Abstract Rationale Chronic airway colonization—particularly with gram-negative bacteria (GNB), including Pseudomonas aeruginosa (PA)—is a key driver of exacerbations, symptoms, and disease progression in bronchiectasis. Long-term therapy with inhaled antibiotics or macrolides is commonly used in high-risk patients, but real-world comparative data in Asian populations remain limited. Methods In this prospective, multicenter observational cohort, adults (≥20 years) with computed tomography (CT)-confirmed bronchiectasis, a history of GNB isolation, and high-risk features (≥2 exacerbations or ≥ 1 severe exacerbation in the prior 24 months, or bronchiectasis severity index BSI ≥9) were enrolled. Patients received either inhaled colistin or oral azithromycin for 3 months. The primary outcome was change in microbiological culture results. Secondary outcomes included changes in COPD Assessment Test (CAT) and modified Medical Research Council (mMRC) dyspnea scores, lung function, and safety. Results Eighty-five patients were analyzed (colistin n = 51; azithromycin n = 34). At baseline, the colistin group had higher symptom burden and worse lung function. After 3 months, GNB culture positivity declined more markedly in the colistin group, resulting in higher clearance rates (64.7% vs 29.4%, p=0.001)(Figure 1A). In the PA subgroup, clearance was also higher with colistin (33.3% vs 11.8%, p=0.039) (Figure 1B). No significant between-group differences were observed in ΔFEV₁ or ΔFVC (p=0.136)(Figure 1C). Symptom improvement was greater with colistin: median CAT score change −4.0 vs 0.4 (p0.001) and a higher proportion achieved a clinically meaningful CAT improvement ≥4 points (52.9% vs 26.5%, p=0.016) (Figure 1D). Adverse events were infrequent and mild (e.g., skin rash), with no serious treatment-related events. Conclusion In high-risk bronchiectasis patients with prior GNB infection, long-term inhaled colistin was associated with greater microbiological clearance and clinically meaningful symptom improvement compared with azithromycin, while lung function remained stable in both groups. These real-world multicenter data support the integration of inhaled antibiotics into bronchiectasis management strategies in Asian settings. This abstract is funded by: This research was funded by the Ministry of Science and TechnNational Taiwan University Hospital, Yun-Lin Branch, Taiwan
Chen et al. (Fri,) studied this question.