Mycotic keratitis: an overview of diagnosis and therapy

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.

Antifungal Combination Eye Drops for Fungal Keratitis Treatment

Fungal keratitis (FK) is a corneal mycotic infection that can lead to vision loss. Furthermore, the severity of FK is aggravated by the emergence of resistant fungal species. There is currently only one FDA-approved formulation for FK treatment forcing hospital pharmacy departments to reformulate intravenous drug preparations with unknown ocular bioavailability and toxicity. In the present study, natamycin/voriconazole formulations were developed and characterized to improve natamycin solubility, permanence, and safety. The solubility of natamycin was studied in the presence of two cyclodextrins: HPβCD and HPγCD. The HPβCD was chosen based on the solubility results. Natamycin/cyclodextrin (HPβCD) inclusion complexes characterization and a competition study between natamycin and voriconazole were conducted by NMR (Nuclear Magnetic Resonance). Based on these results, several eye drops with different polymer compositions were developed and subsequently characterized. Permeability studies suggested that the formulations improved the passage of natamycin through the cornea compared to the commercial formulation Natacyn^®. The ocular safety of the formulations was determined by BCOP and HET-CAM. The antifungal activity assay demonstrated the ability of our formulations to inhibit the in vitro growth of different fungal species. All these results concluded that the formulations developed in the present study could significantly improve the treatment of FK.

Stability of voriconazole 10 mg/mL ophthalmic solution during 90 days

Objectives

Fungal keratitis is a rare but severe cause of infectious keratitis and can lead to blindness. To cure fungal keratitis, antifungal like voriconazole eye drops must be immediately administered. As no brand is available on the market, voriconazole ophthalmic solution is compounded in hospital pharmacies using voriconazole powder for intravenous infusion. The aims of our study were to both assess the physico-chemical and microbiological stability of eye drop solutions stored at +2 to 8 °C. Two different High-Density-Polyethylene (HDPE) eye drop dispensing containers were assessed, one with a sterility preserving cap Novelia®(Nemera) and the other without sterility preserving cap both provided by CAT laboratory. In addition microbiological quality was assessed during 15 days simulated patient use.

Methods

Multiple batches of voriconazole 10 mg/mL eye drops were prepared and stored at +2 to 8 °C to study their stability over 90 days. All analyses were performed in triplicate. Physical stability was determined, pH determination, osmolarity measurement, and a particle count test was also performed. A high performance liquid chromatography (HPLC-UV) stability indicating method was used to determine chemical stability of the ophthalmic solution over 90 days of storage. For microbiological stability, a sterility test was performed using closed membrane filtration method (Steritest®, Merck Millipore) at D0, D90 and D90+15 days after simulated administration of eye drops (D90+15).

Results

For both containers, no variation of visual aspect, pH, osmolality, particle count and final concentration were observed. No microbiological growth was observed after 90 days of storage. At the end of the simulated administration period (D+15), unconstant microbiological growth was only observed in HDPE vials without sterility preserving cap, whereas HDPE vials with a sterility preserving cap Novelia®(Nemera) remained sterile.

Conclusions

Voriconazole 10 mg/mL ophtalmic solution was stable during 90 days at +2 to 8 °C in lightproof HDPE vials without sterility preserving cap and HDPE vials with a sterility preserving cap Novelia®(Nemera). However, vials with classical cap which are not airtight systems, may microbiologically contaminated during patient’s use than vials with Novelia® cap thanks to their innovative valve system.

Case Report: Molecular Diagnosis of Fungal Keratitis Associated With Contact Lenses Caused by Fusarium solani

Fusarium is a filamentous fungus commonly found in the environment and is the major cause of fungal keratitis. We report a case of keratomycosis caused by Fusarium solani in a patient using disposable soft contact lenses. A delay in diagnosis led to the initiation of an empirical antifungal treatment with the subsequent deterioration of the patient's clinical condition. The use of the real-time quantitative PCR assay confirmed keratitis from F. solani providing a result in <48 h and therefore giving the possibility of quickly starting targeted antifungal therapy. The patient had an improvement in eye condition after the diagnosis of keratitis by F. solani and the rapid change to targeted antifungal treatment. For the rapid identification of corneal fungal pathogens, we believe that PCR may be added for the diagnosis of mycotic keratitis pending the isolation in culture that is necessary for in vitro susceptibility testing.

Topical Corticosteroids and Fungal Keratitis: A Review of the Literature and Case Series

The management of fungal keratitis is complex since signs and symptoms are subtle and ocular inflammation is minimal in the preliminary stages of infection. Initial misdiagnosis of the condition and consequent management of inflammation with corticosteroids is a frequent occurrence. Topical steroid use is considered to be a principal factor for development of fungal keratitis. In this review, we assess the studies that have reported outcomes of fungal keratitis in patients receiving steroids prior to diagnosis. We also assess the possible rebound effect present when steroids are abruptly discontinued and the clinical characteristics of three patients in this particular clinical scenario. Previous reports and the three clinical descriptions presented suggest that in fungal keratitis, discontinuing topical steroids can induce worsening of clinical signs. In these cases, we recommend to slowly taper steroids and continue or commence appropriate antifungal therapy.

