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.