Loss of Microbial Topography between Oral and Nasopharyngeal Microbiota and Development of Respiratory Infections Early in Life.

The respiratory microbiota is increasingly being appreciated as an important mediator in the susceptibility to childhood respiratory tract infections (RTIs). Pathogens are presumed to originate from the nasopharyngeal ecosystem. To investigate the association between early life respiratory microbiota and development of childhood RTIs. In a prospective birth cohort (Microbiome Utrecht Infant Study: MUIS), we characterized the oral microbiota longitudinally from birth until 6 months of age of 112 infants (nine regular samples/subject) and compared them with nasopharyngeal microbiota using 16S-rRNA-based sequencing. We also characterized oral and nasopharynx samples during RTI episodes in the first half year of life. Oral microbiota were driven mostly by feeding type, followed by age, mode of delivery, and season of sampling. In contrast to our previously published associations between nasopharyngeal microbiota development and susceptibility to RTIs, oral microbiota development was not directly associated with susceptibility to RTI development. However, we did observe an influx of oral taxa, such as , , , , and , in the nasopharyngeal microbiota before and during RTIs, which was accompanied by reduced presence and abundance of , , and spp. Moreover, this phenomenon was accompanied by reduced niche differentiation indicating loss of ecological topography preceding confirmed RTIs. This loss of ecological topography was further augmented by start of daycare, and linked to consecutive development of symptomatic infections. Together, our results link the loss of topography to subsequent development of RTI episodes. This may lead to new insights for prevention of RTIs and antibiotic use in childhood.