Filamentous fungal infections of the cornea: a global overview of epidemiology and drug sensitivity

The differential virulence of Fusarium strains causing corneal infections and plant diseases is associated with accessory chromosome composition

Fusarium oxysporum is a cross-kingdom pathogen. While some strains cause disseminated fusariosis and blinding corneal infections in humans, others are responsible for devastating vascular wilt diseases in plants. To better understand the distinct adaptations of F. oxysporum to animal or plant hosts, we conducted a comparative phenotypic and genetic analysis of two strains: MRL8996 (isolated from a keratitis patient) and Fol4287 (isolated from a wilted tomato [Solanum lycopersicum]). In vivo infection of mouse corneas and tomato plants revealed that, while both strains cause symptoms in both hosts, MRL8996 caused more severe corneal ulceration and perforation in mice, whereas Fol4287 induced more pronounced wilting symptoms in tomato. In vitro assays using abiotic stress treatments revealed that the human pathogen MRL8996 was better adapted to elevated temperatures, whereas the plant pathogen Fol4287 was more tolerant of osmotic and cell wall stresses. Both strains displayed broad resistance to antifungal treatment, with MRL8996 exhibiting the paradoxical effect of increased tolerance to higher concentrations of the antifungal caspofungin. We identified a set of accessory chromosomes (ACs) and protein-encoding genes with distinct transposon profiles and functions, respectively, between MRL8996 and Fol4287. Interestingly, ACs from both genomes also encode proteins with shared functions, such as chromatin remodeling and post-translational protein modifications. Our phenotypic assays and comparative genomics analyses lay the foundation for future studies correlating genotype with phenotype and for developing targeted antifungals for agricultural and clinical uses.

Trends and Clinical Outcomes of Fungal Keratitis in Canada: A 20-year Retrospective Multicentre Study

PURPOSE

An increase in fungal and particularly filamentous keratitis has been observed in many geographic areas, mostly in contact lens wearers. This study seeks to characterize long-term trends in fungal keratitis in a continental climate area to provide guidance for diagnosis and treatment.

DESIGN

Retrospective multicentric case series.

METHODS

Cases of microbiology-confirmed fungal keratitis from 2003 to 2022 presenting to tertiary care centers across Canada were included. Charts were reviewed for patient demographics, risk factors, visual acuity, and treatments undertaken.

RESULTS

A total of 138 patients were identified: 75 had yeast keratitis while 63 had filamentous keratitis. Patients with yeast keratitis had more ocular surface disease (79% vs 28%) while patients with filamentous keratitis wore more refractive contact lenses (78% vs 19%). Candida species accounted for 96% of all yeast identified, while Aspergillus (32%) and Fusarium (26%) were the most common filamentous fungi species. The mean duration of treatment was 81 ± 96 days. Patients with yeast keratitis did not have significantly improved visual acuity with medical treatment (1.8 ± 1 LogMAR to 1.9 ± 1.5 LogMAR, P = .9980), in contrast to patients with filamentous keratitis (1.4 ± 1.2 LogMAR to 1.1 ± 1.3 LogMAR, P = .0093).

CONCLUSIONS

Fungal keratitis is increasing in incidence, with contact lenses emerging as one of the leading risk factors. Significant differences in the risk factors and visual outcomes exist between yeast keratitis and filamentous keratitis which may guide diagnosis and treatment.

Screening Candida auris through a multiplex stepwise PCR algorithm directly from clinical samples of patients suspected of otomycosis in south of Iran; Detection of five cases

BACKGROUND

Otomycosis is an infection of the external auditory canal caused by molds and yeasts with descending frequency. Laboratory diagnosis is usually confirmed by microscopy and culture. However, they are not specific enough to reliably differentiate the causative agents, especially for rare pathogens such as Candida auris. The purpose of the current study was to the molecular screening of C. auris species from direct clinical samples of patients with suspected otomycosis in Southern of Iran.

MATERIALS AND METHODS

A total of 221 ear aspirates collected from 221 patients with suspected otomycosis over a four-year period. All the ear aspirations were examined with pan-fungal primers, then those with a positive result was included in two separate reaction mixtures simultaneously to identify the most clinically relevant Aspergillus and Candida species. The validity of positive samples for C. auris was assessed by sequencing.

RESULTS

Of the 189 pan-fungal positive PCRs, 78 and 39 specimens contained Aspergillus spp. and Candida spp., respectively. Furthermore, 65 specimens showed simultaneous positive bands in both Candida and Aspergillus species-specific multiplex PCR including five samples/patients with positive result for C. auris (5/189; 2.6%). Four out of five cases with C. auris species-specific PCR were reconfirmed by sequencing, while none were positive for C. auris in culture.

CONCLUSION

Unfortunately, due to high treatment failure rates of antifungal classes against C. auris species, rapid and accurate identification of patients colonised with C. auris is critical to overcome the challenge of preventing transmission. This PCR assay can be successfully applied for rapid and accurate detection of C. auris directly in patient samples and is able to differentiate C. auris from closely related Candida species.

An in-vitro evaluation of antifungal, anti-lungcancer (A549), and anti-hyperglycemic activities potential of Andrographis paniculata (Burm. f.) flower extract

The medical plant research has received more attention among researchers especially after the Covid-19 pandemic. This research performed to evaluate the antifungal, anti-lung cancer (A549), and anti-hyperglycemic activities of aqueous extract of Andrographis paniculata flower. Interestingly, A. paniculata flower aqueous extract contains pharmaceutically valuable phytochemicals such as alkaloid, phenolics, terpenoids, tannins, flavonoids, and protein. It also showed fine antifungal activity against test fungal pathogens in the following order as: Aspergillus niger > Fusarium solani > Trichoderma harzianum > A. parasiticus > P. expansum > Penicillium janthinellum with lowest MIC values as ranged from 100 to 300 μg mL-1. Interestingly, this aqueous extract also showed considerable anti-lung cancer activity, evidenced by dose and time dependent lung cancer cell line (A549) growth/proliferation inhibition/cytotoxicity activity (65%) at 300 μg mL-1 concentration. This can be achieved by plant extract through inducing the secretion of apoptosis related proteins such as TNF α, IFN-γ, and ınterleukin 2 leads to apoptosis in A549 cells. It also showed fine anti-diabetic activity by inhibiting α -amylase (58.41%) than α-glucosidase (54.74%) at 200 μg mL-1 concentration. The UV as well as FTIR results demonstrated that the aqueous extract of A. paniculata flower contains pharmaceutically valuable bioactive compounds, which may be responsible for the wide range of biomedical applications.

A Structure-Aware Convolutional Neural Network for Automatic Diagnosis of Fungal Keratitis with In Vivo Confocal Microscopy Images

Fungal keratitis (FK) is a common and severe corneal disease, which is widely spread in tropical and subtropical areas. Early diagnosis and treatment are vital for patients, with confocal microscopy cornea imaging being one of the most effective methods for the diagnosis of FK. However, most cases are currently diagnosed by the subjective judgment of ophthalmologists, which is time-consuming and heavily depends on the experience of the ophthalmologists. In this paper, we introduce a novel structure-aware automatic diagnosis algorithm based on deep convolutional neural networks for the accurate diagnosis of FK. Specifically, a two-stream convolutional network is deployed, combining GoogLeNet and VGGNet, which are two commonly used networks in computer vision architectures. The main stream is used for feature extraction of the input image, while the auxiliary stream is used for feature discrimination and enhancement of the hyphae structure. Then, the features are combined by concatenating the channel dimension to obtain the final output, i.e., normal or abnormal. The results showed that the proposed method achieved accuracy, sensitivity, and specificity of 97.73%, 97.02%, and 98.54%, respectively. These results suggest that the proposed neural network could be a promising computer-aided FK diagnosis solution.

Immunity to pathogenic fungi in the eye

Fusarium, Aspergillus and Candida are important fungal pathogens that cause visual impairment and blindness in the USA and worldwide. This review will summarize the epidemiology and clinical features of corneal infections and discuss the immune and inflammatory responses that play an important role in clinical disease. In addition, we describe fungal virulence factors that are required for survival in infected corneas, and the activities of neutrophils in fungal killing, tissue damage and cytokine production.

