Differences in clinical outcomes in keratitis due to fungus and bacteria

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.

Corneal Transplantation for Infectious Keratitis: A Prospective Dutch Registry Study

PURPOSE

The aim of this study was to analyze real-world practice patterns and graft survival after corneal transplantation for infectious keratitis in the Netherlands.

METHODS

All consecutive keratoplasties for infectious keratitis registered in the Netherlands Organ Transplant Registry were included. Graft survival was analyzed using Kaplan-Meier survival curves with Cox regression to compare the 3 most common pathogens with subgroup analysis for type and reason of transplantation, sex, and graft size. Multivariable analysis was performed using the same explanatory factors.

RESULTS

Between 2007 and 2017, 1111 keratoplasties for infectious keratitis were registered in the Netherlands Organ Transplant Registry. The most common pathogens were viruses (n = 437), bacteria (n = 271), and Acanthamoeba (n = 121). Human leukocyte antigen (HLA) matching did not provide a significant survival benefit, whereas emergency procedures showed worse graft survival [hazard ratio (HR) = 0.40, P = 0.120; HR = 2.73, P < 0.001, respectively]. Graft size >8.5 mm was significantly worse than graft size 8.5 mm (HR = 2.062, P = 0.010). In therapeutic keratoplasty, graft survival was significantly worse for Acanthamoeba than viral keratitis (HR = 2.36, P = 0.008). In the multivariable model, adjusting for graft size, type, and reason for transplantation, viral and bacterial keratitis did not differ significantly in graft survival, and Acanthamoeba showed a significantly worse prognosis (vs. viral keratitis, HR = 2.30, P < 0.001; bacterial keratitis, HR = 2.65, P < 0.001).

CONCLUSIONS

Viral keratitis was the most common indication for transplantation, followed by bacterial and Acanthamoeba keratitis. HLA matching did not offer protection over elective non-HLA-matched procedures, whereas emergency procedures and grafts sized >8.5 mm showed poor survival. In optical keratoplasty, survival is high for all pathogens, whereas in therapeutic keratoplasty Acanthamoeba shows poor outcome.

Rapid Point-of-Care Identification of Aspergillus Species in Microbial Keratitis

Importance

Microbial keratitis (MK) is a common cause of unilateral visual impairment, blindness, and eye loss in low-income and middle-income countries. There is an urgent need to develop and implement rapid and simple point-of-care diagnostics for MK to increase the likelihood of good outcomes.

Objective

To evaluate the diagnostic performance of the Aspergillus-specific lateral-flow device (AspLFD) to identify Aspergillus species causing MK in corneal scrape and corneal swab samples of patients presenting with microbial keratitis.

Design, Setting, and Participants

This diagnostic study was conducted between May 2022 and January 2023 at the corneal clinic of Aravind Eye Hospital in Madurai, Tamil Nadu, India. All study participants were recruited during their first presentation to the clinic. Patients aged 15 years or older met the eligibility criteria if they were attending their first appointment, had a corneal ulcer that was suggestive of a bacterial or fungal infection, and were about to undergo diagnostic scrape and culture.

Main Outcomes and Measures

Sensitivity and specificity of the AspLFD with corneal samples collected from patients with MK. During routine diagnostic scraping, a minimally invasive corneal swab and an additional corneal scrape were collected and transferred to aliquots of sample buffer and analyzed by lateral-flow device (LFD) if the patient met the inclusion criteria. Photographs of devices were taken with a smartphone and analyzed using a ratiometric approach, which was developed for this study. The AspLFD results were compared with culture reports.

Results

The 198 participants who met the inclusion criteria had a mean (range) age of 51 (15-85) years and included 126 males (63.6%). Overall, 35 of 198 participants with corneal scrape (17.7%) and 17 of 40 participants with swab samples (42.5%) had positive culture results for Aspergillus species. Ratiometric analysis results for the scrape samples found that the AspLFD achieved high sensitivity (0.89; 95% CI, 0.74-0.95), high negative predictive value (0.97; 95% CI, 0.94-0.99), low negative likelihood ratio (0.12; 95% CI, 0.05-0.30), and an accuracy of 0.94 (95% CI, 0.90-0.97). Ratiometric analysis results for the swab samples showed that the AspLFD had high sensitivity (0.94; 95% CI, 0.73-1.00), high negative predictive value (0.95; 95% CI, 0.76-1.00), low negative likelihood ratio (0.07; 95% CI, 0.01-0.48), and an accuracy of 0.88 (95% CI, 0.73-0.96).

Conclusions and Relevance

Results of this diagnostic study suggest that AspLFD along with the ratiometric analysis of LFDs developed for this study has high diagnostic accuracy in identifying Aspergillus species from corneal scrapes and swabs. This technology is an important step toward the provision of point-of-care diagnostics for MK and could inform the clinical management strategy.

Oxidative Stress Initiates Receptor-Interacting Protein Kinase-3/Mixed Lineage Kinase Domain-Like-Mediated Corneal Epithelial Necroptosis and Nucleotide-Binding Oligomerization Domain-Like Receptor Protein 3 Inflammasome Signaling during Fungal Keratitis

Fungal keratitis remains a major cause of severe visual loss in developing countries because of limited choices of therapy. The progression of fungal keratitis is a race between the innate immune system and the outgrowth of fungal conidia. Programmed necrosis (necroptosis), a type of proinflammatory cell death, has been recognized as a critical pathologic change in several diseases. However, the role and potential regulatory mechanisms of necroptosis have not been investigated in corneal diseases. The current study showed, for the first time, that fungal infection triggered significant corneal epithelial necroptosis in human/mouse/in vitro models. Moreover, a reduction in excessive reactive oxygen species release effectively prevented necroptosis. NLRP3 knockout did not affect necroptosis in vivo. In contrast, ablation of necroptosis via RIPK3 knockout significantly delayed migration and inhibited the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in macrophages, which enhanced the progression of fungal keratitis. Taking these findings together, the study indicated that overproduction of reactive oxygen species in fungal keratitis leads to significant necroptosis in the corneal epithelium. Furthermore, the necroptotic stimuli-mediated NLRP3 inflammasome serves as a driving force in host defense against fungal infection.

