The mycotic ulcer treatment trial: a randomized trial comparing natamycin vs voriconazole

In vitro susceptibility of filamentous fungi from mycotic keratitis to azole drugs

OBJECTIVE

The in vitro antifungal activities of azole drugs viz., itraconazole, voriconazole, ketoconazole, econazole and clotrimazole were investigated in order to evaluate their efficacy against filamentous fungi isolated from mycotic keratitis.

METHODS

The specimen collection was carried out from fungal keratitis patients attending Aravind eye hospital and Post-graduate institute of ophthalmology, Coimbatore, India and was subsequently processed for the isolation of fungi. The dilutions of antifungal drugs were prepared in RPMI 1640 medium. Minimum inhibitory concentrations (MICs) were determined and MIC50 and MIC90 were calculated for each drug tested.

RESULTS

A total of 60 fungal isolates were identified as Fusarium spp. (n=30), non-sporulating moulds (n=9), Aspergillus flavus (n=6), Bipolaris spp. (n=6), Exserohilum spp. (n=4), Curvularia spp. (n=3), Alternaria spp. (n=1) and Exophiala spp. (n=1). The MICs of ketoconazole, clotrimazole, voriconazole, econazole and itraconazole for all the fungal isolates ranged between 16 μg/mL and 0.03 μg/mL, 4 μg/mL and 0.015 μg/mL, 8 μg/mL and 0.015 μg/mL, 8 μg/mL and 0.015 μg/mL and 32 μg/mL and 0.06 μg/mL respectively. From the MIC50 and MIC90 values, it could be deciphered that in the present study, clotrimazole was more active against the test isolates at lower concentrations (0.12-5 μg/mL) when compared to other drugs tested.

CONCLUSION

The results suggest that amongst the tested azole drugs, clotrimazole followed by voriconazole and econazole had lower MICs against moulds isolated from mycotic keratitis.

Exoproteome of Aspergillus flavus corneal isolates and saprophytes: identification of proteoforms of an oversecreted alkaline protease

Aspergillus flavus infects the human eye leading to keratitis. Extracellular proteins, the earliest proteins that come in contact with the host and virulence related exoproteins, were identified in the fungus isolated from infected cornea. Virulence of the corneal isolates was tested in the Galleria mellonella larvae model and those isolates showing higher virulence were taken for subsequent exoproteome analysis. High resolution two-dimensional electrophoresis and mass spectrometry were used to generate A. flavus exoproteome reference map as well as to profile most of the exoproteins. Analysis of the identified proteins clearly shows the major biological processes that they are involved in. Nearly 50% of the exoproteins possess catalytic activity and one of these, an alkaline serine protease (Alp1) is present in high abundance as well as multiple proteoforms. Many proteins in the A. flavus exoproteome have been shown to be virulence factors in other pathogens indicating the probable role for these proteins in the corneal infection as well. Interestingly, the majority of the exoproteins do not have secretory signal indicating that they are secreted through the non-classical pathway. Thus, this study provides a clue to the early strategies employed by the pathogen to establish an infection in an immunocompetent host.

BIOLOGICAL SIGNIFICANCE

The outcome of a fungal infection in an immunocompetent human eye depends on the ability of the fungus to overcome the host defense and propagate itself. In this process, the earliest events with respect to the fungal proteins involved include the secretory proteins of the invading organism. As a first step towards understanding the role of the extracellular proteins, exoproteome profile of the fungal isolates was generated. The fungal isolates from cornea showed a distinct pattern of the exoproteome when compared to the saprophyte. Since corneal isolates also showed higher virulence in the insect larval model, presumably the proteins elaborated by the corneal isolates are virulence related. One of the abundant proteins is an alkaline serine protease and this protein exists as multiple proteoforms. This study reports the comprehensive profile of exoproteome and reveals proteins that are potential virulence factors.