Honokiol reduces fungal burden and ameliorate inflammation lesions of Aspergillus fumigatus keratitis via Dectin-2 down-regulation

PURPOSE

To screen and identify the mechanism of honokiol on anti-fungi and anti-inflammation in fungal keratitis (FK) through bioinformatic analysis and biological experiments.

METHODS

Transcriptome profile demonstrated differential expression genes (DEGs) of Aspergillus fumigatus keratitis between PBS-treated and honokiol-treated groups via bioinformatics analyses. Inflammatory substances were quantified by qRT-PCR, Western blot and ELISA, and macrophage polarization was examined by flow cytometry. Periodic acid Schiff staining and morphological interference assay were used to detect hyphal distribution in vivo and fungal germination in vitro, respectively. Electron microscopy was to illustrate hyphal microstructure.

RESULTS

Illumina sequencing demonstrated that compared with the honokiol group, 1175 up-regulated and 383 down-regulated genes were induced in C57BL/6 mice Aspergillus fumigatus keratitis with PBS treatment. Through GO analysis, some differential expression proteins (DEPs) played major roles in biological processes, especially fungal defense and immune activation. KEGG analysis provided fungus-related signaling pathways. PPI analysis demonstrated that DEPs from multiple pathways form a close-knit network, providing a broader context for FK treatment. In biological experiments, Dectin-2, NLRP3 and IL-1β were upregulated by Aspergillus fumigatus to evaluate immune response. Honokiol could reverse the trend, comparable to Dectin-2 siRNA interference. Meanwhile, honokiol could also play an anti-inflammatory role via promoting M2 phenotype polarization. Moreover, honokiol reduced hyphal distribution in the stroma, delayed germination, and destroyed the hyphal cell membrane in-vitro.

CONCLUSIONS

Honokiol possesses anti-fungal and anti-inflammatory effects in Aspergillus fumigatus keratitis and may develop a potential and safe therapeutic modality for FK.

Conservation and Expansion of Transcriptional Factor Repertoire in the Fusarium oxysporum Species Complex

The Fusarium oxysporum species complex (FOSC) includes both plant and human pathogens that cause devastating plant vascular wilt diseases and threaten public health. Each F. oxysporum genome comprises core chromosomes (CCs) for housekeeping functions and accessory chromosomes (ACs) that contribute to host-specific adaptation. This study inspects global transcription factor profiles (TFomes) and their potential roles in coordinating CC and AC functions to accomplish host-specific interactions. Remarkably, we found a clear positive correlation between the sizes of TFomes and the proteomes of an organism. With the acquisition of ACs, the FOSC TFomes were larger than the other fungal genomes included in this study. Among a total of 48 classified TF families, 14 families involved in transcription/translation regulations and cell cycle controls were highly conserved. Among the 30 FOSC expanded families, Zn2-C6 and Znf_C2H2 were most significantly expanded to 671 and 167 genes per family including well-characterized homologs of Ftf1 (Zn2-C6) and PacC (Znf_C2H2) that are involved in host-specific interactions. Manual curation of characterized TFs increased the TFome repertoires by 3% including a disordered protein Ren1. RNA-Seq revealed a steady pattern of expression for conserved TF families and specific activation for AC TFs. Functional characterization of these TFs could enhance our understanding of transcriptional regulation involved in FOSC cross-kingdom interactions, disentangle species-specific adaptation, and identify targets to combat diverse diseases caused by this group of fungal pathogens.

Conservation and Expansion of Transcriptional Factor Repertoire in the Fusarium oxysporum Species Complex

The Fusarium oxysporum species complex (FOSC) includes both plant and human pathogens that cause devastating plant vascular wilt diseases and threaten public health. Each F. oxysporum genome comprises core chromosomes (CCs) for housekeeping functions and accessory chromosomes (ACs) that contribute to host-specific adaptation. This study inspected global transcription factor profiles (TFomes) and their potential roles in coordinating CCs and ACs functions to accomplish host-specific pathogenicity. Remarkably, we found a clear positive correlation between the sizes of TFome and proteome of an organism, and FOSC TFomes are larger due to the acquisition of ACs. Among a total of 48 classified TF families, 14 families involved in transcription/translation regulations and cell cycle controls are highly conserved. Among 30 FOSC expanded families, Zn2-C6 and Znf_C2H2 are most significantly expanded to 671 and 167 genes per family, including well-characterized homologs of Ftf1 (Zn2-C6) and PacC (Znf_C2H2) involved in host-specific interactions. Manual curation of characterized TFs increased the TFome repertoires by 3%, including a disordered protein Ren1. Expression profiles revealed a steady expression of conserved TF families and specific activation of AC TFs. Functional characterization of these TFs could enhance our understanding of transcriptional regulation involved in FOSC cross-kingdom interactions, disentangle species-specific adaptation, and identify targets to combat diverse diseases caused by this group of fungal pathogens.

Fungal keratitis in Iran: Risk factors, clinical features, and mycological profile

Introduction

This study was intended to investigate the clinical features and predisposing factors of fungal keratitis (FK), as well as molecular identification and antifungal susceptibility of causative agents in Tehran, Iran.

Methods

This cross-sectional study was carried out from April 2019 to May 2021. All fungi isolates were identified using conventional methods and were confirmed by DNA-PCR-based molecular assays. Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) was used to identify yeast species. Minimum inhibitory concentrations (MIC) of eight antifungal agents were assessed according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) microbroth dilution reference method.

Results

Fungal etiology was confirmed in 86 (7.23%) of 1189 corneal ulcers. A significant predisposing factor for FK was ocular trauma caused by plant materials. Therapeutic penetrating keratoplasty (PKP) was required in 60.4% of cases. The predominant fungal species isolated was Fusarium spp. (39.5%) followed by Aspergillus spp. (32.5%) and Candida spp. (16.2%).

Discussion

The MIC results indicate that amphotericin B may be appropriate for treating FK caused by Fusarium species. FK caused by Candida spp. can be treated with flucytosine, voriconazole, posaconazole, miconazole, and caspofungin. In developing countries such as Iran, corneal infection due to filamentous fungi is a common cause of corneal damage. In this region, fungal keratitis is observed primarily within the context of agricultural activity and subsequent ocular trauma. Fungal keratitis can be managed better with understanding the "local" etiologies and antifungal susceptibility patterns.

An artificial intelligence approach to classify pathogenic fungal genera of fungal keratitis using corneal confocal microscopy images

PURPOSE

Fungal keratitis is a common cause of blindness worldwide. Timely identification of the causative fungal genera is essential for clinical management. In vivo confocal microscopy (IVCM) provides useful information on pathogenic genera. This study attempted to apply deep learning (DL) to establish an automated method to identify pathogenic fungal genera using IVCM images.

METHODS

Deep learning networks were trained, validated, and tested using a data set of 3364 IVCM images that collected from 100 eyes of 100 patients with culture-proven filamentous fungal keratitis. Two transfer learning approaches were investigated: one was a combined framework that extracted features by a DL network and adopted decision tree (DT) as a classifier; another was a complete supervised DL model which used DL-based fully connected layers to implement the classification.

RESULTS

The DL classifier model revealed better performance compared with the DT classifier model in an independent testing set. The DL classifier model showed an area under the receiver operating characteristic curves (AUC) of 0.887 with an accuracy of 0.817, sensitivity of 0.791, specificity of 0.831, G-mean of 0.811, and F1 score of 0.749 in identifying Fusarium, and achieved an AUC of 0.827 with an accuracy of 0.757, sensitivity of 0.756, specificity of 0.759, G-mean of 0.757, and F1 score of 0.716 in identifying Aspergillus.

CONCLUSION

The DL model can classify Fusarium and Aspergillus by learning effective features in IVCM images automatically. The automated IVCM image analysis suggests a noninvasive identification of Fusarium and Aspergillus with clear potential application in early diagnosis and management of fungal keratitis.

Evaluation of antifungal susceptibility and clinical characteristics in fungal keratitis in a tertiary care center in North India

Purpose

To study the antifungal susceptibility of common corneal pathogenic fungi to antifungal agents in the North Indian population.