Oral voriconazole monotherapy for fungal keratitis: efficacy, safety, and factors associated with outcomes

Purpose

To provide preliminary data on the efficacy and safety of oral voriconazole (VCZ) as a primary treatment for fungal keratitis (FK).

Method

We performed a retrospective histopathological analysis of data on 90 patients with FK at The First Affiliated Hospital of Guangxi Medical University between September 2018 and February 2022. We recorded three outcomes: corneal epithelial healing, visual acuity (VA) improvement, and corneal perforation. Independent predictors were identified using univariate analysis, and multivariate logistic regression analysis was used to identify independent predictive factors associated with the three outcomes. The area under the curve was used to evaluate the predictive value of these factors.

Results

Ninety patients were treated with VCZ tablets as the only antifungal drug. Overall, 71.1% (n = 64) of the patients had extreme corneal epithelial healing, 56.7% (n = 51) showed an improvement in VA, and 14.4% (n = 13) developed perforation during treatment. Non-cured patients were more likely to have large ulcers (≥5 × 5 mm²) and hypopyon.

Conclusion

The results indicated that oral VCZ monotherapy was successful in the patients with FK in our study. Patients with ulcers larger than 5 × 5 mm² and hypopyon were less likely to respond to this treatment.

The Case for Fungal Keratitis to Be Accepted as a Neglected Tropical Disease

Amongst the treatable cause of blindness among young people, fungal keratitis ranks high. There are an estimated 1,051,787 to 1,480,916 eyes affected annually, with 8–11% of patients having to have the eye removed. Diagnosis requires a corneal scraping, direct microscopy and fungal culture with a large number of airborne fungi implicated. Treatment involves the intensive application of antifungal eye drops, preferably natamycin, often combined with surgery. In low-resource settings, inappropriate corticosteroid eye drops, ineffective antibacterial therapy, diagnostic delay or no diagnosis all contribute to poor ocular outcomes with blindness (unilateral or bilateral) common. Modern detailed guidelines on fungal keratitis diagnosis and management are lacking. Here, we argue that fungal keratitis should be included as a neglected tropical disease, which would facilitate greater awareness of the condition, improved diagnostic capability, and access to affordable antifungal eye medicine.

Profiling of the Conjunctival Bacterial Microbiota Reveals the Feasibility of Utilizing a Microbiome-Based Machine Learning Model to Differentially Diagnose Microbial Keratitis and the Core Components of the Conjunctival Bacterial Interaction Network

Both healthy and diseased human ocular surfaces possess their own microbiota. If allowed, opportunistic pathogens within the ocular microbiota may cause microbial keratitis (MK). However, the nonpathogenic component of the ocular microbiota has been proven to undermine the performance of culture, the gold standard of the etiological diagnosis for MK. As the conjunctival bacterial microbiota generates unique alterations with various oculopathies, this study aimed to evaluate the feasibility of distinguishing MK using machine learning based on the characteristics of the conjunctival bacterial microbiome associated with various types of MK. This study also aimed to reveal which bacterial genera constitute the core of the interaction network of the conjunctival bacterial microbiome. Conjunctival swabs collected from the diseased eyes of MK patients and the randomly chosen normal eyes of healthy volunteers were subjected for high-throughput 16S rDNA sequencing. The relative content of each bacterial genus and the composition of bacterial gene functions in every sample were used to establish identification models with the random forest algorithm. Tenfold cross validation was adopted. Accuracy was 96.25% using the bacterial microbiota structure and 93.75% using the bacterial gene functional composition. Therefore, machine learning with the conjunctival bacterial microbiome characteristics might be used for differentiation of MKs as a noninvasive supplementary approach. In addition, this study found that Actinobacteria, Lactobacillus, Clostridium, Helicobacter, and Sphingomonas constitute the core of the interaction network of the conjunctival bacterial microbiome.

Thermosensitive Tri-Block Polymer Nanoparticle-Hydrogel Composites as Payloads of Natamycin for Antifungal Therapy Against Fusarium Solani

Purpose

Fusarium Solani is the principal pathogen associated with fungal keratitis. As a sensitive drug to F. Solani, natamycin (NAT) was limited by the poor penetration and low bioavailability in clinical application. The aim of this study was to develop a new type of tri-block polymer nanoparticle-gel complex (Gel@PLGA-PEI-PEG@NAT) for delivering NAT and evaluate its physicochemical properties, antifungal activity, safety, penetrability, adhesion, and efficacy in treating fungal keratitis.

Methods

PLGA-PEI-PEG@NAT was prepared and characterized with a nano-particle size analyzer, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The minimum inhibitory concentration (MIC), cytotoxicity, penetrability of NAT (Natacyn^® 5% ophthalmic suspension; Alcon) and PLGA-PEI-PEG@NAT with different concentrations were assessed. The eye surface retention time, ocular irritation, and curative effect of the NAT ophthalmic suspension and Gel@PLGA-PEI-PEG@NAT on a rabbit fungal keratitis model were evaluated.

