VIRULENCE FACTORS OF STAPHYLOCOCCUS-AUREUS IN THE PATHOGENESIS OF ENDOCARDITIS - A COMPARATIVE-STUDY OF CLINICAL ISOLATES

It is now generally accepted that adherence of microorganisms to vario us components of cardiac valve surfaces or vegetation lodging on the h eart valves is an important early event in the pathogenesis of infecti ve endocarditis. 120 clinical isolates of S. aureus obtained from pati ents with endocarditis and wound infections and from nasopharyngeal ca rriers were quantitatively analysed in vitro for their ability to bind to fibronectin and to produce protein A and alpha-toxin. Both cell-bo und and extracellular protein A were measured and alpha-toxin was dete rmined as antigen and as haemolytic activity. The highest fibronectin binding ability was found in carrier strains while no significant diff erences between strains were observed regarding the production of prot ein A. Strains isolated from patients with endocarditis produced signi ficantly lower amounts of alpha-toxin than did strains from the other two groups. An inverse relationship between the production of protein A and of alpha-toxin was noticed in the material. Animal passage of fi ve strains in an experimental endocarditis model showed a good reprodu cibility of the test systems and one strain was upregulated in its fib ronectin binding ability and in alpha-toxin production. These in vitro results indicate that the fibronectin binding ability is not the deci sive adherence factor and question the role of alpha-toxin as a virule nce factor in endocarditis.