Fungal keratitis: Pathogenesis, diagnosis and prevention

Fungal Keratitis in Northwestern Spain: Epidemiology, Risk Factors and Outcomes

PURPOSE

To review the clinical features, risk factors, microbiological profile, and treatment regimens of fungal keratitis in Galicia, a region in Northwestern Spain with temperate humid weather.

PATIENTS AND METHODS

A retrospective case series was employed, including patients with fungal keratitis from nine hospitals within the region of Galicia, Spain, between 2010 and 2020. Data obtained from clinical records were analysed.

RESULTS

Out of 654 cases of infectious keratitis, 77 cases (9.9%) were identified as fungal keratitis. The median age of affected patients was 68.0 years, with a higher incidence in rural areas (62.3%). Candida spp. infections were the most frequent type (55.8%) and were associated with a higher median age than were the non-dermatophyte mould infections. The primary risk factors included steroid eyedrop use (29.9%), recent keratoplasty (18.2%), ocular trauma (19.5%), and contact with vegetable matter (11.7%). Most ulcers displayed stromal involvement, and 37.7% presented corneal thinning. The median duration of infection was longer in fungal than in bacterial keratitis, and surgical intervention was required in 48.1% of cases.

CONCLUSIONS

Fungal keratitis, mainly involving Candida spp., accounted for 9.9% of microbial keratitis cases in Galicia, Spain, with significant risk factors being topical steroid use, ocular trauma, and contact with vegetable matter. Delayed diagnosis often resulted in poor outcomes, highlighting the need for early detection through awareness and new technologies to improve prognosis.

Fusarium spp.: infections and intoxications

The genus Fusarium, member of the Hypocreaceae family, comprises over 500 spp. with an ever-evolving taxonomy. These fungi, some highly pathogenic, primarily affect various plants, including major crops like maize, rice, cereals, and potatoes, leading to significant agricultural losses and contributing to human undernutrition in certain regions. Additionally, Fusarium spp. produce harmful mycotoxins like trichothecenes, fumonisins, zearalenones, etc., posing health risks to animals and humans. These toxins generally transferred to food items can cause diverse issues, including organ failure, cancer, and hormonal disturbances, with effects sometimes appearing years after exposure. The fungi's vast genetic repertoire enables them to produce a range of virulence factors, leading to infections in both animals and humans, particularly in immunocompromised individuals. Fusarium spp. can cause systemic infections and local infections like keratitis. Due to limited antifungal effectiveness and biofilm formation, these infections are often challenging to treat with poor outcomes.

Nanomaterial-based therapeutics for enhanced antifungal therapy

The application of nanotechnology in antifungal therapy is gaining increasing attention. Current antifungal drugs have significant limitations, such as severe side effects, low bioavailability, and the rapid development of resistance. Nanotechnology offers an innovative solution to address these issues. This review discusses three key strategies of nanotechnology to enhance antifungal efficacy. Firstly, nanomaterials can enhance their interaction with fungal cells via ingenious surface tailoring of nanomaterials. Effective adhesion of nanoparticles to fungal cells can be achieved by electrostatic interaction or specific targeting to the fungal cell wall and cell membrane. Secondly, stimuli-responsive nanomaterials are developed to realize smart release of drugs in the specific microenvironment of pathological tissues, such as the fungal biofilm microenvironment and inflammatory microenvironment. Thirdly, nanomaterials can be designed to cross different physiological barriers, effectively addressing challenges posed by skin, corneal, and blood-brain barriers. Additionally, some new nanomaterial-based strategies in treating fungal infections are discussed, including the development of fungal vaccines, modulation of macrophage activity, phage therapy, the application of high-throughput screening in drug discovery, and so on. Despite the challenges faced in applying nanotechnology to antifungal therapy, its significant potential and innovation open new possibilities for future clinical antifungal applications.

Isoalantolactone: a review on its pharmacological effects

Isoalantolactone (ISA) is a sesquiterpene lactone that could be isolated from Inula helenium as well as many other herbal plants belonging to Asteraceae. Over the past 2 decades, lots of researches have been made on ISA, which owns multiple pharmacological effects, such as antimicrobial, anticancer, anti-inflammatory, neuroprotective, antidepressant-like activity, as well as others. The anticancer effects of ISA involve proliferation inhibition, ROS overproduction, apoptosis induction and cell cycle arrest. Through inhibiting NF-κB signaling, ISA exerts its anti-inflammatory effects which are involved in the neuroprotection of ISA. This review hackled the reported pharmacological effects of ISA and associated mechanisms, providing an update on understanding its potential in drug development.

Clinical Features, Risk Factors, and Management of Candida Keratitis

BACKGROUND/AIMS

To determine the clinical features, predisposing factors, and management of infectious keratitis caused by Candida spp.

METHODS

Retrospective chart review.

RESULTS

The medical records of 52 patients (54 eyes) with Candida keratitis were available for statistical analysis. Thinning of the corneal stroma was identified in 34 eyes (63.0%), and corneal perforation occurred in 16 eyes (29.6%). Corneal thinning and perforation were more common in Candida albicans compared with non-albicans (P-val < .001, P = .09, respectively). The most common predisposing factors for Candida keratitis were topical steroid use (21 patients, 40.4%), previous corneal transplantation (17 patients, 32.7%), and preexisting ocular surface disease (15 patients, 28.8%). Fourteen eyes (25.9%) required cyanoacrylate glue application and 10 eyes (18.5%) underwent therapeutic penetrating keratoplasty (TPK).

CONCLUSION

Local immunosuppression and ocular surface disease play an important role in Candida keratitis. C. albicans appears to be more invasive compared with non-albicans spp.

Therapeutic effect of oxidized bletilla striata polysaccharide-natamycin eye drops on fungal keratitis

OBJECTIVE

Fungal keratitis (FK) usually develops to a poor clinical prognosis due to the fungal invasion and excessive inflammatory reaction. In order to enhance the therapeutic effect of natamycin (NAT), we used the anti-inflammatory biological polysaccharide bletilla striata polysaccharide (BSP) combined with NAT to prepare a new eye drop -- oxidized bletilla striata polysaccharide-natamycin (OBN).

METHODS

UV-vis, FT-IR, and fluorescence spectroscopy were used to identify the synthesis of OBN. Biocompatibility of OBN was determined by CCK-8, scratch assay, and corneal toxicity test. RAW264.7 cells and C57BL/6 mice were stimulated with A. fumigatus and treated with PBS, OBN, or NAT. The anti-inflammatory activity of OBN was detected by RT-PCR and ELISA. In mice with FK, the clinical scores were used to evaluate the effect of OBN; HE staining was performed to assess the corneal pathological changes; MPO assay and immunofluorescence staining were used to investigate neutrophil infiltration.

RESULTS

OBN was synthesized by combining oxidized bletilla striata polysaccharide (OBSP) with NAT through Schiff base reaction. OBN did not affect cell viability at a concentration of 160 μg/mL in HCECs, RAW264.7 cells, and mouse corneas. OBN versus NAT significantly improved the prognosis of A. fumigatus keratitis by reducing disease severity, neutrophil infiltration, and expression of inflammatory factors in vivo. Additionally, OBN treatment down-regulated the mRNA and protein expression levels of inflammatory factors IL-1β, TNF-α, and IL-6 in RAW264.7 and mouse models.

CONCLUSION

OBN is a compound prepared by covalently linking OBSP to the imino group of NAT through Schiff base reaction. OBN treatment down-regulated inflammation and improved the prognosis of mice with A. fumigatus keratitis.

Two-stage deep neural network for diagnosing fungal keratitis via in vivo confocal microscopy images

Timely and effective diagnosis of fungal keratitis (FK) is necessary for suitable treatment and avoiding irreversible vision loss for patients. In vivo confocal microscopy (IVCM) has been widely adopted to guide the FK diagnosis. We present a deep learning framework for diagnosing fungal keratitis using IVCM images to assist ophthalmologists. Inspired by the real diagnostic process, our method employs a two-stage deep architecture for diagnostic predictions based on both image-level and sequence-level information. To the best of our knowledge, we collected the largest dataset with 96,632 IVCM images in total with expert labeling to train and evaluate our method. The specificity and sensitivity of our method in diagnosing FK on the unseen test set achieved 96.65% and 97.57%, comparable or better than experienced ophthalmologists. The network can provide image-level, sequence-level and patient-level diagnostic suggestions to physicians. The results show great promise for assisting ophthalmologists in FK diagnosis.

