Microbial shifts in early life: the pediatric gut microbiome and its role in health and disease

Abstract

This review explores the pivotal role of the pediatric gut microbiome in shaping early-life development and influencing susceptibility to disease, emphasizing its impact on immune, metabolic, and neurodevelopmental processes. The neonatal period represents a critical window for host–microbiome interactions, beginning at birth when intestinal barrier function is still developing and immune responses remain immature. During this formative stage, rapid microbial colonization and ecological succession are influenced by delivery mode, infant feeding practices, antibiotic exposure, and environmental factors. Beyond bacterial populations, the early-life gut virome composed of bacteriophages and eukaryotic viruses evolves dynamically and contributes to microbial community structure, gene exchange, and immune system maturation. Microbially derived signals and metabolites support the development of mucosal integrity, immune programming, and host microbe equilibrium, with long-term implications for systemic immune function. Breastfeeding fosters the establishment of microbial communities and metabolic profiles associated with immune tolerance, whereas formula feeding and early-life antibiotic use may disrupt normal microbiome development. Alterations in early microbial trajectories have been associated with heightened risk of pediatric conditions, including allergic diseases, obesity, inflammatory bowel disease, and neurodevelopmental disorders. The review further evaluates emerging microbiome-directed strategies, such as probiotics, prebiotics, and fecal microbiota transplantation, considering both their therapeutic promise and current challenges. Collectively, current evidence underscores the early-life gut microbiome as a central determinant of host development and a compelling target for disease prevention strategies.