A Sneaky Culprit: Secondary Infectious Keratitis Due to Brevundimonas diminuta

To describe a rare case of infectious keratitis secondary to Brevundimonas diminuta , a gram-negative bacillus with fluoroquinolone resistance and rare clinical isolation.

A 50-year-old man with contact lens overuse presented with a large corneal ulcer and hand motion visual acuity. Initial treatment with fortified topical tobramycin and vancomycin yielded slow improvement, and initial culture grew Staphylococcus epidermidis , Staphylococcus hominis , and Corynebacterium bovis . Therapy was tapered to topical moxifloxacin. Loteprednol was added to reduce corneal inflammation after presumed sterilization. Persistent epithelial defect and worsening infiltrate after 3 weeks prompted repeat culture and corneal punch biopsy.

Repeat culture revealed B. diminuta resistant to moxifloxacin. Treatment was modified to tobramycin, and therapeutic penetrating keratoplasty was pursued to prevent further stromal loss. Four months postoperatively, the cornea remained clear without recurrence or neovascularization.

To our knowledge, this is the second reported culture-positive case of secondary infectious keratitis with B. diminuta , highlighting its rarity and potential for delayed identification. The atypical response to initial therapy underscores the importance of repeat cultures and corneal biopsy in persistent cases. This case contributes to the growing understanding of rare ocular pathogens, advocating for a vigilant clinical approach.