The rising tide of Acanthamoeba keratitis in Auckland, New Zealand: a 7-year review of presentation, diagnosis and outcomes (2009-2016)

Bifunctional chemokine-nanobody fusion protein enhances neutrophil recruitment to impede Acanthamoeba immune evasion

BACKGROUND

Acanthamoeba keratitis (AK) is a severe infectious disease that causes serious visual impairment and low quality of life. This study aims to investigate the immune landscape in AK, with the goal of improving treatment outcomes through immunotherapy.

METHODS

We conducted single-cell transcriptome sequencing on corneal tissues from nine patients (3 AK patients, 3 patients with fungal keratitis and 3 patients with bacterial keratitis). Bioinformatic analysis calculated the cell subsets and their proportions within different infectious keratitis. CellChat analysis elucidated the differential expression of chemokines in keratitis. After that, screening amebic nano-antibodies, synthesizing antibody-chemokine fusion proteins, and validated their affinity and chemotactic abilities in vitro and in vivo. And assessing of the therapeutic efficacy of antibody-chemokine fusion proteins.

FINDINGS

The UMAP plot demonstrated the 13 major cell clusters in infectious keratitis. Compared with non-AK group, the neutrophil proportion of AK group is markedly reduced. Cell communication indicated a diminished CXCL pathway in AK. Acanthamoeba-specific antibodies were obtained by screening a natural antibody library derived from alpacas. The amoeba-specific antibodies were conjugated with the CXCL1 chemokine, and this fusion protein exhibited robust binding affinity to Acanthamoeba and chemotactic capacity both in vitro and in vivo. Furthermore, in vivo animal investigations indicated that the fusion protein presented excellent therapeutic effect and could effectively eliminate the Acanthamoeba burden.

INTERPRETATION

This study revealed an immune evasion mechanism employed by Acanthamoeba and offered a therapeutic approach. It presents promising potential for enhancing the treatment of infectious diseases by targeting and overcoming challenges posed by immune evasion.

FUNDING

This work was funded by National Natural Science Foundation of China (grant number 82171017 and 82471041) and the Beijing Municipal Public Welfare Development and Reform Pilot Project for Medical Research Institutes (PWD&RPP-MRI, JYY2023-6).

Acanthamoeba Keratitis Management and Prognostic Factors: A Systematic Review

Background/Objectives: The aim of this study was to review the therapeutic and prognostic factors influencing Acanthamoeba Keratitis (AK) management. Methods: A systematic search was performed across MEDLINE® (via PubMed), Web of Science®, and Scopus®, following the PRISMA 2020 guidelines, and registered in PROSPERO (CRD420251010774). Studies reporting AK treatment regiments and prognostic factors were included. After extracting the data from the included articles, the relevant aspects of the treatment and the prognostic factors were compared and summarized. Results: Sixty-one articles were included: nine were prospective, including 3 randomized controlled trials (RCTs), and fifty-two were retrospective. The findings suggest that therapeutic epithelial debridement (TED), followed by an association with biguanides, diamidines, and an antibacterial agent, is a strong initial treatment option. An adjunctive medical treatment with topical voriconazole 1% or oral miltefosine may also be considered. Surgical approaches were also assessed when the pharmaceutical therapy failed, with Deep Anterior Lamellar Keratoplasty (DALK) playing an important role in the cases without a deep stroma involvement. Early Therapeutic Penetrating Keratoplasty (TPK) should be used as a salvage therapy and Optical Penetrating Keratoplasty (OPK) should be used for rehabilitation purposes. Key prognostic factors include older age, delayed diagnosis, corticosteroid use before prompt diagnosis, poor initial best corrected visual acuity (BCVA), and AK stage at presentation. Conclusions: The initial treatment with TED, biguanides, and diamidines remains the foundation of treatment. Surgical options can be considered in advanced cases. An early diagnosis, age, and initial BCVA are prognosis factors that should be considered. Future research may focus on improvement of protocols and searching for novel agents.

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.

The incidence of severe complications in acanthamoeba keratitis: Qualitative and quantitative systematic assessment

Acanthamoeba keratitis (AK) is a rare, sight-threating corneal infection. The disease is challenging to diagnose and treat, and the amoeba can rapidly encyst, persisting in the tissue and causing recurrences. Medical therapy is conventionally considered the first line treatment, but advanced cases could require more invasive treatments like a "chaud" corneal transplant. We review the incidence of severe complications in patients affected by AK. Of 439 reports screened, 158 met our inclusion criteria. Incidence of severe complications was low, with 2.21 % patients developing perforation, 1 % requiring evisceration/enucleation and less than 1 % developing endophthalmitis. Corneal transplantation was required in 16.68 % of the cases. According to our results, and considering the reported incidences of these complications in other infectious keratitis, AK patients have an overall low risk of developing perforation, endophthalmitis, and enucleation/evisceration. Nevertheless, data available in the literature remain poor, and further randomized control trials are needed to confirm our findings.

Novel anti-Acanthamoeba effects elicited by a repurposed poly (ADP-ribose) polymerase inhibitor AZ9482

Introduction

Acanthamoeba infection is a serious public health concern, necessitating the development of effective and safe anti-Acanthamoeba chemotherapies. Poly (ADP-ribose) polymerases (PARPs) govern a colossal amount of biological processes, such as DNA damage repair, protein degradation and apoptosis. Multiple PARP-targeted compounds have been approved for cancer treatment. However, repurposing of PARP inhibitors to treat Acanthamoeba is poorly understood.

