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
What is the drug of choice for listeriosis caused by Listeroa monocytogenes? 
Select and explain. 
A. Ampicillin, B. Amoxycillin, C. Vancomycin, D. Amikacin
A: Ampicillin
Answer: A: Ampicillin 
Explanation: Ampicillin is considered the drug of choice for treatment of infections caused by susceptible strains of enterococci and Listeria monocytogenes. Cephalosporins and fluoroquinolones are not active against L monocytogenes. Vancomycin is the drug of choice for staphylococcal infections. Amoxicillin is the drug of choice for acute otitis media, sinusitis, and other respiratory tract infections.