Global research on keratomycosis: New insights from latent Dirichlet allocation and HJ-Biplot-driven knowledge mapping study.

BACKGROUND: Keratomycosis is a form of infectious keratitis, an infection of the cornea, which is caused by fungi. This disease is a leading cause of ocular morbidity globally with at least 60 % of the affected individuals becoming monocularly blind. OBJECTIVE: This bibliometric analysis aimed to comprehensively assess the existing body of literature, providing insights of the evolution of keratomycosis research by identifying key themes and research gaps. METHODS: This work used the modeling method Latent Dirichlet Allocation (LDA) to identify and interpret scientific information on topics concerning existing categories in a set of documents. The HJ-Biplot method was also used to determine the relationship between the analyzed topics, taking into consideration the years under study. RESULTS: This bibliometric analysis was performed on a total of 2,599 scientific articles published between 1992 and 2022. The five leading countries with more scientific production and citations on keratomycosis were The United States of America, followed by India, China, United Kingdom and Australia. The top five topics studied were Case Reports and Corneal Infections, which exhibited a decreasing trend; followed by Penetrating Keratoplasty and Corneal Surgery, Ocular Effects of Antifungal Drugs, Gene Expression and Inflammatory Response in the Cornea and Patient Data which have been increasing throughout the years. However Filamentous Fungi and Specific Pathogens, and Antifungal Therapies research has been decreasing in trend. CONCLUSION: Additional investigation into innovative antifungal drug therapies is crucial for proactively tackling the potential future resistance to antifungal agents in scientific writing.

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.

Scedosporium apiospermium keratitis: a case report.

BACKGROUND: Scedosporium apiospermum, an opportunistic and filamentous fungus, is a rarely seen ocular entity that is difficult to identify and heal. We report a challenging case of S. apiospermium keratitis and discuss the treatment modalities in light of previous studies. CASE PRESENTATION: A 30-year-old Turkish farmer with a history of contact lens misuse presented to our clinic with a painful corneal abscess and severe vision loss in his left eye. S. apiospermum was identified by spectrophotometric analysis. The patient was successfully treated with therapeutic penetrating keratoplasty, but was resistant to fluconazole and amphotericin B and susceptible but unresponsive to voriconazole. CONCLUSION: S. apiospermum keratitis should be considered in the differential diagnosis of immunocompromised and immunocompetent patients with history of ocular trauma and contact lens use, especially those who do not respond to treatment.

Microbial Profile and Clinical Outcomes of Fungal Keratitis at a Single-Center Tertiary Care Hospital.

PURPOSE: To evaluate baseline characteristics, microbiological spectrum, management, and outcomes of patients with culture-proven fungal keratitis. METHODS: Retrospective review of all patients with culture-proven fungal keratitis seen over 6 years at a tertiary referral center. RESULTS: The present study included 62 eyes from 62 patients. Infection with filamentous organisms was more common than with yeast (66.1% vs 27.4%). The most common filamentous organisms were Fusarium (17.7%) and Aspergillus (16.1%), while the most common yeast was Candida (24.2%). The main predisposing factor for filamentous keratitis was contact lens use. Yeast keratitis is most associated with an immunocompromised host and ocular surface disease. Corneal perforation (20.0%) and surgical interventions (46.8%) were common, with 27.4% of eyes requiring at least one penetrating keratoplasty. Filamentous keratitis is more likely than yeast keratitis to require urgent penetrating keratoplasty or enucleation and to receive more than one topical and systemic antifungal agent. Visual outcomes were poor with nearly half of the eyes remaining at 20/200 or worse upon resolution of infection. Worse visual outcomes were associated with poor vision at presentation and a history of ocular surface disease. Antifungal susceptibility testing was not routinely performed, but it demonstrated a relatively high minimum inhibitory concentration for at least one antifungal drug in 90% of cases when performed (16.1%) and guided the direction of treatment for 80% of the cases. CONCLUSION: Fungal keratitis is visually devastating. Infections with filamentous fungi predominated over yeast and were generally treated more aggressively both medically and surgically. Filamentous and yeast keratitis had similar durations of infections and visual outcomes. Antifungal susceptibility testing influenced treatment in 80% of cases in which it was performed.

