Microwave treatment of contact lens cases contaminated with acanthamoeba

Recent advances in sterilization and disinfection technology: A review

Sterilization and disinfection of pollutants and microorganisms have been extensively studied in order to address the problem of environmental contamination, which is a crucial issue for public health and economics. Various form of hazardous materials/pollutants including microorganisms and harmful gases are released into the environment that enter into the human body either through inhalation, adsorption or ingestion. The human death rate rises due to various respiratory ailments, strokes, lung cancer, and heart disorders related with these pollutants. Hence, it is essential to control the environmental pollution by applying economical and effective sterilization and disinfections techniques to save life. In general, numerous forms of traditional physical and chemical sterilization and disinfection treatments, such as dry and moist heat, radiation, filtration, ethylene oxide, ozone, hydrogen peroxide, etc. are known along with advanced techniques. In this review we summarized both advanced and conventional techniques of sterilization and disinfection along with their uses and mode of action. This review gives the knowledge about the advantages, disadvantages of both the methods comparatively. Despite, the effective solution given by the advanced sterilization and disinfection technology, joint technologies of sterilization and disinfection has proven to be more effective innovation to protect the indoor and outdoor environments.

Exploring microwave irradiation as a method to disinfect contact lens cases

PURPOSE

Biofilm formation caused by infrequent contact lens case replacement and the ineffectiveness of multi-purpose solutions (MPS) on biofilm removal is associated with high rates of bacterial keratitis infections. This study demonstrated biofilm elimination from the contact lens case by microwave irradiation.

METHODS

Staphylococcus aureus biofilms indicative of 3-9 months of contact wear were cultured in contact lens cases and visualized with crystal violet (CV) staining. Biofilms in contact cases were then exposed to four treatment regimens: No treatment (n = 8), 45 s microwave irradiation (n = 8), tap water (n = 6), and MPS (n = 9). Bacterial survival was assessed by colony forming unit (CFU) assay using streak dilutions.

RESULTS

Visualization of the biofilms through CV staining revealed that biofilms coalesce between ribs of the contact case. In 5/8 cases no CFU were cultivated from the case after treatment with microwave irradiation. In tap water and MPS the first dilution averaged 6 ± 2 and 31 ± 13 CFUs per plate, respectively, while microwave irradiation averaged < 1 CFU per plate. In Dilution 2, the average reduced to 0.7 ± 0.7 and 6 ± 5 CFUs per plate for tap water and MPS, respectively, while microwave irradiation had 0 CFUs in Dilution 2.

CONCLUSION

Biofilms that coalesce between the ribs of the contact case pose a threat because this area is difficult to thoroughly scrub and could act as a basis for infection through fouling of contact lenses. Of the four treatment regimens, microwave irradiation displayed the most consistent and highest rate of bacterial eradication. Tap water was less effective compared to microwave irradiation, and poses other harmful side effects, but greatly reduced CFU count compared to no treatment. MPS displayed the poorest bacterial eradication of the treatments. Thus, microwave irradiation is worth further investigation as a viable in-home disinfecting option.

Inactivation of Acanthamoeba Cysts in Suspension and on Contaminated Contact Lenses Using Non-Thermal Plasma

Water suspensions of cysts of a pathogenic clinical isolate of Acanthamoeba sp. were prepared, and the cysts were inactivated either in suspension or placed on the surface of contact lenses by the non-thermal plasma produced by the DC corona transient spark discharge. The efficacy of this treatment was determined by cultivation and the presence of vegetative trophozoites indicating non-inactivated cysts. The negative discharge appeared to be more effective than the positive one. The complete inactivation occurred in water suspension after 40 min and on contaminated lenses after 50 min of plasma exposure. The properties of lenses seem to not be affected by plasma exposure; that is, their optical power, diameter, curvature, water content and infrared and Raman spectra remain unchanged.