Aspergillus flavus endophthalmitis after penetrating keratoplasty combined with cataract phacoemulsification and IOL implantation

To report the clinical findings and management of a case of Aspergillus flavus endophthalmitis following penetrating keratoplasty (PKP) and combined cataract extraction. Clinical cornea appearance was evaluated by slit-lamp examination. Ocular ultrasonography was performed to evaluate the anterior chamber and vitreous cavity. The cornea was scraped. The corneal-scleral donor rim and media were cultured. The diagnosis of A. flavus infection was made. The patient received fortified antifungal drops (voriconazole 1 % solution) plus systemic voriconazole 400 mg/die. A second corneal transplant was performed, and the anterior chamber was cleaned and washed with a solution of voriconazole 1 %. At the end of follow-up, CDVA was 20/20 and slit-lamp examination showed a clear cornea graft. This case illustrates a severe A. flavus endophthalmitis after PKP and demonstrates the possibilities of visual function restoration. Furthermore, this case describes the different sources of fungal infection after PKP and the different clinical appearances.

Evaluation of corneal collagen cross-linking as an additional therapy in mycotic keratitis

BACKGROUND

To report the treatment outcomes of mycotic keratitis with collagen cross-linking.

DESIGN

Retrospective study.

PARTICIPANTS

Patients with smear-positive moderate mycotic keratitis.

METHODS

A retrospective case-file analysis was performed to identify cases of moderate mycotic keratitis treated with and without additional collagen cross-linking, in addition to intensive topical antifungal therapy. Patients in which collagen cross-linking was performed on the day of presentation (group 1) were compared with patients who received medical treatment alone in the form of 5% natamycin eye drops (group 2).

MAIN OUTCOME MEASURES

The primary outcome measure was the time taken for resolution of infection.

RESULTS

Overall, 41 cases were included for analysis (group 1, 20 cases; group 2, 21 cases). Mean age of the patients was comparable in both groups (46.5 ± 17.01 vs. 41.2 ± 20.7 years; P = 0.36). Average infiltrate size was 16.35 ± 6.8 mm(2) in group 1 and 17.09 ± 7.4 mm(2) in group 2 (P = 0.83). Overall, Aspergillus was the most commonly isolated organism (n = 4 group 1; n = 6 group 2). Resolution of infection was observed in 18 cases (90%) in group 1 and 18 (85.71%) cases in group 2. The average healing time was 30.85 ± 26.6 days in group 1, while it was 31.28 ± 19.97 days in group 2 (P = 0.94). Final best-corrected visual acuity in group 1 was 1.13 ± 0.55 and 1.25 ± 0.46 in group 2 (P = 0.46). A tectonic keratoplasty was performed in two cases in group 1 and three cases in group 2 (P = 1.00).

CONCLUSIONS

In our study, additional collagen cross-linking treatment did not have any advantage over medical management in cases with moderate mycotic keratitis.

Intrastromal voriconazole for deep recalcitrant fungal keratitis: a case series

AIM

To evaluate the outcomes of treating deep recalcitrant fungal keratitis with intrastromal voriconazole injection.

METHODS

Twenty-five patients with culture proven fungal keratitis, not responding to a combination of topical 5% natamycin and 1% voriconazole were treated with intrastromal voriconazole (50 µg/0.1 mL) injected in five divided doses around the infiltrate to form a depot of the drug around the circumference of the lesion.

RESULTS

The mean age of the patients was 52.52±12.21 years and mean time to presentation was 17.12±13.75 days from the onset of symptoms. The mean area of the infiltrate was 30.41±17.2 mm(2), hypopyon was present in 88% and all cases had infiltrates that extended beyond the mid-stromal level. Intrastromal voriconazole helped to resolve the infection in 18 (72%) patients and about 15% of these needed more than one injection. Smaller ulcers responded better to treatment. Fusarium spp were responsible for six of the seven cases that failed treatment.

CONCLUSIONS

Targeted delivery of voriconazole by intrastromal injection (50 µg/0.1 mL) is a safe and effective way to treat deep recalcitrant fungal keratitis, though some may need repeated injections. Fusarium keratitis may show suboptimal response but this needs further study.