Results

PLGA-PEI-PEG@NAT had a particle size of 150 nm, a positive surface charge, and a sustained-release effect. The MIC for F. Solani was 2 μg/mL. A cytotoxicity test and ocular irritation test showed that PLGA-PEI-PEG@NAT and Gel@PLGA-PEI-PEG@NAT had good biocompatibility and no obvious irritation for rabbit corneas. Penetration experiments confirmed that PLGA-PEI-PEG@NAT can successfully enter corneal epithelial cells and through the cornea to enter the anterior chamber. Compared with NAT ophthalmic suspension, Gel@PLGA-PEI-PEG@NAT had stronger cornea permeation at the same concentration. The therapeutic effect and precorneal retention ability of the NAT ophthalmic suspension and Gel@PLGA-PEI-PEG@NAT on the fungal keratitis rabbit model were compared. Gel@PLGA-PEI-PEG@NAT achieved a better therapeutic effect at a lower drug concentration, and its eye surface retention time was significantly longer than that of the NAT ophthalmic suspension.

Conclusion

Gel@PLGA-PEI-PEG@NAT was shown to be a safe and effective nanodrug delivery system for NAT. It has great potential to improve the cure rate of fungal keratitis, reduce the administration frequency during the treatment process, and improve patient compliance.

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

PURPOSE

To evaluate baseline characteristics, microbiological spectrum, management, and outcomes of patients with culture-proven fungal keratitis.

METHODS

Retrospective review of all patients with culture-proven fungal keratitis seen over 6 years at a tertiary referral center.

RESULTS

The present study included 62 eyes from 62 patients. Infection with filamentous organisms was more common than with yeast (66.1% vs 27.4%). The most common filamentous organisms were Fusarium (17.7%) and Aspergillus (16.1%), while the most common yeast was Candida (24.2%). The main predisposing factor for filamentous keratitis was contact lens use. Yeast keratitis is most associated with an immunocompromised host and ocular surface disease. Corneal perforation (20.0%) and surgical interventions (46.8%) were common, with 27.4% of eyes requiring at least one penetrating keratoplasty. Filamentous keratitis is more likely than yeast keratitis to require urgent penetrating keratoplasty or enucleation and to receive more than one topical and systemic antifungal agent. Visual outcomes were poor with nearly half of the eyes remaining at 20/200 or worse upon resolution of infection. Worse visual outcomes were associated with poor vision at presentation and a history of ocular surface disease. Antifungal susceptibility testing was not routinely performed, but it demonstrated a relatively high minimum inhibitory concentration for at least one antifungal drug in 90% of cases when performed (16.1%) and guided the direction of treatment for 80% of the cases.

CONCLUSION

Fungal keratitis is visually devastating. Infections with filamentous fungi predominated over yeast and were generally treated more aggressively both medically and surgically. Filamentous and yeast keratitis had similar durations of infections and visual outcomes. Antifungal susceptibility testing influenced treatment in 80% of cases in which it was performed.

Clinical Characteristics and Outcomes of Fungal Keratitis in the United Kingdom 2011-2020: A 10-Year Study

Fungal keratitis (FK) is a serious ocular infection that often poses significant diagnostic and therapeutic dilemmas. This study aimed to examine the causes, clinical characteristics, outcomes, and prognostic factors of FK in the UK. All culture-positive and culture-negative presumed FK (with complete data) that presented to Queen’s Medical Centre, Nottingham, and the Queen Victoria Hospital, East Grinstead, between 2011 and 2020 were included. We included 117 patients (n = 117 eyes) with FK in this study. The mean age was 59.0 ± 19.6 years (range, 4–92 years) and 51.3% of patients were female. Fifty-three fungal isolates were identified from 52 (44.4%) culture-positive cases, with Candida spp. (33, 62.3%), Fusarium spp. (9, 17.0%), and Aspergillus spp. (5, 9.4%) being the most common organisms. Ocular surface disease (60, 51.3%), prior corneal surgery (44, 37.6%), and systemic immunosuppression (42, 35.9%) were the three most common risk factors. Hospitalisation for intensive treatment was required for 95 (81.2%) patients, with a duration of 18.9 ± 16.3 days. Sixty-six (56.4%) patients required additional surgical interventions for eradicating the infection. Emergency therapeutic/tectonic keratoplasty was performed in 29 (24.8%) cases, though 13 (44.8%) of them failed at final follow-up. The final corrected-distance-visual-acuity (CDVA) was 1.67 ± 1.08 logMAR. Multivariable logistic regression analyses demonstrated increased age, large infiltrate size (>3 mm), and poor presenting CDVA (<1.0 logMAR) as significant negative predictive factors for poor visual outcome (CDVA of <1.0 logMAR) and poor corneal healing (>60 days of healing time or occurrence of corneal perforation requiring emergency keratoplasty; all p < 0.05). In conclusion, FK represents a difficult-to-treat ocular infection that often results in poor visual outcomes, with a high need for surgical interventions. Innovative treatment strategies are urgently required to tackle this unmet need.

Impact of COVID-19 Pandemic on Infectious Keratitis Outcomes: A Retrospective Multicenter Study in Tertiary Eye Hospitals of South India

PURPOSE

The purpose of this study was to report the adverse effects of the COVID-19 pandemic on the clinical outcomes of infectious keratitis in South India.

METHODS

Two hundred fifty-eight patients presented with infectious keratitis at 6 tertiary care centers when strict travel restrictions were in place from March 24 to May 31, 2020. Case records were collected retrospectively and analyzed for demographics, type of initial treatment, length of delay in presentation, microbiological diagnosis, clinical course, and final treatment outcome.

