The role of domestic tap water in Acanthamoeba contamination in contact lens storage cases in Korea

Impact of contact lens hygiene risk factors on the prevalence of contact lens-related keratitis in Alexandria-Egypt

BACKGROUND

This study aimed at measuring the effect of contact lens hygiene risk factors on the prevalence of contact lens-related keratitis and identifying the specific risk factors to both microbial and non-microbial keratitis independently.

METHODS

A cross-sectional study was conducted at Alexandria Ophthalmology Hospital from May to October 2023. All contact lens wearers attending the outpatient clinic had undergone face-to-face interviews using a standardized validated questionnaire which included demographic data and contact lenses (CLs) hygiene risk factors. Participants were classified into two groups; normal group and keratitis group. Keratitis group was further subdivided into non-microbial and microbial group.

RESULTS

The study included 245 contact lens wearers; 149 normal cases, 50 (20.4%) contact lens-related non-microbial keratitis (CLNK) cases, and 46 (18.8%) contact lens-related microbial keratitis (CLMK) cases. Sharing contact lenses and eye trauma were significant risk factors for both CLNK (p=0.036), (p=0.001) and CLMK (p=0.003), (p=0.017). CLs wear duration for more than 12 hours was associated with an increased risk of CLNK by about 4 times (p=0.030) and overnight wear of contact lenses increased the risk of CLNK by 2.6 times (p=0.030). Showering or swimming in lenses was identified as a significant risk factor for CLMK (p=0.012), moreover washing lenses with tap water increased the risk of CLMK (p=0.030).

CONCLUSIONS

Poor compliance with contact lenses hygiene rules results in a high prevalence of contact lens-related keratitis. Eye trauma and sharing contact lenses were significant hygiene risk factors for both contact lens-related non-microbial keratitis and contact lens-related microbial keratitis.

Presence and diversity of free-living amoebae and their potential application as water quality indicators

Free-living amoebae (FLA) are found in diverse environments, such as soils, rivers, and seas. Hence, they can be used as bioindicators to assess the water quality based solely on their presence. In this study, we determined the presence of FLA in river water by filtering water samples collected from various sites and culturing the resulting filtrates. FLA were detected in all the water samples with varying quality grades (Grades Ι-V). The significant increase in the size of the amoebae population with the deterioration in the water quality. Monoxenic cultures of the amoebae were performed, and genomic DNAs were isolated, among which 18S rDNAs were sequenced to identify the amoeba species. Of the 12 species identified, 10 belonged to the Acanthamoeba genus; of the remaining 2 species, one was identified as Vannella croatica and the other as a species of Vermamoeba. Acanthamoeba was detected in samples with Grades Ι to VI quality, whereas the Vermamoeba species was present only in Grade Ι water. V. croatica was found exclusively in water with Grade ΙΙ quality. Following morphological observations, genomic DNA was sequenced using 16S rDNA to determine whether the species of Acanthamoeba harbored endosymbionts. Most of the isolated Acanthamoeba contained endosymbionts, among which 4 species of endogenous bacteria were identified and examined using transmission electron microscopy. This study provides evidence that the distribution of amoebae other than Acanthamoeba may be associated with water quality. However, further confirmation will be required based on accurate water quality ratings and assessments using a more diverse range of FLA.

Molecular detection and characterization of Acanthamoeba infection in dogs and its association with keratitis in Korea

Acanthamoeba infection is associated with keratitis in humans; however, its association with keratitis in dogs remains unclear. To investigate this possibility, we collected 171 conjunctival swab samples from dogs with eye-related diseases (65 with keratitis and 106 without keratitis) at Chungbuk National University Veterinary Teaching Hospital, Korea, from August 2021 to September 2022. Polymerase chain reaction identified 9 samples (5.3%) as Acanthamoeba positive; of these, 3 were from dogs with keratitis (4.6%) and 6 were from dogs without keratitis (5.7%). Our results indicated no significant association between Acanthamoeba infection and keratitis, season, sex, or age. All Acanthamoeba organisms found in this study had the genotype T4, according to 18S ribosomal RNA analysis. Acanthamoeba infection in dogs might have only a limited association with keratitis.

Molecular characterization and phylogenetic analysis of FLA from different water sources in Egypt

Free-living amoebae (FLA) are protozoa ubiquitously found in nature. In addition to their natural distribution, some species have been documented as pathogenic to humans. The main aim of the current study was the molecular identification, sequencing and phylogenetic analysis of morphologically detected FLA in water sources in El-Qalyubia, Egypt. A total of 96 water samples were collected from different water sources. Each water sample was filtrated and cultured on non-nutrient agar (NNA). Morphologically positive FLA were subjected to PCR, PCR products were sequenced and the obtained sequences were phylogenetically analysed. FLA were found in 41 water samples examined (42.7%). Nile water and groundwater were the sources with the highest prevalence rates (83.3 and 62.5%, respectively). Naegleria italica was first identified in Egypt from the waters of the Nile. In addition, Vahlkampfia spp. and Hartmannella spp. were also detected. However, other FLA species, including Acanthamoeba spp. and the pathogenic Naegleria fowleri, previously reported in Egypt, were not included in this study. The recent identification of these FLA in the Egyptian waters related to human populations indicates the need for more phylogenetic studies using larger sample sizes to investigate their potential threat to human health.

A Systematic Review of Intracellular Microorganisms within Acanthamoeba to Understand Potential Impact for Infection

Acanthamoeba, an opportunistic pathogen is known to cause an infection of the cornea, central nervous system, and skin. Acanthamoeba feeds different microorganisms, including potentially pathogenic prokaryotes; some of microbes have developed ways of surviving intracellularly and this may mean that Acanthamoeba acts as incubator of important pathogens. A systematic review of the literature was performed in order to capture a comprehensive picture of the variety of microbial species identified within Acanthamoeba following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Forty-three studies met the inclusion criteria, 26 studies (60.5%) examined environmental samples, eight (18.6%) studies examined clinical specimens, and another nine (20.9%) studies analysed both types of samples. Polymerase chain reaction (PCR) followed by gene sequencing was the most common technique used to identify the intracellular microorganisms. Important pathogenic bacteria, such as E. coli, Mycobacterium spp. and P. aeruginosa, were observed in clinical isolates of Acanthamoeba, whereas Legionella, adenovirus, mimivirus, and unidentified bacteria (Candidatus) were often identified in environmental Acanthamoeba. Increasing resistance of Acanthamoeba associated intracellular pathogens to antimicrobials is an increased risk to public health. Molecular-based future studies are needed in order to assess the microbiome residing in Acanthamoeba, as a research on the hypotheses that intracellular microbes can affect the pathogenicity of Acanthamoeba infections.