Diagnosing Fungal Keratitis and Simultaneously Identifying Fusarium and Aspergillus Keratitis with a Dot Hybridization Array.

Fungal keratitis (FK) is one of the most common microbial keratitis, which often leads to poor prognosis as a result of delayed diagnosis. Several studies implied that early differentiation of the two major FK, Fusarium and Aspergillus keratitis, could be helpful in selecting effective anti-fungal regimens. Therefore, a novel dot hybridization array (DHA) was developed to diagnose FK and differentiate Fusarium and Aspergillus keratitis in this study. One hundred forty-six corneal scrapes obtained from one hundred forty-six subjects impressed with clinically suspected FK were used to evaluate the performance of the DHA. Among these patients, 107 (73.3%) patients had actual FK confirmed by culture and DNA sequencing. We found that the DHA had 93.5% sensitivity and 97.4% specificity in diagnosing FK. In addition, this array had 93.2% sensitivity and 93.8% specificity in diagnosing Fusarium keratitis, as well as 83.3% sensitivity and 100% specificity in diagnosing Aspergillus keratitis. Furthermore, it had 83.9% sensitivity and 100% specificity in identifying Fusarium solani keratitis. Thus, this newly developed DHA will be beneficial to earlier diagnosis, more precise treatment, and improve prognosis of FK, by minimizing medical refractory events and surgical needs.

Mycotic Keratitis-A Global Threat from the Filamentous Fungi.

Mycotic or fungal keratitis (FK) is a sight-threatening disease, caused by infection of the cornea by filamentous fungi or yeasts. In tropical, low and middle-income countries, it accounts for the majority of cases of microbial keratitis (MK). Filamentous fungi, in particular Fusarium spp., the aspergilli and dematiaceous fungi, are responsible for the greatest burden of disease. The predominant risk factor for filamentous fungal keratitis is trauma, typically with organic, plant-based material. In developed countries, contact lens wear and related products are frequently implicated as risk factors, and have been linked to global outbreaks of Fusarium keratitis in the recent past. In 2020, the incidence of FK was estimated to be over 1 million cases per year, and there is significant geographical variation; accounting for less than 1% of cases of MK in some European countries to over 80% in parts of south and south-east Asia. The proportion of MK cases is inversely correlated to distance from the equator and there is emerging evidence that the incidence of FK may be increasing. Diagnosing FK is challenging; accurate diagnosis relies on reliable microscopy and culture, aided by adjunctive tools such as in vivo confocal microscopy or PCR. Unfortunately, these facilities are infrequently available in areas most in need. Current topical antifungals are not very effective; infections can progress despite prompt treatment. Antifungal drops are often unavailable. When available, natamycin is usually first-line treatment. However, infections may progress to perforation in ~25% of cases. Future work needs to be directed at addressing these challenges and unmet needs. This review discusses the epidemiology, clinical features, diagnosis, management and aetiology of FK.

Recent advances on mycotic keratitis caused by dematiaceous hyphomycetes.

Dematiaceous hyphomycetes (DH) are darkly pigmented fungi ubiquitously found all over the world as plant pathogens and saprophytes, and many of the members of this group have emerged as opportunistic pathogens. These fungi are responsible for a wide variety of infections including mycotic keratitis, which is considered as one of the major causes of corneal blindness, particularly in tropical and subtropical countries with an annual global burden of about 1 000 000 patients. The infection is more common in workers working in an outdoor environment. Moreover, trauma is found to be the most important predisposing cause of mycotic keratitis. Considerable delay in diagnosis and scarcity of effective pharmacological drugs are the major factors responsible for increased morbidity and visual impairment. Considering the crucial role of DH in mycotic keratitis, in the present review, we have focused on major DH with special emphasis on their pathogenicity, diagnosis and treatment strategies.

Mycotic keratitis due to Cylindrocarpon lichenicola: Successful salvage of the eye.

