Background and Purpose

Fungal keratitis remains a major cause of corneal blindness, particularly in individuals with ocular trauma or environmental exposure. Accurate and timely identification of the etiologic agent is important for appropriate treatment. This report describes a case of keratitis caused by an uncommon dematiaceous fungus, identified using a sequencing-based approach, highlighting the role of molecular diagnostics in clinical practice.

Case presentation

A 25-year-old male presented with redness and pain in the right eye after exposure to dust. On slit lamp examination, a 5 mm × 3 mm superficial corneal infiltrate was noted, and the best-corrected visual acuity in the affected eye was 20/50. Corneal scrapings were obtained and examined microscopically, revealing septate fungal filaments. Sample was cultured on Sabouraud Dextrose Agar, which produced rapidly growing, initially colourless colonies that later developed black pigmentation at the margins. To accurately identify the fungal species, DNA was extracted from the culture and analysed using Oxford Nanopore Sequencing targeting the ITS gene.

Results

The colonies observed on culture suggested the presence of a dematiaceous fungus. Sequencing confirmed the organism as Podospora bulbillosa, a rare fungal species not commonly associated with ocular infections. The patient was started on 5% natamycin eye drops administered topically. Over the course of treatment, the infiltrate showed gradual resolution. Complete clinical recovery was achieved with restoration of visual acuity and no residual scarring or complications noted on follow-up examination.

Conclusion

This case highlights the utility of molecular diagnostic techniques in the identification of rare fungal pathogens in keratitis. Incorporating sequencing tools can aid in precise pathogen detection and guide targeted therapy. Podospora bulbillosa should be considered as a potential etiological agent in cases of fungal keratitis, especially in settings where exposure to environmental contaminants occurs. Early recognition and appropriate antifungal treatment can result in successful outcomes, even in infections caused by rare fungal species.