Methods

In the present study, we attempted to fill these knowledge gaps by performing anti-Acanthamoeba efficacy assays, cell biology experiments, bioinformatics, and transcriptomic analyses.

Results

Using a homology model of Acanthamoeba poly (ADP-ribose) polymerases (PARPs), molecular docking of approved drugs revealed three potential inhibitory compounds: olaparib, venadaparib and AZ9482. In particular, venadaparib exhibited superior docking scores (-13.71) and favorable predicted binding free energy (-89.28 kcal/mol), followed by AZ9482, which showed a docking score of -13.20 and a binding free energy of -92.13 kcal/mol. Notably, the positively charged cyclopropylamine in venadaparib established a salt bridge (through E535) and a hydrogen bond (via N531) within the binding pocket. For comparison, AZ9482 was well stacked by the surrounding aromatic residues including H625, Y652, Y659 and Y670. In an assessment of trophozoites viability, AZ9482 exhibited a dose-and time-dependent anti-trophozoite effect by suppressing Acanthamoeba PARP activity, unlike olaparib and venadaparib. An Annexin V-fluorescein isothiocyanate/propidium iodide apoptosis assay revealed AZ9482 induced trophozoite necrotic cell death rather than apoptosis. Transcriptomics analyses conducted on Acanthamoeba trophozoites treated with AZ9482 demonstrated an atlas of differentially regulated proteins and genes, and found that AZ9482 rapidly upregulates a multitude of DNA damage repair pathways in trophozoites, and intriguingly downregulates several virulent genes. Analyzing gene expression related to DNA damage repair pathway and the rate of apurinic/apyrimidinic (AP) sites indicated DNA damage efficacy and repair modulation in Acanthamoeba trophozoites following AZ9482 treatment.

Discussion

Collectively, these findings highlight AZ9482, as a structurally unique PARP inhibitor, provides a promising prototype for advancing anti-Acanthamoeba drug research.

Understanding Acanthamoeba Keratitis: An In-Depth Review of a Sight-Threatening Eye Infection

Acanthamoeba keratitis (AK) is a rare but potentially sight-threatening corneal infection caused by the Acanthamoeba parasite. This microorganism is found ubiquitously in the environment, often in freshwater, soil, and other sources of moisture. Despite its low incidence, AK presents significant challenges due to delayed diagnosis and the complex nature of therapeutic management. Early recognition is crucial to prevent severe ocular complications, including corneal ulceration and vision loss. Diagnostic modalities and treatment strategies may vary greatly depending on the clinical manifestation and the available tools. With the growing reported cases of Acanthamoeba keratitis, it is essential for the ophthalmic community to thoroughly understand this condition for its effective management and improved outcomes. This review provides a comprehensive overview of AK, encompassing its epidemiology, risk factors, pathophysiology, clinical manifestations, diagnosis, and treatment.

Acanthamoeba keratitis - A review

This is a comprehensive review after a thorough literature search in PubMed-indexed journals, incorporating current information on the pathophysiology, clinical features, diagnosis, medical and surgical therapy, as well as outcomes of Acanthamoeba keratitis (AK). AK is a significant cause of ocular morbidity, and early diagnosis with timely institution of appropriate therapy is the key to obtaining good outcomes. The varied presentations result in frequent misdiagnosis, and co-infections can increase the morbidity of the disease. The first line of therapy continues to be biguanides and diamidines, with surgery as a last resort.

Differentiation of acanthamoeba keratitis from other non-acanthamoeba keratitis: Risk factors and clinical features

INTRODUCTION

Infectious Keratitis is one of the most common ocular emergencies seen by ophthalmologists. Our aim is to identify the risk factors and clinical features of Acanthamoeba Keratitis (AK).

METHODS

This retrospective chart review study was conducted at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia, and included all the microbial keratitis cases, male and female patients of all ages. The main outcome is the differentiation between various microbial keratitis types.

RESULTS

We included 134 consecutive eyes of 126 persons. We had 24 cases of acanthamoeba keratitis, 22 bacterial keratitis, 24 fungal keratitis, 32 herpetic keratitis, and 32 bacterial co-infection. Contact lens wear was found in 33 eyes (24.6%). Among acanthamoeba keratitis patients, 73% were ≤ 39 years of age, and 73% were females (P <0.001). Also, in AK cases, epithelial defect was found in all cases (100%), endothelial plaques were found in 18 eyes (69.2%), 12 cases had radial keratoneuritis (46.2%), and ring infiltrate was found in 53.8% of AK cases.

CONCLUSIONS

We determined the factors that increase the risk of acanthamoeba infection and the clinical characteristics that help distinguish it from other types of microbial keratitis. Our findings suggest that younger females and patients who wear contact lenses are more likely to develop acanthamoeba keratitis. The occurrence of epitheliopathy, ring infiltrate, radial keratoneuritis, and endothelial plaques indicate the possibility of acanthamoeba infection. Promoting education on wearing contact lenses is essential to reduce the risk of acanthamoeba infection, as it is the most significant risk factor for this infection.

Diagnosing and monitoring the characteristics of Acanthamoeba keratitis using slit scanning and laser scanning in vivo confocal microscopy

INTRODUCTION

Acanthamoeba keratitis (AK) is a serious and potentially blinding ocular infection caused by the free-living amoeba, Acanthamoeba. In vivo confocal microscopy (IVCM) is a non-invasive device which has been proven of great use to diagnose Acanthamoeba infections immediately. The aim of this review was to establish different patterns and signs of AK that appear on the IVCM both before and after treatment.