In situ forming and mucoadhesive ophthalmic voriconazole/HPβCD hydrogels for the treatment of fungal keratitis

Fungal keratitis is a severe infectious corneal disease. At present, no voriconazole ophthalmic formulations are approved by the FDA or EMA. This lack of therapeutic options leads to the reformulation of intravenous voriconazole preparations (VFEND®) by the hospital pharmacy departments to prepare the appropriate ophthalmic formulations (pharmacy compounding). However, the limited residence time of these formulations leads to an intensive treatment posology that may increase the occurrence of side effects. In the present study, two different hydrogels were developed and characterized in order to improve the voriconazole's ophthalmic solubility, permanence, and security. Voriconazole-cyclodextrin (HPβCD or HPɣCD) inclusion complexes in aqueous solutions were characterized by NMR and molecular modeling. Complexes were formed by encapsulation of voriconazole into the cyclodextrin's internal cavity which considerably increases its water solubility. Ocular safety was proven by ocular irritation studies. Permeability studies suggest both hydrogels have good corneal permeability. Furthermore, in vivo ocular permanence study by PET/CT showed a longer permanence time on the ocular surface (t_1/2 = 58.91 ± 13.4 min and 96.28 ± 49.11 min for VZHAH and VZISH 0.65 respectively) compared to the voriconazole control formulation (VFEND® t_1/2 = 32.27 ± 15.56 min). Results suggest these formulations are a good alternative for the treatment of fungal keratitis.

Genetically Engineered Elastin-based Biomaterials for Biomedical Applications

Protein-based polymers are some of the most promising candidates for a new generation of innovative biomaterials as recent advances in genetic-engineering and biotechnological techniques mean that protein-based biomaterials can be designed and constructed with a higher degree of complexity and accuracy. Moreover, their sequences, which are derived from structural protein-based modules, can easily be modified to include bioactive motifs that improve their functions and material-host interactions, thereby satisfying fundamental biological requirements. The accuracy with which these advanced polypeptides can be produced, and their versatility, self-assembly behavior, stimuli-responsiveness and biocompatibility, means that they have attracted increasing attention for use in biomedical applications such as cell culture, tissue engineering, protein purification, surface engineering and controlled drug delivery. The biopolymers discussed in this review are elastin-derived protein-based polymers which are biologically inspired and biomimetic materials. This review will also focus on the design, synthesis and characterization of these genetically encoded polymers and their potential utility for controlled drug and gene delivery, as well as in tissue engineering and regenerative medicine.

Fungal keratitis: Pathogenesis, diagnosis and prevention

As a kind of serious, potentially sight-threatening corneal infections with poor prognosis, fungal keratitis can bring a heavy economic burden to patients and seriously affect the quality of life, especially those in developing countries where fungal keratitis is more prevalent. Typical clinical features include immune rings, satellite lesions, pseudopods, hypha moss, hypopyon and endothelial plaques. The ideal therapeutic effects could not be achieved by current treatments for many reasons. Therefore, under the current status, understanding the pathogenesis, early diagnosis and prevention strategies might be of great importance. Here, in this review, we discuss the recent progresses that may advance our understanding of pathogenesis, early diagnosis and prevention of fungal keratitis.

A case of fungal keratitis due to Fusarium solani after an indigenous healing practice

Fusarium keratomycosis is a destructive eye infection that is difficult to treat and produces a poor outcome, which can affect healthy patients. Keratomycoses are rare and can be underdiagnosed, thus, direct microscopic examination and culture are essential for an early specific diagnosis and must be taken into consideration to establish the most effective treatment and avoid severe complications. Herein, we present a case of a healthy patient, who was diagnosed with Fusarium solani keratitis. He developed a corneal infection without an obvious history of trauma, and any comorbidity but with a history of contact with juice of herbs during an indigenous healing practice, which was the most likely cause for the development of the fungal infection. He was treated with intrastromal voriconazole and systemic itraconazole, with a good clinical course, however with sequelae of decreased visual acuity.

In Vitro Activity of Chlorhexidine Compared with Seven Antifungal Agents against 98 Fusarium Isolates Recovered from Fungal Keratitis Patients

