Distinctive airway microbial ecology of smokers and asthmatics

Abstract

The airways of the lung carry microbiota that contribute to respiratory health1. The ecology of normal airway microbial communities, their responses to environmental events, and the mechanisms through which they cause or modify disease are poorly understood. Cigarette smoking is the dominant malign environmental influence on lung function, causing 11·5% of deaths globally2. Asthma is the most prevalent chronic respiratory disease worldwide3,4, but was uncommon 100 years ago5. The asthma pandemic is linked to urbanization, leading to considerations of protective microbiota loss (the “hygiene hypothesis”)6-8 and acquisition of strains that may damage the airway epithelia9. We therefore investigated oropharyngeal airway microbial community structures in a general population sample of Australian adults. We show here that airway bacterial communities were strongly organized into distinctive co-abundance networks (“guilds”), just seven of which contained 99% of all oropharyngeal operational taxonomic units (OTUs). Smoking was associated with diversity loss, negative effects on abundant taxa, profound alterations to network structure and marked expansion of Streptococcus spp.. These perturbations may influence chronic obstructive pulmonary disease10 (COPD) and lung cancer11. In contrast to smokers, the loss of diversity in asthmatics selectively affected low abundance but prevalent OTUs from poorly understood genera such as Selenomonas, Megasphaera and Capnocytophaga, without coarse scale network disruption. The results open the possibility that replacement of specific organisms may mitigate asthma susceptibility.