Abstract
OBJECTIVES: Pseudomonas aeruginosa is the most common pathogen in the bronchiectasis lung, associated with worsened outcomes. P. aeruginosa genomic studies in this context have been limited to single-country, European studies. We aimed to determine strain diversity, adaptation mechanisms, and AMR features to better inform treatment. METHODS: P. aeruginosa from 180 bronchiectasis patients in 15 countries, obtained prior to a phase 3, randomised clinical trial (ORBIT-3), were analysed by whole-genome sequencing. Phylogenetic groups and sequence types were determined, and between versus within patient genetic diversity compared using Analysis of Molecular Variance (AMOVA). The frequency of AMR-associated genes and mutations was also determined. RESULTS: A total of 2854 P. aeruginosa isolates were analysed, predominantly belonging to phylogenetic group 1 (83%, n = 2359). Genetic diversity was far greater between than within patients, responsible for >99.9% of total diversity (AMOVA: phylogroup 1: df = 145, P < 0.01). Numerous pathways were under selection, some shared with CF (e.g., motility, iron acquisition), some unique to bronchiectasis (e.g., novel efflux pump PA1874). Multidrug resistance features were also frequent. CONCLUSIONS: We present a 10-fold increase in the availability of genomic data for P. aeruginosa in bronchiectasis, highlighting key distinctions with cystic fibrosis and potential targets for future treatments.