Nasal microbiota and symptom persistence in acute respiratory tract infections in infants

Neumann, Roland P.; Hilty, Markus; Xu, Binbin; Usemann, Jakob; Korten, Insa; Mika, Moana; Müller, Loretta; Latzin, Philipp; Frey, Urs

Composition of the airway microbiota is highly dynamic and various environmental factors have been shown to influence colonisation patterns. Antimicrobial exposure and vaccinations, as well as tobacco smoke exposure, can lead to changes in the airway microbiota [15, 16] . In a prospective cohort study, we investigated the nasal microbiota in infants longitudinally during the first year of life [17] , in the absence of acute respiratory tract infections (ARI). We showed that the composition of nasal microbiota in infants is highly dynamic and seems to be predominantly influenced by age and season. However, little is known about how and to what degree ARIs, which are often caused by viruses, influence the dynamically changing microbiota. Interactions between viruses and bacteria are well known [18] , but their relationship to respiratory symptoms is not completely understood. Recently, KORTEN et al. [7] demonstrated for human rhinovirus (HRV) that the microbiota primarily changes in cases of symptomatic ARI, but not in cases of asymptomatic HRV colonisation. In the study by KORTEN et al. [7] , nasal swabs were taken biweekly throughout the first year of life irrespective of presence or absence of symptoms and not necessarily at the onset of the very first ARI. BOSCH et al. [19] observed an advanced "microbiota age" in infants with more frequent ARIs in the first year of life. Thus, we hypothesise that the first symptomatic viral infection in infection-naïve infants may induce distinct changes in microbiota following commonly observed respiratory viruses. We also hypothesise that distinct clusters of infants with specific microbial response patterns can be identified, which could be associated with severity of clinical symptom response and host risk factors, such as risk for atopy, as suggested by TEO et al. [5] .