Aggregation and Binding Substances Enhance Pathogenicity in a Rabbit Model of Enterococcus faecalis Endocarditis

Abstract

We investigated the importance of Aggregation Substance (AS) and Binding Substance (BS) in a rabbit model of Enterococcus faecalis endocarditis. Aggregation substance (AS), a pheromone inducible, surface protein of E. faecalis, promotes mating aggregate formation during bacterial conjugation and is thought to be a virulence factor in enterococcal infections by promoting binding to a variety of eukaryotic cell surfaces². AS is not produced constitutively, but may be induced by eukaryotic factors in serum. AS contains the amino acid motifs Arg-Gly-Asp-Ser and Arg-Gly-Asp-Val, found in fibronectin and other proteins which mediate adhesion to eukaryotic cell surfaces². Binding Substance (BS) is the site recognized by AS and is also necessary for mating aggregate formation. Lipotechoic acid (LTA) inhibits aggregate formation and may function as enterococcal BS². Because of the increasing frequency with which enterococci are identified as nosocomial pathogens and because of the increasing incidence of vancomycin and other antibiotic resistance among these organisms, greater attention is focusing on the pathogenesis of enterococcal infections. AS and BS are thought to play an important role in enterococcal infections.

This work was supported by grant HL51987 from the National Heart, Lung, and Blood Institute. AP Assimacopoulos was supported by National Research Service Award #2-T32-HD-07381.