Advances in the management of Acanthamoeba keratitis: A review of the literature and synthesized algorithmic approach

Contact Lens-Related Corneal Infections

Our review provides an update on the current landscape of contact lens-associated microbial keratitis (MK). We discuss the prevalence and risk factors associated with MK, emphasizing the role of overnight wear, poor hygiene, and contact lens type. CL-related MK is commonly caused by bacteria, though can also be caused by fungi or protozoa. Clinical presentation involves ocular pain, redness, and vision loss, with more specific presenting symptoms based on the culprit organism. Treatment strategies encompass prevention through proper hygiene and broad-spectrum antibiotic, antifungal, or antiprotozoal therapy, with surgical management reserved for severe recalcitrant cases.

Identification of new targets for the diagnosis of cysts (four) and trophozoites (one) of the eye pathogen Acanthamoeba

Acanthamoebae , which are free-living amoebae, cause corneal inflammation (keratitis) and blindness, if not diagnosed and effectively treated. While trophozoites adhere to and damage the cornea, Acanthamoeba cysts, the walls of which contain cellulose and have two layers connected by conical ostioles, are the diagnostic form by microscopy of the eye or of corneal scrapings. We recently used structural and experimental methods to characterize cellulose-binding domains of Luke and Leo lectins, which are abundant in the inner layer and ostioles. However, no antibodies have been made to these lectins or to a Jonah lectin and a laccase, which are abundant in the outer layer. Here we used confocal microscopy to show that rabbit antibodies to recombinant Luke, Leo, Jonah, and laccase generally support localizations of GFP-tagged proteins in walls of transfected Acanthamoebae. Rabbit antibodies to all four wall proteins efficiently detected calcofluor white-labeled cysts of 10 of 11 Acanthamoeba isolates obtained from the ATCC, including five T4 genotypes that cause most cases of keratitis. Laccase shed into the medium during encystation was detected by an enzyme-linked immunoassay. We also used structural and experimental methods to characterize the mannose-binding domain of an Acanthamoeba mannose-binding protein and showed that rabbit antibodies to the mannose-binding domain efficiently detected trophozoites of all 11 Acanthamoeba isolates. We conclude that four wall proteins are all excellent targets for diagnosing Acanthamoeba cysts in the eye or corneal scrapings, while the mannose-binding domain is an excellent target for identifying trophozoites in cultures of corneal scrapings.

Importance

Free-living amoeba in the soil or water cause Acanthamoeba keratitis, which is diagnosed by identification of cysts by microscopy of the eye or of corneal scrapings, using calcofluor-white that unfortunately cross-reacts with fungi and plants. Alternatively, Acanthamoeba infections are diagnosed by identification of trophozoites in cultures of scrapings. Here we showed that rabbit antibodies to four abundant cyst wall proteins (Jonah, Luke, Leo, and laccase) each efficiently detect calcofluor-white-labeled cysts of 10 of 11 Acanthamoeba isolates obtained from the ATCC. Further, laccase released into the medium by encysting Acanthamoebae was detected by an enzyme-linked immunoassay. We also showed that rabbit antibodies to the mannose-binding domain of the Acanthamoeba mannose-binding protein, which mediates adherence of trophozoites to keratinocytes, efficiently identifies trophozoites of all 11 ATCC isolates. In summary, four wall proteins and the ManBD appear to be excellent targets for diagnosis of Acanthamoeba cysts and trophozoites, respectively.

Human Conjunctival Transcriptome in Acanthamoeba Keratitis: An Exploratory Study

PURPOSE

The purpose of this study was to identify conjunctival transcriptome differences in patients with Acanthamoeba keratitis compared with keratitis with no known associated pathogen.

METHODS

The host conjunctival transcriptome of 9 patients with Acanthamoeba keratitis (AK) is compared with the host conjunctival transcriptome of 13 patients with pathogen-free keratitis. Culture and/or confocal confirmed Acanthamoeba in 8 of 9 participants with AK who underwent metagenomic RNA sequencing as the likely pathogen. Cultures were negative in all 13 cases where metagenomic RNA sequencing did not identify a pathogen.