We hereby report a successfully salvaged eye due to mycotic keratitis by Cylindrocarpon lichenicola in a 60-year-old female from Kasaragod (Kerala). The patient came with a history of pain, photophobia and decreased vision of the right eye. The microbiological investigations of the corneal scraping revealed C. lichenicola. C. lichenicola is a soil saprophyte. Since the ulcer worsened paracentesis followed by therapeutic keratoplasty and adjunct therapy with natamycin drops, voriconazole drops and oral ketoconazole was given. We stress that evidence-based timely medical and surgical intervention helped in the restoration of the vision in an infected eye.

Deciphering potential inhibitors targeting THI4 of Fusarium solani sp. to combat fungal keratitis: An integrative computational approach.

Mycotic keratitis is a fungal infection of corneal epithelium. It is more common in tropical and subtropical countries and is one of the leading causes of blindness. Many of the antifungal drugs have been less effective in treating this condition and certain drugs which are efficient and yet limited in use due to its extreme side effects. Hence, in this study an attempt is made to identify potential and least toxic antifungal inhibitors that targets thiamine thiazole synthase, a novel target for suppressing Fusarium solani subsp.pisi (Nectria haematococca MPVI) infections, to combat mycotic keratitis. Integrative computational approaches involving model refinement, molecular dynamics simulation and High throughput virtual screening (HTVS) were applied through integrative multi precision mode in order to identify potential inhibitors. Moreover, machine learning approach was also implemented to prioritize potential inhibitors that are ophthalmic adaptive, as well as antifungal molecule. From the NCI and Maybridge datasets, for HTVS only 209,872 compounds that surpassed ligand property filtration were considered, which resulted in 209 compounds after XP docking. Among the top 5 compounds from XP docking, on cumulative analysis only 2-(1-hydroxyethyl)-1,3-thiazole-4-carboxamide was prioritized as the most potential hit, as it showed higher order of significance in terms of binding affinity, structural stability and therapeutic relevance for the treatment of Mycotic keratitis. Thus, widening the scope for novel antifungal therapy in ophthalmic infections.

Self-nanoemulsifying drug delivery system to improve transcorneal permeability of voriconazole: in-vivo studies.

OBJECTIVE: This study investigates the effectiveness of self-nanoemulsifying drug delivery system (SNEDDS) in improving voriconazole transcorneal permeability. METHODS: Voriconazole-SNEDDS was prepared with isopropyl myristate, PEG 400, Tween 80® and Span 80® and was subjected for physicochemical characterization after reconstitution with NaCl 0.9% (1/9; v/v). In-vitro antifungal activity was assessed and compared with the marketed formulation. In-vivo studies, namely ocular irritation test via modified Draize test and pharmacokinetic study, were investigated using rabbit as animal model. KEY FINDINGS: Voriconazole-SNEDDS presented a droplet size of 21.353 ± 0.065 nm, a polydispersity index of 0.123 ± 0.003, a pH of 7.205 ± 0.006 and an osmolarity of 342.667 ± 2.517 mOsmol/l after reconstitution with NaCl 0.9%. Voriconazole-SNEDDS minimum inhibitory concentration (MIC90 ) was similar to the one of marketed formulation for Candida species while it was significantly lower (P < 0.001) for Aspergillus fumigatus. Draize test revealed that Voriconazole-SNEDDS was safe for ocular administration. Voriconazole maximum concentration (5.577 ± 0.852 µg/ml) from SNEDDS was higher than marketed formulation (Cmax  = 4.307 ± 0.623 µg/ml), and the Tmax was delayed to 2 h. The area under the concentration-time curve value of Voriconazole-SNEDDS was improved by 2.419-fold. CONCLUSION: Our results suggest that SNEDDS is a promising carrier for voriconazole ocular delivery and this encourages further clinical studies.

Evaluation of in vitro activities of extracellular enzymes from Aspergillus species isolated from corneal ulcer/keratitis.

