Professional · Issue 1 · 2026-09-24
Inhaled Antibiotics in CF: Registry Evidence Suggests Diminishing Returns and Emerging Risks in the Modulator Era
Editorially reviewed research summaries, context, and limitations.
Marianne S Muhlebach, Jane She, John J LiPuma, et al.
Summary: Using US CF Foundation Patient Registry data from 2011–2019, this study examined whether the benefits and risks of chronic inhaled antibiotic therapy have shifted alongside the introduction of CFTR modulators. Using inverse probability treatment weighting and generalized estimating equations across roughly 12,000–16,000 people with CF (pwCF) annually, the authors found that inhaled antibiotics were associated with increased risks of Aspergillus, Stenotrophomonas maltophilia, and Achromobacter infections. The lung-function benefit of inhaled antibiotics was present only in pwCF with chronic Pseudomonas aeruginosa (Pa) infection, was absent or negative in Pa-negative pwCF, and diminished progressively across successive CFTR-modulator eras.
Why it matters: Chronic inhaled antibiotics have been a cornerstone of CF pulmonary management for decades, but the therapeutic landscape has changed dramatically with the advent of highly effective modulator therapy (HEMT). This study provides registry-scale evidence that the benefit-risk calculus for inhaled antibiotics may need recalibration — particularly for Pa-negative patients, who appear to bear infection risk without lung-function benefit, and for patients on modulators, whose Pa burden and baseline lung function have improved substantially. These findings carry direct implications for prescribing practice, guideline development, and the design of future comparative-effectiveness studies.
Expert perspective: This is a methodologically serious registry study tackling a clinically important and underexplored question. The sample is large, nationally representative within the US CF population, covers nine years spanning three modulator eras, and employs inverse probability treatment weighting to address treatment-selection bias. Leeds criteria for Pa infection status add rigor to the exposure stratification.
That said, several limitations deserve explicit acknowledgment. The study period ends in 2019, predating the widespread uptake of elexacaftor/tezacaftor/ivacaftor (ETI) — the modulator combination that has most dramatically altered Pa prevalence, lung function trajectories, and exacerbation rates. The three modulator eras studied represent a period of partial and heterogeneous modulator access, and the trajectory of diminishing antibiotic benefit may steepen considerably in the ETI era. Extrapolating these findings to current practice therefore requires caution.
The observational design, even with weighting, cannot fully eliminate confounding by indication. Physicians prescribing inhaled antibiotics to Pa-negative patients may be responding to clinical signals incompletely captured in registry fields. The association between inhaled antibiotics and Aspergillus or gram-negative co-infections is biologically plausible — antibiotics alter airway microbiome composition and may select for fungi and intrinsically resistant organisms — but causality cannot be established from these data. Reverse causation is also possible. The finding that Pa-negative pwCF prescribed inhaled antibiotics had worse lung function trajectories is clinically concerning but particularly susceptible to residual confounding, as this group likely contains patients prescribed antibiotics for reasons not well captured in registry data.
The clinical bottom line is pragmatically important: for pwCF who have eradicated or never acquired chronic Pa — a growing proportion in the modulator era — continued prescription of inhaled antibiotics deserves active reassessment rather than reflexive continuation. For those with chronic Pa, the benefit appears to persist but to be attenuating. This study will not by itself change guidelines, but it builds a credible evidential case for prospective trials or updated registry analyses incorporating ETI-era data to guide deprescribing decisions.
Relevance: Cystic Fibrosis | CF Registry and Real-World Evidence
Source: https://pubmed.ncbi.nlm.nih.gov/42767597/
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