Another factor affecting the intestinal flora of the newborn is delivery mode. A normal vaginal delivery commonly permits transfer of bacteria from the mother to the infant. During cesarean deliveries, this transfer is completely absent. These infants commonly acquire and are colonized with flora from the hospital's environment and, therefore, their flora may differ from maternal flora. Infants delivered by cesarean section are colonized with more anaerobic bacteria, especially Bacteroides, than vaginally delivered infants. Clostridium perfringens is the anaerobic bacterium most frequently isolated after cesarean deliveries. When colonized, cesarean delivered infants less frequently harbor E. coli, and more often klebsiella and enterobacteria(7).
The initial colonizing bacteria vary with the food source of the infant. In breast-fed infants, Bifidobacteria account for more than 90% of the total intestinal bacteria. The low concentration of protein in human milk, the presence of specific anti-infective proteins such as immunoglobulin A, lactoferrin, lysozyme, and oligosacharides (prebiotics), as well as production of lactic acid, cause an acid milieu and are the main reasons for its bifidogenic charachtersitics. In bottle-fed infants, Bifidobacteria are not predominant(13). Instead enterobacteria and gram-negative organisms dominate because of a more alkaline milieu and the absence of the prebiotic modulatory factors present in breast milk.
Colonized with the bacteria from the hospital? YUCK! This is of particular interest to me since Hannah was a c-section baby.
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