Pseudonectria keratitis-emerging pathogenic fungi in the eye

BACKGROUND

Infectious keratitis, a significant contributor to blindness, with fungal keratitis accounting for nearly half of cases, poses a formidable diagnostic and therapeutic challenge due to its delayed clinical presentation, prolonged culture times, and the limited availability of effective antifungal medications. Furthermore, infections caused by rare fungal strains warrant equal attention in the management of this condition.

CASE PRESENTATION

A case of fungal keratitis was presented, where corneal scraping material culture yielded pink colonies. Lactophenol cotton blue staining revealed distinctive spore formation consistent with the Fusarium species. Further analysis using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) identified the causative agent as Fusarium proliferatum. However, definitive diagnosis of Pseudonectria foliicola infection was confirmed through ITS sequencing. The patient's recovery was achieved with a combination therapy of voriconazole eye drops and itraconazole systemic treatment.

CONCLUSION

Pseudonectria foliicola is a plant pathogenic bacterium that has never been reported in human infections before. Therefore, ophthalmologists should consider Pseudonectria foliicola as a possible cause of fungal keratitis, as early identification and timely treatment can help improve vision in most eyes.

Etiopathology, Epidemiology, Diagnosis, and Treatment of Fungal Keratitis

Fungal keratitis (FK) is a severe ocular condition resulting from corneal infection that is prevalent in tropical countries, particularly in developing regions of Asia and Africa. Factors like corneal lens misuse, inappropriate steroid use, and diagnostic challenges have provoked the epidemic. FK causes significant vision impairment, scarring, and ocular deformities. Accurate pathological diagnosis is crucial for effective therapeutic intervention. Topical antifungal therapy with surface healing medications proves effective in preventing fungal-borne ulcers. Managing FK requires a comprehensive understanding of fungal pathogenesis, guiding formulation strategies and preventive measures to curb global ocular blindness. This review provides in-depth insights into FK, covering etiology, epidemiology, pathogenesis, therapeutic interventions, antifungal resistance, limitations, prevention, and future perspectives on ocular surface disease management.

Recent Advances in the Use of Cubosomes as Drug Carriers with Special Emphasis on Topical Applications

Topical drug delivery employing drug nanocarriers has shown prominent results in treating topical ailments, especially those confined to the skin and eyes. Conventional topical formulations persist with drug and disease-related challenges during treatment. Various nanotechnology-driven approaches have been adopted to mitigate the issues associated with conventional formulations. Among these, cubosomes have shown potential applications owing to their liquid crystalline structure, which aids in bioadhesion, retention, sustained release, and loading hydrophilic and hydrophobic moieties. The phase transition behavior of glyceryl monooleate, the concentration of stabilizers, and critical packing parameters are crucial parameters that affect the formation of cubosomes. Microfluidics-based approaches constitute a recent advance in technologies for generating stable cubosomes. This review covers the recent topical applications of cubosomes for treating skin (psoriasis, skin cancer, cutaneous candidiasis, acne, and alopecia) and eye (fungal keratitis, glaucoma, conjunctivitis, and uveitis) diseases. The article summarizes the manufacturing and biological challenges (skin and ocular barriers) that must be considered and encountered for successful clinical outcomes. The patented products are successful examples of technological advancements within cosmeceuticals that support various topical applications with cubosomes in the pharmaceutical field.

Resveratrol has neuroprotective effects and plays an anti-inflammatory role through Dectin-1/p38 pathway in Aspergillus fumigatus keratitis

PURPOSE

To determine the antifungal, anti-inflammatory and neuroprotective effects of resveratrol (RES) in Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

Cytotoxicity assay and Draize eye assay were performed to assess the toxicity of RES. The antifungal effect of RES was assessed by minimal inhibitory concentration, scanning or transmission electron microscopy, propidium iodide uptake assay, and Calcofluor white staining. Phosphorylation of p38 MAPK, mRNA and protein levels of Dectin-1 and related inflammatory factors were measured by qRT-PCR, ELISA and Western blot in vitro and in vivo. Clinical score, HE staining, plate count, and myeloperoxidase test were used to observe the progress of fungal keratitis. IF staining, qRT-PCR, and the Von Frey test were selected to assess the neuroprotective effects of RES.

RESULTS

RES suppressed A. fumigatus hyphae growth and altered hyphae morphology in vitro. RES decreased the expression of Dectin-1, IL-1β and TNF-α, as well as p38 MAPK phosphorylation expression, and also decreased clinical scores, reduced inflammatory cell infiltration and neutrophil activity, and decreased fungal load. RES also protected corneal basal nerve fibers, down-regulated mechanosensitivity thresholds, and increased the mRNA levels of CGRP and TRPV-1..

CONCLUSION

These evidences revealed that RES could exert antifungal effects on A. fumigatus and ameliorate FK through suppressing the Dectin-1/p38 MAPK pathway to down-regulate IL-1β, IL-6, etc. expression and play protective effect on corneal nerves.

Cold atmospheric plasma inactivates Aspergillus flavus and Fusarium keratoplasticum biofilms and conidia in vitro

Introduction. Aspergillus flavus and Fusarium keratoplasticum are common causative pathogens of fungal keratitis (FK), a severe corneal disease associated with significant morbidity and vision loss. Escalating incidence of antifungal resistance to available antifungal drugs poses a major challenge to FK treatment. Cold atmospheric plasma (CAP) is a pioneering nonpharmacologic antimicrobial intervention that has demonstrated potential as a broad-spectrum antifungal treatment.Gap statement. Previous research highlights biofilm-associated resistance as a critical barrier to effective FK treatment. Although CAP has shown promise against various fungal infections, its efficacy against biofilm and conidial forms of FK pathogens remains inadequately explored.Aim. This study aims to investigate the antifungal efficacy of CAP against clinical fungal keratitis isolates of A. flavus and F. keratoplasticum in vitro.Methodology. Power parameters (22-27 kVpp, 300-400 Hz and 20-80 mA) of a dielectric barrier discharge CAP device were optimized for inactivation of A. flavus biofilms. Optimal applied voltage and total current were applied to F. keratoplasticum biofilms and conidial suspensions of A. flavus and F. keratoplasticum. The antifungal effect of CAP treatment was investigated by evaluating fungal viability through means of metabolic activity, c.f.u. enumeration (c.f.u. ml-1) and biofilm formation.Results. For both fungal species, CAP exhibited strong time-dependent inactivation, achieving greater than 80 % reduction in metabolic activity and c.f.u. ml-1 within 300 s or less, and complete inhibition after 600 s of treatment.Conclusion. Our findings indicate that CAP is a promising broad-spectrum antifungal intervention. CAP treatment effectively reduces fungal viability in both biofilm and conidial suspension cultures of A. flavus and F. keratoplasticum, suggesting its potential as an alternative treatment strategy for fungal keratitis.

Ebselen improves fungal keratitis through exerting anti-inflammation, anti-oxidative stress, and antifungal effects

Fungal keratitis is a severely vision-threatening corneal infection, where the prognosis depends on both fungal virulence and host immune defense. Inappropriate host responses can induce substantial inflammatory damage to the cornea. Therefore, in the treatment of fungal keratitis, it is important to concurrently regulate the immune response while efforts are made to eliminate the pathogen. Ebselen is a widely studied organo-selenium compound and has been demonstrated to have antifungal, antibacterial, anti-inflammatory, and oxidative stress-regulatory properties. The effectiveness of ebselen for the treatment of fungal keratitis remains unknown. In this study, ebselen was demonstrated to produce a marked inhibitory effect on Aspergillus fumigatus (A. fumigatus), including spore germination inhibition, mycelial growth reduction, and fungal biofilm disruption. The antifungal activity of ebselen was related to the cell membrane damage caused by thioredoxin (Trx) system inhibition-mediated oxidative stress. On the contrary, ebselen enhanced the antioxidation of Trx system in mammalian cells. Further, ebselen was proven to suppress the expressions of inflammatory mediators (IL-1β, IL-6, TNF-α, COX-2, iNOS, and CCL2) and reduce the production of oxidative stress-associated indicators (ROS, NO, and MDA) in fungi-stimulated RAW264.7 cells. In addition, ebselen regulated PI3K/Akt/Nrf2 and p38 MAPK signaling pathways, which contributed to the improvement of inflammation and oxidative stress. Finally, we verified the therapeutic effect of ebselen on mouse fungal keratitis. Ebselen improved the prognosis and reduced the fungal burden in mouse corneas. Expressions of inflammatory mediators, as well as the infiltration of macrophages and neutrophils in the cornea were also obviously decreased by ebselen. In summary, ebselen exerted therapeutic effects by reducing fungal load and protecting host tissues in fungal keratitis, making it a promising treatment for fungal infections.