METHODS

A systematic review of the literature from 1974 until September 2021 was performed using Embase and PubMed, following The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Twenty different signs of AK were observed using IVCM. The included studies used vastly different criteria to diagnose infections, ranging from just 1 to 13 of the signs, demonstrating the current lack of a standardised diagnosis of this infection using the IVCM. The appearance of double wall cysts, trophozoites, signet rings, target signs and clusters were shown to be pathognomonic to AK infections. Bright spots located in the corneal epithelium were demonstrated as non-reliable predictors of AK. The presence of cysts in clusters and single file can predict the need for corneal transplantation. The morphological changes in cysts using the IVCM following treatment were described as breaking down to hollow forms and occasionally surrounded by black cavities. Using this information, a visual guideline for identifying AK signs in diagnosis and follow-up using IVCM was created.

CONCLUSION

Increased awareness of the different signs and patterns of AK that appear on the IVCM is crucial in order to correctly identify an infection and increase the potential of this device. Our guidelines presented here can be used, but further studies are needed in order to determine the relationship and aetiology of these signs and cellular changes on the IVCM both before and after anti-amoeba treatment.

Diagnosis of Acanthamoeba Keratitis: Past, Present and Future

Acanthamoeba keratitis (AK) is a painful and sight-threatening parasitic corneal infection. In recent years, the incidence of AK has increased. Timely and accurate diagnosis is crucial during the management of AK, as delayed diagnosis often results in poor clinical outcomes. Currently, AK diagnosis is primarily achieved through a combination of clinical suspicion, microbiological investigations and corneal imaging. Historically, corneal scraping for microbiological culture has been considered to be the gold standard. Despite its technical ease, accessibility and cost-effectiveness, the long diagnostic turnaround time and variably low sensitivity of microbiological culture limit its use as a sole diagnostic test for AK in clinical practice. In this review, we aim to provide a comprehensive overview of the diagnostic modalities that are currently used to diagnose AK, including microscopy with staining, culture, corneal biopsy, in vivo confocal microscopy, polymerase chain reaction and anterior segment optical coherence tomography. We also highlight emerging techniques, such as next-generation sequencing and artificial intelligence-assisted models, which have the potential to transform the diagnostic landscape of AK.

Diagnostic accuracy of confocal scan in detecting acanthamoeba keratitis and fungal keratitis: a systematic review and meta-analysis

PURPOSE

Acanthamoeba keratitis (AK) and fungal keratitis (FK) are two microbial keratitis that cause serious damage and, without early accurate diagnosis and treatment, may lead to blindness. In vivo corneal confocal scan, as an emerging ocular diagnostic method in comparison with microbiological smears and cultures as the gold standard, may assist in accelerating appropriate diagnosis.

OBJECTIVE

To determine the diagnostic accuracy of confocal scan for the diagnosis of AK and FK.

METHODS

Data were collected via a comprehensive literature search of PubMed, Web of Science, Cochrane Library, Embase and Scopus using keywords related to diagnostic accuracy of confocal scan in AK and FK up to October 2022. Pooled data underwent meta-analysis in terms of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall diagnostic odds ratio (DOR) of confocal scan for the diagnosis of AK and FK.

RESULTS

The final 14 relevant studies were identified, including 1950 eyes. Meta-analysis in AK group revealed 94% sensitivity, 87% specificity, 89% PPV, 92% NPV, and DOR of 143.32, and in FK group disclosed 88% sensitivity, 85% specificity, 85% PPV, 88% NPV, and DOR of 75.98.

CONCLUSION

The accuracy of confocal scan for the diagnosis of AK was significantly more than that for detecting FK; despite the limitations such as limited numbers of available retrospective studies for the detection of FK, confocal scan had an acceptable performance in detecting FK eyes. The overall performance of NCS was similar with that of HRT-RCM for the detection of both types of keratitis.

Susceptibility of the Intact and Traumatized Feline Cornea to In Vitro Binding and Invasion by Acanthamoeba castellanii

PURPOSE

Acanthamoeba castellanii ( A. castellanii ) displays host specificity at the level of the ocular surface. This study determined the susceptibility of the intact and traumatized feline cornea to A. castellanii binding and invasion relative to other host species with established susceptibility and resistance to Acanthamoeba binding.

METHODS

Full-thickness buttons of fresh feline, porcine, and canine corneas were prepared. The corneal epithelium was confirmed intact by fluorescein staining or lightly scarified with a 25-G needle to simulate corneal trauma. Acanthamoeba castellanii was axenically cultivated. Corneal buttons were incubated with the parasite suspension or parasite-free medium for 18 hours at 35°C. Corneal buttons were rinsed, fixed, and processed for histopathology and immunohistochemistry using immunoperoxidase and immunofluorescence methods of amoeba detection.

RESULTS

Numerous amoebae were bound to feline and porcine corneas incubated with parasites. In both intact and traumatized corneas, amoebae were detected at all levels in the corneal epithelium and within the anterior stroma. In traumatized corneal sections, amoebae were frequently present in regions of epithelial damage. Corneal architecture was well-preserved in sections incubated with parasite-free medium; however, epithelial cell sloughing, separation of epithelial layers, and epithelial detachment from the stroma were observed in corneas incubated with amoebae. Intact and traumatized canine corneas were relatively free of adherent amoebae, and corneal architecture was indistinguishable between sections incubated with the parasite suspension and parasite-free medium.

