Bacterial colonization of the large intestine in newborns delivered by cesarean section.

Colonization of the gastrointestinal tract in newborns delivered by Cesarean section occurs during the first days of life by bacteria provided by the environment. It is more rapid in breast-fed infants than in bottle-fed babies. The intestinal flora is more diversified if the infants receive formula feeding. The first bacteria encountered are facultative anaerobes; they remain predominant during the first two weeks of life. In comparison to vaginal delivery, there were low levels of strict anaerobes after Cesarean section; members of the Bacteroides fragilis group were still completely lacking after 14 days of life and Bifidobacteria were only isolated sporadically.