Respiratory Dysbiosis in Preschool Children with Asthma: Predictive of a Severe Form

The prevalence of asthma in preschool children is estimated to between 11 and 12%. Inhaled corticosteroid therapy is the main therapy used, however this treatment seems insufficiently effective in some children. Recent research in cystic fibrosis has made it possible to highlight pulmotypes corresponding to the different stages of pulmonary dysbiosis, and a predictive microbiological signature of an increased risk of early primocolonization to P. aeruginosa. These pulmotypes are the result of the so-called "enterotypeing" analysis, a biostatistical method that makes it possible to stratify individuals according to the analysis of the microbiota. In the light of these data, it seems interesting to transcribe the concept of using a biomarker of the microbiota in the monitoring of a chronic lung disease such as asthma. The hypothesis is that there is respiratory dysbiosis causing corticosteroid resistance to treatment in children under 3 years of age with severe asthma. The goal of this study is to research a difference between respiratory dysbiosis and severe asthma (i.e. resistant to doses of inhaled corticosteroids less than or equal to 200μg of fluticasone equivalent). DREAM is a exploratory multicentric prospective case-control study. The primary objective is to research a difference between respiratory dysbiosis and severe asthma (i.e. resistant to doses of inhaled corticosteroids less than or equal to 200μg of fluticasone equivalent) in children less than 36 months of age. The secondary objectives are : 1. To compare the bacterial pulmotypes of children under 36 months of age with severe asthma with children with mild or moderate asthma. 2. To look for microbial biomarkers associated with corticosteroid resistance 3. To assess the association between digestive dysbiosis and severe asthma (i.e. resistant to inhaled corticosteroid doses less than or equal to 200μg fluticasone equivalent) 4. To look for an association between digestive dysbiosis and respiratory dysbiosis 5. To constitute a biocollection (sputum, stool, blood) of children with asthma for future analysis 30 patients are expected to be included in two arms : 15 uncontrolled asthmatic patients at moderate doses of inhaled corticosteroids and 15 asthmatic patients controlled at mild to moderate doses of inhaled corticosteroids. Inclusion period : 12 months. Duration of patient's participation: 6 years Total study duration: 7 years