What is protracted bacterial bronchitis (PBB)?

From the Guidelines

Protracted bacterial bronchitis (PBB) is a chronic respiratory condition characterized by a persistent wet cough lasting more than four weeks that responds to antibiotic treatment, primarily affecting young children but can occur in adults as well. The condition develops when bacteria colonize the airways, causing inflammation and excessive mucus production. The most common bacteria involved include Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis, as reported in a study published in Chest in 2017 1.

Key Characteristics of PBB

• Persistent wet cough lasting more than four weeks
• Responds to antibiotic treatment
• Common bacteria involved: Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis
• Diagnosis requires excluding other causes of chronic cough such as asthma, cystic fibrosis, or foreign body aspiration

Treatment of PBB

• Treatment usually involves a 2-week course of antibiotics, with amoxicillin-clavulanate (Augmentin) being the first-line choice at a dose of 45 mg/kg/day divided twice daily for children or 875 mg twice daily for adults, as recommended by the Chest guideline and expert panel report in 2017 1.
• In cases of penicillin allergy, alternatives include azithromycin or clarithromycin
• Some patients may require longer courses of antibiotics or repeated treatments for recurrent episodes

Complications and Supportive Measures

• If left untreated, PBB can potentially lead to bronchiectasis, a condition involving permanent airway damage
• Supportive measures include adequate hydration to thin secretions and chest physiotherapy to help clear mucus from the airways
• The condition is believed to develop due to impaired mucociliary clearance, which allows bacteria to establish biofilms in the airways, making them resistant to normal immune clearance mechanisms, as suggested by a study published in Chest in 2017 1.

Diagnosis and Referral

• Diagnosis typically requires excluding other causes of chronic cough
• Further investigations, such as flexible bronchoscopy with quantitative cultures and sensitivities with or without chest computed tomography, should be undertaken when the wet cough persists after 4 weeks of appropriate antibiotics 1
• Referral to a specialist may be necessary for further evaluation and management.

From the Research

Definition and Characteristics of Protracted Bacterial Bronchitis

• Protracted bacterial bronchitis (PBB) is a common cause of chronic wet cough in preschool children with no symptoms or signs of other specific causes 2.
• It is characterized by a chronic wet or productive cough without signs of an alternative cause and responds to 2 weeks of appropriate antibiotics, such as amoxicillin-clavulanate 3.
• The diagnosis is mainly clinical, and generally, no instrumental examinations are necessary 2.

Pathogenesis and Risk Factors

• The most common bacteria found in the bronchoalveolar lavage (BAL) of subjects with PBB include Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis 2, 3.
• Airway malacia is commonly found in children with PBB, but there is no correlation with any type of immunodeficiency 2, 3.
• Childcare attendance, prior history of chronic cough, and age <2-years increase the risk of PBB 4.
• Baseline diagnoses of asthma/reactive airways disease or bronchiolitis decrease the risk of PBB 4.

Treatment and Outcomes

• Amoxicillin-clavulanate acid is the most commonly used antibiotic, and prolonged therapy (longer than 2 weeks) is sometimes required to achieve cough resolution 2, 3.
• The duration of initial antibiotic treatment is associated with recurrent relapse in PBB, with longer treatment durations (6 weeks) reducing the likelihood of recurrent PBB 5.
• Recurrent PBB (>3 episodes/years) and the presence of H. influenzae infection in the lower airways seem to be significant risk factors for developing bronchiectasis 2, 3.