<prompt> Which organism infection is virulent and may cause corneal ulcer perforation within 48hrs?PseudomonasAspergillusHerpes simplexStaphylococci  <response>: Ans. a PseudomonasRef: Khurana 6e, p. 102 Pseudomonas ulcers are usually associated with hypopyon, spread very rapidly may even perforate within 48 - 72 hrs. Pseudomonas is the most common gram negative organism causing corneal ulcer. 