This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lens, Subject name: Ophthalmology
[{'content': 'Late onset endophthalmitis after cataract surgery is caused by \nSelect and explain. \nA. Streptococcus pyogenes, B. Propionibacterium acne, C. Staphylococcus aureus, D. Pseudomonas', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Bacterial endophthalmitis: This is one of the most dreaded complications with an incidence of 0.2 to 0.5 percent. The principal sources of infection are contaminated solutions, instruments, surgeon&;s hands, patient&;s own flora from conjunctiva, eyelids and air-borne bacteria. Symptoms and signs: Present between 48 and 72 hours after surgery and include: ocular pain, diminshed vision, lid oedema, conjunctival chemosis and marked circumciliary congestion, corneal oedema, exudates in pupillary area, hypopyon and diminished or absent red pupillary glow. Delayed chronic postoperative endophthalmitis : is caused when an organism of low virulence (Propionobacterium acne or staph epidermidis) becomes trapped within the capsular bag. It has an onset ranging from 4 weeks to years (mean 9 months) postoperatively. Ref:- A K KHURANA; pg num:-200,201', 'role': 'assistant'}]