title: Dynamics of the nasal microbiota in infancy: a prospective cohort study.
abstract: BACKGROUND
  Understanding the composition and dynamics of the upper respiratory tract microbiota in healthy infants is a prerequisite to investigate the role of the microbiota in patients with respiratory diseases. This is especially true in early life, when the immune system is in development.
  
  
  OBJECTIVE
  We sought to describe the dynamics of the upper respiratory tract microbiota in healthy infants within the first year of life.
  
  
  METHODS
  After exclusion of low-quality samples, microbiota characterization was performed by using 16S rDNA pyrosequencing of 872 nasal swabs collected biweekly from 47 unselected infants.
  
  
  RESULTS
  Bacterial density increased and diversity decreased within the first year of life (R(2) = 0.95 and 0.73, respectively). A distinct profile for the first 3 months of life was found with increased relative abundances of Staphlyococcaceae and Corynebacteriaceae (exponential decay: R(2) = 0.94 and 0.96, respectively). In addition, relative bacterial abundance and composition differed significantly from summer to winter months. The individual composition of the microbiota changed with increasing time intervals between samples and was best modeled by an exponential function (R(2) = 0.97). Within-subject dissimilarity in a 2-week time interval was consistently lower than that between subjects, indicating a personalized microbiota.
  
  
  CONCLUSIONS
  This study reveals age and seasonality as major factors driving the composition of the nasal microbiota within the first year of life. A subject's microbiota is personalized but dynamic throughout the first year. These data are indispensable to interpretation of cross-sectional studies and investigation of the role of the microbiota in both healthy subjects and patients with respiratory diseases. They might also serve as a baseline for future intervention studies.
authors: Institute for Infectious Diseases, University of Bern, Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.
authors: Moana
authors: M
authors: Mika
authors: Division of Respiratory Medicine, Department of Pediatrics, Inselspital and University of Bern, Bern, Switzerland; University Children's Hospital (UKBB), Basel, Switzerland.
authors: Ines
authors: I
authors: Mack
authors: Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland; Division of Respiratory Medicine, Department of Pediatrics, Inselspital and University of Bern, Bern, Switzerland.
authors: Insa
authors: I
authors: Korten
authors: Functional Genomics Center, Swiss Federal Institute of Technology Zurich/University of Zurich, Zurich, Switzerland.
authors: Weihong
authors: W
authors: Qi
authors: Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
authors: Suzanne
authors: S
authors: Aebi
authors: University Children's Hospital (UKBB), Basel, Switzerland.
authors: Urs
authors: U
authors: Frey
authors: Division of Respiratory Medicine, Department of Pediatrics, Inselspital and University of Bern, Bern, Switzerland; University Children's Hospital (UKBB), Basel, Switzerland.
authors: Philipp
authors: P
authors: Latzin
authors: Institute for Infectious Diseases, University of Bern, Bern, Switzerland; Department of Infectious Diseases, University Hospital, Bern, Switzerland. Electronic address: markus.hilty@ifik.unibe.ch.
authors: Markus
authors: M
authors: Hilty
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics; D058491:Bacterial Load; D044822:Biodiversity; D004269:DNA, Bacterial; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D054892:Metagenome; D064307:Microbiota; D009666:Nose / Q000382:microbiology*; D011446:Prospective Studies; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012621:Seasons
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S
keywords: Nasal microbiota; age; bacterial families; cohort study; season; toddlers