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

Epidemiology of and Genetic Factors Associated with Acanthamoeba Keratitis

Acanthamoeba keratitis (AK) is a severe, rare protozoal infection of the cornea. Acanthamoeba can survive in diverse habitats and at extreme temperatures. AK is mostly seen in contact lens wearers whose lenses have become contaminated or who have a history of water exposure, and in those without contact lens wear who have experienced recent eye trauma involving contaminated soil or water. Infection usually results in severe eye pain, photophobia, inflammation, and corneal epithelial defects. The pathophysiology of this infection is multifactorial, including the production of cytotoxic proteases by Acanthamoeba that degrades the corneal epithelial basement membrane and induces the death of ocular surface cells, resulting in degradation of the collagen-rich corneal stroma. AK can be prevented by avoiding risk factors, which includes avoiding water contact, such as swimming or showering in contact lenses, and wearing protective goggles when working on the land. AK is mostly treated with an antimicrobial therapy of biguanides alone or in combination with diaminidines, although the commercial availability of these medicines is variable. Other than anti-amoeba therapies, targeting host immune pathways in Acanthamoeba disease may lead to the development of vaccines or antibody therapeutics which could transform the management of AK.

Epidemiological profile of microbial keratitis in Alexandria-Egypt a 5 years retrospective study

OBJECTIVE

To evaluate the epidemiologic profile of microbial keratitis in Alexandria- Egypt, with special emphasis on risk factors, visual outcome and microbiological results.

METHODS

This retrospective study reviewed files of patients treated for microbial keratitis during a period of 5 years at Alexandria Ophthalmology Hospital Cornea Clinic, Alexandria- Egypt, between February 2017 and June 2022. The patients were evaluated for the risk factors e.g., trauma, eyelid disorders, co-morbidities, and contact lens use. They were also evaluated for their clinical picture, the identified microorganisms, visual outcomes, and complications. Non-microbial keratitis and incomplete files were excluded from the study.

RESULTS

A total of 284 patients were diagnosed as microbial keratitis in our study. Viral keratitis was the most common cause of microbial keratitis (n = 118 (41.55%)), followed by bacterial keratitis (n = 77 (27.11%)), mixed keratitis (n = 51 (17.96%)), acanthamoeba keratitis (n = 22 (7.75%)) and the least cause was fungal keratitis (n = 16 (5.63%)). Trauma was the most common risk factor for microbial keratitis (29.2%). Fungal keratitis had a statistically significant association with trauma (p < 0.001), while the use of contact lenses had a statistically significant association with Acanthamoeba keratitis (p < 0.001). The percentage of culture-positive results in our study was 76.8%. Gram-positive bacteria were the most frequently isolated bacterial isolate (n = 25 (36.2%)), while filamentous fungi were the most frequently isolated fungi (n = 13(18.8%)). After treatment, there was a significant increase in the mean visual acuity among all groups; it was significantly higher in Acanthamoeba keratitis group with a mean difference of 0.262 ± 0.161 (p = 0.003).

CONCLUSION

Viral keratitis followed by bacterial keratitis were the most frequent etiologic agents causing microbial keratitis found in our study. Although trauma was the most frequent risk factor for microbial keratitis, contact lens wear was found an important preventable risk factor for microbial keratitis in young patients. Performing culture properly whenever indicated before starting antimicrobial treatment increased the cultures' positive results.

Clinical and molecular diagnosis of Acanthamoeba keratitis in contact lens wearers in southern Brazil reveals the presence of an endosymbiont

Acanthamoeba keratitis (AK) is an infection that is mostly observed in contact lens wearers. It is often misdiagnosed causing delays in the administration of the correct treatment. The aim of this study was to report the outcome of clinical and molecular diagnosis of AK cases during the summer of 2019 in the southern region of Brazil. Three suspected cases of AK were discovered after an ophthalmic examination at a public hospital in the city of Porto Alegre. These cases were then confirmed through laboratory diagnosis (cell culture and molecular analysis by PCR and sequencing). In each of the three clinical sample cell cultures of corneal scraping and molecular analysis confirmed the presence of Acanthamoeba spp., all belonging to the morphological group II and to the genotype T4, which is the most common genotype associated with AK. In addition, Acanthamoeba spp. isolated from one of the clinical samples was found to harbor the Candidatus Paracaedibacter acanthamoeba, a bacterial endosymbiont. The presence of Ca. Paracaedibacter acanthamoeba in clinical isolates requires further research to reveal its possible role in the pathogenicity of Acanthamoeba infections.

