Cystic fibrosis patients are frequently chronically colonized by which bacterium?

• A. Staphylococcus aureus
• B. Pseudomonas aeruginosa
• C. Haemophilus influenzae
• D. Burkholderia cepacia

Answer: (B)

Chronic airway infection in cystic fibrosis is dominated by Pseudomonas aeruginosa. The thick, sticky mucus in CF impairs clearance, and Pseudomonas is highly adaptable, often evolving a mucoid biofilm–producing form that resists antibiotics and immune defenses. This combo lets it persist as a long-term colonizer and drives progressive lung decline. Other bacteria like Staphylococcus aureus and Haemophilus influenzae are common early infections, but they are less likely to remain as lifelong colonizers. Burkholderia cepacia can occur and poses serious prognosis and infection-control concerns, but it is less frequently the chronic colonizer compared with Pseudomonas aeruginosa.