RESULTS

The mean age of the patients was 49.2 years, with most of them (61.2%) being male. Forty-one patients (15.9%) did not receive any treatment for at least a week after the onset of symptoms. One hundred eight patients (41.9%) presented with severe ulcer (32 had a frank perforation). Resolution of the infection was achieved only in 103 patients (45.6%). A total of 90 patients (39.8%) with ulcers had a perforation, yet only 29 patients (32.2%) could receive keratoplasty because of the unavailability of donor tissues. At the end of 6-month follow-up, 47 patients had anatomical failure (loss of globe) and 12 additional patients had functional failure (total permanent vision loss).

CONCLUSIONS

Delay in presentation and acute shortage of donor corneal tissues for emergency keratoplasty because of the COVID-19 pandemic had a grave impact, resulting in irreversible blindness in a significant number of patients.

Update on the management of fungal keratitis

PURPOSE

The aim of this article is to introduce the recent advance on the studies of fungal keratitis published over past 5 years.

METHODS

We performed literature review of articles published on PubMed, Google Scholar, CNKI and Web of Science relevant to the diagnosis, pathogenesis and novel treatment of fungal keratitis.

RESULTS

Excessive inflammation can lead to stromal damage and corneal opacification, hence the research on immune mechanism provides many potential therapeutic targets for fungal keratitis. Many researchers discussed the importance of earlier definitive diagnosis and were trying to find rapid and accurate diagnostic methods of pathogens. Develop new drug delivery systems and new routes of administration with better corneal penetration, prolonged ocular residence time, and better mucoadhesive properties is also one of the research hotspots. Additionally, many novel therapeutic agents and methods have been gradually applied in clinical ophthalmology.

CONCLUSION

The diagnosis and treatment of fungal keratitis are still a challenge for ophthalmologist, and many researches provide new methods to conquer these problems.

Fungal Keratitis in the Egyptian Delta: Epidemiology, Risk Factors, and Microbiological Diagnosis

Purpose: The current study evaluates the epidemiological characteristics, risk factors, and microbiological diagnosis of fungal keratitis among patients living in the Egyptian Delta.Methods: This is a prospective hospital-based study that included patients who were clinically diagnosed and confirmed by culture test to have fungal keratitis. Patients were examined at baseline and risk factors were identified and collected. Patients were followed over 6 months and the outcomes were documented.Results: A total of 171 (67%) of 252 microbial keratitis patients was proved fungal by microbial culture test. Rural residence and agricultural activity were reported in 139 (81.3%) and 85 (49.7%) patients, respectively. Patients presented within 1 week from the start of symptoms were 120 (70.2%). A total of 54 (31.6%) patients reported ocular trauma. Forty patients (23.4%) had prior ocular surgery and 43 (25.1%) patients had a history of previous ocular disorders. Aspergillus species was the most common organism found in 120 (70.17%) patients, followed by Dematiceous fungi that were found in 25 (14.6%) patients. The main outcome was corneal opacity in 132 (77.2%) patients following medical treatment.Conclusion: Filamentary fungal predominance in Mansoura is influenced by the rural residence of its population. Therefore, more efforts in spreading awareness about microbial keratitis among villagers are important to reduce blindness caused by corneal opacity in rural areas.

First report of a new corneal pathogen: Phaeoacremonium parasiticum

Keratitis is a public health issue in developing countries and a potentially sight-threatening condition. Collagen fibrils in the corneal stroma are parallels to each other. Fundamental substance maintains the same space between collagen fibrils. That is how corneal transparency can be achieved. Any damage which can modify this structure will lead to corneal opacity and loss of vision. Fungal keratitis might appear in up to one-third of cases. Nevertheless, fungal keratitis remains poorly described and understood. Herein, we present the first ever reported case of corneal infection due to Phaeoacremonium parasiticum in a young patient. We describe the clinical and microbial characteristics, and we also discuss the use of confocal microscopy in early diagnosis of this infection.

The role of fungi in fungal keratitis

Fungal keratitis (FK) accounts for approximately half of the microbial keratitis encountered in low middle income countries (LMICs) and predominantly affect the working rural-poor. FK causes significant morbidity with the majority of patients left with moderate or worse visual impairment and approximately 25% requiring expensive and often unsuccessful surgical interventions. The severity of FK and the resultant corneal damage or resolution can be attributed to i) the virulence and bioburden of the fungal pathogen, ii) the host defense mechanism and immune response and iii) sub-optimal diagnostics and anti-fungal treatment strategies. This review provides a comprehensive overview of the multifaceted components that drive FK progression and resolution, highlighting where knowledge gaps exist and areas that warrant further research.

CRISPR/Cas9-Mediated Gene Replacement in the Fungal Keratitis Pathogen Fusarium solani var. petroliphilum

Fungal keratitis (FK) is a site-threatening infection of the cornea associated with ocular trauma and contact lens wear. Members of the Fusarium solani species complex (FSSC) are predominant agents of FK worldwide, but genes that support their corneal virulence are poorly understood. As a means to bolster genetic analysis in FSSC pathogens, we sought to employ a CRISPR/Cas9 system in an FK isolate identified as Fusarium petroliphilum. Briefly, this approach involves the introduction of two components into fungal protoplasts: (1) A purified Cas9 protein complexed with guide RNAs that will direct the ribonuclease to cut on either side of the gene of interest, and (2) a “repair template” comprised of a hygromycin resistance cassette flanked by 40 bp of homology outside of the Cas9 cuts. In this way, Cas9-induced double strand breaks should potentiate double homologous replacement of the repair template at the desired locus. We targeted a putative ura3 ortholog since its deletion would result in an easily discernable uracil auxotrophy. Indeed, 10% of hygromycin-resistant transformants displayed the auxotrophic phenotype, all of which harbored the expected ura3 gene deletion. By contrast, none of the transformants from the repair template control (i.e., no Cas9) displayed the auxotrophic phenotype, indicating that Cas9 cutting was indeed required to promote homologous integration. Taken together, these data demonstrate that the in vitro Cas9 system is an easy and efficient approach for reverse genetics in FSSC organisms, including clinical isolates, which should enhance virulence research in these important but understudied ocular pathogens.