The negligible effects of the antifungal natamycin on cholesterol-dipalmitoyl phosphatidylcholine monolayers may explain its low oral and topical toxicity for mammals

Natamycin is an effective, broad spectrum antifungal with no reported resistance, in contrast to most antimicrobials. It also exhibits reduced (oral and topical) toxicity to humans, which is probably associated with the lack of effects on mammalian cell membranes. In this paper we employ Langmuir monolayers to mimic a cell membrane, whose properties are interrogated with various techniques. We found that natamycin has negligible effects on Langmuir monolayers of dipalmitoyl phosphatidylcholine (DPPC), but it strongly affects cholesterol monolayers. Natamycin causes the surface pressure isotherm of a cholesterol monolayer to expand even at high surface pressures since it penetrates into the hydrophobic chains. It also reduces the compressibility modulus, probably because natamycin disturbs the organization of the cholesterol molecules, as inferred with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). In mixed cholesterol/DPPC monolayers, strong effects from natamycin were only observed when the cholesterol concentration was 50mol% or higher, well above its concentration in a mammalian cell membrane. For a sterol concentration that mimics a real cell membrane in mammals, i.e. with 25mol% of cholesterol, the effects were negligible, which may explain why natamycin has low toxicity when ingested and/or employed to treat superficial fungal infections.

Association between in vitro susceptibility to natamycin and voriconazole and clinical outcomes in fungal keratitis

PURPOSE

To assess the association between minimum inhibitory concentration (MIC) and clinical outcomes in a fungal keratitis clinical trial.

DESIGN

Experimental study using data from a randomized comparative trial.

PARTICIPANTS

Of the 323 patients enrolled in the trial, we were able to obtain MIC values from 221 patients with monocular fungal keratitis.

METHODS

The Mycotic Ulcer Treatment Trial I was a randomized, double-masked clinical trial comparing clinical outcomes of monotherapy with topical natamycin versus voriconazole for the treatment of fungal keratitis. Speciation and determination of MIC to natamycin and voriconazole were performed according to Clinical and Laboratory Standards Institute guidelines. The relationship between MIC and clinical outcome was assessed.

MAIN OUTCOME MEASURES

The primary outcome was 3-month best spectacle-corrected visual acuity. Secondary outcomes included 3-month infiltrate or scar size; corneal perforation and/or therapeutic penetrating keratoplasty; and time to re-epithelialization.

RESULTS

A 2-fold increase in MIC was associated with a larger 3-month infiltrate or scar size (0.21 mm; 95% confidence interval [CI], 0.10-0.31; P < 0.001) and increased odds of perforation (odds ratio, 1.32; 95% CI, 1.04-1.69; P = 0.02). No correlation was found between MIC and 3-month visual acuity. For natamycin-treated cases, an association was found between higher natamycin MIC with larger 3-month infiltrate or scar size (0.29 mm; 95% CI, 0.15-0.43; P < 0.001) and increased perforations (odds ratio, 2.41; 95% CI, 1.46-3.97; P < 0.001). Among voriconazole-treated cases, the voriconazole MIC did not correlate with any of the measured outcomes in the study.

CONCLUSIONS

Decreased susceptibility to natamycin was associated with increased infiltrate or scar size and increased odds of perforation. There was no association between susceptibility to voriconazole and outcome.

In vitro susceptibility of filamentous fungal isolates from a corneal ulcer clinical trial

PURPOSE

To describe the minimum inhibitory concentration (MIC) of fungal isolates to natamycin and voriconazole, and to compare these MICs to previous ocular susceptibility studies.

DESIGN

Experimental laboratory study using isolates from a randomized clinical trial.

METHODS

The Mycotic Ulcer Treatment Trial I was a randomized, double-masked, multicenter trial comparing topical natamycin and voriconazole for fungal keratitis treatment. Susceptibility testing to natamycin and voriconazole were performed according to Clinical and Laboratory Standards Institute methods. The relationship between organism and MIC was assessed. A literature review was performed to compare results to previous ocular susceptibility studies.

