydrogen peroxide disinfecting solutions against Acanthamoeba spp. and compare it to the effectivity of other commercially available systems. METHODS Nine one-step 3% hydrogen peroxide systems including the new systems Silver Sept (platinum and silver disk for intensifying disinfection) and Blue Vision (newly composed catalytic tablet) and 2 two-step systems (0.6 and 3.0% H(2)O(2)) were tested for their effectivity against cysts of two Acanthamoeba keratitis isolates at different concentrations. RESULTS After a soaking time of 8 h (overnight soaking of contact lenses) the 2 two-step systems completely destroyed the cysts of both Acanthamoeba strains, even at the highest concentration of cysts tested. The nine tested one-step systems showed weaker effects. The new Blue Vision system was able to eradicate the cysts of one strain at the low concentration of cysts. CONCLUSIONS One-step hydrogen peroxide systems do not have sufficient effects on Acanthamoeba cysts and therefore may not protect the contact lens user from a possible infection of the eye. Further development of tablets like the ones used in the Blue Vision system may result in better cysticidal effects for one-step systems.
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Affiliation(s)
- K Hiti
- 1Department of Ophthalmology, University of Graz, Austria
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