New evidence for the non-infectivity of Treponema pallidum for mice.

We have recently shown that syphilitic rabbits are resistant to challenge with Listeria monocytogenes. This resistance was thought to reflect stimulation of cell-mediated immunity by active infection with Treponema pallidum. We now report data which show that the growth of Listeria was not suppressed in mice inoculated with T. pallidum. Re-inoculation with T, pallidum or with a large dose of an avirulent treponeme also failed to suppress the growth of Listeria. These results contrast with those obtained in rabbits and provide additional evidence that T. pallidum is not infective for the mouse.