Polymicrobial airway bacterial communities in adult bronchiectasis patients

Abstract

BackgroundChronic airway infection contributes to the underlying pathogenesis of non-cystic fibrosis bronchiectasis (NCFBr). In contrast to other chronic airway infections, associated with COPD and CF bronchiectasis, where polymicrobial communities have been implicated in lung damage due to the vicious circle of recurrent bacterial infections and inflammation, there is sparse information on the composition of bacterial communities in NCFBr. Seventy consecutive patients were recruited from an outpatient adult NCFBr clinic. Bacterial communities in sputum samples were analysed by culture and pyrosequencing approaches. Bacterial sequences were analysed using partial least square discrimination analyses to investigate trends in community composition and identify those taxa that contribute most to community variation.ResultsThe lower airway in NCFBr is dominated by three bacterial taxa Pasteurellaceae, Streptococcaceae and Pseudomonadaceae. Moreover, the bacterial community is much more diverse than indicated by culture and contains significant numbers of other genera including anaerobic Prevotellaceae, Veillonellaceae and Actinomycetaceae. We found particular taxa are correlated with different clinical states, 27 taxa were associated with acute exacerbations, whereas 11 taxa correlated with stable clinical states. We were unable to demonstrate a significant effect of antibiotic therapy, gender, or lung function on the diversity of the bacterial community. However, presence of clinically significant culturable taxa; particularly Pseudomonas aeruginosa and Haemophilus influenzae correlated with a significant change in the diversity of the bacterial community in the lung.ConclusionsWe have demonstrated that acute exacerbations, the frequency of exacerbation and episodes of clinical stability are correlated, in some patients, with a significantly different bacterial community structure, that are associated with a presence of particular taxa in the NCFBr lung. Moreover, there appears to be an inverse relationship between the abundance of P. aeruginosa and that of of H. influenzae within the NCFBr lung bacterial community. This interaction requires further exploration.

Pediatric bronchiectasis: No longer an orphan disease

“…In contrast, another study reported no correlation between clinical parameters and microbiota, with bacterial load and composition unchanged by antibiotic treatment of exacerbations . Based on culture and pyrosequencing of sputum from adults with bronchiectasis, another study found the exacerbation frequency and episodes of clinical stability were associated in some patients with significantly different bacterial community structures . However, this study was cross‐sectional and suffered from limited resolution provided by pyrosequencing where individual species cannot be identified.…”

“…Three adult‐based studies highlighted the abundance of anaerobic bacteria and the complex microbiota within the lungs of bronchiectasis patients . Bacterial community composition positively correlated with forced expiratory volume in 1 sec (FEV 1 ), neutrophil count and cough score .…”

Geographic variation in the aetiology, epidemiology and microbiology of bronchiectasis

“…Other bacterial genera described in bronchiectasis airways include Streptococcus, Prevotella, Veillonella and Staphylococcus [65][66][67]. P. aeruginosa is associated with poorer pulmonary function, higher hospitalisation rates and greater morbidity and mortality compared to H. influenzae [68][69][70][71][72][73][74][75][76][77][78].…”

Research priorities in bronchiectasis: a consensus statement from the EMBARC Clinical Research Collaboration

“…Haemophilus influenzae and P. aeruginosa are the most commonly isolated organisms in several European studies using aerobic selective cultures, although no organisms are isolated in 23-27% of patients [9,17,36,37]. New methods to study lung microbiota have found that the diversity of airway infection is underestimated, with anaerobic bacteria found in up to 83% of sputum samples, and that three taxa, Streptococcaceae, Pseudomonadaceae and Pasturellaceae, seem to be dominant [38].…”