WS07.5 Gut microbiome in healthy children and children with cystic fibrosis during the first 18 months of life

Introduction: Progressive lung damage, associated with bacterial infection and neutrophil mediated inflammation, is the major cause of morbidity and death in CF. Ivacaftor improves lung function in CF patients with the G551D mutation and this may be associated with changes in airway bacterial community composition. Objectives: To determine the effect of ivacaftor on CF airway bacterial community composition and to examine the relationship with lung function and measures of systemic inflammation. Methods: Sputum and blood samples from CF patients (n = 20) were collected prior to and every three months (for 12 months) after initiation of ivacaftor therapy. Molecular based analysis (Illumina MiSeq) was used to define airway bacterial community composition. ELISA’s were used to quantify measures of systemic inflammation in blood (IL-8, IL-6 & CRP). Results: Mean relative abundance of Pseudomonas decreased after ivacaftor therapy whilst relative abundance of Streptococcus, Haemophilus, Rothia and Prevotella increased. There was no correlation between relative abundance of individual taxa and lung function. However, there was a significant inverse correlation between the relative abundance of both Streptococcus and Prevotella and IL-8 (p < 0.05). There was no association between relative abundance of individual taxa and IL-6 or CRP. Conclusion: Alterations in CF airway bacterial community composition post-ivacaftor therapy are associated with reduced levels of the potent neutrophil chemoattractant IL-8. This may result in decreased neutrophil influx into the airways and improve lung function by limiting neutrophil mediated inflammation. Acknowledgement: Funding: DEL NI Studentship & CFMATTERS (603038)