Adherence to and penetration through endothelial cells by oral treponemes

Oral spirochetes were co-incubated with monolayers of endothelial cells seeded into multiwell plates or onto filters mounted in plastic chambers. Attachment was assessed using an enzyme-linked immunosorbent assay and scanning electron microscopy. Invasiveness was determined by monitoring media beneath filters within chambers for spirochetes using darkfield microscopy. Transmission electron microscopy was used to estimate intercellular and intracellular passage of spirochetes through monolayers. All tested treponemes attached to monolayers in a dose- and time-dependent manner, except Treponema phagedenis. A few treponemes were observed within host cell cytoplasm. Unidentified spirochetes obtained from dental plaque were also invasive. Results indicate that oral spirochetes possess virulence-associated characteristics shared with pathogenic spirochetes. Further studies should examine the possibility that invasive spirochetes could disseminate from within affected gingiva.