Fungal keratitis is a common but severe eye infection in tropical and subtropical areas of the world. In regions with a temperate climate, the frequency of infection is rising in patients with contact lenses and following trauma. Early and adequate therapy is important to prevent disease progression and loss of vision. The management of Fusarium keratitis is complex, and the optimal treatment is not well defined. We investigated the in vitro activity of chlorhexidine and seven antifungal agents against a well-characterized collection of Fusarium isolates recovered from patients with Fusarium keratitis. The fungus culture collection of the Center of Expertise in Mycology Radboudumc/CWZ was searched for Fusarium isolates that were cultured from cornea scrapings, ocular biopsy specimens, eye swabs, and contact lens fluid containers from patients with suspected keratitis. The Fusarium isolates that were cultured from patients with confirmed keratitis were all identified using conventional and molecular techniques. Antifungal susceptibility testing was performed according to the EUCAST broth microdilution reference method. The antifungal agents tested included amphotericin B, voriconazole, posaconazole, miconazole, natamycin, 5-fluorocytosine, and caspofungin. In addition, the activity of chlorhexidine was determined. The fungal culture collection contained 98 Fusarium isolates of confirmed fungal keratitis cases from 83 Dutch patients and 15 Tanzanian patients. The isolates were collected between 2007 and 2017. Fusarium oxysporum (n = 24, 24.5%) was the most frequently isolated species followed by Fusarium solani sensu stricto (n = 18, 18.4%) and Fusarium petroliphilum (n = 11, 11.2%). Amphotericin B showed the most favorable in vitro inhibition of Fusarium species followed by natamycin, voriconazole, and chlorhexidine, while 5-fluorocytosine, posaconazole, miconazole, and caspofungin showed no relevant inhibiting effect. However, chlorhexidine showed fungicidal activity against 90% of F. oxysporum strains and 100% of the F. solani strains. Our study supports the clinical efficacy of chlorhexidine and therefore warrants its further clinical evaluation for primary therapy of fungal keratitis, particularly in low and middle income countries where fungal keratitis is much more frequent and, currently, antifungal eye drops are often unavailable.

Evolving nanotechnological trends in the management of mycotic keratitis

The alarming increase in global burden of various corneal diseases in general and mycotic keratitis in particular has raised up a major concern for its treatment. Mycotic keratitis is one of the most serious infections among the various ocular diseases. The proper diagnosis and effective treatment strategies remain a great challenge for ophthalmologists. The inefficacy and failure of conventional treatments have generated need to develop alternative approaches for the treatment of mycotic keratitis. Considering the promising applications of nanotechnology in biomedical area, it is believed that various nanomaterials can be effectively used in the management of mycotic keratitis. This review focuses on worldwide burden of various corneal diseases including mycotic keratitis and the role of nanotechnology in its treatment. In addition, safety and toxicological issues are also discussed.

Removing chaos from confusion: assigning names to common human and animal pathogens in Neocosmospora

The genus Neocosmospora encompasses highly prevalent and aggressive human and animal fungal pathogens. Here we assign formal descriptions and Latin binomials to some of the most clinically relevant phylogenetic species of the genus. Three new species, named Neocosmospora catenata, N. gamsii and N. suttoniana (previously assigned to the informal names 'Fusarium' solani species complex (FSSC) lineages, FSSC 43, FSSC 7 and FSSC 20, respectively) are described on the basis of multilocus phylogenetic analyses (using EF-1α, ITS, LSU and RPB2 loci) and morphological characters. Lineage FSSC 9 is conspecific with the ex-type strain of Cylindrocarpon tonkinense, thus the new combination Neocosmospora tonkinensis is proposed. In addition, and based on the latest taxonomy for this generic complex, new combinations are introduced for four medically important taxa: Neocosmospora keratoplastica, N. lichenicola, N. metavorans and N. petroliphila. The most significant distinctive features for all the clinically relevant species treated here are compared and illustrated.

South Indian Isolates of the Fusarium solani Species Complex From Clinical and Environmental Samples: Identification, Antifungal Susceptibilities, and Virulence

Members of the Fusarium solani species complex (FSSC) are the most frequently isolated fusaria from soil. Moreover, this complex solely affects more than 100 plant genera, and is also one of the major opportunistic human pathogenic filamentous fungi, being responsible for approximately two-third of fusariosis cases. Mycotic keratitis due to Fusarium species is among the leading causes of visual impairment and blindness in South India, but its management is still challenging due to the poor susceptibility of the isolates to conventional antifungal drugs. Aims of the present study were to isolate South Indian clinical and environmental FSSC strains and identify them to species level, to determine the actual trends in their susceptibilities to antifungal therapeutic drugs and to compare the virulence of clinical and environmental FSSC members. Based on the partial sequences of the translation elongation factor 1α gene, the majority of the isolates-both from keratomycosis and environment-were confirmed as F. falciforme, followed by F. keratoplasticum and F. solani sensu stricto. In vitro antifungal susceptibilities to commonly used azole, allylamine and polyene antifungals were determined by the CLSI M38-A2 broth microdilution method. The first generation triazoles, fluconazole and itraconazole proved to be ineffective against all isolates tested. This phenomenon has already been described before, as fusaria are intrinsically resistant to them. However, our results indicated that despite the intensive agricultural use of azole compounds, fusaria have not developed resistance against the imidazole class of antifungals. In order to compare the virulence of different FSSC species from clinical and environmental sources, a Drosophila melanogaster model was used. MyD88 mutant flies having impaired immune responses were highly susceptible to all the examined fusaria. In wild-type flies, one F. falciforme and two F. keratoplasticum strains also reduced the survival significantly. Pathogenicity seemed to be independent from the origin of the isolates.

