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Aggregation and binding substances enhance pathogenicity in rabbit models of Enterococcus faecalis endocarditis
P M Schlievert1, P J Gahr, A P Assimacopoulos
1Department of Microbiology, University of Minnesota Medical School, Minneapolis 55455-0312, USA. pats@lenti.med.umn.edu
Infection and Immunity
|January 10, 1998
Summary
Enterococcal aggregation substance (AS) and binding substance (EBS) are crucial for Enterococcus faecalis infections. Deletion of AS and EBS significantly reduces virulence, impacting cardiac infections and endocarditis development in rabbit models.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Enterococcus faecalis is a significant cause of hospital-acquired infections.
- Enterococcal aggregation substance (AS) and binding substance (EBS) are cell wall components implicated in bacterial virulence.
- The specific roles of AS and EBS in Enterococcus faecalis pathogenesis, particularly in cardiac infections and endocarditis, require further elucidation.
Purpose of the Study:
- To investigate the role of enterococcal aggregation substance (AS) and enterococcal binding substance (EBS) in rabbit models of Enterococcus faecalis cardiac infections and endocarditis.
- To determine the impact of AS and EBS on bacterial virulence, host immune response, and disease severity.
Main Methods:
- Utilized rabbit models, including intraventricular injection and transaortic catheterization, to simulate Enterococcus faecalis cardiac infections and endocarditis.
- Employed genetically modified Enterococcus faecalis strains lacking AS and/or EBS (AS- EBS-, AS- EBS+, AS+ EBS-, AS+ EBS+).
- Assessed clinical signs of illness, mortality, pericardial inflammation, vegetation formation, splenomegaly, lung congestion, and host immune responses (lymphocyte proliferation, cytokine production).
Main Results:
- Absence of both AS and EBS (AS- EBS-) rendered Enterococcus faecalis non-pathogenic in cardiac infection and endocarditis models.
- Strains lacking only AS (AS+ EBS-) or EBS (AS- EBS+) exhibited reduced virulence compared to wild-type (AS+ EBS+).
- Enterococcus faecalis strains expressing both AS and EBS (AS+ EBS+) demonstrated the highest virulence, causing significant cardiac inflammation, high mortality, and severe endocarditis with lung congestion.
Conclusions:
- Enterococcal aggregation substance (AS) and binding substance (EBS) are critical virulence factors for Enterococcus faecalis.
- These cell wall components play a significant role in the pathogenesis of cardiac infections and endocarditis.
- The combined presence of AS and EBS contributes to lethal infections, potentially through superantigen activity and immune modulation.