Background
Normal 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
incompletely defined.
Methods
We investigated airway bacterial communities in a general population sample of 529
Australian adults. Posterior oropharyngeal swabs were analyzed by sequencing of the
16S rRNA gene. The microbiota were characterized according to their prevalence,
abundance and network memberships.
Findings
The microbiota were similar across the general 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.
Interpretation
Our study shows that the healthy airway microbiota in this population were contained
within a highly structured ecosystem, suggesting balanced relationships between the
microbiome and human host factors. The marked abnormalities in smokers may
contribute to 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.