In vivo efficacy of silver-impregnated barrel contact lens storage cases

PURPOSE

This study examined the rate and level of microbial contamination of silver and non-silver (control) barrel contact lens storage cases in vivo.

METHODS

A prospective, single-centre, randomized, double blinded, crossover study was conducted to evaluate the efficacy of silver and control barrel cases used with an Oxipol™-based disinfecting solution over a two-month period. Lens cases were collected, and the frequency, type and level of microbial contamination evaluated using viable culture and standard identification methods. Questionnaires were used to assess the contact lens-related hygiene compliance of the participants.

RESULTS

Forty eight daily contact lens wearers completed the study. Overall, 27 % of silver and 35 % control lens cases (P > 0.05) were contaminated, predominantly with Gram-positive bacteria. Only, 12 % of participants had good compliance, with 46 % having average compliance and 43 % poor compliance. Compliance score was not associated with level of microbial contamination. However, the use of hydrogel lenses in combination with silver cases compared to non-silver barrel cases resulted significantly greater numbers of bacteria colonising cases.

CONCLUSION

The present investigation demonstrated that the use of silver barrel cases does not reduce the overall rate and level of bacterial contamination, but that using hydrogel lenses in combination with silver cases resulted in higher numbers of bacteria isolated from cases.

Identification of Free-Living Amoebas in Tap Water of Buildings with Storage Tanks in Korea

Free-living amoebas (FLAs) can cause severe disease in humans and animals when they become infected. However, there are no accurate survey reports on the prevalence of FLAs in Korea. In this study, we collected 163 tap water samples from buildings, apartments, and restrooms of highway service areas in 7 Korean provinces with high population density. All these buildings and facilities have water storage tanks in common. The survey was separated into categories of buildings, apartments, and highway service areas. Five hundred milliliters of tap water from each building was collected and filtered with 0.2 µm pore filter paper. The filters were incubated in agar plates with heated E. coli at 25°C. After axenization, genomic DNA was collected from each FLA, and species classification was performed using partial 18S-rDNA PCR-sequencing analysis. We found that 12.9% of tap water from buildings with storage tanks in Korea was contaminated with FLAs. The highway service areas had the highest contamination rate at 33.3%. All of the FLAs, except one, were genetically similar to Vermamoeba vermiformis (Hartmannella vermiformis). The remaining FLA (KFA21) was very similar to Acanthamoeba lugdunensis (KA/E26). Although cases of human infection by V. vermiformis are very rare, we must pay attention to the fact that one-third of tap water supplies in highway service areas have been contaminated.

Isolation of Acanthamoeba T5 from Water: Characterization of Its Pathogenic Potential, Including the Production of Extracellular Vesicles

Acanthamoeba is a genus of free-living amoebae widely distributed in nature, associated with the development of encephalitis and keratitis. Despite the fact that it is common to find genotype T5 in environmental samples, only a few cases have been associated with clinical cases in humans. The wide distribution of Acanthamoeba, the characteristic of being amphizoic and the severity of the disease motivate researchers to focus on the isolation of these organisms, but also in demonstrating direct and indirect factors that could indicate a possible pathogenic potential. Here, we performed the characterization of the pathogenic potential of an Acanthamoeba T5 isolate collected from a water source in a hospital. Osmo- and thermotolerance, the secretion of proteases and the effect of trophozoites over cell monolayers were analyzed by different methodologies. Additionally, we confirm the secretion of extracellular vesicles (EVs) of this isolate incubated at two different temperatures, and the presence of serine and cysteine proteases in these vesicles. Finally, using atomic force microscopy, we determined some nanomechanical properties of the secreted vesicles and found a higher value of adhesion in the EVs obtained at 37 °C, which could have implications in the parasite´s survival and damaging potential in two different biological environments.

Heat and chlorine resistance of a soil Acanthamoeba sp. cysts in water

AIMS

The study established the inactivation kinetic parameters of an Acanthamoeba cyst isolate subjected to heating and chlorination.

METHODS AND RESULTS

A strain of Acanthamoeba was isolated and purified from an area surrounding a pilot food plant. Mature cysts (14 days) were subjected to heat inactivation studies at 71, 76, 81, 86 and 91°C; and chlorination at 100, 200, 300, 400 and 500 ppm. The decimal reduction times (D-values) at 71, 76, 81, 86 and 91°C were 18·31, 9·26, 7·35, 4·52 and 1·81 min respectively. The calculated thermal resistance constant (z-value) was 21·32°C (R²  = 0·96-0·97). The D-value in 100, 200, 300, 400 and 500 ppm chlorine-treated water were 47·17, 25·06, 24·51, 23·70 and 18·55 min respectively. The chlorine resistance constant (z-value) was 1179 ppm chlorine (R²  = 0·65-0·74).

CONCLUSIONS

Results demonstrated high resistance of the isolated Acanthamoeba cysts towards the common methods applied in ensuring food and food processing environment sanitation.

SIGNIFICANCE AND IMPACT OF THE STUDY

The resistance parameters of the test organisms established in this study may be used in the establishment of Sanitation Standard Operating Procedures (SSOPs), which are often based on inactivation of bacteria. These SSOPs could render better protection to food and food processing environments.

Molecular detection of free-living amoebae from Namhangang (southern Han River) in Korea

The free-living amoebae Naegleria spp. and Acanthamoeba spp. exist in the natural environment and are sometimes causal agents of lethal primary amoebic meningoencephalitis (PAM), amoebic keratitis (AK) and granulomatous amebic encephalitis (GAE) in humans, respectively. To ascertain the existence of free-living amoebae in Korea, water samples were collected from the Korean hydrosphere, Namhangang (southern Han River), an active location for water skiing and recreation. Samples underwent two-step filtration and were cultured on non-nutrient agar medium with inactivated E. coli. The remaining samples were subjected to PCR for primarily the 18S small ribosomal RNA gene and gene sequencing. Similarities in 18S rDNA sequences, in comparison with various reference amoebae in GenBank, showed 86~99% homology with N. gruberi, N. philippinensis, N. clarki, A. polyphaga, A. castellannii, and Hartmannella (Vermamoeba) vermiformis. Therefore, this study will be useful for seasonal detection of free-living amoebae from various Korean hydrospheres in future studies.

