Fusarium Keratitis-Review of Current Treatment Possibilities

Treatment Strategies for Filamentous Fungi Keratitis

INTRODUCTION

This research aims to describe clinical findings, epidemiology and treatment outcomes in patients with filamentous fungi keratitis of a tertiary centre in Germany over a 7-year period and to compare the efficacy of different antifungal treatments and the effect of additive topical steroids.

METHODS

This retrospective study included 25 eyes of 23 patients from October 2013 to December 2020 with cultural isolates of filamentous fungi and corresponding keratitis. Best-corrected visual acuity (BCVA), clinical signs, symptoms, risk factors and outcome were extracted from medical records.

RESULTS

Improvement of BVCA was noted in 68% of eyes. Mean BCVA of the study population increased from 0.75 logMAR [median 0.40, standard deviation (SD) 0.82, range 0-2.3] to 0.48 logMAR (median 0.10, SD 0.88, range - 0.1 to 3). The most commonly used antifungal topical treatment was a combination of natamycin 5% and voriconazole 2% (44% of eyes), followed by voriconazole 2% in 36% of cases. An antiinflammatory topical steroid was applied in 52%. In 16% of the eyes, penetrating keratoplasty (pKP) was performed.

CONCLUSION

Diagnosis of filamentous fungi keratitis is often difficult or delayed. Outcomes can be poor even with intensive treatment because of high resistance to common antifungals. Access to natamycin 5% seems to lead to favourable outcomes in filamentous fungi keratitis.

Immune Mechanisms of Filamentous Fungal Keratitis

Filamentous fungal keratitis is a particularly serious eye infection that often results in ulceration, corneal perforation, and blindness. The cornea acts as a natural barrier against harmful agents due to the close connection of its epithelial cells. In addition, on its surface, there is a large number of substances with anti-inflammatory and bactericidal properties, such as secretory IgA and mucin glycoproteins, and antimicrobial peptides (AMPs), such as human β-defensin 2 (HBD-2) and LL-37, which are especially increased in filamentous fungal keratitis. The interaction between pathogenic fungi and the host's immune mechanisms is a complex process: pathogen-associated molecular pattern (PAMP) molecules (chitin, β-glucan, and mannan) found in the fungal cell wall are recognized by pattern recognition receptors (PRRs) (toll-like receptors {TLRs}, C-type lectin receptors {CLRs}, nucleotide-binding oligomerization domain-like receptors {NLRs}, and scavenger receptors {SR}) found in host defense cells, triggering the secretion of various types of cytokines, such as interleukins (IL), tumor necrosis factors (TNFs), and chemokines, which recruit macrophages and neutrophils to migrate to the site of infection and activate inflammatory responses. In addition, the interaction of hyphae and corneal epithelial cells can activate cluster of differentiation (CD) 4+ T cells, CD8+ T cells, and B cells and induce secretion of T-helper (Th)-type cytokines 2 (IL-4 and IL-13) and IgG.

Sir2-mediated cytoplasmic deacetylation facilitates pathogenic fungi infection in host plants

Lysine acetylation is an evolutionarily conserved and widespread post-translational modification implicated in the regulation of multiple metabolic processes, but its function remains largely unknown in plant pathogenic fungi. A comprehensive analysis combined with proteomic, molecular and cellular approaches was presented to explore the roles of cytoplasmic acetylation in Fusarium oxsysporum f.sp. lycopersici (Fol). The divergent cytoplasmic deacetylase FolSir2 was biochemically characterized, which is contributing to fungal virulence. Based on this, a total of 1752 acetylated sites in 897 proteins were identified in Fol via LC-MS/MS analysis. Further analyses of the quantitative acetylome revealed that 115 proteins representing two major pathways, translational and ribosome biogenesis, were hyperacetylated in the ∆Folsir2 strain. We experimentally examined the regulatory roles of FolSir2 on K271 deacetylation of FolGsk3, a serine/tyrosine kinase implicated in a variety of cellular functions, which was found to be crucial for the activation of FolGsk3 and thus modulated Fol pathogenicity. Cytoplasmic deacetylation by FolSir2 homologues has a similar function in Botrytis cinerea and likely other fungal pathogens. These findings reveal a conserved mechanism of silent information regulator 2-mediated cytoplasmic deacetylation that is involved in plant-fungal pathogenicity, providing a candidate target for designing broad-spectrum fungicides to control plant diseases.

