Oral miltefosine for refractory Acanthamoeba 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.

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.

Determination of probability of causative pathogen in infectious keratitis using deep learning algorithm of slit-lamp images

Corneal opacities are important causes of blindness, and their major etiology is infectious keratitis. Slit-lamp examinations are commonly used to determine the causative pathogen; however, their diagnostic accuracy is low even for experienced ophthalmologists. To characterize the “face” of an infected cornea, we have adapted a deep learning architecture used for facial recognition and applied it to determine a probability score for a specific pathogen causing keratitis. To record the diverse features and mitigate the uncertainty, batches of probability scores of 4 serial images taken from many angles or fluorescence staining were learned for score and decision level fusion using a gradient boosting decision tree. A total of 4306 slit-lamp images including 312 images obtained by internet publications on keratitis by bacteria, fungi, acanthamoeba, and herpes simplex virus (HSV) were studied. The created algorithm had a high overall accuracy of diagnosis, e.g., the accuracy/area under the curve for acanthamoeba was 97.9%/0.995, bacteria was 90.7%/0.963, fungi was 95.0%/0.975, and HSV was 92.3%/0.946, by group K-fold validation, and it was robust to even the low resolution web images. We suggest that our hybrid deep learning-based algorithm be used as a simple and accurate method for computer-assisted diagnosis of infectious keratitis.

Acanthamoeba Keratitis: an update on amebicidal and cysticidal drug screening methodologies and potential treatment with azole drugs

Introduction: Acanthamoeba encompasses several species of free-living ameba encountered commonly throughout the environment. Unfortunately, these species of ameba can cause opportunistic infections that result in Acanthamoeba keratitis, granulomatous amebic encephalitis, and occasionally systemic infection.Areas covered: This review discusses relevant literature found through PubMed and Google scholar published as of January 2021. The review summarizes current common Acanthamoeba keratitis treatments, drug discovery methodologies available for screening potential anti-Acanthamoeba compounds, and the anti-Acanthamoeba activity of various azole antifungal agents.Expert opinion: While several biguanide and diamidine antimicrobial agents are available to clinicians to effectively treat Acanthamoeba keratitis, no singular treatment can effectively treat every Acanthamoeba keratitis case.Efforts to identify new anti-Acanthamoeba agents include trophozoite cell viability assays, which are amenable to high-throughput screening. Cysticidal assays remain largely manual and would benefit from further automation development. Additionally, the existing literature on the effectiveness of various azole antifungal agents for treating Acanthamoeba keratitis is incomplete or contradictory, suggesting the need for a systematic review of all azoles against different pathogenic Acanthamoeba strains.

Anterior Scleral and Limbal Inflammatory Necrosis After Adjuvant Miltefosine for Recalcitrant Acanthamoeba Keratitis

PURPOSE

The purpose of this study was to report a retrospective case series of anterior scleral and limbal inflammatory necrosis after adjuvant miltefosine for recalcitrant Acanthamoeba keratitis (AK).

METHODS

A case series and literature review.

RESULT

Four eyes of 3 patients with recalcitrant AK developed anterior scleral and limbal inflammatory necrosis with significant scleral-limbal thinning after treatment with miltefosine. The average age was 38 years, and the average duration of infection before miltefosine treatment was 239 days. All cases required urgent surgical intervention to either prevent or mitigate corneal-limbal perforation.

CONCLUSIONS

Miltefosine has been observed to result in the resolution of AK when used as an adjunctive therapy. It may also lead to a consecutive inflammatory necrosis of the anterior sclera and limbus. This inflammatory response may be significant enough to cause rapid scleral-limbal thinning with subsequent perforation.

Oral Miltefosine as Salvage Therapy for Refractory Acanthamoeba Keratitis

PURPOSE

To report a case series of patients with treatment-resistant Acanthamoeba keratitis (AK) using oral miltefosine, often as salvage therapy.

DESIGN

Descriptive, retrospective multicenter case series.

METHODS

We reviewed 15 patients with AK unresponsive to therapy who were subsequently given adjuvant systemic miltefosine between 2011 and 2017. The main outcome measures were resolution of infection, final visual acuity, tolerance of miltefosine, and clinical course of disease.

