This randomized controlled trial evaluated the effect of a combination of Lactobacillus acidophilus DSMZ 26280 and Limosilactobacillus reuteri DSMZ 25441 on the duration of diarrhea and gut microbiota composition in children aged 1-6 years with acute infectious diarrhea.

This prospective, randomized, controlled, open-label clinical trial was conducted between March 2024 and August 2024 at the Pediatric Emergency Department of Prof. Dr. İlhan Varank Sancaktepe Training and Research Hospital, Istanbul, Türkiye. Children aged 1-6 years presenting within 24 hours of onset of acute infectious diarrhea were randomized 1:1 to receive standard therapy (oral rehydration solution with or without intravenous fluids) alone or in combination with a probiotic preparation containing Lactobacillus acidophilus DSMZ 26280 (1×10⁸ CFU) and Limosilactobacillus reuteri DSMZ 25441 (1×10⁸ CFU) administered once daily for 5 days.

The primary outcomes were duration of diarrhea and the proportion of children who were diarrhea-free at 72 hours. Secondary outcomes included the proportion of children with diarrhea during the first 10 days of follow-up. A subgroup underwent longitudinal gut microbiota analysis at baseline, day 10, and day 30 using 16S rRNA sequencing.

The study was approved by the Ethics Committee of Prof. Dr. İlhan Varank Sancaktepe Training and Research Hospital (approval date April 17, 2024; decision no: 126), and written informed consent was obtained from all parents or legal guardians.

Inclusion Criteria:

• Children aged 1-6 years
• Clinical diagnosis of acute infectious diarrhea
• Presentation within 24 hours of symptom onset
• Mild or no dehydration
• Written informed consent from parents or guardians

Exclusion Criteria:

• Antibiotic or probiotic use within the previous month
• Moderate or severe dehydration
• Malnutrition
• Immunosuppression
• Chronic systemic disease