Effects of Bifidobacterium lactis Bb12 supplementation on intestinal microbiota of preterm infants: a double-blind, placebo-controlled, randomized study

Abstract

The gastrointestinal microbiota of preterm infants in a neonatal intensive care unit differs from that of term infants. In particular, the colonization of preterm infants by bifidobacteria is delayed. A double-blind, placebo-controlled, randomized clinical study was performed on 69 preterm infants to investigate the role of Bifidobacterium lactis Bb12 supplementation in modifying the gut microbiota. Both culture-dependent and culture-independent approaches were used to study the gut microbiota. Bifidobacterial numbers, determined by fluorescence in situ hybridization, were significantly higher in the probiotic than in the placebo group (log(10) values per g of fecal wet weight: probiotic, 8.18 + 0.54 [standard error of the mean]; placebo, 4.82 + 0.51; P < 0.001). A similar trend for bifidobacterial numbers was also obtained with the culture-dependent method. The infants supplemented with Bb12 also had lower viable counts of Enterobacteriaceae (log(10) values of CFU per g of fecal wet weight: probiotic, 7.80 + 0.34; placebo, 9.03 + 0.35; P = 0.015) and Clostridium spp. (probiotic, 4.89 + 0.30; placebo, 5.99 + 0.32; P = 0.014) than the infants in the placebo group. Supplementation of B. lactis Bb12 did not reduce the colonization by antibiotic-resistant organisms in the study population. However, the probiotic supplementation increased the cell counts of bifidobacteria and reduced the cell counts of enterobacteria and clostridia.

FIG. 1.

Effect of probiotic and placebo supplementation on CFU of bacterial groups tested (probiotic, n = 26; placebo, n = 32). The empty and filled bars represent the placebo and the probiotic groups, respectively. The error bars represent the standard errors of the means. P values are as follows: 0.005, total bacteria; 0.02, total aerobic bacteria; 0.008, total anaerobic bacteria; 0.002, bifidobacteria; 0.015, Enterobacteriaceae; 0.014, clostridia. *, P < 0.05; **, P < 0.01.

FIG. 2.

(A) Weekly changes in the numbers of bifidobacteria targeted with Bif164 during probiotic and placebo supplementation: week 1, probiotic n = 18, placebo n = 21; week 2, probiotic n = 24, placebo n = 27; week 3, probiotic n = 18, placebo n = 19. Open and closed circles refer to the probiotic and placebo groups, respectively. The error bars represent the standard errors of the means. The P value is <0.001 in all cases. (B) Effect of probiotic supplementation and antibiotic therapy on bifidobacteria targeted by Bif164. The effect is shown for all infants (probiotic n = 32, placebo n = 33), antibiotic-treated infants (probiotic n = 23, placebo n = 20), and infants without antibiotic treatment (probiotic n = 10, placebo n = 12). The empty and filled bars represent the placebo and the probiotic groups, respectively. The error bars represent the standard errors of the means. P values are as follows: <0.001, all infants; 0.006, infants with antibiotic treatment; <0.001, infants without antibiotic treatment. **, P < 0.01; ***, P < 0.001.

FIG. 3.

FISH signals obtained upon hybridization of the fecal sample of an infant (subject number 35) with the Clit135 probe with (A) and without (B) lysozyme treatment.