The Utility of Repeat Culture in Fungal Corneal Ulcer Management: A Secondary Analysis of the MUTT-I Randomized Clinical Trial

Recent Advances in Diagnosis and Treatment Approaches in Fungal Keratitis: A Narrative Review

Fungal keratitis represents a potentially sight-threatening infection associated with poor prognosis, as well as financial burden. Novel diagnostic methods include polymerase-chain-reaction (PCR)-based approaches, metagenomic deep sequences, in vivo confocal microscopy, and antifungal susceptibility testing. The ideal therapeutic approaches and outcomes have been widely discussed in recent times, with early therapy being of the utmost importance for the preservation of visual acuity, minimizing corneal damage and reducing the scar size. However, combination therapy can be more efficacious compared to monotherapy. Understanding the pathogenesis, early diagnosis, and prevention strategies can be of great importance. In this narrative, we discuss the recent progress that may aid our understanding of the diagnosis, treatment, and prevention of mycotic keratitis.

Modern Technologies in Diagnosis of Fungal Keratitis (Review)

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

Double-masked, sham and placebo-controlled trial of corneal cross-linking and topical difluprednate in the treatment of bacterial keratitis: Steroids and Cross-linking for Ulcer Treatment Trial (SCUT II) study protocol

Introduction

Although antibiotics are successful at achieving microbiological cure in infectious keratitis, outcomes are often poor due to corneal scarring. Ideal treatment of corneal ulcers would address both the infection and the inflammation. Adjunctive topical steroid treatment may improve outcomes by reducing inflammation. Corneal cross-linking (CXL) is a novel prospective therapy that may simultaneously reduce both inflammatory cells and bacterial pathogens. The purpose of this study is to determine differences in 6-month visual acuity between standard medical therapy with antibiotics versus antibiotics with adjunctive early topical steroid therapy versus antibiotic treatment plus CXL and early topical steroids.

Methods and analysis

This international, randomised, sham and placebo-controlled, three-arm clinical trial randomises patients with smear positive bacterial ulcers in a 1:1:1 fashion to one of three treatment arms: (1) topical 0.5% moxifloxacin plus topical placebo plus sham CXL; (2) topical 0.5% moxifloxacin plus difluprednate 0.05% plus sham CXL; or (3) the CXL group: topical 0.5% moxifloxacin plus difluprednate 0.05% plus CXL.

Ethics and dissemination

We anticipate that both adjunctive topical steroids and CXL will improved best spectacle corrected visual acuity and also reduce complications such as corneal perforation and the need for therapeutic penetrating keratoplasty. This study will comply with the NIH Data Sharing Policy and Policy on the Dissemination of NIH-Funded Clinical Trial Information and the Clinical Trials Registration and Results Information Submission rule. Our results will be disseminated via ClinicalTrials.gov website, meetings and journal publications. Our data will also be available on reasonable request.

Trial registration number

NCT04097730.

Fusarium Keratitis-Review of Current Treatment Possibilities

In many parts of the world, fungi are the predominant cause of infectious keratitis; among which, Fusarium is the most commonly isolated pathogen. The clinical management of this ophthalmic emergency is challenging. Due to the retardation of the first symptoms from an injury and the inability to differentiate fungal from bacterial infections based on clinical symptoms and difficult microbial diagnostics, proper treatment, in many cases, is postponed. Moreover, therapeutical options of Fusarium keratitis remain limited. This paper summarizes the available treatment modalities of Fusarium keratitis, including antifungals and their routes of administration, antiseptics, and surgical interventions.

