The Airway Microbiome and Childhood Asthma - What Is the Link?

In this paper we propose to describe the available evidence from the literature on upper airway microbiome and its association with paediatric asthma and allergy. Recent advances in sequencing the bacterial 16S ribosomal RNA (16S rRNA) gene have enabled research into the complex communities of bacteria, known as the microbiome, that exist outside and inside the human body. Although the upper airways have long been recognised to host a microbiome, the lower airways are now known to contain a rich and diverse microbiome. This review first describes the microbiome of the upper and lower airways and then explores associations between the microbiome in the airways and bowel and asthma in children. The characteristics of the microbiome differ between nose and mouth, and between the mouth and bronchus in terms of burden and diversity of bacteria and in the predominant phyla present. There is a small literature which suggests that there are differences in the airway microbiome in early life between children who later have asthma compared to those who do not develop asthma. CONCLUSION: At the time of writing it is not clear whether the microbiome may cause childhood asthma, whether the conditions in the asthmatic airway encourage a different microbiome or whether a third factor confounds the relationship between airway microbiome and childhood asthma.