What question did this study set out to answer?

The study aims to understand the patterns of colonization by H. influenzae and P. aeruginosa in non-cystic fibrosis bronchiectasis patients.

February 19, 2026Open Access

Epidemiological insights into Haemophilus influenzae and Pseudomonas aeruginosa persistent colonization in non-cystic fibrosis bronchiectasis patients: a longitudinal and multicenter study

Key Points

The study aims to understand the patterns of colonization by H. influenzae and P. aeruginosa in non-cystic fibrosis bronchiectasis patients.
Isolated bacterial strains from bronchiectasis patients across three visits and exacerbation episodes.
Performed antimicrobial susceptibility tests and phenotyping assays.
Applied whole genome sequencing to analyze resistance determinants and genetic diversity.
31 patients were colonized by H. influenzae, 28 by P. aeruginosa, and 3 were co-colonized.
P. aeruginosa was linked to 70.6% of severe cases and H. influenzae to 81.8% of exacerbations.
High genetic diversity found in bacterial strains, with specific sequence types dominating.
Low overall antimicrobial resistance noted, but H. influenzae had 40.4% resistance to cotrimoxazole.
Persistent colonization was observed in 25.8% of patients.

Abstract

Abstract Background Bronchiectasis is a chronic respiratory disease characterized by recurrent exacerbations and persistent inflammation, often associated with bacterial pathogens such as Haemophilus influenzae and Pseudomonas aeruginosa . Phenotypic adaptations (e.g., antimicrobial resistance) complicate treatment and worsen a patient’s quality of life. Methods Between 2019 and 2020, we isolated 52 H. influenzae and 48 P. aeruginosa strains from 62 non-CF bronchiectasis patients across three scheduled visits and during exacerbation episodes. Antimicrobial susceptibility (assessed by microdilution) and phenotyping assays (motility and hypermutability) were performed. Whole genome sequencing was applied for analyses of resistance determinants, virulence factors, and genetic diversity. Results Of the 62 patients, 31 were colonized by H. influenzae , 28 by P. aeruginosa , and 3 were co-colonized. Severe disease was predominantly linked to P. aeruginosa (70.6%), while exacerbations were more common with H. influenzae (81.8%). Multilocus sequence typing (MLST) revealed high genetic diversity, with ST1025 and ST253 most common in H. influenzae and P. aeruginosa , respectively. Antimicrobial resistance was low, but H. influenzae showed the highest resistance to cotrimoxazole (40.4%), while P. aeruginosa showed high resistance to aminoglycosides (27.1%) and fluoroquinolones (25%). Virulence profiling of P. aeruginosa identified 22.9% of strains as hypermutable, 27.1% as mucoid, 31.3% harboring the exoU gene, and 41.7% with impaired twitching motility. Persistent colonization occurred in 16 patients (25.8%), with antimicrobial resistance emerging following previous antimicrobial treatment in one case. Conclusions In this cohort, H. influenzae and P. aeruginosa showed similar prevalence, high genetic diversity, and rare co-colonization. P. aeruginosa was associated with more severe disease, higher antimicrobial resistance, and hypermutability, whereas H. influenzae was associated with acute exacerbations.

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