Abstract:
The human respiratory tract is inhabited by a community of microorganisms termed the respiratory or airway microbiota. These microbes can significantly impact human respiratory health and may play a role in the development of various lung diseases. One such disease is non-cystic fibrosis bronchiectasis, a chronic condition in which patients undergo progressive lung damage experiencing recurrent exacerbations typically consisting of chronic cough and recurrent bacterial infection. Up to now, data about the microbiota of bronchiectasis are scarce. The disease has a high incidence among New Zealand children, particularly in Māori and Pacific Island communities. Unlike in adults, there is some suggestion that the lung damage seen in bronchiectasis may be reversible in children. The intent of this research is to better understand the role of the airway microbiota in paediatric bronchiectasis in New Zealand children. Specifically, this research aims to: (1) describe the airway microbiota during exacerbations and assess its response to treatment; (2) compare the microbiota among different clinical states and healthy children; (3) assess differences between the paediatric and adult microbiota. Nasal swabs and sputum samples were used to sample the upper and lower airway, respectively. Using 16S rRNA gene amplicon sequencing we determined bacterial community composition in the airways of children with non-cystic fibrosis bronchiectasis both before and after exacerbations, as well as in the upper airways of newly diagnosed and healthy control children. Droplet-digital PCR was used to estimate total bacterial load in nasal swabs for different clinical states. To assess how the microbiota differs between children and adults, data from our lab was compared to publicly available data from three other studies. Although substantial variability between samples was observed, the most abundant phyla in airways were Proteobacteria, Firmicutes and Bacteroidetes. Sample sites differed in composition and diversity. Some shifts in relative abundance of certain taxa and bacterial load were observed between clinical states, however diversity remained largely consistent. Composition and diversity exhibited some changes between adults and children, however this differed by study, likely due to methodological differences. This thesis provides insight into the role of the microbiota in bronchiectasis, potentially guiding future research.