Intestinal Microbiota After PPI Treatment

"* Drug: Esomeprazole, a proton pump inhibitor commonly used in pediatric gastroenterology.~* Administration: Oral, once daily, 30 minutes before meals.~* Dosage: Personalized dosing according to body weight, with an average of approximately 0.6 mg/kg/day.~* Treatment duration: Minimum 45 days, maximum 60 days.~* Comparator: None. This is a within-subject design; each participant serves as their own control with baseline samples (t0) compared to follow-up (t1-t2).~* Monitoring: Adherence to therapy and sample collection timeline will be verified during scheduled clinical follow-up."