This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
Late onset endophthalmitis after cataract surgery is most often caused by: 
Select and explain. 
A. Staphylococcus Epidermidis, B. Pseudomonas, C. Streptococcus Pyogenes, D. Propionobacterium Acnes
D: Propionobacterium Acnes
Answer: D: Propionobacterium Acnes 
Explanation: Propionobacterium Acnes - most frequent isolate in chronic postoperative endophthalmitis followed by S.epidermidis, aerobic streptococci and Actinomyces species. Most frequent repoed organism is Propionobacterium Acnes. Ref: Clinical Eye Atlas - Page 700; Complications in Phacoemulsification: Avoidance, Recognition, and Management - Page 304.