Airway Microbiome of Patients With Protracted Bacterial Bronchitis

Interaction Between Microbiome, Virome and Host Immunity Response in the Context of Protracted Bacterial Bronchitis

This project aims to assess the relationship between the microbiome and virome composition, the immune responses, and the respiratory health of children with protracted bacterial bronchitis (PBB). In addition, we aim to evaluate how the standard treatment with azithromycin interacts with the components of the microbiome, virome and immune biomarkers.

Study Overview

• Status: Recruiting
• Conditions: Protracted Bacterial Bronchitis

Detailed Description

Protracted Bacterial Bronchitis (PBB) is an often underestimated disease, characterized by a persistent cough for more than four weeks, without other significant underlying symptoms. While generally treatable, it can lead to complications such as recurrent infections and airway damage (bronchiectasis). The reasons why some children develop PBB or subsequent complications while others do not remain unclear. Recent research suggests that an impaired immune response and microbiota dysbiosis may play a key role. This study aims to analyze the microbial and viral composition of the airways in children with PBB, its relationship with inflammation, and the effects of azithromycin. Oropharyngeal swabs will be collected from up to 160 children <5 years old diagnosed with PBB at UZA in a longitudinal setup during one year. At each routine consultation (five in total) and during an exacerbation episode, three oropharyngeal swabs will be collected from each child. The three swabs will be used to: (1) determine the microbiome composition using next-generation sequencing, (2) identify the virome composition using multiplex qPCR or similar approaches, and (3) quantify immune biomarkers (RNA and protein-level) and culture microbial isolates. These findings will help to better understand the role of the airway microbiome in young children with PBB and identify microorganisms that may have a pathogenic or protective role. Ultimately, this knowledge may contribute to the development of new and effective diagnostics and treatments for PBB from an early age.

• Study Type: Observational
• Enrollment (Estimated): 160

Contacts and Locations

• Study Contact: Name: Kim Van Hoorenbeeck, Prof. dr.; Phone Number: +3238213000; Email: kim.vanhoorenbeeck@uza.be
• Study Contact Backup: Name: Irina Spacova, Prof. dr. ir.; Phone Number: +3232653289; Email: irina.spacova@uantwerpen.be

Study Locations

• Belgium
  • Edegem, Belgium, 2650
    • Recruiting
    • Antwerp University Hospital
    • Contact: Kim Van Hoorenbeeck, Prof. dr.; Phone Number: +3238213000; Email: kim.vanhoorenbeeck@uza.be
    • Principal Investigator: Kim Van Hoorenbeeck, Prof. dr.

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: No

• Sampling Method: Probability Sample

Study Population

Children under five years old diagnosed with PBB.

Description

Inclusion Criteria:

• Children with PBB diagnosis according to case definition
• Consent form signed by parents or legal guardians

Exclusion Criteria:

• Comorbidities (HIV, asthma, chronic obstructive pulmonary disease, diabetes)
• Have had serious illnesses (meningitis, pneumonia, bacteremia, empyema, etc) in the previous three months, identified only at the time of enrollment.
• Have chronic respiratory conditions at the time of enrollment (non-PBB bronchiectasis not caused by PBB, CF, allergy, etc.).
• Having received mechanical ventilation.
• Having been hospitalized or used antibiotics in the previous three months at the time of enrollment.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Participants with Protracted bacterial bronchitis diagnostic; Children under five years old who attend pediatric outpatient visits or well-child visits at University Hospital Antwerp (UZA) and are diagnosed with Protracted bacterial bronchitis.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Analysis of respiratory microbiome composition	Description: Analysis of microbiome communities in airway samples will be performed using amplicon or shotgun sequencing to determine relative microbial abundances (in percentages) as the unit of measure, coupled with the use of bioinformatic tools for community structure analysis.	Baseline, 3 months, 6 months, 9 months, 12 months and during exacerbations
Prevalence of respiratory viruses	Description: Detection of respiratory viruses from airway samples using RT-qPCR. Unit of Measure: percentage of positive samples (in percentages).	Baseline, 3 months, 6 months, 9 months, 12 months and during exacerbations

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Immune biomarkers profiling in airway samples	Immunological profiling will be performed in airway samples by determining (1) cytokine concentrations based on protein-level analysis such as ELISA (pg/mL) and/or (2) differential gene expression based on RNA analysis (log fold-change or similar metric).	Baseline, 3 months, 6 months, 9 months, 12 months and during exacerbations
Correlates of respiratory microbiome	Description: Microbial profiles will be associated with demographic, epidemiological and clinical data collected through standardized questionnaires and clinical assessments to determine relevant correlates. Unit of Measure: Statistical association measure (e.g., correlation coefficients or similar).	Baseline, 3 months, 6 months, 9 months, 12 months and during exacerbations
Correlates of Protracted Bacterial Bronchitis	PBB events will be associated with demographic, epidemiological and clinical data collected through standardized questionnaires and clinical assessments to determine relevant correlates. Unit of Measure: Effect estimates (odds/prevalence/hazard ratios or similar).	Baseline, 3 months, 6 months, 9 months, 12 months and during exacerbations

Collaborators and Investigators

• Sponsor: University Hospital, Antwerp
• Investigators: Principal Investigator: Kim Van Hoorenbeeck, Prof. dr., University Hospital, Antwerp; Principal Investigator: Irina Spacova, Prof. dr. ir., Universiteit Antwerpen

Study record dates

Study Major Dates

• Study Start (Actual): January 7, 2026
• Primary Completion (Estimated): January 1, 2028
• Study Completion (Estimated): January 1, 2029

Study Registration Dates

• First Submitted: October 1, 2025
• First Submitted That Met QC Criteria: November 19, 2025
• First Posted (Actual): December 1, 2025

Study Record Updates

• Last Update Posted (Actual): March 19, 2026
• Last Update Submitted That Met QC Criteria: March 18, 2026
• Last Verified: September 1, 2025

More Information

Terms related to this study

• Keywords: microbiome; cough; Protracted Bacterial Bronchitis
• Additional Relevant MeSH Terms: Respiratory Tract Diseases; Respiration Disorders; Signs and Symptoms, Respiratory; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Cough
• Other Study ID Numbers: BUN B3002025000069

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: The metadata of participants in the study will be made available in a restricted access repository. For samples and data sharing, the researchers will work with the legal department to establish Material/Data Transfer Agreements. Sequencing data are available at the European Nucleotide Archive. Physical samples are their origin will be stored at the decentral hub of the Antwerp biobank.
• IPD Sharing Time Frame: After the completion of the study (intended in 2029) and before publication, sequences and related metadata will be deposited into the ENA database and made available indefinitely.
• IPD Sharing Access Criteria: After data deposition in ENA, the data will be publicly accessible to anyone using the ENA instructions https://www.ebi.ac.uk/ena/browser/downloading-data

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No