Molecular characterization and phylogenetic analysis of Acanthamoeba isolates in tap water of Beni-Suef, Egypt

The genus Acanthamoeba is a free-living amoeba widely distributed in various aquatic environments. It is an etiologic cause of amoebic encephalitis and keratitis particularly for immunocompromised individuals. The purpose of the present study was to investigate Acanthamoeba species prevalence in household and hospital potable water in Beni-Suef governorate, Egypt, and to employ sequencing methods to identify positive Acanthamoeba species isolates and their potential health risks. Sixty tap water samples (30 household and 30 governmental and private hospital settings) collected from Beni-Suef governorate, Egypt were filtered, cultured on non-nutrient agar, identified by morphotyping keys after staining with Giemsa stain and then confirmed by PCR using Acanthamoeba specific primers. Twenty positive samples were successfully genetically characterized and phylogenetically analyzed to identify Acanthamoeba species. The total detection rate for Acanthamoeba was 48/60 (80%); Acanthamoeba contamination in water collected from domestic houses was higher than in hospitals; 27/30 (90%) versus 21/30 (70%) with statistical significant value (P value = 0.05). Sequencing of 20 positive isolates revealed Acanthamoeba T4 in 65% and T2 in 35%. To our knowledge, this is the first research that documents the occurrence and phylogeny of Acanthamoeba species in Beni-Suef, Egypt. The presence of a higher percentage of Acanthamoeba species in tap water, in particular T4, highlights the potential health hazards for immunocompromised individuals and emphasizes the urgent need for the implementation of effective filtration and disinfection measures.

Isolation, identification of pathogenic Acanthamoeba from drinking and recreational water sources in Saudi Arabia

Objective:

The present study was conducted to isolate and identify the Acanthamoeba species from various water sources such as drinking water, tap water, swimming pool, and other recreational water.

Materials and methods:

During the study period, 57 water samples were collected from various sources such as tap water, drinking water, swimming pool, and recreational water. All samples were processed and cultured on non-nutrient agar medium (NNA) with Escherichia coli overlay for the isolation of Acanthamoeba species. Organism identified based on the microscopic morphology of cyst and trophozoites forms. The pathogenicity of Acanthamoeba was analyzed by thermotolerance and osmotolerance assays.

Results:

Acanthamoeba were detected in 10 out of 57 (17.5%) examined water samples. The high percentage of positivity was observed in bore well water stored in tanks (37.5%) and in recreational water samples (26.7%). All processed drinking water samples were free from Acanthamoeba. Based on pathogenicity test assays, four (40%) were pathogenic and three (30%) were non-pathogenic. The observed frequency of Acanthamoeba spp. was compared with available literature worldwide.

Conclusion:

This study is the first report showing the distribution of Acanthamoeba in various water sources in the central region of Saudi Arabia and confirms that the high percentage presence of pathogenic strains in recreational water could threat contact lens wearers. Further research works are required to identify the prevalence of pathogenic Acanthamoeba from various water sources in Saudi Arabia.

A review of cosmetic contact lens infections

This paper provides a comprehensive review of the existing literature surrounding cosmetic contact lens infections. In this paper, lens-related, dispensing-related and patient-related factors are examined in detail.

Acanthamoeba keratitis: confirmation of the UK outbreak and a prospective case-control study identifying contributing risk factors

BACKGROUND/AIMS

Acanthamoeba keratitis (AK) is a chronic debilitating corneal infection principally affecting contact lens (CL) users. Studies were designed to test claims that the UK incidence may have increased in 2012-2014 and to evaluate potential causes.

METHODS

Annualised incidence data were collected from January 1984 to December 2016. Case-control study subjects were recruited between 14 April 2011 and 05 June 2017. Reusable CL users with AK were recruited retrospectively and prospectively. Controls were reusable CL users, recruited prospectively, with any disorder other than AK. Multivariable analysis of questionnaire data measured independent risk factors for AK.

RESULTS

The current outbreak of AK started in 2010-2011 with an incidence threefold higher than in 2004-2009. Risk factors for AK were: Oxipol disinfection, CLs made of group IV CL materials, poor CL hygiene, deficient hand hygiene, use of CLs while swimming or bathing, being white British, and for those in social classes 4-9.

CONCLUSION

AK is a largely preventable disease. The current outbreak is unlikely to be due to any one of the identified risk factors in isolation. Improving CL and hand hygiene, avoiding CLs contamination with water and use of effective CL disinfection solutions, or daily disposable CLs, will reduce the incidence of AK. In the longer-term, water avoidance publicity for CL users can be expected to reduce the incidence further. Ongoing surveillance of AK numbers will identify changes in incidence earlier. Evaluation of Acanthamoeba contamination in end-user drinking water would contribute to our understanding of regional variations in the risk of exposure.

Prevalence of free living amoeba in the domestic waters reservoirs in Sfax, Tunisia

Free living amoebas (FLA) are opportunistic pathogen found in different water sources in the environment. The aim of this study was to investigate the prevalence of free living amoeba in different samples of domestic water reserves (DWR) in Sfax region from Tunisia. It was a prospective study dealing with 486 water samples collected from different DWR. After filtration through a cellulose acetate membrane samples were cultured on non-nutrient agar and the FLA were detected and strained with Giesma, Trichrome and red nuclear stain for morphological and morphotypic studies. FLA were found in 62% of samples. The Acanthopodial morphotype was detected in 43%, Polytactic (38%), Monotactic (28%), Fan-shaped (17%), Rugose (11%), Dactilopodial (10%) and Eruptive (9%). These results demonstrate that domestic water reserves are a significant source of the FLA and maintenance of DWR is recommended.

Influence of secondary water supply systems on microbial community structure and opportunistic pathogen gene markers

Secondary water supply systems (SWSSs) refer to the in-building infrastructures (e.g., water storage tanks) used to supply water pressure beyond the main distribution systems. The purpose of this study was to investigate the influence of SWSSs on microbial community structure and the occurrence of opportunistic pathogens, the latter of which are an emerging public health concern. Higher numbers of bacterial 16S rRNA genes, Legionella and mycobacterial gene markers were found in public building taps served by SWSSs relative to the mains, regardless of the flushing practice (P < 0.05). In residential buildings, genes of L. pneumomhila, Acanthamoeba and Vermamoeba vermiformis were primarily detected in tanks and taps compared to the mains. Long water retention time, warm temperature and loss of disinfectant residuals promoted microbial growth and colonization of potential pathogens in SWSSs. Varied levels of microbial community shifts were found in different types of SWSSs during water transportation from the distribution main to taps, highlighting the critical role of SWSSs in shaping the drinking water microbiota. Overall, the results provided insight to factors that might aid in controlling pathogen proliferation in real-world water systems using SWSSs.

