Gut Microbiota, Neuroinflammation, and Postbiotic-Based Interventions in Autism Spectrum Disorder and Developmental Speech and Language Delay: Retrospective Observational Case Series of 42

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition increasingly associated with gastrointestinal dysfunction, immune dysregulation, neuroinflammation, and alterations in gut microbial composition. Growing evidence supports the role of the gut–brain axis as an important mediator linking intestinal health and neurodevelopmental outcomes. To review current evidence regarding the relationship between the gut microbiome, neuroinflammation, and ASD, and to describe clinical observations obtained from a retrospective observational cohort of children participating in a microbiome-oriented supportive intervention program. This retrospective observational case series included 42 children aged 1–6 years diagnosed with Autism Spectrum Disorder (ASD) and/or Developmental Speech and Language Delay (DSLD). Clinical evaluation included assessment of gastrointestinal symptoms, nutritional deficiencies, developmental characteristics, laboratory findings, and available microbiome analyses, including 16S rRNA sequencing in a subset of participants. Children received microbiome-oriented supportive interventions that included postbiotic-based therapy, dietary modification, nutritional correction, and individualized supportive measures. Clinical outcomes were assessed descriptively during follow-up periods of up to 15 months. Gastrointestinal symptoms were present in 90.5% of participants, food selectivity in 85.7%, sleep disturbances in 83.3%, attention difficulties in 81.0%, hyperactivity in 78.6%, and speech delay in 95.2%. Across clinical subgroups, a characteristic temporal sequence of improvement was observed. Early changes (1–3 days) primarily involved gastrointestinal function, including normalization of bowel habits and reduction of abdominal discomfort. Intermediate improvements (3–4 weeks) were observed in sleep quality, appetite, emotional regulation, and behavioral stability. Later improvements (8–12 weeks) involved communication, social engagement, attention, and speech development. No serious adverse events were reported. The observations presented in this cohort support the growing body of evidence linking gastrointestinal health, microbial metabolism, immune regulation, and neurodevelopment. A characteristic sequence of clinical improvements was observed, with gastrointestinal changes preceding behavioral and neurodevelopmental improvements. Although causal relationships cannot be established within an observational study, the findings support further investigation of microbiome-oriented and postbiotic-based interventions in prospective controlled trials involving children with ASD and Developmental Speech and Language Delay.