Bronchial brushings from 40 participants in the Bronchoscopic Exploratory Research Study of Biomarkers in Corticosteroid-refractory Asthma (BOBCAT) study were evaluated by using 16S ribosomal RNA–based methods. In patients with severe asthma, bronchial bacterial composition was associated with several disease-related features, including body mass index, Asthma Control Questionnaire (ACQ) scores, sputum leukocyte values, and bronchial biopsy eosinophil values.
Bacterial communities associated with worsening ACQ scores and sputum leukocyte values (predominantly Proteobacteria) differed markedly from those associated with body mass index (Bacteroidetes/Firmicutes). Expression of TH17-related genes was associated with Proteobacteria.
In contrast, improving/stable ACQ scores and bronchial epithelial gene expression of FK506 binding protein (FKBP5), an indicator of steroid responsiveness, correlated with Actinobacteria.
Patients with severe asthma compared with healthy control subjects or patients with mild-to-moderate asthma were significantly enriched in Actinobacteria, although the largest differences observed involved a Klebsiella genus member (7.8-fold increase in patients with severe asthma).
Specific microbiota may modulate inflammatory processes in patients with severe asthma and related phenotypes. Airway dysbiosis in severe asthma differs from milder asthma.
The airway microbiome in patients with severe asthma: Associations with disease features and severity. Yvonne J. Huang et al. JACI, October 2015, Volume 136, Issue 4, Pages 874–884 (full text).
The World Allergy Organization (WAO) Small Airways Working Group publishes a monthly "What's New?" summary and I have served as its editor since 2011. The summary features the top 3 asthma/small airways articles each month. The article above is a part of the project. The archive is here: http://www.worldallergy.org/small_airways_group/reviews/archive.php