Contact lenses contamination by Acanthamoeba spp. in Upper Egypt

Background

Acanthamoeba spp. are one of the free-living amoeba that spread worldwide causing keratitis. Owing to the increase in the use of lenses, whether for medical or cosmetic purposes, the incidence of disease increases every year. Contamination of the lenses with the Acanthamoeba trophozoites or cysts may lead to eye infection and cause sight-threatening keratitis in human. We isolated Acanthamoeba spp. from new lenses, used lenses, and contact lens disinfecting solutions and identified them based on morphological characteristics and molecular test.

Methods

New and used lenses and contact lens disinfecting solutions were cultured on monogenic media. Light and scanning electron microscope was used to identify Acanthamoeba spp. morphological features. Genotype identification was also evaluated using PCR sequencing of 18S rRNA gene specific primer pair JDP1 and JDP2.

Results

A hundred samples were examined, 29 (29%) were infected with Acanthamoeba spp. That belonged to two strains of Acanthamoeba (Acanthamoeba 41 and Acanthamoeba 68). 18S rRNA of the Acanthamoeba 41 had 99.69% sequence identity to Acanthamoeba castellanii clone HDU-JUMS-2, whereas Acanthamoeba 68 had 99.74% similar pattern to that of Acanthamoeba sp. isolate T4 clone ac2t4 that are morphologically identified as Acanthamoeba polyphaga. The obtained data revealed that the isolated strains belong to T4 genotype that was evolutionarily similar to strains isolated in Iran.

Conclusions

Cosmetic lenses and disinfectant solutions are a major transmissible mode for infection. This genotype is common as the cause of Acanthamoeba keratitis. To avoid infection, care must be taken to clean the lenses and their preservative solutions and prevent contamination with the parasite.

Acanthamoeba keratitis in contact lens wearers in a tertiary center of Tunisia, North Africa

PURPOSE

To analyze the epidemiological and clinical features of Acanathamoeba keratitis AK and to assess the risk factors of this corneal infection in contact lens CL wearers in a tertiary center of Tunisia, North Africa.

METHODS

We carried out a retrospective study between January 2008 and December 2019 in the ophthtalmology department of a referral center, Sousse, Tunisia. A review of the chart of 248 patients using CL and diagnosed with presumed infectious keratitis was done.Socio demographic, risk behaviors and microbiological findings in case of AK were analyzed. The mean follow-up was 18 months (1 month-4 years).

RESULTS

AK was diagnosed in 29 cases (11.7% of contact lens wearers with infectious keratitis). These 29 cases were analyzed. The mean age at the time of diagnosis was 33, 44 ± 26, 9 years. Almost of the patients (13; 44.82%) used soft monthly disposable contact lenses. Some risk behaviors related to contact lens wearing were found in our study like not washing and drying hands before CL wear, sleeping in CL, topping off, not respecting the adequate replacement frequency and showering or swimming in CL.After treatment, visual acuity improved only in 10 cases (34.48%), remained the same in 11 cases (37.93%) and worsened in 8 cases (27.58%).

CONCLUSION

Clinicians must suspect AK in each CL wearer with suggestive clinical signs to allow earlier treatment and better prognosis. Public prevention messages that encourage CL wearers to respect the hygiene rules should be broadly applicable to each person using any type of CL, to minimize the risk of AK.

Application of Dendrimers for Treating Parasitic Diseases

Despite advances in medical knowledge, parasitic diseases remain a significant global health burden and their pharmacological treatment is often hampered by drug toxicity. Therefore, drug delivery systems may provide useful advantages when used in combination with conventional therapeutic compounds. Dendrimers are three-dimensional polymeric structures, characterized by a central core, branches and terminal functional groups. These nanostructures are known for their defined structure, great water solubility, biocompatibility and high encapsulation ability against a wide range of molecules. Furthermore, the high ratio between terminal groups and molecular volume render them a hopeful vector for drug delivery. These nanostructures offer several advantages compared to conventional drugs for the treatment of parasitic infection. Dendrimers deliver drugs to target sites with reduced dosage, solving side effects that occur with accepted marketed drugs. In recent years, extensive progress has been made towards the use of dendrimers for therapeutic, prophylactic and diagnostic purposes for the management of parasitic infections. The present review highlights the potential of several dendrimers in the management of parasitic diseases.

