The species-specific inflammatory response of colonising bacteria in stable COPD

Potentially pathogenic micro-organisms (PPMs) are frequently isolated from stable COPD patients. We hypothesised that the degree of airway & systemic inflammation is dependent on species of PPM. Sputa & sera collected from stable patients in the London COPD Cohort were analysed by qPCR to detect H. influenzae (HI) , M. catarrhalis (MC) and S. pneumoniae (SP), ELISAs for airway IL-8, IL-1β & MPO, & sera CRP was measured. 183 paired sputa & sera from 99 stable patients were included. Clinical characteristics are shown in Table 1. View this table: Baseline Characteristics n=99 PPMs were detected in 64/183 of sputa. HI & SP were equally prevalent & there was no significant difference between their loads (p=0.49). MC load was significantly higher than both HI (p<0.001) & SP (p=0.001). Patients with lower airway bacterial colonisation (LABC) by any PPM had significantly higher airway cytokines than non-LABC patients (all p<0.001). HI-colonised but not SP- or MC-colonised patients had significantly higher airway cytokines than non-LABC patients (all p<0.05, Figure 1). There was no significant difference between CRP in non-LABC & LABC patients, or between non-LABC patients & different PPMs. ![Figure][1] LABC patients have higher airway, but not systemic inflammation, & this is associated with HI. Targeting HI in stable COPD may potentially help to decrease airway inflammation. [1]: pending:yes