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: Microbiology
Which of the following organisms, when isolated in the blood, requires the synergistic activity of penicillin plus an aminoglycoside for appropriate therapy- 
Select and explain. 
A. Enterococcus faecalis, B. Staphylococcus aureus, C. Str. pneumoniae, D. Bacteroides fragilis
A: Enterococcus faecalis
Answer: A: Enterococcus faecalis 
Explanation: Ans. is 'a' i.e., Enterococcus faecalis "Unlike streptococci, enterococci are not reliably killed by penicillin or ampicillin alone. Because of synergistic action of Penicillin and aminoglycoside against enterococci combination therapy is recommended ".