This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diseases of Cornea, Subject name: Ophthalmology
Which organismal infection is highly virulent & cause corneal ulcer perforation within 48 hr? 
Select and explain. 
A. Herpes simplex, B. Pseudomonas, C. Staphylococci, D. Aspergillus
B: Pseudomonas
Answer: B: Pseudomonas 
Explanation: Pseudomonas bacterial keratitis is most virulent and can cause corneal ulcer perforation within 48 hours. Pseudomonas ulcer : Most common cause of infection in contact lens users Very virulent Can stimulate fungal corneal ulcer Impoant Points to Remember in Bacterial Keratitis: *Symptoms more pronounced than sign. *Staphyococcus most common cause for bacterial keratitis. *Most common cause of contact lens related keratitis- Pseudomonas. *Ulcer Serpens- Pneumococcus. *Organisms that can breach intact corneal epithelium - Gonococci, Meningiococci, Shigella, Corynebacterium diphtheria, H. influenza biotype III, Listeria monocytogenes