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: Medicine
The most commonly encountered bacterial pathogens in the lungs of patients with cystic fibrosis are: 
Select and explain. 
A. E. coli and alpha Streptococcus, B. E. coli and Pseudomonas, C. Staphylococcus and Proteus, D. Staphylococcus and Pseudomonas
D: Staphylococcus and Pseudomonas
Answer: D: Staphylococcus and Pseudomonas 
Explanation: For reasons that still are not understood, the most common bacterial organisms infecting the lungs of children with cystic fibrosis are Staphylococcus aureus and Pseudomonas aeruginosa. This has not changed much in the past two decades despite major changes in our antibiotic usuage. Pseudomonas is paicularly difficult to eradicate despite sensitivity in vitro to a variety of antibiotics.