Pseudomonas infections persisting after CFTR modulators are widespread throughout the lungs and drive lung inflammation.

Cystic fibrosis transmembrane conductance regulator (CFTR) modulators improve the physiological defect causing cystic fibrosis, but the lungs of most people remain infected and inflamed. A leading hypothesis implicates damaged segments as the cause of persistent infection and predicts that mildly diseased segments within an individual's lungs will clear after treatment, whereas severely diseased segments will not. Our findings contradict this hypothesis. We used bronchoscopy to sample the least- and most-damaged lung segments in Pseudomonas aeruginosa (Pa)-infected individuals before modulators and returned to these same segments after 1.5 years. Surprisingly, we find an "all-or-none" infection clearance response: the most-diseased segments clear if any other lung segment in that person clears, and the least-diseased segments remain infected if others in that person do. Furthermore, neutrophilic inflammation completely resolves where Pa clears but remains elevated where Pa persists. These data indicate that post-modulator infections are not limited to severely diseased segments and that Pa infections drive persistent lung inflammation after modulators.