Molecular and Morphometric Characterization of Acanthamoeba spp. from Different Water Sources of Northwest Iran as a Neglected Focus, Co-Bordered With the Country of Iraq

Background

Acanthamoeba spp. is a free-living opportunistic protozoan parasites, which can be found in tap, fresh and bottled mineral waters, contact lens solutions, soil etc.

Objectives

The present study is aimed to determine the Acanthamoeba spp. on the basis of their morpho-molecular aspects in different water sources of the West Azerbaijan province, Northwest of Iran.

Methods

In this cross-sectional study, 60 water samples were collected from rivers and tap waters during June to September 2015. The water samples were filtered through a cellulose nitrate filter and cultured on non-nutrient agar medium. The extracted DNAs were amplified and some ampliqons were sequenced using partial 18S rRNA for genotyping and phylogenetic analyses.

Results

Twenty-seven (45%) out of 60 water samples were positive to Acanthamoeba spp. using both culture and morphological examinations. In addition, 24 (40%) out of 27 positive samples in culture method were confirmed by PCR to be Acanthamoeba spp.

Conclusions

A relatively high prevalence of Acanthamoeba spp. in rivers reflects a risk alert for threatening human health in the region. However, well hygienic status of the tap waters considering Acanthamoeba spp. cannot be ignored in western co-border regions of Iran-Iraq. This study can also serve as a platform for further explorations of water sources in Iran and neighboring countries.

Molecular Characterization of Acanthamoeba Isolates from Surface Resting Waters in Northwest Iran

BACKGROUND

Acanthamoeba is an opportunistic amphizoic protozoan found in different fresh water sources. The aim of this study was to identify and characterize Acanthamoeba isolates from surface resting waters, in Northwest Iran.

METHODS

Samples were collected from twenty-two different areas, between May and Sep 2014. After filtration, samples were cultivated on non-nutrient agar. The extracted DNAs were amplified and sequenced using partial 18S rRNA in order to genotype and phylogenetic analyses.

RESULTS

Thirty-four (68%) out of 50 collected samples were positive for free-living amoebae based on both culture and morphological characterizations but 28 samples were identified as Acanthamoeba spp. by PCR. Sequentially, one isolate was identified as A. lenticulata, (T5) (AN: KP940443, identity 99.7%-100%, and divergence 0.3%) whilst other sequenced isolates identified Acanthamoeba spp. (AN: KP940444-45) as very similar to A. rhysodes and A. royreba with identity 100% and divergence 0%.

CONCLUSION

Surface resting waters in Northwest Iran, were potentially contaminated with pathogenic amphizoic protozoan. Further studies will be required to determine other Acanthamoeba species and genotypes in the region.

Isolation and Genotyping of Acanthamoeba spp. as Neglected Parasites in North of Iran

Acanthamoeba, a free-living amoeba, is widely distributed in the environment, water sources, soil, dust, and air. It can cause keratitis in contact lens wearers with poor hygiene and also fatal granulomatous amebic encephalitis (GAE) in immunocompromised hosts. The aim of this study was to gain some insights into the distribution and genotypes of the potentially pathogenic species of Acanthamoeba present in water sources in north of Iran. Total 43 Acanthamoeba species were isolated from 77 water samples taken from different water sources within the Mazandaran province in Northern Iran (Sari city and suburbs). Isolates were identified based on cyst and trophozoite morphological characteristics as well genetics. PCR fragments corresponding to the small-subunit 18S rRNA gene were sequenced for 20 of 43 positive isolates. The results revealed that 83.3% of sequenced isolates belonged to the T4 genotype and the rest belonged to the T2 genotype. Our results indicated that Acanthamoeba is widely distributed in Sari city. As the incidence in Iran of amoebic keratitis has increased in recent years, the exact estimation of the prevalence of this amoeba and its predominant genotype may play a crucial role in prevention of the disease. Sari city has several rivers, seashores, and natural recreational amenities, which attract visitors during the year. This is the first report of Acanthamoeba genotypes from water sources in Sari city, Mazandaran province of Iran, and the results suggest that more attention is needed to protect the visiting population and immunocompromised individuals.

Acanthamoeba Keratitis among Rigid Gas Permeable Contact Lens Wearers in the United States, 2005 through 2011

PURPOSE

To describe the clinical presentation and outcomes of Acanthamoeba keratitis (AK) in rigid gas permeable (RGP) contact lens wearers and to identify modifiable risk factors.

DESIGN

Case-control investigation.

PARTICIPANTS

Patients were RGP contact lens-wearing United States residents with a diagnosis of AK from 2005 through 2011. Controls were RGP contact lens wearers with no history of AK who were at least 12 years of age.

METHODS

Patients were identified during 2 multistate AK outbreak investigations. Controls from the first investigation in 2007 were identified using a reverse address directory. In the second investigation, controls were recruited from participating ophthalmology and optometry practices. Patients and controls were interviewed by phone using a standardized questionnaire. Odds ratios (ORs) and Fisher exact P values were calculated to assess risk factors associated with infection.

MAIN OUTCOME MEASURES

Acanthamoeba keratitis, a rare eye disease primarily affecting contact lens wearers, is caused by free-living amebae, Acanthamoeba species.

RESULTS

We identified 37 patients in the 2 investigations, 10 (27%) from the 2007 investigation and 27 (73%) from 2011. There were 17 healthy controls, 9 (53%) from 2007 and 8 (47%) from 2011. Among patients, 9 (24%) wore RGP lenses for orthokeratology or therapeutic indication; no controls wore RGP lenses for these indications. Significant risk factors for AK were wearing lenses for orthokeratology (OR, undefined; P = 0.02), sleeping while wearing lenses (OR, 8.00; P = 0.04), storing lenses in tap water (OR, 16.00; P = 0.001), and topping off contact lens solution in the case (OR, 4.80; P = 0.01). After stratifying by use of RGP lenses for orthokeratology, storing lenses in tap water and topping off remained significant exposures.

CONCLUSIONS

Nearly one quarter of patients were orthokeratology wearers. Using tap water to store RGP lenses and topping off solution in the lens case were modifiable risk behaviors identified in RGP wearers who wore lenses for both orthokeratology and nonorthokeratology indications. Rigid gas permeable wearers should avoid exposing their lenses to tap water and should empty their cases and use fresh lens solution each time they take out their lenses.

