A complex case of Nocardia keratitis: challenges in diagnosis and therapy

Abstract

Nocardia keratitis is a rare cause of microbial keratitis, primarily affecting patients in tropical and subtropical regions. Its diagnostic challenge arises from this keratitis uncommon presentation, which often mimics other infectious keratitis types, leading to delays in appropriate treatment. This case report aims to elucidate the complexities of diagnosing and managing Nocardia keratitis of a 41-year-old male who had a chronic, progressively worsening wreath-pattern corneal infiltrate and hypopyon following ocular trauma. Initial empirical treatments were ineffective. Diagnostic confirmation via corneal scraping culture enabled targeted antimicrobial therapy. Subconjunctival amikacin and topical tobramycin led to gradual improvement, though complications such as corneal scarring and neovascularization remained, indicating potential need for surgical intervention. This case emphasizes the importance of high clinical suspicion and precise laboratory diagnostics in managing rare cases of Nocardia keratitis. Establishing standardized treatment guidelines for rare ocular infections could improve clinical outcomes.

Figure 1. Slit lamp photographs of the LE: (A) Initial presentation: corneal "wreath-pattern" infiltrate (yellow arrows) with satellite lesions (green arrow) and hypopyon; (B) One month: After taking subconjunctival amikacin for five days, tobramycin ED, and cotrimoxazole tablets, hypopyon resolved completely, but peripheral corneal neovascularization emerged; (C) Six months after admission: resolved Nocardia keratitis showed leucoma and neovascularization, the surrounding cornea remains clear.

Figure 2. Microbiological examinations: (A) Blood agar inoculated with corneal scrapings showing white, dry, and chalky colonies (blue arrow); (B) Gram-positive thin branching filaments bacteria (blue arrow) on Gram stain; (C) Positive acid-fast staining (blue arrow).