CFTR and cystic fibrosis: CFTR gene variants have been investigated as a possible influencer of gut microbiota in CF patients who are not on antibiotics: Escherichia coli and Eubacterium biforme species were found to be prevalent in patients with F508del mutations, especially in the homozygous state and in more severe CF patients, while beneficial species, such as Faecalibacterium prausnitzii, Bifidobacterium spp., and Eubacterium limosum, were reduced [15].