RESULTS

Transcriptome analysis identified 36 genes differently expressed between patients with AK and patients with presumed sterile, or pathogen-free, keratitis. Gene enrichment analysis revealed that some of these genes participate in several biologic pathways important for cellular signaling, ion transport and homeostasis, glucose transport, and mitochondrial metabolism. Notable relatively differentially expressed genes with potential relevance to Acanthamoeba infection included CPS1 , SLC35B4 , STEAP2 , ATP2B2 , NMNAT3 , and AKAP12 .

CONCLUSIONS

This research suggests that the local transcriptome in Acanthamoeba keratitis may be sufficiently robust to be detected in the conjunctiva and that corneas infected with Acanthamoeba may be distinguished from the inflamed cornea where no pathogen was identified. Given the low sensitivity for corneal cultures, identification of differentially expressed genes may serve as a suggestive transcriptional signature allowing for a complementary diagnostic technique to identify this blinding parasite. Knowledge of differentially expressed genes may also direct investigation of disease pathophysiology and suggest novel pathways for therapeutic targets.

The Pathology of the Brain Eating Amoeba Naegleria fowleri

The genus Naegleria is a taxonomic subfamily consisting of 47 free-living amoebae. The genus can be found in warm aqueous or soil habitats worldwide. The species Naegleria fowleri is probably the best-known species of this genus. As a facultative parasite, the protist is not dependent on hosts to complete its life cycle. However, it can infect humans by entering the nose during water contact, such as swimming, and travel along the olfactory nerve to the brain. There it causes a purulent meningitis (primary amoebic meningoencephalitis or PAME). Symptoms are severe and death usually occurs within the first week. PAME is a frightening infectious disease for which there is neither a proven cure nor a vaccine. In order to contain the disease and give patients any chance to survival, action must be taken quickly. A rapid diagnosis is therefore crucial. PAME is diagnosed by the detection of amoebae in the liquor and later in the cerebrospinal fluid. For this purpose, CSF samples are cultured and stained and finally examined microscopically. Molecular techniques such as PCR or ELISA support the microscopic analysis and secure the diagnosis.

Rethinking Keratoplasty for Patients with Acanthamoeba Keratitis: Early "Low Load Keratoplasty" in Contrast to Late Optical and Therapeutic Keratoplasty

BACKGROUND

Early therapeutic penetrating keratoplasty (TKP) for Acanthamoeba keratitis (AK) is thought to have a worse visual prognosis than the delayed optical penetrating keratoplasty (OKP) after successful conservative treatment of AK. This has led to a tendency to prolong conservative therapy and delay penetrating keratoplasty in patients with AK. This retrospective series presents the results of patients with AK that underwent early penetrating keratoplasty after reducing the corneal amoeba load through intensive conservative therapy, so-called "low load keratoplasty" (LLKP).

PATIENTS AND METHODS

The medical records of our department were screened for patients with AK, confirmed by histological examination and/or PCR and/or in vivo confocal microscopy, which underwent ab LLKP and had a follow-up time of at least one year between 2009 and 2023. Demographic data, best corrected visual acuity (BCVA) and intraocular pressure at first and last visit, secondary glaucoma (SG), and recurrence and graft survival rates were assessed.

RESULTS

28 eyes of 28 patients were included. The average time from initiation of therapy to penetrating keratoplasty (PKP) was 68 ± 113 days. The mean follow-up time after LLKP was 53 ± 42 months. BCVA (logMAR) improved from 1.9 ± 1 pre-operatively to 0.5 ± 0.6 at last visit (p < 0.001). A total of 14% of patients were under medical therapy for SG at the last visit, and two of them underwent glaucoma surgery. The recurrence rate was 4%. The Kaplan-Meier graft survival rate of the first graft at four years was 70%. The second graft survival rate at four years was 87.5%.

CONCLUSION

LLKP appears to achieve a good visual prognosis with an earlier visual and psychological habilitation, as well as low recurrence and SG rates. These results should encourage us to reconsider the optimal timing of PKP in therapy-resistant AK.

