Accelerated lesion development in experimental syphilis.

In experimental syphilis, lesion development changes when different numbers of treponemes are injected. Lesions at sites inoculated with lower concentrations frequently exhibit delayed incubation periods, less tissue degradation, and more rapid healing. In this report I describe an unusual finding, namely, that accelerated rather than delayed incubation period occurred after intradermal inoculation of different dosages of Treponema pallidum. When rabbits were injected with only one inoculum containing 10(6), 10(5), 10(4), or 10(3) treponemes per rabbit, the corresponding incubation periods were 4.2, 7.5, 11.0 and 15.3 days, respectively. When each rabbit was injected with all four inocula on the back, the incubation periods were shortened to 3.9, 6.0, 7.0 and 8.9 days, respectively. More pronounced differences were observed with more divergent ranges of treponemal inocula. I discuss these findings in terms of the histopathology of syphilitic lesions.