Abstract
Objective: Pathogenic airway bacteria colonizing the neonatal airway increase the risk of childhood asthma, but little is known about the determinants of the establishment and dynamics of the airway microbiota in early life. We studied associations between perinatal risk factors and bacterial richness of the commensal milieu in the neonatal respiratory tract. Methods: Three hundred and twenty-eight children from the Copenhagen Prospective Studies on Asthma in the Childhood2000 (COPSAC2000) at-risk birth cohort were included in this study. The bacterial richness in each of the nasopharynxes of the 1-month old, asymptomatic neonates was analyzed by use of a culture-independent technique (T-RFLP). Information on perinatal risk factors included predisposition to asthma, allergy and eczema; social status of family; maternal exposures during pregnancy; mode of delivery; and postnatal exposures. The risk factor analysis was done by conventional statistics and partial least square discriminant analysis (PLSDA). Results: The nasopharyngeal bacterial community at 1-month displayed an average of 35 (IQR: 14–55, range 1–161) phylogenetically different bacteria groups. Season of birth was associated with nasopharyngeal bacterial richness at 1-month of age with a higher bacterial richness (p = 0.003) and more abundant specific bacterial profiles representing Gram-negative alpha-proteobacteria and Gram-positive Bacilli in the nasopharynx of summer-born children. Conclusion: Early postnatal bacterial colonization of the upper airways is significantly affected by birth season, emphasizing a future focus on the seasonality aspect in modelling the impact of early dynamic changes in airway bacterial communities in relation to later disease development.
Highlights
Asymptomatic colonization in neonates with the common respiratory tract pathogens Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae has been shown to confer a higher risk of subsequent lung diseases, including childhood asthma [1,2,3]
Complex bacterial communities, such as those within the respiratory tract, have been studied by a number of different methods, including cultivation, which may be selective for certain species, but more recently, profiling of airway bacterial communities by culture-independent DNA based methods such as terminal restriction fragment length polymorphism (T-RFLP) [7,8] has been applied
In this study we focused on factors that could potentially influence the richness of the nasopharyngeal microbiota during establishment in early life, including perinatal risk factors such as predisposition to asthma and allergies and environmental risk factors relevant for the establishment of a commensal milieu in the respiratory tract
Summary
Asymptomatic colonization in neonates with the common respiratory tract pathogens Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae has been shown to confer a higher risk of subsequent lung diseases, including childhood asthma [1,2,3]. Little is known about the establishment and dynamics of the commensal microbiota in the neonatal respiratory tract [6] and the influences of genetic and perinatal environmental factors Complex bacterial communities, such as those within the respiratory tract, have been studied by a number of different methods, including cultivation, which may be selective for certain species, but more recently, profiling of airway bacterial communities by culture-independent DNA based methods such as terminal restriction fragment length polymorphism (T-RFLP) [7,8] has been applied. In this study we focused on factors that could potentially influence the richness of the nasopharyngeal microbiota during establishment in early life, including perinatal risk factors such as predisposition to asthma and allergies and environmental risk factors relevant for the establishment of a commensal milieu in the respiratory tract. Associations have been observed for asthma, allergic sensitization [12] and food allergies in particular [13], with potential mediation through differences in commensal microbiota in the respiratory tract influencing the early immune system’s development [5]
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