Acanthamoeba spp. in Contact Lenses from Healthy Individuals from Madrid, Spain

Purpose

Acanthamoeba keratitis (AK) is a painful and potentially blinding corneal infection caused by Acanthamoeba spp. In Madrid, environmental studies have demonstrated a high presence of these free-living amoebae in tap water. Since most of AK cases occur in contact lenses (CL) wearers with inadequate hygiene habits, the presence of Acanthamoeba in discarded CL has been studied and compared with other common etiological agents of keratitis, such as Pseudomonas aeruginosa and Staphylococcus aureus.

Methods

One hundred and seventy-seven healthy individuals from Madrid contributed their discarded CL and answered a questionnaire on hygiene habits. DNA was extracted from the CL solution and analyzed by real-time PCR for Acanthamoeba, Pseudomonas aeruginosa and Staphylococcus aureus. These CL and their solutions were also cultured on non-nutrient agar to isolate Acanthamoeba.

Results

Among the 177 samples, Acanthamoeba DNA was detected in 87 (49.2%), P. aeruginosa DNA in 14 (7.9%) and S. aureus DNA in 19 (10.7%). Cultivable amoebae, however, were observed in only one sample (0.6%). This isolate was genotyped as T4. The habits reported by this CL owner included some recognized risk factors for AK, but in this study only the practice of “not cleaning the CL case” presented some statistical significant association with Acanthamoeba DNA presence. Detection of the investigated bacterial DNA did not demonstrate statistical significant association with the studied practices, but the presence of P. aeruginosa revealed a possible inhibition of Acanthamoeba in these samples.

Conclusions

The PCR results suggest a high presence of Acanthamoeba spp. in healthy CL wearers from Madrid, but we can assume that CL solutions are properly disinfecting the CL since only 1.1% of the positive PCR samples correspond to viable amoebae and, after four years, only one participant reported stronger ocular problems. Nevertheless, more studies are necessary to corroborate this hypothesis.

Comparative proteomic analysis of extracellular secreted proteins expressed by two pathogenic Acanthamoeba castellanii clinical isolates and a non-pathogenic ATCC strain

Acanthamoeba keratitis (AK) is a serious ocular disease caused by pathogenic Acanthamoeba gaining entry through wounds in the corneal injury; generally, patients at risk for contracting AK wear contact lenses, usually over a long period of time. Moreover, pathogenic Acanthamoeba causes serious consequences: it makes the cornea turbid and difficult to operate on, including procedures such as enucleation of the eyeball. At present, diagnosis of this disease is not straightforward, and treatment is very demanding. We have established the comparative transcriptome and extracellular secreted proteomic database according to the non-pathogenic strain ATCC 30010 and the pathogenic strains NCKU_B and NCKU_D. We identified 44 secreted proteins successfully, 10 consensus secreted proteins and 34 strain-specific secreted proteins. These proteins may provide targets for therapy and immuno-diagnosis of Acanthamoeba infections. This study shows a suitable approach to identify secreted proteins in Acanthamoeba and provides new perspectives for the study of molecules potentially involved in the AK.

Genotypic, physiological, and biochemical characterization of potentially pathogenic Acanthamoeba isolated from the environment in Cairo, Egypt

Acanthamoebae are the most common opportunistic amphizoic protozoa that cause life-threatening granulomatous amoebic encephalitis in immunocompromised individuals and sight-threatening amoebic keratitis (AK) in contact lens wearers. The present work aimed to determine the presence of Acanthamoeba isolates in different environmental sources: water, soil, and dust in Cairo, Egypt and to characterize the pathogenic potential of the isolated Acanthamoeba using physiological and biochemical assays as well as determination of the genotypes in an attempt to correlate pathogenicity with certain genotypes. The study included the collection of 22 corneal scrapings from patients complaining of symptoms and signs indicative of acanthamoeba keratitis (AK) and 75 environmental samples followed by cultivation on non-nutrient agar plates preseeded with E. coli. Positive samples for Acanthamoeba were subjected to osmo- and thermo-tolerance assays and zymography analysis. Potentially pathogenic isolates were subjected to PCR amplification using genus-specific primer pair. Isolates were classified at the genotype level based on the sequence analysis of Acanthamoeba 18S rRNA gene (diagnostic fragment 3). The total detection rate for Acanthamoeba in environmental samples was 33.3 %, 31.4 % in water, 40 % in soil, and 20 % in dust samples. Three and two Acanthamoeba isolates from water and soil sources, respectively, had the potential for pathogenicity as they exhibited full range of pathogenic traits. Other 12 isolates were designated as weak potential pathogens. Only ten of the environmental isolates were positive in PCR and were classified by genotype analysis into T4 genotype (70 %), T3 (10 %) and T5 (20 %). Potential pathogens belonged to genotypes T4 (from water) and T5 (from soil) while weak potential pathogens belonged to genotypes T3 (from water) and T4 (from water and soil). Additionally, T7 genotype was isolated from keratitis patients. There is a considerable variation in the response of Acanthamoeba members of the same genotype to pathogenicity indicator assays making correlation of pathogenicity with certain genotypes difficult. Presence of potentially pathogenic Acanthamoeba isolates in habitats related directly to human populations represent a risk for human health. Isolation of Acanthamoeba genotype T7 from AK cases, which is commonly considered as nonpathogenic, might draw the attention to other Acanthamoeba genotypes considered as non pathogenic and reevaluate their role in production of human infections. To our knowledge, this is the first study on the presence and distribution of Acanthamoeba genotypes in the environment, Cairo, Egypt.

Identification of coagulase-negative staphylococci in daily disposable contact lens wearers

This study aimed to identify and quantify the number of contaminating organisms on daily disposable (DD) soft contact lenses, which may be responsible for mild cases of keratitis that occur with this lens wear modality. Ten participants wore DD lenses, and 10 participants wore planned replacement (PR) lenses. Lenses were collected aseptically and analysed for microbial contamination. Colony-forming units (CFU) were recorded, and representative colonies were used for identification using the API identification system. The DD lenses evaluated in this study were contaminated with coagulase-negative staphylococcus (CNS), ranging from 1 to 653 CFU. PR lenses showed more diversity in the types of contaminating micro-organisms and consisted of CNS, Gram-negative bacteria (Pseudomonas), a yeast (Candida) and a mould (Aspergillus), ranging from 1 to 230 CFU. CNS was the only type of micro-organism found on DD contact lenses and therefore may be the cause of any form of keratitis observed in DD lens wearers.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study to determine the frequency and identify the contaminating organisms found on daily disposable (DD) soft contact lenses. The contaminating organisms identified on DD contact lenses were solely coagulase-negative staphylococcus (CNS), suggesting that CNS may be the causative organism associated with infectious keratitis that occurs with DD contact lens wear.

