Effect of Multispecies Probiotic Supplementation on the Efficacy of Rifaximin α Therapy in Patients With Small Intestinal Bacterial Overgrowth (SIBO): a Randomized Placebo-controlled Trial (SIBO-Probiotic)

February 16, 2026 updated by: Państwowy Instytut Medyczny Ministerstwa Spraw Wewnętrznych i Administracji

Effect of Enterococcus Faecium and Bacillus Subtilis-Containing Multispecies Probiotic Supplementation on the Therapeutic Efficacy of Rifaximin α in Patients With Small Intestinal Bacterial Overgrowth (SIBO): a Prospective, Randomized, Placebo-controlled Trial

Small intestinal bacterial overgrowth (SIBO) is a common condition associated with gastrointestinal symptoms such as bloating, abdominal pain, diarrhea, and constipation, particularly in patients with irritable bowel syndrome. Antibiotic therapy with rifaximin is commonly used, but relapse rates remain high.

This randomized, placebo-controlled clinical trial aims to evaluate whether supplementation with a multispecies probiotic containing Enterococcus faecium and Bacillus subtilis improves the effectiveness of rifaximin therapy in adult patients with SIBO.

Participants will be randomly assigned to receive either rifaximin plus the probiotic or rifaximin plus placebo. Clinical assessments will include hydrogen breath testing and evaluation of gastrointestinal symptoms using standardized questionnaires at baseline and during follow-up visits.

The study is being conducted at a single academic medical center in Poland and is sponsored by Państwowy Instytut Medyczny MSWiA. The probiotic and rifaximin are provided by Urgo.

The results of this study may help determine whether probiotic supplementation can improve treatment outcomes and reduce recurrence of SIBO.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

100

Phase

  • Phase 4

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

  • Name: Aleksandra Perdek
  • Phone Number: 477221242

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age ≥18 years.
  • Meets Rome IV criteria for irritable bowel syndrome.
  • Written informed consent to participate in the study.

Exclusion Criteria:

  • Lack of cooperation with investigators.
  • Age >75 years.
  • Need for modification of gastrointestinal treatment during the study.
  • Use of antibiotics within 4 weeks before screening.
  • Use of probiotics within 7 days before screening.
  • Endoscopic examination within 6 weeks before screening or during the study without investigator approval.
  • History of abdominal surgery.
  • Crohn's disease, ulcerative colitis, microscopic colitis, celiac disease, cystic fibrosis, chronic pancreatitis, liver cirrhosis, or end-stage renal disease.
  • Low FODMAP diet within 4 weeks before screening.
  • Pregnancy or breastfeeding.
  • Lactulose intolerance.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Probiotic Group
Participants will receive rifaximin followed by the probiotic preparation according to the study protocol.
Dietary supplement: Probiotic preparation
Oral probiotic preparation administered once daily for 6 weeks following completion of antibiotic treatment for small intestinal bacterial overgrowth (SIBO). The product contains a defined combination of bacterial strains and is intended to support restoration of gut microbiota and reduce recurrence of SIBO.
Drug: Rifaximin (drug)
Rifaximin is administered to all participants as background standard therapy for SIBO at a dose of 1600 mg per day orally for 14 days. The randomized comparison concerns adjunctive probiotic versus placebo.
Placebo Comparator: Placebo Group
Participants will receive rifaximin followed by placebo according to the study protocol.
Drug: Rifaximin (drug)
Rifaximin is administered to all participants as background standard therapy for SIBO at a dose of 1600 mg per day orally for 14 days. The randomized comparison concerns adjunctive probiotic versus placebo.
Other: Placebo
Matching oral placebo capsule administered once daily for 6 weeks following completion of antibiotic treatment for small intestinal bacterial overgrowth (SIBO). The placebo is identical in appearance, taste, and packaging to the probiotic product but contains no live microorganisms.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
SIBO eradication rate
Time Frame: 4 weeks
Proportion of participants with eradicated small intestinal bacterial overgrowth (SIBO), defined as a negative hydrogen breath test, assessed 4 weeks after treatment initiation (rifaximin for 14 days plus probiotic for 4 weeks).
4 weeks

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
SIBO recurrence rate after completion of probiotic therapy
Time Frame: 10 weeks
Proportion of participants with recurrent SIBO, defined as a positive hydrogen breath test, assessed 4 weeks after completion of 6 weeks of probiotic supplementation following rifaximin treatment.
10 weeks

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Państwowy Instytut Medyczny Ministerstwa Spraw Wewnętrznych i Administracji

Collaborators

URGO Poland

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

February 15, 2026

Primary Completion (Estimated)

July 15, 2027

Study Completion (Estimated)

July 15, 2027

Study Registration Dates

First Submitted

February 16, 2026

First Submitted That Met QC Criteria

February 16, 2026

First Posted (Actual)

February 23, 2026

Study Record Updates

Last Update Posted (Actual)

February 23, 2026

Last Update Submitted That Met QC Criteria

February 16, 2026

Last Verified

February 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 34/BK/2025 (Other Identifier: PIM MSWiA)

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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