Comparative behavior of virulent strains of Treponema pallidum and Treponema pertenue in gradient cultures of various mammalian cells.

Two strains of virulent Treponema pallidum and two of virulent T. pertenue were investigated for their ability to attach to and survive in gradient cultures of five different mammalian cells under aerobic conditions. The strains of T. pallidum studied were the high-rabbit-passage Nichols and the low-rabbit-passage KKJ. The former was known to readily attach to cottontail rabbit epithelial cells (Sf1Ep) and to survive in the virulent state for up to 21 days. We therefore compared attachment of the other virulent treponemes with that of T. pallidum (Nichols). The KKJ strain of T. pallidum behaved in a fashion similar to T. pallidum (Nichols) in all of the cultures. Both strains exhibited preferential attachment to cells of Sf1Ep and those derived from the ear of a nude athymic (nu/nu) mouse. In these cultures, we observed a consistent three- to fivefold increase in attached treponemes up to 12 days after initial inoculation. The strains of T. pertenue were the human-derived Gauthier and cynocephalus-derived FB. These two strains of T. pertenue also attached to cells of all five types of cultures, but in smaller numbers than were seen with T. pallidum and equally to all of the cultures. Neither preferential attachment to Sf1Ep and nude mouse ear cells nor increased attachment with time was seen.