Visual Impairment in Fungal Versus Bacterial Corneal Ulcers 4 Years After Successful Antimicrobial Treatment

PURPOSE

To compare longitudinal outcomes of visual acuity after fungal corneal ulcers with those of bacterial ulcers.

DESIGN

Prospective cohort study.

METHODS

This study was conducted in a tertiary eye hospital in South India. The population consisted of 100 of 152 individuals whose fungal or bacterial keratitis had been diagnosed 4 years prior and had been enrolled in 1 of 2 concurrent randomized trials. Causative organisms of infectious keratitis were either bacterial or fungal. Presenting visual acuity consisted of best spectacle corrected visual acuity (BSCVA) and hard contact lens-corrected visual acuity (CLVA).

RESULTS

Fifty study participants with prior fungal keratitis and 50 with prior bacterial keratitis were enrolled. Four years after treatment for keratitis, participants' presenting vision in the better eye was worse than 20/60 for 12 individuals (24.0%) in the fungal group and 10 individuals (20.0%) in the bacterial group. Median BSCVA in the affected eye at the 4-year visit in the fungal group was similar to that in the bacterial group (Snellen equivalent, 20/32 for each), although vision worse than 20/400 was more common in the fungal ulcer group after spectacle correction (odds ratio [OR] 4.19; 95% confidence interval [CI], 1.11-15.8) and contact lens correction (OR, 5.74; 95% CI, 1.37-24.1).

CONCLUSIONS

In this South Indian population with a previous episode of fungal or bacterial keratitis, correctable bilateral visual impairment was common. Although long-term visual outcomes were, on average, similar between fungal and bacterial ulcers, fungal ulcers were more likely to produce severe visual impairment.

Quantitative profiling of tear proteome reveals down regulation of zinc alpha-2 glycoprotein in Aspergillus flavus keratitis patients

Corneal mycotic ulceration is predominantly due to Aspergillus and Fusarium solani infection in tropical countries. In this study, we examined the proteome profile of tear samples from A. flavus keratitis patients at various stages of infection. The proteome was profiled using 2D PAGE and the protein levels were quantified using 2D DIGE. Alpha-1-antitrypsin, apolipoprotein, haptoglobin, lactoferrin and albumin were up regulated while cystatin SA III precursor, lacrimal lipocalin precursor, lacritin precursor and Zinc alpha-2 glycoprotein (ZAG) were down regulated in tear fluid. In the case of ZAG all proteoforms were down regulated as the disease progressed from early to late stage of infection. Western blot analysis confirmed the results observed using DIGE. Further, there were no gender specific differences in the levels of ZAG expression in keratitis patient tear film. Published results show up regulation of ZAG in Fusarium keratitis patient tear indicating subtle changes in the early events of host response to these two fungal pathogens. We conclude that ZAG level could be used as an indicator of A. flavus or F. solani infection, even during the early stage of the disease.

Evaluation of corneal cross-linking as adjuvant therapy for the management of fungal keratitis

PURPOSE

To evaluate the efficacy of corneal cross-linking (CXL) as adjuvant therapy for the treatment of fungal ulcerative keratitis.

METHODS

Forty-one patients with fungal ulcerative keratitis were recruited and assigned into two randomized controlled groups. These groups were treated with CXL combined with antifungal medications (CXL-M) or antifungal medications alone (M). The ulcers were assessed by slit-lamp biomicroscopy, slit-lamp images, in vivo confocal microscopy (IVCM), and anterior segment optical coherence tomography (AS-OCT). The patients were followed up before surgery/first visit (FV), 1 day after surgery, 1 and 2 weeks, and 1, 2, 3, 4, 5, and 6 months after surgery/FV.

RESULTS

In the cured patients, the area of corneal ulcers, the duration of ulcer healing, the time to non-observed fungal hyphae by IVCM, the number of antifungal medications, the frequency of administered medications, and the maximum ulcer depth decreased significantly after CXL (all P < 0.05) compared with the M group. There were no significant differences in either corneal thickness or epithelial thickness of ulcers after healing between 5 and 6 months after surgery in the CXL-M group, while these were increased significantly at 6 months compared with 5 months after FV in the M group (both P < 0.05).

CONCLUSIONS

In our study, CXL accelerated healing of the fungal ulcers, shortened the treatment duration, and minimized the need for medications and surgery. It appears that CXL is an effective procedure and adjuvant therapy for managing fungal keratitis.

