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Identification and molecular characterization of Subramaniula asteroides causing human fungal keratitis: a case
Rosario Cultrera1, Riccardo Torelli2, Caterina Sarnicola3
1Department of Morphology, Surgery and Experimental Medicine, Infectious Diseases Unit, University 'S. Anna' Hospital of Ferrara, Via Aldo Moro 8, 44124, Ferrara, Italy. ctr@unife.it.
Background:
Keratitis due to by filamentous fungi are not easy to diagnose thus causing a delay in correct therapy. There are many descriptions of keratitis due to Candida, Fusarium and Aspergillus genera. Subramaniula genus has only recently been reported to cause human infections and there are few descriptions of eye infections due to this filamentous fungus. Diagnosis of fungal keratitis is usually based on microscopic and cultural techniques of samples obtained by corneal swabbing or scraping. Considering the amount of time required to obtain culture results it is wise to use other diagnostic methods, such as molecular analyses. Therapeutic options against these fungi are limited by low tissue penetration in the eye due to ocular barriers. We describe the first case of S. asteroides human keratitis treated with isavuconazole.
Case Presentation:
We describe a rare case of fungal keratitis unresponsive to antimicrobial treatment in a 65-year-old male patient without a history of diabetes or immunological diseases. He reported that the onset of symptoms occurred during a long holiday in Cape Verde Island. Initial treatment with topical antibiotics associated to steroids were ineffective, allowing a slow clinical progression of disease to corneal perforation. On admission in our Hospital, slit-lamp examination of the left eye showed conjunctival congestion and hyperemia, a large inferior corneal ulceration with brown pigment, corneal edema, about 3 mm of hypopyon and irido-lenticular synechiae. The slow clinical progression of the disease to corneal perforation and the aspect of the ulcer were consistent with a mycotic etiology. Molecular methods used on fungal colonies isolated by Sabouraud's dextrose agar cultures allowed the identification of Subramaniula asteroids from corneal scraping. Antimicrobial test showed a good susceptibility of this filamentous fungus to voriconazole and isavuconazole. Moreover, this fungal keratitis was successfully treated with isavuconazole, without side effects, observing a progressive clinical improvement.
Conclusions:
Molecular methods may be useful for the identification of filamentous fungal keratitis on scraping samples thus shortening the time of diagnosis. Systemic therapy by isavuconazole could be useful to treat the filamentous fungal keratitis, reducing the possible adverse effects due to the use of voriconazole by systemic administration.
Insights
This study reports the first case of human keratitis caused by Subramaniula asteroides, a rare filamentous fungus. The infection was successfully treated with isavuconazole, offering a new therapeutic option for this difficult-to-diagnose condition.
Area of Science:
- Ophthalmology
- Mycology
- Infectious Diseases
Background:
- Fungal keratitis, particularly from rare genera like Subramaniula, presents diagnostic challenges and limited treatment options due to ocular barriers.
- Traditional diagnosis relies on microscopy and cultures, which are time-consuming, delaying appropriate therapy.
- Subramaniula asteroides is a recently identified fungus with few reported human infections, making its clinical presentation and management less understood.
Observation:
- A 65-year-old male presented with severe keratitis unresponsive to standard antimicrobial and steroid treatment, progressing to corneal perforation.
- Clinical examination revealed a large, pigmented corneal ulcer with hypopyon and conjunctival hyperemia, suggestive of a fungal etiology.
- Molecular identification confirmed Subramaniula asteroides isolated from corneal scrapings.
Findings:
- Molecular methods provided a rapid and accurate diagnosis of fungal keratitis caused by Subramaniula asteroides.
- Antimicrobial susceptibility testing indicated sensitivity to voriconazole and isavuconazole.
- Successful treatment of the fungal keratitis was achieved using systemic isavuconazole without reported side effects.
Implications:
- Molecular diagnostics can significantly shorten the time to diagnosis for filamentous fungal keratitis, enabling prompt treatment.
- Systemic isavuconazole represents a potentially safer and effective alternative to voriconazole for treating fungal keratitis, minimizing systemic adverse effects.
- This case expands the understanding of Subramaniula asteroides as a human pathogen and highlights isavuconazole as a viable therapeutic agent.