Recent Advances in Diagnosis and Treatment Approaches in Fungal Keratitis: A Narrative Review

Fungal keratitis represents a potentially sight-threatening infection associated with poor prognosis, as well as financial burden. Novel diagnostic methods include polymerase-chain-reaction (PCR)-based approaches, metagenomic deep sequences, in vivo confocal microscopy, and antifungal susceptibility testing. The ideal therapeutic approaches and outcomes have been widely discussed in recent times, with early therapy being of the utmost importance for the preservation of visual acuity, minimizing corneal damage and reducing the scar size. However, combination therapy can be more efficacious compared to monotherapy. Understanding the pathogenesis, early diagnosis, and prevention strategies can be of great importance. In this narrative, we discuss the recent progress that may aid our understanding of the diagnosis, treatment, and prevention of mycotic keratitis.

Fungal Diseases Caused by Serious Contamination of Pharmaceuticals and Medical Devices, and Rapid Fungal Detection Using Nano-Diagnostic Tools: A Critical Review

Fungal-contaminated compounded pharmaceuticals and medical devices pose a public health problem. This review aimed to provide an organized overview of the literature on that critical issue. Firstly, it was found that compounding pharmacies can produce drugs that are contaminated with fungi, leading to outbreaks of severe fungal diseases. Secondly, inadequate sterile compounding techniques or storage conditions, or exceeding the limit of a fungal count, can result in fungal contamination. Lastly, nanotools can be used to rapidly detect fungi, thus improving fungal diagnostic procedures. To achieve this goal, we have reviewed the published data on PubMed, the CDC, and FDA Web sites, and a literature search was undertaken to identify severe fungal infections associated with compounding pharmacies outside of hospitals, limited by the dates 2003 to 2021. The "Preferred Reporting Items for Critical Reviews" were followed in searching, including, and excluding papers. Fungal outbreaks have been documented due to contaminated pharmaceuticals and medical devices. In 2013, 55 people died from fungal meningitis caused by contaminated steroid injections containing methylprednisolone acetate. Additionally, in 2021, Aspergillus penicillioides contamination was reported in ChloraPrep drugs, which was attributed to the storage conditions that were conducive to the growth of this fungus. These incidents have resulted in severe infectious diseases, such as invasive mycoses, cornea infections, Endophthalmitis, and intestinal and gastric mycosis. By implementing preventive measures and policies, it is possible to avoid these outbreaks. Creating Nano-diagnostics presents a major challenge, where promptly diagnosing fungal infections is required to determine the proper corrective and preventive measures.

Fusarium Keratitis on the Rise - a Clinical Review

Fungal keratitis due to Fusarium species is a rare but serious ocular disease. Due to its rapid progression, often late diagnostic confirmation as well as limited topical treatment options, this is potentially sight threatening. Increasing contact lens use and global climate change have been suggested to be factors leading to an increase in cases of fusarium keratitis, even in regions with moderate climate. Early recognition and initiation of antimycotic treatment, as well as early surgical treatment by penetrating keratoplasty are decisive for the outcome.

Repeated Intracameral Amphotericin B: A Safe Approach for Management of Fungal Anterior Chamber Reactivations After Therapeutic Penetrating Keratoplasty

PURPOSE

The aim of this study was to describe the safe use of repeated intracameral amphotericin B for anterior chamber reactivations after therapeutic penetrating keratoplasty for Fusarium solani keratitis.

