Final answer:
Pseudomonas aeruginosa is the primary bacteria that typically causes pneumonia in patients with cystic fibrosis, often leading to serious infections and being a major cause of mortality due to chronic lung damage.
Step-by-step explanation:
The number one bacteria that typically causes pneumonia in patients with cystic fibrosis is Pseudomonas aeruginosa. This opportunistic pathogen is known for causing serious cases of bacterial pneumonia in these patients due to its ability to thrive in the thick, excess mucus characteristic of cystic fibrosis. The genetic defect in the cystic fibrosis transmembrane receptor (CFTR) leads to the accumulation of dried mucus in the lungs, which decreases the efficiency of the mucociliary escalator, allowing P. aeruginosa to infect and adapt to the conditions in the patient's lungs. It is known to affect more than half of all patients with cystic fibrosis and leads to lung damage due to chronic inflammatory response, which is the leading cause of mortality in these patients.