Methods

Prospective study of the antifungal sensitivity testing (natamycin, amphotericin B, voriconazole, itraconazole, fluconazole, posaconazole, caspofungin, micafungin) of fungal isolates from 50 cases of culture positive fungal keratitis by using E test method. Details noted included demographic data, visual acuity, clinical details, grade of keratitis, healing time, and success in medical management.

Results

Of 50 patients with fungal keratitis (mean age: 40.28 ± 16.77 years), 12 eyes healed within 3 weeks, 14 had a delayed healing response, and 24 had chronic keratitis. Among the 15 cases of Fusarium isolates, 93.3% were sensitive to natamycin, while 40% to amphotericin B; 66.6% to voriconazole, 13.4% to itraconazole and fluconazole each. 80% of Fusarium cases (n = 12) showed susceptibility to posaconazole. Among Aspergillus flavus isolates, 53.4% (n = 8) were sensitive to natamycin, with only 40% (n = 7) showing sensitivity to amphotericin B and good susceptibility to azoles. MIC against susceptible Fusarium spp. for natamycin was 3-16 μg/mL, amphotericin B: 1-8 μg/mL, voriconazole: 0.5-1.5 μg/mL, itraconazole: 0.5-12 μg/mL, posaconazole: 0.094-1.5 μg/mL. MIC against Aspergillus flavus was natamycin: 8-32 μg/mL, amphotericin B: 0.5-16 μg/mL, voriconazole: 0.025-4 μg/mL, itraconazole: 0.125-8 μg/mL, posaconazole: 0.047-0.25 μg/mL; against Aspergillus niger isolates, to natamycin was 6 μg/mL (n=1), amphotericin B 8-12 μg/mL (n = 3), voriconazole: 0.125-0.19 μg/mL (n = 3), itraconazole: 0.38-0.75 μg/mL, posaconazole: 0.064-0.19 μg/mL and against Aspergillus fumigatus (n = 1), was natamycin4 μg/mL, amphotericin B - 8 μg/mL, voriconazole 0.25 μg/mL, itraconazole 1 μg/mL, and posaconazole 0.19 μg/mL. MIC against susceptible Acremonium spp. for natamycin was 1.5-16 μg/mL, amphotericin B: 0.5-8 μg/mL, voriconazole: 0.19-3 μg/mL, itraconazole: 0.125 μg/mL, posaconazole: 0.125-0.5 μg/mL and against susceptible Curvularia was natamycin 0.75-4 μg/mL, amphotericin B 0.5-1 μg/mL, voriconazole 0.125-0.19 μg/mL, itraconazole 0.047-0.094 μg/mL, posaconazole 0.047-0.094 μg/mL. MIC against Mucor spp.+ Rhizopus spp. (n = 1) was natamycin: 8 μg/mL, amphotericin B: 0.75 μg/mL, posaconazole: 1.5 μg/mL. MIC against of Alternaria (n = 1) was voriconazole: 0.19 μg/mL, posaconazole: 0.094 μg/mL. MIC against Penicillium (n=1) was natamycin: 8 μg/mL, voriconazole: 0.25 μg/mL, itraconazole: 0.5 μg/mL, and Posaconazole: 0.125 μg/mL.

Conclusion

Our observations highlight the variations in susceptibility to antifungal agents. Posaconazole seems to be effective with low MIC against common corneal pathogenic fungal isolates.

Molecular identification, phylogeny and antifungal susceptibilities of dematiaceous fungi isolated from human keratomycosis

PURPOSE

To investigate the dematiaceous fungal profile of patients with ocular mycoses attending a tertiary eye care hospital in Coimbatore, India METHODS: The identification of dematiaceous fungus based on their morphology, their genotypes, and the measurement of the minimum inhibitory concentrations (MICs) using microdilution method of routinely used antifungal drugs were all compared.

RESULTS

A total of 148 dematiaceous fungi were isolated during a study period of 27 months. Isolates were confirmed as Curvularia spp. (n = 98), Exserohilum spp. (n = 32), Alternaria spp. (n = 14), Exophiala spp. (n = 2), Cladosporium sp. (n = 1) and Aureobasidium sp. (n = 1). Out of 50 well grown isolates characterized genotypically based on the amplification and sequencing of the ITS region of the ribosomal RNA gene cluster and subsequent BLAST analysis, Curvularia lunata (n = 24), C. aeria (n = 1), C. spicifera (n = 8), C. hawaiiensis (n = 1), C. maydis (n = 2), C. papendorfii (n = 2), C. geniculata (n = 3), C. tetramera (n = 2) and Exs. rostratum (n = 7) were identified. In vitro antifungal susceptibilities of the most tested dematiaceous isolates showed that voriconazole had a MIC₅₀ of 0.25 μg ml^-1, while amphotericin B had a MIC₅₀ of 0.25 μg ml^-1 for Curvularia spp. and Alternaria spp.

CONCLUSION

Voriconazole proved to be the most effective drug against the pigmented filamentous fungi, followed by amphotericin B, itraconazole and econazole.

Ophthalmic Solutions with a Broad Antiviral Action: Evaluation of Their Potential against Ocular Herpetic Infections

HSV-1 can be associated with severe and recurrent eye infections characterized by a strong inflammatory response that leads to blepharoconjunctivitis, epithelial and stromal keratitis, and retinal necrosis. The incidence of HSV-1 keratitis is 1.5 million every year worldwide, including more than 40,000 new cases exhibiting serious visual failures. Generally, the therapy uses antiviral drugs to promote healing; however, there are currently no compounds that are able to completely eradicate the virus. In addition, the phenomenon of resistance is rapidly spreading among HSV-1 strains, creating mutants developing resistance to the common antiviral drugs; therefore, deep research on this issue is warranted. The efficacy of different ophthalmic solutions already on the market was evaluated for reducing HSV-1 infection. Different plaque assays were set up on epithelial cells, revealing that two ophthalmic solutions were able to inhibit viral replication in the early stages of infection. The data were further confirmed by molecular tests analyzing the expression levels of the principal genes involved in HSV-1 infection, and a strong reduction was observed after only 1 min of eye-drop treatment. Collectively, these results suggested the use of ophthalmic solutions as potential antiviral options for the treatment of ocular herpetic infection.

Clinical Manifestation of Infectious Keratitis in Ocular Graft Versus Host Disease

Purpose: We evaluated the clinical manifestations of, and risk factors for, infectious keratitis in patients with ocular graft-versus-host disease (GVHD).Methods: A total of 11 patients who developed infectious keratitis after a diagnosis of ocular GVHD between January 2015 and December 2020, and 36 who did not (the control group), were included in this retrospective study. We recorded sex, age, any underlying disease, any other organ affected by systemic GVHD, systemic immunosuppressant use, follow-up duration, clinical manifestations, the severity of ocular GVHD prior to infection, the size of the epithelial defect, the depth of infiltration, hypopyon status, and the results of microbiological tests. Systemic and ocular indices (including systemic GVHD status) were compared using the chi-squared test. Risk factors for infection were identified.Results: Of the corneal indices, the presence of corneal filaments, the extent of corneal neovascularization, and the number of corneal epithelial defects were significantly higher in the infected group (p = 0.023, p = 0.004, and p = 0.001, respectively). GVHD severity was also significantly higher in that group (p < 0.001). The presence of corneal filaments, corneal neovascularization, and corneal epithelial defects prior to infection correlated significantly with the risk of infection (p = 0.046, p = 0.010, and p = 0.003, respectively). Multivariate analysis identified corneal epithelial defects as a significant risk factor for infection (p = 0.029).Conclusions: In patients with ocular GVHD, corneal epithelial defects, corneal neovascularization, and corneal filaments prior to infection were associated with the development of infection. In particular, corneal epithelial defects before infection was a significant risk factor for infection.

Microbiological Profiles of Ocular Fungal Infection at an Ophthalmic Referral Hospital in Southern China: A Ten-Year Retrospective Study

Purpose

Methods

Results

Conclusion

Case Report: A Rare Fungal Keratitis Caused by Plectosphaerella Cucumerina

PURPOSE

To report a rare case of fungal keratitis caused by Plectosphaerella cucumerina.

