Effect of a Probiotic or Postbiotic on Gut Microbiome During Antibiotic Treatment (POTATO-2)

Assessment Of Gut Microbiome Changes During Antibiotic Treatment With Probiotic, Postbiotic Or Placebo: A Randomized, Triple-blind, Placebo-controlled Pilot Study.

This study assesses the effects of a probiotic or postbiotic on gut microbiome during antibiotic treatment.

Study Overview

• Status: Not yet recruiting
• Conditions: Microbiome
• Intervention / Treatment: Dietary supplement: Probiotic; Dietary supplement: Postbiotic; Dietary supplement: Placebo

Detailed Description

The current study aims to assess the changes in microbiome composition in healthy adults receiving antibiotic treatment, and concomitantly a probiotic or postbiotic. The trial will be run in Greece, and will recruit healthy adults from the general population.

• Study Type: Interventional
• Enrollment (Estimated): 126
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: ADM Medical Team; Phone Number: +441460243230; Email: medical@protexin.com

Study Locations

• Greece
  • Thessaloniki, Greece, 56429
    • General Hospital Of Thessaloniki Papageorgiou
    • Contact: Theodoridou; Phone Number: +30 210 6147282; Email: maria.theodoridou@nextcro.eu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

Participants meeting ALL of the following criteria will be recruited for the study:

• Males and females aged ≥18 to ≤ 65 years; if female, either not of childbearing potential or using a medically approved method of birth control and willing to take a pregnancy test at screening.
• Body mass index (BMI) 18.5-29.9 kg/m².
• Healthy as determined by medical history and physical examination.
• Agreed not to change current dietary habits during the course of the study.
• Able to attend study visits, comply with study requirements (consumption of study medications, especially biological sample collection procedures, and study visit schedule) and provide reliable and complete data regarding AEs/SAEs and PROs.
• Have been informed and have given written consent for the use of their data in accordance with local regulations before study inclusion.

Exclusion Criteria:

Participants meeting ANY of the following criteria will be excluded from the study:

• Women who are pregnant, breastfeeding, or planning to become pregnant during the course of the study.
• People on vegetarian or vegan diet; People on special diet (e.g. Ducan, Keto, etc.)
• BMI ≥ 30 kg/m² or <18.5 kg/m².
• History of intake of antibiotics, other probiotics, postbiotics, prebiotics, synbiotics, proton pump inhibitors, acid sequestrants (cholestyramine, Bile colestipol), within six months prior to the screening day.
• Participation in other clinical trials in the last 90 days prior to screening.
• Allergy to any penicillin antibiotic or any other beta-lactam agent (e.g. cephalosporin, carbapenem or monobactam).
• History of jaundice/hepatic impairment due to amoxicillin/clavulanic acid.
• Active smokers or using any form of smokeless tobacco.

• Participants with substance abuse problems (within two years) defined as:

  • Use of recreational drugs (such as cocaine, methamphetamine, marijuana, etc.)/ Nicotine dependence.
  • High-risk drinking as defined by the consumption of four or more alcohol-containing beverages on any day or eight or more alcohol-containing beverages per week for women and five or more alcohol-containing beverages on any day or 15 or more alcohol-containing beverages per week for men.
• Participants having clinically significant illnesses of cardiovascular, endocrine, immune, respiratory, hepato-biliary, kidney and urinary, haematological, musculoskeletal system and/or any inflammatory disorder, tumour, and other gastrointestinal diseases.
• Participants with a history of bariatric surgery or surgical resection of the stomach, small intestine, or large intestine.
• Participants actively using GLP1 agonist drugs (Wegovy, Semiglutide etc.) or completed treatment with said medication less than 12 weeks before screening.
• Any condition that could, in the opinion of the Investigator, preclude the participant's ability to successfully and safely complete the study or that may confound study outcomes.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Probiotic; Participants in this arm will receive a daily dose of a daily dose of of a probiotic (live bacterium), in a form of 2 capsules once daily, for 28 days.	Dietary supplement: Probiotic; Participants in this arm will receive a daily dose of of a probiotic (live bacterium), in a form of 2 capsules once daily, for 28 days.
Experimental: Postbiotic; Participants in this arm will receive a daily dose of a postbiotic (heat-inactivated bacterium), in a form of 2 capsules once daily, for 28 days.	Dietary supplement: Postbiotic; Participants in this arm will receive a daily dose of a postbiotic (heat-inactivated bacterium), in a form of 2 capsules once daily, for 28 days.
Placebo Comparator: Placebo; Participants in this arm will receive an equivalent placebo for the duration of the study (28 days).	Dietary supplement: Placebo; Participants in this arm will receive an equivalent placebo for the duration of the study (28 days).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in gut microbiome composition between baseline and day 14 as compared to placebo.	To assess the effects of a probiotic or postbiotic in gut microbiome composition of healthy adults receiving antibiotic therapy, as measured by changes in alpha and beta diversity of the gut microbiome as compared to placebo.	Day 0 and Day 14