Rare fungal infectious agents: a lurking enemy

In the expanding population of immunocompromised patients and those treated in intensive care units, rare fungal infectious agents have emerged as important pathogens, causing invasive infections associated with high morbidity and mortality. These infections may present either as de novo or as breakthrough invasive infections in high-risk patients with hematologic malignancies receiving prophylactic or empirical antifungal therapy or in patients with central venous catheters. Diagnosis and treatment are challenging. Physicians should have a high index of suspicion because early diagnosis is of paramount importance. Conventional diagnostic methods such as cultures and histopathology are still essential, but rapid and more specific molecular techniques for both detection and identification of the infecting pathogens are being developed and hopefully will lead to early targeted treatment. The management of invasive fungal infections is multimodal. Reversal of risk factors, if feasible, should be attempted. Surgical debridement is recommended in localized mold infections. The efficacy of various antifungal drugs is not uniform. Amphotericin B is active against most yeasts, except Trichosporon, as well as against Mucorales, Fusarium, and some species of Paecilomyces and dimorphic fungi. The use of voriconazole is suggested for the treatment of trichosporonosis and scedosporiosis. Combination treatment, though recommended as salvage therapy in some infections, is controversial in most cases. Despite the use of available antifungals, mortality remains high. The optimization of molecular-based techniques, with expansion of reference libraries and the possibility for direct detection of resistance mechanisms, is awaited with great interest in the near future. Further research is necessary, however, in order to find the best ways to confront and destroy these lurking enemies.

Fungal keratitis caused by rare organisms

Purpose

To report two rare cases of filamentous fungal keratitis.

Methods

Two non-consecutive patients presented with suspicious fungal keratitis. After performing the smear and culture, medical therapy was started for them. They underwent slit photography and in vivo confocal microscopy (IVCM) in their follow-up visits.

Results

The patients were 33-year-old and 56-year-old farmer men. They both mentioned a history of ocular trauma by plants. During their follow-up visits, corneal infiltration density and fungal hyphae density decreased in slit-lamp biomicroscopy and IVCM, respectively. The corresponding organisms were Pseudallescheria boydii (P. boydii) and Colletotrichum coccodes.

Conclusions

It is important to be aware of these rare organisms and their antibiotic susceptibility. There was not any specific confocal feature for the presented fungal keratitis that was different from other filamentous fungal hyphae; however, confocal scan is a good choice to follow the response to the treatment.

A Hydrogel-Based Hybrid Theranostic Contact Lens for Fungal Keratitis

Fungal keratitis, a severe ocular disease, is one of the leading causes of ocular morbidity and blindness, yet it is often neglected, especially in developing countries. Therapeutic efficacy of traditional treatment such as eye drops is very limited due to poor bioavailability, whereas intraocular injection might cause serious side effects. Herein, we designed and fabricated a hybrid hydrogel-based contact lens which comprises quaternized chitosan (HTCC), silver nanoparticles, and graphene oxide (GO) with a combination of antibacterial and antifungal functions. The hydrogel is cross-linked through electrostatic interactions between GO and HTCC, resulting in strong mechanical properties. Voriconazole (Vor), an antifungal drug, can be loaded onto GO which retains the drug and promotes its sustained release from the hydrogel-based contact lenses. The contact lenses also exhibited good antimicrobial functions in view of glycidyltrimethylammonium chloride and silver nanoparticles. The results from in vitro and in vivo experiments demonstrate that contact lenses loaded with Vor have excellent efficacy in antifungal activity in vitro and could significantly enhance the therapeutic effects on a fungus-infected mouse model. The results indicate that this hydrogel contact lenses-based drug delivery system might be a promising therapeutic approach for a rapid and effective treatment of fungal keratitis.

Geographic Disparities in the Etiology of Bacterial and Fungal Keratitis in the United States of America

Infectious keratitis is a serious cause of vision loss. Proper treatment of infectious keratitis requires antimicrobials that target the organism responsible for a patient's ulcer. The frequency of infection by a given organism varies by location. We examined the literature to determine geographic disparities in the etiology of bacterial and fungal keratitis in the United States of America. Bacterial keratitis makes up a greater proportion of cases in northern locations, and fungal keratitis increases in prevalence in southern locations. Gram-negative organisms make up a greater proportion of bacterial keratitis in southern locations when compared to northern locations.

Etiological Analysis of Fungal Keratitis and Rapid Identification of Predominant Fungal Pathogens

Fungal keratitis is a worldwide-distributed refractory and potentially blinding ocular infection caused by various fungi. It is necessary to investigate the etiological and epidemiological characteristics of this disease and establish a rapid and specific pathogenic identification method. Here, we isolated and identified fungal pathogens of 275 patients with presumed fungal keratitis from Jilin Province, China, and conducted statistical analyses of epidemiological information. The positive rate of fungal culture was 72.0 %. Fusarium sp. was the most common genus among 210 fungal isolates. The predominant species were Fusarium solani, Aspergillus fumigatus, and Candida glabrata, which accounted for over 50 % of the isolated organisms. Corneal trauma and previous use of drugs were the most important predisposing factors. In addition, a multiplex polymerase chain reaction (PCR) was designed with species-specific primers of the three species that could identify them with amplicons of approximately 330 bp from F. solani, 275 bp from A. fumigatus, and 230 bp from C. glabrata. Additionally, PCR with fungal universal primers and multiplex PCR were performed using DNA prepared by an improved DNA extraction method from corneal scrapings. With this method, fungal pathogens from corneal scrapings could be specifically and rapidly identified within 8 h. The culture-independent rapid identification of corneal scrapings may have great significance for the early diagnosis and treatment of fungal keratitis.