METHODS

This study retrospectively reviewed the medical records of a case of fungal keratitis.

RESULTS

Silt-lamp biomicroscopy revealed corneal infiltration and epithelial defects. Anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM) were performed to assist in the diagnosis and evaluate corneal conditions. The isolate was identified as Plectosphaerella cucumerina by MALDI-TOF mass spectrometry. The patient was treated with topical 5% pimaricin and oral voriconazole for 1 month and recovered.

CONCLUSION

Fungal keratitis caused by Plectosphaerella cucumerina is rare. AS-OCT and IVCM can help locate the lesion and diagnose fungal keratitis. Furthermore, MALDI-TOF mass spectrometry showed potential prospects in the identification of filamentous fungi. Plectosphaerella cucumerina rarely infects humans and is sensitive to antifungal agents such as pimaricin and voriconazole.

Update on fungal keratitis in France: a case-control study

PURPOSE

To report an epidemiological update of documented fungal keratitis (FK) in a French tertiary ophthalmological centre from 2014 to 2018 in comparison with a previous period from 1993 to 2008.

METHODS

Sixty-two consecutive FK documented by microbiological corneal scrapings were compared with the 64 FK of the previous study. Amphotericin B and voriconazole eye drops were administered hourly. Population characteristics, clinical findings, aetiological organisms and treatments were analysed.

RESULTS

The most frequently identified fungi were Fusarium (61%), Aspergillus (6.5%) and Candida (5%). Thirty out of 44 cases examined with in vivo confocal microscopy (IVCM) presented filaments. Ten required conventional cross-linking, 9 therapeutic penetrating keratoplasty, and 2 enucleation. Risk factors significantly associated with the absence of response to medical treatment were patient age (p = 0.01), presence of a deep stromal infiltrate at presentation (p = 0.04) and high numbers of filaments in IVCM images (p = 0.01). The two populations were comparable in age, but not in sex ratio males/females (18/44 versus 37/26 in the previous study; p = 0.001). The frequency of contact lens-associated infection increased from 35.5% to 71% (p = 0.0001) between the two periods. Since then, filamentous FK increased from 69% (44/64) to 95% (59/62) (p = 0.0001). A history of keratoplasty was less frequently reported during the last period (3.2% (2/62) versus 17% (11/64) of cases (p = 0.01)). A clear decrease in the frequency of therapeutic keratoplasty was noted from 39% (25/64) to 14% (9/62) (p = 0.02).

CONCLUSION

The frequency of filamentous keratomycosis is currently increasing. Elderly patients and the presence of numerous filaments in IVCM are associated with poor clinical outcomes.

Post penetrating keratoplasty infectious keratitis: Clinico-microbiological profile and predictors of outcome

PURPOSE

To study the clinico-microbiological profile, outcomes and prognostic factors of post penetrating keratoplasty (PKP) infectious keratitis.

METHODS

Retrospective review of medical records of 78 patients with post PKP infectious keratitis presenting between January 2014 and December 2018. Demographic, clinical and microbiological profile was documented and predictors of treatment and graft success were evaluated using univariate and subsequent multivariate logistic regression analysis.

RESULTS

Mean age of patients was 52.17 ± 15.51 years and mean infiltrate size was 19.39 ± 19.68 mm². Mean duration of presentation with infection post PKP was 11.66 ± 10.65 months. Culture positivity was seen in 64 eyes (82.05%). Bacterial growth was observed in 47 eyes (60.25%), fungal growth in 17 (21.79%) and no microbiological growth in 14 eyes (17.94%). At 3 months the visual acuity (VA) improved in 37 eyes (47.44%), did not change in 27 (34.62%) and deteriorated in 14 (17.95%). Graft failure was noted in 53 eyes (73.08%). Surgical intervention was needed in 47 (60.25%) eyes of which most common was therapeutic PKP in 32 eyes (41.02%). Treatment failure was noted with fungal infection (p = 0.05), poorer vision at presentation (p = 0.02), larger infiltrate area (p = 0.002) and graft infection developing before 1 year (p = 0.02). Graft failure was noted with associated endophthalmitis (p = 0.02), poorer VA at presentation (p = 0.01) and larger infiltrate area (p = 0.02).

CONCLUSION

Post PKP infectious keratitis is a sight threatening ocular condition. It is associated with high incidence of graft failure and frequently requires surgical intervention. Fungal etiology, larger infiltrate size, poorer vision at presentation and associated endophthalmitis carries a poorer prognosis.

α- MSH plays anti-inflammatory and anti-fungal role in Aspergillus Fumigatus keratitis

PURPOSE

To investigate the anti-inflammatory and anti-fungal role of α-melanocyte stimulating hormone (α-MSH) in Aspergillus Fumigatus (A. fumigatus) keratitis.

METHOD

Corneas of C57BL/6 mice were infected with A. Fumigatus. α-MSH (5 ul, 1x10^-4mmol/ml) was given by subconjunctival injection from day 1 to day 3 post infection (p.i.). After 3 days p.i., clinical score was recored and HE staining was tested. Fungal load in mice corneas was observed by plate counting. Pro-inflammatory mediators and pattern recognition receptors (PRRs) were detected. The numbers of neutrophils and macrophages were tested by immunofluorescence staining. The role of α-MSH in RAW264.7 cells after A. fumigatus stimulation were evaluated by PCR and Western blot, and MPKA protein levels including total-JNK (T-JNK), phosphorylated-JNK (P-JNK), total-ERK (T-ERK) and phosphorylated-ERK (P-ERK) were tested via Western blot with or without α-MSH treatment.

RESULTS

Compared with PBS control group, α-MSH treatment alleviated disease response and decreased clinical score at 3 days p.i. HE staining showed less infiltration in corneal tissue after α-MSH treatment. Plate counting experiment showed that number of viable fungus in corneas of α-MSH treated group was less than control group. mRNA levels of IL-1β, TNF-α, IL-6, MIP-2, LOX-1, Dectin-1 and iNOS were decreased. Protein levels of IL-1β, TNF-α, IL-6 and Dectin-1 were decreased. α-MSH treatment also decreased the infiltrating neutrophils and macrophages. The levels of pro-inflammatory cytokines, Dectin-1 and LOX-1 stimulated by A. fumigatus, were also suppressed by pretreatment of α-MSH in RAW264.7 cells. The ratio of P-JNK/T-JNK and P-ERK/T-ERK were down regulated in α-MSH group compared with PBS control group.

CONCLUSION

α-MSH alleviates the severity and decreases fungal load of A. fumigatus keratitis in mice. Migration of neutrophils and macrophages are restrained. α-MSH downregulates the expression of dectin-1 and the ratio of P-JNK/T-JNK and P-ERK/T-ERK in A. fumigatus infection.

Fungal keratitis caused by Pseudallescheria boydii: clinical and mycological characteristics

Background

Pseudallescheria keratitis is rare but important type of fungal keratitis because of the inherently resistance of the organism to many existing antifungal agents.

Methods

Slit-lamp and confocal microscopy were used for clinical examinations. Fungal isolates were identified based on morphological characteristics and DNA sequence of the internal transcribed spacer region (ITS). In vitro antifungal susceptibility testing for fungal isolates was performed according to the Clinical and Laboratory Standards Institute (CLSI, M38-A2).

Result

All patients had a history of ocular trauma. In clinical examination hypopion were seen in three patients. The main antifungal medications were topical voriconazole. After treatment the visual acuity of all patients improved in 2–3 weeks.

Conclusion

All four patients of Pseudallescheria keratitis had similar clinical features. Accurate and rapid identification of species should be helpful in treating p. boydii keratitis.

Endothelial Biopsy for the Diagnosis and Management of Culture-Negative Retrocorneal Fungal Keratitis With the Assistance of Optical Coherence Tomography Imaging

PURPOSE

To report a case of a culture-negative deep fungal corneal infection that was diagnosed after histopathology of an anterior segment optical coherence tomography-guided endothelial biopsy.

