title: Bacterial Exposures and Associations with Atopy and Asthma in Children.
abstract: BACKGROUND
  The increase in prevalence of asthma and atopic diseases in Western countries has been linked to aspects of microbial exposure patterns of people. It remains unclear which microbial aspects contribute to the protective farm effect.
  
  
  OBJECTIVE
  The objective of this study was to identify bacterial groups associated with prevalence of asthma and atopy, and to quantify indoor exposure to some of these bacterial groups.
  
  
  METHODS
  A DNA fingerprinting technique, denaturing gradient gel electrophoresis (DGGE), was applied to mattress dust samples of farm children and control children in the context of the GABRIEL Advanced study. Associations between signals in DGGE and atopy, asthma and other allergic health outcomes were analyzed. Quantitative DNA based assays (qPCR) for four bacterial groups were applied on the dust samples to seek quantitative confirmation of associations indicated in DNA fingerprinting.
  
  
  RESULTS
  Several statistically significant associations between individual bacterial signals and also bacterial diversity in DGGE and health outcomes in children were observed. The majority of these associations showed inverse relationships with atopy, less so with asthma. Also, in a subsequent confirmation study using a quantitative method (qPCR), higher mattress levels of specifically targeted bacterial groups - Mycobacterium spp., Bifidobacteriaceae spp. and two different clusters of Clostridium spp. - were associated with a lower prevalence of atopy.
  
  
  CONCLUSIONS
  DNA fingerprinting proved useful in identifying bacterial signals that were associated with atopy in particular. These findings were quantitatively confirmed for selected bacterial groups with a second method. High correlations between the different bacterial exposures impede a clear attribution of protective effects to one specific bacterial group. More diverse bacterial flora in mattress dust may link to microbial exposure patterns that protect against development of atopic diseases.
authors.affiliation: Department of Health Protection, National Institute for Health and Welfare, Kuopio, Finland; Department of Environmental Science, University of Eastern Finland, Department of Environmental Science, Kuopio, Finland.
authors.forename: Maria
authors.initials: M
authors.lastname: Valkonen
authors.affiliation: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Inge M
authors.initials: IM
authors.lastname: Wouters
authors.affiliation: Department of Health Protection, National Institute for Health and Welfare, Kuopio, Finland.
authors.forename: Martin
authors.initials: M
authors.lastname: Täubel
authors.affiliation: Department of Health Protection, National Institute for Health and Welfare, Kuopio, Finland.
authors.forename: Helena
authors.initials: H
authors.lastname: Rintala
authors.affiliation: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Virissa
authors.initials: V
authors.lastname: Lenters
authors.affiliation: Department of Health Protection, National Institute for Health and Welfare, Kuopio, Finland.
authors.forename: Ritva
authors.initials: R
authors.lastname: Vasara
authors.affiliation: Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany.
authors.forename: Jon
authors.initials: J
authors.lastname: Genuneit
authors.affiliation: University of Basel, Basel, Switzerland.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Braun-Fahrländer
authors.affiliation: UMR MD3 Aix-Marseille University, Marseilles, France.
authors.forename: Renaud
authors.initials: R
authors.lastname: Piarroux
authors.affiliation: Ludwig Maximilians University, Munich, Germany.
authors.forename: Erika
authors.initials: E
authors.lastname: von Mutius
authors.affiliation: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Dick
authors.initials: D
authors.lastname: Heederik
authors.affiliation: Department of Health Protection, National Institute for Health and Welfare, Kuopio, Finland.
authors.forename: Anne
authors.initials: A
authors.lastname: Hyvärinen
mesh_terms: D000367:Age Factors; D016902:Air Pollution, Indoor / Q000009:adverse effects; D001249:Asthma / Q000453:epidemiology / Q000276:immunology* / Q000382:microbiology; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000276:immunology*; D044822:Biodiversity; D002648:Child; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology / Q000276:immunology* / Q000382:microbiology; D008297:Male; D058889:Molecular Typing; D036301:Qualitative Research; D012307:Risk Factors