Treponema pallidum in human chancre tissue: an electron microscopic survey

In biopsies obtained from syphilitic chancres of varying ages in 10 patients, a total of 766 ultrathin sections of Treponema pallidum were studied by electron microscopy. The course and number of axial filaments observed reveal that one bunch of 3-4 filaments without interruption entwine the whole cytoplasmic body. In 9.2% of the sections a trilaminar or a fragmentary trilaminar periplastic membrane was observed outside the cytoplasmic membrane and the axial filaments. The occurrence of the periplastic membrane decreased with advancing ages of the chancres. A protective function of the membrane is discussed. A peritreponemal fine reticular halo demonstrable in most fragments is supposed to be due to fixation induced shrinkage of treponemal hyaluronidase-influenced semifluid glycosaminoglycans. Peritreponemal reticular halos were also observed in collagen tissue. A destructive effect of the treponemes on collagen fibres could explain how the organisms penetrate through the collagen rich meninges into the central nervous system. A surface associated narrow border of electron dense amorphous substance, probably originating from the host organism, yields to tangentially cut treponemes a spiny caterpillar-like appearance.