Duytschaever, et al.13 also reported a lower total richness index (TRI, using the number of bands in denaturing gradient gel electrophoresis) for bacterial species in the gut of CF patients compared to controls, but comparisons were made with siblings of CF patients (which we avoided in this study since there is a higher probability of heterozygotes among among affected siblings, who may thus have mild degrees of CFTR dysfunction28, 29, 30) and no temporal changes in TRI were described. This evidence concerns the gene CFTR and cystic fibrosis.