Predicting factors and prediction model for discriminating between fungal infection and bacterial infection in severe microbial keratitis

A retrospective medical record review including 344 patients who were admitted with severe microbial keratitis at Ramathibodi Hospital, Bangkok, Thailand, from January 2010 to December 2016 was conducted. Causative organisms were identified in 136 patients based on positive culture results, pathological reports and confocal microscopy findings. Eighty-six eyes (63.24%) were bacterial keratitis, while 50 eyes (36.76%) were fungal keratitis. Demographics, clinical history, and clinical findings from slit-lamp examinations were collected. We found statistically significant differences between fungal and bacterial infections in terms of age, occupation, contact lens use, underlying ocular surface diseases, previous ocular surgery, referral status, and duration since onset (p < 0.05). For clinical features, depth of lesions, feathery edge, satellite lesions and presence of endothelial plaque were significantly higher in fungal infection compared to bacterial infection with odds ratios of 2.97 (95%CI 1.43–6.15), 3.92 (95%CI 1.62–9.45), 6.27 (95%CI 2.26–17.41) and 8.00 (95%CI 3.45–18.59), respectively. After multivariate analysis of all factors, there were 7 factors including occupation, history of trauma, duration since onset, depth of lesion, satellite lesions, endothelial plaque and stromal melting that showed statistical significance at p < 0.05. We constructed the prediction model based on these 7 identified factors. The model demonstrated a favorable receiver operating characteristic curve (ROC = 0.79, 95%CI 0.72–0.86) with correct classification, sensitivity and specificity of 81.48%, 70% and 88.24%, respectively at the optimal cut-off point. In conclusion, we propose potential prediction factors and prediction model as an adjunctive tool for clinicians to rapidly differentiate fungal infection from bacterial infection in severe microbial keratitis patients.

Solutol HS15 based binary mixed micelles with penetration enhancers for augmented corneal delivery of sertaconazole nitrate: optimization, in vitro, ex vivo and in vivo characterization

Keratomycosis is a serious corneal disease that can cause a permanent visual disability if not treated effectively. Sertaconazole nitrate (STZ), a novel broad spectrum antifungal drug, was suggested as a promising treatment. However, its utility in the ocular route is restricted by its poor solubility, along with other problems facing the ocular delivery like short residence time, and the existing corneal barrier. Therefore, the objective of this study was to formulate STZ loaded binary mixed micelles (STZ-MMs) enriched with different penetration enhancers using thin-film hydration method, based on a 3¹.2² mixed factorial design. Different formulation variables were examined, namely, type of auxiliary surfactant, type of penetration enhancer, and total surfactants: drug ratio, and their effects on the solubility of STZ in MMs (S_M), particle size (PS), polydispersity index (PDI), and zeta potential (ZP) were evaluated. STZ-MMs enhanced STZ aqueous solubility up to 338.82-fold compared to free STZ. Two optimized formulations (MM-8 and MM-11) based on the desirability factor (0.891 and 0.866) were selected by Design expert^® software for further investigations. The optimized formulations were imaged by TEM which revealed nanosized spherical micelles. Moreover, they were examined for corneal mucoadhesion, stability upon dilution, storage effect, and ex vivo corneal permeation studies. Finally, both in vivo corneal uptake and in vivo corneal tolerance were investigated. MM-8 showed superiority in the ex vivo and in vivo permeation studies when compared to the STZ-suspension. The obtained results suggest that the aforementioned STZ loaded mixed micellar system could be an effective candidate for Keratomycosis-targeted therapy.

Corneal Collagen Cross-Linking for the Management of Mycotic Keratitis

PURPOSE

To evaluate the efficiency of corneal collagen cross-linking (CXL) in addition to topical voriconazole in cases with mycotic keratitis.

DESIGN

Retrospective case series in a tertiary university hospital.

PARTICIPANTS

CXL was performed on 13 patients with mycotic keratitis who presented poor or no response to topical voriconazole treatment.

METHODS

The clinical features, symptoms, treatment results and complications were recorded retrospectively. The corneal infection was graded according to the depth of infection into the stroma (from grade 1 to grade 3). The visual analogue scale was used to calculate the pain score before and 2 days after surgery.

MAIN OUTCOME MEASURES

Grade of the corneal infection.

RESULTS

Mean age of 13 patients (6 female and 7 male) was 42.4 ± 17.7 years (20-74 years). Fungus was demonstrated in culture (eight patients) or cytological examination (five patients). Seven of the 13 patients (54%) were healed with topical voriconazole and CXL adjuvant treatment in 26 ± 10 days (15-40 days). The remaining six patients did not respond to CXL treatment; they initially presented with higher grade ulcers. Pre- and post-operative pain score values were 8 ± 0.8 and 3.5 ± 1, respectively (p < 0.05).

CONCLUSIONS

The current study suggests that adjunctive CXL treatment is effective in patients with small and superficial mycotic ulcers. These observations require further research by large randomized clinical trials.

Fungal keratitis: The Aravind experience

Research becomes very significant and meaningful when it addresses a significant public health problem of a region. Fungal keratitis is a serious problem affecting the agrarian poor and hence requires attention from public health specialists. The approach to a public health issue should focus not only on treatment but also prevention or at least show a significant thrust to reduce the morbidity of the problem. At our institution, we have developed a special interest in fungal keratitis and tried to study it in a multitude of aspects. As we put the pieces of the puzzle together, we believe that interest will be rekindled among policymakers, clinicians, microbiologists, pharmaceutical industry, and basic scientists to work together to join forces and take up an integrative approach to managing this problem. It is also believed that the article underscores the need and importance of having a focused approach to ensuring a successful career in clinical research.

Fungal Keratitis Associated With Airborne Organic Debris and Soft Contacts Lenses: Case Reports and Review of the Literature

OBJECTIVES

To report two cases of fungal keratitis in soft contact lens wearers who were exposed to environmental mold.

METHODS

Case reports, with review of the relevant literature.