METHODS

A 22-year-old woman with history of contact lens wear and concomitant topical steroid use presented with a mid-stromal corneal infiltrate that failed to respond to oral acyclovir and topical fortified antibiotics. Although cornea stains, cultures, and confocal microscopy showed negative results, there was high clinical suspicion for fungal keratitis. After 2 months on topical natamycin, oral voriconazole, and serial intrastromal and intracameral voriconazole injections, the infiltrate enlarged and deepened. Imaging with anterior segment optical coherence tomography revealed that the infection had progressed to an endothelial plaque.

RESULTS

Diagnostic endothelial biopsy was performed in the operating room. Cultures showed again negative results, whereas histopathology of the removed specimen revealed fungal elements. The postoperative edema at the site of the biopsy resolved over the course of 4 weeks, and a posterior stromal scar formed. Serial intrastromal and intracameral voriconazole injections were continued for the first postoperative month. At the 1-year and the 3-year follow-up examinations, the patient's vision was 20/20 without recurrence.

CONCLUSIONS

Intraoperative scraping of the endothelial plaque and histopathologic evaluation of the specimen proved to be of utmost importance for definitive diagnosis and resolution of the culture-negative deep fungal infection in this case. This young patient's cornea was retained and vision remains excellent.

Distribution, Prevalence, and Causative Agents of Fungal Keratitis: A Systematic Review and Meta-Analysis (1990 to 2020)

Objectives

This study aims to provide an overview of the prevalence, distribution, and causative agents of fungal keratitis.

Methods

All the articles with data on the prevalence of fungal keratitis among various patient groups from January 1, 1990 to May 27, 2020 were retrieved through a systematic search in PubMed, Scopus, Web of Science, and Google Scholar. Data were extracted, and the pooled estimated prevalence of fungal keratitis, yeast/mold infection, the spectrum and frequency of various causative agents, and the pooled estimated prevalence of mixed infections were calculated in general and in various countries (wherever possible) using meta-analysis.

Results

From 11,235 articles retrieved in the primary search step, 169 met the inclusion criteria. The 169 eligible articles were divided into six groups and analyzed separately. The pooled prevalence of fungal keratitis was variable with values ranging from 0.05% among postkeratoplasty patients to 43.01% among patients with a clinical suspicion of fungal keratitis. There was also a country-dependent variation in the prevalence (Paraguay: 50.1% (95% CI, 35.11, 65.00); Ireland: 1.1% (95% CI, 0.03, 6.04)). Except for postkeratoplasty cases (yeast: 51.80%), in all patient groups, molds were more common than yeasts. Although more than 50 distinct species of fungi have been found to cause fungal keratitis, Fusarium species followed by Aspergillus species were the most common causes of the disease. In general, 9.29% (95% CI, 6.52, 12.38) of fungal keratitis cases were mixed with bacterial agents.

Conclusion

The prevalence of fungal keratitis can vary dramatically depending on the patient groups and geographical origin; however, the dominant causative agents are generally similar.

Fungal keratitis: Mechanisms of infection and management strategies

Fungal corneal ulcers are an uncommon, yet challenging, cause of vision loss. In the United States, geographic location appears to dictate not only the incidence of fungal ulcers, but also the fungal genera most encountered. These patterns of infection can be linked to environmental factors and individual characteristics of fungal organisms. Successful management of fungal ulcers is dependent on an early diagnosis. New diagnostic modalities like confocal microscopy and polymerase chain reaction are being increasingly used to detect and identify infectious organisms. Several novel therapies, including crosslinking and light therapy, are currently being tested as alternatives to conventional antifungal medications. We explore the biology of Candida, Fusarium, and Aspergillus, the three most common genera of fungi causing corneal ulcers in the United States and discuss current treatment regimens for the management of fungal keratitis.

First Report of a Case of Ocular Infection Caused by Purpureocillium lilacinum in Poland

This report describes the first case of an ocular infection induced by Purpureocillium lilacinum in Poland. The patient was a 51-year-old immunocompetent contact lens user who suffered from subacute keratitis and progressive granulomatous uveitis. He underwent penetrating keratoplasty for corneal perforation, followed by cataract surgery due to rapid uveitic cataract. A few weeks later, intraocular lens removal and pars plana vitrectomy were necessary due to endophthalmitis. The patient was treated with topical, systemic, and intravitreal voriconazole with improvement; however, the visual outcome was poor. The pathogen was identified by MALDI-TOF MS.

Efficacy of Voriconazole Corneal Intrastromal Injection for the Treatment of Fungal Keratitis

Purpose

To evaluate efficacy and safety of novel tricyclic corneal stroma injection (TCSI) voriconazole for the treatment of fungal keratitis.

Methods

This retrospective cohort study included data of 57 patients (57 eyes) with fungal keratitis. The TCSI group consisted of 27 patients (27 eyes) who were injected voriconazole once via TCSI procedure within one week after enrollment, in addition to conventional antifungal treatment. The control group consisted of 30 patients (30 eyes) who were treated using conventional antifungal treatment modalities. The outcome measures consist of the 3-week and 3-month best-corrected visual acuity (BCVA) values and size of infiltrate or scar, time to re-epithelialization, corneal perforation rate and/or therapeutic penetrating keratoplasty (TPK) requirement, the preoperative and post-TCSI corneal endothelial cell density (ECD), and the intraocular pressure (IOP) of the treated eye and the respective contralateral eye.

Results

There were no significant differences in the baseline demographic and clinical characteristics between the two groups. 3 weeks and 3 months after enrollment, the TCSI group exhibited an increase in visual acuity (P < 0.05), and there was no significant difference in the size of infiltrate or scar between two groups (P > 0.05). Time to re-epithelialization was shorter in the TCSI group than in the control group (P < 0.05). There was no statistically significant difference between corneal ECD on the day before and 7 days after TCSI and the IOP of treated and contralateral healthy eyes on the day before and 1 day, 3 days, 7 days, and 1 month after TCSI (P > 0.05). The difference in the risk of perforation and/or TPK requirement was not statistically significant between two groups (P > 0.05).

Conclusion

Localized injection of voriconazole using TCSI may be a minimally invasive, safe, and effective adjuvant treatment modality for fungal keratitis.

Inhibitory Effect of Ophthalmic Solutions against SARS-CoV-2: A Preventive Action to Block the Viral Transmission?

In 2020, a global pandemic was declared following the spread of SARS-CoV-2, the pathogen responsible for COVID-19. The risk of infection is high due to the ease of transmission, which can occur orally, through droplets, or via contact with contaminated surfaces and objects. It has also been demonstrated that the ocular surface can constitute a transmission route, especially in hospital settings, where health care workers can become a dangerous source of infection. In order to increase prevention and reduce the spread of the virus on the ocular surface, the antiviral activity of already-marketed eye drops against SARS-CoV-2 was evaluated. Iodim, Ozodrop, Septavis, and Dropsept were tested against SARS-CoV-2 in plaque-assay experiments at different stimulation times. Furthermore, the expression levels of early and late genes were evaluated through molecular assays. Results indicated that three of the four ophthalmic solutions showed a considerable dose-dependent inhibition of viral replication, highlighting their use as potential antiviral drugs against SARS-CoV-2 and preventing other ocular infections.

Using Slit-Lamp Images for Deep Learning-Based Identification of Bacterial and Fungal Keratitis: Model Development and Validation with Different Convolutional Neural Networks

In this study, we aimed to develop a deep learning model for identifying bacterial keratitis (BK) and fungal keratitis (FK) by using slit-lamp images. We retrospectively collected slit-lamp images of patients with culture-proven microbial keratitis between 1 January 2010 and 31 December 2019 from two medical centers in Taiwan. We constructed a deep learning algorithm consisting of a segmentation model for cropping cornea images and a classification model that applies different convolutional neural networks (CNNs) to differentiate between FK and BK. The CNNs included DenseNet121, DenseNet161, DenseNet169, DenseNet201, EfficientNetB3, InceptionV3, ResNet101, and ResNet50. The model performance was evaluated and presented as the area under the curve (AUC) of the receiver operating characteristic curves. A gradient-weighted class activation mapping technique was used to plot the heat map of the model. By using 1330 images from 580 patients, the deep learning algorithm achieved the highest average accuracy of 80.0%. Using different CNNs, the diagnostic accuracy for BK ranged from 79.6% to 95.9%, and that for FK ranged from 26.3% to 65.8%. The CNN of DenseNet161 showed the best model performance, with an AUC of 0.85 for both BK and FK. The heat maps revealed that the model was able to identify the corneal infiltrations. The model showed a better diagnostic accuracy than the previously reported diagnostic performance of both general ophthalmologists and corneal specialists.

