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
Most common contributory factor to respiratory failure in patients with cystic fibrosis is: 
Select and explain. 
A. H.Influenzae infection, B. Pseudomona infection, C. Associated hea failure, D. Hypokalemia
B: Pseudomona infection
Answer: B: Pseudomona infection 
Explanation: P. aeruginosa is the most common cause of gram-negative bacteremia in neutropenic patients and it is the most common contributing factor to respiratory failure in cystic fibrosis and is responsible for the majority of deaths among them. P. aeruginosa infection in burns is no longer a major problem. Ref: Harrison, E-18, P-1266.