Effect of Probiotics on the Intestinal Microbiota of Pediatric Patients

Inclusion Criteria: * Children aged 3 to 7 years old. * Diagnosed with autism spectrum disorder, according to the clinical criteria of the "Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)" and who meet criteria for ASD according to the ADOS-2 classification. * Presenting one or more gastrointestinal symptoms (constipation, diarrhoea, abnormal stools, painful defecation, abdominal pain, reflux, bloating, flatulence). * Written informed consent signed by the parent or legal guardian with express or tacit consent of the other parent. Exclusion Criteria: * With intake of antibiotics in the last month. * With intake of probiotics in the last two weeks. * Diagnosed with short bowel syndrome or has undergone relevant surgery on the gastrointestinal tract. * Exhibiting a defect in the intestinal epithelial barrier (e.g. inflammatory bowel disease (IBD)). * Diagnosed with endocrinological diseases such as diabetes mellitus, hypo- and hyperthyroidism, Cushing's disease, Addison's disease, etc. * Having heart failure and a cardiac medical history (e.g. artificial heart valve, medical history of infective endocarditis, rheumatic fever, or cardiac malformation). * Congenital or acquired immunodeficiency. * Immunocompromised (e.g., cancer and/or transplant patients taking certain immunosuppressive drugs, patients with inherited diseases that affect or may affect the immune system). * Uncertainty on the part of the investigator about the willingness or ability of the minor's parents or legal guardian to comply with the requirements of the protocol. * With oral hyper sensitivity impairments that prevent the uptake of the study product.