Metagenomic analysis for detecting Fusarium solani in a case of fungal keratitis

Abstract Purpose To report a difficult-to-identify case of keratitis due to Fusarium solani , diagnosed with the help of exhaustive gene analysis. Case A 47-year-old woman attended our hospital with a refractory corneal ulcer associated with contact lens wear in her left eye that had appeared two weeks earlier. On her initial visit, slit lamp examination revealed a small double-ringed irregular hyphate ulcer in the center of the cornea, which had no epithelial defect, suggesting fungal infection. Microscopic visualization and culture of corneal scrapings were performed repeatedly, but the results were negative. Despite intensive antifungal treatment, infiltration of the cornea worsened and therapeutic keratoplasty was performed. Specimens from a corneal button were microbiologically and histologically negative for microorganisms. During irrigation of the anterior chamber with amphotericin B, aspirated corneal infiltrations were submitted for culture and metagenomic analysis. Genes belonging to F. solani were identified by metagenomic analysis, and an isolate presumed to be a Fusarium species was cultured. Genotypic identification of the isolates confirmed F. solani . Conclusion The detection of microorganisms, especially fungi, can be extremely difficult. In difficult-to-culture cases, metagenomic analysis seems to be a promising technique for the identification of microbial pathogens.