title: Role of microbiome in the pathophysiology and disease course of asthma.
abstract: The emergence of next-generation 16S rRNA sequencing techniques has facilitated a more detailed study of the body's microbiota and led to renewed interest in the association between microbial exposure and asthma inception. In this review, we evaluate the evidence that the respiratory tract and intestinal microbiota contribute to asthma pathogenesis and progression.
  
  
  
  Human studies have revealed associations between the presence of potentially pathogenic bacteria in the respiratory tract in early life and subsequent risk of allergic sensitization and asthma. Similarly, alterations in the intestinal microbiota of neonates have also been shown to precede the development of asthma. Emerging evidence suggests that the lung microbiota is dysregulated in asthma with specific changes in bacterial diversity and community composition according to severity and phenotype. Studies using germ-free mice have been invaluable in moving our understanding from correlation to causation by demonstrating a mechanistic link between the neonatal microbiota and the development of allergic airway inflammation.
  
  
  
  An expanding body of literature supports the hypothesis that early life microbial exposures and bacterial communities within the lung and/or intestine play an important role in shaping early immunological development. Perturbations in the microbiota may promote immune defects associated with the development of asthma and allergic sensitization.
authors.affiliation: Airway Disease Infection Section, National Heart and Lung Institute, Imperial College, London, UK.
authors.forename: Aran
authors.initials: A
authors.lastname: Singanayagam
authors.forename: Andrew I
authors.initials: AI
authors.lastname: Ritchie
authors.forename: Sebastian L
authors.initials: SL
authors.lastname: Johnston
mesh_terms: D000818:Animals; D001249:Asthma / Q000276:immunology* / Q000382:microbiology / Q000503:physiopathology; D018450:Disease Progression; D006801:Humans; D008168:Lung / Q000382:microbiology; D064307:Microbiota