A study to define microbiome subtypes in the adult asthmatic airway

Background: Molecular methods have shown that the airways harbour a distinct microbiome. Respiratory research is beginning to investigate the role of the host-microorganism interaction in both healthy and diseased lungs. Our aim was to characterise the lower airway microbiota in a cohort of well-defined adult asthmatics. Methods: 87 patients, clinically stratified by asthma severity (GINA) and level of control (ACQ-7) underwent bronchoscopy with BAL and endobronchial biopsies. Cell differentials, microscopy, DNA extraction and qPCR were performed to determine the presence and identity of microbes. Results: Microscopic evaluation demonstrated the presence of microbes in BAL, adherent to the epithelium of biopsies and demonstrated numerous intracellular microbial species within BAL macrophages. Overall qPCR revealed the presence of bacteria such as Firmicutes (69%), Proteobacteria (Pseudomonas (30%), Escherichia (35%), Bordetella (47%)), Prevotella (72%), Veillonella (85%), and the atypicals M. pneumoniae (54%) and C. pneumoniae (63%) in the BAL. Patients with severe asthma had higher levels of S. aureus (P Conclusions: The presence of distinct microbial species within the airway is associated with increased neutrophils, eosinophils and asthma severity. These findings suggest a complex interplay between microbial communities present in asthma and disease phenotype.