Polymicrobial Keratitis With Cryptococcus curvatus, Candida parapsilosis, and Stenotrophomonas maltophilia After Penetrating Keratoplasty: A Rare Case Report With Literature Review

Objectives: To report the first case of fungal keratitis caused by Cryptococcus curvatus after penetrating keratoplasty (PK) in an immunocompetent patient and to describe its therapeutic challenge and long-term outcome. Methods: An interventional case report. Results: A 54-year-old female patient underwent right PK for lattice dystrophy. At 5-year post-PK, she developed a polymicrobial keratitis caused by Candida parapsilosis, and Stenotrophomonas maltophilia at the peripheral graft, which was successfully treated with topical antibiotic and antifungal drops. One year later, another fungal keratitis occurred which apparently resolved with antifungal treatment but recurred in an unusual fashion and required a repeat PK revealing the diagnosis of C. curvatus keratitis. This was confirmed by microbiological culture on Sabouraud dextrose agar, nuclear ribosomal repeat regional sequencing of the D1-D2 and internal transcribed spacer regions, and histopathological examination. Various topical, intracorneal, and systemic antifungal treatments had been attempted but failed to resolve the infection completely, necessitating a subsequent third PK. A further recurrence was noted 16-month post-third PK, which was eradicated with multiple topical and intracorneal antifungal treatment, and direct cryotherapy to the corneal abscess. No further recurrence of C. curvatus was noted at 4-year follow-up. Conclusions: Cryptococcus curvatus should be added to the known list of organisms capable of causing fungal keratitis. Our experience suggests that this type of organism could cause low-grade, grumbling infection, which may however be exceptionally difficult to treat. Long-term eradication of this rare fungal keratitis could be potentially achieved by intensive ocular and systemic antifungal treatment, repeat therapeutic keratoplasties, and focal cryotherapy.