Relationship between antibiotic treatment and clinical outcome in people with bronchiectasis

Bacterial load correlates with airway inflammation and exacerbation risk, supporting the use of long-term inhaled antibiotics. While microbial culture remains the gold standard for pathogen quantification, molecular methods such as quantitative PCR (qPCR) and next-generation sequencing (NGS) offer promising alternatives for assessing microbiological efficacy.<br><br>This thesis aimed to: (i) validate qPCR assays for respiratory pathogen detection and quantification; (ii) evaluate the impact of inhaled antibiotics on sputum bacterial density and clinical outcomes in BE; (iii) assess qPCR and NGS for monitoring microbial changes post-treatment; and (iv) determine the effect of saponin processing on microbial DNA recovery.

Total bacterial, Pseudomonas aeruginosa, and Haemophilus influenzae densities were measured using qPCR in sputum samples from clinical trials, with microbial composition assessed via 16S rRNA sequencing.<br><br>Treatment with tobramycin inhalation powder (TIP) and liposomal ciprofloxacin significantly reduced P. aeruginosa density, measured by quantitative culture, by >3.5 and >1.5 log₁₀ CFU/mL, respectively. Molecular analysis also revealed that TIP decreased total bacterial density and P. aeruginosa density and relative abundance, while promoting a more diverse lung microbiota.