PORPHYROMONAS-GINGIVALIS INVADES HUMAN POCKET EPITHELIUM IN-VITRO

The present study examined the adhesive and invasive potential of Porp hyromonas gingivalis interacting with human pocket epithelium in vitro . Pocket epithelial tissue, obtained during periodontal surgery of pat ients with advanced periodontal disease, generated a stratified epithe lium in culture. P. gingivalis strains W50 and FDC 381 (laboratory str ains), OMGS 712, 1439, 1738, 1739 and 1743 (clinical isolates) as well as Escherichia coli strain HB1O1 (non-adhering control) were tested w ith respect to epithelial adhesion and invasion. Adhesion was quantita ted by scintillation spectrometry after incubation of radiolabeled bac teria with epithelial cells. The invasive ability of I gingivalis was measured by means of an antibiotic protection assay. The epithelial mu ltilayers were infected with the test and control strains and subseque ntly incubated with an antibiotic mixture (metronidazole 0.1 mg/ml and gentamicin 0.5 mg/ml). The number of internalized bacteria surviving the antibiotic treatment was assessed after plating lyzed epithelial c ells on culture media. All tested Il gingivalis strains adhered to and entered pocket epithelial cells. However, considerable variation in t heir adhesive and invasive potential was observed. E. coli strain HB10 1 did not adhere or invade. Transmission electron microscopy revealed that internalization of R gingivalis was preceded by formation of micr ovilli and coated pits on the epithelial cell surfaces. Intracellular bacteria were most frequently surrounded by endosomal membranes; howev er, bacteria devoid of such membranes were also seen. Release of outer membrane vesicles (blebs) by internalized II gingivalis was observed. These results support and extend previous work from this laboratory w hich demonstrated invasion of a human oral epithelial cell-line (KB) b y II gingivalis.