Perspectives on the Incidence of Acanthamoeba Keratitis: A Systematic Review and Meta-Analysis

TOPIC

To provide an overview on the incidence of Acanthamoeba keratitis (AK).

CLINICAL RELEVANCE

Although being a sight-threatening cause of infectious keratitis, a comprehensive assessment of the incidence of AK is lacking.

METHODS

Incidence of AK was computed as the number of eyes with AK per health care center, per year (annualized center incidence [ACI]). Two meta-analytical ratios also were calculated: (1) the ratio of eyes with AK to the count of eyes with nonviral microbial keratitis (MK) and (2) the ratio of eyes with AK to the overall population (i.e., the total number of people in a nation or region, as indicated by the authors in each study). Center was defined as the health care facility where the study took place. Actual and projected estimates of the number of eyes with AK in years were calculated multiplying the ratio of eyes with AK to the total population and the corresponding population estimates, sourced from the United Nations Population Prospects.

RESULTS

Overall, 105 articles were included, published between 1987 and 2022. The total number of eyes identified was 91 951, with 5660 eyes affected by AK and 86 291 eyes affected by nonviral MK. The median ACI was 1.9 eyes with AK per health care center per year (95% confidence interval [CI], 1.5-2.6 eyes), with no statistically significant differences among continents. The ratio of eyes with AK to the total number of eyes with MK was 1.52% (95% CI, 1.03%-2.22%), whereas the ratio of eyes with AK in relationship to the entire population was estimated at 2.34 eyes per 1 000 000 people (95% CI, 0.98-5.55 per 1 000 000 people). The projected increase in the numbers of eyes with AK indicated an increase of 18.5% (n = 15 355 eyes with AK) in 2053 and 25.5% (n = 16 253 eyes with AK) in 2073, compared with the baseline of 2023 (n = 12 953 eyes with AK).

DISCUSSION

Acanthamoeba keratitis emerged as a relatively low-incident disorder, and no significant differences in terms of its incidence were found among different continents.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

A Comprehensive Review on Acanthamoeba Keratitis: An Overview of Epidemiology, Risk Factors, and Therapeutic Strategies

Acanthamoeba keratitis (AK) is a rare but severe corneal infection caused by the free-living amoeba, Acanthamoeba, which is ubiquitously present in the environment. This condition predominantly affects contact lens wearers but can also occur in non-lens users, particularly those exposed to contaminated water or with compromised immune systems. AK is characterized by progressive corneal inflammation, epithelial defects, and ulceration, which can lead to significant visual impairment or blindness if not promptly diagnosed and treated. This review aims to provide a comprehensive overview of AK by synthesizing current knowledge on its epidemiology, risk factors, pathophysiology, clinical manifestations, diagnostic approaches, and therapeutic strategies. The review also highlights preventive measures and public health strategies to reduce the incidence of this debilitating condition. A detailed examination of existing literature was conducted, focusing on the global incidence of AK, demographic trends, and various risk factors such as contact lens use, environmental exposures, and immunity status. The review also delves into the pathophysiology of Acanthamoeba infection, the host immune response, and the challenges in distinguishing AK from other forms of infectious keratitis. Therapeutic strategies, including medical and surgical interventions, are analyzed, along with emerging treatments. The global incidence of AK has increased, particularly among contact lens users, due to poor hygiene practices and environmental exposures. Early diagnosis remains challenging, often leading to delayed treatment and poorer outcomes. Biguanides and diamidines are the mainstays of medical therapy, with surgical options considered in advanced cases. Emerging therapies, such as photodynamic therapy and antimicrobial peptides, show promise in enhancing treatment outcomes. AK poses a significant threat to ocular health due to its potential for severe visual impairment and the complexities associated with its diagnosis and treatment. Early recognition, appropriate management, and public health initiatives focused on prevention are crucial for improving patient outcomes. Ongoing research and a collaborative approach among healthcare providers are essential to advancing the understanding and management of AK.

