The pulmonary disease in CF is chronic and progressive. It is characterized by a cycle of inflammation and infection, which destroys lung tissue and leads to scarring. Patients with CF have a persistent cough and increased sputum production. Small airways are congested with thick mucus and colonized shortly after birth with Staphylococcus aureus and Haemophilus influenzae. The Haemophilus tends to be supplanted by a mucoid strain of Pseudomonas aeruginosa as the patient ages. Declining pulmonary function is the leading cause of morbidity and mortality in CF. The clinical microbiology laboratory is involved in identifying pulmonary pathogens and performing drug susceptibility testing.
Pulmonary exacerbations, characterized by an increase in cough, sputum production, and shortness of breath, are treated with a variety of antibiotics; however, it can be very difficult to completely eradicate the bacteria. This is thought to be due to the development of antibiotic-resistant bacteria, the presence of mucus and bacterial capsulation (both of which make drug penetration more difficult), and the development of bacterial biofilms.
