Effects of Probiotics on Respiratory Tract Infections in Children: A Randomized, Placebo-Controlled Interventional Study

This study is a 14-day, randomized, double-blind, placebo-controlled trial involving children aged 3 months to 6 years who meet clinical diagnostic criteria for mild to moderate upper respiratory tract infection (URTI). Participants are randomized to receive either a mixed probiotic preparation (Lactobacillus rhamnosus CRL1505 and Bifidobacterium breve M-16V) or a placebo. The primary clinical outcome assessed is the duration and severity of respiratory symptoms. Secondary outcomes include changes in gut microbiota composition, intestinal immune markers, and quality of life. To investigate potential mechanisms, fecal samples are collected before and after intervention for metagenomic sequencing to analyze microbial diversity and composition, alongside immunological assessments such as sIgA and calprotectin.