Assessing PCR-Positive Acanthamoeba Keratitis-A Retrospective Chart Review

Ophthalmologists' diagnostic and treatment competence in Acanthamoeba keratitis varies widely. This investigator-initiated, retrospective, single-center chart review examined the electronic patient files regarding PCR-positive Acanthamoeba keratitis. We included corneal and contact lens assessments. We further reviewed the patient's medical history, corneal scraping results regarding viral or fungal co-infections, and the duration from symptom onset to final diagnosis. We identified 59 eyes of 52 patients from February 2010 to February 2023, with 31 of 52 (59.6%) being female patients. The median (IQR, range) patient age was 33 (25.3 to 45.5 [13 to 90]) years, and the mean (SD, range) time to diagnosis after symptom onset was 18 (10.5 to 35 [3 to 70]) days. Overall, 7 of 52 (7.7%) patients displayed a bilateral Acanthamoeba infection, and 48 (92.3%) used contact lenses at symptom onset. Regarding other microbiological co-infections, we found virologic PCR testing in 45 of 52 (86.5%) patients, with 3 (6.7%) positive corneal scrapings. Fungal cultures were performed in 49 of 52 (94.2%) patients, with 5 (10.2%) positive corneal scrapings. The medical treatment success rate was 45/46 (97.8%). This study raises awareness of patient education in contact lens handling and screens for further microbial co-infections in suspected Acanthamoeba cases.

Increasing incidence of contact-lens-related Acanthamoeba keratitis in a tertiary ophthalmology department in an Italian population

PURPOSE

The purpose of this paper is to report the increasing incidence of contact-lens related Acanthamoeba keratitis (AK) in a tertiary ophthalmology department in Umbria, central Italy.

METHODS

Observational and retrospective case series were carried out. A total of nine eyes with a diagnosis of AK were examined. All patients underwent a full slit lamp examination, in vivo confocal microscopy (IVCM) and corneal scraping. The IVCM was repeated at one and two-week and at one, three and six-month intervals. Samples of domestic tap water were also examined for PCR analysis. Patients were treated with levofloxacin0,5%, Polyhexamethylene biguanide 0.02%, and Propamidine Isetionate0,1%.

RESULTS

All patients were contact lens wearers. The average patient age was 27.75 (range 18-45), with three men and five women. The main clinical features were ciliary congestion, diffuse epitheliopathy with punctuated keratitis, multiple, small sub-epithelial, greyish, corneal infiltrates with epithelial defect, pseudodendritic corneal lesions, perineural infiltrates, corneal stromal cellularity, and stromal infiltrates. IVCM was indicative of Acanthamoeba in seven out of the nine eyes. All the positive IVCM images were section images showing double walled, bright-spot cysts with a clear chain-like arrangement of five or more cysts identified in three of the patients. PCR analysis of the water was negative in all cases.

CONCLUSION

Although PCR is the most common method used, the increased incidence of AK could mainly be related to a proper IVCM interpretation. A broad-spectrum antibiotic, such as levofloxacin might play a role in the early treatment of AK reducing the virulence of the amoeba.

Global prevalence of potentially pathogenic free-living amoebae in sewage and sewage-related environments-systematic review with meta-analysis

Free-living amoebae (FLA) include amphizoic microorganisms important in public health, widely isolated from air, water, and soil. However, its occurrence in sewage-related environments still needs to be systematically documented. This study summarizes the occurrence of FLA in sewage-related environments through a systematic review with meta-analysis. A total of 1983 scientific article were retrieved from different databases, of which 35 were selected and analyzed using a random effects forest plot model with a 95% confidence interval (IC). The pooled overall prevalence of FLA in sewage across 12 countries was 68.96% (95% IC = 58.5-79.42). Subgroup analysis indicates high prevalence in all environments analyzed, including sewage water from the sewage treatment plant (81.19%), treated sewage water (75.57%), sewage-contaminated water (67.70%), sediment contaminated by sewage (48.91%), and sewage water (47.84%). Prevalence values of Acanthamoeba spp., Hartmanella/Vermamoeba spp., and Naegleria spp. are 47.48%, 28.24%, and 16.69%, respectively. Analyzing the species level, the distribution is as follows: Acanthamoeba palestinensis (88%), A. castellanii (23.74%), A. astronyxis (19.18%), A. polyphaga (13.59%), A. culbertsoni (12.5%), A. stevensoni (8.33%), A. tubiashi (4.35%) and A. hatchetti (1.1%), Naegleria fowleri (28.4%), N. gruberi (25%), N. clarki (8.33%), N. australiensis (4.89%) and N. italica (4.29%), Hartmannella/Vermamoeba exundans (40%) and H.V. vermiform (32.61%). Overall, our findings indicate a high risk associated with sewage-related environments, as the prevalence of FLA, including pathogenic strains, is high, even in treated sewage water. The findings of this study may be valuable both for risk remediation actions against amoebic infections and for future research endeavors.

