Bacterial load and defective monocyte-derived macrophage bacterial phagocytosis in biomass-smoke COPD

Lower airway colonisation with potentially pathogenic bacterial species (PPBs) is associated with defective bacterial phagocytosis, in monocyte-derived macrophages (MDMs) and alveolar macrophages, from tobacco-smoke associated COPD (S-COPD) subjects. In developing world, COPD among non-smokers is largely due to biomass-smoke (BMS) exposure. Yet, little is known about PPBs colonisation and its association with impaired innate immunity in these subjects.We investigated the PPBs load (Streptococcus pneumoniae, SP; Haemophilus influenzae, HI; Moraxella catarrhalis, MC; and Pseudomonas aeruginosa, PA) in BMS-exposed COPD (BMS-COPD) compared with S-COPD and spirometrically normal subjects. We also examined the association between load of PPBs with phagocytic activity of MDMs and lung function.Induced sputum and peripheral venous blood samples were collected from 18 healthy non-smokers, 15 smokers without COPD, 16 BMS-exposed healthy, 19 S-COPD and 23 BMS-COPD subjects. PPBs load in induced sputum and MDMs phagocytic activity were determined using qPCR and fluorimetry respectively.Higher bacterial load of SP, HI, and PA were observed in BMS-COPD. Increased PPBs load in BMS-exposed subjects was significantly negatively associated with defective phagocytosis in MDMs, and spirometric lung function indices (p<0.05).Increased load of PPBs in airways of BMS-COPD subjects is inversely associated with defective bacterial phagocytosis and lung function