Mycotic/fungal keratitis is a suppurative, generally ulcerative infection of the cornea. The filamentous fungi, Aspergillus spp. are the second leading cause of mycotic keratitis, particularly in India. Aspergillus spp. produce a range of extracellular enzymes that are used to break down complex molecules and used for growth and reproduction, also for survival on/in host organism. The current study was designed with an objective to screen in vitro extracellular enzyme activity of Fusarium and Aspergillus isolates from mycotic keratitis patients and to correlate the same as a putative virulence factor. Extracellular enzymes viz., deoxyribonuclease (DNase), protease, lipase, elastase, keratinase, etc., produced by Aspergillus have key role in keratomycosis and hence their (n = 85) in vitro activities were investigated. It was found that, the majority of the Aspergillus isolates produced protease (n = 75; 88% of 85) followed by lipase (n = 59; 69% of 85), DNase (n = 35; 41% of 85), elastase (n = 26; 31% of 85) and keratinase (n = 13; 15% of 85). The enzyme activity indices (EAI) for DNase, elastase, protease and lipase ranged between 1.01 and 1.98, whereas elastase EAI varied between 1.26 and 1.92. DNase, protease and lipase showed a maximum EAI of 1.98 and lowest EAI value of 1.01, respectively. Extracellular enzymes of Aspergillus spp. may have potential role in the onset and progression of keratitis.

Voriconazole-loaded self-nanoemulsifying drug delivery system (SNEDDS) to improve transcorneal permeability.

The aim of this study was to develop self- nanoemulsifying drug delivery system (SNEDDS) to improve the transcorneal permeability of voriconazole. A 'mixture design around a reference mixture' approach was applied. This latter included four components, namely, isopropyl myristate, PEG 400, Tween® 80 and Span® 80 as oil, co-solvent, surfactant and co-surfactant, respectively. Droplet size was selected as response. The effect of mixture components on droplet size was analyzed by means of response trace method. Optimal formulation was subjected to stability studies and characterized for droplet size, polydispersity index (PDI), pH, osmolarity, viscosity and percentage of transmittance. Ex-vivo transcorneal permeation of the optimal and the marketed formulations was carried out on excised bovine cornea using Franz cell diffusion apparatus. Optimal voriconazole loaded-SNEDDS showed moderate emulsification efficiency and was characterized by a droplet size of 21.447 ± 0.081 nm, a PDI of 0.156 ± 0.004, a pH of 7.205 ± 0.006, an osmolarity of 310 mosmol/Kg and a viscosity of 8.818 ± 0.076 cP. Moreover, it presented an excellent stability and exhibited a significant improvement (p < 0.05) in apparent permeability coefficient (1.982 ± 0.187 × 10-6 cm/s) when compared to commercialized formulation (1.165 ± 0.106 × 10-6 cm/s). These results suggest that SNEDDS is a promising carrier for voriconazole ocular delivery.

Infectious Keratitis Caused by Rare and Emerging Micro-Organisms.

PURPOSE: To provide a comprehensive review of rare and emerging micro-organisms causing infectious keratitis. MATERIAL AND METHODS: A literature search was performed using PubMed Medline, Cochrane Library Database, EMBASE and Scopus (1960 onwards), using the terms: keratitis caused by rare pathogens; mycotic keratitis; fungal keratitis; bacterial keratitis; infectious keratitis; infective keratitis; atypical fungal keratitis; fungal keratitis caused by rare organisms; fungal keratitis caused by rare ocular pathogen; atypical bacterial keratitis; bacterial keratitis caused by rare organisms; bacterial keratitis caused by rare ocular pathogen. All relevant articles were included in this review. RESULTS: A total of 1232 articles matched our search strategy of which 124 articles were included in this mini-review. The rare and emerging bacteria causing keratitis include atypical mycobacteria, Nocardia spp., Chrysebacterium spp., Delftia acidovorans, Kocuria spp., Enterococcus spp., Bartonella henslae, Achromobacter spp. and others. The rare and emerging fungi causing keratitis include Pythium spp., Alternaria spp., Acremonium spp., Cladosporium spp., Curvularia spp., Bipolaris spp., Microsporidia spp., Pseudallescheria spp., Colletotrichum spp., and others. The clinical presentation of these cases is variable. While a few organisms produce characteristic clinical features, rest present similar to bacterial or fungal keratitis with variable response to routine treatment. A strong degree of suspicion is therefore essential for its diagnosis. Special investigations like polymerase chain reaction, gene sequencing, mass spectroscopy and enzyme-linked immunosorbent assay are required for accurate identification of these organisms. Culture-sensitivity is extremely useful as drug resistance to routinely used anti-microbial drugs is common. Prognosis is usually poor for keratitis with Pythium spp., Pseudallescheria spp., Arthrographis spp., Purpureocillium spp., Kociria spp. and Achromobacter spp. CONCLUSION: Keratitis caused by rare and emerging micro-organisms must be suspected in cases where the infection runs an unusual course or shows a poor response to standard anti-microbial drugs. Early diagnosis and timely treatment hold the key for a good outcome.