The Orphan Drug for Acanthamoeba Keratitis (ODAK) Trial: PHMB 0.08% (Polihexanide) and Placebo versus PHMB 0.02% and Propamidine 0.1

PURPOSE

To compare topical PHMB (polihexanide) 0.02% (0.2 mg/ml)+ propamidine 0.1% (1 mg/ml) with PHMB 0.08% (0.8 mg/ml)+ placebo (PHMB 0.08%) for Acanthamoeba keratitis (AK) treatment.

DESIGN

Prospective, randomized, double-masked, active-controlled, multicenter phase 3 study (ClinicalTrials.gov identifier, NCT03274895).

PARTICIPANTS

One hundred thirty-five patients treated at 6 European centers.

METHODS

Principal inclusion criteria were 12 years of age or older and in vivo confocal microscopy with clinical findings consistent with AK. Also included were participants with concurrent bacterial keratitis who were using topical steroids and antiviral and antifungal drugs before randomization. Principal exclusion criteria were concurrent herpes or fungal keratitis and use of antiamebic therapy (AAT). Patients were randomized 1:1 using a computer-generated block size of 4. This was a superiority trial having a predefined noninferiority margin. The sample size of 130 participants gave approximately 80% power to detect 20-percentage point superiority for PHMB 0.08% for the primary outcome of the medical cure rate (MCR; without surgery or change of AAT) within 12 months, cure defined by clinical criteria 90 days after discontinuing anti-inflammatory agents and AAT. A prespecified multivariable analysis adjusted for baseline imbalances in risk factors affecting outcomes.

MAIN OUTCOME MEASURES

The main outcome measure was MCR within 12 months, with secondary outcomes including best-corrected visual acuity and treatment failure rates. Safety outcomes included adverse event rates.

RESULTS

One hundred thirty-five participants were randomized, providing 127 in the full-analysis subset (61 receiving PHMB 0.02%+ propamidine and 66 receiving PHMB 0.08%) and 134 in the safety analysis subset. The adjusted MCR within 12 months was 86.6% (unadjusted, 88.5%) for PHMB 0.02%+ propamidine and 86.7% (unadjusted, 84.9%) for PHMB 0.08%; the noninferiority requirement for PHMB 0.08% was met (adjusted difference, 0.1 percentage points; lower one-sided 95% confidence limit, -8.3 percentage points). Secondary outcomes were similar for both treatments and were not analyzed statistically: median best-corrected visual acuity of 20/20 and an overall treatment failure rate of 17 of 127 patients (13.4%), of whom 8 of 127 patients (6.3%) required therapeutic keratoplasty. No serious drug-related adverse events occurred.

CONCLUSIONS

PHMB 0.08% monotherapy may be as effective (or at worse only 8 percentage points less effective) as dual therapy with PHMB 0.02%+ propamidine (a widely used therapy) with medical cure rates of more than 86%, when used with the trial treatment delivery protocol in populations with AK with similar disease severity.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

The role of naturally acquired intracellular Pseudomonas aeruginosa in the development of Acanthamoeba keratitis in an animal model

BACKGROUND

Acanthamoeba is an environmental host for various microorganisms. Acanthamoeba is also becoming an increasingly important pathogen as a cause of keratitis. In Acanthamoeba keratitis (AK), coinfections involving pathogenic bacteria have been reported, potentially attributed to the carriage of microbes by Acanthamoeba. This study assessed the presence of intracellular bacteria in Acanthamoeba species recovered from domestic tap water and corneas of two different AK patients and examined the impact of naturally occurring intracellular bacteria within Acanthamoeba on the severity of corneal infections in rats.