Development and optimization of new culture media for Acanthamoeba spp. (Protozoa: Amoebozoa)

The isolation and growth in axenic liquid media of Acanthamoeba strains is necessary in order to carry out primary in vitro drug screening. Amoebic isolates which are hard to grow in the current liquid media have been reported. Such circumstances hampers the ability of conducting drug sensitivity tests. Therefore, finding suitable universal growth media for Acanthamoeba species is required. The present study was aimed at the development of liquid medium suitable for growing a fastidious (F) genotype T3 Acanthamoeba isolate, and eventually for other genotypes of this genus as well. Trophozoite growth was indirectly monitored by respiration analysis with oxygen-sensitive microplates (OSM) and further confirmed by manual counting. Media were empirically designed and tested first in a non-fastidious (NF) T3 isolate and then tested with 14 different strains, including the fastidious one. Combinations of nutritive components such as meat/vegetable broth, LB medium, malt and skimmed milk led to the design of new media suitable for culturing all the isolates tested, in conditions similar to those obtained in standard culture media such as PYG or CERVA.

Isolation and molecular characterization of Acanthamoeba from patients with keratitis in Spain

In order to improve our knowledge on the epidemiology of amoebic keratitis, as well as the identification of Acanthamoeba isolates, we have isolated Acanthamoeba spp. from five symptomatic patients in Spain in the present study. All isolates were grown in axenic liquid medium, with only one exception. The morphology of these isolates were characterized by optical and scanning electron microscopy. Their structural features corresponded to those of amphizoic amoebae (namely Acanthamoeba spp.). The molecular characterization of the five Acanthamoeba isolates yielded six sequences. Almost complete 18S rRNA gene sequences (>2000bp) were obtained from three isolates and partial sequences (∼1500bp) from the other two. A robust phylogenetic analysis based on the almost complete 18S rRNA sequence showed that four isolates belonged to the T4 genotype and the other one to the T3 genotype. However, all isolates were identified as T4 genotype using the ASA.S1 fragment. As previously suggested by other researchers, only a robust phylogenetic approach may be helpful in identifying Acanthamoeba genotypes. In addition, new data on the phylogenetic relationships among the Acanthamoeba genotypes is provided and discussed.

Microwave Irradiation as a Promising Method of Sterilization for Acanthamoeba polyphaga in Cultures

PURPOSE

To determine the killing effect of microwave irradiation on Acanthamoeba polyphaga.

METHODS

The trophozoites and cysts of A. polyphaga both in water and on agar were exposed to microwave irradiation with a capacity of 750 W for 0, 1, 3, 5, and 10 minutes, respectively. Furthermore, the trophozoites and cysts of A. polyphaga in water were exposed to microwave irradiation with a capacity of 100, 300, and 500 W for 1 minute, respectively.

RESULTS

The trophozoites and cysts of A. polyphaga on agar were completely killed by 3 minutes of microwave irradiation with a capacity of 750 W. The trophozoites and cysts of A. polyphaga in water were completely killed by microwave irradiation with a capacity of 300 W for 1 minute.

CONCLUSIONS

We demonstrate that microwave treatment is effective in killing A. polyphaga both in water and on agar and may be a helpful modality to prevent Acanthamoeba keratitis.

Inactivation of Acanthamoeba spp. and Other Ocular Pathogens by Application of Cold Atmospheric Gas Plasma

Currently there are estimated to be approximately 3.7 million contact lens wearers in the United Kingdom and 39.2 million in North America. Contact lens wear is a major risk factor for developing an infection of the cornea known as keratitis due to poor lens hygiene practices. While there is an international standard for testing disinfection methods against bacteria and fungi (ISO 14729), no such guidelines exist for the protozoan Acanthamoeba, which causes a potentially blinding keratitis most commonly seen in contact lens wearers, and as a result, many commercially available disinfecting solutions show incomplete disinfection after 6 and 24 h of exposure. Challenge test assays based on international standard ISO 14729 were used to determine the antimicrobial activity of cold atmospheric gas plasma (CAP) against Pseudomonas aeruginosa, Candida albicans, and trophozoites and cysts of Acanthamoeba polyphaga and Acanthamoeba castellanii P. aeruginosa and C. albicans were completely inactivated in 0.5 min and 2 min, respectively, and trophozoites of A. polyphaga and A. castellanii were completely inactivated in 1 min and 2 min, respectively. Furthermore, for the highly resistant cyst stage of both species, complete inactivation was achieved after 4 min of exposure to CAP. This study demonstrates that the CAP technology is highly effective against bacterial, fungal, and protozoan pathogens. The further development of this technology has enormous potential, as this approach is able to deliver the complete inactivation of ocular pathogens in minutes, in contrast to commercial multipurpose disinfecting solutions that require a minimum of 6 h.

