Which two fungi are most commonly implicated in fungal keratitis?

• A. Fusarium species and Aspergillus species
• B. Candida albicans and Cryptococcus neoformans
• C. Aspergillus niger and Histoplasma capsulatum
• D. Mucorales and Coccidioides immitis

Answer: (B)

Fungal keratitis is most often caused by environmental molds that invade the cornea after a break in the epithelium. The two species most commonly implicated worldwide are Fusarium and Aspergillus. They are frequent in warm, humid climates and among contact lens wearers or after ocular trauma with plant matter, because their hyphae readily penetrate corneal tissue and spread within the stroma. Microscopy typically shows septate hyphae, and culture can reveal distinctive features such as Fusarium’s canoe-shaped macroconidia or Aspergillus’s radiating conidiophores. First-line therapy is usually topical natamycin, with other antifungals used based on susceptibility and response. Candida albicans and Cryptococcus neoformans are yeasts and can cause keratitis in some contexts (e.g., immune compromise or postoperative settings), but they are less commonly the main culprits compared with Fusarium and Aspergillus. Mucorales and Coccidioides are not typical primary causes of fungal keratitis.