Review articleIntegrating the microbiota of the respiratory tract with the unified airway model

- Overview of collection and sequencing methods specific to respiratory microbiota.
- Bacterial communities are highly similar in the lungs and upper respiratory tract.
- Prevotella, Streptococcus, and Veillonella are reliably present in the unifed airway.
- Bacterial shifts in one location of the airway may be related with changes in others.

The unified airway model has developed from indications that the upper and lower respiratory tracts share key elements of pathogenesis. These shared traits likely extend to similar niche characteristics that support bacterial communities, and as such, we suspect that similar microbes exist on upper and lower respiratory tract epithelium. Over the past decade and a half there have been significant improvements in microbiological identification and analysis due to the development of new molecular technologies, including next-generation sequencing. In this review, we provide an overview of the modern collection and sequencing methods involved in respiratory microbiota research, and outline the specific microbial communities that have been found to be associated with the healthy and diseased human respiratory tract. Demonstration of a remarkable similarity between the upper and lower respiratory tract in terms of microbiological presence adds further corroboration to the existence of a unified airway.