Severe mycotic keratoconjunctivitis caused by Fusarium sp. in an immunocompetent child successfully treated with intravenous voriconazole and keratoplasty: case report and short review of the literature.

BACKGROUND: Pediatric mycotic infections in the eye are uncommon. However, ophthalmic infections by several fungal species have been described in immunocompetent subjects. Mycotic keratitis with or without conjunctivitis (MK) may account for more than 50% of all cases, particularly in tropical and sub-tropical areas. The leading mechanism is trauma. Treatment of MK is managed by medical (antifungal agents) and/or surgical means. This is the first case report of a patient with MK by Fusarium spp. successfully treated with keratoplasty and intravenous voriconazole, along with topical natamycin. METHODS: Keratoplasty was performed and cultures obtained. Both Blood and Sabouraud Agars were used for cultures, and Lactophenol Cotton Blue Staining for microscopic observation. RESULTS: A healthy, 10 year-old female, from the sub-tropical area of Sinaloa, Mexico, was admitted at both the CODET Vision Institute and the General Hospital of Tijuana, Mexico. Seven days after a direct trauma of the right cornea, the patient complained of progressive blurred vision, burning sensation, and itchiness. Clinical examination showed severe keratoconjunctivitis, and a necrotic slough on the cornea. Fungal colonies grew, and microscopic visualization showed typical ovoid, sickle-cell shaped macroconidia characteristics of Fusarium spp. The patient received intravenous voriconazole (200 mg every 12 h) and topical natamycin for 7 days prior and 6 days after keratoplasty. Topical natamycin was continued for 3 weeks. At 1-month follow-up, the patient's outcome was significantly improved, with 90% vision recovery. CONCLUSION: This is the first pediatric case report of severe MK by Fusarium spp. successfully treated with combined intravenous voriconazole, keratoplasty and topical natamycin.

Pharmacologic therapy of mycotic keratitis.

Mycotic keratitis continues to be an important cause of corneal blindness, especially in tropical and subtropical countries. The prognosis is poor compared with many other forms of keratitis because of the lack of effective antifungal drugs. The currently available antifungal drugs suffer from multiple drawbacks such as poor ocular penetration, unpredictable bioavailability, and adverse effects associated with systemic medications. Over the last decade, several new drugs and drug-delivery systems have been introduced in an attempt to improve the treatment outcomes. Thorough knowledge of the currently available antifungal drugs, their spectrum of action, and associated adverse effects is essential to deal with cases of mycotic keratitis. We discuss the pharmacologic properties and clinical use of the currently available antifungal drugs.

Identification of the proteoforms of surface localized Rod A of Aspergillus flavus and determination of the mechanism of proteoform generation.

Fungal keratitis is a serious, potentially sight-threatening corneal infection that is more prevalent in the tropical parts of the world including India, and A. flavus and Fusarium solani are the predominant etiological agents. The surface of fungal conidia is covered by hydrophobin family proteins, effectively masking the conidial antigens from immune cells. In this study, we report that the outer cell wall layer of A. flavus conidia contain Rod A as well as other hydrophobins, which could be extracted by formic acid. Analysis of these surface proteins by mass spectrometry showed the presence of rodlet forming hydrophobins and other membrane and antigenic proteins. Our analysis revealed that Rod A existed as two proteoforms on the conidial surface. These proteoforms were separated using polyacrylamide gel electrophoresis and the amino acid sequence of these proteoforms was determined by high resolution mass spectrometry. PCR analysis of the mRNA encoding the Rod A showed the retention of intron one, which results in the formation of a truncated proteoform two. This is the first report in which the presence of RodA and its proteoforms and their mechanism of formation has been demonstrated in the corneal pathogenic fungus A. flavus. SIGNIFICANCE: A. flavus is a common fungal pathogen in tropical countries playing a predominant role in causing mycotic keratitis in humans. Surface of fungal conidia is immunologically inert primarily due to the hydrophobin family proteins forming a rodlet layer and masking the conidia from immune cells. In this study we demonstrated the existence two proteoforms of RodA/hydrophobin A and intron retention is shown to be responsible for the formation of one of the proteoforms. In addition, the spore surface proteins of A.flavus corneal isolates and saprophyte are distinctly different, which indicate the spore surface protein profile is ecotype specific. This is the first report showing the presence of two proteoforms of RodA on A.flavus conidial surface and demonstration of the mechanism of formation of the proteoforms.

