Effect of in vivo growth conditions upon expression of surface protein antigens in<i>Enterococcus faecalis</i>

Western blotting of whole-cell preparations of Enterococcus faecalis showed the protein-antigen profiles to be markedly influenced by growth conditions. The E. faecalis-specific antigens of 40 and 37 kDa, which are prominent in endocarditis, were strongly expressed following growth in serum or brain heart infusion, but not after growth in a chemically defined medium. The expression of these antigens in vivo was demonstrated in cells grown as a biofilm on silastic discs in the peritoneum of rabbits. These in vivo culture conditions may be useful in studying the pathogenesis of E. faecalis infections and the effectiveness of antibiotic therapy.