Acanthamoeba protease activity promotes allergic airway inflammation via protease-activated receptor 2

Acanthamoeba is a free-living amoeba commonly present in the environment and often found in human airway cavities. Acanthamoeba possesses strong proteases that can elicit allergic airway inflammation. To our knowledge, the aeroallergenicity of Acanthamoeba has not been reported. We repeatedly inoculated mice with Acanthamoeba trophozoites or excretory-secretory (ES) proteins intra-nasally and evaluated symptoms and airway immune responses. Acanthamoeba trophozoites or ES proteins elicited immune responses in mice that resembled allergic airway inflammation. ES proteins had strong protease activity and activated the expression of several chemokine genes (CCL11, CCL17, CCL22, TSLP, and IL-25) in mouse lung epithelial cells. The serine protease inhibitor phenyl-methane-sulfonyl fluoride (PMSF) inhibited ES protein activity. ES proteins also stimulated dendritic cells and enhanced the differentiation of naive T cells into IL-4-secreting T cells. After repeated inoculation of the protease-activated receptor 2 knockout mouse with ES proteins, airway inflammation and Th2 immune responses were markedly reduced, but not to basal levels. Furthermore, asthma patients had higher Acanthamoeba-specific IgE titers than healthy controls and we found Acanthamoeba specific antigen from house dust in typical living room. Our findings suggest that Acanthamoeba elicits allergic airway symptoms in mice via a protease allergen. In addition, it is possible that Acanthamoeba may be one of the triggers human airway allergic disease.

A year long study of the presence of free living amoeba in Spain

Free-living amoeba such as Acanthamoeba and Balamuthia mandrillaris can act as opportunistic parasites on a wide range of vertebrates and they are becoming a serious threat to human health due to the resistance of their cysts to harsh environmental conditions, disinfectants, some water treatment practices and their ubiquitous distribution. This work was carried out in order to study the presence of these free-living amoebae (FLA) and their possible seasonality in a continental-Mediterranean climate in different types of water. For this purpose, a total of 223 water samples were collected during one year from four drinking water treatment plants (DWTP), seven wastewater treatment plants (WWTP) and six locations of influence (LI) on four river basins from Spain. Water samples were concentrated using the IDEXX Filta-Max(®) system and analyzed by a triplex real time PCR that detects Acanthamoeba, B. mandrillaris and Naegleria fowleri. Agar plates were also seeded for Acanthamoeba culture. From the three FLA studied, N. fowleri was not detected in any sample while B. mandrillaris was found at the entrance of a DWTP; this being, to our knowledge, the first report of these protozoa in water worldwide. On the other hand, the presence of Acanthamoeba observed was higher, 94.6% of the studied points were positive by real time PCR and 85.2% by culture, resulting in 99.1% positive for Acanthamoeba with both methods. All genetically analyzed Acanthamoeba were genotype T4 but nine different T4/DF3 sequences were observed, three of them being described for the first time, assigning new codes. No seasonal distribution of Acanthamoeba was found. These facts should serve as a warning to contact lens wearers of the risk of a poor hygiene when handling their contact lenses. It should also serve as a signal to physicians to consider FLA as a possible causative agent of nervous system infections as well as Acanthamoeba keratitis due to their high environmental presence shown in this study.

Non-contact lens use-related Acanthamoeba keratitis in southern Turkey: evaluation of risk factors and clinical features

PURPOSE

To assess the diagnostic methods, risk factors, and clinical features of Acanthamoeba keratitis cases in patients who do not wear contact lenses.

METHODS

Medical records of 26 consecutive patients with non-contact lens-related Acanthamoeba keratitis, who were followed up at the tertiary eye care center between May 2010 and May 2012, were analyzed. Laboratory, demographic, and clinical findings were evaluated pertaining to the patients.

RESULTS

Twenty-six non-contact lens-related Acanthamoeba keratitis cases were included in the study. The main risk factors were trauma (group 1, n = 13 patients) and ocular surface disease (group 2, n = 12 patients). One patient had both of the risk factors mentioned above. Overall test results showed that Acanthamoeba positivity rates were 15.3% for direct microscopy, 46.1% for culture, 92.3% for conventional polymerase chain reaction (PCR), and 100% for real-time PCR. The rates of full-thickness corneal involvement and ring-shaped infiltrations were higher in group 2, whereas superficial keratitis and radial keratoneuritis were higher in group 1. The final visual acuities were significantly better in group 1 than group 2 (p<0.025).

CONCLUSIONS

This study is the first regional report from Turkey about Acanthamoeba keratitis in non-contact lens users. A majority of cases admitted to a tertiary eye care center were related to trauma or ocular surface disease. Physician suspicion is critically important for the timely diagnosis of these cases. At this point, molecular diagnostic tests (PCR or real-time PCR) seem to support the clinical diagnosis of Acanthamoeba keratitis with the help of fast and reliable results.

Morpho-Physiological and Biochemical Criteria of Acanthamoeba spp. Isolated from the Egyptian Aquatic Environment

BACKGROUND

The free-living amoebae Acanthamoeba spp., have been recognized as etiologic agents of amoebic encephalitis, keratitis, otitis, lung lesions and other skin infections mainly in immuno-compromised individuals. In this study, morpho-physiological and biochemical characterization of Acanthamoeba strains isolated from the Egyptian aquatic environment were surveyed.

METHODS

Some Acanthamoeba species were cultivated on non-nutrient agar. Isolated strains of Acanthamoeba were identification based on the morphology of trophic and cyst forms in addition to temperature and osmo-tolerance assays. Biochemical characterization of the isolated amoeba strains was performed using quantitative assay as well as qualitative determination of proteolytic activity in zymograph analysis.

RESULTS

Potentially pathogenic Acanthamoeba species were isolated from all of the examined water sources. Colorimetric assays showed protease activity in the heat-tolerant isolates of Acanthamoeba. All pathogenic isolates of Acanthamoeba exhibited higher protease activity than did the non-pathogenic ones. The zymographic protease assays showed various banding patterns for different strains of Acanthamoeba.

CONCLUSION

The incidence and prevalence of the pathogenic Acanthamoeba species in the aquatic environment using parasitological and biochemical diagnostic tools will provide baseline data against which the risk factors associated with waterborne transmission can be identified.

Amoebicidal effects of contact lens disinfecting solutions

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.

