Considering that PI-IBS is brought on by infection and gut microbiota may be associated with the onset of symptoms, the modification of altered gut microbiota with nonabsorbable antibiotics such as rifaximin-α or probiotics is often employed as first-stage treatment. Research in recent years has also shown the potential benefits of fecal microbiota transplantation (FMT) for IBS, which is the replacement of a sick recipient's gut microbiota with fecal material from a healthy donor. Even though the only officially approved indication for FMT at this time is recurrent Clostridium difficile infection, the effectiveness of FMT is nevertheless being studied for the treatment of other gastrointestinal and non-gastrointestinal pathologies including IBS. To date, several controlled and uncontrolled studies have been conducted to study the effectiveness of FMT for IBS, and most of them have demonstrated positive results. The investigators have not come across studies devoted to the study of the effectiveness of FMT in patients with PI-IBS in the available literature. So, the aim of the current study was to conduct single-centre, randomized clinical trial to assess the safety, clinical and microbiological efficacy of FMT in patients with PI-IBS.

Inclusion Criteria

• age 18-65 years
• PI-IBS diagnosis in accordance with the Rome IV criteria
• moderate-severe disease activity (as determined by an IBS-Symptom Severity Score ≥175)
• normal appearing colon on colonoscopy with biopsy that did not reveal pathology
• signed inform consent.

Exclusion Criteria:

• systemic disease, immunodeficiency, or previous treatment with immunomodulators;
• pregnant or breastfeeding;
• previous surgery on the abdominal cavity, with the exception of appendectomy, cholecystectomy, caesarean section and hysterectomy;
• severe current disease (hepatic, renal, respiratory, or cardiovascular);
• probiotic or antibiotic use within 8 weeks prior to study initiation;
• any condition or circumstance that would, in the opinion of the investigator, prevent completion of the study or interfere with analysis of study results.