A 30-year-old gardener has a chronic indolent corneal infiltrate for six weeks after soil contamination. The lesion is a yellowish, wreath-shaped stromal infiltrate with satellite opacities, minimally responsive to routine antibiotics. Which laboratory technique will confirm the causative agent?
- A Calcofluor white staining of scrapings
- B Giemsa staining showing intranuclear inclusions
- C Modified acid-fast (Kinyoun) staining showing branching filaments ✓
- D India ink preparation showing budding yeast
Correct answer: C. Modified acid-fast (Kinyoun) staining showing branching filaments
Explanation
Nocardia asteroides is a gram-positive, weakly acid-fast filamentous bacterium identified by modified acid-fast stains such as Kinyoun. It causes chronic wreath-shaped keratitis after organic trauma. Calcofluor white detects fungi and Acanthamoeba cysts, Giemsa identifies chlamydial or viral inclusions, and India ink demonstrates Cryptococcus.
Reference: Yanoff and Duker Ophthalmology, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.