title: Environmental and mucosal microbiota and their role in childhood asthma.
abstract: BACKGROUND
  High microbial diversity in the environment has been associated with lower asthma risk, particularly in children exposed to farming. It remains unclear whether this effect operates through an altered microbiome of the mucosal surfaces of the airways.
  
  
  METHODS
  DNA from mattress dust and nasal samples of 86 school age children was analyzed by 454 pyrosequencing of the 16S rRNA gene fragments. Based on operational taxonomic units (OTUs), bacterial diversity and composition were related to farm exposure and asthma status.
  
  
  RESULTS
  Farm exposure was positively associated with bacterial diversity in mattress dust samples as determined by richness (P = 8.1 × 10-6) and Shannon index (P = 1.3 × 10-5). Despite considerable agreement of richness between mattress and nasal samples, the association of richness with farming in nasal samples was restricted to a high gradient of farm exposure, that is, exposure to cows and straw vs no exposure at all. In mattress dust, the genera Clostridium, Facklamia, an unclassified genus within the family of Ruminococcaceae, and six OTUs were positively associated with farming. Asthma was inversely associated with richness [aOR = 0.48 (0.22-1.02)] and Shannon index [aOR = 0.41 (0.21-0.83)] in mattress dust and to a lower extent in nasal samples [richness aOR 0.63 = (0.38-1.06), Shannon index aOR = 0.66 (0.39-1.12)].
  
  
  CONCLUSIONS
  The stronger inverse association of asthma with bacterial diversity in mattress dust as compared to nasal samples suggests microbial involvement beyond mere colonization of the upper airways. Whether inhalation of metabolites of environmental bacteria contributes to this phenomenon should be the focus of future research.
authors: Dr. von Hauner Children's Hospital, LMU Munich, Munich, Germany.
authors: L T
authors: LT
authors: Birzele
authors: Dr. von Hauner Children's Hospital, LMU Munich, Munich, Germany.
authors: M
authors: M
authors: Depner
authors: Dr. von Hauner Children's Hospital, LMU Munich, Munich, Germany.|Member of the German Center for Lung Research (DZL), Munich, Germany.
authors: M J
authors: MJ
authors: Ege
authors: Research Unit Scientific Computing, Helmholtz Center Munich, Neuherberg, Germany.|Research Unit for Environmental Genomics, Helmholtz Center Munich, Neuherberg, Germany.
authors: M
authors: M
authors: Engel
authors: Research Unit for Environmental Genomics, Helmholtz Center Munich, Neuherberg, Germany.
authors: S
authors: S
authors: Kublik
authors: Leibniz Supercomputing Center of the Bavarian Academy of Sciences and Humanities, Garching, Germany.
authors: C
authors: C
authors: Bernau
authors: Dr. von Hauner Children's Hospital, LMU Munich, Munich, Germany.|Department of Pediatrics, School of Medicine, University of California, San Diego, CA, USA.
authors: G J
authors: GJ
authors: Loss
authors: Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany.
authors: J
authors: http://orcid.org/0000-0001-5764-1528
authors: J
authors: Genuneit
authors: Division of Cardiology and Pulmonology, Department of Pediatrics and Adolescents, Innsbruck Medical University, Innsbruck, Austria.
authors: E
authors: E
authors: Horak
authors: Research Unit for Environmental Genomics, Helmholtz Center Munich, Neuherberg, Germany.
authors: M
authors: M
authors: Schloter
authors: Swiss Tropical and Public Health Institute, Basel, Switzerland.|Department of Epidemiology and Public Health, University of Basel, Basel, Switzerland.
authors: C
authors: C
authors: Braun-Fahrländer
authors: Department of Pediatrics, Allergology and Cardiology, Wroclaw Medical University, Wroclaw, Poland.
authors: H
authors: H
authors: Danielewicz
authors: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, University of Utrecht, Utrecht, The Netherlands.
authors: D
authors: D
authors: Heederik
authors: Dr. von Hauner Children's Hospital, LMU Munich, Munich, Germany.|Member of the German Center for Lung Research (DZL), Munich, Germany.
authors: E
authors: E
authors: von Mutius
authors: Dr. von Hauner Children's Hospital, LMU Munich, Munich, Germany.
authors: A
authors: A
authors: Legatzki
mesh_terms: D001249:Asthma / Q000453:epidemiology* / Q000209:etiology*; D001419:Bacteria / Q000145:classification / Q000235:genetics; D044822:Biodiversity; D002648:Child; D003430:Cross-Sectional Studies; D004781:Environmental Exposure / Q000009:adverse effects*; D004783:Environmental Microbiology; D005260:Female; D006801:Humans; D008297:Male; D064307:Microbiota; D009092:Mucous Membrane / Q000382:microbiology*
keywords: asthma; epidemiology; microbiome; pediatrics