CONCLUSIONS

The feline cornea is highly susceptible to in vitro binding and invasion by A. castellanii . Acanthamoeba binding to the feline cornea does not require a previous epithelial defect.

The epidemiology of infectious keratitis

Infectious keratitis is a rare but potentially severe sight-threatening disease, associated with considerable societal burden, cost and morbidity. This review summarises the most recent evidence for the incidence, risk factors and impact of disease, all of which vary widely according to region, access to health care, socioeconomic and environmental factors, predisposing conditions and causative organisms. The frequency and societal impact of infectious keratitis are significantly higher in low-income countries. In non-viral infectious keratitis, bacterial causes predominate in most regions. Fungi, particularly linked with agricultural trauma, are more frequently associated with infectious keratitis in low-income regions, particularly in India and certain African countries. The disease impact is compounded by poverty and limited access to services and treatment. Early diagnosis, access to appropriate treatment, prophylaxis in ocular trauma, availability of eye protection, awareness of risk factors may be associated with reduced disease severity and vision loss. Evidence for the incidence and burden of disease is lacking in certain regions and well-designed epidemiological studies to identify independent risk factors for the disease and those associated with more severe outcomes may better identify causation and guide resource allocation and preventative strategies.

The global epidemiology and clinical diagnosis of Acanthamoeba keratitis

Acanthamoeba keratitis is a rare parasitic infection of the cornea that can lead to permanent blindness if not diagnosed and treated promptly. We collected data on the incidences of Acanthamoeba keratitis from 20 countries and calculated an annual incidence of 23,561 cases, with the lowest rates in Tunisia and Belgium, and the highest in India. We analyzed 3755 Acanthamoeba sequences from the GenBank database across Asia, Europe, North America, South America, and Oceania and genotyped them into T1, T2, T3, T4, T5, T10, T11, T12, and T15. Many genotypes possess different characteristics, yet T4 is the most prevalent genotype. As efficient treatment against Acanthamoeba remains lacking, prevention from early diagnosis via staining, PCR, or in vivo confocal microscopy (IVCM) becomes significant for the condition's prognosis. IVCM is the most recommended approach for the early detection of Acanthamoeba. If IVCM is unavailable, PCR should be used as an alternative.

Anti-Acanthamoeba activity of a semi-synthetic mangostin derivative and its ability in removal of Acanthamoeba triangularis WU19001 on contact lens

Garcinia mangostana L., also known as the mangosteen tree, is a native medicinal plant in Southeast Asia having a wide variety of pharmacologically active compounds, including xanthonoid mangostin. In this study, we examined the pharmacological activities of the selected semi-synthetic mangostin derivative, namely, amoebicidal activity, encystation inhibition, excystation activity, and removal capacity of adhesive Acanthamoeba from the surface of contact lens (CL). Among the three derivatives, C1 exhibited promising anti-Acanthamoeba activity against Acanthamoeba triangularis WU19001 trophozoites and cysts. SEM images displayed morphological changes in Acanthamoeba trophozoites, including the loss of acanthopodia, pore formation in the cell membrane, and membrane damage. In addition, the treated cyst was shrunken and adopted an irregular flat cyst shape. Under a fluorescence microscope, acridine orange and propidium iodide (AO/PI) staining revealed C1 induced condensation of cytoplasm and chromatin with the loss of cell volume in the treated trophozoites, while calcofluor white staining demonstrated the leakage of cell wall in treated cysts, leading to cell death. Interestingly, at the concentration ranges in which C1 showed the anti-Acanthamoeba effects (IC₅₀ values ranging from 0.035-0.056 mg/mL), they were not toxic to Vero cells. C1 displayed the highest inhibitory effect on A. triangularis encystation at 1/16×MIC value (0.004 mg/mL). While C1 demonstrated the excystation activity at 1/128×MIC value with a high rate of 89.47%. Furthermore, C1 exhibited the removal capacity of adhesive Acanthamoeba from the surface of CL comparable with commercial multipurpose solutions (MPSs). Based on the results obtained, C1 may be a promising lead agent to develop a therapeutic for the treatment of Acanthamoeba infections and disinfectant solutions for CL.

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.

Super aggregated amphotericin B with a thermoreversible in situ gelling ophthalmic system for amoebic keratitis treatment

Acanthamoeba spp. are the causative agents of a sight-threatening infection of the cornea known as Acanthamoeba keratitis (AK). Amphotericin B - deoxycholate (AB) is used in the treatment of infectious keratitis, however, its topical administration has side effects as blepharitis, iritis, and painful instillation. In this context, the preheating of AB can decrease its toxicity by the formation of super aggregates (hAB). hAB associated with a thermoreversible in situ gelling ophthalmic system is a promising option due to the latter biocompatibility, low toxicity, and high residence time on the ocular surface. Our objective was to develop a topical ocular formulation of hAB for the treatment of AK. After heating at 70°C for 20 min, hAB was incorporated into a thermoreversible gelling system. The amebicidal activity of AB and hAB was evaluated against trophozoites and cysts of A. castellanii (ATCC 50492) and a regional clinical isolate (IC01). The results showed that the preheating of AB did not change the pharmacological action of the drug, with the amebicidal effect of AB and hAB under trophozoites and cysts of Acanthamoeba spp. The thermoreversible system remained stable, allowing the increase of drug retention time. For assessment of cytotoxicity, HUVEC (ATCC® CRL-1730) cells were challenged with AB and hAB for 48h. Cell viability was assessed, and hAB did not show cytotoxicity for HUVEC cells. As far as we know this was the first study that showed the preheated AB associated with a thermoreversible in situ gelling ophthalmic system as a promising system for topical ocular topical administration of hAB for AK therapy.