The effect of microwave irradiation on the vitality of various dermatophytes

Dermatomycosis is one of the most common dermatological infectious diseases. In recent years, the incidence of tinea pedum, a fungal infection of the feet, was increasing due to changing lifestyles. The risk of tinea pedum infections is associated with the use of sport shoes as well as contact with public sports facilities. Transmission of dermatomycosis occurs almost exclusively through indirect contacts, meaning that contagious material initially contaminates the patients' environment and subsequently facilitates the spread of infection to others. A suitable disinfection procedure for 'fungal reservoirs' is very important in order to reduce the risk of reinfection of tinea pedum. This study investigates the effect of microwave radiation on various dermatophytes- (Trichophyton rubrum, T. rubrum var. nigricans, T. interdigitale and Microsporum canis infected cork and polyethylene sponge shoe insoles. The contaminated insoles were irradiated with various intensities and durations of microwaves. In each case, 10 colonies on cork and polyethylene sponge insoles were irradiated with the same intensity and duration, and subsequently compared with those of corresponding non-irradiated control groups. Results of three independent experiments were statistically verified using Chi-squared test for significance. We found significant differences between the various dermatophytes on polyethylene sponge insoles and also partly on cork insoles for the same irradiation intensity and duration. We were also able to show that a complete growth inhibition of all four dermatophytes occurs on both types of insoles after a 30 s exposure at 560 W, including a maximum temperature of 60 °C.

Evaluation of two alternative methods for disinfection of toothbrushes and tongue scrapers

OBJECTIVE

The aim of this study was to investigate the effectiveness of two alternatives methods for the disinfection of oral cleaning devices.

METHODS

One type of toothbrush and two types of tongue scrapers (steel and plastic) were tested in this study. Sixteen specimens of each group were cut with standardized dimensions, contaminated separately with Candida albicans, Streptococcus mutans and Staphylococcus aureus and incubated for 24 h. After this, oral cleaning devices were washed in saline solution to remove non-adhered cells and divided into two groups (n = 8), one irradiated in microwave and other immersed in 3.78% sodium perborate solution, and evaluated for microbial recovery. The values of cfu of each group of microorganism after disinfection were compared by Kruskal-Wallis and Dunn non-parametric test, considering 95% of confidence.

RESULTS

The toothbrush harboured a significant larger number of viable organisms than the tongue scrapers. The steel tongue scraper was less susceptible to adhesion of the three oral microorganisms. The time required to inactivate all contaminating microorganisms using microwave oven was 1 min and, for the immersion in 3.78% sodium perborate solution, was 2 and 3 h, respectively, for C. albicans and S. mutans/S. aureus.

CONCLUSION

Microwave irradiation proved to be an effective alternative method to the disinfection of tongue cleaners and toothbrushes.

A conventional microwave oven for denture cleaning: a critical review

INTRODUCTION

Denture cleaning should be quick and easy to perform, especially in long-term care facilities. The lack of proper oral hygiene can put older adults at higher risk from opportunistic oral infections, particularly fungal. As an alternative to regular brushing, the use of a microwave oven has been suggested for cleaning and disinfecting dentures.

OBJECTIVES

To synthesise and discuss the advantages and disadvantages of the use of a conventional microwave oven for cleaning and disinfecting complete dentures.

METHODS

A brief literature search focused on papers dealing with microwave therapy for denture cleaning through PubMed Central, Cochrane Database of Systematic Reviews, Google Scholar, Ovid MEDLINE(R) In-Process, and Scifinder Scholar.

RESULTS

One hundred and sixty-seven manuscripts published in English with full text were found, and 28 were accepted and discussed in the light of the advantages and disadvantages of the use of conventional microwave oven for cleaning and disinfecting complete dentures.

