Contact lens-associated fusarium keratitis in Switzerland

Mycotic Keratitis-A Global Threat from the Filamentous Fungi

Mycotic or fungal keratitis (FK) is a sight-threatening disease, caused by infection of the cornea by filamentous fungi or yeasts. In tropical, low and middle-income countries, it accounts for the majority of cases of microbial keratitis (MK). Filamentous fungi, in particular Fusarium spp., the aspergilli and dematiaceous fungi, are responsible for the greatest burden of disease. The predominant risk factor for filamentous fungal keratitis is trauma, typically with organic, plant-based material. In developed countries, contact lens wear and related products are frequently implicated as risk factors, and have been linked to global outbreaks of Fusarium keratitis in the recent past. In 2020, the incidence of FK was estimated to be over 1 million cases per year, and there is significant geographical variation; accounting for less than 1% of cases of MK in some European countries to over 80% in parts of south and south-east Asia. The proportion of MK cases is inversely correlated to distance from the equator and there is emerging evidence that the incidence of FK may be increasing. Diagnosing FK is challenging; accurate diagnosis relies on reliable microscopy and culture, aided by adjunctive tools such as in vivo confocal microscopy or PCR. Unfortunately, these facilities are infrequently available in areas most in need. Current topical antifungals are not very effective; infections can progress despite prompt treatment. Antifungal drops are often unavailable. When available, natamycin is usually first-line treatment. However, infections may progress to perforation in ~25% of cases. Future work needs to be directed at addressing these challenges and unmet needs. This review discusses the epidemiology, clinical features, diagnosis, management and aetiology of FK.

Fusarium Keratitis in Germany

Fusarium keratitis is a destructive eye infection that is difficult to treat and results in poor outcome. In tropical and subtropical areas, the infection is relatively common and associated with trauma or chronic eye diseases. However, in recent years, an increased incidence has been reported in temperate climate regions. At the German National Reference Center, we have observed a steady increase in case numbers since 2014. Here, we present the first German case series of eye infections with Fusarium species. We identified Fusarium isolates from the eye or eye-related material from 22 patients in 2014 and 2015. Thirteen isolates belonged to the Fusarium solani species complex (FSSC), 6 isolates belonged to the Fusarium oxysporum species complex (FOSC), and three isolates belonged to the Fusarium fujikuroi species complex (FFSC). FSSC was isolated in 13 of 15 (85%) definite infections and FOSC in 3 of 4 (75%) definite contaminations. Furthermore, diagnosis from contact lens swabs or a culture of contact lens solution turned out to be highly unreliable. FSSC isolates differed from FOSC and FFSC by a distinctly higher MIC for terbinafine. Outcome was often adverse, with 10 patients requiring keratoplasty or enucleation. The use of natamycin as the most effective agent against keratitis caused by filamentous fungi was rare in Germany, possibly due to restricted availability. Keratitis caused by Fusarium spp. (usually FSSC) appears to be a relevant clinical problem in Germany, with the use of contact lenses as the predominant risk factor. Its outcome is often adverse.

Altered Patterns of Fungal Keratitis at a London Ophthalmic Referral Hospital: An Eight-Year Retrospective Observational Study

PURPOSE

In previous studies of fungal keratitis (FK) from temperate countries, yeasts were the predominant isolates, with ocular surface disease (OSD) being the leading risk factor. Since the 2005-2006 outbreak of contact lens (CL)-associated Fusarium keratitis, there may have been a rise in CL-associated filamentary FK in the United Kingdom. This retrospective case series investigated the patterns of FK from 2007 to 2014. We compared these to 1994-2006 data from the same hospital.

DESIGN

Retrospective observational study.

METHODS

All cases of FK presenting to Moorfields Eye Hospital between 2007 and 2014 were identified. The definition of FK was either a fungal organism isolated by culture or fungal structures identified by light microscopy (LM) of scrape material, histopathology, or in vivo corneal confocal microscopy (IVCM). Main outcome measure was cases of FK per year.

RESULTS

A total of 112 patients had confirmed FK. Median age was 47.2 years. Between 2007 and 2014, there was an increase in annual numbers of FK (Poisson regression, P = .0001). FK was confirmed using various modalities: 79 (70.5%) by positive culture, 16 (14.3%) by LM, and 61 (54.5%) by IVCM. Seventy-eight patients (69.6%) were diagnosed with filamentary fungus alone, 28 (25%) with yeast alone, and 6 (5.4%) with mixed filamentary and yeast infections. This represents an increase in the proportion of filamentary fungal infections from the pre-2007 data. Filamentary fungal and yeast infections were associated with CL use and OSD, respectively.

CONCLUSIONS

The number of FK cases has increased. This increase is due to CL-associated filamentary FK. Clinicians should be aware of these changes, which warrant epidemiologic investigations to identify modifiable risk factors.

Recent outbreaks of atypical contact lens-related keratitis: what have we learned?

PURPOSE

To examine the public health implications of 2 recent outbreaks of atypical contact lens-related infectious keratitis.

DESIGN

Perspective based on the literature and authors' experience.

RESULTS

The contact lens-related Fusarium and Acanthamoeba keratitis outbreaks were each detected by dramatic rises seen in tertiary care centers in Singapore and the United States, respectively. Case-control studies of both outbreaks were able to identify a strong association with the use of different contact lens disinfection solutions. Their respective recalls resulted in a steep decline of Fusarium keratitis, but not of Acanthamoeba keratitis. Early investigations into each solution association implicated components not directly related to their primary disinfectant, but the true pathogenesis remains unknown. However, the number of Acanthamoeba cases individually attributed to each of almost all available disinfection systems exceeds the previously understood total United States incidence, suggesting other risk factors. Current standards do not require demonstration of anti-acanthamoebal activity. Yet, despite the inclusion of Fusarium in mandatory testing for solutions, current premarket testing was not predictive of the outbreak.

CONCLUSIONS

The 2 recent outbreaks of atypical contact lens-related keratitis have reinforced the value of tertiary care eye care centers in detecting early rises in rare infections and the power of adaptable, well-designed epidemiologic investigations. Although Fusarium keratitis has declined significantly with the recall of Renu with MoistureLoc (Bausch & Lomb Inc.), the persistence of Acanthamoeba keratitis demands fundamental changes in contact lens hygiene practices, inclusion of Acanthamoeba as a test organism, and contact lens disinfectant test regimens for all contact lens-related pathogens that are verifiably reflective of end user contact lens wear complications.

[Successful treatment of resistant Fusarium solani keratitis with liposomal amphotericin B]

INTRODUCTION

The prognosis for Fusarium keratitis is poor. Effective drugs to treat this infection are therefore needed.

CASE REPORT

A patient presented Fusarium solani keratitis. The infection regressed with topical amphotericin B and intravenous voriconazole. Topical steroids were introduced. There was reactivation and extension of the infection, invading the anterior chamber. Steroids were discontinued and the antifungal treatment was restarted but there was continued deterioration. Recovery was achieved without surgery, with topical voriconazole, topical liposomal amphotericin B, topical natamycin, intravenous liposomal amphotericin B, and intravenous voriconazole.

CONCLUSION

Combined orally and topically administered voriconazole is a promising therapy when the minimum inhibitory concentration is approximately 2 microg/ml. Liposomal amphotericin B seems to be the most effective drug for the different infection stages. Posaconazole is a useful alternative but further investigations must be pursued.