Acute diarrhea due to infectious causes is a major source of morbidity in the pediatric population.

Although it is generally self-limiting, acute diarrhea may lead to severe dehydration, hospitalization, and, rarely, death, particularly in young children. Numerous studies have investigated the role of probiotics and other microbiota-targeted therapies in improving the clinical course of infectious acute diarrhea.

The first multicenter PROBAGE study conducted in Türkiye 15 years ago provided valuable evidence regarding the efficacy of probiotics in this context. Over the past 15 years, changes in epidemiology-especially in the post-pandemic period-have created a need for new studies evaluating the effectiveness of probiotics in acute diarrhea.

The PROBAGE 2.0.1 study is designed to evaluate the efficacy of Lactobacillus rhamnosus GG in the treatment of acute infectious diarrhea in children in Türkiye. This is a multicenter, prospective, randomized, open-label, controlled clinical trial, to be conducted across seven tertiary care medical centers nationwide. A total of 480 children with acute infectious diarrhea will be enrolled.

At the initial presentation, stool samples will be collected to identify rotavirus, norovirus, and adenovirus as causative pathogens. The treatment group (n = 240) will receive standard of care plus Lactobacillus rhamnosus GG (one sachet twice daily for 5 or 10 days), whereas the control group (n = 240) will receive standard of care alone.

Daily monitoring of stool frequency and consistency will be documented for 10 days, by families for outpatients and by physicians and nurses for hospitalized patients. Provided that sufficient data are obtained, data analysis and publication phases will be completed.

Inclusion Criteria:

• Children aged 1 month to 10 years presenting with acute infectious diarrhea (for S. boulardii group)
• Children aged 2 to 10 years presenting with acute infectious diarrhea (other probiotics or synbiotics groups)
• Onset of diarrhea symptoms within the last 48 hours.
• Parental/legal guardian consent obtained.

Exclusion Criteria:

• Use of any probiotics or biotic formulations within the past 8 weeks.
• Use of antibiotics in the last 8 weeks.
• Presence of chronic diseases (e.g., diabetes, congenital heart disease, immunodeficiencies).
• Previous gastrointestinal surgical procedures.