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Published on: February 19, 2013
Colonization resistance of the digestive tract in conventional and antibiotic-treated mice
Abstract:
The effect of oral administration of antibiotics on the intestinal flora of conventional mice and their resistance to colonization by orally introduced Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa was studied. Colonization resistance (CR) was expressed as the log of the oral bacterial dose followed by a persistent take in 50% of the contaminated animals. The intestinal flora was virtually eliminated by the antibiotics and this elimination was accompanied by a precipitous fall of CR. CR gradually returned to normal values during the period of repopulation of the intestinal tract by the organisms surviving the treatment. Antibiotic treatment resulted in the disappearance of Enterobacteriaceae, enterococci, staphylococci and yeasts and, under appropriate housing conditions, the animals remained free of these organisms indefinitely. Germ-free mice contaminated with the intestinal flora of an antibiotic-treated animal and their offspring housed in a germ-free isolator showed high values of CR. Their intestinal flora consisted of anaerobic bacteria only. Apparently, these anaerobes are responsible for CR in these and in conventional mice.
Insights
Oral antibiotics disrupt gut flora and reduce colonization resistance (CR) in mice. Anaerobic bacteria, however, restore CR, highlighting their crucial role in maintaining intestinal health.
Area of Science:
- Microbiology
- Gastroenterology
- Immunology
Background:
- The intestinal microbiota plays a critical role in host health, including defense against pathogens.
- Antibiotic use can profoundly alter the gut microbiome composition and function.
- Colonization resistance (CR) is a key protective mechanism of the gut microbiota against invading microorganisms.
Purpose of the Study:
- To investigate the impact of oral antibiotics on the intestinal flora of conventional mice.
- To assess the effect of antibiotic-induced dysbiosis on colonization resistance against specific pathogens.
- To identify the microbial components responsible for maintaining colonization resistance.
Main Methods:
- Conventional mice were administered oral antibiotics to disrupt their intestinal flora.
- Colonization resistance (CR) was quantified by challenging mice with oral doses of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa.
- Germ-free mice were colonized with the intestinal flora of antibiotic-treated mice to evaluate the role of specific microbial communities.
Main Results:
- Antibiotic treatment virtually eliminated the intestinal flora and significantly reduced CR.
- CR gradually recovered as the intestinal tract repopulated with surviving microorganisms.
- Antibiotic-treated mice, under specific housing, remained free of Enterobacteriaceae, enterococci, staphylococci, and yeasts.
- Germ-free mice colonized with flora from antibiotic-treated animals exhibited high CR, with intestinal flora composed solely of anaerobic bacteria.
Conclusions:
- Oral antibiotics severely impair colonization resistance by disrupting the intestinal microbiota.
- Anaerobic bacteria are identified as the primary mediators of colonization resistance in both conventional and antibiotic-treated mice.
- Restoration of anaerobic gut bacteria is crucial for re-establishing defense against enteric pathogens.
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