Quantitative analysis of intestinal bacterial populations from term infants fed formula supplemented with fructo-oligosaccharides

Objectives: Previous studies of infant formulas supplemented with oligosaccharides reported mixed results regarding the impact on intestinal microbial populations. The objective of this study was to examine the effect of supplementation of an infant formula with fructo-oligosaccharides (FOS) on select groups of intestinal bacteria in term infants. Methods: Four groups of infants were enrolled and fed human milk, a commercially available milk-based infant formula, or infant formula supplemented with 2.0 or 3.0g/L FOS. Dietary intake, stool, and tolerance events were recorded. Fresh stool samples were collected approximately 27 days after feeding the diets (approximately 32 days after birth). Total bacteria, Bacteroides (as commensal bacteria), Bifidobacterium and Lactobacillus, and Clostridium difficile and Escherichia coli were quantified using respective specific real-time PCR assays. Results: The formula feeding groups did not differ in stool consistency and stool frequency or frequency of spit-up or vomit during the entire study. The formula-fed infants tended to have more total bacteria in their stool samples than the human milk-fed infants. The formula-fed infants harbored a greater abundance of C difficile and E coli than the human milk-fed infants, but had a similar abundance of Bacteroides, Bifidobacterium, and Lactobacillus. The FOS supplementation at either dose did not significantly increase the bifidobacterial or lactobacilli populations, or decrease the populations of C difficile, E coli, or Bacteroides. Conclusions: The milk-based formula used in this study supported bifidobacterial and lactobacilli populations comparable with the human milk group; however, this formula did not suppress E coli or C difficile as effectively as human milk.