Eye Infections Caused by Filamentous Fungi: Spectrum and Antifungal Susceptibility of the Prevailing Agents in Germany

Fungal eye infections can lead to loss of vision and blindness. The disease is most prevalent in the tropics, although case numbers in moderate climates are increasing as well. This study aimed to determine the dominating filamentous fungi causing eye infections in Germany and their antifungal susceptibility profiles in order to improve treatment, including cases with unidentified pathogenic fungi. As such, we studied all filamentous fungi isolated from the eye or associated materials that were sent to the NRZMyk between 2014 and 2020. All strains were molecularly identified and antifungal susceptibility testing according to the EUCAST protocol was performed for common species. In total, 242 strains of 66 species were received. Fusarium was the dominating genus, followed by Aspergillus, Purpureocillium, Alternaria, and Scedosporium. The most prevalent species in eye samples were Fusarium petroliphilum, F. keratoplasticum, and F. solani of the Fusarium solani species complex. The spectrum of species comprises less susceptible taxa for amphotericin B, natamycin, and azoles, including voriconazole. Natamycin is effective for most species but not for Aspergillus flavus or Purpureocillium spp. Some strains of F. solani show MICs higher than 16 mg/L. Our data underline the importance of species identification for correct treatment.

Practical Guidance for Clinical Microbiology Laboratories: Diagnosis of Ocular Infections

The variety and complexity of ocular infections have increased significantly in the last decade since the publication of Cumitech 13B, Laboratory Diagnosis of Ocular Infections (L. D. Gray, P. H. Gilligan, and W. C. Fowler, Cumitech 13B, Laboratory Diagnosis of Ocular Infections, 2010). The purpose of this practical guidance document is to review, for individuals working in clinical microbiology laboratories, current tools used in the laboratory diagnosis of ocular infections. This document begins by describing the complex, delicate anatomy of the eye, which often leads to limitations in specimen quantity, requiring a close working bond between laboratorians and ophthalmologists to ensure high-quality diagnostic care. Descriptions are provided of common ocular infections in developed nations and neglected ocular infections seen in developing nations. Subsequently, preanalytic, analytic, and postanalytic aspects of laboratory diagnosis and antimicrobial susceptibility testing are explored in depth.

Beauveria bassiana keratitis: Management of an atypical clinical presentation

We report an atypical presentation of Beauveria bassiana keratitis which unusually presented in a 85-year-old patient with a corneal ulcer with an anterior segment inflammation and hypopyon. Despite negative culture and unspecific results from panfungal PCR-based sequencing, the patient was treated for a presumed fungal infection. Following clinical deterioration an emergency surgical intervention with apposition of a corneal patch was performed. Infection resolution was achieved following the introduction of systemic voriconazole to the topical one.

Candida Keratitis: Epidemiology, Management, and Clinical Outcomes

PURPOSE

To examine the epidemiological characteristics, trends, risk factors, management strategies, and clinical outcomes of Candida albicans and non-albicans keratitis over a 15-year period in a tertiary Canadian eye center.

METHODS

In a retrospective observational case series of Candida keratitis from 2003 to 2017, demographics, risk factors, corrected distance visual acuity (CDVA) at initial and final consultations, medical and surgical management, and follow-up duration were recorded.

RESULTS

Twenty-one cases of Candida keratitis were identified (62.5% of total fungal keratitis; 10 C. albicans and 11 non-albicans). The most commonly associated risk factors were topical steroid use (16 patients, 76%), ocular surface disease (15 patients, 71%), contact lens use (11 patients, 52%), and previous corneal surgery (8 patients, 38%); all patients had 2 or more combined risk factors. The number of patients with a visual acuity of 20/200 or better remained the same before and after the treatment (5/21, 24%). The mean duration of the antifungal treatment was 98 ± 126 days. Sixteen patients ultimately required surgical management (76%; 12 therapeutic keratoplasties, 3 enucleation, and 1 optical keratoplasty). When comparing C. albicans with non-albicans keratitis, we found no difference in presenting visual acuity, final visual acuity, or requirement for surgical management.

CONCLUSIONS

Candida keratitis accounts for the most identified fungal keratitis cases in this temperate climate area. An exposure to multiple risk factors appears necessary. A surgical intervention is required for the resolution of most cases. Different subspecies of Candida ultimately resulted in similar clinical outcomes.

Isorhamnetin Ameliorates Aspergillus fumigatus Keratitis by Reducing Fungal Load, Inhibiting Pattern-Recognition Receptors and Inflammatory Cytokines

Purpose

Isorhamnetin is a natural flavonoid with both antimicrobial and anti-inflammatory properties, but its effect on fungal keratitis (FK) remains unknown. The current study aims to investigate the antifungal and anti-inflammatory effects of isorhamnetin against mouse Aspergillus fumigatus keratitis.

Methods

In vitro, the lowest effective concentration of isorhamnetin was assessed by minimum inhibitory concentration and cytotoxicity tests in human corneal epithelial cells (HCECs) and RAW264.7 cells. The antifungal property was investigated by scanning electron microscopy and propidium iodide uptake test. The anti-inflammatory effect of isorhamnetin in HCECs and RAW264.7 cells was observed by quantitative real-time polymerase chain reaction (qRT-PCR). In the eyes of mice with A. fumigatus keratitis, FK severity was evaluated using clinical score, plate counting, histological staining and periodic acid Schiff staining. In vivo, the anti-inflammatory effect of isorhamnetin was examined by immunofluorescence staining, myeloperoxidase assay, Western blot, enzyme-linked immunosorbent assay, and qRT-PCR.

Results

In HCECs and RAW264.7 cells, isorhamnetin significantly inhibited A. fumigatus conidia growth and hyphae viability at 80 µg/mL without affecting cell viability. In vitro, isorhamnetin altered A. fumigatus hyphal morphology and membrane integrity. In A. fumigatus keratitis mouse model, isorhamnetin treatment alleviated the severity of FK by reducing corneal fungal load and inhibiting neutrophil recruitment. In addition, the mRNA and protein expression levels of TLR-2, TLR-4, Dectin-1, IL-1β, and tumor necrosis factor-α were significantly decreased in isorhamnetin-treated groups in vivo and in vitro.

Conclusions

Isorhamnetin improves the prognosis of A. fumigatus keratitis in mice by inhibiting the growth of A. fumigatus, reducing the recruitment of neutrophils and downregulating inflammatory factors.

Identification and molecular characterization of Subramaniula asteroides causing human fungal keratitis: a case report

Background

Keratitis due to by filamentous fungi are not easy to diagnose thus causing a delay in correct therapy. There are many descriptions of keratitis due to Candida, Fusarium and Aspergillus genera. Subramaniula genus has only recently been reported to cause human infections and there are few descriptions of eye infections due to this filamentous fungus. Diagnosis of fungal keratitis is usually based on microscopic and cultural techniques of samples obtained by corneal swabbing or scraping. Considering the amount of time required to obtain culture results it is wise to use other diagnostic methods, such as molecular analyses. Therapeutic options against these fungi are limited by low tissue penetration in the eye due to ocular barriers. We describe the first case of S. asteroides human keratitis treated with isavuconazole.

Case presentation

We describe a rare case of fungal keratitis unresponsive to antimicrobial treatment in a 65-year-old male patient without a history of diabetes or immunological diseases. He reported that the onset of symptoms occurred during a long holiday in Cape Verde Island. Initial treatment with topical antibiotics associated to steroids were ineffective, allowing a slow clinical progression of disease to corneal perforation. On admission in our Hospital, slit-lamp examination of the left eye showed conjunctival congestion and hyperemia, a large inferior corneal ulceration with brown pigment, corneal edema, about 3 mm of hypopyon and irido-lenticular synechiae. The slow clinical progression of the disease to corneal perforation and the aspect of the ulcer were consistent with a mycotic etiology. Molecular methods used on fungal colonies isolated by Sabouraud’s dextrose agar cultures allowed the identification of Subramaniula asteroids from corneal scraping. Antimicrobial test showed a good susceptibility of this filamentous fungus to voriconazole and isavuconazole. Moreover, this fungal keratitis was successfully treated with isavuconazole, without side effects, observing a progressive clinical improvement.

