Introduction
This analysis describes pathogens identified at stable state and exacerbation in patients in the EMBARC bronchiectasis registry.
Methods
We analysed a large cohort of patients from the European Bronchiectasis registry EMBARC (enrolled 2015-2022) with sputum samples sent at stable state and exacerbation.
Results
18843 patients were included in the study.  28272 sputum samples were sent during the study period, 17237 (61%) at stable state and 11035 (39%) at exacerbation.  The most common pathogens identified across all patients were Pseudomonas aeruginosa (3175, 16.8%) Haemophilus Influenzae (2775, 14.7%), Staphylococcus aureus (1024, 5.4%) and Streptococcus pneumoniae (799, 4.2%). The most common pathogens identified at stable state and exacerbation were similar: P. aeruginosa (stable, 2032, 10.8% vs exacerbations, 1602, 8.5%), H. Influenzae (stable, 1675, 8.9% vs exacerbations, 1332, 7.1%), Enterobacteriaceae (stable, 765, 4.0% vs exacerbation, 614, 3.2%) S. aureus (stable, 661, 3.5% vs exacerbation 414, 2.2%) and S. pneumoniae (stable, 517, 2.7% vs exacerbation 514, 2.7%).  There was no clear difference in pathogen distribution by aetiology, except for a higher rate of most pathogens in patients with Primary Ciliary Dyskinesia (PCD).  880 (4.7%) of patients had at least one sample growing multiple organisms.  In total 1181 (4.2%) of samples grew multiple organisms.
Discussion
There is no clear difference between microbiology at stable state and exacerbation and no clear variation by aetiology, except in the case of PCD which has a higher rate of most pathogens.  Samples growing multiple organisms are common.