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Updated: Oct 3, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
[Colonization of methicillin-resistant Staphylococcus aureus in the mouse intestinal tract]
1Pharmaceutical Development Research Laboratory, Tanabe Seiyaku Co. Ltd., Saitama, Japan.
Abstract:
Mice were infected intravenously with rifampicin-resistant strains selected out of methicillin-resistant Staphylococcus aureus (MRSA) strains and examined for colonization of these organisms in the intestinal tract. Three of four MRSA strains colonized in the cecum of more than 80% of the mice inoculated with approximately 10(7) cfu/mouse. The extent of colonization paralleled the lethal activity, which was inversely related to the methicillin resistivity: moderately resistant strains (MIC: 12.5 micrograms/ml) tended to show more potent pathogenicity than highly resistant ones (MIC: > or = 100 micrograms/ml). Distribution and localization of the organisms in the mice infected with a moderately resistant and highly pathogenic strain S. aureus 1-6 RFPr were studied by autobacteriography. Within one day after infection, colonies of the infecting organisms were distributed all over the body and were especially dense in the liver and spleen. On day 3, the organisms in the liver and spleen disappeared, while many colonies were observed in the intestinal tract. The organisms in the intestinal tract remained for 14 days after infection. In the autobacteriograms of the mice infected with Escherichia coli KC-14 RFPr, such persistency in the intestinal tract was not demonstrated. When viable cell counts of the cecum contents of the mice infected with S. aureus 1-6 RFPr (approximately 10(7) cfu/mouse) were made, the organisms were detected as early as 3 hr after infection and then gradually increased to more than 4 logs cfu/g on day 7. With E. coli KC-14 RFPr, a few colonies were detected transiently in the cecum contents of mice at an early stage infection, but the organisms did not increase and disappeared by day 3 after infection. These results show that the colonization in the mouse intestinal tract is a specific phenomenon to the S. aureus species including MRSA strains.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) strains effectively colonize the mouse intestinal tract, with colonization correlating to pathogenicity. This intestinal colonization is specific to S. aureus, including MRSA strains.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Context:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat due to its antibiotic resistance.
- Understanding the colonization dynamics of MRSA is crucial for developing effective treatment and prevention strategies.
- Intestinal colonization by bacteria can serve as a reservoir for systemic infections.
Purpose:
- To investigate the intestinal colonization potential of rifampicin-resistant MRSA strains in a mouse model.
- To determine the relationship between MRSA methicillin resistance, pathogenicity, and colonization extent.
- To elucidate the distribution and persistence of S. aureus in vivo using autobacteriography.
Summary:
- Intravenous inoculation of mice with rifampicin-resistant MRSA strains resulted in significant cecal colonization in over 80% of animals.
- Colonization extent was inversely proportional to methicillin resistance, with moderately resistant strains exhibiting higher pathogenicity.
- Autobacteriography revealed initial systemic distribution followed by specific and persistent intestinal colonization by S. aureus, unlike Escherichia coli.
Impact:
- These findings highlight the specific ability of S. aureus, including MRSA, to colonize the mouse intestinal tract.
- The study provides insights into the complex host-pathogen interactions governing MRSA persistence.
- Results contribute to understanding potential reservoirs for MRSA infections and inform future research directions.