Recent Perspectives in the Management of Fungal Keratitis

Mycotic keratitis is common in warm, humid regions with a varying profile of pathogenic fungi according to geographical origin, socioeconomic status, and climatic condition. Clinical diagnosis can be challenging in difficult cases and those refractory to treatment. Fungal hyphae on microscopic examination and culture isolation have been the gold standard in the laboratory diagnosis of fungal keratitis. A culture isolate of the aetiological fungus is essential to perform antifungal susceptibility testing. As the culture isolation of fungi is time-consuming, causing delays in the initiation of treatment, newer investigative modalities such as in vivo confocal microscopy and molecular diagnostic methods have recently gained popularity. Molecular diagnostic techniques now help to obtain a rapid diagnosis of fungal keratitis. Genomic approaches are based on detecting amplicons of ribosomal RNA genes, with internal transcribed spacers being increasingly adopted. Metagenomic deep sequencing allows for rapid and accurate diagnosis without the need to wait for the fungus to grow. This is also helpful in identifying new emerging strains of fungi causing mycotic keratitis. A custom-tear proteomic approach will probably play an important diagnostic role in future in the management of mycotic keratitis. Positive repeat cultures are being suggested as an important gauge indicative of a poor prognosis. Positive repeat fungal cultures help to modify a treatment regimen by increasing its frequency, providing the addition of another topical and oral antifungal agent along with close follow-up for perforation and identifying need for early therapeutic keratoplasty. The role of collagen crosslinking in the treatment of fungal keratitis is not convincingly established. Rapid detection by multiplex PCR and antifungal susceptibility testing of the pathogenic fungi, adopted into a routine management protocol of fungal keratitis, will help to improve treatment outcome. Early therapy is essential in minimizing damage to the corneal tissue, thereby providing a better outcome. The role of conventional therapy with polyenes, systemic and targeted therapy of antifungal agents, newer azoles and echinocandins in fungal keratitis has been widely studied in recent times. Combination therapy can be more efficacious in comparison to monotherapy. Given the diversity of fungal aetiology, the emergence of new corneal pathogenic fungi with varying drug susceptibilities, increasing the drug resistance to antifungal agents in some genera and species, it is perhaps time to adopt recent molecular methods for precise identification and incorporate antifungal susceptibility testing as a routine.

The global incidence and diagnosis of fungal keratitis

Fungal keratitis is a severe corneal infection that often results in blindness and eye loss. The disease is most prevalent in tropical and subtropical climates, and infected individuals are frequently young agricultural workers of low socioeconomic status. Early diagnosis and treatment can preserve vision. Here, we discuss the fungal keratitis diagnostic literature and estimate the global burden through a complete systematic literature review from January, 1946 to July, 2019. An adapted GRADE score was used to evaluate incidence papers-116 studies provided the incidence of fungal keratitis as a proportion of microbial keratitis and 18 provided the incidence in a defined population. We calculated a minimum annual incidence estimate of 1 051 787 cases (736 251-1 367 323), with the highest rates in Asia and Africa. If all culture-negative cases are assumed to be fungal, the annual incidence would be 1 480 916 cases (1 036 641-1 925 191). In three case series, 8-11% of patients had to have the eye removed, which represents an annual loss of 84 143-115 697 eyes. As fungal keratitis probably affects over a million people annually, an inexpensive, simple diagnostic method and affordable treatment are needed in every country.

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.

Cross-Linking Assisted Infection Reduction (CLAIR): A Randomized Clinical Trial Evaluating the Effect of Adjuvant Cross-Linking on Bacterial Keratitis

PURPOSE

To determine whether there is a benefit to adjuvant corneal cross-linking (CXL) for bacterial keratitis.

METHODS

This is an outcome-masked, randomized controlled clinical trial. Consecutive patients presenting with a smear-positive bacterial ulcer at Aravind Eye Hospitals at Madurai, Pondicherry, and Coimbatore in India were enrolled. Study eyes were randomized to topical moxifloxacin 0.5% or topical moxifloxacin 0.5% plus CXL. The primary outcome of the trial was microbiological cure at 24 hours on repeat culture. Secondary outcomes included best spectacle corrected visual acuity at 3 weeks and 3 months, percentage of study participants with epithelial healing at 3 weeks and 3 months, infiltrate and/or scar size at 3 weeks and 3 months, 3-day smear and culture, and adverse events.

RESULTS

Those randomized to CXL had 0.60 decreased odds of culture positivity at 24 hours (95% confidence interval [CI]: 0.10-3.50; P = 0.65), 0.9 logarithm of the minimum angle of resolution lines worse visual acuity (95% CI: -2.8 to 4.6; P = 0.63), and 0.41-mm larger scar size (95% CI: -0.48 to 1.30; P = 0.38) at 3 months. We note fewer corneal perforations or need for therapeutic penetrating keratoplasty in the CXL group.

CONCLUSIONS

We were unable to confirm a benefit to adjuvant CXL in the primary treatment of moderate bacterial keratitis. However, CXL may reduce culture positivity and complication rates; therefore, a larger trial to fully evaluate this is warranted.

TRIAL REGISTRATION

NCT02570321.

The Prognostic Value of Persistent Culture Positivity in Fungal Keratitis in the Mycotic Antimicrobial Localized Injection Trial

PURPOSE

To evaluate the utility of repeat cultures at days 3 and 7 after starting antifungal medications for predicting outcomes in fungal keratitis.

