Which organism is the most common cause of bacterial corneal ulcer in India, and what is its characteristic gram staining appearance?

Explanation

## Epidemiology of Bacterial Corneal Ulcer **Key Point:** Pseudomonas aeruginosa is the most common cause of bacterial corneal ulcer in India and other tropical regions, accounting for 30–50% of cases. ### Organism Characteristics | Feature | Pseudomonas aeruginosa | |---------|------------------------| | Gram staining | Gram-negative rod | | Morphology | Slender, aerobic, motile | | Pigment | Pyoverdine (green), pyocyanin (blue) | | Culture medium | MacConkey agar (non-lactose fermenter) | | Oxidase test | Positive | **High-Yield:** Pseudomonas is an opportunistic pathogen that thrives in moist environments (contact lens wear, eye trauma, ocular surface disease). It produces exotoxins and elastase, leading to rapid corneal necrosis and perforation if untreated. ### Clinical Significance **Clinical Pearl:** Pseudomonas corneal ulcers are characterized by: - Rapid progression (24–48 hours) - Stromal infiltration with greenish discoloration - Hypopyon formation - Risk of perforation and endophthalmitis **Mnemonic:** **PSEUDOMONAS** = **P**erforation **R**apid **O**pportunistic **O**rganisms **F**ound in **M**oist environments ### Treatment Implications Requires aggressive topical fluoroquinolone therapy (ciprofloxacin, ofloxacin, moxifloxacin) with frequent dosing (every 15–30 minutes initially). Systemic antibiotics may be needed for severe cases. [cite:Khurana Comprehensive Ophthalmology Ch 4]