This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics, Subject name: Medicine
In a patient with cystic fibrosis, high fever with productive cough. Most common causative organism is 
Select and explain. 
A. Pseudomonas aerugenosa, B. H influenzae, C. Staph aureus, D. Streptococcus
A: Pseudomonas aerugenosa
Answer: A: Pseudomonas aerugenosa 
Explanation: Pseudomonas aeruginosa is the key bacterial agent of cystic fibrosis (CF) lung infections, and the most impoant pathogen in progressive and severe CF lung disease. Once these sticky biofilms are formed, inflammation results and, in some cases, leads to chronic infections that can last for months or years with productive cough and fever Ref Robbins 9/e pg 178