Evaluation of Acanthamoeba keratitis cases in a tertiary medical care centre over 21 years

To report on Acanthamoeba keratitis cases in a tertiary university eye-hospital in Graz, Austria, over a 21-year period. Retrospective study. Parameters included demographics, diagnostics, clinical courses, medical therapies, surgical interventions, secondary complications, and best spectacle-corrected visual acuity (BSCVA). Patient records for 44 eyes of 42 patients were analysed; 2 bilateral infections. Mean age at presentation was 31 ± 13 (16-65) years; contact lenses were used in 41 of 44 eyes (93.2%). Symptoms at initial presentation were mainly pain (41/43, 95.3%) and photophobia (16/43, 37.2%). Most frequent morphological findings were stromal infiltrates (30/44, 68.2%). Diagnosis was mainly confirmed by smears (40/42, 95.2%) and polymerase chain reaction (8/42, 19%). Antiamoebic treatment comprised biguanides and diamidines. Penetrating keratoplasty was performed in 10/44 (22.7%) eyes. Median time from symptom onset to initial visit was 2 (0-26) weeks; median follow-up was 30 (2-1008) weeks. BSCVA improved in 23/36 (63.9%) eyes, remained unchanged in 6/36 (16.7%) eyes and deteriorated in 7/36 (19.4%) eyes. Acanthamoeba keratitis predominantly occurs in young contact lens wearers. Diagnosis should be considered in patients with pain and stromal infiltrates. In the majority of cases, BSCVA can be improved. Early diagnosis and adequate treatment should be implemented to prevent complications.

Presence and interaction of free-living amoebae and amoeba-resisting bacteria in water from drinking water treatment plants

Free-living amoebae (FLA) are ubiquitous and many isolates have been shown to be infected with amoeba-resisting bacteria, as the example of Acanthamoeba and Legionella interaction. Due to the high environmental prevalence of Acanthamoeba. in the Castilian Plateau (Spain), the aims of this work were to investigate the occurrence of Acanthamoeba and other FLA in water from several sampling points from four Drinking Water Treatment Plants (DWTP) and to investigate the presence of Legionella spp. and other amoeba-resisting bacteria in biofilms in raw and finished water, taking into account that no legislation exists for this protozoa control. Acanthamoeba was detected at different sampling points, and sand filters seemed to contribute to amoebic enrichment. After ozonation, a temporary decrease in viable amoebae was observed. The genotypes detected were T3, T4, and T5, revealing the first report of genotype T5 in waters from this region. Moreover, Balamuthia mandrillaris, Vermamoeba vermiformis and Paravahlkampfia sp. were detected. Regarding Legionella, PCR detection in raw and finished water was higher than by agar culture, but even higher after Acanthamoeba co-culture. Also, Legionella's presence was higher in raw water than in finished water. The decrease of free Legionella observed from raw (27.5%, by PCR) to finished water (3.4% by PCR) contrasted with the increase of Legionella-infected FLA from raw (30.7%) to finished water (52%). At biofilm, free Legionella was not detected, and the percentage of infected FLA was low (3.8%). Legionella species identified in these samples were L. drozanskii, L. donaldsonii and L. feeleii. Additionally, Acanthamoeba co-culture led to the isolation of Pseudomonas aeruginosa, P. stutzeri, P. fluorecens, Achromobacter xylosoxidans and Stenotrophomonas maltophilia. The highly disseminated presence of Acanthamoeba and the detection of amoeba-resisting bacteria inside amoebae highlight the importance of developing methods for controlling FLA in order to limit human pathogenic amoeba-resisting bacteria survival to the water purification processes.

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.

