Airway Bacterial Load and Inhaled Antibiotic Response in Bronchiectasis

Oriol Sibila, Elena Laserna, Amelia Shoemark, Holly R. Keir, Simon Finch, Ana Rodrigo-Troyano, Lidia Perea, Mike Lonergan, Pieter C. Goeminne, James D. Chalmers (Lead / Corresponding author)

    Research output: Contribution to journalArticlepeer-review

    69 Citations (Scopus)
    219 Downloads (Pure)


    Rationale: The principal underlying inhaled antibiotic treatment in bronchiectasis is that airway bacterial load drives inflammation, and therefore antibiotic treatment will reduce symptoms.

    Objectives: To determine the relationship between bacterial load and clinical outcomes, assess the stability of bacterial load over time, and test the hypothesis that response to inhaled antibiotics would be predicted by baseline bacterial load.

    Methods: We performed three studies. Studies 1 and 2 were prospective studies including adults with bronchiectasis. Study 3 was a post hoc analysis of a randomized trial of inhaled aztreonam. A priori patients were divided into low (<10 5 cfu/g), moderate (10 5-10 6 cfu/g), andhigh bacterial load (≥10 7 cfu/g) using quantitative sputum culture.

    Measurements and Main Results: Bacterial load was a stable trait associated with worse quality of life and more airway inflammation in studies 1, 2, and 3. In study 3, patients with high bacterial load showed an improvement in the primary endpoint (Quality of Life-Bronchiectasis-Respiratory Symptoms Score at Week 4) in favor of aztreonam (mean difference of 9.7 points; 95% confidence interval, 3.4-16.0; P = 0.003). The proportion of patients who achieved an increase above the minimum clinically important difference was higher in the aztreonam group at Week 4 (63% vs. 37%; P = 0.01) and at Week 12 (62% vs. 38%; P = 0.01) only in high bacterial load patients.

    Conclusions: Improvement of quality of life with inhaled aztreonam was only evident in patients with high bacterial load. Bacterial load may be a useful biomarker of severity of disease and treatment response.

    Original languageEnglish
    Pages (from-to)33-41
    Number of pages9
    JournalAmerican Journal of Respiratory and Critical Care Medicine
    Issue number1
    Early online date21 May 2019
    Publication statusPublished - 1 Jul 2019


    • Airway inflammation
    • Inhaled aztreonam
    • QoL-B
    • Quality of life

    ASJC Scopus subject areas

    • Pulmonary and Respiratory Medicine
    • Critical Care and Intensive Care Medicine


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