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Updated: Sep 2, 2026
Preparation and Maintenance of Bioexclusion IsoPositive Cage Experiment for Human Fecal Transplantation into Germ-Free Mice
Published on: February 28, 2025
ASSOCIATION OF GERMFREE MICE WITH BACTERIA ISOLATED FROM NORMAL MICE
Abstract:
Germfree mice were given food contaminated with pure cultures of various bacterial species isolated from ordinary healthy mice. The cultures were given singly, or in association, or consecutively at weekly intervals. Whatever the technique of administration, the lactobacilli and anaerobic streptococci immediately established themselves throughout the gastrointestinal tract, and became closely associated with the walls of the organs. In contrast, the organisms of the bacteroides group were found in large numbers only in the large intestine. Within a week after exposure, the populations of these three bacterial species reached levels similar to those found in ordinary mice. They remained at these characteristic levels throughout the period of observation (several months). Their presence resulted in a progressive decrease in the size of the cecum which eventually became normal in gross appearance. Coliform bacilli multiplied extensively and persisted at high levels in all parts of the gastrointestinal tract of germfree mice, even after these had become colonized with lactobacilli, anaerobic streptococci and bacteroides. However, the coliform population fell precipitously within a few days after the animals were fed the intestinal contents of healthy pathogen-free mice.
Insights
Introducing specific gut bacteria to germfree mice rapidly established normal microbial populations and cecal size. However, coliform bacilli persisted until colonization with healthy gut contents occurred.
Area of Science:
- Microbiology
- Gastroenterology
- Animal Models
Background:
- Germfree animals lack a native gut microbiome, exhibiting distinct physiological characteristics.
- Understanding microbial colonization is crucial for gut health and disease research.
Purpose of the Study:
- To investigate the colonization patterns and effects of specific bacterial species in germfree mice.
- To determine the impact of microbial colonization on cecal morphology and coliform populations.
Main Methods:
- Germfree mice were orally administered pure cultures of lactobacilli, anaerobic streptococci, and bacteroides species.
- Bacterial colonization was monitored over several months using various administration techniques.
- Cecal size and coliform populations were assessed in colonized and control mice.
Main Results:
- Lactobacilli and anaerobic streptococci colonized the entire gastrointestinal tract, while bacteroides primarily inhabited the large intestine.
- Colonization rapidly restored cecal size to normal in germfree mice.
- Coliform bacilli initially proliferated but were suppressed by the introduction of healthy gut microbiota.
Conclusions:
- Specific gut bacteria can rapidly establish stable populations in germfree mice, influencing host physiology.
- The presence of a balanced microbiota, including healthy gut contents, is essential for controlling opportunistic pathogens like coliforms.
