A Mini-review on Infant Microbiome: Inheritance, Development and Programmed Susceptibility to Contemporary Diseases

The infant microbiome is one of the most active and biologically important ecosystems in human physiology. The colonisation by microbes starts at birth and can even precede delivery, and then the process of ecological succession is extremely regulated in the initial months and years of life. This is a critical developmental period that overlaps with key immune developmental stages, metabolic programming, and neurodevelopmental stages, indicating that microbial exposures in infancy may have far-reaching and long-term effects on human health. The early microbial communities are conditioned by a variety of determinants such as mode of delivery, maternal microbiota, and breastfeeding, exposure to antibiotics, environmental hygiene, and more general lifestyle factors related to urbanisation. There is growing evidence that disturbances during early colonisation of microbes, also known as microbial symbiosis, can alter the path of physiological development of the host. Babies born through caesarean delivery, exposed to antibiotics early in life or reared in much sanitised homes often have distorted microbial composition and slow development of commensal populations that are beneficial. These disruptions can disrupt the immune education and metabolic signalling pathways, which are typically set up during host-microbe interactions. Therefore, there has been an increasing body of evidence showing that early-life symbiosis is linked to an increased risk of acquiring various non-communicable diseases in adulthood, such as asthma, allergic disorders, obesity, autoimmune diseases, and some neuro-developmental disorders. This review summarises existing information about vertical microbial transmission, the ecological succession of microbial communities in infancy, and the molecular pathways of host-microbe crosstalk. It also examines the ways in which disturbances in microbial colonization at this developmental period can predispose one to disease susceptibility in adulthood. The study of such initial microbial dynamics could provide the possibility of preventive measures that would help to maintain long-term health.