METHODS

A 49-year-old woman monthly soft contact lens wearer with a history of overuse and swimming in her lenses presented with a red painful left eye. Her vision was 0.5 logMAR and there was a poorly demarcated corneal infiltrate. Although corneal scrapes and a corneal biopsy were negative, confocal microscopy showed fungal hyphae. After failure of medical treatment, therapeutic penetrating keratoplasty was performed. Fusarium solani sensitive to amphotericin was isolated. There was pan-azole resistance. The patient was managed with topical amphotericin B, and repeated anterior chamber reactivations were managed with intracameral amphotericin B 5 µg in 0.1 mL on 9 occasions over 5 months after sensitivities were known. Topical cyclosporine was used as the sole immunomodulator postoperatively, with no topical steroid use over the 4-year follow-up period.

RESULTS

There were no episodes of graft rejection and no endothelial, lenticular, or retinal toxicity. The best-corrected visual acuity is -0.1 logMAR and the endothelial cell count is 2160/mm 2 .

CONCLUSION

This report describes the safe and effective use of repeated intracameral amphotericin (cumulative 45 µg) in anterior chamber reactivations after therapeutic penetrating keratoplasty and highlights the role of fungal sensitivity in guiding treatment in refractory cases. It also demonstrated the successful use of topical cyclosporin as the sole postoperative immunomodulatory therapy despite repeated recurrence of infection and consequent increased inflammation in the postoperative period.

Intracameral Drug Delivery: A Review of Agents, Indications, and Outcomes

An intracameral (IC) injection directly delivers the drug into the anterior chamber of the eye. This targeted drug delivery technique overcomes the ocular barriers and offers a high therapeutic concentration of medication at the desired site and consequently better clinical outcomes. IC drug delivery is a safe and effective modality with many advantages over topical delivery. These include excellent bioavailability, reduced systemic risk, and minimal ocular toxicity. Agents delivered via IC injection have shown promising results against infection, inflammation, ocular hypertension, and neovascularization. Current literature shows that IC antibiotics, including cefuroxime, vancomycin, and moxifloxacin, are routinely used for prophylaxis of endophthalmitis. Other drugs available for IC use are steroids, anesthetics, mydriatics, miotics, antivascular endothelial growth factor, antiglaucoma, and alkylating agents. Introduction of sustained-release devices containing dexamethasone or Bimatoprost in anterior chamber via IC route has the potential in treating ocular inflammation and raised intraocular pressure. The complications such as hemorrhagic occlusive retinal vasculitis and toxic anterior segment syndrome have been documented with IC prophylaxis but are rare. In this review, we provide an overview of available IC drugs, their pharmacokinetics, the spectrum of activity, dosage and preparation, prophylactic and therapeutic usage, clinical efficacy, and safety profiles.

A 5-Year Retrospective Analysis of the Risk Factors, Treatment, and Prognosis of Patients With Fungal Keratitis in Heilongjiang, China

PURPOSE

To report the epidemiologic features, laboratory findings, and treatment outcomes of patients with fungal keratitis (FK) during a busy farming period (May, June, and September to November) in Heilongjiang Province, China.

DESIGN

Retrospective, observational case series.

METHODS

In total, 251 patients diagnosed with FK at the Eye Hospital, First Affiliated Hospital of Harbin Medical University, from 2017 to 2021 were identified. Medical records were retrospectively analyzed, and demographic features, risk factors, monthly distributions, clinical characteristics, laboratory findings, treatment strategies, and prognostic data were collected.

RESULTS

The number of FK cases in the busy farming period accounted for 74.1% (186/251) of the total. The mean patient age was 58.2±9.5 years. Males (66.7%) were more likely to develop FK than females (33.3%), and plant-related trauma was the main cause in 80.1% (149/186) of the cases. The most common causative fungal species was Fusarium (34.9%). In vivo confocal microscopy had the highest positivity rate for FK diagnosis (94.6%). The depth of hypopyon, depth of hyphae or spores, and infiltrate width were significantly positively correlated with delayed presentation.

CONCLUSIONS

Patients with a longer time of presentation to the hospital were more likely to undergo surgery because of topical medical therapy failure. The most important measures for FK prevention are the use of eye protection during outdoor work and visiting the hospital for treatment as soon as possible after eye injury.