Conclusions

Molecular methods may be useful for the identification of filamentous fungal keratitis on scraping samples thus shortening the time of diagnosis. Systemic therapy by isavuconazole could be useful to treat the filamentous fungal keratitis, reducing the possible adverse effects due to the use of voriconazole by systemic administration.

Anti-inflammatory effects of astaxanthin against fungal keratitis

AIM

To characterize effect of astaxanthin (ASX) in Aspergillus fumigatus (A. fumigatus) induced keratitis in mouse model.

METHODS

In vivo, fungal keratitis mouse model was established in C57BL/6 mice using A. fumigatus, followed by ASX or dimethyl sulfoxide (DMSO) treatment. Clinical responses were evaluated by clinical score and myeloperoxidase (MPO) assay. Inflammatory cytokines were assessed by reverse-transcription polymerase chain reaction (RT-PCR), Western blot, immunofluorescence, and enzyme-linked immuno sorbent assay (ELISA).

RESULTS

In animal model, ASX improved corneal transparency and clinical response, suppressed the expression of inflammatory cytokine like IL-1β, TNF-α, and HMGB-1. Neutrophil levels have been shown to decrease in ASX-treated cornea by immunofluorescence and MPO. TLR2 and TLR4 levels were lower in ASX-treated group than DMSO-treated.

CONCLUSION

ASX can suppress inflammatory response and reduce inflammatory cytokine production in mice model with A. fumigatus keratitis.

In-vitro assessment of first-line antifungal drugs against Aspergillus spp. caused human keratomycoses

BACKGROUND AND OBJECTIVES

Aspergillus keratitis are in the increasing trend and reported as the second most common cause of mycotic keratitis in developing countries. The present study was designed to isolate, identify Aspergillus spp. from the keratits/corneal ulcer patients attending a tertiary care eye hospital, Coimbatore, South India and to assess the minimum inhibitory concentrations (MICs) against ten clinically used first-line antifungal drugs.

METHODS

A total of seventy-three Aspergillus strains isolated from corneal scrapings were included and assessed for a period of one year. All isolates were identified up to the species level by morphological observations. Antifungal drug susceptibilities were determined against a standard panel of antifungal agents.

CONCLUSIONS

Five different species of aspergilli, A. flavus (n=53), A. fumigatus (n=14), A. terreus (n=9), A. tamarii (n=6) and A. niger (n=3) were identified based on morphological features. Minimum inhibitory concentration analyses indicated that, voriconazole, natamycin, itraconazole, clotrimazole, econazole followed by ketoconazole shall be the order of choices for the effective treatment for Aspergillus keratitis.

Honokiol Reduces Fungal Load, Toll-Like Receptor-2, and Inflammatory Cytokines in Aspergillus fumigatus Keratitis

Purpose

We characterized the effects of Honokiol (HNK) on Aspergillus fumigatus-caused keratomycosis and the underlying mechanisms. HNK is known to have anti-inflammatory and antifungal properties, but the influence on fungal keratitis (FK) remains unknown.

Methods

In ex vivo, minimum inhibitory concentration and Cell Count Kit-8 assay were carried out spectrophotometrically to provide preferred concentration applied in vivo. Time kill assay pointed that HNK was fungicidal and fungistatic chronologically. Adherence assay, crystal violet staining, and membrane permeability assay tested HNK effects on different fungal stages. In vivo, clinical scores reflected the improvement degree of keratitis outcome. Myeloperoxidase (MPO) assay, flow cytometry (FCM), and immunohistofluorescence staining (IFS) were done to evaluate neutrophil infiltration. Plate count detected HNK fungicidal potentiality. RT-PCR, Western blot, and enzyme-linked immunosorbent assay (ELISA) verified the anti-inflammatory activity of HNK collaboratively.

Results

In vitro, MIC90 HNK was 8 µg/mL (no cytotoxicity), and Minimal Fungicidal Concentration (MFC) was 12 µg/mL for A. fumigatus. HNK played the fungistatic and fungicidal roles at 6 and 24 hours, respectively, inhibiting adherence at the beginning, diminishing biofilms formation, and increasing membrane permeability all the time. In vivo, HNK improved C57BL/6 mice outcome by reducing disease severity (clinical scores), neutrophil infiltration (MPO, FCM, and IFS), and fungal loading (plate count). RT-PCR, Western blot, and ELISA revealed that HNK downregulated mRNA and protein expression levels of Toll-like receptor-2 (TLR-2), high mobility group box 1 (HMGB1), IL-1β, and TNF-α.

Conclusions

Our study suggested HNK played antifungal and anti-inflammatory roles on keratomycosis by reducing survival of fungi, infiltration of leucocytes, and expression of HMGB1, TLR-2, and proinflammatory cytokines, providing a potential treatment for FK.

Synthesis of Novel Stilbene-Coumarin Derivatives and Antifungal Screening of Monotes kerstingii-Specialized Metabolites Against Fusarium oxysporum

Fusarium is one of the most toxigenic phytopathogens causing diseases and reduced agricultural productivity worldwide. Current chemical fungicides exhibit toxicity against non-target organisms, triggering negative environmental impact, and are a danger to consumers. In order to explore the chemical diversity of plants for potential antifungal applications, crude extract and fractions from Monotes kerstingii were screened for their activity against two multi-resistant Fusarium oxysporum strains: Fo32931 and Fo4287. Antifungal activity was evaluated by the determination of minimum inhibitory concentration (MIC) by broth dilution of fermentative yeasts using kinetic OD_{600 nm} reading by a spectrophotometer. The n-butanol fraction showed the best activity against Fo4287. We screened eleven previously reported natural compounds isolated from different fractions, and a stilbene-coumarin 5-[(1E)-2-(4-hydroxyphenyl)ethenyl]-4,7-dimethoxy-3-methyl-2H-1-benzopyran-2-one (1) was the most active compound against both strains. Compound 1 was employed as a nucleophile with a selection of electrophilic derivatizing agents to synthesize five novel stilbene-coumarin analogues. These semisynthetic derivatives showed moderate activity against Fo32931 with only prenylated derivative exhibiting activity comparable to the natural stilbene-coumarin (1), demonstrating the key role of the phenolic group.

Voriconazole Induced Ocular Surface Dysplasia - Report of Two Cases

PURPOSE

To report ocular surface dysplasia induced by voriconazole treatment in two patients with recalcitrant fungal keratitis.

METHODS

Observational study.

RESULTS

Case 1 - A 49 year old female who was a known case of fungal keratitis and treated with prolonged topical voriconazole therapy, underwent penetrating keratoplasty and the histopathological examination of corneal specimen showed multiple keratin pearls with dyskeratotic cells suggestive of squamous cell carcinoma.Case 2 - A 78-year-old man who was diagnosed as fungal keratitis in his left eye and treated with topical voriconazole 1% and itraconazole 1% for 6 months underwent therapeutic penetrating keratoplasty. Histopathology of the host corneal tissue showed squamous cells with irregular thickening with dyskeratotic cells and squamous eddies suggestive of voriconazole induced dysplasia.

CONCLUSION

Prolonged topical voriconazole treatment in fungal keratitis can induce ocular surface dysplasia. Early diagnosis and treatment of the dysplastic changes can result in complete remission and prevent recurrence.

[Epidemiology and treatment of fungal keratitis]

Infectious keratitis in most cases is caused by bacterial, viral or fungal agents, but their structure is changing. Some researchers have noted a substantial increase in fungal corneal lesions in recent decades, but important local etiological therapy remains unavailable in developing countries. While bacterial keratitis and ophthalmoherpes are controlled by widely available local etiotropic therapy, treatment of keratomycosis in the Russian Federation is carried out with off-label medicine. Lack of skills and availability of diagnostic methods and official etiotropic therapy creates unequal conditions for ophthalmology specialists in the fight against ophthalmomycosis. In part, this causes a reduced level of «myco-caution», which leads to long-term ineffective treatment using antibacterial drops, lasting suffering of patients, and results in the loss of the eye functionally and - in some cases - anatomically. Therefore, the study of fungal keratitis remains relevant. The article provides an overview of research data on current epidemiology in different regions of the world, analyzes available antifungal drugs and the prospects for development of affordable and effective treatment of fungal keratitis.