Molecular identification and antifungal susceptibility of Curvularia australiensis, C. hawaiiensis and C. spicifera isolated from human eye infections

A reliable identification method was developed for three closely related Curvularia species, which are frequently isolated from human keratomycoses. Since the traditionally used morphological method and the increasingly used internal transcribed spacer (ITS)-based molecular method proved to be insufficient to discern C. australiensis, C. hawaiiensis and C. spicifera, other molecular targets, such as β-tubulin, translation elongation factor 1-α and the nuclear ribosomal intergenic spacer (IGS), were tested. Among them, the use of the highly divergent IGS sequence is suggested and the species-specific discriminating characters were determined in appropriate reference strains. It was also concluded that C. hawaiiensis and C. spicifera can be predominantly isolated from eye infections among the three species. The in vitro antifungal susceptibility of 10 currently used antifungal agents against 32 Curvularia isolates was also investigated. MICs were determined in each case. Isolates of C. spicifera proved to be less susceptible to the tested antifungals than those of C. hawaiiensis, which underline the importance of the correct identification of these species.

Multidrug resistant Fusarium keratitis

CASE REPORT

We report a case of keratitis in a female contact lens wearer, who developed a deep corneal abscess. The culture of a corneal biopsy scraping was positive for multiresistant Fusarium solani. The patient has a complicated clinical course and failed to respond to local and systemic antifungal treatment, requiring eye enucleation.

CONCLUSION

Fusarium keratitis may progress to severe endophthalmitis. Clinical suspicion is paramount in order to start antifungal therapy without delay. Therapy is complex due to the high resistance of this organism to usual antifungal drugs.

Tear-mediated delivery of nanoparticles through transcytosis of the lacrimal gland

Rapid clearance from the tears presents a formidable obstacle to the delivery of peptide drugs to the eye surface. This impedes therapies for ocular infections, wound healing, and dry-eye disease that affect the vision of millions worldwide. To overcome this challenge, this manuscript explores a novel strategy to reach the ocular surface via receptor-mediated transcytosis across the lacrimal gland (LG), which produces the bulk of human tears. The LG abundantly expresses the coxsackievirus and adenovirus receptor (CAR); furthermore, we recently reported a peptide-based nanoparticle (KSI) that targets CAR on liver cells. This manuscript reports the unexpected finding that KSI both targets and transcytoses into the LG acinar lumen, which drains to tear ducts. When followed using ex vivo live cell imaging KSI rapidly accumulates in lumen formed by LG acinar cells. LG transduction with a myosin Vb tail, which is dominant negative towards transcytosis, inhibits lumenal accumulation. Transcytosis of KSI was confirmed in vivo by confocal and TEM imaging of LG tissue following administration of KSI nanoparticles. These findings suggest that it is possible to target nanomaterials to the tears by targeting certain receptors on the LG. This design strategy represents a new opportunity to overcome barriers to ocular delivery.

Non traumatic keratitis due to colletotrichum coccodes: a case report

Colletotrichum species, a rare and emerging fungus is a well- known plant pathogen and an uncommon cause of human infection. It has been implicated as the etiological agent of cutaneous phaeohyphomycosis and keratitis, particularly following colonization of traumatized tissues or in immunocompromised patients. However, it has hardly ever been reported in the absence of such predisposing risk factors. Here, we report a case of keratitis with Colletotrichum coccodes occurring in a middle- aged, immunocompetent person without any history of trauma or co-morbidity. The isolate was sensitive to Amphotericin B and Voriconazole, and accordingly the patient was treated successfully with ocular administration of Amphotericin B.

First unusual case of keratitis in Europe due to the rare fungus Metarhizium anisopliae

Metarhizium anisopliae is a fungus utilized worldwide for insect-pest biocontrol. Few M. anisopliae infections have been reported previously. Here, M. anisopliae was isolated from a corneal ulcer in a healthy man. It is the first ocular case in France and Europe of this extremely rare fungus in humans.

DOPA and DHN pathway orchestrate melanin synthesis in Aspergillus species

Melanins are high molecular weight hydrophobic pigments that have been studied for their role in the virulence of fungal pathogens. We investigated the amount and type of melanin in 20 isolates of Aspergillus spp.; A. niger (n = 3), A. flavus (n = 5), A. tamarii (n = 3), A. terreus (n = 3), A. tubingensis (n = 3), A. sydowii (n = 3). Aspergillus spp. were identified by sequencing the internal transcribed spacer (ITS) region. Extraction of melanin from culture filtrate and fungal biomass was done and followed by qualitative and quantitative analysis of melanin pigment. Ultraviolet (UV), Fourier transformed infrared (FT-IR), and electron paramagnetic resonance (EPR) spectra analyses confirmed the presence of melanin. The melanin pathway was studied by analyzing the effects of inhibitors; kojic acid, tropolone, phthalide, and tricyclazole. The results indicate that in A. niger and A. tubingensis melanin was found in both culture filtrate and fungal biomass. For A. tamarii and A. flavus melanin was extracted from biomass only, whereas melanin was found only in culture filtrate for A. terreus. A negligible amount of melanin was found in A. sydowii. The maximum amount of melanin from culture filtrate and fungal biomass was found in A. niger and A. tamarrii, respectively. The DOPA (3,4-dihydroxyphenylalanine) pathway produces melanin in A. niger, A. tamarii and A. flavus, whereas the DHN (1,8-dihydroxynaphthalene) pathway produces melanin in A. tubingensis and A. terreus. It can be concluded that the amount and type of melanin in aspergilli largely differ from species to species.

