Distinctive airway microbial ecology of smokers and asthmatics

BackgroundNormal airway microbial communities play a central role in respiratory health but are poorly characterized. Cigarette smoking is the dominant global environmental influence on lung function, and asthma has become the most prevalent chronic respiratory disease worldwide. Both conditions have major microbial components that are also poorly defined. MethodsWe investigated airway bacterial communities in a general population sample of 529 Australian adults. Posterior oropharyngeal swabs were analysed by sequencing of the 16S rRNA and methionine aminopeptidase genes. The microbiota were characterised according to their prevalence, abundance, and network memberships. FindingsMicrobial communities were similar across the population and were strongly organized into co-abundance networks. Smoking associated with diversity loss, negative effects on abundant taxa, profound alterations to network structure and expansion of Streptococcus spp. By contrast, the asthmatic microbiota were selectively affected by an increase in Neisseria spp. and by reduced numbers of low abundance but prevalent organisms. InterpretationOur study shows healthy airway microbiota are contained within a highly structured ecosystem, indicating balanced relationships between the microbiome and human host factors. The marked abnormalities in smokers may be pathogenic for chronic obstructive pulmonary disease (COPD) and lung cancer. The narrow spectrum of abnormalities in asthmatics encourages investigation of damaging and protective effects of specific bacteria. FundingThe study was funded by the Asmarley Trust and a Wellcome Senior Investigator Award to WOCC and MFM (P46009). The Busselton Healthy Ageing Study is supported by the Government of Western Australia (Office of Science, Department of Health) the City of Busselton, and private donations.