Keratitis due to Fusarium langsethiae: clinical profile, molecular identification, and susceptibility to antifungals

We report a case of keratitis due to Fusarium langsethiae in a 56-year-old man. The patient presented with pain and tearing of 10 days duration in the right eye, which had sustained a paddy stalk injury. On examination, a hypopyon corneal ulcer was noted in the right eye. Multiple scrapings were obtained from the affected part of the cornea. A lactophenol cotton blue wet mount and a Gram-stained smear of scrapings were made. Scrapings were also inoculated on various culture media, including Sabouraud dextrose agar (SDA). A fungal etiology was sought by conventional microbiological techniques and polymerase chain reaction. In vitro susceptibility testing was performed by an agar dilution method. Direct microscopy of corneal scrapings revealed septate hyphae, leading to initiation of intensive topical therapy with natamycin (5 %). However, the keratitis progressed, necessitating therapeutic penetrating keratoplasty. White, powdery-like colonies, with abundant aerial mycelium, were recovered on SDA from corneal scrape material. Based on macroscopic and microscopic morphological features, the isolated fungus was initially identified as a Fusarium species. Sequence analysis of the 28S rRNA region of the fungal genome led to a specific identification of F. langsethiae. Antifungal susceptibility testing results suggested that the strain isolated was susceptible to voriconazole, ketoconazole, and itraconazole. To our knowledge, this is the first reported case of keratitis due to F. langsethiae; attention is drawn to the unique characteristics of the fungal isolate, difficulties in identification and non-responsiveness to medical therapy.