Epidemiological profile of fungal keratitis in Sfax (Tunisia)

Fungal keratitis is responsible for a significant burden of blinding disease in the developing world.

OBJECTIVE

The aim of this study was to determine the etiological agents, predisposing factors and therapy of keratomycosis in our region.

METHODS

Retrospective study of 60 patients with clinically and cultured confirmed fungi keratitis, who were attended at department of mycology in Sfax (1995 to 2012).

RESULTS

The mean age of patients was 47.2 years (sex ratio: 1.58). At least, one presumed predisposing factor was identified in 83.3% of cases. Corneal traumatism was established as the most common predisposing factor (61.6%) with vegetative matter (42.4%). Patients had corneal ulcer in 40% or abscess in 47.6%. All cases were positive on direct microscopy and 93% of cultures were positive. Filamentous fungi form the major etiologic agents (83%): Fusarium species (49% with F. solani [66%]), Aspergillus sp. (22%), Alternaria (5%), Scedosporium sp. (2%); and non-identified mold in (5%). Yeast were identified in 17% of cases. Topical agents were used in 97% of cases: ketoconazole 2%, amphotericin B (0.5%). Fluconazole per os was administrated for 11% of cases, itraconazole (2 cases) and voriconazole (one case). Keratoplasty was indicated for 27% of cases. The outcome was favorable in 16% of patients. Among the patients, 71% had persistent corneal deposit sequelae. Four patients lost the eyeball.

CONCLUSION

Corneal traumatism was the principal risk factor for fungal keratitis in young and middle-aged farmers. Fusarium solani is the predominant cause in Sfax. Early diagnosis, coupled with appropriate treatment, is crucial for increasing the chance of complete recovery.

A case of Beauveria bassiana keratitis confirmed by internal transcribed spacer and LSU rDNA D1-D2 sequencing

We describe a case of fungal keratitis due to Beauveria bassiana in a farmer with Fuchs' dystrophy, treated with amphotericin B. Surgery with penetrating keratoplasty was necessary to resolve the lesions. Susceptibility testing and molecular sequencing permitted the identification and treatment of this rare aetiological agent of invasive fungal disease.

[A case of mycotic keratitis due to Fusarium solani in Valdivia, Chile]

BACKGROUND

Keratomycosis is one of the most prevalent ophthalmic infections, which needs a specific treatment depending on the nature of the infecting fungus. The prognosis is usually severe and depends on an early diagnosis and suitable therapy.

CASE REPORT

We describe a case of keratitis due to Fusarium solani in a patient from a rural area, who, between May and October 2011, suffered a corneal trauma caused by dust particles in Valdivia, Chile. On two occasions, direct examination of eye scrapes revealed abundant septate hyphae. All cultures were positive for the same fungus, which was identified as Fusarium solani by phenotypic characterization and sequencing of ribosomal nuclear genes. The patient was initially treated with amphotericin B and afterwards successfully responded to a treatment with oral and intravenous voriconazole, although corneal opacity persisted.

CONCLUSIONS

Although keratomycosis in Chile is rare, its diagnostic particularities must be taken into consideration to establish the most effective treatment. Thus, a rapid visualization of the fungus in the lesion, an efficient isolation of the etiologic agent in pure culture is essential, as well as its rapid identification, which requires the use of molecular sequencing techniques in the case of Fusarium species.

Spectrum of fungal keratitis: clinicopathologic study of 44 cases

AIM

To determine the causative agents of fungal keratitis and study the predisposing factors over a period of ten years in a single tertiary care hospital.

METHODS

A retrospective analysis of fungal corneal ulcers was done from 2003-2012. Patients' clinical data were noted from the file records. Correlation of histopathological diagnosis was done with the report on fungal culture.

RESULTS

Mycotic keratitis was established in 44 cases by a positive fungal culture. Direct microscopic examination of potassium hydroxide (KOH) mounts revealed fungal elements in 39 cases while 40 cases showed fungus on Gram stained smears. Males (54.55%) were more commonly affected than the females (45.45%). The age ranged from 18 to 82 years. Most common age group to be involved was 41-60 years. Predisposing risk factors were seen in 34 (77.27%) cases. Most common findings on clinical examination were anterior chamber reaction and conjunctival injection seen in all the cases. Other common findings were stromal infiltration and hypopyon seen in 20 (45.45%) and 18 (40.91%) cases respectively. On histopathological examination the fungus was typed, as aspergillus in 34 cases while no definite typing was possible in 10 cases. The predominant isolate was aspergillus flavus (59.09%) followed by fusarium (15.91%). Mixed fungal and bacterial infection was seen in 3 (6.82%) cases.