Evaluation of microbial contamination and distribution of sulphate-reducing bacteria in dental units

Although bacterial contamination is widely researched in dental unit water systems, we have been unable to find any published reports to date about the presence and distribution of sulphate-reducing bacteria (SRB) in dental unit waterlines (DUWLs). The aim of this study was to evaluate microbial contamination and to determine the presence and distribution of SRB in DUWLs. One hundred twenty-three water samples were collected from the air-water syringes, high-speed drills and water sources from 41 dental units in Istanbul, Turkey. The counts of aerobic heterotrophic bacteria and SRB were investigated in the water samples. In addition, the presence of free-living amoebae (FLA) was examined. In this work, we evaluated microbial contamination and reported for the first time the distribution of SRB in DUWLs. We determined that only ten out of 123 water samples were able to meet the American Dental Association's limit (≤200 CFU ml( - 1)). SRB were observed in 102 out of 123 samples (82.9%). In addition, SRB were detected in all of the air-water syringes and high-speed drills. FLA were established in 103 out of 123 samples (83.7%).

Isolation and genotyping of acanthamoeba strains from environmental sources in ahvaz city, khuzestan province, southern iran

BACKGROUND

Acanthamoeba spp. are free-living amoebae commonly found in the environmental sources such as water, soil, and air. This ubiquitous amoeba is the causative agent of amoebic keratitis (AK). The objective of the present study was to investigate the presence of Acanthamoeba spp. in water and soil sources in Ahvaz City, Khuzestan Province, southern Iran.

METHODS

In general, 110 samples of water and soil were taken from different localities of Ahvaz including agricultural canals, rivers, and swimming pools. Filtration and cultivation were carried out on non-nutrient agar medium (NNA). Axenic cultivation was performed for all of positive isolates. PCR analysis was conducted on positive samples. Sequencing was done for 15 PCR products. Genotypes were identified by Blast search and homology analysis.

RESULTS

Acanthamoeba spp. was found in 43 (71.6%) of samples of water and 13 (26%) soil samples. Genotyping of 15 samples proved that Acanthamoeba belonged to T4 (86.6%), T2 (6.6%), and T5 (6.6%) genotypes.

CONCLUSION

TYI-S-33 medium could be better than PYG medium for Acanthamoeba axenic culture.

Adherence of acanthamoeba to lens cases and effects of drying on survival

PURPOSE

To compare the effects of drying the lens case with tissue on the presence of Acanthamoeba with cases left wet and to determine adherence to the lens case of varying concentrations of Acanthamoeba suspensions. The effect of drying on viability of Acanthamoeba in new, used, and soiled lens cases was compared over a 24 h period.

METHODS

New (16) and scratched (16) lens cases were rinsed with a range of Acanthamoeba suspensions. Eight of each group were dried with tissue and the presence of Acanthamoeba was determined in all cases using polymerase chain reaction. To examine effects of drying, forty-two lens case wells were scratched to simulate use and 21 of these were artificially soiled with serum Bovine albumin. These cases and a further 21 unused wells were contaminated with Acanthamoeba (×10/ml) and then left to dry in a cool, dry environment. Three wells of each group were sampled at time 0, 2, 4, 6, 8, 12, and 24 h, and the number of viable Acanthamoeba were determined.

RESULTS

Acanthamoeba were more likely to adhere to used than unused lens cases (p < 0.05). Detection of Acanthamoeba in wiped lens cases was at 2-log dilutions less than in cases left wet for both new and used lens cases. Adherence were significantly different between rinse and rinse/dried cases (p = 0.015). Air drying significantly reduced the numbers of viable amoebic cysts and trophozoites and the effect was time dependent. Survival was significantly higher in used and soiled wells.

CONCLUSIONS

Drying with tissue after rinsing significantly reduces numbers of adhering Acanthamoeba. Acanthamoeba were found to be able to adhere even to new unused cases, so the importance of proper cleaning and disinfection of lens cases cannot be underestimated. Air drying reduces viability but some viable cells were present at 24 h in soiled cases, confirming the role of biofilm in protecting organisms from desiccation.

Do free-living amoebae in treated drinking water systems present an emerging health risk?

There is an expanding body of evidence that free-living amoebae (FLA) increase both the numbers and virulence of water-based, human-pathogenic, amoeba-resisting microorganisms (ARM). Legionella spp., Mycobacterium spp., and other opportunistic human pathogens are known to be both ARM and also the etiologic agents of potentially fatal human lung infections. However, comparatively little is known about the FLA that may facilitate ARM growth in drinking water. This review examines the available literature on FLA in treated drinking water systems; in total 26 studies from 18 different countries. FLA were reported to breakthrough the water treatment barrier and enter distribution systems, in addition to the expected post-treatment system ingress. Once in the distribution system there is evidence of FLA colonization and regrowth especially in reservoirs and in-premise plumbing storage tanks. At the point of use the average FLA detection rate was 45% but highly variable (n = 16, σ = 31) due to both differences in both assay methods and the type of water systems examined. This review reveals that FLA are consistently detected in treated drinking water systems around the world and present a yet unquantified emerging health risk. However, more research is urgently required before accurate risks assessments can be undertaken to assess the impacts on human health, in households and institutions, due to exposure to FLA facilitated pathogenic ARM.

Isolation of acanthamoeba spp. From drinking waters in several hospitals of iran

BACKGROUND

Acanthamoeba is an opportunistic amphizoic protozoan found in different water sources including swimming pool as well as in sewage. The aim of this study was to investigate the prevalence of Acanthamoeba in tap-water samples in Iran.

METHOD

In this descriptive cross-sectional study, 94 samples of cold and warm tap-water were collected from different wards of hospitals in 13 cities of Iran in 2007-2008. Free residual chlorine, pH, and temperature of samples were measured. After filtration through multipore nylon membrane, samples were cultured on non-nutrient agar. Then we investigated existence of Acanthamoeba by reverse contrast phase microscope.

RESULTS

Acanthamoeba was found in 45 samples (48%). Thirty-four and 11 positive samples were collected from cold and warm tap water, respectively. The samples belonged to the category of 20-30°C temperature with 0-2 ppm free residual chlorine and pH 6-7.4 showed the most coincidence to the positive cases. The greatest proportion of positive samples was obtained from Mashhad hospitals, while all samples collected from Arak and Semnan hospitals were negative.

CONCLUSION

considering the results of this study and the pathogenic role of this protozoan on patients with immunodeficiency, as well as capability of this microorganism in carrying other pathogens such as Legionella, further studies are needed. What is more important, potable water in hospitals should follow the procedure of treatment and sanitation, in order to prevent the relevant nosocomial infections.