Corneal Collagen Cross-Linking for the Management of Mycotic Keratitis.

PURPOSE: To evaluate the efficiency of corneal collagen cross-linking (CXL) in addition to topical voriconazole in cases with mycotic keratitis. DESIGN: Retrospective case series in a tertiary university hospital. PARTICIPANTS: CXL was performed on 13 patients with mycotic keratitis who presented poor or no response to topical voriconazole treatment. METHODS: The clinical features, symptoms, treatment results and complications were recorded retrospectively. The corneal infection was graded according to the depth of infection into the stroma (from grade 1 to grade 3). The visual analogue scale was used to calculate the pain score before and 2 days after surgery. MAIN OUTCOME MEASURES: Grade of the corneal infection. RESULTS: Mean age of 13 patients (6 female and 7 male) was 42.4 ± 17.7 years (20-74 years). Fungus was demonstrated in culture (eight patients) or cytological examination (five patients). Seven of the 13 patients (54%) were healed with topical voriconazole and CXL adjuvant treatment in 26 ± 10 days (15-40 days). The remaining six patients did not respond to CXL treatment; they initially presented with higher grade ulcers. Pre- and post-operative pain score values were 8 ± 0.8 and 3.5 ± 1, respectively (p < 0.05). CONCLUSIONS: The current study suggests that adjunctive CXL treatment is effective in patients with small and superficial mycotic ulcers. These observations require further research by large randomized clinical trials.

[Tintelnotia destructans: new enemy at the gates]. / Tintelnotia destructans: Ein neuer Feind vor dem Tore.

Tintelnotia destructans is a fungal species described for the first time in 2016, which can cause infections of the nails and of the cornea. We describe the second known case worldwide of Tintelnotia destructans-associated keratitis and its therapy. A good sensitivity for amphotericin B and voriconazole was demonstrated in the resistogram for the first time and the successful clinical course was confirmed. The present case study also shows the importance of intensive diagnostics in atypical microbial keratitis.

Exophiala phaeomuriformis keratitis in a subarctic climate region: a case report.

PURPOSE: To report a case of Exophiala phaeomuriformis mycotic keratitis in a patient from a subarctic climate region. Dematiaceous fungi (black yeasts) have been gaining importance as corneal keratitis and ulcer causative agents in certain regions, but no cases have been described in Scandinavia. METHODS: Case report of a patient with a persistent corneal erosion that eventually presented a brown-pigmented infiltrate. The patient had a history of several months of topical therapy comprising medication for glaucoma, corticosteroids and antibiotics. A therapeutic contact lens was used, and amniotic membrane transplantation was performed before the development of the pigmented infiltrate. RESULTS: Exophiala phaeomuriformis was identified on the microbiological cultures from the surgically obtained infiltrate scrapes. The patient responded to topical amphotericin and fluconazole, the erosion was cured and a stromal scar subsided. During follow-up, sequential slit-lamp images and anterior segment optical coherence tomography (OCT) scans were obtained. CONCLUSION: This is the first described case of keratitis caused by E. phaeomuriformis in a subarctic region, the first in Europe and, to our knowledge, the second reported case in the literature. It is important to remember that superficial corneal brown-pigmented infiltrates should raise the suspicion of an unusual fungal infection even in this climate. This is particularly important in patients with ocular surface disease treated with steroids and antibiotics for a long time.