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: Unknown
In a patient of nephritic syndrome with spontaneous bacterial peritonitis, which one of the following micro-organisms is most commonly involved? 
Select and explain. 
A. Proteus, B. Escherichia, C. Pneumococcus, D. Staphylococcus
B: Escherichia
Answer: B: Escherichia 
Explanation: Spontaneous bacterial peritonitismeans peritonitis without any apparent source of contamination.
Enteric gram-negative organismE. coli most commonly encountered but sometime gram-positive organism such as streptococci and enterococci also responsible.