Incorporation of Inclusion Complexes in the Dissolvable Microneedle Ocular Patch System for the Efficiency of Fluconazole in the Therapy of Fungal Keratitis

Fluconazole (FNL) is one of the first-line treatments for fungal keratitis as it is an effective broad-spectrum antimicrobial commonly administered orally or topically. However, FNL has a very low water solubility, limiting its drug formulation, therapeutic application, and bioavailability through tissues. To overcome these limitations, this study aimed to develop FNL inclusion complexes (FNL-IC) with cyclodextrin (α-cyclodextrin, sulfobutylether-β-cyclodextrin, and hydroxypropyl-γ cyclodextrin) and incorporate it into a dissolvable microneedle (DMN) system to improve solubility and drug penetration. FNL-IC was evaluated for saturation solubility, Fourier transform infrared spectroscopy, differential scanning calorimetry, in vitro release, minimum inhibitory concentration, minimum fungicidal concentration, and time-killing assay. DMN-FNL-IC was evaluated for mechanical and insertion properties, surface pH, moisture absorption ability, water vapor transmission, and drug content recovery. Moreover, ocular kinetic, ex vivo antimicrobial, in vivo antifungal, and chorioallantoic membrane (HET-CAM) assays were conducted to assess the overall performance of the formulation. Mechanical strength and insertion properties revealed that DMN-FNL-IC has great mechanical and insertion properties. The in vitro release of FNL-IC was significantly improved, exhibiting a 9-fold increase compared to pure FNL. The ex vivo antifungal activity showed significant inhibition of Candida albicans from 6.54 to 0.73 log cfu/mL or 100-0.94%. In vivo numbers of colonies of 0.87 ± 0.13 log cfu/mL (F2), 4.76 ± 0.26 log cfu/mL (FNL eye drops), 3.89 ± 0.24 log cfu/mL (FNL ointments), and 8.04 ± 0.58 log cfu/mL (control) showed the effectiveness of DMN preparations against other standard commercial preparations. The HET-CAM assay showed that DMN-FNL-IC (F2) did not show any vascular damage. Finally, a combination of FNL-IC and DMN was developed appropriately for ocular delivery of FNL, which was safe and increased the effectiveness of treatments for fungal keratitis.

Fangchinoline inhibits growth and biofilm of Candida albicans by inducing ROS overproduction

Infections caused by Candida species, especially Candida albicans, threaten the public health and create economic burden. Shortage of antifungals and emergence of drug resistance call for new antifungal therapies while natural products were attractive sources for developing new drugs. In our study, fangchinoline, a bis-benzylisoquinoline alkaloid from Chinese herb Stephania tetrandra S. Moore, exerted antifungal effects on planktonic growth of several Candida species including C. albicans, with MIC no more than 50 μg/mL. In addition, results from microscopic, MTT and XTT reduction assays showed that fangchinoline had inhibitory activities against the multiple virulence factors of C. albicans, such as adhesion, hyphal growth and biofilm formation. Furthermore, this compound could also suppress the metabolic activity of preformed C. albicans biofilms. PI staining, followed by confocal laser scanning microscope (CLSM) analysis showed that fangchinoline can elevate permeability of cell membrane. DCFH-DA staining suggested its anti-Candida mechanism also involved overproduction of intracellular ROS, which was further confirmed by N-acetyl-cysteine rescue tests. Moreover, fangchinoline showed synergy with three antifungal drugs (amphotericin B, fluconazole and caspofungin), further indicating its potential use in treating C. albicans infections. Therefore, these results indicated that fangchinoline could be a potential candidate for developing anti-Candida therapies.

Plumbagin inhibits fungal growth, HMGB1/LOX-1 pathway and inflammatory factors in A. fumigatus keratitis

To investigate the anti-inflammatory and antifungal effects of plumbagin (PL) in Aspergillus fumigatus (A. fumigatus) keratitis, the minimum inhibitory concentration (MIC), time-killing curve, spore adhesion, crystal violet staining, calcium fluoride white staining, and Propidium Iodide (PI) staining were employed to assess the antifungal activity of PL in vitro against A. fumigatus. The cytotoxicity of PL was assessed using the Cell Counting Kit-8 (CCK8). The impact of PL on the expression of HMGB1, LOX-1, TNF-α, IL-1β, IL-6, IL-10 and ROS in A. fumigatus keratitis was investigated using RT-PCR, ELISA, Western blot, and Reactive oxygen species (ROS) assay. The therapeutic efficacy of PL against A. fumigatus keratitis was assessed through clinical scoring, plate counting, Immunofluorescence and Hematoxylin-Eosin (HE) staining. Finally, we found that PL inhibited the growth, spore adhesion, and biofilm formation of A. fumigatus and disrupted the integrity of its cell membrane and cell wall. PL decreased IL-6, TNF-α, and IL-1β levels while increasing IL-10 expression in fungi-infected mice corneas and peritoneal macrophages. Additionally, PL significantly attenuated the HMGB1/LOX-1 pathway while reversing the promoting effect of Boxb (an HMGB1 agonist) on HMGB1/LOX-1. Moreover, PL decreased the level of ROS. In vivo, clinical scores, neutrophil recruitment, and fungal burden were all significantly reduced in infected corneas treated with PL. In summary, the inflammatory process can be inhibited by PL through the regulation of the HMGB-1/LOX-1 pathway. Simultaneously, PL can exert antifungal effects by limiting fungal spore adhesion and biofilm formation, as well as causing destruction of cell membranes and walls.

Extracellular vesicles from Candida albicans modulate immune cells function and play a protective role in fungal keratitis

Fungal keratitis (FK) is a highly blinding infectious corneal disease caused by pathogenic fungi. Candida albicans (C. albicans) is one of the main pathogens of fungal keratitis. Extracellular vesicles (EVs), lipid bilayer compartments released by almost all living cells, including fungi, have garnered attention for their role in pathogenic microbial infection and host immune responses in recent years. Studies have reported that pretreating the host with fungal EVs can reduce the inflammatory response of the host when attacked by fungi and reduce the lethality of fungal infection. However, there are no studies that have evaluated whether C. albicans EVs can modulate the inflammatory response associated with C. albicans keratitis. Our study revealed that C. albicans EVs could activate the polymorphonuclear cells (PMNs) and promote their secretion of proinflammatory cytokines and nitric oxide (NO), enhance their phagocytic and fungicidal abilities against C. albicans. C. albicans EVs also induced a proinflammatory response in RAW264.7 cells, which was characterized by increased production of inflammatory cytokines and elevated expression of the chemokine CCL2. Similarly, stimulation of C. albicans EVs to RAW264.7 cells also enhanced the phagocytosis and killing ability of cells against C. albicans. Besides, in our in vivo experiments, after receiving subconjunctival injection of C. albicans EVs, C57BL/6 mice were infected with C. albicans. The results demonstrated that pre-exposure to C. albicans EVs could effectively diminish the severity of keratitis, reduce fungal load and improve prognosis. Overall, we conclude that C. albicans EVs can modulate the function of immune cells and play a protective role in C. albicans keratitis.

Oxymatrine mitigates Aspergillus fumigatus keratitis by suppressing fungal activity and restricting pyroptosis

Fungal keratitis (FK) is a refractory keratitis caused by excessive inflammation and fungal damage. Excessive inflammation can lead to tissue damage and corneal opacity, resulting in a poor prognosis for FK. Oxymatrine (OMT) is a natural alkaloid, which has rich pharmacological effects, such as antioxidant and anti-inflammation. However, its antifungal activity and the mechanism of action in FK have not been elucidated. This study confirmed that OMT suppressed Aspergillus fumigatus growth, biofilm formation, the integrity of fungal cell and conidial adherence. OMT not only effectively reduced corneal fungal load but also inflammation responses. OMT lessened the recruitment of neutrophils and macrophages in FK. In addition, OMT up-regulated the expression of Nrf2 and down-regulated the expression of IL-18, IL-1β, caspase-1, NLRP3 and GSDMD. Pre-treatment with Nrf2 inhibitor up-regulated the expression of IL-1β, IL-18, caspase-1, NLRP3 and GSDMD supressed by OMT. In conclusion, OMT has efficient anti-inflammatory and antifungal effects by suppressing fungal activity and restricting pyroptosis via Nrf2 pathway. OMT is considered as a potential option for the treatment of FK.

