While previous studies have shown that presence of bacteria in systemic circulation can cause infective endocarditis, there is no information on the specific amount of bacteria necessary to cause this condition. The purpose of this study was to establish the minimum level of circulating bacteria that will cause colonization of damaged heart valves in rats. Fifty-two Sprague-Dawley rats were anesthetized and their heart valves were damaged using an established protocol. A clinical isolate of Enterococcus faecalis was transformed with a plasmid bearing the luxF and Chloramphenicol cassettes to label the bacteria with the light-emitting protein. After four weeks, the rats were re-anesthetized and intravenously injected with various concentrations of the labeled E. faecalis ranging from 1 x 102 to 1 x 108 cells in a 100 μl volume. The animals were sacrificed one week after infection and the hearts were excised and incubated overnight in brain heart infusion containing chloramphenicol. The presence or absence of luminescent bacteria was examined under a low light imager and recorded. All animals injected with 1 x 108 E. faecalis cells consistently demonstrated colonization of their heart valves. Variable incidence of colonization was also observed in animals injected with 1 x 103 to 1 x 107 cells. None of the rats injected with 5 x 102 or 1 x 102 bacterial cells demonstrated colonization of their heart valves. This study has established for the first time the lowest level of bacteria, which can cause colonization of damaged heart valves in rats.


Graduate School

First Advisor

Mahmoud Torabinejad

Second Advisor

Alan Escher

Third Advisor

Shahrokh Shabahang

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Enterococcus Faecalis; Heart Valve; Heart Valve Diseases; Endocarditis, Bacterial



Page Count

viii; 33

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives