Related Experiment Video
Updated: May 8, 2026

Probiotic Studies in Neonatal Mice Using Gavage
Published on: January 27, 2019
A comparison of two probiotic strains of bifidobacteria in premature infants
Mark A Underwood1, Karen M Kalanetra, Nicholas A Bokulich
1Department of Pediatrics, University of California, Davis, Sacramento, CA; Foods for Health Institute, University of California, Davis, Davis, CA.
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.
Related Concept Videos
Development of Human Microbiota
Probiotics
Development of the Oral Microbiota
Introduction to the Human Microbiota
Microbiota of the Stomach and Small Intestine
Bacterial Flora of the Large Intestine
The normal gut flora of the colon plays a critical role in generating essential vitamins such as vitamins K, B5, and B7.