CONCLUSIONS

There was no standardisation for microwave use for denture cleaning. Manual cleaning still seemed to be the optimal method for controlling fungal infection and denture stomatitis. However, such a daily routine appeared to be underused, particularly in long-term care facilities.

Dark secrets behind the shimmer of contact lens: the Indian scenario

Background

We studied the bacteriological profile of soft contact lens and its accessories among the asymptomatic subjects and monitored the compliance level with the lens use and its cleaning protocol.

Findings

A total of 115 (104 daily wear and 11 extended wear) subjects using contact lens were studied. Data regarding the duration of use and frequency and method of cleaning were recorded. Contact lens, lens cases, preserving solutions and tips of solution bottles were the samples collected. The isolates were identified on the basis of their phenotypic characters. Samples from 24 subjects (21 daily wear and 3 extended wear) were found contaminated. Of the 24 contaminated cases, 23 showed medium adherence to the cleaning protocol. Contamination rate was higher among the 56 daily wear lens users who used same lens for 2 years and more, than the 48 users who used their lenses for less than 2 years. Lens case contamination was found in all the 24 cases. The bacteria isolated were Citrobacter freundii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus epidermidis and Streptococcus pneumoniae. In extended wear lens users, there was no change in microbial flora on repeating the cultures on day 7 and 14.

Conclusion

Non-compliance with contact lens use may lead to invitation of microbial flora. The accumulation of these bacteria may act as a precursor to biofilm formation, thus colonizing the lens accessories as well. The bacteria isolated in this study were similar to the ones causing microbial keratitis thus, predisposing the otherwise asymptomatic subjects to permanent visual damage.

Denture disinfection by microwave irradiation: a randomized clinical study

OBJECTIVE

This study evaluated the clinical effectiveness of two exposure times of microwave irradiation on the disinfection of complete dentures.

METHODS

Biofilm samples were collected from dentures of 30 patients, who were randomly divided into two experimental groups of 15 subjects each: Group 1-patients had their maxillary denture microwaved for 3 min (650W); Group 2-patients had their maxillary denture microwaved for 2 min (650W). Denture biofilm samples were taken with swabs, before (left side surfaces) and after (right side surfaces) microwave irradiation. All microbial material was plated on selective media for Candida spp., Staphylococcus spp., mutans streptococci and a non-selective media. After incubation (48 h/37 degrees C), the number of colony-forming units (cfu/mL) was counted. Microorganisms which grew on selective media were identified using biochemical methods. The data were statistically analyzed by Kruskal-Wallis test, followed by Dunn's post-test (alpha=0.05).

RESULTS

Microwave irradiation for 3 min (Group 1) resulted in sterilization of all dentures evaluated. After microwave irradiation for 2 min (Group 2), a significant decrease in Candida spp. (P=0.0062), Staphylococcus spp. (P=0.0178), mutans streptococci (P=0.0047) and non-identified species (P<0.0001) was achieved in comparison with the cfu/mL obtained before irradiation. The colonies grown after 2 min of microwave irradiation were identified as Candida albicans, non-aureus Staphylococci and Streptococcus mutans.

CONCLUSION

Microwave irradiation for 3 min may be a potential treatment to prevent cross-contamination.

Acanthamoeba: a review of its potential to cause keratitis, current lens care solution disinfection standards and methodologies, and strategies to reduce patient risk

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.

