Gut microbiota in adults with cystic fibrosis: Implications for the severity of the CFTR gene mutation and nutritional status

•The composition of gut microbiota was evaluated in adults with and without CF.•Gut microbiota samples were analyzed using full-length 16S rRNA gene sequencing.•CF is associated with alterations of gut microbiota in adult CF patients.•Body Mass Index is related to gut microbiota dysbiosis in adults with CF. Microbial dysbiosis has been linked to cystic fibrosis (CF); however, the composition of gut microbiota in adult CF patients in relation to severity of CF transmembrane conductance regulator (CFTR) gene mutation and nutritional status have not yet been explored. Study aimed to assess the gut microbiota composition in adults with CF, and its relationship with the severity of CFTR mutations, and BMI. Gut microbiota of 41 adults with CF, and 26 non-CF controls were compared using whole 16S rRNA gene sequencing. Differences in the microbial community between groups of patients classified according to the severity of CFTR mutations, and BMI were assessed. The alpha diversity, beta diversity, and taxa abundance were identified to reflect gut microbiota composition. Results showed a significant decrease in alpha diversity of bacterial communities in CF compared to non-CF group, but no significant difference between the CF groups distinguished by the severity of CFTR mutations. However, more severe mutations were associated with the higher relative abundance of Bacteroides and Streptococcus and the lower relative abundance of Faecalibacterium and Blautia. Undernourished CF patients showed significantly lower alpha diversity compared to non-CF group and CF patients with BMI within the norm. Significant differences in the structure of the gut microbiota between CF and non-CF groups, as well as between BMI groups were also found. Our research indicates that CF is associated with alterations in gut microbiota in adults. Additionally, in adult CF patients, the composition of the gut microbiota is also related to BMI.