Effect of a milk formula with prebiotics on the intestinal microbiota of infants after an antibiotic treatment.

Antibiotics exert deleterious effects on the intestinal microbiota, favoring the emergence of opportunistic bacteria and diarrhea. Prebiotics are nondigestible food components that stimulate the growth of bifidobacteria. Our aim was to evaluate the effects on the intestinal microbiota of a prebiotic-supplemented milk formula after an antibiotic treatment. A randomized, double-blind, controlled clinical trial was carried out in 140 infants 1-2 y of age distributed into two groups after a 1-wk amoxicillin treatment (50 mg/kg/d) for acute bronchitis. The children received for 3 wk >500 mL/d of a formula with prebiotics (4.5 g/L) or a control without prebiotics. Fecal samples were obtained on d -7 (at the beginning of the antibiotic treatment), on d 0 (end of the treatment and before formula administration), and on d 7 and 21 (during formula administration). Counts of Bifidobacterium, Lactobacillus-Enterococcus, Clostridium lituseburiense cluster, Clostridium histolyticum cluster, Escherichia coli, and Bacteroides-Prevotella were evaluated by fluorescent in situ hybridization (FISH) and flow cytometry. Tolerance and gastrointestinal symptoms were recorded daily. Amoxicillin decreased total fecal bacteria and increased E. coli. The prebiotic significantly increased bifidobacteria from 8.17 +/- 1.46 on d 0 to 8.54 +/- 1.20 on d 7 compared with the control 8.22 +/- 1.24 on d 0 versus 7.95 +/- 1.54 on d 7. The Lactobacillus population showed a similar tendency while the other bacteria were unaffected. No gastrointestinal symptoms were detected during the prebiotic administration. Prebiotics in a milk formula increase fecal bifidobacteria early after amoxicillin treatment without inducing gastrointestinal symptoms.