ETD

• pediatric patiens
• primary ciliary dyskinesia
• Pseudomonas aeruginosa

Background. Primary Ciliary Dyskinesia (PCD) is characterized by impaired mucociliary clearance, recurrent respiratory infections and progressive structural lung disease. Although microbiological surveillance is an important component of routine PCD care, the relationship between upper- and lower-airway bacterial detection remains poorly characterized. This study evaluated the distribution of Pseudomonas aeruginosa (PA), Staphylococcus aureus (SA) and Haemophilus influenzae (HI) across airway compartments and their correlations with clinical phenotype and genotype.
Methods. We conducted a pilot observational study including patients with genetically characterized PCD, undergoing routine follow-up evaluation at our PCD reference center between May 2025 and June 2026, who underwent recent medical history taking, physical examination, spirometry and nasal and oropharyngeal swabs and sputum or lower-airway aspirate samples Microbiological concordance was defined as detection of the same microorganism in the lower airways and in at least one upper-airway sample. The prevalence and distribution of PA, HI and SA were assessed according to age and sampling site, and associations with lung function, bronchiectasis, pansinusitis were explored.
Results. A total of 176 patients were included, comprising 128 adults and 48 children. Bronchiectasis was more frequent in adults than in children (93.7% vs 76.9%, p=0.006), and adults had significantly lower mean FEV₁ z-scores (−1.97±1.49 vs −1.25±1.52, p=0.008). Lower-airway PA positivity was substantially more frequent in adults than in children (47.7% vs 14.6%, p<0.001), whereas HI was more frequent in children (31.2% vs 15.6%, p=0.033); SA prevalence was similar between groups (31.2% vs 28.9%, p=0.853). Upper/lower-airway concordance was highest for SA, particularly in children (93.3%), followed by HI in children (73.3%), whereas PA concordance was approximately 50% in both age groups. PA positivity increased significantly with age (OR 1.53 per 10-year increase, 95% CI 1.25–1.86; p<0.001), whereas HI decreased with age (OR 0.72, 95% CI 0.56–0.93; p=0.011). Patients with lower-airway PA positivity had a higher prevalence of bronchiectasis (98.5% vs 83.5%, p=0.001) and poorer lung function (FEV₁ z-score −2.47±1.57 vs −1.31±1.32, p<0.001) than PA negative patients. Concordant upper- and lower-airway PA detection was not associated with further impairment of lung function or greater structural disease compared with lower-airway PA positivity alone. Significant associations were not observed for SA or HI.
Conclusions: Airway microbiology shows age- and pathogen-specific patterns in patients with PCD. PA positivity becomes progressively more frequent with age and is associated with worse lung function and bronchiectatic disease, whereas HI predominates earlier in life while SA shows a more stable distribution. Upper-airway sampling reflects lower-airway microbiology to a variable extent and may provide clinically useful information, particularly for SA and HI, although upper-airway PA detection does not appear to identify a more severe phenotype. However, the upper airways may represent a reservoir for the pathogens, and for PA in particular: therefore, PA positivity at this level should be sought and could represent a future target for the management of chronic infected patients.