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in gut microbiome composition throughout the study as compared to placebo and baseline.	Changes in microbiome composition as measured by changes in alpha and beta diversity of the gut microbiome throughout the study as compared to placebo and baseline.	Day 0, Day 3, Day 7, Day 28, and Day 56
Changes in abundance of beneficial versus opportunistic/ pathogenic bacterial species throughout the study as compared to baseline and to placebo	Effects of a probiotic or postbiotic on the abundance of beneficial versus opportunistic/pathogenic bacterial species throughout the study as compared to baseline and to placebo.	Day 0, Day 3, Day 7, Day 14, Day 28, and Day 56
Changes in the abundances of microbial genes contained in specific functional modules through the study as compared to baseline and placebo.	Effects of probiotic or postbiotic on the abundances of genes contained in specific functional modules obtained from KEGG database. A Gene Set Enrichment Analysis (GSEA) is performed to obtain which modules are enriched by the biotics effect thought the study. Significant associations will be reported with the Normalized Enrichment score (NES) and adj.p.value.	Day 0, Day 7, Day 14, Day 28, and Day 56
Study the associations of specific microbe abundances with the development of gastrointestinal (GI) symptoms	Association between each bacterial abundance and the clinical measures, related to GI symptoms, will be performed using linear models. Significant associations will be reported with the linear model coefficient and adj.p.value.	Day 0, Day 3, Day 7, and Day 14
.Changes in the abundances of microbial virulence factors and antibiotic resistant genes through the study as compared to baseline and placebo.	Effects of probiotic or postbiotic on the abundances of genes annotated as virulence factors or antibiotic resistant genes through the study as compared to baseline and placebo. The results will be tested using the most fitting statistical method, and p.value will be reported.	Day 0, Day 7, Day 14, Day 28, and Day 56
Safety profile throughout the study as compared to placebo.	The number of adverse events (AE)/serious adverse events (SAE) related to the study investigational product occurring during the study compared to placebo.	56 days
Tolerability of a probiotic or postbiotic as measured by a validated questionnaire and compared to placebo.	Assess tolerability of a probiotic or postbiotic consumption as measured by a validated questionnaire, the Gastrointestinal Symptom Rating Scale (GSRS) throughout the study and compared to baseline and placebo.	Day 0, Day 7, Day 14, Day 28, and Day 56

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Effects on development of antibiotic-associated diarrhea (AAD) as compared to placebo.	Efficacy of probiotic or postbiotic on incidence of diarrhea or AAD during and after antibiotic therapy as assessed by frequency and form of daily bowel movements measured with Bristol Stool Form Scale (BSFS). BSFS scale ranges from 1 to 7 with scores 1-2 indicating hard and lumpy bowel motions and 6-7 indicating runny, watery stools.	56 days
Effects on duration of diarrhea or AAD if presented during the study as compared to placebo.	Efficacy of probiotic or postbiotic on the duration of diarrhea or AAD, if present, as assessed by Bristol Stool Form Scale (BSFS). BSFS scale ranges from 1 to 7 with scores 1-2 indicating hard and lumpy bowel motions and 6-7 indicating runny, watery stools.	56 days

Collaborators and Investigators

• Sponsor: The Archer-Daniels-Midland Company
• Collaborators: NEXT CRO

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): May 31, 2027
• Study Completion (Estimated): May 31, 2027

Study Registration Dates

• First Submitted: April 28, 2026
• First Submitted That Met QC Criteria: May 12, 2026
• First Posted (Actual): May 19, 2026

Study Record Updates

• Last Update Posted (Actual): May 19, 2026
• Last Update Submitted That Met QC Criteria: May 12, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Antibiotic; Probiotic; Dysbiosis; Microbiome composition; Postbiotic; Antibiotic Resistance Genes; Microbiome Recovery; Antibiotic Scarring
• Additional Relevant MeSH Terms: Pathologic Processes; Pathological Conditions, Signs and Symptoms; Dysbiosis; Dietary Supplements; Food; Diet, Food, and Nutrition; Physiological Phenomena; Food and Beverages; Probiotics
• Other Study ID Numbers: CTB2024TN403

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No