PERSISTENCE OF HAEMOPHILUS INFLUENZAE AND PSEUDOMONAS AERUGINOSA STRAINS IN BRONCHIECTASIS PATIENTS: A LONGITUDINAL STUDY

Bronchiectasis (BQ) is a chronic respiratory condition characterized by a widening of the bronchial airways, leading to inflammation and recurrent exacerbations. Inflammation is frequently associated with gram-negative microorganisms, particularly Haemophilus influenzae and Pseudomonas aeruginosa , which are the main pathogens causing chronic infections. This study aimed to describe long-term bacterial persistence and antimicrobial resistance levels in non-cystic fibrosis bronchiectasis (non-CF-BQ). The study involved seven Spanish hospitals (2019-2020). Strains were isolated in routine visits (V0=initial; V1=6m; V2=12m) and exacerbations (Fig.1). Persistence was defined as the same clone found over three months apart. All strains were tested for antimicrobial susceptibility and hypermutability in P. aeruginosa . Finally, whole genome sequencing was performed using Illumina Miseq/NextSeq platforms, with mutations identified using Geneious software. A total of 62 patients were included in the study. Of these, 31 patients harboured H. influenzae , 28 had P. aeruginosa and three patients had both microorganisms. Eighteen exacerbation episodes were identified: H. influenzae was isolated in nine episodes (9/18; 50%), P. aeruginosa in two (2/18; 11.1%), Streptococcus pneumoniae in two (2/18; 11.1%) and commensal microbiota in the remaining episodes. Persistent colonization was observed in 16 patients (Fig. 1): seven with H. influenzae (7/16; 43.8%) and nine with P. aeruginosa ( 9/16; 56.2%). Notably, six (6/7; 85.7%) patients with persistent H. influenzae had exacerbation episodes, compared to only two (2/9; 22.2%) with P. aeruginosa . Antimicrobial resistance rates showed no statistical significance between persistent and non-persistent strains (Figure 1). However, four patients acquired antimicrobial resistance during the longitudinal study, in two cases, after an exacerbation. Patient HUGTiP-P09 developed aminoglycoside resistance, this patient received nebulized antimicrobial treatment since visit 0 due to chronic P. aeruginosa infection. For patient HM-P09, moxifloxacin was successfully used to treat an exacerbation caused by an sporadic P. aeruginosa clone (ST4386), but led to fluoroquinolone resistance in the persistent P. aeruginosa clone (ST2555). Two patients with persistent P. aeruginosa harboured hypermutable strains (2/16; 12.5%). Persistent colonization was more frequently observed in P. aeruginosa , while exacerbations were more commonly related to H. influenzae . Antimicrobial treatment for exacerbations led to the acquisition of antibiotic resistance in persistent strains.