A PLASMID-ENCODED SURFACE PROTEIN ON ENTEROCOCCUS-FAECALIS AUGMENTS ITS INTERNALIZATION BY CULTURED INTESTINAL EPITHELIAL-CELLS

Aggregation substance, a plasmid-encoded Enterococcus faecalis surface protein, plays a role in mediating the formation of mating aggregates , resulting in plasmid transfer. The role of aggregation substance in the internalization of E. faecalis by cultured intestinal epithelial c ells, namely HT-29 cells, was analyzed. It was associated with a signi ficant increase in endocytosis of E. faecalis by HT-29 cells: Numbers of internalized enterococci were fewer than of an invasive strain of L isteria monocytogenes, similar to Salmonella typhimurium and another L . monocytogenes strain, and greater than relatively noninvasive strain s of E. faecalis, Proteus mirabilis, and Escherichia coli. Electron mi croscopy confirmed aggregation substance on the surface of strains int eracting with the enterocyte microvillous surface, and intracellular e nterococci were localized within membrane-bound vacuoles in the entero cyte cytoplasm. Thus, aggregation substance may facilitate E. faecalis internalization by host epithelial cells.