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

Abstract

Lower airway colonisation with species of potentially pathogenic bacteria (PPB) is associated with defective bacterial phagocytosis, in monocyte-derived macrophages (MDMs) and alveolar macrophages, from tobacco smoke-associated chronic obstructive pulmonary disease (S-COPD) subjects. In the developing world, COPD among nonsmokers is largely due to biomass smoke (BMS) exposure; however, little is known about PPB colonisation and its association with impaired innate immunity in these subjects.

We investigated the PPB load ( Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Pseudomonas aeruginosa) in BMS-exposed COPD (BMS-COPD) subjects compared with S-COPD and spirometrically normal subjects. We also examined the association between PPB load and phagocytic activity of MDMs and lung function. Induced sputum and peripheral venous blood samples were collected from 18 healthy nonsmokers, 15 smokers without COPD, 16 BMS-exposed healthy subjects, 19 S-COPD subjects and 23 BMS-COPD subjects. PPB load in induced sputum and MDM phagocytic activity were determined using quantitative PCR and fluorimetry, respectively.

Higher bacterial loads of S. pneumoniae, H. influenzae and P. aeruginosa were observed in BMS-COPD subjects. Increased PPB load in BMS-exposed subjects was significantly negatively associated with defective phagocytosis in MDMs and spirometric lung function indices (p<0.05).

Increased PPB load in airways of BMS-COPD subjects is inversely associated with defective bacterial phagocytosis and lung function.