ABSTRACT: A rich microbial environment in infancy protects
against asthma ,  and infections precipitate asthma
exacerbations . We compared the airway microbiota at three
levels in adult patients with asthma, the related condition of
COPD, and controls. We also studied bronchial lavage from
asthmatic children and controls. We identified 5,054 16S rRNA
bacterial sequences from 43 subjects, detecting >70% of species
present. The bronchial tree was not sterile, and contained a
mean of 2,000 bacterial genomes per cm(2) surface sampled.
Pathogenic Proteobacteria, particularly Haemophilus spp., were
much more frequent in bronchi of adult asthmatics or patients
with COPD than controls. We found similar highly significant
increases in Proteobacteria in asthmatic children. Conversely,
Bacteroidetes, particularly Prevotella spp., were more frequent
in controls than adult or child asthmatics or COPD patients. The
results show the bronchial tree to contain a characteristic
microbiota, and suggest that this microbiota is d