METHODOLOGY/PRINCIPAL FINDINGS

Household water and corneal swabs were collected from AK patients. Acanthamoeba strains and genotypes were confirmed by sequencing. Acanthamoeba isolates were assessed for the presence of intracellular bacteria using sequencing, fluorescence in situ hybridization (FISH), and electron microscopy. The viability of the bacteria in Acanthamoeba was assessed by labelling with alkyne-functionalized D-alanine (alkDala). Primary human macrophages were used to compare the intracellular survival and replication of the endosymbiotic Pseudomonas aeruginosa and a wild type strain. Eyes of rats were challenged intrastromally with Acanthamoeba containing or devoid of P. aeruginosa and evaluated for the clinical response. Domestic water and corneal swabs were positive for Acanthamoeba. Both strains belonged to genotype T4F. One of the Acanthamoeba isolates harboured P. aeruginosa which was seen throughout the Acanthamoeba's cytoplasm. It was metabolically active and could be seen undergoing binary fission. This motile strain was able to replicate in macrophage to a greater degree than strain PAO1 (p<0.05). Inoculation of Acanthamoeba containing the intracellular P. aeruginosa in rats eyes resulted in a severe keratitis with increased neutrophil response. Acanthamoeba alone induced milder keratitis.

CONCLUSIONS/SIGNIFICANCE

Our findings indicate the presence of live intracellular bacteria in Acanthamoeba can increase the severity of acute keratitis in vivo. As P. aeruginosa is a common cause of keratitis, this may indicate the potential for these intracellular bacteria in Acanthamoeba to lead to severe polymicrobial keratitis.

New Frontiers in Acanthamoeba Keratitis Diagnosis and Management

Acanthamoeba Keratitis (AK) is a severe corneal infection caused by the Acanthamoeba species of protozoa, potentially leading to permanent vision loss. AK requires prompt diagnosis and treatment to mitigate vision impairment. Diagnosing AK is challenging due to overlapping symptoms with other corneal infections, and treatment is made complicated by the organism's dual forms and increasing virulence, and delayed diagnosis. In this review, new approaches in AK diagnostics and treatment within the last 5 years are discussed. The English-language literature on PubMed was reviewed using the search terms "Acanthamoeba keratitis" and "diagnosis" or "treatment" and focused on studies published between 2018 and 2023. Two hundred sixty-five publications were initially identified, of which eighty-seven met inclusion and exclusion criteria. This review highlights the findings of these studies. Notably, advances in PCR-based diagnostics may be clinically implemented in the near future, while antibody-based and machine-learning approaches hold promise for the future. Single-drug topical therapy (0.08% PHMB) may improve drug access and efficacy, while oral medication (i.e., miltefosine) may offer a treatment option for patients with recalcitrant disease.

Identification and quantification of Acanthamoeba spp. within seawater at four coastal lagoons on the east coast of Australia

