Survival of the Probiotic Escherichia coli Nissle 1917 (EcN) in the Gastrointestinal Tract Given in Combination with Oral Mesalamine to Healthy Volunteers

Background: Mesalamine and the probiotic E. coli Nissle 1917 (EcN) are both effective agents for the treatment of ulcerative colitis. A combined therapy may have more than additive efficacy. However, mesalamine may have antimicrobial effects on EcN. Materials and Methods: In this prospective, randomized, double-blind, placebo-controlled study, 48 healthy volunteers took EcN in a run-in phase for 17 days (5-50 x 10(9) viable bacteria od). If stool samples became positive for EcN, volunteers received combination treatment with EcN plus either mesalamine (1500 mg twice a day) or placebo for I week. Fecal samples were further tested for EcN in 2- to 3-day intervals until a maximum of 48 weeks after treatment. Patient diaries, blood, and urine were checked to assess safety, compliance, and tolerance. Results: During run-in, viable EcN were detected in 45 of the 48 volunteers (94%); 2 volunteers were positive before taking EcN. From days I to 7 of combination treatment (n = 40), the number of EcN-positive volunteers varied between 70% and 80% in the mesalamine group and between 85% and 95% in the placebo group. Differences between the groups were not significant (normal approximation: day 3, P > 0.15; day 5, P > 0.25; day 7, P > 0.076). At treatment discontinuation, 16 of 20 volunteers in the mesalamine group and 15 of 20 volunteers in the placebo group were EcN positive, whereas this figure dropped continuously up to week 12 after discontinuation (mesalamine, 7 of 20; placebo, 4 of 20). No differences between the groups were seen with regard to tolerance and safety. Conclusions: The combination of EcN and mesalamine has no significant effect on the survival of EcN in healthy volunteers.