The Effect of a Probiotic Containing Lacticaseibacillus rhamnosus and Bifidobacterium longum subsp. infantis on Clinical Outcomes in Children Aged 2–10 Years with Recurrent Upper Respiratory Tract Infections: A Multicenter Cohort Study

ABSTRACT Aim: To evaluate the effects of a probiotic combination containing Lacticaseibacillus rhamnosus GG and Bifidobacterium longum subsp. infantis on the frequency of upper respiratory tract infections (URTI), antibiotic use, school absenteeism, and gastrointestinal microbiota parameters in children aged 2–10 years with recurrent URTI. Materials and Methods: This retrospective, observational, controlled, multicenter cohort study was conducted across nine pediatric outpatient clinics in Türkiye. The study enrolled 200 children aged 2–10 years with a history of at least three URTI episodes in the preceding six months. Children were assigned to two groups: Group 1 (n=100) received a daily six-drop Lacticaseibacillus rhamnosus GG + Bifidobacterium longum subsp. infantis probiotic combination in addition to standard care; Group 2 (n=100) received standard care alone. Clinical parameters were assessed at baseline (V0), month 3 (V1), and month 6 (V2). Mann-Whitney U and chi-square tests were used for between-group comparisons; Wilcoxon signed-rank test was applied for within-group longitudinal analysis. Results: In Group 1, the mean number of URTI episodes decreased from 4.05±0.95 at V0 to 1.39±1.04 at V2 (p<0.001; 65.7% reduction), whereas no significant change was observed in the control group (2.06→2.09; p=0.592). Antibiotic use declined by 58.7%, school absenteeism by 70.9%, and febrile days by 55.5% in Group 1 (all p<0.001). More pronounced clinical improvement was observed in subgroups of children born by cesarean section, those who received no breast milk, and those with a history of frequent antibiotic exposure. Product adherence was 97.5±4.4% and no adverse events were reported. Conclusion: The Lacticaseibacillus rhamnosus GG + Bifidobacterium longum subsp. infantis probiotic combination significantly reduces both infection burden and antibiotic use in children with recurrent URTI, with particularly marked clinical efficacy in cesarean-born children, those with minimal breast milk exposure, and those with high prior antibiotic use.