The healthy lung has previously been considered to be a sterile organ because standard microbiological culture techniques consistently yield negative results. However, culture-independent techniques report that large numbers of microorganisms coexist in the lung. There are many unknown aspects in the field, but available reports show that the lower respiratory tract microbiota: 1) is similar in healthy subjects to the oropharyngeal microbiota and dominated by members of the Firmicutes, Bacteroidetes and Proteobacteria phyla; 2) shows changes in smokers and well-defined differences in chronic respiratory diseases, although the temporal and spatial kinetics of these changes are only partially known; and 3) shows relatively abundant non-cultivable bacteria in chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, cystic fibrosis and bronchiectasis, with specific patterns for each disease. In all of these diseases, a loss of diversity, paralleled by an over-representation of Proteobacteria (dysbiosis), has been related to disease severity and exacerbations. However, it is unknown whether dysbiosis is a cause or a consequence of the damage to bronchoalveolar surfaces.
Finally, little is known about bacterial functionality and the interactions between viruses, fungi and bacteria. It is expected that future research in bacterial gene expressions, metagenomics longitudinal analysis and host–microbiome animal models will help to move towards targeted microbiome interventions in respiratory diseases.
The respiratory system bacterial community is dominated by specific phyla that change in chronic respiratory diseases http://ow.ly/j68Z30967DB
Conflict of interest: Disclosures can be found alongside this article at erj.ersjournals.com
This article is a summary of a Barcelona Respiratory Network workshop held in Barcelona on June 3rd, 2016. The symposium was supported by unrestricted grants from Menarini, AstraZeneca, Chiesi, GSK and Novartis and partially funded by Fundació Ramón Pla Armengol, Fondo de Investigación Sanitaria 15/00167 and PI15/02042.
- Received October 25, 2016.
- Accepted February 8, 2017.
- Copyright ©ERS 2017