Lung and gut microbiota markers in children aged 1 to 3 years help distinguish asthma severity (DREAM). DREAM

sthma is the most common chronic disease in children, with limited therapeutic resources for those aged 1-3. Identifying biomarkers in the lung and gut microbiota could help predict corticosteroid resistance.A prospective, exploratory, case-control study was conducted at Brest and Nantes University hospitals from January to May 2022. Twenty-five patients aged 1-3 years were included: 15 with severe asthma and 10 with mild to moderate asthma. Lung microbiota was analyzed using induced sputum, and gut microbiota was assessed using high-throughput 16S rDNA sequencing followed by bioinformatics analysis. The two patient groups had no significant differences in microbiota richness and diversity. However, supervised beta-diversity analysis revealed that severe asthma patients had more similar lung and gut microbiota than non-severe patients. Specifically, the lung microbiota showed a significantly higher relative abundance of Prevotella nanceiensis in severe patients (p=0.04). In the gut microbiota, a decreased abundance of the Lachnospiraceae NK4A136 group was associated with more severe asthma. Severe asthma, including corticosteroid-resistant cases, is linked to a more uniform lung and gut microbiota profile. Potential biomarkers of severe asthma include increased P. nanceiensis in the lung microbiota and decreased Lachnospiraceae NK4A136 in the gut microbiota. These findings may improve the characterization and management of severe asthma in children under 3 years old.