Development and differences of intestinal flora in the neonatal period in breast-fed and bottle-fed infants.

The development of stool bacterial flora was studied in breast-fed and bottle-fed infants. In both groups of infants, the intestine was first colonized with enterobacteria and their number attained 10(9) per gram of feces. On day 6, bifidobacteria were the predominant organisms in the stool of breast-fed infants, exceeding enterobacteria by a ratio of 1,000:1, whereas enterobacteria were the predominant organisms in formula-fed infants, exceeding bifidobacteria by approximately 10:1. At 1 month of age, bifidobacteria were the most prevalent organisms in both groups but the number of these organisms in the stool of bottle-fed infants was approximately one tenth that of breast-fed infants. The properties of breast milk that promote the growth of bifidobacteria and suppress the growth of coliform and other potentially pathogenic organisms, theoretically, would help to minimize the incidence of neonatal diseases caused by these organisms. The results would support the advantages of breast-feeding for optimal care of newborn infants.