DESIGN

Prespecified secondary analysis of the randomized clinical Mycotic Antimicrobial Localized Injection trial.

METHODS

Patients presenting to Aravind Eye Hospital, Pondicherry, India, with fungal keratitis and visual acuity worse than 20/70 received topical natamycin and were randomized to either receive intrastromal injection of voriconazole or topical therapy alone. All subjects received corneal cultures at date of presentation, day 3, and day 7. Outcome measures included 3-week and 3-month visual acuity and scar size, corneal perforation, and/or the need for therapeutic penetrating keratoplasty (TPK). Visual acuity and scar size were analyzed with multiple linear regression controlling for baseline measures. Survival analysis was used to analyze the risk of corneal perforation and/or need for TPK.

RESULTS

Of the 70 study subjects with fungal keratitis, 25 of 69 (36%) remained culture positive at day 3, and 20 of 62 (32%) were culture positive at day 7. Culture positivity at day 3 conferred a hazard ratio of 2.8 for requiring TPK (P = .03) but was not a statistically significant predictor of perforation, scar size, or final visual acuity. Culture positivity at day 7 had a hazard ratio of 3.5 for requiring TPK (P = .003). Those with positive cultures at day 7 had on average 3 logMAR lines worse visual acuity at 3 months (95% confidence interval 0.9 to 5.2 logMAR lines, P = .006) and 1.1 mm larger scar size at 3 months after controlling for baseline measures (95% confidence interval 0.1 to 2.2 mm; P = .03).

CONCLUSIONS

While not as predictive as day 7 cultures, culture positivity at day 3 after starting treatment is a significant predictor of the need for TPK in patients with moderate-to-severe filamentous fungal keratitis. This has applications for risk stratification, and may facilitate earlier consideration of TPK in high-risk patients.

Cross-Linking-Assisted Infection Reduction: A Randomized Clinical Trial Evaluating the Effect of Adjuvant Cross-Linking on Outcomes in Fungal Keratitis

PURPOSE

To determine if there is a benefit to adjuvant corneal crosslinking (CXL) and to compare natamycin versus amphotericin B for filamentous fungal keratitis.

DESIGN

Outcome-masked, 2×2 factorial design, randomized controlled clinical trial.

PARTICIPANTS

Consecutive patients presenting with moderate vision loss from a smear-positive fungal ulcer at Aravind Eye Hospital, Madurai, India.

METHODS

Study eyes were randomized to 1 of 4 treatment combinations using an adaptive randomization protocol. The treatment arms included (1) topical natamycin 5% alone, (2) topical natamycin 5% plus CXL, (3) topical amphotericin B 0.15% alone, and (4) topical amphotericin 0.15% plus CXL.

MAIN OUTCOME MEASURES

The primary outcome of the trial was microbiological cure at 24 hours on repeat culture. Secondary outcomes included best spectacle-corrected visual acuity (BSCVA) at 3 weeks and 3 months, percentage of study participants with epithelial healing at 3 days, 3 weeks, and 3 months, infiltrate or scar size at 3 weeks and 3 months, 3-day smear and culture, and adverse events.

RESULTS

Those randomized to CXL regardless of medication (topical natamycin or amphotericin) had 1.32-fold increased odds of 24-hour culture positivity, although this was not statistically significant (95% confidence interval [CI], 0.57-3.06; P = 0.51). We were also unable to find a difference in 24-hour culture positivity between those randomized to amphotericin and those randomized to natamycin when evaluating as a group regardless of whether or not they received CXL (coefficient 1.10; 95% CI, 0.47-2.54; P = 0.84). The BSCVA was approximately 0.22 logarithm of the minimum angle of resolution (logMAR) (2.2 Snellen lines) worse on average at 3 weeks among those receiving CXL regardless of medication (95% CI, -0.04 to 0.40; P = 0.04) and 0.32 logMAR (3.2 Snellen lines) worse visual acuity at 3 months after controlling for baseline visual acuity (95% CI, 0.03-0.54; P = 0.02). There was no difference in infiltrate or scar size, percentage of epithelialized or adverse events when comparing CXL with no CXL or the 2 topical medications.

CONCLUSIONS

There appears to be no benefit of adjuvant CXL in the primary treatment of moderate filamentous fungal ulcers, and it may result in decreased visual acuity.

