title: Household siblings and nasal and fecal microbiota in infants.
abstract: BACKGROUND
  Early-life exposure to older siblings is associated with a lower risk of asthma. To date, no study has addressed the impact of having siblings on both the airway and fecal microbiota during infancy. The aim of this study was therefore to profile the nasal airway and fecal microbiota in infants, and to examine the association between having siblings and microbiota profile.
  
  
  METHODS
  We conducted a cross-sectional study of 105 healthy infants (aged <1 year). Using 16S rRNA gene sequencing and an unbiased clustering approach to the nasal airway and fecal samples, we identified microbiota profiles and then determined the association between having siblings and microbiome profile.
  
  
  RESULTS
  Overall, the median age was 3.4 months (IQR, 2.0-4.7 months); 43% had siblings in the household. Unbiased clustering of nasal airway microbiota identified three profiles: Moraxella dominant (43%), Corynebacterium/Dolosigranulum dominant (36%), and mixed (21%). Infants with siblings were more likely to have a Moraxella-dominant profile than Corynebacterium/Dolosigranulum-dominant profile (76% vs 18%), while those without siblings had the opposite pattern (18% vs 50%; P < 0.001, multivariable-adjusted). Fecal microbiota consisted of three profiles: Bifidobacterium dominant (39%), Escherichia dominant (31%), and Enterobacter dominant (30%). Infants with siblings were more likely to have a Bifidobacterium-dominant profile than Escherichia-dominant profile (49% vs 24%) while those without siblings had the opposite pattern (32% vs 37%; P = 0.04, multivariable-adjusted).
  
  
  CONCLUSIONS
  In this cross-sectional study, infants with siblings were more likely to have a Moraxella-dominant nasal microbiota profile and Bifidobacterium-dominant fecal microbiota profile. These findings should facilitate further investigation of the interplay between early-life environmental exposure, the microbiome, and childhood asthma.
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Kohei
authors.identifier: http://orcid.org/0000-0002-5739-7999
authors.initials: K
authors.lastname: Hasegawa
authors.affiliation: Department of Medicine, Boston Children's Hospital, Boston, Massachusetts, USA.
authors.forename: Rachel W
authors.initials: RW
authors.lastname: Linnemann
authors.affiliation: Division of Gastroenterology and Nutrition and General Academic Pediatrics, MassGeneral Hospital for Children, Boston, Massachusetts, USA.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Mansbach
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Nadim J
authors.initials: NJ
authors.lastname: Ajami
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Janice A
authors.initials: JA
authors.lastname: Espinola
authors.affiliation: Alkek Center for Metagenomics and Microbiome Research, Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Lauren G
authors.initials: LG
authors.lastname: Fiechtner
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Petrosino
authors.affiliation: Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Camargo
mesh_terms: D003430:Cross-Sectional Studies; D005243:Feces / Q000382:microbiology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D064307:Microbiota; D009297:Nasal Mucosa / Q000382:microbiology*; D035781:Siblings
keywords: airway microbiota; asthma; fecal microbiota; infant; sibling