Title: Bacterial profile by age in paediatric Non-CF Bronchiectasis (NCFB)

<b>Background:</b> Understanding the bacterial profile over time in childhood may help early identification of children progressing from pre-bronchiectasis to high resolution computerised tomographic (HCRT) confirmed bronchiectasis on the chronic suppurative lung disease (CSLD) spectrum. A microbiological profile by age has been well described in Cystic Fibrosis. <b>Aim:</b> To describe the bacterial infection profile of children with NCFB. <b>Objectives:</b> Identify age of first documented isolate of each pathogen. <b>Methods:</b> Retrospective study of respiratory bacterial sample results between 01/2011 – 08/2021 of 32 children with NCFB defined by HRCT presenting to a tertiary paediatric respiratory centre since 2012 recording type of pathogens seen and age of first isolate. <b>Results:</b> 32 children (15 females) were identified for inclusion. 353 sample collection dates were identified from age 7 months - 16 years (y), including bronchoealveolar lavage, sputum or cough swabs specimens. The most common pathogens seen were H. Influenza (22), S. Aureus (12), Moraxella Catarrhalis (10), Strep Pneumonia (7), and yeast&amp;mould (6). Mean age of first isolate was 6.5y (range &lt;1-14y, median 5y). No distinctive pattern of first bacterial pathogen or progression with age was observed. Three groups of children were however identified: those with first infection &lt;6 years, those around 11-14 years, and those with no culture of bacterial pathogen over the study time period. <b>Conclusion:</b> The pattern of bacterial infections with age seen in cystic fibrosis was not replicated. The 3 groups warrant further exploration, the largest group with first isolates &lt;5y supports the model of a CSLD spectrum starting with protracted bacterial bronchitis in under 5s.