Mycotic Antimicrobial Localized Injection: A Randomized Clinical Trial Evaluating Intrastromal Injection of Voriconazole

PURPOSE

To determine if there is a benefit to adjuvant intrastromal voriconazole (ISV) injections for primary treatment of filamentous fungal keratitis.

DESIGN

Outcome-masked, randomized controlled clinical trial.

PARTICIPANTS

Patients with moderate vision loss resulting from a smear-positive fungal ulcer.

METHODS

Study eyes were randomized to topical natamycin plus ISV injection versus topical natamycin alone.

MAIN OUTCOME MEASURES

The primary outcome of the trial was microbiological cure on 3-day repeat culture analysis. Secondary outcomes included microbiological cure on 7-day repeat culture analysis; 3-week and 3-month best spectacle-corrected visual acuity; infiltrate or scar size or both; rate of perforation; therapeutic penetrating keratoplasty (TPK); and other adverse events.

RESULTS

A total of 151 patients with smear-positive ulcers were screened and 70 were enrolled at Aravind Eye Hospital, Pondicherry, India. Baseline cultures grew Fusarium in 19 samples (27%), Aspergillus in 17 samples (24%), and other filamentous fungi in 19 samples (27%) and showed negative results in 13 samples (19%). Those randomized to ISV injection had 1.82 times the odds of 3-day culture positivity after controlling for baseline culture status (95% confidence interval [CI], 0.65-5.23; P = 0.26, bias-corrected logistic regression) and 1.98 times the odds of positive 7-day culture results, after controlling for baseline culture status (95% CI, 0.69-5.91; P = 0.20, bias-corrected logistic regression). Those randomized to ISV injection showed 0.5 logMAR lines (approximately 0.5 Snellen lines) of decreased visual acuity (95% CI, -2.6 to 3.6 lines; P = 0.75) and 0.55 mm worse infiltrate or scar size or both at 3 months after controlling for baseline values (95% CI, -0.13 to 1.25; P = 0.11). Intrastromal voriconazole injections showed a 2.85-fold increased hazard of perforation after controlling for baseline infiltrate depth (95% CI, 0.76-10.75; P = 0.12) but no difference in the rate of TPK (hazard ratio, 0.95; 95% CI, 0.44-2.04; P = 0.90).

CONCLUSIONS

There seems to be no benefit to adding ISV injections to topical natamycin in the primary treatment of moderate to severe filamentous fungal ulcers. Studies consistently suggest that voriconazole has a limited role in the treatment of filamentous fungal ulcers.

Therapeutic Penetrating Keratoplasty Button Cultures in The Mycotic Ulcer Treatment Trial II: A Randomized Trial Comparing Oral Voriconazole Versus Placebo

OBJECTIVE

To compare oral voriconazole vs placebo in addition to topical antifungals in the treatment of filamentous fungal keratitis.

DESIGN

Non-prespecified, secondary case-control analysis from a multicenter, double-masked, randomized placebo-controlled clinical trial.

METHODS

Study Participants: Patients with smear-positive filamentous fungal ulcers and visual acuity of 20/400 or worse who eventuated to therapeutic penetrating keratoplasty (TPK).

INTERVENTION

Study participants were randomized to oral voriconazole vs oral placebo; all received topical antifungal drops.

MAIN OUTCOME MEASURES

TPK button culture positivity.

RESULTS

A total of 95 of 194 (49.5%) study participants enrolled at Madurai, Coimbatore, or Pondicherry, India eventuated to TPK in an average of 20.9 days (standard deviation 15.2 days, range 2-71 days). TPK button cultures were available for 67 of 95 (71%) of the TPKs performed and were positive for filamentous fungus in 45 of 67 (67%) cases. For each 1-day increase in the time to TPK there was 0.94-fold decreased odds of fungal culture positivity (95% confidence interval [CI] 0.90-0.98, P = .005). Those randomized to oral voriconazole had 1.26-fold increased odds of TPK button culture positivity after controlling for time to TPK and baseline organism, but this was not statistically significant (95% CI 0.32-4.87; P = .74). Those who underwent TPK for lack of response to medical therapy were 10.64-fold more likely to be culture positive than if the indication for surgery was perforation and this was statistically significant (95% CI 2.16-51.70; P = .003).

CONCLUSIONS

There appears to be no benefit to adding oral voriconazole to topical antifungal agents in the treatment of severe filamentous fungal ulcers. Infection rather than inflammation appears to be the reason for the worsening clinical picture in many of these patients.

