Literature review of Neonatal Microbiota: Implications for Health and Development

Abstract

The establishment of the neonatal microbiota is an essential process for the immunological, metabolic, and physiological development of newborn animals. Traditionally, it has been assumed that the intrauterine environment is sterile, and that microbial colonization begins only during birth and lactation. However, recent evidence from both human and veterinary medicine has challenged this paradigm by identifying viable bacteria and microbial DNA in the amniotic fluid, placenta, and meconium, suggesting that microbiota acquisition may begin in utero. This work is a literature review aimed at analyzing the origin, establishment, and progression of the neonatal microbiota in small animals (particularly dogs and cats), as well as its implications for neonatal health and development. It examines the role of the maternal microbiome (intestinal, vaginal, oral and mammary), along with the main factors that influence neonatal colonization, such as the mode of delivery, lactation, maternal contact (including licking), and the immediate environment. Furthermore, the relationship between microbiota alterations (dysbiosis) and common neonatal diseases. The reviewed evidence highlights that each mother possesses a unique microbial profile that significantly influences the initial composition of her offspring’s microbiome. Nevertheless, significant knowledge gaps remain, particularly in the veterinary field, underscoring the need for further research aimed at characterizing these microbial dynamics and their clinical impact.