CONCLUSION

Although culture is the gold standard for definitive diagnosis of fungal keratitis, direct microscopic examination of corneal scrapings or histomorphological evaluation of biopsies allow a rapid preliminary diagnosis. Early administration of antifungal treatment helps in preventing dreadful complications.

Canine keratomycosis in 11 dogs: a case series (2000-2011)

Keratomycosis is rarely reported in dogs. The purpose of this study was to review the signalment, clinical characteristics, predisposing factors, and outcome of 11 cases of canine keratomycosis. Medical records of included dogs were reviewed and follow-up information was obtained by re-examination of patients following their initial diagnosis. All 11 patients possessed predisposing factors for fungal keratitis, including an underlying endocrinopathy, pre-existing corneal disease, intraocular surgery, and/or prolonged use of either topical antibiotics or corticosteroids at the time of initial examination. Diagnostic techniques included corneal cytology demonstrating yeast or hyphae in 6 of 11 eyes, and fungal cultures with positive results in 7 of 11 eyes. Fungal organisms isolated included Cladosporium spp. (n = 1), Chrysosporium spp. (n = 1), Curvularia spp. (n = 2), Aspergillus spp. (n = 1), Penicillium spp. (n = 1), and Phialemonium spp. (n = 1). Of the 11 patients, 6 responded to medical management alone. Two resolved after a superficial keratectomy, and three were enucleated due to either endophthalmitis or progression of corneal disease. This study identified potential risk factors for developing fungal keratitis.

Calcineurin controls hyphal growth, virulence, and drug tolerance of Candida tropicalis

Candida tropicalis, a species closely related to Candida albicans, is an emerging fungal pathogen associated with high mortality rates of 40 to 70%. Like C. albicans and Candida dubliniensis, C. tropicalis is able to form germ tubes, pseudohyphae, and hyphae, but the genes involved in hyphal growth machinery and virulence remain unclear in C. tropicalis. Recently, echinocandin- and azole-resistant C. tropicalis isolates have frequently been isolated from various patients around the world, making treatment difficult. However, studies of the C. tropicalis genes involved in drug tolerance are limited. Here, we investigated the roles of calcineurin and its potential target, Crz1, for core stress responses and pathogenesis in C. tropicalis. We demonstrate that calcineurin and Crz1 are required for hyphal growth, micafungin tolerance, and virulence in a murine systemic infection model, while calcineurin but not Crz1 is essential for tolerance of azoles, caspofungin, anidulafungin, and cell wall-perturbing agents, suggesting that calcineurin has both Crz1-dependent and -independent functions in C. tropicalis. In addition, we found that calcineurin and Crz1 have opposite roles in controlling calcium tolerance. Calcineurin serves as a negative regulator, while Crz1 plays a positive role for calcium tolerance in C. tropicalis.

Factors affecting treatment outcomes with voriconazole in cases with fungal keratitis

PURPOSE

To report clinical experience with the use of voriconazole for management of cases with fungal keratitis and to evaluate the factors affecting treatment outcomes.

METHODS

Retrospective database review of all cases with fungal keratitis that were treated with topical voriconazole at the Royal Victorian Eye and Ear Hospital, Melbourne, Australia, between January 2003 and July 2010, was undertaken. Main parameters evaluated were clinical and microbiological profile of the cases, treatment, and final outcomes.

RESULTS

A total of 26 cases were treated with voriconazole eye drops during the study period. In addition, voriconazole was used in the form of oral tablets (n = 16, 61.5%), intracorneal injection (n = 7, 26.9%), and intracameral injection (n = 2, 7.7%). Overall, 50% (n = 13) of cases responded to medical treatment. Further definitive surgical intervention in the form of penetrating keratoplasty was required in 11 cases (42.3%). Two cases (7.7%) underwent enucleation for severe nonresolving keratitis. Nonresponders were more likely to have peripheral infiltrates (38.5% vs. 7.7%, P = 0.16) and hypopyon (61.5% vs. 23%, P = 0.11) as compared with responders. There was no significant variation in the microbiological results between responders and nonresponders.

CONCLUSIONS

Voriconazole was successful in the management of 50% cases of fungal keratitis in our study. Cases with peripheral infiltrates and hypopyon are less likely to respond to medical treatment.

Positively charged polymeric nanoparticle reservoirs of terbinafine hydrochloride: preclinical implications for controlled drug delivery in the aqueous humor of rabbits

