Clinical Characteristics, Microbiological Profile, and Antimicrobial Resistance of Pseudomonas aeruginosa in Hospitalized Patients with Bronchiectasis: A 10-Year Single- Center Cohort Study

Background. Pseudomonas aeruginosa (PA) is the most clinically significant respiratory pathogen in patients with bronchiectasis, yet data from mainland China on PA colonization, antimicrobial resistance, and its impact on hospitalization outcomes remain limited. We aimed to characterize the clinical and microbiological profile of PA among hospitalized patients with bronchiectasis over a 10-year period. Methods. We conducted a retrospective cohort study of all adult patients hospitalized with a primary diagnosis of bronchiectasis at Beijing Chaoyang Hospital, a tertiary referral respiratory center in China, between January 2014 and December 2024. Clinical, radiological, laboratory, and microbiological data were extracted from the electronic hospital information system. Respiratory samples were cultured using standard microbiological methods; antimicrobial susceptibility testing was performed by the clinical microbiology laboratory. Patients were classified as PA-positive or PA-negative on the basis of respiratory culture results. Comparisons between groups used the Mann-Whitney U test for continuous variables and the chi-square test for categorical variables. Multivariable logistic regression identified factors independently associated with PA colonization. Results. Among 7787 hospital admissions from 2,503 unique patients (mean age 59.9 ± 13.4 years; 56.4% female), 942 admissions (29.2%) underwent respiratory culture. PA was the dominant pathogen, isolated in 338 of 942 cultured admissions (35.9%), followed by Klebsiella pneumoniae (3.0%), Acinetobacter baumannii (2.4%), and Aspergillus spp. (6.2%). PA-positive admissions were younger (median 60 vs. 64 years), had longer hospitalization (12 vs. 11 days), higher white blood cell counts (7.28 vs. 6.56 × 10⁹/L), higher platelet counts, and higher PaCO2 (51 vs. 44 mmHg) than PA-negative admissions (all p < 0.05). In multivariable analysis, CT-documented bronchiectasis (adjusted OR 1.64, 95% CI 1.19–2.24) and higher WBC count (adjusted OR 1.06 per unit, 95% CI 1.02–1.10) were independently associated with PA colonization, whereas older age was protective (adjusted OR 0.98, 95% CI 0.97–0.99). Among 821 PA isolates with comprehensive susceptibility testing, 20.0% were multidrug-resistant, 26.4% were carbapenem-resistant, and 25.0% were fluoroquinolone-resistant; amikacin and tobramycin retained the highest susceptibility rates (90.4% and 93.8%, respectively). CT-documented bronchiectasis was also the strongest predictor of recurrent hospitalization (adjusted OR 3.17, 95% CI 2.46–4.07). Conclusions. PA is the predominant respiratory pathogen among hospitalized patients with bronchiectasis in Beijing, associated with more extensive structural lung disease, higher systemic inflammation, worse ventilatory function, and prolonged hospitalization. The substantial rates of carbapenem and fluoroquinolone resistance underscore the need for systematic surveillance and antibiotic stewardship in this population.