Applications of medicinal chemistry for drug discovery against Acanthamoeba infections

Acanthamoeba is a genus of free-living amoebae, pervasively found in the environment. Most of its pathogenic species are the causative agent of sight-threatening Acanthamoeba keratitis and fatal granulomatous amoebic encephalitis. Despite the advancements in the field of chemotherapy, treating Acanthamoeba infections is still challenging due to incomplete knowledge of the complicated pathophysiology. In case of infection, the treatment regimen for the patients is often ineffective due to delayed diagnosis, poor specificity, and side-effects. Besides the resistance of Acanthamoeba cysts to most of the drugs, the recurrence of infection further complicates the recovery. Thus, it is necessary to develop an effective treatment which can eradicate these rare, but serious infections. Based on various computational and in vitro studies, it has been established that the synthetic scaffolds such as heterocyclic compounds may act as potential drug leads for the development of antiamoebic drugs. In this review, we report different classes of synthetic compounds especially heterocyclic compounds which have shown promising results against Acanthamoeba. Moreover, the antiamoebic activities of synthetic compounds with their possible mode of actions against Acanthamoeba, have been summarized and discussed in this review.

CLEAR - Evidence-based contact lens practice

Evidence-based contact lens -->practice involves finding, appraising and applying research findings as the basis for patient management decisions. These decisions should be informed by the strength of the research study designs that address the question, as well as by the experience of the practitioner and the preferences and environment of the patient. This reports reviews and summarises the published research evidence that is available to inform soft and rigid contact lens history and symptoms taking, anterior eye health examination (including the optimised use of ophthalmic dyes, grading scales, imaging techniques and lid eversion), considerations for contact lens selection (including the ocular surface measurements required to select the most appropriate lens parameter, lens modality and material selection), evaluation of lens fit, prescribing (teaching self-application and removal, adaptation, care regimen and cleaning instructions, as well as -->minimising risks of lens wear through encouraging compliance) and an aftercare routine.

Challenges in Acanthamoeba Keratitis: A Review

To review challenges in the diagnosis and management of Acanthamoeba keratitis (AK), along with prognostic factors, in order to help ophthalmologists avoid misdiagnosis, protracted treatment periods, and long-term negative sequelae, with an overarching goal of improving patient outcomes and quality of life, we examined AK studies published between January 1998 and December 2019. All manuscripts describing clinical manifestations, diagnosis, treatment, prognosis, and challenges in short- and long-term management were included. The diagnosis of AK is often challenging. An increased time between symptom onset and the initiation of appropriate therapy is associated with poorer visual outcomes. The timely initiation of standardized antiamoebic therapies improves visual outcomes, decreases the duration of treatment, and reduces the chances of needing surgical intervention. In clinical practice, AK diagnosis is often missed or delayed, leading to poorer final visual outcomes and a negative impact on patient morbidity and quality of life.

Gas-Permeable Contact Lenses and Water Exposure: Practices and Perceptions

SIGNIFICANCE

This study provides insight into the current recommendations, clinical behaviors, and risk assessments of eye care professionals on the topic of rigid contact lens exposure to tap water. This knowledge may motivate professional organizations to develop initiatives to educate eye care professionals on the dangers of contact lens exposure to water.

PURPOSE

The purpose of this study was to investigate the practice patterns and risk perceptions of eye care professionals regarding gas-permeable contact lens exposure to tap water.

METHODS

A branched-logic survey was started by 320 clinicians, vision scientists, and industry personnel and was fully completed by 272 participants. The survey queried participants about their current practices, recommendations, and perceptions of risk regarding exposure of gas-permeable contact lenses to tap water.

RESULTS

Of those who prescribe gas-permeable contact lenses, 57.4% reported rinsing lenses with tap water, whereas only 32.7% reported engaging in this same behavior in front of patients. Of those who reported never rinsing lenses with tap water, 85.6% indicated that rinsing lenses with water increases infection risk, whereas 52.1% of those who rinse lenses with water reported the same perceived risk (P < .001). Of all participants, 60% indicated that wearing contact lenses while showering increases infection risk, and 50.2% of all participants advised patients to avoid this behavior.

CONCLUSIONS

A discrepancy exists between perceptions of risk concerning exposure of contact lenses to water and both clinical practices and patient education provided by professionals.

Microbiological diagnosis of Acanthamoebic keratitis: experience from tertiary care center of North India

Acanthamoeba keratitis (AK) is a painful vision-threatening infection caused by pathogenic free-living Acanthamoeba. Due to the non-specific clinical presentation, this condition tends to be misdiagnosed by clinicians. A timely diagnosis is crucial for favorable visual outcome. Three hundred patients with suspected microbial keratitis presenting to the Advanced Eye Center at our tertiary care center in North India during the period from 2014 to 2018 were included. Patient's corneal scrapings, contact lens, lens solution, lens case, and tears were processed for microscopic examination by Giemsa and Calcofluor staining, non-nutrient agar (NNA) culture and molecular diagnosis by conventional PCR (cPCR) and Real-time PCR (qPCR). 18S rDNA gene sequencing was done to assess phylogenetic relationship. AK was found in 3.6% (11/300) of non-bacterial non-fungal keratitis patients. Among microbiological techniques, microscopy for Acanthamoeba was positive in 7 cases, NNA culture was positive in 9 cases and 11 cases were detected both by cPCR and qPCR. The sensitivity of microscopy, culture, cPCR and qPCR was 63.64%, 81.82 %, 100%, and 100% respectively whereas specificity was 100% for all the tests. 18S rDNA sequencing revealed that A. castellanii was the predominant species and isolates were genetically distinct. AK should be considered in the differential diagnosis of infectious keratitis. Molecular tests are useful for rapid, sensitive and specific diagnosis and must be included in workup of keratitis.

