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Emerging Dematiaceous and Hyaline Fungi Causing Keratitis in a Tertiary Care Centre From North India
Anup Ghosh1, Harsimran Kaur1, Amit Gupta2
1Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India; and.
Purpose:
To report rare dematiaceous and hyaline fungal pathogens causing fungal keratitis (FK) at our center and review the published literature in this field.
Methods:
In a retrospective review of FK cases from 2005 to 2011, a total of 14 rare pathogens causing isolated cases of FK of a total of 393 isolates were revived from our collection and reconfirmed by using molecular techniques. The in vitro antifungal susceptibility testing (AFST) was performed against a 6-antifungal drug panel by the CLSI microbroth-dilution method. We reviewed the literature on keratitis due to these rare fungi.
Results:
Two novel fungi, Alternaria tenuissima and Epicoccum nigrum, were reported in addition to 6 dematiaceous (black pigmented) fungi (Acrophialophora fusispora, Chaetomium globosum, Cladophialophora carionii, Nigrospora sphaerica, Papulaspora equi, and Scytalidium lignicola), 5 hyaline (colorless) fungi (Aspergillus tamarii, Fusarium chlamydosporum, Fusarium incarnatum, Fusarium lichenicola, and Fusarium sacchari), and one yeast (Trichosporon asahii). Amphotericin B had good in vitro activity (minimum inhibitory concentration [MIC] ≤1 μg/mL) against most dematiaceous fungi, but not hyaline fungi (MIC ≥1 μg/mL). Natamycin showed variable MIC, itraconazole and voriconazole had good in vitro activity, except in Fusarium species. Alternaria tenuissima and A. fusispora had a very high MIC (≥16 μg/mL) against echinocandins. Literature search revealed 27 FK cases due to F. lichenicola (n = 6), P. equi (n = 5), F. sacchari (n = 4), A. fusispora (n = 3), S. lignicola (n = 2), and others (n = 7), and more than 50% of these were reported from India.
Conclusions:
Plant fungal pathogens with variable antifungal susceptibility are an emerging cause of human keratitis with predominance of dematiaceous fungi. Identification and antifungal susceptibility testing are important for epidemiology and to optimize therapy and improve the patient outcome.
Insights
Rare fungal keratitis is increasingly caused by plant pathogens, with dematiaceous fungi being most common. Accurate identification and antifungal susceptibility testing are crucial for effective treatment and improved patient outcomes in fungal keratitis cases.
Area of Science:
- Ophthalmology
- Mycology
- Infectious Diseases
Background:
- Fungal keratitis (FK) is a significant cause of visual impairment globally.
- Rare fungal pathogens, including dematiaceous and hyaline fungi, can cause FK.
- Understanding the spectrum of these rare pathogens and their susceptibility is vital for clinical management.
Purpose of the Study:
- To identify and characterize rare dematiaceous and hyaline fungal pathogens causing FK.
- To review the existing literature on keratitis caused by these specific fungi.
- To assess the in vitro antifungal susceptibility of these rare fungal isolates.
Main Methods:
- Retrospective review of 393 FK isolates from 2005-2011.
- Identification of 14 rare fungal pathogens using molecular techniques.
- In vitro antifungal susceptibility testing (AFST) against a six-antifungal drug panel using CLSI microbroth-dilution method.
- Comprehensive literature review on keratitis caused by these rare fungi.
Main Results:
- Two novel fungi, Alternaria tenuissima and Epicoccum nigrum, were identified, alongside six dematiaceous and five hyaline fungi, and one yeast.
- Amphotericin B showed good activity against most dematiaceous fungi but not hyaline fungi.
- Itraconazole and voriconazole demonstrated good in vitro activity, with exceptions in Fusarium species. Echinocandins were ineffective against Alternaria tenuissima and Acrophialophora fusispora.
- Literature search identified 27 FK cases attributed to specific rare fungi, with over 50% reported from India.
Conclusions:
- Plant-derived fungal pathogens are an emerging cause of human keratitis.
- Dematiaceous fungi are predominant among these rare causes of FK.
- Accurate fungal identification and AFST are essential for optimizing therapy and improving patient outcomes in FK.
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