Which genera are most commonly implicated in fungal keratitis?

• A. Fusarium species and Aspergillus species
• B. Candida species
• C. Aspergillus species
• D. Histoplasma species

Answer: (C)

Fungal keratitis most often starts when environmental fungi invade the cornea after a breakdown in the surface barrier, such as trauma or exposure from contact lens wear. Among the fungal causes, Aspergillus species are the most commonly implicated organisms in keratitis. They are widespread environmental molds that readily invade corneal tissue once the epithelium is breached, leading to typical corneal infiltrates and potential complications like hypopyon. Laboratory clues that point to Aspergillus include septate hyphae with branching at acute angles and growth of mold on standard fungal media, which helps confirm the diagnosis. While Fusarium is also a common cause in certain settings, and Candida or Histoplasma can cause keratitis in other contexts, Aspergillus remains the most frequent culprit overall, making it the best answer in this context.