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A new model for infective endocarditis of the mitral valve in rabbits
K Imataka1, Y Kitahara, S Naito
1Institute for Adult Diseases, Asahi Life Foundation, Tokyo, Japan.
Abstract:
To produce an experimental model of infective endocarditis without inserting catheters into the heart, we injected a bacterial suspension into rabbits in which mitral complex lesions had been induced by electrical stimulation of the cervical vagus. Typical infective vegetations grew on the surface of the mitral valves 1 week later. The formation of vegetations was related to the timing of the inoculation. Streptococcus viridans injected just after vagal stimulation produced vegetations in 10 of 17 animals (58.8%), but the same bacteria injected 14 days after vagal stimulation did so in only 2 of 11 animals (18.2%). The incidence of infective endocarditis was significantly higher after early inoculation compared with delayed inoculation (p < 0.01). The susceptibility to infection depended on the species of bacteria injected. Both S. viridans and Pseudomonas pseudoalkaligenes injected just after vagal stimulation produced vegetations in 10 of 17 (58.8%) and 6 of 13 (46.2%) animals, respectively, but Staphylococcus epidermidis injected just after vagal stimulation did not produce vegetations in any of the 10 animals. S. viridans injected into nine normal animals never produced vegetations. These findings indicate that infective endocarditis develops after intravenous injection of bacterial suspensions alone in rabbits with mitral complex lesions.
Insights
This study developed an experimental model for infective endocarditis in rabbits without cardiac catheterization. Early bacterial inoculation following induced mitral valve lesions significantly increased vegetation formation, demonstrating a new method for studying this heart infection.
Area of Science:
- Cardiovascular Research
- Infectious Diseases
- Experimental Pathology
Background:
- Infective endocarditis (IE) is a serious heart valve infection.
- Current experimental models often require invasive cardiac catheterization.
- A non-invasive method to induce IE is needed for research.
Purpose of the Study:
- To establish an experimental model of infective endocarditis in rabbits.
- To achieve this without the need for invasive cardiac catheterization.
- To investigate the influence of lesion timing and bacterial species on IE development.
Main Methods:
- Mitral valve complex lesions were induced in rabbits via electrical stimulation of the cervical vagus nerve.
- Bacterial suspensions (Streptococcus viridans, Pseudomonas pseudoalkaligenes, Staphylococcus epidermidis) were intravenously injected at varying times post-lesion induction.
- Vegetation formation on mitral valves was assessed 1 week after bacterial inoculation.
Main Results:
- Typical infective vegetations formed on mitral valves 1 week after inoculation in rabbits with induced lesions.
- Early bacterial inoculation (immediately after vagal stimulation) resulted in a significantly higher incidence of IE (58.8% with S. viridans) compared to delayed inoculation (18.2%).
- Bacterial species influenced IE development; S. viridans and P. pseudoalkaligenes induced vegetations, while S. epidermidis did not. Normal rabbits did not develop IE.
Conclusions:
- Infective endocarditis can be experimentally modeled in rabbits by intravenous bacterial injection alone, provided mitral valve lesions are present.
- The timing of bacterial inoculation relative to lesion induction is critical for successful IE development.
- This non-invasive method provides a valuable tool for studying the pathogenesis and treatment of infective endocarditis.