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.

The biology of Acanthamoeba keratitis

Acanthamoeba keratitis (AK) is a rare protozoal infection of the cornea. At least eight species of Acanthamoeba are known to cause this sight-threatening disease of the ocular surface. Acanthamoeba spp. exist in a wide array of niches ranging from thermal springs to under ice and every conceivable habitat in between. Contact lens wear is the leading risk factor for AK and is practiced by over 30 million individuals in the United States, yet the incidence of AK is less than 33 cases per one million contact lens wearers. Serological studies have reported that 90%-100% of individuals with no history of AK possess antibodies specific for Acanthamoeba antigens indicating that exposure to this organism is commonplace, yet disease is remarkably rare. Animal studies have shed light on the pathobiology and immunobiology of AK and indicate that a constellation of factors including the ocular surface microbiome and the microbiome of Acanthamoeba itself contribute to the pathogenesis of AK. Interesting, secretory antibodies produced by the adaptive immune response can prevent the initiation of corneal infection, but once Acanthamoeba trophozoites breach the corneal epithelium the adaptive immune system is helpless in altering the course of AK. It has been almost 50 years since AK was first described, yet many questions remain unanswered about this curious and enigmatic disease of the ocular surface.

Application of Histone Deacetylase Inhibitors MPK472 and KSK64 as a Potential Treatment Option for Acanthamoeba Keratitis

Treatment of Acanthamoeba keratitis (AK) is difficult because Acanthamoeba cysts are resistant to drugs, and as such, successful treatment requires an effective approach that inhibits cyst formation. Histone deacetylase inhibitors (HDACis) are involved in cell proliferation, differentiation, and apoptotic cell death. In this study, the effects of HDACis such as MPK472 and KSK64 on Acanthamoeba castellanii trophozoites and cysts were observed. MPK472 and KSK64 showed at least 60% amoebicidal activity against Acanthamoeba trophozoites at a concentration of 10 μM upon 8 h of treatment. Neither of the two HDACis affected mature cysts, but significant amoebicidal activities (36.4 and 33.9%) were observed against encysting Acanthamoeba following treatment with 5 and 10 μM HDACis for 24 h. Light microscopy and transmission electron microscopy results confirmed that the encystation of Acanthamoeba was inhibited by the two HDACis. In addition to this, low cytopathic effects on human corneal epithelial (HCE) cells were observed following treatment with MPK472 and KSK64 for 24 h. Our results indicate that the HDACis MPK472 and KSK64 could be used as new candidates for the development of an optimal therapeutic option for AK.

Topical corticosteroids in Acanthamoeba keratitis: Friend or foe?

BACKGROUND/AIMS

To analyse the effect of topical corticosteroids before start of anti-amoebic therapy (AAT) in Acanthamoeba keratitis (AK) on final visual outcome and to identify factors that affect the outcome.

METHODS

A retrospective case control study of the medical records of patients diagnosed with AK at the Rotterdam Eye Hospital between 2003 and 2017 was performed. Patient demographic and clinical data were collected. The outcomes of patients treated with topical corticosteroids before the start of AAT were compared with those not treated with topical corticosteroids. Univariable and multivariable analyses were conducted.

RESULTS

A total of 109 patients was diagnosed with AK, with a mean follow-up time of 18 months. The use of corticosteroids was associated with a delay in diagnosis and thereby the start of AAT. In the non-steroids group, mean diagnostic delay was 23 days versus 62 days in the steroids group (p < 0.001). We found a statistically significant effect of pre-AAT steroid use on disease severity stage (p < 0.001). Also, a suboptimal visual outcome (⩽20/80) was seen significantly more frequent in the steroids group, as was the need for an urgent penetrating keratoplasty (PK) and for the total need of surgeries.

CONCLUSION

Use of corticosteroids before the start of AAT is associated with a suboptimal visual outcome, a significantly higher risk for a PK and a significantly more severe disease stage. It is important to continuously consider a differential diagnosis in a keratitis of unknown cause and to use corticosteroids cautiously before a definite diagnosis.

Increasing incidence of Acanthamoeba keratitis in a large tertiary ophthalmology department from year 1994 to 2018

PURPOSE

Acanthamoeba (AA) keratitis is a rare and severe infection with poor prognosis. The aim was to investigate the incidence and risk factors of AA keratitis in a large tertiary ophthalmology department in Denmark.

METHODS

A search was performed in our electronic patient records by the keywords: 'PHMB/polyhexanid', 'Brolene' or 'amoeba and chlorhexidine' from year 1994 to 2018, and afterwards medical records were reviewed. A total of 65 cases of AA keratitis were hereby identified.