Concurrent determination of anti-microbial and anti-inflammatory drugs in lachrymal fluid and tissue by LC-MS/MS: A potential treatment for microbial keratitis and its PK-PD evaluation

Unforeseen surfacing of microbial keratitis (MKT) over the years has led to a requisite for promising treatment strategy involving combination of antifungal and antibacterial agents. Subsequently, symptoms associated with MKT including inflammation and watery eyes require treatment with anti-inflammatory agents. Thus, a requirement of functional clinical treatment strategy involving combination of anti-inflammatory corticosteroids (Betamethasone) with antifungal polyene (Amphotericin B, AmB) and antibacterials macrolide (Azithromycin, AZT) and aminoglycoside (Neomycin, NEO). In the ensuing pursuit, a sensitive and fast simultaneous LC-MS/MS method of four drastically different analytes in rabbit tear fluid and cornea was developed and validated as per US-FDA guidelines. The gradient LC set-up was used with C18 column and flow rate of 0.55 mL/min along with short run time of 7 min. The calibration curves showed good linearity over the concentration range of 0.07-300 ng/mL, 1.00-400 ng/mL, 3.00-600 ng/mL and 8.00-900 ng/mL for AZT, AmB, NEO and BEM respectively. The bioanalytical method requires only 10 µL of ocular sample and analytes were extracted with fast protein precipitation with acidic methanol. Finally, the developed method was validated for selectivity, linearity (r2 > 0.99), precision, accuracy, matrix effects, and stability. PK-PD indices and dosing frequency was predicted using Phoenix WinNonlin Software, based on single dose ocular pharmacokinetics and MIC values of AmB, AZT and NEO. According to the PK-PD simulation, S. aureus and E. coli required 6 and 12 instillations of AZT per 24 h, respectively whereas 12 instillation of NEO requires per 24 h for S. aureus. The result suggests that to minimize antimicrobial resistance; drug, dose and dosing schedule depend upon the pathogen as well as the strain.

Trans-kingdom fungal pathogens infecting both plants and humans, and the problem of azole fungicide resistance

Azole antifungals are abundantly used in the environment and play an important role in managing fungal diseases in clinics. Due to the widespread use, azole resistance is an emerging global problem for all applications in several fungal species, including trans-kingdom pathogens, capable of infecting plants and humans. Azoles used in agriculture and clinics share the mode of action and facilitating cross-resistance development. The extensive use of azoles in the environment, e.g., for plant protection and wood preservation, contributes to the spread of resistant populations and challenges using these antifungals in medical treatments. The target of azoles is the cytochrome p450 lanosterol 14-α demethylase encoded by the CYP51 (called also as ERG11 in the case of yeasts) gene. Resistance mechanisms involve mainly the mutations in the coding region in the CYP51 gene, resulting in the inadequate binding of azoles to the encoded Cyp51 protein, or mutations in the promoter region causing overexpression of the protein. The World Health Organization (WHO) has issued the first fungal priority pathogens list (FPPL) to raise awareness of the risk of fungal infections and the increasingly rapid spread of antifungal resistance. Here, we review the main issues about the azole antifungal resistance of trans-kingdom pathogenic fungi with the ability to cause serious human infections and included in the WHO FPPL. Methods for the identification of these species and detection of resistance are summarized, highlighting the importance of these issues to apply the proper treatment.

Aspergillus fumigatus-Derived Extracellular Vesicles Mitigate Fungal Keratitis by Modulating the Immune Cell Function

Fungal keratitis (FK) is a refractory global disease characterized by a high incidence of blindness and a lack of effective therapeutic options, and Aspergillus fumigatus (A. fumigatus, AF) is one of the most common causative fungi. This study aimed to investigate the role of extracellular vesicles (EVs) from A. fumigatus in the immune cell function and their protective role in A. fumigatus keratitis in order to explore their therapeutic potential. First, we isolated and characterized the EVs (AF-derived EVs). In vitro, we stimulated RAW264.7 cells and polymorphonuclear cells with AF-derived EVs. The expression levels of inflammatory factors increased in both immune cells along with an M1 polarization variation of RAW264.7 cells. After being incubated with AF-derived EVs, both immune cells exhibited an increased conidia-phagocytic index and a decreased conidia survival rate. In vivo, we injected EVs subconjunctivally on mice resulting in a heightened production of secretory immunoglobulin A (sIgA) in tear fluid. By the injection of EVs on mice in advance, a significant reduction in severity of A. fumigatus FK was witnessed by lower clinical scores, inflammatory appearances, and mitigated fungal load. Collectively, these results positioned AF-derived EVs as a promising and innovative immune therapy for combating FK, while also providing a platform for further investigation into developing an optimal formulation for modulating inflammation in the context of FK.

Advances in the Application of Microneedles in the Treatment of Local Organ Diseases

In recent years, microneedles (MNs) have attracted a lot of attention due to their microscale sizes and high surface area (500-1000 µm in length), allowing pain-free and efficient drug delivery through the skin. In addition to the great success of MNs based transdermal drug delivery, especially for skin diseases, increasing studies have indicated the expansion of MNs to diverse nontransdermal applications, including the delivery of therapeutics for hair loss, ocular diseases, and oral mucosal. Here, the current treatment of hair loss, eye diseases, and oral disease is discussed and an overview of recent advances in the application of MNs is provided for these three noncutaneous localized organ diseases. Particular emphasis is laid on the future trend of MNs technology development and future challenges of expanding the generalizability of MNs.

Topical antifungal keratitis therapeutic potential of Clitoria ternatea Linn. flower extract: phytochemical profiling, in silico modelling, and in vitro biological activity assessment

Introduction

Fungal keratitis (FK) poses a severe threat to vision, potentially leading to blindness if not promptly addressed. Clitoria ternatea flower extracts have a history of use in Ayurvedic and Indian traditional medicines, particularly for treating eye ailments. This study investigates the antifungal and antibiofilm effects of Clitoria ternatea flower extracts on the FK clinical isolate Coniochaeta hoffmannii. Structural details and key compound identification were analysed through FTIR and GC-MS.

Methods

The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of Clitoria ternatea flower extracts were determined using broth dilution and well plate techniques. Biofilm inhibitory activity was assessed through microscopic evaluation, while anti-irritant and cytotoxic properties were evaluated using CAE-EI and MTT assays. Through GC-MS and FT-IR analysis the compounds dissolved in the extract and their functional group were studied, and their toxicity screening and pharmacokinetic prediction were conducted in silico. Subsequently, compounds with high corneal permeability were further identified, and molecular docking and simulation studies at 150 ns were used to investigate their interactions with fungal virulence factors and human inflammatory proteins.

Results and Discussion

At a concentration of 250 µg/mL, the Clitoria ternatea flower extract displayed effective biofilm inhibition. MIC and MFC values were determined as 500 and 1000 µg/mL, respectively. CAE-EI and MTT assays indicated no significant irritant and cytotoxic effects up to a concentration of 3 mg/mL. Compounds like 9,9-dimethoxybicyclo[3.3.1]nonane-2,4-dione showed high corneal permeability with strong and stable interactions with fungal virulence cellobiose dehydrogenase, endo β 1,4 xylanase, and glucanase, as well as corneal inflammation-associated human TNF-α and Interleukin IL-1b protein targets. The findings indicate that extracts from C. ternatea flowers could be formulated for an effective and safe alternative for developing new topical FK therapeutics.

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.

Recent advances in nanotechnology for the treatment of fungal keratitis

Fungal keratitis (FK) is a serious pathogenic disease usually associated with serious ocular complications. The current mainstay of treatment for FK is topical eye drops; however, poor corneal penetration, low bioavailability of the drug and the need to administer high and frequent doses due to the presence of an effective clearance mechanism in the eye result in poor patient compliance. Nanocarriers can extend the duration of drug action through sustained and controlled release of the drug, protect the drug from ocular enzymes and help overcome ocular barriers. In this review, we discussed the mechanisms of action of antifungal drugs, the theoretical basis for the treatment of FK, and recent advances in the clinical treatment of FK. We have summarized the results of research into the most promising nanocarriers for ocular drug delivery and highlight their efficacy and safety in the therapy.

