The electron microscope images showed a specific interaction of anti-E. fecalis antibodies to E. fecalis in a monoculture preparation but not in a monoculture preparations of S. aureus or E. coli (Figs. 2 and 3). Furthermore, in a bacterial co-culture preparation containing the three bacterial strains (E. fecalis, S. aureus, and E. coli), anti-E. fecalis antibodies bound specifically only to the surface of few cocci (shown in arrows) but not to the other bacteria (Additional file 2).Fig. 2Co-culture of three bacterial strains: Staphylococcus aureus, Enterococcus fecalis, and Escherichia coli. Anti- Enterococcus fecalis antibodies incubated with the co-culture bound to some cocci but not to the other cocci or rods (white arrows). This interaction was visualized by electron microscopy by adding gold labled anti human IgG antibodies to the mediumFig. 3Co-culture of Enterococcus fecalis and Staphylococcus aureus incubated with anti-Enterococcus fecalis antibodies and visualized by electron microscopy. Please note the antibodies covering some cocci in the co-culture of two bacterial strains (white arrow)