Fungal keratitis: An overview of clinical and laboratory aspects

Mycotic keratitis or keratomycosis is a fungal infection with global distribution. The dominant aetiology of this disease varies based on geographical origin, socioeconomic status, and climatic condition. Generally, Aspergillus spp. and Fusarium spp. are common in tropical and subtropical regions and Candida spp. are dominant in temperate areas. Demonstration of fungal elements in microscopic examination besides the isolation of fungi in culture is the gold standard of laboratory diagnosis. As the culture is a time-consuming procedure, other approaches such as in vivo confocal microscopy which produces real-time imaging of corneal tissue and molecular techniques have been developed to facilitate rapid diagnosis of fungal keratitis. The first choice of treatment is topical natamycin, although topical amphotericin B is the best choice for Aspergillus and Candida keratitis. Regarding the diversity of fungal aetiology and the emergence of drug resistance in some genera and species, proper identification using molecular methods and antifungal susceptibility testing could provide useful data. Furthermore, as the better efficacy of combination therapy in comparison to monotherapy is reported, in vitro determination of interactions between various drugs seem informative. This review aims to provide a general and updated view on the aetiology, risk factors, epidemiology, clinical and laboratory diagnosis, and management of fungal keratitis.

The Significance of Repeat Cultures in the Treatment of Severe Fungal Keratitis

PURPOSE

To identify fungal keratitis patients who are at risk of a poor outcome and may benefit from closer follow-up or more aggressive treatment.

DESIGN

Secondary analysis of randomized clinical trial data.

METHODS

We compared the clinical outcomes of patients who had positive 6-day fungal cultures with those who did not, using backward stepwise regression with covariates for all baseline clinical characteristics.

SUBJECTS

Patients presenting with a smear-positive filamentous fungal ulcer and visual acuity of 20/400 or worse, and who subsequently had a 6-day fungal culture performed at the Aravind Eye Care system (India), Lumbini Eye Hospital (Nepal), or Bharatpur Eye Hospital (Nepal).

MAIN OUTCOME MEASURES

The primary outcome is rate of corneal perforation and/or the need for therapeutic penetrating keratoplasty. Secondary outcomes include 3-month best spectacle-corrected visual acuity (BSCVA), 3-month infiltrate and/or scar size, and rate of re-epithelialization.

RESULTS

Patients who tested positive at their 6-day culture had twice the hazard of experiencing a corneal perforation or the need for therapeutic penetrating keratoplasty (P = .002) than those who tested negative, even after controlling for baseline ulcer characteristics. These patients also had on average 0.26 logMAR lines worse BSCVA at 3 months (P = .001). Culture positivity at day 6 was not a statistically significant predictor of 3-month infiltrate/scar-size (-0.24 mm¹; P = .45) or time to re-epithelialization (hazard ratio = .81; P = .31).

CONCLUSIONS

Here we identify a uniquely valuable clinical tool, day 6 culture results, for the treatment of severe fungal keratitis. Risk stratification based on repeat culture positivity is an objective way to assess response to medical therapy and identify patients who are at high risk of a poor clinical outcome. This establishes a new standard of care for severe fungal keratitis management.

[Fungal keratitis: A 5-year monocentric retrospective study on Reunion Island]

OBJECTIVES

Fungal keratitis is rare in France, but could be a severe sight-threatening condition. Here, we aimed to describe the epidemiology of fungal keratitis in Réunion Island.

METHODS

In a retrospective study, we analyzed 13 culture-proven keratitis episodes, occurred between January 2013 and July 2017 in the ophthalmology ward of a University Hospital, Saint-Pierre. Twelve isolates were genotyped and antifungal susceptibility testing was performed.

RESULTS

Corneal abrasion caused by vegetable matter was the main predisposing factor. Stromal infiltration was observed in 12 patients. Six patients did not response to medical treatment, requiring surgical care, including two enucleations surgery. Fusarium solani (n = 6) and Fusarium dimerum (n = 4) were the main fungal species involved in fungal keratitis. Clinical failures were more prevalent with F. solani infections. The lowest minimal inhibitory concentrations for Fusarium sp. were observed with voriconazole and amphotericin B.

CONCLUSION

In Reunion Island, the epidemiology of fungal keratitis is characterized by the predominance of Fusarium species, potentially involved in visual loss. This pattern is consistent with the epidemiology usually observed in tropical areas.