Increased Risk of Pneumonia and Bronchiolitis after Bacterial Colonization of the Airways as Neonates

Rationale: The frequency of pneumonia and bronchiolitis exhibits considerable variation in otherwise healthy children, and suspected risk factors explain only a minor proportion of the variation. We hypothesized that alterations in the airway microbiome in early life may be associated with susceptibility to pneumonia and bronchiolitis in young children. Objectives: To investigate the relation between neonatal airway colonization and pneumonia and bronchiolitis during the first three years of life. Methods: Participants comprised children of the COPSAC2000 cohort; a prospective birth cohort study of 411 children born to asthmatic mothers. Aspirates from the hypopharynx at age four weeks were cultured for S.pneumoniae, H.influenzae, M.catarrhalis, and S.aureus. Clinical information on pneumonia and bronchiolitis within the first three years of life was prospectively collected by the research physicians at the center. Analyses were adjusted for covariates associated pneumonia and bronchiolitisand bacterial airway colonization. Measurements and Main Results: Hypopharyngeal aspirates and full clinical follow-up until three years of age were available for 265 children. Of these, 56 (21%) neonates were colonized with S.pneumoniae, H.influenzae and/or M.catarrhalis at four weeks of age. Colonization with at least one of these microorganisms, (but not S.aureus), was significantly associated with increased incidence of pneumonia and bronchiolitis (adjusted Incidence Rate Ratio=1.79[1.29-2.48], p-value