Acanthamoeba Keratitis and Acanthamoeba Conjunctivitis: A Case Report

Acanthamoeba species are vision-threatening agents by causing cornea infections known as Acanthamoeba keratitis. A 5 year-old kid with the complaints of erythema, eyelid edema, inflammation, limitation of eye movements in the right eye, and having no history of wearing contact lenses or trauma, was diagnosed of Acanthamoeba conjunctivitis through laboratory examinations in the Ophthalmology clinic. The visual sharpness of the patient improved after the treatment. A 44 year-old female patient suffering from pain, stinging, irritation, and inability to see in the left eye with the history of wearing contact lenses or trauma was diagnosed of Acanthamoeba keratitis through laboratory examinations. The agent was isolated and identified as "A. castellani" in the Genotype "T2". Examination of the left eye on the 15th day of treatment indicated that all complaints disappeared except for the cataract originated visual loss. However, the first diagnosis of Acanthamoeba keratitis appeared in the literature on a case with no history of wearing contact lenses and trauma it is found to be attention grabbing. We think that Acanthamoeba should not be ignored among microbial agents that cause eye infection with or without trauma and contact lens usage history.

Detection of Acanthamoeba spp. from dust phenomenon in Ilam Province, West Iran

In recent years, increasing dust phenomenon in the west of Iran has led to social, economic, and health concerns. This study aimed to represent the existence and genotyping of Acanthamoeba spp. in dust phenomenon in Ilam Province, Iran. In this study, 55 dust samples were collected and by targeting the diagnostic fragment 3 region of the 18S rRNA gene, the genotypes were determined. Utilizing the tolerance ability test, the pathogenic potential of all positive isolates was also recognized. Eighteen samples of Acanthamoeba (32.7%) were detected in the sampling areas. According to sequencing analysis, the isolates related to T4 (77.7%) and T2 (22.3%) genotypes were reported. It was revealed by thermo- and osmotolerance tests in which six strains are extremely pathogenic. To our knowledge, the pathogenic Acanthamoeba was potentially isolated initially from dust phenomenon in Ilam Province. Thus, these strains are probably highly virulent, and dusts are possible sources of Acanthamoeba infection in humans.

Acanthamoeba Keratitis: Current Status and Urgent Research Priorities

Background:

First discovered in the early 1970s, Acanthamoeba keratitis has remained a major eye infection and presents a significant threat to the public health, especially in developing countries. The aim is to present a timely review of our current understanding of the advances made in this field in a comprehensible manner and includes novel concepts and provides clear directions for immediate research priorities.

Methods:

We undertook a search of bibliographic databases for peer-reviewed research literature and also summarized our published results in this field.

Results:

The present review focuses on novel diagnostic and therapeutic strategies in details which can provide access to management and treatment of Acanthamoeba keratitis. This coupled with the recently available genome sequence information together with high throughput genomics technology and innovative approaches should stimulate interest in the rational design of preventative and therapeutic measures. Current treatment of Acanthamoeba keratitis is problematic and often leads to infection recurrence. Better understanding of diagnosis, pathogenesis, pathophysiology and therapeutic regimens, would lead to novel strategies in treatment and prophylaxis.

Identification and Genotypic Characterization of Potentially Pathogenic Acanthamoeba Isolated from Tap Water in Wuxi, China

Members of genus Acanthamoeba are widely distributed in the environment. Some are pathogenic and cause keratitis and fatal granulomatous amoebic encephalitis. In this study, we isolated an Acanthamoeba CJW/W1 strain from tap water in Wuxi, Jiangsu Province, China. Its 18S rDNA was sequenced and a phylogenetic tree was constructed. The isolated cysts belonged to morphologic group II. Comparison of 18S rDNA sequences of CJW/W1 strain and other isolates showed high similarity (99.7%) to a clinical isolate Asp, KA/E28. A phylogeny analysis confirmed this isolate belonged to the pathogenic genotype T4, the most common strain associated with Acanthamoeba-related diseases. This is the first report of an Acanthamoeba strain isolated from tap water in Wuxi, China. Acanthamoeba could be a public health threat to the contact lens wearers and, therefore, its prevalence should be monitored.

