, a potential predictive biomarker of pulmonary infection in cystic fibrosis.

Introduction: pulmonary infections are the primary cause of morbi-mortality in patients with cystic fibrosis (CF). In this cohort study, the objective was to identify candidate biomarkers of infection within the airway microbiota.

Methods: A 3-year prospective multicentre study (PYOMUCO study) was conducted in Western France and included patients initially free for at least 1 year. A 16S-targeted metagenomics approach was applied on iterative sputum samples of a first set of patients (n=33). The composition of airway microbiota was compared according to their status at the end of the follow-up (colonised vs non-colonised), and biomarkers associated with were screened. In a second step, the distribution of a candidate biomarker according to the two groups of patients was verified by qPCR on a second set of patients (n=52) coming from the same cohort and its load quantified throughout the follow-up.

Results: (mainly ) was found to be an enriched phylotype in patients uninfected by (p<0.001). This result was confirmed by quantitative PCR. Conversely, in patients who became positive, significantly decreased before acquisition (p=0.014).

Discussion: Further studies on replication cohorts are needed to validate this potential predictive biomarker, which may be relevant for the follow-up in the early years of patients with CF. The identification of infection candidate biomarkers may offer new strategies for CF precision medicine.