On Acanthamoeba keratitis

Az Acanthamoeba-infekciók száma világszerte, így hazánkban is növekvő tendenciát mutat. A diagnosztikus és terápiás lehetőségek bővülése ellenére ez a betegség súlyosan károsíthatja a látást. A kórkép jellemzőit foglaljuk össze és mutatjuk be. A betegség elsősorban kontaktlencsét viselőkön alakul ki a nem megfelelő higiénia miatt. Szubjektív tünetei a fájdalom, vörös szem, könnyezés és szemhéjduzzanat. A klinikai képben jellegzetes a gyűrű alakú cornea stromájába terjedő infiltrátum. Differenciáldiagnosztikai szempontból a bakteriális, gombás és herpeses keratitistől kell elkülöníteni. Diagnózisában, a részletes anamnézis mellett, elsősorban konfokális corneamikroszkópia és speciális mikrobiológiai vizsgálatok javasoltak. A kórkép kezelésére többféle konzervatív és sebészi terápia létezik. Az eredményes gyógyuláshoz időben történő felismerés és hosszan tartó adekvát terápia szükséges. A legfontosabb azonban a megelőzés, amely az illesztők feladata, a páciensek felvilágosítása a megfelelő higiénés szabályok betartásáról, a korszerű lencsék és ápolószerek használatáról.

Factors affecting the epidemiology of Acanthamoeba keratitis

Despite being a relatively rare disease in comparison with other forms of infectious keratitis, Acanthamoeba keratitis is a potentially blinding disease. Wide variations in the incidence of Acanthamoeba keratitis have been reported in both developed and developing countries. At the same time that contact lens wear was found to be responsible for the spread of the disease in developed countries, Acanthamoeba keratitis was considered a rare disease in developing countries compared with fungal and bacterial keratitis. In recent decades, the risk of getting Acanthamoeba keratitis has increased because of the increased proportion of contact lens wearers. This article introduces the different factors affecting the epidemiology of Acanthamoeba keratitis worldwide, presents a chronological review of the literature, and shows the progressive spread of Acanthamoeba keratitis in the last two decades in different geographical areas of the world. A detailed comparison of the incidence of the disease as reported in different studies in different countries is made. The impact of contact lenses and other factors, such as hot weather, virulence of Acanthamoeba strains, water sanitation and quality, the occurrence of environmental disasters such as flooding, and the wide environmental presence of Acanthamoeba cysts on the incidence of the disease, are discussed. In addition, the ability of Acanthamoeba cysts to resist different harsh conditions is reviewed.

Acanthamoeba Keratitis and Contact Lens Disinfecting Solutions

OBJECTIVES

To report cases of culture-proved Acanthamoeba keratitis in Greece over a 10-year period and to evaluate the effectiveness of the commonly used commercial contact lens disinfecting systems in clinical cases of Acanthamoeba keratitis.

MATERIAL AND METHODS

During the years 1994-2004, 45 contact lens wearers and 3 non-contact lens wearers presenting with symptoms and signs of keratitis underwent corneal sampling. The scrapings obtained were inoculated directly onto appropriate culture media for bacteria, fungi and Acanthamoeba. All proved positive for Acanthamoeba. The contact lenses and contact lens disinfecting solutions (16 one-step 3% hydrogen peroxide and 3 multipurpose solutions) of 19/45 patients with culture-proven Acanthamoeba keratitis were cultured for bacteria, fungi and Acanthamoeba.

RESULTS

Acanthamoeba was isolated from contact lenses and contact lens disinfecting solutions in all 19 cases of Acanthamoeba keratitis studied.

CONCLUSIONS

The main risk factor for corneal infection in contact lens wearers is the use of contact lens disinfecting systems ineffective at killing Acanthamoeba cysts and trophozoites, as well as bacteria and fungi. Improvement or development of new contact lens disinfecting systems by manufacturers is needed to prevent Acanthamoeba keratitis.

Efficacy of contact lens storage solutions against different acanthamoeba strains

PURPOSE

This study was undertaken in order to determine the susceptibility of acanthamoebae to various contact lens disinfecting systems, with respect to type of disinfectant and exposure time.

METHODS

Ten contact lens solutions, including one new system, were tested for their effectivities against cysts of three Acanthamoeba strains. Of main interest was an incubation time of 8 hours (overnight disinfection) and cyst quantities of 10 and 10, respectively.

RESULTS

Boston Advance (polyaminopropyl biguanide 0.0005%, chlorhexidine 0.003%) for the storage of rigid gas permeable contact lenses destroyed the cysts of all strains at either concentration within one hour of exposure. Meni Care Plus (polyhexamethylene biguanide 0.0005%) also destroyed 10 cysts of all strains, however, 10 cysts only of two strains within one hour; after an exposure time of 8 hours all cysts were killed. The disinfecting solutions for soft contact lenses did not kill 10 cysts of either strain after 8 hours of incubation time.

