title: Infant gut microbiota and the hygiene hypothesis of allergic disease: impact of household pets and siblings on microbiota composition and diversity.
abstract: BACKGROUND
  Multiple studies have demonstrated that early-life exposure to pets or siblings affords protection against allergic disease; these associations are commonly attributed to the "hygiene hypothesis". Recently, low diversity of the infant gut microbiota has also been linked to allergic disease. In this study, we characterize the infant gut microbiota in relation to pets and siblings.
  
  
  METHODS
  The study population comprised a small sub-sample of 24 healthy, full term infants from the Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort. Mothers reported on household pets and siblings. Fecal samples were collected at 4 months of age, and microbiota composition was characterized by high-throughput signature gene sequencing.
  
  
  RESULTS
  Microbiota richness and diversity tended to be increased in infants living with pets, whereas these measures were decreased in infants with older siblings. Infants living with pets exhibited under-representation of Bifidobacteriaceae and over-representation of Peptostreptococcaceae; infants with older siblings exhibited under-representation of Peptostreptococcaceae.
  
  
  CONCLUSIONS
  This study provides new evidence that exposure to pets and siblings may influence the early development of the gut microbiota, with potential implications for allergic disease. These two traditionally protective "hygiene hypothesis" factors appear to differentially impact gut microbiota composition and diversity, calling into question the clinical significance of these measures. Further research is required to confirm and expand these findings.
authors.affiliation: Department of Pediatrics, University of Alberta, 3-527 Edmonton Clinic Health Academy 11405 - 87th Avenue, Edmonton, AB, T6G IC9, Canada.
authors.forename: Meghan B
authors.initials: MB
authors.lastname: Azad
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
authors.forename: Theodore
authors.initials: T
authors.lastname: Konya
authors.affiliation: Cell & Systems Biology, University of Toronto, Toronto, ON, Canada.
authors.forename: Heather
authors.initials: H
authors.lastname: Maughan
authors.affiliation: Cell & Systems Biology, University of Toronto, Toronto, ON, Canada.
authors.forename: David S
authors.initials: DS
authors.lastname: Guttman
authors.affiliation: Agriculture, Food & Nutritional Sciences, University of Alberta, Edmonton, AB, Canada.
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Field
authors.affiliation: Department of Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Malcolm R
authors.initials: MR
authors.lastname: Sears
authors.affiliation: Pediatrics & Child Health, University of Manitoba, Winnipeg, MB, Canada ; Manitoba Institute of Child Health, Winnipeg, Canada.
authors.forename: Allan B
authors.initials: AB
authors.lastname: Becker
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
authors.forename: James A
authors.initials: JA
authors.lastname: Scott
authors.affiliation: Department of Pediatrics, University of Alberta, 3-527 Edmonton Clinic Health Academy 11405 - 87th Avenue, Edmonton, AB, T6G IC9, Canada ; Manitoba Institute of Child Health, Winnipeg, Canada.
authors.forename: Anita L
authors.initials: AL
authors.lastname: Kozyrskyj
keywords: Allergic disease; Atopy; Environmental exposures; Gut microbiome; Gut microbiota; Hygiene hypothesis; Infants; Microflora hypothesis; Pets; Siblings