Background: Exclusive enteral nutrition (EN) is an established primary therapy for pediatric Crohn's disease (CD). The mechanism of action of such treatment is still conjectural. The aim of the present study was to investigate if EN-induced remission is associated with modification of the fecal microflora in CD. Methods: Stool samples were collected from 5 healthy children and adolescents over a period of 3 months, and from 9 children and adolescents with active CD. To induce disease remission, children with CD received a course of exclusive EN for 8 weeks with a polymeric formula (Modulen IBD, Nestle). At the end of the course of exclusive EN, children returned to a free diet but continued to take 40% of the daily caloric intake as polymeric formula. Fecal microflora was analyzed by 16S ribosomal DNA polymerase chain reaction and temperature gradient gel electrophoresis (TGGE) with direct visual comparison of band profiles of PCR products. Results: In 8 of 9 children, the exclusive EN alone induced disease remission. In 1 child, it was necessary to add steroids to the exclusive EN course to achieve remission. In all children with CD, analysis of gel band distribution revealed profound modification of the fecal microflora after exclusive EN. Variations of band distribution corresponding to different bacterial species were observed also in children on partial EN and required time to achieve stability of the band profile. In contrast, control healthy children showed a host-specific and stable TGGE profile over time. Conclusion: These data suggest that a possible mechanism of action of EN in inducing disease remission in CD is the capacity of modification of gut microflora. Possible explanations of such capacity are both low residue and prebiotic properties of the polymeric liquid formula.
