Ultrastructural changes of Treponema pallidum isolated from secondary syphilitic skin lesions.

Treponema pallidum was isolated from various types of secondary syphilitic skin lesions. From moist genital papules and from condylomata lata several treponemes were isolated whereas few were isolated from dry papules of the trunk. One third of the observed treponemes were morphologically different from treponemes isolated from human chancres. Especially the nose-piece structures of the terminal parts of the treponemes were deviating. Some nose-pieces were coated by a fuzzily outlined electron dense substance, whereas others were degenerated or nearly separated from the cytoplasmic body. Other treponemes were missing their nose-piece as avirulent saprophytic treponemes. Recent studies have indicated that the nose-pieces are essential for the tissue attachment of treponemes and the treponemal virulence. The significance of the altered nose-piece structure observed is discussed.