Corynebacterium bovis Keratitis Mimicking Acanthamoeba Infection Following Ocular Trauma

Corneal isolates of Corynebacterium species are frequently dismissed as contaminants, yet they are capable of causing severe, vision-threatening keratitis. A 45-year-old man with no history of contact lens use developed acute left eye pain and visual loss after a stone fragment struck his eye during work, with immediate contamination by garden hose water. Slit-lamp examination revealed a ring-shaped stromal infiltrate with visual acuity reduced to light perception, a presentation consistent with Acanthamoeba keratitis. Empiric therapy with fortified topical vancomycin and ceftazidime, antifungal and anti-amoebic agents, and systemic antibiotics was initiated before culture results were available. Admission evaluation identified previously undiagnosed diabetes mellitus with a hemoglobin A1c level of 12.1%. Corneal cultures grew Corynebacterium bovis as the sole organism, confirmed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry; Acanthamoeba and fungal cultures were negative at four weeks. The patient improved on culture-directed topical vancomycin but required surgical debridement 28 days after discharge for a persistent corneal abscess with hypopyon; intraoperative cultures were sterile, and the globe was preserved. C. bovis keratitis can present with morphologic and clinical features that closely mimic Acanthamoeba infection; in the setting of ocular trauma and metabolic risk factors, diphtheroid corneal isolates should be considered pathogens until culture and clinical correlation suggest otherwise.