Sustained Release of Voriconazole Using 3D-Crosslinked Hydrogel Rings and Rods for Use in Corneal Drug Delivery

Corneal disorders and diseases are prevalent in the field of clinical ophthalmology. Fungal keratitis, one of the major factors leading to visual impairment and blindness worldwide, presents significant challenges for traditional topical eye drop treatments. The objective of this study was to create biocompatible 3D-crosslinked hydrogels for drug delivery to the cornea, intending to enhance the bioavailability of ophthalmic drugs. Firstly, a series of flexible and porous hydrogels were synthesized (free-radical polymerization), characterized, and evaluated. The materials were prepared by the free-radical polymerization reaction of 1-vinyl-2-pyrrolidinone (also known as N-vinylpyrrolidone or NVP) and 1,6-hexanediol dimethacrylate (crosslinker) in the presence of polyethylene glycol 1000 (PEG-1000) as the porogen. After the physicochemical characterization of these materials, the chosen hydrogel demonstrated outstanding cytocompatibility in vitro. Subsequently, the selected porous hydrogels could be loaded with voriconazole, an antifungal medication. The procedure was adapted to realize a loading of 175 mg voriconazole per ring, which slightly exceeds the amount of voriconazole that is instilled into the eye via drop therapy (a single eye drop corresponds with approximately 100 mg voriconazole). The voriconazole-loaded rings exhibited a stable zero-order release pattern over the first two hours, which points to a significantly improved bioavailability of the drug. Ex vivo experiments using the established porcine eye model provided confirmation of a 10-fold increase in drug penetration into the cornea (after 2 h of application of the hydrogel ring, 35.8 ± 3.2% of the original dose is retrieved from the cornea, which compares with 3.9 ± 1% of the original dose in the case of eye drop therapy). These innovative hydrogel rods and rings show great potential for improving the bioavailability of ophthalmic drugs, which could potentially lead to reduced hospitalization durations and treatment expenses.

Quercetin protects against Aspergillus fumigatus keratitis by reducing fungal load and inhibiting TLR-4 induced inflammatory response

PURPOSE

To investigate the antifungal and anti-inflammatory effects of quercetin in Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

Draize eye test was performed in mice to evaluate the toxicity of quercetin, and the antifungal effects on A. fumigatus were assessed via scanning electron microscopy (SEM), propidium iodide uptake, and adherence assay. In fungal keratitis (FK) mouse models, immunostaining was performed for investigating toll-like receptor 4 (TLR-4) expression and macrophage infiltration. Real-time PCR, ELISA, and Western blot were used to evaluate the expression of pro-inflammatory factors IL-1β, TNF-α, and IL-6 in infected RAW264.7 cells. Cells were also treated with TLR-4 siRNA or agonist CRX-527 to investigate mechanisms underlying the anti-inflammatory activity of quercetin.

RESULTS

Quercetin at 32 μM was non-toxic to corneal epithelial and significantly inhibited A. fumigatus growth and adhesion, and also altered the structure and reduced the number of mycelia. Quercetin significantly reduced macrophage infiltration in the mouse cornea, and attenuated the expression of TLR-4 in the corneal epithelium and stroma of mice with keratitis caused by A. fumigatus. In RAW264.7 cells infected by A. fumigatus, quercetin downregulated TLR-4 along with pro-inflammatory factors IL-1β, TNF-α, and IL-6. RAW cells with TLR-4 knockdown had reduced expression of factors after A. fumigatus infection, which was decreased even further with quercetin treatment. In contrast, cells with CRX-527 had elevated inflammatory factors compared to control, which was significantly attenuated in the presence of quercetin.

CONCLUSION

Quercetin plays a protective role in mouse A. fumigatus keratitis by inhibiting fungal load, disrupting hyphae structure, macrophage infiltration, and suppressing inflammation response in macrophages via TLR-4 mediated signaling pathway.

The Role of Biofilms in Contact Lens Associated Fungal Keratitis

Biofilm formation is an important microbial strategy for fungal pathogens, such as Fusarium, Aspergillus, and Candida, to establish keratitis in patients wearing soft contact lenses. Despite the well-documented 2006 outbreak of Fusarium keratitis that eventually led to the withdrawal of the Bausch & Lomb multipurpose lens care solution ReNu with MoistureLoc ("MoistureLoc") from the global market, contact lens care systems and solutions currently available on the market do not specifically target fungal biofilms. This is partially due to the lack of recognition and understanding of important roles that fungal biofilms play in contact lens associated fungal keratitis (CLAFK). This review aims to reemphasize the link between fungal biofilms and CLAFK, and deepen our comprehension of its importance in pathogenesis and persistence of this medical device-related infection.

Recurrent Filamentous Fungal Keratitis Caused When the Primarily Selected Graft Diameter was Too Small

PURPOSE

To establish the importance of using a sufficiently large corneal graft in primary penetrating keratoplasty in order to prevent recurrence of fungal keratitis.

OBERSERVATIONS

A 58-year-old female patient underwent emergency penetrating keratoplasty (diameter 7.0 mm, double running suture) for therapy-resistant fungal keratitis (Fusarium solani) at an external eye clinic. Despite intensive antifungal therapy, new fungal infiltrates appeared in the host cornea after a few days. The patient was referred to our department for further treatment. On first presentation, circular infiltrates were seen around the corneal graft with anterior chamber involvement and therapy-resistant hypopyon. We performed an emergency penetrating repeat keratoplasty (diameter of 13.0 mm, 32 interrupted sutures) combined with anterior chamber lavage and intracameral and intrastromal drug injection.

CONCLUSION AND IMPORTANCE

Fungal keratitis sometimes has a frustrating clinical course. Therefore, early diagnosis with effective therapy initiation is of the utmost importance. In cases of penetrating keratoplasty, optimal planning and timing (before anterior chamber involvement) should be provided. Sufficient safety distance must be ensured in the choice of graft diameter, fixation with multiple interrupted sutures, and anterior chamber lavage, as well as intracameral and intrastromal drug administration. Incomplete excision carries a risk of recurrence and endophthalmitis in the course. Close postoperative control is necessary to detect early recurrences.

Clinical Characterization and Outcomes of Culture- and Polymerase Chain Reaction-Negative Cases of Infectious Keratitis

PURPOSE

To examine the clinical presentation, management, and outcomes of culture and polymerase chain reaction (PCR) negative cases of infectious keratitis.

METHODS

In this retrospective case series, we evaluated the laboratory and medical records of culture- and PCR-negative cases (2016-2020) reported to a tertiary care center, which were presumed to be infectious keratitis on the basis of clinical history and presentation.

RESULTS

A total of 121 cases with culture-negative keratitis were included in this study. The mean age of the patients was 48.42 ± 1.89 years, and 53.72% were female. At presentation, the presumed etiology was viral in 38.01%, bacterial in 27.27%, fungal in 8.26%, Acanthamoeba in 6.61%, and unlisted in 28.92% of cases. The most common risk factors were a previous history of ocular surface diseases (96.69%) and contact lens use (37.19%). In total, 61.98% of the patients were already on antimicrobial medication at presentation. The initial management was altered in 79 cases (65.29%) during the treatment course. Average presenting and final (post-treatment) visual acuities (VA) were 0.98 ± 0.04 (LogMAR) and 0.42 ± 0.03 (LogMAR), respectively. A significantly higher frequency of patients with a final VA worse than 20/40 (Snellen) had worse VA at initial presentation (p < 0.0001). A history of ocular surface disease, cold sores, and recurrent infection (p < 0.05) were more commonly associated with a presumed diagnosis of viral keratitis. The patients with presumed bacterial etiology were younger and had a history of poor contact lens hygiene (p < 0.05).

CONCLUSIONS

We observed a distinct difference in clinical features among patients with culture-negative and PCR-negative keratitis managed for presumed viral and bacterial infections. Although there was significant variability in presentation and management duration in this cohort, the visual outcomes were generally favorable.

Simultaneous estimation of voriconazole, moxifloxacin, and pirfenidone in rabbit lacrimal matrix using LC-MS/MS: an application to preclinical ocular pharmacokinetics

Dynamic emergence of microbial keratitis (MK) requires a promising therapeutic arsenal of antifungal and antibacterial agents like voriconazole (VCZ) and moxifloxacin (MOXI), respectively. Parallelly, another paradigm of MK associated with ulcerative wounds cannot be left unnoticed and requires antifibrotic remedy (pirfenidone, PIR) as an authalic antimicrobial to retain the primordial vision. For designing an effective clinical cure, a combination of these three agents is required at a therapeutic dosage regimen. Following the quest, we have developed a simple and sensitive LC-MS/MS bioanalytical method for simultaneous quantification of VCZ, MOXI, and PIR in rabbit lacrimal fluid. The method was validated as per US-FDA norms using ketoconazole as an internal standard for linearity, accuracy-precision, matrix effect, dilution integrity, selectivity, and stability. The five minutes chromatographic set-up includes isocratic elution with a C18 column using MeOH (80%, v/v) and ultrapure water containing 0.2% formic acid (20%, v/v), respectively. The MS-based analyte detection was achieved in ESI⁺ multiple reaction monitoring mode. The sample extraction was performed using the protein precipitation method with minimal sample size. The validated methodology was employed to determine the ocular pharmacokinetics profile of marketed formulations containing VCZ, MOXI, and PIR in rabbit lacrimal matrix.