CONCLUSION

Two of the tested contact lens solutions (the ones for rigid gas permeable lenses) destroyed the cysts of all strains. One of these, containing a combination of two amoebicidal ingredients even after only one hour of exposure time.

Synthesis and activity of 1H-benzimidazole and 1H-benzotriazole derivatives as inhibitors of Acanthamoeba castellanii

Chloro-, bromo- and methyl- analogues of 1H-benzimidazole and 1H-benzotriazole and their N-alkyl derivatives have been synthesized and tested in vitro against the protozoa Acanthamoeba castellanii. The results indicate that 5,6-dimethyl-1H-benzotriazole (11) and 5,6-dibromo-1H-benzotriazole (14) have higher efficacy than the antiprotozoal agent chlorohexidine.

Testing of a Dual-Mode Microwave Care Regimen for Hydrogel Lenses

PURPOSE

To test the design of a patient care regimen for soft lenses that aims to provide the highest standards of disinfecting through use of domestic microwave cookers, while also providing storage equipment and solution that enable patients to follow a conventional cold disinfecting regimen when traveling. The cleaning efficacy of surfactant agents during microwave treatment was also considered.

METHODS

The microbiologic performance of the regimen and its disinfecting apparatus was tested according to the Food and Drug Administration (FDA) protocols for contact lens heat disinfectors. Subsequently, a prospective pilot clinical trial of the regimen involving 15 subjects was carried out to the protocols of the FDA and International Standards Organization 11,980:1997.

RESULTS

Lenses inoculated with 10(7) colony-forming units (cfu) of Enterococcus faecalis were disinfected to 0 cfu by a 12-s irradiation of a compact disinfecting case that held the lenses suspended in 12 ml saline. A proof of operation indicator performed correctly for all 10 cases tested. No adverse reactions were found in the pilot patient trial, using Renu multipurpose (Bausch and Lomb, Rochester, NY) as the test solution, and no statistically significant difference was found between test and control groups in respect of any sign. However, the greater incidence of edema, palpebral hyperemia, and lens front-surface deposition in the microwave test group may be clinically significant.

CONCLUSIONS

The design of the test care regimen proved easy for patients to follow in either hot or cold disinfecting mode. The greater incidence of certain signs in the microwave test group suggests the need to continue using a rub and rinse step for the microwave mode and for additional investigation into the choice of an appropriate multipurpose solution formulation for this proposed regimen, preferably one that does not use a block copolymer-type surfactant agent.

Health effects of Acanthamoeba spp. and its potential for waterborne transmission

Risk from Acanthamoeba keratitis is complex, depending upon the virulence of the particular strain, exposure, trauma, or other stress to the eye, and host immune response. Bacterial endosymbionts may also play a factor in the pathogenicity of Acanthamoeba. Which factor(s) may be the most important is not clear. The ability of the host to produce IgA antibodies in tears may be a significant factor. The immune response of the host is a significant risk factor for GAE infection. If so, then a certain subpopulation with an inability to produce IgA in the tears may be at greatest risk. There was no sufficient data on the occurrence or types of Acanthamoeba in tapwater in the U.S. Published work on amoebal presence in tapwater does not provide information on the type of treatment the water received or the level of residual chlorine. Assessment of the pathogenicity by cell culture and molecular methods of Acanthamoeba in tapwater would also be useful in the risk assessment process for drinking water. The possibility that Acanthamoeba spp. might serve as vectors for bacterial infections from water sources also should be explored. The bacterial endosymbionts include an interesting array of pathogens such as Vibrio cholerae and Legionella pneumophila, both of which are well recognized waterborne/water-based pathogens. Work is needed to determine if control of Acanthamoeba spp. is needed to control water-based pathogens in water supplies.