Acanthamoeba is an opportunistic free-living heterotrophic protist that is the most predominant amoeba in diverse ecological habitats. Acanthamoeba causes amoebic keratitis (AK), a painful and potentially blinding corneal infection. Major risk factors for AK have been linked to non-optimal contact lens hygiene practices and Acanthamoeba contamination of domestic and recreational water. This study investigated the incidence and seasonal variation of Acanthamoeba spp. within coastal lagoons located on the eastern coast of Australia and then examined the association between Acanthamoeba and water abiotic factors and bacterial species within the water. Water samples were collected from four intermittently closed and open lagoons (ICOLLs) (Wamberal, Terrigal, Avoca and Cockrone) every month between August 2019 to July 2020 except March and April. qPCR was used to target the Acanthamoeba 18S rRNA gene, validated by Sanger sequencing. Water abiotic factors were measured in situ using a multiprobe metre and 16S rRNA sequencing (V3-V4) was performed to characterise bacterial community composition. Network analysis was used to gauge putative associations between Acanthamoeba incidence and bacterial amplicon sequence variants (ASVs). Among 206 water samples analysed, 79 (38.3%) were Acanthamoeba positive and Acanthamoeba level was significantly higher in summer compared with winter, spring, or autumn (p = 0.008). More than 50% (23/45) water samples of Terrigal were positive for Acanthamoeba which is a highly urbanised area with extensive recreational activities while about 32% (16/49) samples were positive from Cockrone that is the least impacted lagoon by urban development. All sequenced strains belonged to the pathogenic genotype T4 clade except two which were of genotype clades T2 and T5. Water turbidity, temperature, intl1 gene concentration, and dissolved O2 were significantly associated with Acanthamoeba incidence (p < 0.05). The ASVs level of cyanobacteria, Pseudomonas spp., Candidatus spp., and marine bacteria of the Actinobacteria phylum and Acanthamoeba 18S rRNA genes were positively correlated (Pearson's r ≥ 0.14). The presence of Acanthamoeba spp. in all lagoons, except Wamberal, was associated with significant differences in the composition of bacterial communities (beta diversity). The results of this study suggest that coastal lagoons, particularly those in urbanised regions with extensive water recreational activities, may pose an elevated risk to human health due to the relatively high incidence of pathogenic Acanthamoeba in the summer. These findings underscore the importance of educating the public about the rare yet devastating impact of AK on vision and quality of life, highlighting the need for collaborative efforts between public health officials and educators to promote awareness and preventive measures, especially focusing lagoons residents and travellers.

A simple method for culturing Acanthamoeba from soft contact lens at a clinical laboratory of a hospital: Case report of Acanthamoeba keratitis

Key Clinical Message

A simple culturing method for Acanthamoeba available at a clinical laboratory is a key for making timely diagnosis and starting treatment with topical 0.02% chlorhexidine gluconate eye drops, together with 0.1% miconazole or fluconazole eye drops.

Abstract

A 19-year-old woman with pain and injection in the right eye showed spotty corneal infiltration and radiating linear opacity. Suspicious of Acanthamoeba keratitis, corneal scraping, and the soft contact lens were sent to in-house clinical laboratory to culture successfully Acanthamoeba on Sabouraud dextrose agar plate painted with heat-treated dead bacilli.

[Bottlenecks in the availability of ophthalmological medications : Initiative of the Working Group on Ethics in Ophthalmology of the DOG and the University Eye Clinic Bonn]

BACKGROUND

Bottlenecks in drug supply in the field of ophthalmological are continuously increasing in Germany. So far, these have hardly been communicated and discussed. We see the transparent presentation of the problem as a first step in compiling concepts to counteract this development.

AIM OF THE WORK

Presentation of the supply shortages in ophthalmological drugs.

MATERIAL AND METHODS

A listing and discussion of the shortages in drug supply to the best of our knowledge are presented.

RESULTS

We distinguish between the problems in (1) supply shortages, (2) discontinuation of production, (3) lack of availability in Germany and (4) manufacture of drugs in specialized pharmacies often lacking approval for the ophthalmological indications.

DISCUSSION

The reasons for drug supply shortages in ophthalmology are complex and therefore no easy solutions can be expected; however, industrial and regulatory authorities at the national and European levels are called upon to analyze the underlying problems and to find appropriate solutions.

