Mycotic keratitis caused by concurrent infections of exserohilum mcginnisii and candida parapsilosis

Background: Mycotic keratitis in human cornea has been rarely reported to be associated with a co-infection of filamentous fungi and yeast. This paper aims to report a case of mycotic keratitis concurrently infected by Exserohilum mcginnisii and Candida parapsilosis. Case presentation: A Chinese female presented two superposed corneal infiltrates with different size and texture on her left eye. In vivo confocal microscopy showed hyper-reflective multiple linear with highly branching structures distributing in the anterior corneal stroma. Inoculations of the corneal lesion scrape concurrently grew two similar superposed colonies on Sabouraud dextrose and chocolate agar plate. The larger colony exhibited mould, cottony and floccose at the edge, while the smaller one showed creamy and shiny surface. Modified slide culture for mould revealed hyphae were septate, and conidia were brown, smooth-walled, cylindrical to slight clavate with 6 to 13 pseudosepta. Based on the morphology of microscopic and macroscopic characteristics, the mould was identified as Exserohilum mcginnisii. Smear of the non-mould colony showed ellipse or ovoid budding yeast-like cells with abundant pseudomycelium. Vitek Yeast Biochemical Card test identified the yeast as Candida parapsilosis. With treatment of combined oral itraconazole with topical amphotericin B, a complete resolution of the corneal infiltrate was achieved within 1.5 months. Conclusion: This is the first documented case of human corneal infection by Exserohilum mcginnisii, and also the first report providing evidence of mycotic keratitis in human cornea concurrently infected by filamentous fungi and yeast.