Candidalysin amplifies the immune inflammatory response in Candida albicans keratitis through the TREM-1/DAP12 pathway

Candidalysin is a fungal peptide toxin secreted by Candida albicans hyphae during invasion into epithelial cells. In Candida albicans-infected mucosa, candidalysin causes epithelial cell damage and activates downstream inflammatory responses, especially the release of inflammatory cytokines. However, the role of candidalysin in Candida albicans corneal keratitis remains unexplored. Moreover, it remains unclear whether candidalysin regulates the inflammatory response through the TREM-1/DAP12 pathway in Candida albicans corneal keratitis. In this study, we determined the expression pattern of TREM-1 in a mouse model of Candida albicans corneal keratitis and investigated the molecular mechanism underlying the inflammatory response regulation by candidalysin. The corneal keratitis model was established in C57BL/6 mice. In the GF9 group, mice were pretreated and then treated with the TREM-1 inhibitor GF9; in the candidalysin group, mice were treated with peptide candidalysin; and in the PD98059 group, mice were pretreated with the ERK inhibitor PD98059. Slit-lamp photography, clinical scoring, PCR, western blotting and immunofluorescence assay were performed to observe disease response and GF9 therapeutic efficacy. Pretreatment with candidalysin or PD98059 was performed before Candida albicans infection. GF9 treatment reduced the expression of TREM-1 and cytokines in the infected mouse cornea, whereas candidalysin treatment increased the expression of TREM-1, p-ERK, and cytokines, and this increase was inhibited by GF9. The candidalysin-induced increment of TREM-1, p-ERK, and cytokines was inhibited by PD98059 pretreatment. These data suggest that candidalysin can initiate inflammatory response in Candida albicans corneal keratitis through the TREM-1/DAP12 pathway and can regulate cytokine expression by enhancing ERK phosphorylation.

Caspofungin-Loaded Formulations for Treating Ocular Infections Caused by Candida spp

Fungal keratitis causes corneal blindness worldwide. The treatment includes antibiotics, with Natamycin being the most commonly used; however, fungal keratitis is difficult to treat, so alternative therapies are needed. In situ gelling formulations are a promising alternative; this type of formulation has the advantages of eye drops combined with the advantages of ointments. This study was designed to develop and characterize three formulations containing 0.5% CSP: CSP-O1, CSP-O2, and CSP-O3. CSP is an antifungal drug that acts against a diverse variety of fungi, and Poloxamer 407 (P407) is a polymer of synthetic origin that is able to produce biocompatible, biodegradable, highly permeable gels and is known to be thermoreversible. Short-term stability showed that formulations are best stored at 4 °C, and rheological analysis showed that the only formulation able to gel in situ was CSP-O3. In vitro release studies indicated that CSP-O1 releases CSP most rapidly, while in vitro permeation studies showed that CSP-O3 permeated the most. The ocular tolerance study showed that none of the formulations caused eye irritation. However, CSP-O1 decreased the cornea's transparency. Histological results indicate that the formulations are suitable for use, with the exception of CSP-O3, which induced slight structural changes in the scleral structure. All formulations were shown to have antifungal activity. In view of the results obtained, these formulations could be promising candidates for use in the treatment of fungal keratitis.

Modern Technologies in Diagnosis of Fungal Keratitis (Review)

Traumas and infectious diseases of the eye play a leading role in the development of corneal blindness responsible for 1.5-2 million cases of vision loss per year. To date, the issue of reducing the incidence of fungal keratitis is acute and needs to be solved worldwide. Trauma as a risk factor for corneal fungal disease is thought to be prevalent in developing countries due to agricultural involvement, while in developed countries the onset of the disease is predisposed by medical advances such as contact vision correction and modern ophthalmic surgery. Thorough analysis of the pathogenesis gives the possibility to describe the action of fungal enzymes, biofilm formation, and the resistance mechanism, which on the one hand explains the aggressive course of the disease and difficulties in its diagnosis, and on the other hand, it encourages searching for new methods of diagnosis and treatment. The non-specific clinical picture of fungal keratitis, the variety and availability of antibiotics nowadays become an obstacle for rapid detection of this pathology. Low public awareness and late visit to an ophthalmologist are also a barrier to successful combating the increasing incidence of fungal keratitis. Belated diagnosis, increasing resistance of fungi to antibiotics, and lack of registered antifungal ophthalmic drugs justify poor treatment efficacy resulting in decreased visual acuity or vision loss. Existing diagnostic methods need systematization and detailed comparison, identifying the advantages and disadvantages of each. This review considers causative agents and their influence on pathogenesis of the disease, describes difficulties of fungal keratitis diagnosis and possible ways of overcoming these problems using new developments, and also outlines further prospects of research in this direction.

Time-Course Transcriptomic Analysis Reveals the Crucial Roles of PANoptosis in Fungal Keratitis

Purpose

Fungal keratitis (FK) is a serious corneal infection with high morbidity. Host immune responses function as a double-edged sword by eradicating fungal pathogens while also causing corneal damage, dictating the severity, progression, and outcome of FK. However, the underlying immunopathogenesis remains elusive.

Methods

Time-course transcriptome was performed to illustrate the dynamic immune landscape in a mouse model of FK. Integrated bioinformatic analyses included identification of differentially expressed genes, time series clustering, Gene Ontology enrichment, and inference of infiltrating immune cells. Gene expression was verified by quantitative polymerase chain reaction (qPCR), Western blot, or immunohistochemistry.

Results

FK mice exhibited dynamic immune responses with concerted trends with clinical score, transcriptional alteration, and immune cell infiltration score peaking at 3 days post infection (dpi). Disrupted substrate metabolism, broad immune activation, and corneal wound healing occurred sequentially in early, middle, and late stages of FK. Meanwhile, dynamics of infiltrating innate and adaptive immune cells displayed distinct characteristics. Proportions of dendritic cells showed overall decreasing trend with fungal infection, whereas that of macrophages, monocytes, and neutrophils rose sharply in early stage and then gradually decreased as inflammation resolved. Activation of adaptive immune cells was also observed in late stage of infection. Furthermore, shared immune responses and activation of AIM2-, pyrin-, and ZBP1-mediated PANoptosis were revealed across different time points.

Conclusions

Our study profiles the dynamic immune landscape and highlights the crucial roles of PANoptosis in FK pathogenesis. These findings provide novel insights into host responses to fungi and contribute to the development of PANoptosis-targeted therapeutics for patients with FK.

Characteristics of In Vitro Culture and In Vivo Confocal Microscopy in Patients with Fungal Keratitis in a Tertiary Referral Hospital in Central China

PURPOSE

To investigate the characteristics of in vitro culture and in vivo confocal microscopy (IVCM) in patients with fungal keratitis (FK) presented in a tertiary referral hospital in central China.

METHODS

In this noncomparative retrospective study, patients with the diagnosis of FK between October 2021 and November 2022 were reviewed. An IVCM and fungal culture (corneal scraping specimens) were performed, and the characteristics were analyzed.

RESULTS

During October 2021 and November 2022, 85 patients were diagnosed with FK. From 63 culture-positive cases, 8 species of fungus were identified. The proportions of isolated fungal species were Fusarium and Aspergillus equally accounting for 33.3% (21 of 63), Alternaria 9.5% (6 of 63), Curvularia 6.3% (4 of 63), Scedosporium apiospermum 6.3% (4 of 63), Paecilomyces lilacinus 3.2% (2 of 63), Exserohilum 3.2% (2 of 63), and Candida 4.8% (3 of 63), respectively. In positive culture cases, IVCM was found to be positive for hyphae or spores in 61 of 63 patients (96.8%). Different fungal species had a variety of cultural characteristics and IVCM manifestations.

CONCLUSIONS

In a tertiary referral hospital in central China, Fusarium species, Aspergillus species, and Alternaria species were the 3 most common isolated fungal pathogens, and the proportion of Aspergillus species was significantly higher than that in other regions of China. Careful lesion depth examination by IVCM and OCT should be taken before lamellar keratoplasty to avoid postoperative recurrence. Identifying the IVCM image and culture characteristics will facilitate rapid diagnosis and proper treatment, but IVCM cannot yet replace fungal cultures to distinguish between different fungal species.

