A comparison of two probiotic strains of bifidobacteria in premature infants

Abstract

Objective: To determine the impact of 2 probiotic bifidobacteria on the fecal microbiota of premature infants fed either human milk or formula.

Study design: In the first of two phase 1 clinical trials, 12 premature infants receiving formula feedings were assigned randomly to receive either Bifidobacterium longum ssp infantis or Bifidobacterium animalis ssp lactis in increasing doses during a 5-week period. In the second, 9 premature infants receiving their mother's milk received each of the two bifidobacteria for 2 weeks separated by a 1-week washout period. Serial stool specimens from each infant were analyzed by terminal restriction fragment-length polymorphism and quantitative polymerase chain reaction for bacterial composition.

Results: Among the formula-fed infants, there was a greater increase in fecal bifidobacteria among infants receiving B infantis (Binf) than those receiving B lactis (Blac). This difference was most marked at a dose of 1.4 × 10(9) colony-forming units twice daily (P < .05). Bacterial diversity improved over dose/time in those infants receiving Binf. Among the human milk-fed infants, greater increases in fecal bifidobacteria and decreases in γ-Proteobacteria followed the administration of Binf than Blac. The B longum group (which includes Binf but not Blac) was the dominant bifidobacteria among the human milk-fed infants, regardless of the probiotic administered.

Conclusions: Binf was more effective at colonizing the fecal microbiota than Blac in both formula-fed and human milk-fed premature infants. The combination of human milk plus Binf resulted in the greatest fecal levels of bifidobacteria.

Trial registration: ClinicalTrials.gov NCT00810160.

Keywords: B infantis; B lactis; Bac-TRFLP; Bacilli-specific terminal restriction fragment-length polymorphism; Bif-TRFLP; Bifidobacteria-specific terminal restriction fragment-length polymorphism; Binf; Blac; Colony-forming units; F+Binf; F+Blac; Formula plus Binf; Formula plus Blac; H+Binf; H+Blac; HMO; Human milk oligosaccharides; Human milk plus Binf; Human milk plus Blac; NEC; Necrotizing enterocolitis; PBS; PCoA; Phosphate-buffered saline; Principal coordinate analysis; Quantitative polymerase chain reaction; Ribosomal RNA; TRFLP; Terminal restriction fragment-length polymorphism; UC Davis; University of California, Davis; WO; Washout; cfu; qPCR; rRNA.