Probiotic bacteria have been proposed as therapeutic option in several pathologic conditions, but their utilization is often not evidence-based driven. In inflammatory bowel disease (IBD), consistent heterogenity exists among published clinical studies. Aim of the present clinical study is to evaluate the effect of Lactobacillus rhamnosus GG (LGG), the probiotic bacteria most extensively investigated, with solid safety data and proven anti-inflammatory effect in experimental models, in ulcerative colitis (UC) patients, with a rigorous methodology, a well defined protocol, and with relevant outcomes clearly set.

This study is a randomized double-blind clinical trial that intends to evaluate the efficacy and safety of LGG administration at two different doses, for 1 month, in UC patients with mild-moderate disease activity in therapy with oral mesalamine.The eligible patients will be identified by a screening visit (T-1), with consideration of inclusion and exclusion criteria, and informed consent will be signed. Then the patients will have a 4 weeks wash-out period, when oral mesalamine will be suspended, and biochemical tests \[total blood count, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and serum protein electrophoresis\], and endoscopic examination with biopsies will be performed. The patients will be then evaluated again prior to the randomization to regular or double dose group (T0), and clinical activity and quality of life will be assessed. Patients will be randomized to assume a regular (LGG 1.2 × 10\^10 CFU/day, 2 capsules a day) or a double (LGG 2.4 × 10\^10 CFU/day, 4 capsules a day) dose of LGG for 1 month. After 4 weeks of treatment, patients will be re-evaluated (T1), with physical examination and interview, and rectum-sigmoidoscopy with biopsies will be performed. The patients will then be allowed to assume the therapy they were taking at T-1 visit (mesalamine), and will be assessed for the last time after 4 weeks after treatment completition (T2), with physical examination and interview. Efficacy of therapy will be evaluated by comparison of clinical, endoscopic, histological, biochemical and molecular data, pre- and post-treatment (T1 vs. T0). Randomization of patients in the groups will be performed by a computer-generated randomization list, in a double blind fashion. Clinical activity will be evaluated by Clinical Mayo Score calculation. Quality of life will be evaluated by specific validated tests. Endoscopic activity will be evaluated by Endoscopic Mayo Score calculation, by an endoscopist blinded to clinical data of patients. Histologic activity will be evaluated by expert anatomopathologists, by means of Geboes score. Molecular activity of LGG will be evaluated by assessment of bacteria adhesion to the colonic mucosa, measured by real-time(RT)-Polymerase Chain Reaction (PCR) with specific primers on total DNA extracted by bioptic samples (as already described), and by quantification of expression of pro- and anti-inflammatory cytokines, before and after probiotic treatment, by means of RT-PCR on total RNA extracted from bioptic samples (as already described).

Safety of LGG treatment will be assessed by weekly phone calls to the patients, in order to investigate the unexpected occurence of side-effects, and with direct physical examination and biochemical tests at the end of the study period (T1). Possible LGG translocation will be evaluated by RT-PCR with specific primers on total DNA extracted from peripheral blood collected from patients at the end of treatment (T1).