Thymol Ameliorates Aspergillus fumigatus Keratitis by Downregulating the TLR4/ MyD88/ NF-kB/ IL-1β Signal Expression and Reducing Necroptosis and Pyroptosis

Fungal keratitis is a refractory kind of keratopathy. We attempted to investigate the anti-inflammatory role of thymol on Aspergillus fumigatus (A. fumigatus) keratitis. Wound healing and fluorescein staining of the cornea were applied to verify thymol's safety. Mice models of A. fumigatus keratitis underwent subconjunctival injection of thymol. The anti-inflammatory roles of thymol were verified by hematoxylin-eosin (HE) staining, slit lamp observation, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blotting. In contrast with the DMSO group, more transparent corneas and less inflammatory cells infiltration were detected in mice treated with 50 μg/ml thymol. Thymol downregulated the synthesis of TLR4, MyD88, NF-kB, IL-1β, NLRP3, caspase 1, caspase 8, GSDMD, RIPK3 and MLKL. In summary, we proved that thymol played a protective part in A. fumigatus keratitis by cutting down inflammatory cells aggregation, downregulating the TLR4/ MyD88/ NF-kB/ IL-1β signal expression and reducing necroptosis and pyroptosis.

Development and multi-center validation of machine learning model for early detection of fungal keratitis

BACKGROUND

Fungal keratitis (FK) is a leading cause of corneal blindness in developing countries due to poor clinical recognition and laboratory identification. Here, we aimed to identify the distinct clinical signature of FK and develop a diagnostic model to differentiate FK from other types of infectious keratitis.

METHODS

We reviewed the electronic health records (EHRs) of all patients with suspected infectious keratitis in Beijing Tongren Hospital from January 2011 to December 2021. Twelve clinical signs of slit-lamp images were assessed by Lasso regression analysis and collinear variables were excluded. Three models based on binary logistic regression, random forest classification, and decision tree classification were trained for FK diagnosis and employed for internal validation. Independent external validation of the models was performed in a cohort of 420 patients from seven different ophthalmic centers to evaluate the accuracy, specificity, and sensitivity in real world.

FINDINGS

Three diagnostic models of FK based on binary logistic regression, random forest classification, and decision tree classification were established and internal validation were achieved with the mean AUC of 0.916, 0.920, and 0.859, respectively. The models were well-calibrated by external validation using a prospective cohort including 210 FK and 210 non-FK patients from seven eye centers across China. The diagnostic model with the binary logistic regression algorithm classified the external validation dataset with a sensitivity of 0.907 (0.774, 1.000), specificity 0.899 (0.750, 1.000), accuracy 0.905 (0.805, 1.000), and AUC 0.903 (0.808, 0.998).

INTERPRETATION

Our model enables rapid identification of FK, which will help ophthalmologists to establish a preliminary diagnosis and to improve the diagnostic accuracy in clinic.

FUNDING

The Open Research Fund from the National Key Research and Development Program of China (2021YFC2301000) and the Open Research Fund from Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Beijing Tongren Hospital, Beihang University &Capital Medical University (BHTR-KFJJ-202001) supported this study.

Overcoming the Stromal Barrier of the Cornea with a Peptide Conjugate Nano-Assembly to Combat Fungal Keratitis

Fungal hyphae deeply invade the cornea in fungal keratitis. The corneal stroma hinders the infiltration of antifungal drugs and reduces their bioavailability. Here, this work reports a peptide conjugate nano-assembly that permeates the stroma and kills the pathogen without irritating the ocular cornea. The hydrophilic surface of the nano-assembly ensures deep permeation into the stroma. When encountering a fungal hyphal cell, the nano-assembly disassembles and exposes the α-helical peptide to destroy the fungal membrane, thus inactivating the pathogen. In a rabbit model of fungal keratitis, the nano-assembly exhibits a better therapeutic effect than commercially available natamycin ophthalmic suspension. Peptide conjugates with a nano-assembled structure and assembly-disassembly behavior could serve as the foundation of a new therapy for fungal keratitis.

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.

Innate Immune System Activation, Inflammation and Corneal Wound Healing

Corneal wounds resulting from injury, surgeries, or other intrusions not only cause pain, but also can predispose an individual to infection. While some inflammation may be beneficial to protect against microbial infection of wounds, the inflammatory process, if excessive, may delay corneal wound healing. An examination of the literature on the effect of inflammation on corneal wound healing suggests that manipulations that result in reductions in severe or chronic inflammation lead to better outcomes in terms of corneal clarity, thickness, and healing. However, some acute inflammation is necessary to allow efficient bacterial and fungal clearance and prevent corneal infection. This inflammation can be triggered by microbial components that activate the innate immune system through toll-like receptor (TLR) pathways. In particular, TLR2 and TLR4 activation leads to pro-inflammatory nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) activation. Similarly, endogenous molecules released from disrupted cells, known as damage-associated molecular patterns (DAMPs), can also activate TLR2, TLR4 and NFκB, with the resultant inflammation worsening the outcome of corneal wound healing. In sterile keratitis without infection, inflammation can occur though TLRs to impact corneal wound healing and reduce corneal transparency. This review demonstrates the need for acute inflammation to prevent pathogenic infiltration, while supporting the idea that a reduction in chronic and/or excessive inflammation will allow for improved wound healing.

Immune modulating nanoparticles for the treatment of ocular diseases

Ocular diseases are increasingly influencing people’s quality of life. Complicated inflammatory mechanisms involved in the pathogenic process of ocular diseases make inflammation-targeting treatment a potential therapeutic approach. The limited efficacy of conventional anti-inflammatory therapeutic strategies, caused by various objective factors, such as complex ocular biological barriers, and subjective factors, such as poor compliance, are promoting the development of new therapeutic methods. With the advantages of considerable tissue permeability, a controllable drug release rate, and selective tissue targeting ability, nanoparticles have successfully captured researchers’ attention and have become a research hotspot in treating ocular diseases. This review will focus on the advantages of nanosystems over traditional therapy, the anti-inflammation mechanisms of nanoparticles, and the anti-inflammatory applications of nanoparticles in different ocular diseases (ocular surface diseases, vitreoretinopathy, uveal diseases, glaucoma, and visual pathway diseases). Furthermore, by analyzing the current situation of nanotherapy and the challenges encountered, we hope to inspire new ideas and incentives for designing nanoparticles more consistent with human physiological characteristics to make progress based on conventional treatments. Overall, some progress has been made in nanoparticles for the treatment of ocular diseases, and nanoparticles have rather broad future clinical translation prospects.

Clinical Comparison of Fusarium Keratitis according to the Initial Potassium Hydroxide (KOH) Smear: A Retrospective Study in South Korea

Purpose. This study aimed to compare predisposing factors, clinical characteristics, treatment, and prognosis of Fusarium keratitis according to the result of the initial potassium hydroxide (KOH) smear. Methods. This is a retrospective study of cases with Fusarium keratitis between January 2000 and December 2019 at two tertiary hospitals in South Korea. Patients were divided into two groups depending on the KOH smear result (KOH-positive and KOH-negative group), and its clinical factors were analyzed. Results. Among 319 fungal keratitis, seventy-nine cases were identified with Fusarium keratitis. Forty-seven cases (59.5%) were negative in the initial KOH smear prior to their diagnosis. The most common predisposing factor for Fusarium keratitis was ocular trauma (55.7%). There were no significant differences in sex, occupation, ulcer size or shape, hypopyon, and initial visual acuity between the two groups. Differences were observed between the KOH-positive group and the KOH-negative group in terms of deep corneal infiltration (50.0% vs. 78.7%, $p=0.008$ ) and evisceration treatment (3.1% vs. 25.5%, $p=0.008$ ). The delayed time to initiate antifungal eye drops was longer in the KOH-negative group (1.13 ± 0.49 vs. 3.93 ± 4.89, $p=0.002$ ). Only the KOH-negative group combined bacterial infection. The significant risk factors for poor clinical outcomes were the central corneal lesion (odds ratio (OR) 3.50, $p=0.047$ ), a large ulcer size (size ≥ 7.5 mm2) (OR 4.98, $p=0.009$ ), and endothelial plaque (OR 7.00, $p=0.031$ ). Conclusion. Initial KOH-negative patients often needed evisceration and had worse final visual outcomes. The delay of prompt initiation of antifungal treatment and combined bacterial infection result in a poor prognosis. This study highlights the initial KOH effect on early diagnosis and early treatment of Fusarium keratitis.

