This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
Which is the most common cause of liver abscess in adults? 
Select and explain. 
A. Streptococcus pyogenes, B. Staph. aureus, C. E. coli, D. Proteus
C: E. coli
Answer: C: E. coli 
Explanation: E.coli is the most common cause of liver abscess in adults. Polymicrobial involvement is common in pyogenic liver abscess with Escherichia coli and Klebsiella pneumoniae being the two most frequently isolated pathogens.