Inclusion Criteria:

• diagnosis of Crohn's disease localised in the ileum and/or colon, documented either radiologically or endoscopically at least 3 months previously;
• patients with a CDAI of ≥ 220 to ≤ 400;
• patients capable of and willing to conform to the study protocol;
• patients who have provided signed and dated written informed consent.

Exclusion Criteria:

• patients potentially needing immediate surgery for Crohn's disease, including patients with occlusive symptoms and/or stenotic tract with dilation above;
• patients with active perianal Crohn's disease;
• patients with other infectious, ischemic, or immunological diseases with gastrointestinal involvement;
• patients with symptoms attributed to Short Bowel Syndrome or previous surgery;
• patients with stoma;
• patients affected by upper gastro-intestinal disease (gastro-duodenum-jejunum Crohn's disease) alone or in combination with colitis or ileitis;
• patients treated with: oral steroids and budesonide less than 30 days prior to screening; i.v. steroids less than 30 days prior to screening; antibiotics (such as metronidazole, tinidazole, ciprofloxacin, clarithromycin) less than 15 days prior to screening;
• rectal steroids less than 30 days prior to the screening visit;
• anti-tumour necrosis factor (anti-TNF) and other biological therapies less than 6 months prior to the screening visit;
• pregnant women or nursing mothers;
• females of childbearing age (unless surgically sterile) without a negative urine pregnancy test at screening and at enrolment;
• patients with severe hepatic insufficiency (Child C);
• patients with severe cardiac insufficiency (NYHA - New York Heart Association classes 3 - 4);
• patients with known hypersensitivity to Rifaximin;
• any condition or circumstance that would prevent completion of the study or interfere with analysis of study results, including a history of drug or alcohol abuse, mental illness or non-compliance with treatments or visits, with immunological (including HIV infection), haematological or neoplastic disease;
• withdrawal of informed consent;
• patients who have used any investigational drug (except biological therapies) within 3 months prior to screening;
• patients who have donated 250 ml or more of blood in the last 3 months.