Flavopiridol Protects against Fungal Keratitis due to Aspergillus fumigatus by Alleviating Inflammation through the Promotion of Autophagy

Fungal keratitis is a serious infectious keratopathy related to fungal virulence and excessive inflammatory responses. Autophagy exhibits a potent ability to resolve inflammation during fungal infection. This study aimed to investigate the protective function of flavopiridol in Aspergillus fumigatus keratitis and explore its effects on autophagy. In our study, the corneas of the fungal keratitis mouse model were treated with 5 μM flavopiridol. In vitro, RAW 264.7 cells were pretreated with 200 nM flavopiridol before fungal stimulation. A. fumigatus was incubated with flavopiridol, and the antifungal activity of flavopiridol was detected. Our results indicated that flavopiridol treatment notably reduced clinical scores as well as cytokines expression of infected corneas. In infected RAW 264.7 cells, flavopiridol treatment inhibited IL-1β, IL-6, and TNF-α expression but promoted IL-10 expression. Transmission electron microscopy (TEM) images showed that more autolysosomes were present in infected corneas and RAW 264.7 cells after flavopiridol treatment. Flavopiridol treatment notably upregulated the protein expression of LC3, Beclin-1, and Atg-7. 3-Methyladenine (3-MA, an inhibitor of autophagy) pretreatment counteracted the cytokine regulation induced by flavopiridol. Moreover, flavopiridol promoted the phagocytosis of RAW 264.7 cells. Flavopiridol also exhibited antifungal activity by restricting fungal growth and limiting fungal biofilm formation and conidial adhesion. In conclusion, flavopiridol significantly alleviated the inflammation of fungal keratitis by activating autophagy. In addition, flavopiridol promoted the phagocytosis of RAW 264.7 cells and exhibited antifungal function, indicating the potential therapeutic role of flavopiridol in fungal keratitis.

Clinical Observation of Corneal Endothelial Plaques With Fungal and Bacterial Keratitis by Anterior Segment Optical Coherence Tomography and In Vivo Confocal Microscopy

PURPOSE

Endothelial plaque is an important sign of fungal keratitis and is related to diagnosis, surgical indications, and prognosis. However, bacterial keratitis sometimes involves fibrin formation on the back corneal surface, similar to endothelial plaques. Because corneal infiltration interferes with precise observation of the posterior corneal plaque, distinguishing pathogens with a slitlamp is difficult. We hope to assist clinicians in early diagnosis and timely treatment by observing the connection state of endothelial plaques and the corneal endothelium through anterior segment optical coherence tomography (AS-OCT) and the different forms of endothelial plaques in infectious keratopathy through in vivo confocal microscopy (IVCM).

METHODS

We analyzed 52 patients in the Eye Hospital of the First Affiliated Hospital of Harbin Medical University who were clearly diagnosed with fungal or bacterial keratitis with endothelial plaques. All patients underwent AS-OCT and IVCM on admission.

RESULTS

According to the smear, IVCM, or fungal and bacterial culture results, the patients were diagnosed with fungal (28 patients) or bacterial keratitis (24 patients). AS-OCT in 25 patients diagnosed with fungal keratitis revealed that the corneal endothelium-endothelial plaque boundary was unclear and wavy, and 24 patients had unclear cell boundaries and a large number of compactly distributed inflammatory cells in the endothelial layer according to IVCM. AS-OCT in 23 patients diagnosed with bacterial keratitis revealed clear corneal endothelium-endothelial plaque boundaries, and insufficient endothelial cell boundaries with a large number of visible and scattered inflammatory cell structures were observed through IVCM in 22 patients.

CONCLUSIONS

Corneal endothelial plaque detection by AS-OCT and IVCM can be used for early diagnosis of infectious keratitis.

Roles of pattern recognition receptors in response to fungal keratitis

Fungal keratitis is one of the leading causes of blindness worldwide, which has become an increasingly serious threat to public ocular health, but no effective treatment strategies are available now. Pattern recognition receptors (PRRs) of the innate immune system are the first line of host defense against fungal infections. They could recognize pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) and trigger an array of inflammatory responses. Over the last decades, research has resulted in significant progress regarding the roles of PRRs in fungal keratitis. This review will highlight the importance of several pattern recognition receptors (C-type lectin-like receptors, Toll-like receptors, and NOD-like receptors) in regulating the innate immunity under fungal keratitis and describe the crosstalk and collaboration in PRRs contributing to disease pathology. Meanwhile, some potential therapy-based PRRs against corneal fungal infections are discussed.

Laccase-mediated functionalization of natamycin by gallic acids for the therapeutic effect on Aspergillus fumigatus keratitis

To improve the therapeutic effect of natamycin on fungal keratitis (FK), the grafted derivatives of natamycin and gallic acid were obtained, and the effects of the grafted derivatives on Aspergillus fumigatus (A. fumigatus) keratitis were investigated. The structure of natamycin grafted with gallic acid was identified by FT-IR and UV-Vis, and the successful synthesis of Gallic-Natamycin (GA-NAT) was proved. CCK-8 and the Draize eye test showed that GA-NAT had less cytotoxicity. Then, through in vitro antibacterial experiments such as minimum inhibitory concentration (MIC), adhesion, biofilm formation, and calcium fluorescence staining and in vivo experiments such as clinical score and plate counting, the results showed that GA-NAT had similar antifungal activity to natamycin, but had a better therapeutic effect than natamycin. Myeloperoxidase assay and immunofluorescence staining also showed that GA-NAT significantly inhibited neutrophil recruitment and activity. Moreover, It was further found that GA-NAT could inhibit the mRNA and protein expressions of LOX-1, TNF-α, and IL-1β. These results indicated that GA-NAT inhibited the fungal growth, reduced the neutrophil infiltration into cornea, and down-regulated the expression of inflammatory factors in lesions, which provides a new choice for FK treatment.

Thymol Protects against Aspergillus Fumigatus Keratitis by Inhibiting the LOX-1/IL-1β Signaling Pathway

OBJECTIVE

To explore the anti-inflammatory effects and mechanisms of action of thymol in Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

The minimum inhibitory concentration of thymol against A. fumigatus was detected. To characterize the anti-inflammatory effects of thymol, mouse corneas and human corneal epithelial cells were pretreated with thymol or dimethyl sulfoxide (DMSO) before infection with A. fumigatus spores. Slit-lamp microscopy, immunohistochemistry, myeloperoxidase detection, quantitative real-time polymerase chain reaction, and Western blotting were used to assess infection. Neutrophil and macrophage recruitment, in addition to the secretion of LOX-1 and IL-1β, were quantified to evaluate the relative contribution of thymol to the inflammatory response.

RESULTS

We confirmed that the growth of A. fumigatus was directly inhibited by thymol. In contrast with the DMSO group, there was a lower degree of inflammation in the mouse corneas of the thymol-pretreated group. This was characterized by significantly lower clinical scores, less inflammatory cell infiltration, and lower expression of LOX-1 and IL-1β. Similarly, in vitro experiments indicated that the production of LOX-1 and IL-1β was significantly inhibited after thymol treatment, in contrast with the DMSO-pretreated group.

CONCLUSION

Our findings demonstrate that thymol exerted a direct fungistatic activity on A. fumigatus. Furthermore, thymol played a protective role in fungal keratitis by inhibiting LOX-1/IL-1β signaling pathway and reducing the recruitment of neutrophils and macrophages.

Ocular Surface Infection Mediated Molecular Stress Responses: A Review

Infection mediated ocular surface stress responses are activated as early defense mechanisms in response to host cell damage. Integrated stress responses initiate the host response to different types of infections and modulate the transcription of key genes and translation of proteins. The crosstalk between host and pathogen results in profound alterations in cellular and molecular homeostasis triggering specific stress responses in the infected tissues. The amplitude and variations of such responses are partly responsible for the disease severity and clinical sequelae. Understanding the etiology and pathogenesis of ocular infections is important for early diagnosis and effective treatment. This review considers the molecular status of infection mediated ocular surface stress responses which may shed light on the importance of the host stress-signaling pathways. In this review, we collated literature on the molecular studies of all ocular surface infections and summarize the results from such studies systematically. Identification of important mediators involved in the crosstalk between the stress response and activation of diverse signaling molecules in host ocular surface infection may provide novel molecular targets for maintaining the cellular homeostasis during infection. These targets can be then explored and validated for diagnostic and therapeutic purposes.