Frequent instillation of terbinafine hydrochloride (T HCl) eye drops (0.25%, w/v) is necessary to maintain effective aqueous humor concentrations for treatment of fungal keratitis. The current approach aimed at developing potential positively charged controlled-release polymeric nanoparticles (NPs) of T HCl. The estimation of the drug pharmacokinetics in the aqueous humor following ocular instillation of the best-achieved NPs in rabbits was another goal. Eighteen drug-loaded (0.50%, w/v) formulae were fabricated by the nanopreciptation method using Eudragit® RS100 and chitosan (0.25%, 0.5%, and 1%, w/v). Soybean lecithin (1%, w/v) and Pluronic® F68 (0.5%, 1%, and 1.5%, w/v) were incorporated in the alcoholic and aqueous phases, respectively. The NPs were evaluated for particle size, zeta potential, entrapment efficiency percentage (EE%), morphological examination, drug release in simulated tear fluid (pH 7.4), Fourier-transform IR (FT-IR), X-ray diffraction (XRD), physical stability (2 months, 4°C and 25°C), and drug pharmacokinetics in the rabbit aqueous humor relative to an oily drug solution. Spherical, discrete NPs were successfully developed with mean particle size and zeta potential ranging from 73.29 to 320.15 nm and +20.51 to +40.32 mV, respectively. Higher EE% were achieved with Eudragit® RS100-based NPs. The duration of drug release was extended to more than 8 h. FT-IR and XRD revealed compatibility between inactive formulation ingredients and T HCl and permanence of the latter's crystallinity, respectively. The NPs were physically stable, for at least 2 months, when refrigerated. F5-NP suspension significantly (P<0.05) increased drug mean residence time and improved its ocular bioavailability; 1.657-fold.

LC-MS/MS assay for the determination of natamycin in rabbit and human plasma: Application to a pharmacokinetics and protein binding study

To enable reliable quantification of natamycin in rabbit and human plasma, a validated, sensitive and selective liquid chromatography–tandem mass spectrometry assay was developed. The chromatographic separation was achieved isocratically on a Cyano column using methanol: aqueous 3.5 mM ammonium acetate (pH 4) (90:10 v/v). The assay was validated over a concentration range of 6.25–400 ng/mL with lower limit of detection of 3.12 ng/mL. Quantification was performed using the transitions 664.5→137.2m/z for natamycin and 923.5→183.4m/z for the IS. The method was validated with respect to linearity, accuracy, precision, recovery and stability. This assay has been successfully applied to a pharmacokinetic study of natamycin in NZ rabbit and plasma protein binding in human plasma.

Diversity of microbial species implicated in keratitis: a review

Background:

Microbial keratitis is an infectious disease of the cornea characterised by inflammation and is considered an ophthalmic emergency requiring immediate attention. While a variety of pathogenic microbes associated with microbial keratitis have been identified, a comprehensive review identifying the diversity of species has not been completed.

Methods:

A search of peer-reviewed publications including case reports and research articles reporting microorganims implicated in keratitis was conducted. Search engines including PubMed, Scopus and Web of Science with years ranging from 1950-2012 were used.

Results:

232 different species from 142 genera, representing 80 families were found to be implicated in microbial keratitis. Fungi exhibited the largest diversity with 144 species from 92 genera. In comparison, 77 species of bacteria from 42 genera, 12 species of protozoa from 4 genera and 4 types of virus were identified as the infectious agents. A comparison of their aetiologies shows reports of similarities between genera.

Conclusions:

The diversity of microbial species implicated in keratitis has not previously been reported and is considerably greater than suggested by incidence studies. Effective treatment is heavily reliant upon correct identification of the responsible microorganisms. Species identification, the risk factors associated with, and pathogenesis of microbial keratitis will allow the development of improved therapies. This review provides a resource for clinicians and researchers to assist in identification and readily source treatment information.

A highly sensitive method for molecular diagnosis of fungal keratitis: a dot hybridization assay

PURPOSE

Fungal keratitis (FK) is an important cause of ocular morbidity, especially for people living in the agricultural communities of the developing world. Current diagnostic methods may lack sensitivity (direct microscopy) or are time consuming (culture). The aim of this study was to develop a dot hybridization assay for sensitive and rapid diagnosis of FK.

DESIGN

Evaluation of diagnostic test or technology.

PARTICIPANTS AND CONTROLS

Fifty corneal scrapes (49 patients) from consecutive cases of clinically suspected microbial keratitis were analyzed prospectively.

METHODS

Molecular detection of fungi in the scrapes was performed by amplification of the internal transcribed spacer region (ITS) that contained the target gene (5.8S rRNA gene) by polymerase chain reaction (PCR), followed by hybridization of the PCR product to a fungus-specific oligonucleotide probe immobilized on a nylon membrane. The results were compared with those obtained by gram-stain microscopy, culture, and gel electrophoresis of the PCR products. Discrepant results were resolved by cloning and resequencing of the amplified ITS fragments.

MAIN OUTCOME MEASURES

Performance of the dot hybridization assay, including sensitivity, specificity, and positive and negative predictive values, was evaluated.

RESULTS

Ten scrapes demonstrated positive results by both the dot hybridization assay and culture. However, 11 scrapes demonstrated positive results by the dot hybridization assay, but demonstrated negative results by culture, and 10 of the 11 samples were considered to be positive for FK by cloning and resequencing of the amplified ITS fragment and by a pathologic examination or clinical course review. The sensitivities for diagnosis of FK by the dot hybridization assay and culture were 100% and 50%, respectively, whereas the specificities were 96.7% and 100%, respectively.

CONCLUSIONS

The dot hybridization assay is a highly sensitive and specific diagnostic tool for FK. The method provides a much higher sensitivity than that of culture (100% vs. 50%; P<0.001). The hybridization procedure can be finished within a working day. It is expected that the method can have an impact on the diagnosis and treatment of FK in the future.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.