Effect of lower airway bacterial colonisation on time to acute exacerbation in patients with COPD

Lower airway bacterial colonisation (LABC) is associated with increased exacerbation frequency in COPD patients. We hypothesised that time to next exacerbation would be dependent on their stable LABC status, individual colonising species and total bacterial load. Sputum samples collected from stable COPD patients were analysed by qPCR to detect H. influenzae, M. catarrhalis and S. pneumoniae. Patients were sub-grouped by LABC status, colonising species and by high or low total bacterial load, using a cut-off of 10⁷ cfu/ml (Singh et al., 2014). Patients prospectively completed daily symptom diary cards to determine time to next exacerbation over a 180-day period using validated symptomatic criteria (Seemungal et al., 1998). 148 COPD patients were included, of whom LABC was detected in 62 (42%). 82 (55%) patients experienced an exacerbation within 180 days. Median time to next exacerbation was significantly shorter in patients with high total bacterial load (n=33) compared with those with low total bacterial load (n=29) (52 [29-74] vs. 85 [62-113] days, p=0.016, Figure 1). There was no significant difference in time to next exacerbation between non-LABC and LABC patients (p=0.737) or by colonising species (p=0.187). Stable COPD patients with high airway total bacterial load have a shorter time to next exacerbation and should be targeted in future interventional studies to prevent exacerbations.