RESULTS

Two otherwise healthy middle-aged women who were soft contact lens wearers developed fungal keratitis about 1 week after heavy exposure to environmental mold. Culture results showed Aspergillus from one patient and the unusual combination of Trichoderma and Penicillium from the other. Both were treated with topical natamycin, topical fluoroquinolone antibiotic prophylaxis, and periodic ulcer debridement. After many weeks of treatment, both ulcers healed with subsequent scarring. Because the ulcers were located in the peripheral cornea in both cases, excellent final visual acuities were achieved. Fungal keratitis cases like these are rarely seen at our referral clinic, which is located in the temperate climate of northeastern Indiana.

CONCLUSIONS

In addition to the usual recommended contact lens care guidelines, it may be prudent for eye care providers to warn patients against wearing their contact lenses in situations likely to result in heavy exposure to organic matter or, at the very least, to wear tight-fitting goggles for eye protection.

Phenotypic Investigation of Regenerated Epithelial Cells After Gonococcal Corneal Perforation: A Clinical, Histological, and Immunohistochemical Study

PURPOSE

To determine the characteristics of regenerated epithelial cells after severe gonococcal infection after corneal perforation.

METHODS

Pathological tissue was obtained from the cornea at the time of surgery. Hematoxylin and eosin staining and immunohistochemical analysis were performed for cytoskeletal keratins (K12, K13, and K15), basement membrane and junctional markers (laminin 5, ZO-1 and Desmoplakin), and proliferative and mesenchymal markers (Ki67, α-SMA, and vimentin).

RESULTS

A 42-year-old patient with severe gonococcal keratoconjunctivitis rapidly progressed to corneal perforation during administration of intensive topical and systemic antibiotics. After conservative treatment, the perforation healed and 5- × 3-mm corneal ectasia occurred with localized iris attachment. Complete closure of the cornea was confirmed by a negative Seidel test. After lamellar keratoplasty to improve corneal integrity and to prevent secondary glaucoma, the pathological tissue revealed a poorly organized epithelial layer at the regenerated ectatic area. The regenerated epithelial cells clearly expressed K12, ZO-1, and Desmoplakin with underlying laminin 5 (+) basement membrane. K15 and Ki67 expressions were observed predominantly at the limbal area but not in the regenerated area. α-SMA and vimentin were sporadically expressed in the underlying connective tissue.

CONCLUSIONS

We speculate that the process of epithelial wound healing at the site of corneal perforation was responsible for migration of the surrounding epithelial cells. Although the regenerated cells expressed several cytokeratins and junctional markers, they remained disorganized and fragile.

Contact lens associated microbial keratitis: practical considerations for the optometrist

Microbial keratitis (MK) is a corneal condition that encompasses several different pathogens and etiologies. While contact lens associated MK is most often associated with bacterial infections, other pathogens (fungi, Acanthamoeba species, etc) may be responsible. This review summarizes the risk factors, microbiology, diagnostic characteristics, and treatment options for all forms of contact lens-related MK.

Pattern recognition receptors in microbial keratitis

Microbial keratitis is a significant cause of global visual impairment and blindness. Corneal infection can be caused by a wide variety of pathogens, each of which exhibits a range of mechanisms by which the immune system is activated. The complexity of the immune response to corneal infection is only now beginning to be elucidated. Crucial to the cornea's defences are the pattern-recognition receptors: Toll-like and Nod-like receptors and the subsequent activation of inflammatory pathways. These inflammatory pathways include the inflammasome and can lead to significant tissue destruction and corneal damage, with the potential for resultant blindness. Understanding the immune mechanisms behind this tissue destruction may enable improved identification of therapeutic targets to aid development of more specific therapies for reducing corneal damage in infectious keratitis. This review summarises current knowledge of pattern-recognition receptors and their downstream pathways in response to the major keratitis-causing organisms and alludes to potential therapeutic approaches that could alleviate corneal blindness.

Corneal Cross-linking as an Adjuvant Therapy in the Management of Recalcitrant Deep Stromal Fungal Keratitis: A Randomized Trial

PURPOSE

To assess the efficacy of corneal cross-linking (CXL) as an adjuvant to appropriate antifungal therapy in nonresolving deep stromal fungal keratitis.

DESIGN

Randomized clinical trial.

METHODS

Eyes with culture-positive deep stromal fungal keratitis not responding to appropriate medical therapy for a period of 2 weeks were randomized to receive either adjuvant CXL or no additional treatment. Antifungal medical therapy was continued in both groups. The prespecified primary outcome was treatment failure at 6 weeks after enrollment, defined as perforation and/or increase in ulcer size by ≥2 mm.

RESULTS

The trial was stopped before full enrollment because of a marked difference in the rate of perforation between the 2 groups. Of the 13 cases enrolled in the study, 6 were randomized to the CXL group and 7 to the non-CXL group. Five eyes in the CXL group and 3 eyes in the non-CXL group experienced treatment failure by 6 weeks (P = .56). In a secondary analysis, the CXL group experienced more perforations than the non-CXL group (4 vs 0, respectively; P = .02).

CONCLUSION

CXL used as adjuvant therapy for recalcitrant deep stromal fungal keratitis did not improve outcomes.

Medical interventions for fungal keratitis

BACKGROUND

Fungal keratitis is a fungal infection of the cornea. It is common in lower income countries, particularly in agricultural areas but relatively uncommon in higher income countries. Although there are medications available, their effectiveness is unclear.

OBJECTIVES

To assess the effects of different antifungal drugs in the management of fungal keratitis.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2015, Issue 2), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to March 2015), EMBASE (January 1980 to March 2015), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to March 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 16 March 2015.

SELECTION CRITERIA

We included randomised controlled trials of medical therapy for fungal keratitis.

