A 30-year-old contact lens wearer presents with a rapidly progressive corneal ulcer developing over 24 hours, showing a large epithelial defect with greenish mucopurulent exudate and hypopyron. Gram stain reveals gram-negative rods. Which virulence factor of this organism is primarily responsible for the rapid stromal destruction?

• A Exotoxin A causing epithelial necrosis
• B Flagella mediating tissue invasion
• C Lipopolysaccharide triggering intense inflammation
• D Alkaline protease and elastase degrading stromal collagen ✓

Explanation

Pseudomonas aeruginosa produces alkaline protease and elastase (LasA and LasB) that rapidly degrade corneal stromal collagen, explaining the characteristic rapid melting and progression over hours. Exotoxin A causes tissue damage but is not the primary collagenolytic factor. LPS drives inflammation but does not directly destroy stroma.

Reference: Basic and Clinical Science Course, Section 8: External Disease and Cornea, AAO 2023-2024 ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.