Colonization of the Gastrointestinal Tract in Neonates

Abstract

Bacterial colonization of the neonatal gastrointestinal tract has emerged as an issue involving nutrition, immunity, and overall mortality. Bacterial organisms colonizing the gastrointestinal tract play a vital role in maintaining intestinal homeostasis, including digestion, nutrient absorption, and immunological mechanisms. In neonates, these bacteria are essential in postnatal development of intestinal mucosa and gut-associated lymphoid tissue critical for immunological protection. Colonization of bacteria is thought to occur over the first 1 to 2 weeks of life. Delivery mode, feeding method, and environment affect the succession and establishment of the beneficial bacteria in the neonate. Neonates delivered vaginally are colonized by the bacteria from the mother, whereas neonates delivered via caesarean section initially colonize with bacteria from the environment. Feeding method is another factor; Bifidobacterium species are believed to dominate the microflora of breastfed infants by day of life 2 to 3 and are thought to be critical in postnatal immunology. Formula-fed infants often have a more diverse microflora and a less obvious presence of the Bifidobacterium. Compared with healthy, term neonates, preterm infants have a significant delay in bacterial colonization. The effects of an immature gastrointestinal track, lack of enteral feeding, and the frequent use of antibiotic therapy are believed to contribute to the delay and imbalance in the microflora of preterm infants. Prolonged exposure to hospital bacteria increases the risk of colonization with strains specific to hospital flora.