DATA COLLECTION AND ANALYSIS

Two review authors selected studies for inclusion in the review, assessed trials for risk of bias and extracted data. The primary outcome was clinical cure at two to three months. Secondary outcomes included best-corrected visual acuity, time to clinical cure, compliance with treatment, adverse outcomes and quality of life.

MAIN RESULTS

We included 12 trials in this review; 10 trials were conducted in India, one in Bangladesh and one in Egypt. Seven of these trials were at high risk of bias in one or more domains, two of these studies were at low risk of bias in all domains. Participants were randomised to the following comparisons: topical 5% natamycin compared to topical 1% voriconazole; topical 5% natamycin compared to topical 2% econazole; topical 5% natamycin compared to topical chlorhexidine gluconate (0.05%, 0.1% and 0.2%); topical 1% voriconazole compared to intrastromal voriconazole 50 g/0.1 mL (both treatments combined with topical 5% natamycin); topical 1% voriconazole combined with oral voriconazole compared to both oral voriconazole and oral itraconazole (both combined with topical 5% natamycin); topical 1% itraconazole compared to topical 1% itraconazole combined with oral itraconazole; topical amphotericin B compared to topical amphotericin B combined with subconjunctival injection of fluconazole; intracameral injection of amphotericin B with conventional treatment compared to conventional treatment alone (severe fungal ulcers); topical 0.5% and 1% silver sulphadiazine compared to topical 1% miconazole. Overall the results were inconclusive because for most comparisons only one small trial was available. The exception was the comparison of topical natamycin and topical voriconazole for which three trials were available. In one of these trials clinical cure (healed ulcer) was reported in all 15 people allocated to natamycin and in 14/15 people allocated to voriconazole (risk ratio (RR) 1.07; 95% confidence interval (CI) 0.89 to 1.28, low quality evidence). In one trial people randomised to natamycin were more likely to have a microbiological cure at six days (RR 1.64; 95% CI 1.38 to 1.94, 299 participants). On average, people randomised to natamycin had better spectacle-corrected visual acuity at two to three months compared to people randomised to voriconazole but the estimate was uncertain and the 95% confidence intervals included 0 (no difference) (mean difference -0.12 logMAR, 95% CI -0.31 to 0.06, 434 participants; 3 studies, low quality evidence) and a decreased risk of corneal perforation or therapeutic penetrating keratoplasty, or both (RR 0.61; 95% CI 0.40 to 0.94, 434 participants, high quality evidence). There was inconclusive evidence on time to clinical cure. Compliance with treatment and quality of life were not reported. One trial comparing natamycin and voriconazole found the effect of treatment greater in Fusarium species, but this subgroup analysis was not prespecified by this review.

AUTHORS' CONCLUSIONS

The trials included in this review were of variable quality and were generally underpowered. There is evidence that natamycin is more effective than voriconazole in the treatment of fungal ulcers. Future research should evaluate treatment effects according to fungus species.

Trends in bacterial and fungal keratitis in South India, 2002-2012

OBJECTIVE

To assess the trends in microbiological organisms identified from corneal scrapings from patients with infectious keratitis at a tertiary care medical centre in South India.

METHODS

We reviewed the records of the microbiology laboratory at Aravind Eye Hospital in Madurai, India, from 2002 until 2012. We identified the microbiological causes of all corneal ulcers from the culture and smear results, and assessed for trends in bacterial and fungal keratitis over time.

RESULTS

Of 23 897 corneal patients with ulcer with a corneal smear from 2002 to 2012 a fungal organism was identified in 34.3%, a bacterial organism in 24.7% and no organism in 38.3%. During this period, the annual number of keratitis cases due to bacteria decreased from 677 to 412, and the annual number due to fungus increased from 609 to 863. In analyses accounting for the total number of outpatients seen each year, the decline in number of smears positive for bacteria was statistically significant (p<0.001) but the increase in the number positive for fungus was not (p=0.73). The relative frequency of individual bacterial or fungal organisms remained relatively stable over this time.

CONCLUSIONS

At a tertiary eye care centre in South India, there has been a reduction in the numbers of smear-positive bacterial keratitis over the past 11 years. This decline likely reflects economic development in India and increased access to antibiotics.

Safety and efficacy of intrastromal injection of 5% natamycin in experimental fusarium keratitis

PURPOSE

To compare the efficacy of combined intrastromal injection and topical natamycin 5% to standard topical therapy alone in an experimental rabbit model of Fusarium keratitis.

METHODS

Fungal keratitis was induced in the right eyes of 12 New Zealand rabbits by stromal injection of Fusarium solani spore suspension into the cornea. Four days after inoculation, animals were randomly assigned to 2 different treatment groups (n=6 in each group). The study group received intrastromal injections of natamycin 5% on treatment day 1 and 4, combined with topical natamycin 5% eye drops given hourly between 8:00 and 20:00 for the first 2 days, followed by 4 times daily on days 3-11. The control group received only topical natamycin 5% at identical intervals. Eyes were examined clinically on days 1, 4, 7, and 11 for status of corneal healing, corneal vascularization, and hypopyon. Animals were sacrificed on day 11, and corneas were subjected to histopathological examination.

RESULTS

Both groups showed significant improvement in terms of conjunctival hyperemia, size and density of corneal infiltrate, corneal edema, and total clinical score. In the study group, there was a significant improvement in the height of hypopyon in the anterior chamber, while there was also an increased amount of vascularization.

CONCLUSIONS

This study showed that intrastromal injection of natamycin 5% combined with topical treatment has little beneficial effect over topical therapy in a Fusarium keratitis rabbit model. The addition of intrastromal injection should be reserved to the most severe or recalcitrant cases.