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| Fig. 28.1 Biopsy of secondary syphilis demonstrating numerous spirochetes in the epidermis (Warthin-Starry stain, 31000). |
T. pallidum is a delicate spiral bacterium that measures 6 to 20 mm in length and 0.10 to 0.18 mm in width (Fig. 28-1). Because of the narrow width, it is not visible by normal light microscopy and must be visualized by darkfield microscopy, by silver stains (i.e., Warthin-Starry or modified Steiner stains), or by immunoperoxidase stains (
Treponema). The spiral coils are regularly spaced at a distance of about 1 mm. The typical spirochete has 6 to 14 coils. The organism reproduces by transverse fission.