Acanthamoeba spp. as agents of disease in humans

Acanthamoeba spp. are free-living amebae that inhabit a variety of air, soil, and water environments. However, these amebae can also act as opportunistic as well as nonopportunistic pathogens. They are the causative agents of granulomatous amebic encephalitis and amebic keratitis and have been associated with cutaneous lesions and sinusitis. Immuno compromised individuals, including AIDS patients, are particularly susceptible to infections with Acanthamoeba. The immune defense mechanisms that operate against Acanthamoeba have not been well characterized, but it has been proposed that both innate and acquired immunity play a role. The ameba's life cycle includes an active feeding trophozoite stage and a dormant cyst stage. Trophozoites feed on bacteria, yeast, and algae. However, both trophozoites and cysts can retain viable bacteria and may serve as reservoirs for bacteria with human pathogenic potential. Diagnosis of infection includes direct microscopy of wet mounts of cerebrospinal fluid or stained smears of cerebrospinal fluid sediment, light or electron microscopy of tissues, in vitro cultivation of Acanthamoeba, and histological assessment of frozen or paraffin-embedded sections of brain or cutaneous lesion biopsy material. Immunocytochemistry, chemifluorescent dye staining, PCR, and analysis of DNA sequence variation also have been employed for laboratory diagnosis. Treatment of Acanthamoeba infections has met with mixed results. However, chlorhexidine gluconate, alone or in combination with propamidene isethionate, is effective in some patients. Furthermore, effective treatment is complicated since patients may present with underlying disease and Acanthamoeba infection may not be recognized. Since an increase in the number of cases of Acanthamoeba infections has occurred worldwide, these protozoa have become increasingly important as agents of human disease.

Cytotoxic activities of alkylphosphocholines against clinical isolates of Acanthamoeba spp

Free-living amoebae of the genus Acanthamoeba are causing serious chronic conditions such as destructive keratitis in contact lens wearers or granulomatous amoebic encephalitis in individuals with compromised immune systems. Both are characterized by the lack of availability of sufficiently effective and uncomplicated, manageable treatments. Hexadecylphosphocholine (miltefosine) is licensed for use as a topical antineoplastic agent, but it is also active in vitro against several protozoan parasites, and it was applied very successfully for the treatment of human visceral leishmaniasis. The aim of our study was to evaluate the efficacy of hexadecylphosphocholine and other alkylphosphocholines (APCs) against Acanthamoeba spp. The in vitro activities of eight different APCs against three Acanthamoeba strains of various pathogenicities were determined. All substances showed at least amoebostatic effects, and some of them disrupted the amoebae, as shown by the release of cytoplasmic enzyme activity. Hexadecylphosphocholine exhibited the highest degree of cytotoxicity against trophozoites, resulting in complete cell death at a concentration as low as 40 microM, and also displayed significant cysticidal activity. Hexadecylphosphocholine may be a promising new candidate for the topical treatment of Acanthamoeba keratitis and, conceivably, even for the oral treatment of granulomatous amoebic encephalitis.

Viability of Acanthamoeba after exposure to a multipurpose disinfecting contact lens solution and two hydrogen peroxide systems

BACKGROUND/AIM

Contact lens cases contaminated with Acanthamoeba are a major risk factor for an infection of the eye. In this study the anti-Acanthamoeba activity of three different contact lens storage solutions was tested.

METHODS

A new multipurpose contact lens storage solution (Meni Care Plus) and a two step (Titmus H(2)O(2)) and one step (Oxysept Comfort) hydrogen peroxide system were tested for their effects on trophozoites and cysts of three different Acanthamoeba species: A castellanii, A hatchetti, and A lenticulata.

RESULTS

After a soaking time of 8 hours (overnight soaking of contact lenses) the Titmus H(2)O(2) 0.6% solution showed very good amoebicidal effects, while Oxysept Comfort 3% H(2)O(2) could not effectively destroy the cysts of any of the three tested species. Viable cysts of the species A lenticulata and A hatchetti were still present after exposure to Meni Care Plus (0.0005% PHMB) for 8 hours.

CONCLUSION

Not all of the three tested contact lens storage solutions have sufficient amoebicidal effects. The two step peroxide system Titmus H(2)O(2) is a very effective disinfectant contact lens solution in order to avoid a possible Acanthamoeba infection of the eye.