The pathogenicity of Achromobacter bacteria is not yet well established, but studies show a decline in respiratory function and an increase in mortality associated with chronic colonisation, making it possible to classify the Achromobacter genus as an emerging pathogen in cystic fibrosis. It is possible that certain species or clones are more virulent or resistant, requiring the adaptation of measures to prevent cross-transmission in the centres concerned.

However, until now, the identification of Achromobacter species has involved the use of molecular biology techniques that are not routinely applicable in diagnostic laboratories, limiting studies and the collection of epidemiological data. Recently, a database using MALDI-TOF mass spectrometry has been built for rapid and accurate species identification.

In view of the local epidemiology and the current lack of data, it would be necessary and interesting to use this tool to study a cohort of cystic fibrosis patients in Réunion island (North and South sites) to see whether one species has a greater clinical impact than another (pathogenicity), and/or is more responsible for chronic colonisation.

The research hypotheses are: What is the pathogenicity of Achromobacter species in cystic fibrosis patients? Is the pathogenicity of one species of the genus Achromobacter greater than that of other species in cystic fibrosis patients, depending on the colonization status of this bacterial species? Colonization with a species of the genus Achromobacter is associated with an increased frequency of pulmonary exacerbations in cystic fibrosis patients.

Investigator will therefore assess the frequency of pulmonary exacerbations as a function of the Achromobacter species colonizing/infecting cystic fibrosis patients.

As this is an exploratory study carried out mainly on bacterial strains from patients, it presents no risk to patients.

the results of the study will enable clinicians to improve their knowledge of the different species of bacteria in the Achromobacter genus, in terms of pathogenicity, ability to colonize the respiratory tract, resistance and virulence.

As far as patients are concerned, the knowledge gained from this study will help improve the overall management of their disease. It will also provide food for thought on the establishment of guidelines and recommendations for dealing with Achromobacter spp. colonization and therapeutic strategy.

Inclusion Criteria:

• Minor or major cystic fibrosis patients
• Patients with at least one sputum cytobacteriological test positive for Achromobacter spp. during the inclusion period.
• Patients living in La Réunion island.
• Patients for whom a non-opposition was obtained orally (if applicable from both one of the child's legal guardians and the child him/herself)

Exclusion Criteria:

• Patients without cystic fibrosis.
• Patients with cystic fibrosis but no Achromobacter-positive ECBC during the study inclusion period

Cohort of cystic fibrosis patients from Reunion island with Achromobacter spp colonisation