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Published on: March 10, 2026
Growth in cecal mucus facilitates colonization of the mouse intestinal tract by methicillin-resistant Staphylococcus
Delores M Gries1, Nicole J Pultz, Curtis J Donskey
1Department of Pediatrics, Madigan Army Medical Center, Tacoma, Washington, USA.
Abstract:
Intestinal colonization by methicillin-resistant Staphylococcus aureus (MRSA) is common in some groups of hospitalized patients and has been associated with an increased risk of staphylococcal infection. We tested the hypothesis that growth of MRSA in the colonic mucus layer is required for establishment of intestinal colonization. Mice treated with oral streptomycin before oral administration of MRSA developed persistent intestinal colonization, and the cecal mucus layer contained high concentrations of MRSA. MRSA strains grew rapidly when inoculated into cecal mucus in vitro but were unable to replicate under anaerobic conditions in cecal contents of saline- or streptomycin-treated mice. Oral vancomycin treatment reduced the density of 1 MRSA strain in stool but had no effect on a second strain. These results suggest that the cecal mucus layer provides an important niche that facilitates intestinal colonization by MRSA. Oral nonabsorbed antibiotics may be ineffective in eradicating some MRSA strains from the intestinal tract.
Insights
The colonic mucus layer is crucial for intestinal colonization by methicillin-resistant Staphylococcus aureus (MRSA). This finding suggests some oral antibiotics may not effectively eradicate MRSA from the gut.
Area of Science:
- Microbiology
- Gastroenterology
- Infectious Diseases
Background:
- Intestinal colonization by methicillin-resistant Staphylococcus aureus (MRSA) is prevalent in hospitalized patients.
- MRSA colonization is linked to a higher risk of staphylococcal infections.
Purpose of the Study:
- To investigate the role of MRSA growth within the colonic mucus layer in establishing intestinal colonization.
- To determine if the mucus layer is a necessary niche for MRSA gut persistence.
Main Methods:
- Mice were treated with oral streptomycin followed by oral MRSA administration.
- MRSA colonization and concentration in the cecal mucus layer were assessed.
- In vitro growth of MRSA in cecal mucus and cecal contents under anaerobic conditions was evaluated.
- Effectiveness of oral vancomycin on MRSA strains was tested.
Main Results:
- Mice treated with streptomycin showed persistent intestinal MRSA colonization with high MRSA concentrations in the cecal mucus.
- MRSA demonstrated rapid growth in cecal mucus in vitro but not in anaerobic cecal contents.
- Oral vancomycin reduced one MRSA strain but not another, indicating variable efficacy.
Conclusions:
- The cecal mucus layer serves as a critical niche facilitating intestinal colonization by MRSA.
- Oral non-absorbed antibiotics may not be effective for eradicating all MRSA strains from the intestinal tract.
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