Characteristics of the bacterial microbiota in the upper respiratory tract of children

Purpose The respiratory tract microbiota are deemed as the gatekeeper to health. Consequently, microbiota dysbiosis can lead to the development of diseases. To identify the exact origins of the localized pathogenic bacteria, we investigated bacterial composition in the upper airway tract. Methods Separate mucosal swabs were collected from nostril or oropharynx of each participant. Meanwhile, the lymphoid tissues including adenoids and tonsils were collected during operation. DNAs were exacted from all the samples for the following 16S rRNA analysis. Results At the phylum level, the basic bacterial structures in the adenoids, tonsils, oropharynx, and nostrils were generally similar: five main phyla Firmicutes , Proteobacteria , Bacteroidetes , Actinobacteria , and Fusobacteria form the majority of the microbiota. However, across these four sites, the microbiota composition differed. More specifically, the bacterial composition in the nostrils was unique. There, Firmicutes and Actinobacteria were the most abundant phyla, while Bacteroides and Fusobacteria were the least abundant. At the genus level, Staphylococcus , Dolosigranulum , Corynebacterium , and Moraxella were the most plentiful, while Fusobacteria was the least ample. Across all sites, Streptococcus displayed similar abundances. Fusobacteria exhibited higher abundances in the lymphoid tissues and oropharynx. Haemophilus and Neisseria were more plentiful in the tonsils and oropharynx. Notably, Klebsiella , which is normally localized to the gut, was abundant in the adenoids and tonsils. Conclusion Our data indicate that promising pathogenic bacteria originate from all sites in the upper airway. The upper tract lymphoid tissues, normally considered as immune organs, may also serve as reservoirs for pathogenic bacteria.