RESULTS

All patients were treated with biguanides and/or diamidines or azoles without resolution of disease before starting miltefosine. Eleven of 15 patients retained count fingers or better vision, and all were considered disease free at last follow-up. Eleven of 15 patients had worsening inflammation with miltefosine, with 10 of them improving with steroids. Six patients received multiple courses of miltefosine. Most tolerated oral miltefosine well, with mild gastrointestinal symptoms as the most common systemic side effect.

CONCLUSIONS

Oral miltefosine is a generally well-tolerated treatment adjuvant in patients with refractory AK. The clinician should be prepared for a steroid-responsive inflammatory response frequently encountered during the treatment course.

Orthokeratology lens-related Acanthamoeba keratitis: case report and analytical review

Acanthamoeba keratitis (AK) is a rare but severe ocular infection with a significant risk of vision loss. Contact lens use is the main risk factor for AK. The orthokeratology (OK) lens, a specially designed contact lens, has been used worldwide as an effective method of myopia control. However, the OK lens is associated with an increased risk of Acanthamoeba infection. Many primary practitioners are concerned about this infection because of its relative rarity, the lack of promising therapeutic medications, and the need for referral. We herein report two cases of AK associated with OK lenses, present a systematic review of such cases, and discuss the possible reasons for the higher incidence rate of this infection in patients who wear OK lenses. We combined the clinical knowledge and skills of corneal specialists and lens experts with the sole objective of addressing these OK lens-related AK cases. We found that the most common risk factors were rinsing the lenses or lens cases with tap water. Prompt and accurate diagnosis along with adequate amoebicidal treatment are essential to ensure desirable outcomes for OK lens wearers who develop AK. Appropriate OK lens parameters and regular checkups are also important.

Keratitis occurring in patients treated with miltefosine for post-kala-azar dermal leishmaniasis

AIM

To describe the characteristic clinical features and management of keratitis in the patients receiving miltefosine for post-kala-azar dermal leishmaniasis (PKDL).

METHODS

The medical records of five patients with PKDL who presented with keratitis were reviewed retrospectively from April 2018 to December 2019. The evaluation included a thorough medical history including details on drugs used, particularly miltefosine. The drug causality assessment was also performed. The clinical and microbiological characteristics of keratitis were noted.

RESULTS

The ocular symptoms included pain, redness, watering, photophobia and diminution of vision. Slit-lamp biomicroscopy revealed peripheral, paralimbal, ring-shaped, full-thickness stromal infiltration resulting in ulcerative keratitis in all cases. Two patients had unilateral keratitis, while three had bilateral keratitis. All five patients received miltefosine for an average period of 48 days before the onset of keratitis. The corrected distance visual acuity at presentation ranged from hand movement to 20/125. The causality assessment revealed a 'probable' association between the adverse drug reaction and miltefosine in all patients. Discontinuation of miltefosine and initiation of corticosteroid therapy resulted in resolution of keratitis in all cases. The unilateral keratitis treated with topical corticosteroids had improved outcomes, but poor outcomes were found in the bilateral keratitis.

CONCLUSION

These observations indicate that prolonged use of miltefosine might cause keratitis that resembles infectious keratitis. Early diagnosis with discontinuation of the drug and initiation of corticosteroid therapy are the key to successful management.

Alkyl-carbon chain length of two distinct compounds and derivatives are key determinants of their anti-Acanthamoeba activities

The opportunistic pathogen, Acanthamoeba castellanii is the causative agent for the sight threatening infection Acanthamoeba keratitis (AK). It is commonly associated with contact lens wearers, and prevalence is increasing at an alarming rate due to an inadequate preventive strategy to protect the lens from this protist. This problem is compounded by the lack of an effective acanthamoebocide, particularly with cysticidal activity in the contact lens solutions. We have used cytotoxicity assays and a variety of biophysical approaches to show that two molecules with tails made of alkyl carbon, alkylphosphocholines (APCs) and quaternary ammonium compounds (QACs) had significant chain-length dependent efficacy against A. castellanii trophozoites, the latter producing death via permeabilization, and DNA complexing. QACs were more effective than APCs and had activity against cysts. Conversely, the QAC with 12 alkyl carbon chain, was non toxic, its presence increased A. castellanii trophozoites biomass and delayed encystation by 96 h. Interestingly, it was unable to induce excystation and increased trophozoite sensitivity to APC16. These results present a mono- and multi-inhibitor management strategy effective against trophozoites and cysts that may be useful for formulating into contact lense cleaning solutions and reducing AK incidence.