Acanthamoeba spp. in domestic tap water in houses of contact lens wearers in the metropolitan area of Mexico City

A survey was carried out in the metropolitan area of Mexico City to determine the presence of Acanthamoeba in the tap water of houses of contact lens wearers. Water samples were taken from the mains water entry, bathroom sinks and storage containers (roof tanks, cisterns) of 27 houses; and from the solution contained in the contact lens cases. Samples were filtered and cultured onto NNE medium. The isolates were identified based on their morphological features and pathogenicity. Total and fecal coliforms, water temperature, pH, dissolved oxygen and residual free-chlorine were measured by standard methods. Forty five isolates of Acanthamoeba from 200 water samples were obtained. The highest number of amoebae was isolated from cisterns and roof tanks. Most Acanthamoeba isolates were non-pathogenic, however, their presence in tap water is a potential hazard since some species can cause Acanthamoeba keratitis and granulomatous amoebic encephalitis.

Endosymbionts of Acanthamoeba isolated from domestic tap water in Korea

In a previous study, we reported our discovery of Acanthamoeba contamination in domestic tap water; in that study, we determined that some Acanthamoeba strains harbor endosymbiotic bacteria, via our molecular characterization by mitochondrial DNA restriction fragment length polymorphism (Mt DNA RFLP). Five (29.4%) among 17 Acanthamoeba isolates contained endosymbionts in their cytoplasm, as demonstrated via orcein staining. In order to estimate their pathogenicity, we conducted a genetic characterization of the endosymbionts in Acanthamoeba isolated from domestic tap water via 16S rDNA sequencing. The endosymbionts of Acanthamoeba sp. KA/WP3 and KA/WP4 evidenced the highest level of similarity, at 97% of the recently published 16S rDNA sequence of the bacterium, Candidatus Amoebophilus asiaticus. The endosymbionts of Acanthamoeba sp. KA/WP8 and KA/WP12 shared a 97% sequence similarity with each other, and were also highly similar to Candidatus Odyssella thessalonicensis, a member of the alpha-proteobacteria. The endosymbiont of Acanthamoeba sp. KA/WP9 exhibits a high degree of similarity (85-95%) with genus Methylophilus, which is not yet known to harbor any endosymbionts. This is the first report, to the best of our knowledge, to show that Methylophilus spp. can live in the cytoplasm of Acanthamoeba.

National outbreak of Acanthamoeba keratitis associated with use of a contact lens solution, United States

Premarket standardized testing for Acanthamoeba spp. is warranted.

An outbreak of Acanthamoeba keratitis, a rare, potentially blinding, corneal infection, was detected in the United States in 2007; cases had been increasing since 2004. A case–control study was conducted to investigate the outbreak. We interviewed 105 case-patients from 30 states and 184 controls matched geographically and by contact lens use. Available contact lenses, cases, solutions, and corneal specimens from case-patients were cultured and tested by molecular methods. In multivariate analyses, case-patients had significantly greater odds of having used Advanced Medical Optics Complete Moisture Plus (AMOCMP) solution (odds ratio 16.9, 95% confidence interval 4.8–59.5). AMOCMP manufacturing lot information was available for 22 case-patients, but none of the lots were identical. Three unopened bottles of AMOCMP tested negative for Acanthamoeba spp. Our findings suggest that the solution was not intrinsically contaminated and that its anti-Acanthamoeba efficacy was insufficient. Premarket standardized testing of contact lens solutions for activity against Acanthamoeba spp. is warranted.

18S ribosomal DNA genotypes of Acanthamoeba species isolated from contact lens cases in the Philippines

This study was carried out to document the genotypes of Acanthamoeba present in contact lens cases from 50 randomly selected contact lens wearers living in Quezon City, Metro Manila, Philippines. Acanthamoeba species were isolated from eight (16%) in 50 contact lens cases examined. We analyzed partial 18S ribosomal DNA (Rns) sequences of the eight isolates and found that the sequence differences were sufficient to distinguish the genotypes. After the isolates were genotyped, using the Basic Local Alignment Search Tool program, their phylogenetic positions relative to known Acanthamoeba isolates were determined. The model-based (GTR+Gamma+Iota) neighbor-joining, maximum likelihood, and Bayesian inference analyses, as well as the non-model-based maximum parsimony analysis were used. Results showed that of the eight isolates, six were Rns genotype T5 while two were Rns genotype T4. This present study indicates that genotype T5 is also a common contaminant in contact lens storage cases.

The relative value of confocal microscopy and superficial corneal scrapings in the diagnosis of Acanthamoeba keratitis

PURPOSE

To compare the relative diagnostic value of confocal microscopy and superficial corneal cultures in the diagnosis of Acanthamoeba keratitis by using clinical and microbiologic definitions of disease.

METHODS

Results of confocal microscopy, superficial corneal smear, and superficial corneal culture were analyzed for validity against 2 different microbiologic and a clinical composite standard for Acanthamoeba keratitis.

RESULTS

In patients with both clinical characteristics and objective evidence of Acanthamoeba keratitis, confocal microscopy exhibited a sensitivity of 90.6% (95% confidence interval [CI]: 79.3%-96.9%) and a specificity of 100% (95% CI: 95.0%-100%). In patients with either positive culture or smear evidence of Acanthamoeba keratitis, confocal microscopy showed a sensitivity of 90.9% (95% CI: 78.3%-97.5%) and specificity of 90.1% (95% CI: 81.5%-95.6%). In strictly culture-positive patients, confocal microscopy showed a sensitivity of 92.9% (95% CI: 76.5%-99.1%) and a specificity of 77.3% (95% CI: 67.7%-85.2%). Of the 53 patients with Acanthamoeba keratitis, confocal microscopy was positive in 48 patients, whereas corneal smears and cultures were positive in 30 of 41 and 23 of 42 patients, respectively. Sensitivity of Acanthamoeba culture was 52.8% (95% CI: 38.6%-66.7%) in patients with a clinical diagnosis of Acanthamoeba keratitis. Simultaneous testing of smear and superficial corneal scraping resulted in a sensitivity of 83.0% (95% CI: 70.2%-91.9%), independent of the results of confocal microscopy.

CONCLUSIONS

As confocal microscopy comes into wider clinical use, it remains in need of clinical and pathologic correlation. When performed and interpreted by an experienced operator, confocal microscopy is both sensitive and specific in the diagnosis of Acanthamoeba keratitis. Contemporaneous corneal scrapings are independently sensitive in the detection of Acanthamoeba keratitis, and a combination of both diagnostic modalities offers the highest likelihood of rapidly and accurately diagnosing Acanthamoeba keratitis in patients with atypical keratitis.