RESULTS

Patients were relatively young, median (range) age of 38 (15-70) years. A significant increase of diagnosing AA keratitis occurred from 0.13 cases per million per year in the first 5 years to 2.7 cases per million per year the last 5 years. Eighty-nine per cent of patients were contact lens users, and 49% had received corticosteroids before the diagnosis was established. Severe pain was present in 34% of patients. Prognosis was poor with final visual acuity of logMAR (mean, 95% CI) 0.30 (0.18-0.41), 18% had transplantation à chaud, and 2% were enucleated.

CONCLUSION

The study indicates that the incidence of AA keratitis is increasing, also in Denmark. Most patients were young contact lens users. The course of the disease is long and often painful, and the prognosis is poor despite relevant treatment.

In vivo confocal microscopy of the inflamed anterior segment: A review of clinical and research applications

In vivo confocal microscopy (IVCM) allows non-invasive imaging of the living human cornea, specifically enabling the detection of immune cells in the healthy and diseased ocular anterior segment. Studies using IVCM have provided insight into the effects of contact lens wear on corneal Langerhans cell density and morphology, and the effects of eye drops on conjunctiva-associated lymphoid tissue. IVCM has also been shown to be a useful adjunctive diagnostic tool in distinguishing infective and non-infective uveitis and in diagnosing atypical infective keratitis. In the research setting, this technology has enhanced our understanding of the role of inflammatory cells in corneal neuropathy and angiogenesis. In vivo-ex vivo correlation using animal models has helped overcome some of the difficulties in identifying cell type on IVCM images. As highlighted in this review, currently there are multiple established, and emerging, clinical and research applications for IVCM in the inflamed anterior segment.

The Spectrum of Microbial Keratitis: An Updated Review

Background:

In microbial keratitis, infection of the cornea can threaten vision through permanent corneal scarring and even perforation resulting in the loss of the eye. A literature review was conducted by Karsten, Watson and Foster (2012) to determine the spectrum of microbial keratitis. Since this publication, there have been over 2600 articles published investigating the causative pathogens of microbial keratitis.

Objective:

To determine the current spectrum of possible pathogens implicated in microbial keratitis relative to the 2012 study.

Methods:

An exhaustive literature review was conducted of all the peer-reviewed articles reporting on microbial pathogens implicated in keratitis. Databases including MEDLINE, EMBASE, Scopus and Web of Science were searched utilising their entire year limits (1950-2019).

Results:

Six-hundred and eighty-eight species representing 271 genera from 145 families were implicated in microbial keratitis. Fungal pathogens, though less frequent than bacteria, demonstrated the greatest diversity with 393 species from 169 genera that were found to cause microbial keratitis. There were 254 species of bacteria from 82 genera, 27 species of amoeba from 11 genera, and 14 species of virus from 9 genera, which were also identified as pathogens of microbial keratitis.

Conclusion:

The spectrum of pathogens implicated in microbial keratitis is extremely diverse. Bacteria were most commonly encountered and in comparison, to the review published in 2012, further 456 pathogens have been identified as causative pathogens of microbial keratitis. Therefore, the current review provides an important update on the potential spectrum of microbes, to assist clinicians in the diagnosis and treatment of microbial keratitis.

Acanthamoeba keratitis related to contact lens use in a tertiary hospital in China

Background

To report the clinical and microbiological features of Acanthamoeba keratitis (AK) related to contact lens use in a tertiary hospital in China.

Methods

In this retrospective study, the medical results of 61 cases of AK related to contact lens use from January 2000 to December 2017 were reviewed. The data included patients’ demographics, lens type, history, risk factors, disease stages, corneal scraping and culture reports, and treatments. Moreover, genotypic identification of some of the isolates was carried out with a PCR assay and sequence analysis of the 18S ribosomal DNA gene.

Results

There were 64 eyes included in the study. A total of 32.8% of the patients wore soft contact lenses, and 67.2% of patients used overnight orthokeratology. In the cases (20 eyes) in the early stage, 65% (13 eyes) had positive results according to Giemsa-stained smears, and 0.9% sodium chloride (NaCl) wet mounts revealed trophozoites in 7 eyes (35%). Six eyes (30%) were diagnosed by confocal microscopy combined with clinical signs. In the orthokeratology patients, 87.8% (36/41) rinsed their lenses and/or cases with tap water; 55% of soft-lens wearers wore their lenses while showering. The genotype of 9 isolates was determined, and all the strains belonged to genotype T4. In the orthokeratology group, the number of patients who required therapeutic penetrating keratoplasty after 2005 was less than that before 2005 (chi-square test, χ² = 4.209, P = 0.04).

Conclusions

More than two-thirds of the cases were associated with orthokeratology. Examinations with Giemsa-stained smears, 0.9% NaCl wet mounts and confocal microscopy should be performed for patients who are highly suspected of having early-stage AK to help with early diagnosis. In the orthokeratology group, the rate of therapeutic keratoplasty after 2005 was less than that before 2005.

Electronic supplementary material

The online version of this article (10.1186/s12886-019-1210-2) contains supplementary material, which is available to authorized users.

The rising incidence of Acanthamoeba keratitis: A 7-year nationwide survey and clinical assessment of risk factors and functional outcomes

Purpose

To evaluate the incidence of Acanthamoeba keratitis in the Netherlands between 2009 and 2015 and to analyse predicting factors for treatment outcome.

Methods

Patient characteristics, diagnostic methods, diagnostic delay, therapy prior to and after diagnosis, and visual outcome were obtained from medical files of all patients diagnosed with Acanthamoeba keratitis in the Netherlands between 2009 and 2015. A logistic regression analysis on treatment failure, defined as a best corrected visual acuity of less than 20/40 Snellen decimals (i.e. >0.3 logMAR or an approximate loss of three lines of visual acuity) and/or the need for keratoplasty, was performed to determine predicting factors.

