It is now known that the bronchi and lungs are usually not completely sterile. It is thought that, like the gut where intestinal bacteria live, bacterial colonies (flora) in the bronchial lungs may form biofilms that are normally in balance with the ciliated cells of the bronchi and the immune cell population. However, if the immune system is weak from birth, if the cilia of the bronchial wall cells are poorly functioning, or if the recovery of the bronchial wall cells is delayed by a cold, the power relationship with the bacterial flora may deteriorate, leading to a chronic state of inflammation.
Adults PBB develop a persistent cough when affected by a preceding respiratory viral infection. The duration of cough illness ranged from 1.4 to 8.5 months (median 3 months), with many lasting more than 8 weeks. Characteristic symptoms are a very expectorant cough, yellow sputum (often despite no detectable pathogens in particular) (the result of neutrophilic airway inflammation and increased sputum lymphocytes) and a sensation of sputum stuck in the throat that is difficult to remove. These symptoms are considered useful for clinical diagnosis.
On the other hand, unlike asthma, wheezing is not present and is not seasonal. Radiological bronchiectasis is not present. It is defined by the absence of other causes of chronic cough such as asthma, COPD or smoking.
The majority of patients were female (as with bronchiectasis and chronic cough, which is associated with gender differences in cough reflex sensitivity) and predominantly middle-aged (late 40s to late 60s).
Some reports suggest that 28% of adult PBBs subsequently had radiological bronchiectasis, suggesting that PBB and bronchiectasis may represent different parts of the same underlying process of endobronchial infection and inflammation.
Clinical characteristics of protracted bacterial bronchitis in adults
Persistent bacterial bronchitis in adults – a precursor to bronchiectasis?