Preventing urinary tract infections in infants and children under 2 years with oral Escherichia coli strain Nissle 1917 probiotic: a randomized controlled trial

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What is this study about?

The study focuses on infants and young children under two years who have experienced a feverish Urinary tract infection, an infection of the bladder and the tubes that carry urine, or pyelonephritis, which is an infection of the kidney. It tests whether a daily oral dose of the probiotic E. coli Nissle, a preparation of live beneficial bacteria, can lower the chance of another infection, with the purpose of preventing recurrent infections.

The trial is randomized and double-blind, meaning participants are assigned by chance to receive either the probiotic or a placebo, and neither families nor doctors know which one is given. After completing the standard course of antibiotic treatment, the child takes the study liquid for about 30 days at home. Over the following six months, follow‑up visits and calls record any new infections, hospital stays, extra antibiotic use, and symptoms such as stomach pain or diarrhea, and a laboratory culture test may be used to confirm any new infection.

1 begin oral probiotic course

after the last dose of the antibiotic that treated the initial urinary tract infection, start taking the study medication at home.

the medication is an oral suspension called mutaflor (or a matching placebo).

take 2 doses of the suspension each day for a total of 30‑day course.

2 continue daily dosing for 30 days

administer the suspension once in the morning and once in the evening, or as instructed, for the full 30‑day period.

do not miss any doses; if a dose is forgotten, take it as soon as remembered unless it is close to the next scheduled dose.

store the suspension according to the packaging instructions.

3 complete the medication course

after 30 days, stop taking the oral suspension.

no further study medication is required.

4 monitor for recurrent infection during 6‑month follow‑up

for the next six months, watch for signs of a recurrent urinary tract infection such as fever, pain during urination, or abdominal discomfort.

if any symptoms appear, contact the child’s regular health care provider for evaluation.

the study will record any confirmed infections, hospital stays, antibiotic use, abdominal pain days, and diarrhoea days during this follow‑up period.

5 attend scheduled follow‑up visits

the protocol may include clinic visits at specified times within the six‑month follow‑up to collect information and samples.

bring the medication bottle and any symptom diaries to these visits.

Who Can Join the Study?

Child must be younger than 2 years old.
It must be the child’s first urinary tract infection diagnosed while in a pediatric emergency room or hospital ward.
A doctor must think a urinary tract infection is likely because a urine sample shows pyuria (white blood cells in the urine) and the child has symptoms such as fever or local urinary symptoms.
No other more likely cause for the symptoms may be identified.
If a bacterial culture (lab test that grows bacteria from the urine) is available, it must show bacteria that support the infection diagnosis.
A final culture result is not required if the other criteria are met and the child is being discharged with a urinary tract infection diagnosis.
Both boys and girls are eligible.
Use of other probiotic products is allowed, but it must be recorded by the study team.
Parents or legal guardians must give informed consent for the child to join the study.
The child must be recruited at one of the participating hospitals in Finland.

Who Cannot Join the Study?

Prematurity: children who were born before 35 weeks of pregnancy.
Severe infection: a life‑threatening infection such as E. coli meningitis (meningitis means a serious infection of the brain’s protective covering).
Urinary tract anomaly: any major blockage or defect in the urinary system that would need care from a urologist (a doctor who treats the kidneys, bladder, and related organs).
Immunodeficiency: a condition where the immune system (the body’s defense against germs) is weak.
Bowel anomaly: an abnormal condition of the intestines (the part of the body that digests food).
Current medication: regularly taking antibiotic prophylaxis (antibiotics used every day to try to prevent infections).
Hospital‑acquired infection: an infection caught while in the hospital, especially one related to a catheter (a thin tube placed in the body to drain fluids).

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country	Status
Kuopio University Hospital	Kuopio	Finland

Other Sites

Site Name	City	Country
Turku University Hospital	Turku	Finland
Pirkanmaan hyvinvointialue	Tampere	Finland
Oulu University Hospital	Oulu	Finland
Vaasa Central Hospital	Vaasa	Finland
Hsplzfyk Ubdholxadl Cmwpowd Hfywvpap	Helsinki	Finland

Trial status

Country	Status	Recruitment Start
Finland	Not yet recruiting	17.08.2026

Trial locations

Investigated Drugs:

Escherichia Coli Strain Nissle 1917

Mutaflor is an oral suspension that contains a harmless strain of the bacteria Escherichia coli called Nissle 1917. In this trial the product is given to infants and young children after they finish a course of antibiotics for a urinary tract infection. The goal is to see if the probiotic can help prevent another infection by supporting a healthy balance of bacteria in the gut and urinary tract. Children take the suspension by mouth for about a month.

Urinary tract infection – Urinary tract infection is an infection of the urinary system, most often affecting the bladder and urethra. It begins when bacteria enter the urethra and multiply in the bladder, causing discomfort during urination. Symptoms may start as mild irritation and can become more pronounced as the infection spreads. When the infection ascends to the kidneys, it is called pyelonephritis, leading to fever and back pain. In young children, the infection can recur, with each episode following a similar pattern of symptoms.

Trial ID:

2026-526444-13-01

NCT ID:

NCT04608851

Trial Phase:

Therapeutic confirmatory (Phase III)

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Preventing urinary tract infections in infants and children under 2 years with oral Escherichia coli strain Nissle 1917 probiotic: a randomized controlled trial

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?