RESULTS

Of the 323 patients enrolled in the trial, MICs were available for 221 (68%). Fusarium (n = 126) and Aspergillus species (n = 52) were the most commonly isolated organisms. MICs to natamycin and voriconazole were significantly different across all genera (P < .001). The MIC median (MIC50) and 90th percentile (MIC90) for natamycin were equal to or higher than voriconazole for all organisms except Curvularia species. Compared to other organisms, Fusarium species isolates had the highest MICs to voriconazole and Aspergillus flavus isolates had the highest MICs to natamycin. Our results were similar to previous reports except that the voriconazole MIC90 against Aspergillus species was 2-fold higher and the natamycin MIC90 against Aspergillus fumigatus was 4-fold higher in our study.

CONCLUSION

In this large susceptibility study, Fusarium isolates were least susceptible to voriconazole and A flavus isolates were least susceptible to natamycin when compared to other filamentous fungi. In the future, susceptibility testing may help guide therapy if performed in a timely manner.

Effectiveness of Topical Antifungal Drugs in the Management of Fungal Keratitis: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Fungal keratitis (FK) typically requires intensive therapy with topical antifungal agents. To date, evidence from clinical trials has been conflicting with respect to the most effective topical antifungal drug in the treatment of FK. Therefore, a systematic review and meta-analysis of randomized controlled trials (RCTS) using the Cochrane methodology was undertaken to evaluate the effectiveness of topical antifungals in management of FK. Outcomes included time to cure, treatment failure, complications of infection, visual acuity and adverse effects. A comprehensive search for studies was undertaken resulting in inclusion of 8 RCTs, predominantly from India, involving a total of 793 participants, the majority of whom were infected with filamentous fungi. Topical voriconazole was more likely to result in therapeutic keratoplasty compared with natamycin [relative risk (RR) 1.89 95% CI: 1.14, 3.12] with a number needed to treat of 13 (95% CI: 7, 50). Final visual acuity was significantly better with natamycin compared with voriconazole [weighted mean difference (WMD) 0.13, 95% CI 0.00, 0.27]. There was no difference in risk of treatment failure across all topical antifungal treatments studied (chlorhexidine gluconate, econazole, miconazole, natamycin, silver sulphadiazine and voriconazole). This study suggests treatment failure was comparable among antifungal treatments reviewed. However, natamycin resulted in better visual acuity following acute infection, compared with voriconazole. Voriconazole had a significantly greater risk of therapeutic keratoplasty compared with natamycin in the populations studied.

Expert prior elicitation and Bayesian analysis of the Mycotic Ulcer Treatment Trial I

PURPOSE

To perform a Bayesian analysis of the Mycotic Ulcer Treatment Trial I (MUTT I) using expert opinion as a prior belief.

METHODS

MUTT I was a randomized clinical trial comparing topical natamycin or voriconazole for treating filamentous fungal keratitis. A questionnaire elicited expert opinion on the best treatment of fungal keratitis before MUTT I results were available. A Bayesian analysis was performed using the questionnaire data as a prior belief and the MUTT I primary outcome (3-month visual acuity) by frequentist analysis as a likelihood.

RESULTS

Corneal experts had a 41.1% prior belief that natamycin improved 3-month visual acuity compared with voriconazole. The Bayesian analysis found a 98.4% belief for natamycin treatment compared with voriconazole treatment for filamentous cases as a group (mean improvement 1.1 Snellen lines, 95% credible interval 0.1-2.1). The Bayesian analysis estimated a smaller treatment effect than the MUTT I frequentist analysis result of 1.8-line improvement with natamycin versus voriconazole (95% confidence interval 0.5-3.0, P = 0.006). For Fusarium cases, the posterior demonstrated a 99.7% belief for natamycin treatment, whereas non-Fusarium cases had a 57.3% belief.

CONCLUSIONS

The Bayesian analysis suggests that natamycin is superior to voriconazole when filamentous cases are analyzed as a group. Subgroup analysis of Fusarium cases found improvement with natamycin compared with voriconazole, whereas there was almost no difference between treatments for non-Fusarium cases. These results were consistent with, though smaller in effect size than, the MUTT I primary outcome by frequentist analysis. The accordance between analyses further validates the trial results. (ClinicalTrials.gov number, NCT00996736.).