Filamentous Fungal Keratitis in Taiwan: Based on Molecular Diagnosis

Purpose

To analyze the epidemiological pattern, demographics, risk factors, and treatment outcomes of filamentous fungal keratitis at a tertiary hospital in Taiwan.

Methods

We recruited 65 patients (65 eyes) with culture-proven filamentous fungal keratitis who received diagnosis and treatment at Chang Gung Memorial Hospital between 2015 and 2018. All isolates were examined through conventional morphological identification and subjected to molecular identification with internal transcribed spacer sequencing. Data on patient demographics, predisposing factors, and treatment outcomes were collected.

Results

In total, filamentous fungi belonged to 16 genera were identified. Fusarium spp. (29 cases [44.6%]) was the most commonly isolated organism overall, followed by Colletotrichum spp. and Purpureocillium linacinum (seven cases [10.8% for each]), and Aspergillus spp. (six cases [9.2%]). Some fungi that have not been regarded as human pathogens were also identified, such as Paracremonium and Phellinum. Among 52 (80%) patients with predisposing factors, 30 (46.2%) had trauma. The ulcers of 33 (50.8%) patients resolved with medical treatment only. Additionally, six patients (9.2%) had corneal perforation, and nine patients (13.9%) required therapeutic/destructive surgical interventions including therapeutic penetrating keratoplasty (seven patients) or evisceration (two patients). Only 16 patients (24.6%) had final visual acuity of 20/40 or better.

Conclusions

Through molecular diagnosis, a high diversity of fungal pathogens was revealed along with an increasing incidence of Colletotrichumspp. and Purpureocilliumspp. in Taiwan. The most common risk factor for filamentous fungal keratitis was trauma. The visual outcomes were guarded.

Translational Relevance

The molecular diagnosis provides insight into accurate identification, which affects the epidemiology and diversity of pathogens of filamentous fungal keratitis.

Antimycotic Activity of Ozonized Oil in Liposome Eye Drops against Candida spp

Purpose

This study aims to investigate the antifungal activity and mechanism of action of ozonized oil eye drops in liposomes (Ozodrop), commercialized as eye lubricant for the treatment of dry eye syndrome and eye inflammation. The activity was tested against four clinical Candida species: C albicans, C glabrata, C krusei, and C orthopsilosis.

Methods

The antifungal activity of the eye drop solution was ascertained by microdilution method in accordance with EUCAST obtaining the minimum inhibitory concentration for Ozodrop. The mechanism of action was further investigated in C albicans by measuring cell vitality, intracellular reactive oxygen species production, levels of cellular and mitochondrial (∆Ψ_m) membrane potential, and the extent of membrane lipid peroxidation.

Results

All Candida isolates were susceptible to Ozodrop with minimum inhibitory concentration values ranging from 0.195% (v/v) for C glabrata to 6.25% (v/v) for C orthopsilosis. After 1 hour of exposure at the minimum inhibitory concentration value about 30% of cells were killed, reaching about 70% at the highest Ozodrop value. After Ozodrop exposure, C albicans showed cell membrane depolarization, increased levels of lipid peroxidation, depolarized ∆Ψ_m, and increased reactive oxygen species generation.

Conclusions

The significant increases in reactive oxygen species production cause the accumulation of reactive oxygen species-associated damages leading to progressive Candida cell dysfunction.

Translational Relevance

The antifungal activity of Ozodrop was demonstrated at concentrations several times lower than the concentration that can be retrieved in ocular surface after its application. The antifungal activity of the eye drops Ozodrop would represent an interesting off-label indication for a product basically conceived as an eye lubricant.

Agricultural systems as potential sources of emerging human mycoses caused by Trichoderma: a successful, common phylotype of Trichoderma longibrachiatum in the frontline

Trichoderma species are abundant in different agricultural habitats, but some representatives of this genus, mainly clade Longibrachiatum members are also emerging as causative agents of various human diseases with even fatal outcome. Strains of these species frequently show resistance to commonly used azole antifungals. Based on previous data it is hypothesized that Trichoderma isolates identified in human infections derive from environmental-including agricultural-origins. We examined Trichoderma longibrachiatum Rifai and Trichoderma bissettii Sandoval-Denis & Guarro strains recovered from four novel cases of human mycoses, along with isolates from previous case reports and different agricultural habitats, using multilocus phylogenetic analysis, BIOLOG Phenotype Microarrays and Etest. Strains attributed to T. bissettii were more abundant in both clinical and agricultural specimens compared to T. longibrachiatum. The majority of the isolates of both taxa could tolerate >256, >32 and >32 μg/ml fluconazole, itraconazole and posaconazole, respectively. None of the obtained results revealed characteristic differences between strains of clinical and agricultural origin, nor between the two taxa, supporting that agricultural environments may be significant sources of infections caused by these emerging human fungal pathogens. Furthermore, based on our findings we propose the re-classification of T. bissettii as T. longibrachiatum f. sp. bissettii.

Structural basis of Fusarium myosin I inhibition by phenamacril

Fusarium is a genus of filamentous fungi that includes species that cause devastating diseases in major staple crops, such as wheat, maize, rice, and barley, resulting in severe yield losses and mycotoxin contamination of infected grains. Phenamacril is a novel fungicide that is considered environmentally benign due to its exceptional specificity; it inhibits the ATPase activity of the sole class I myosin of only a subset of Fusarium species including the major plant pathogens F. graminearum, F. asiaticum and F. fujikuroi. To understand the underlying mechanisms of inhibition, species specificity, and resistance mutations, we have determined the crystal structure of phenamacril-bound F. graminearum myosin I. Phenamacril binds in the actin-binding cleft in a new allosteric pocket that contains the central residue of the regulatory Switch 2 loop and that is collapsed in the structure of a myosin with closed actin-binding cleft, suggesting that pocket occupancy blocks cleft closure. We have further identified a single, transferable phenamacril-binding residue found exclusively in phenamacril-sensitive myosins to confer phenamacril selectivity.

Phenamacril is a recently identified myosin I inhibitor that is a potent and highly species-specific and myosin subtype-selective fungicide. We report the high-resolution structure of the phenamacril-bound myosin I motor domain of the major crop pathogen Fusarium graminearum, providing insight into the molecular mechanism of phenamacril action and resistance. These results are of broad significance for understanding the mode of actions of myosin-based fungicides and for designing novel myosin I inhibitors for crop protection and for treatment of human myosin dysfunction diseases.

Surface modified electrospun poly(lactic acid) fibrous scaffold with cellulose nanofibrils and Ag nanoparticles for ocular cell proliferation and antimicrobial application

Corneal and conjunctival infections are common ocular diseases, sometimes, causing severe and refractory drug-resistant bacteria infections. Fungal keratitis is a leading cause for blindness and traditional medical treatment is unsatisfactory. Thus, there is an urge to develop a new therapy to deal with these cases. In this study, we developed surface modified poly(lactic acid) (PLA) electrospun nanofibrous membranes (EFMs) with silver nanoparticles (AgNPs) and cellulose nanofibrils (CNF) as scaffolds for cell proliferation and antimicrobial application. The AgNPs with a very low content (below 0.1%) were easily anchored on the surface of PLA EFMs by CNF, which endowed the scaffold with hydrophilicity and antibacterial ability. The in-vitro cell co-culture experiments showed that the scaffold had great biocompatibility to ocular epithelial cells, especially the scaffolds coated by CNF, which significantly proliferated cells. Furthermore, the antibacterial activity could reach >95% inhibiting Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) due to the implantation of AgNPs, and the antifungal activity was also outstanding with most of the Fusarium spp. inhibited. Hence, the developed PLA EFMs with CNF and AgNPs are promising ocular bandages to promote cell proliferation and kill infectious pathogens, exhibiting potential applications in ocular wound healing in the future.