A 60-year-old patient presents with a well-demarcated, dense white corneal infiltrate surrounded by a large hypopyon. The patient reports using homemade saline for rigid gas-permeable contact lenses. Gram stain shows gram-negative bacilli with a large mucoid capsule. Which organism is the most likely cause?

• A Streptococcus pneumoniae
• B Staphylococcus aureus
• C Pseudomonas aeruginosa ✓
• D Moraxella species

Explanation

Pseudomonas aeruginosa classically produces a rapidly progressive, suppurative keratitis with a large mucoid capsule and dense greenish discharge in contact lens wearers. The large hypopyon is characteristic of severe gram-negative keratitis. Streptococcus pneumoniae causes an indolent, pneumococcal ulcer; Staphylococcus produces a well-defined, smaller infiltrate; Moraxella causes indolent peripheral ulcers in debilitated or alcoholic patients.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.