Results

Two hundred and twenty-four eyes of 224 patients were included. Ninety-five percent of the patients were contact lens wearers, of whom 74% wore soft contact lenses. The number of cases increased from 16 in 2009 to 49 in 2015. This resulted in an estimated incidence of 1 in 21,000 for soft contact lens wearers in 2015. Eighty-seven eyes (39%) met the criteria for treatment failure. In a multivariable regression analysis, higher age at presentation, a higher severity stage and corticosteroid use before diagnosis were positively correlated with treatment failure. Early referral to a cornea specialist was associated with better clinical outcomes.

Conclusions

Although Acanthamoeba keratitis is still a relatively uncommon disease, the incidence in soft contact lens wearers has increased to reach 1 in 21,000 in 2015. Treatment failure occurred in 39% of cases, with age, higher severity stage, corticosteroid use before diagnosis and indirect referral to a cornea specialist as important risks factors.

Queensland Microbial Keratitis Database: 2005–2015

Aims

To estimate the incidence of culture-positive microbial keratitis in Queensland and analyse trends in the organisms and their sensitivities cultured from corneal scrapes, especially low-incidence organisms.

Methods

Retrospective multicentre case series of all positive corneal scrapes in Queensland, Australia between 2005 and 2015. Pathology organisations in Queensland were identified by online and local directory search and agreed to participate. Digital records of scrapes provided patient demographics and culture and susceptibility results. Trends in the incidence, organisms and sensitivities were monitored with linear regression. The yearly incidence of microbial keratitis was estimated from the Queensland population.

Results

The included corneal scrapes totalled 3182, while 1006 were excluded. The included scrapes yielded 4111 organisms. Pseudomonas aeruginosa was the most common single isolate (729, 17.7%), although Gram-positive organisms were more common overall (2737, 66.6%). Fungal organisms were cultured in 6% of cases, while Acanthamoeba comprised only 1% of records. Bacterial organisms were sensitive to all recorded antibiotics in 89% of all isolates and none of the reported antibiotics showed a decreasing trend in susceptibility. The incidence of protozoal isolation decreased over time (p=0.055). Cultures positive for yeasts showed a linear increase in incidence (p=0.045) while moulds showed a spike in incidence in 2010–2012 (p=0.0008).

Conclusion

The estimated incidence of microbial keratitis was 0.66 cases per 10 000 people, the rate of antibiotic susceptibility is high and stable, the incidence of keratitis secondary to protozoa is likely to be decreasing while the incidence of keratitis culturing yeast is increasing.

Risk factors and clinical signs of severe Acanthamoeba keratitis

Purpose

To determine risk factors and clinical signs for severe Acanthamoeba keratitis (AK) by comparing severe cases with mild cases with good prognosis.

Patients and methods

We reviewed medical records of ten cases of AK (five males and five females) referred to our hospital and classified cases into two groups. One eye that required therapeutic keratoplasty and three eyes with a poor visual acuity (<0.2) on last visit were included in the severe group. Six eyes that had good prognosis with a visual acuity of 1.2 on last visit were classified as mild group. We compared patients’ age, the time required for diagnosis, visual acuity on first visit, the history of steroid eye drops use, and other clinical findings.

Results

The average age of the severe group was older than the mild group (P=0.04). The duration between onset and diagnosis of AK and visual acuity on first visit was not statistically different. A history of steroid eye drop use was found in four eyes of the severe group (100%) and four eyes of the mild group (67%). Keratoprecipitates were found in all severe group eyes and one mild group eye during follow-up (P=0.01). One case in the severe group was diagnosed with diabetes mellitus at initial examination. We detected Staphylococcus epidermis by palpebral conjunctival culture in one case of the severe group.

Conclusion

Aging may be a possible risk factor for severe AK. The presence of keratoprecipitates is a possible sign of severe AK. Attention is also required in patients with comorbidities such as diabetes mellitus and bacterial infection.

Tannic acid-modified silver nanoparticles as a novel therapeutic agent against Acanthamoeba

Free-living amoebae belonging to Acanthamoeba genus are widely distributed protozoans which are able to cause infection in humans and other animals such as keratitis and encephalitis. Acanthamoeba keratitis is a vision-threatening corneal infection with currently no available fully effective treatment. Moreover, the available therapeutic options are insufficient and are very toxic to the eye. Therefore, there is an urgent need for the development of more effective anti-amoebic agents. Nanotechnology approaches have been recently reported to be useful for the elucidation antimicrobial, antiviral, antifungal and antiprotozoal activities and thus, they could be a good approach for the development of anti-Acanthamoeba agents. Therefore, this study was aimed to explore the activity and cytotoxicity of tannic acid-modified silver nanoparticles, pure silver nanoparticles and pure gold nanoparticles against clinical strains of Acanthamoeba spp. The obtained results showed a significant anti-amoebic effect of the tannic acid-modified silver nanoparticles which also presented low cytotoxicity. Moreover, tannic acid-modified silver nanoparticles were well absorbed by the trophozoites and did not induce encystation. On the other hand, pure silver nanoparticles were only slightly active against the trophozoite stage and pure gold nanoparticles did not show any activity. In conclusion and based on the observed results, silver nanoparticle conjugation with tannic acid may be considered as potential agent against Acanthamoeba spp.