Topical Sustained Delivery of Miltefosine Via Drug-Eluting Contact Lenses to Treat Acanthamoeba Keratitis

This study aimed to develop a miltefosine-eluting contact lens (MLF-CL) device that would allow sustained and localized miltefosine release for the treatment of Acanthamoeba keratitis. MLF-CLs were produced in three different miltefosine doses by solvent-casting a thin miltefosine-polymer film around the periphery of a methafilcon hydrogel, which was then lathed into a contact lens. During seven days of in vitro testing, all three formulations demonstrated sustained release from the lens at theoretically therapeutic levels. Based on the physicochemical characterization of MLF-CLs, MLF-CL's physical properties are not significantly different from commercial contact lenses in terms of light transmittance, water content and wettability. MLF-CLs possessed a slight reduction in compression modulus that was attributed to the inclusion of polymer-drug films but still remain within the optimal range of soft contact lenses. In cytotoxicity studies, MLF-CL indicated up to 91% viability, which decreased proportionally as miltefosine loading increased. A three-day biocompatibility test on New Zealand White rabbits revealed no impact of MLF-CLs on the corneal tissue. The MLF-CLs provided sustained in vitro release of miltefosine for a week while maintaining comparable physical features to a commercial contact lens. MLF-CL has a promising potential to be used as a successful treatment method for Acanthamoeba keratitis.

Acanthamoeba, an environmental phagocyte enhancing survival and transmission of human pathogens

The opportunistic protist Acanthamoeba, which interacts with other microbes such as bacteria, fungi, and viruses, shows significant similarity in cellular and functional aspects to human macrophages. Intracellular survival of microbes in this microbivorous amoebal host may be a crucial step for initiation of infection in higher eukaryotic cells. Therefore, Acanthamoeba-microbe adaptations are considered an evolutionary model of macrophage-pathogen interactions. This paper reviews Acanthamoeba as an emerging human pathogen and different ecological interactions between Acanthamoeba and microbes that may serve as environmental training grounds and a genetic melting pot for the evolution, persistence, and transmission of potential human pathogens.

Assessment of genotypes, endosymbionts and clinical characteristics of Acanthamoeba recovered from ocular infection

Introduction

Acanthamoeba is an emerging pathogen, infamous for its resilience against antiprotozoal compounds, disinfectants and harsh environments. It is known to cause keratitis, a sight-threatening, painful and difficult to treat corneal infection which is often reported among contact lens wearers and patients with ocular trauma. Acanthamoeba comprises over 24 species and currently 23 genotypes (T1-T23) have been identified.

Aims

This retrospective study was designed to examine the Acanthamoeba species and genotypes recovered from patients with Acanthamoeba keratitis (AK), determine the presence of endosymbionts in ocular isolates of Acanthamoeba and review the clinical presentations.

Methodology

Thirteen culture-confirmed AK patients treated in a tertiary eye care facility in Hyderabad, India from February to October 2020 were included in this study. The clinical manifestations, medications and visual outcomes of all patients were obtained from medical records. The Acanthamoeba isolates were identified by sequencing the ribosomal nuclear subunit (rns) gene. Acanthamoeba isolates were assessed for the presence of bacterial or fungal endosymbionts using molecular assays, PCR and fluorescence in situ hybridization (FISH).

Results

The mean age of the patients was 33 years (SD ± 17.4; 95% CI 22.5 to 43.5 years). Six (46.2%) cases had AK associated risk factors; four patients had ocular trauma and two were contact lens wearers. A. culbertsoni (6/13, 46.2%) was the most common species, followed by A. polyphaga and A. triangularis. Most of the isolates (12/13) belonged to genotype T4 and one was a T12; three sub-clusters T4A, T4B, and T4F were identified within the T4 genotype. There was no significant association between Acanthamoeba types and clinical outcomes. Eight (61.5%) isolates harboured intracellular bacteria and one contained Malassezia restricta. The presence of intracellular microbes was associated with a higher proportion of stromal infiltrates (88.9%, 8/9), epithelial defect (55.6%, 5/9) and hypopyon (55.6%, 5/9) compared to 50% (2/4), 25% (1/4) and 25% (1/4) AK cases without intracellular microbes, respectively.

Conclusions

Genotype T4 was the predominant isolate in southern India. This is the second report of T12 genotype identified from AK patient in India, which is rarely reported worldwide. The majority of the Acanthamoeba clinical isolates in this study harboured intracellular microbes, which may impact clinical characteristics of AK.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07741-4.