Concomitant inactivation of Acanthamoeba spp. and Escherichia coli using suspended and immobilized TiO2

This work reports the application of photocatalytic disinfection to the inactivation of Acanthamoeba trophozoites, a free-living pathogenic amoeba. Two types of photocatalytic reactors configurations have been used: i) a slurry reactor using suspended titanium dioxide (TiO₂); and, ii) a fixed-bed reactor using immobilized TiO₂ onto glass Raschig rings. The effect of the chemical composition of water has been analysed, comparing the efficiency of the process in deionized water (DW) and synthetic wastewater treatment plant effluent (SWTPE). The inactivation of Acanthamoeba spp. has been compared to that of Escherichia coli bacteria, being also analysed the concomitant inactivation of both microorganisms. Our results show that 99% of inactivation of E. coli and Acanthamoeba spp. can be achieved using photocatalysis in both reactor configurations, but interestingly, the kinetics of inactivation of both microorganisms together differs from that found with them separately. Particularly, E. coli seems to be more resistant to the inactivation in the presence of Acanthamoeba spp. which has been justified by the screen effect caused by the bigger size of Acanthamoeba spp. This observation is more pronounced in DW as the composition of the SWTPE prevent the microorganisms from suffering osmotic and/or mechanical stress and protect cellular structures to the attack of reactive oxygen species (ROS). On the other hand, the difference between the inactivation rate of E. coli and Acanthamoeba, points out the importance of the different inactivation mechanisms, suggesting that the entry of small TiO₂ particles into the cytoplasm of the Acanthamoeba cells provokes the attack of inner structures and as a consequence a faster inactivation. This mechanism is not possible when the catalyst is immobilized leading to a higher cell resistance to inactivation and consequently lower efficiency of the disinfection process.

Contact lens-related polymicrobial keratitis: Acanthamoeba spp. genotype T4 and Candida albicans

A 31-year-old female daily user of contact lenses sought medical attention, reporting blurred vision and irritation of the left eye. Slit-lamp examination revealed hyperemia and an irregular corneal epithelium surface, and empirical treatment was started. A corneal scrape was obtained and examined for the presence of fungi, bacteria, and Acanthamoeba spp. The results of the microbial culture revealed growth of Acanthamoeba spp. and Candida albicans. The Acanthamoeba isolate was characterized by cyst morphology as belonging to group II according to Pussard and Pons. Sequencing of the diagnostic fragment 3 (DF3) region located on the 18S ribosomal DNA identified the isolate as genotype T4. The patient was treated with chlorhexidine 0.02% and polyhexamethylene biguanide (PHMB) 0.02% drops for 5 months until the infection resolved. Lately, rare cases of polymicrobial keratitis associated with Acanthamoeba and Candida albicans have been reported. Cases of co-infection are more difficult to treat, since the specific treatment depends on precise identification of the agents involved.

Application of modified JDP-DGGE-based molecular genotyping method to predict Acanthamoeba genotype and to analyse community diversity in aquatic environments

Acanthamoeba spp. are ubiquitous, opportunistic potential human pathogens, causing granulomatous amoebic encephalitis and keratitis. They are classified as protozoa, and they include at least 20 different genotypes (T1-T20) based on variation in the 18S rRNA gene. Acanthamoeba spp. are diverse in their production of toxins and in their ability to resist environmental factors. Therefore, it is necessary to develop a rapid genotyping method for Acanthamoeba spp. in aquatic environments. Although the denaturing gradient gel electrophoresis (DGGE) method for analysing microbial genotypes is potentially useful for rapid identification of aquatic environmental species, the technique has been compromised by artificial DGGE profiles in which many DNA fragments of identical sequences are segregated and displayed as different bands. The results indicate that PCR-DGGE genotyping with a GC clamp results in many segregated weaker bands of identical DNA sequences. In contrast, PCR-DGGE genotyping without a GC clamp displays genotype-dependent patterns in the major bands. Thus, DGGE without a GC clamp was performed to compare genotyping efficiency for Acanthamoeba in 21 water samples from rivers and reservoirs in Taiwan. Among them, four samples were found to demonstrate a banding pattern with more than one major band, and these band profiles of major bands were identical to those of positive controls. DNA cloning further confirmed that the sequences of the major bands were identical. In conclusion, more than two genotypes of Acanthamoeba in the four samples were identified by this method, suggesting that PCR-DGGE genotyping without a GC clamp is a useful approach for studying the diversity of Acanthamoeba communities. Graphical abstract.