Bacterial colonisation of lower airways in health and chronic lung disease

To evaluate the colonisation rate and type in different groups of patients with chronic lung diseases, bronchial lavage (BL) fluid was investigated for bacteria.

All patients underwent fibre-optic bronchoscopy as part of routine investigation for remote haemoptysis or nodule investigation. The standard procedure included BL and microbiological culture providing the total number of colony forming units (cfu)/mL and the number of potential pathogenic bacteria (ppb)/mL. Three groups of patients were included: 48 persons had a final diagnosis of no pathology, 53 patients with chronic obstructive pulmonary disease in a stable phase and 32 patients with a final diagnosis of bronchiectasis.

The median number of cfu cultured from patients with bronchiectasis was 10(5) cfu/mL compared to 5 10(3) cfu/mL in patients with COPD and 10(4) cfu/mL in persons with no pathology. The ppb colonisation rate varied from 10% in persons with no pathology to 43% in patients diagnosed with chronic obstructive pulmonary disease (COPD) and 63% in patients with bronchiectasis. The most frequent bacteria isolated was Haemophilus influenzae. Colonisation rates were associated with frequencies of respiratory infections; patients with bronchiectasis reported a median of three infections per year, patients with COPD reported one infection per year, and persons without pathology reported 0 infections per year (P < 0.05). Within each group a large patient-to-patient variation was found.

Different groups of patients with chronic pulmonary diseases have very different colonisation rates. Patients with bronchiectasis have the highest colonisation rate. This correlates to the reported frequency of lower respiratory tract infections.