his is a single-center, prospective, single-arm, interventional clinical study to evaluate the clinical efficacy, safety, and potential mechanisms of washed microbiota transplantation (WMT) in patients with recurrent urinary tract infections (rUTI). Recurrent UTI is defined as ≥2 episodes within 6 months or ≥3 episodes within 1 year. Traditional management relies heavily on antibiotics, which often lead to gut dysbiosis and increased infection risk. WMT may reconstruct intestinal microbiota, restore colonization resistance, and modulate immunity through the gut-bladder axis. Approximately 30 eligible patients will receive WMT via mid-gut or colonic transendoscopic enteral tubing (TET) for 2-3 times according to the Nanjing Consensus on Washed Microbiota Transplantation. Participants will be followed for 12 months.

This study evaluates WMT as an interventional treatment for rUTI. WMT preparation follows the Nanjing Consensus on Washed Microbiota Transplantation (Chin Med J, 2020). Donor stool is obtained from healthy screened donors and processed using the GenFMTer intelligent fecal microbiota separation system with repeated washing and strict quality control.

Patients will receive WMT via mid-gut TET or colonic TET for 2-3 sessions. Clinical assessments include UTI episode frequency, symptom severity, antibiotic usage, and adverse events. Microbiological assessments include urine routine and clean-catch midstream urine culture during acute episodes. Fecal and urine samples will be collected at baseline (before TET placement), 3 months, and 6 months post-WMT for 16S rRNA gene high-throughput sequencing to analyze gut and urinary microbiota composition, alpha/beta diversity, and donor colonization via SourceTracker.

Inclusion Criteria:

1. Age ≥18 years, both sexes.
2. Meeting the diagnostic criteria for recurrent urinary tract infection: ≥2 symptomatic UTI episodes within 6 months or ≥3 episodes within 1 year.
3. Planning to receive washed microbiota transplantation (WMT) treatment.
4. Able to provide informed consent and comply with scheduled follow-up visits, examinations, and specimen collection.

Exclusion Criteria:

1. Received antimicrobial therapy within 48 hours before WMT.
2. Complicated UTI requiring surgical intervention, including urinary tract tumor, stricture, congenital malformation, or neurogenic bladder.
3. Co-infection with other urogenital pathogens including fungi, viruses, Mycoplasma, or Chlamydia.
4. Unable to tolerate gastroscopy or colonoscopy for TET tube placement.
5. Severe comorbidities involving heart, liver, kidney, hematopoietic system, respiratory system, or endocrine system that may affect survival, or other serious diseases affecting survival.
6. Pregnant or lactating women.
7. Coexisting psychiatric disorders.
8. Other conditions deemed unsuitable for enrollment by the investigator.