| 1. NCBI Taxonomy ID: |
| 160 |
| 2. Disease: |
| Syphilis |
| 3. Introduction |
| T. pallidum pallidum is a motile spirochaete that is generally acquired by close sexual contact, entering the host via breaches in squamous or columnar epithelium. The organism can also be transmitted to a fetus by transplacental passage during the later stages of pregnancy, giving rise to congenital syphilis. The helical structure of T. pallidum pallidum allows it to move in a corkscrew motion through a viscous medium such as mucus. It gains access to host's blood and lymph systems through tissue and mucous membranes. The subspecies causing yaws, pinta, and bejel are morphologically and serologically indistinguishable from T. pallidum pallidum (syphilis); however, their transmission is not venereal in nature and the course of each disease is significantly different (Wiki: T. pallidum). |
| 4. Microbial Pathogenesis |
|
T. pallidum (in the case of syphilis) generally first forms a chancre at the site of infection and the spirochetes are infectious. The bacteria then penetrate mucosal membranes, and invade the bloodstream as well as other tissues. The bacteria cause latent syphilis which can progress into tertiary syphilis by the bacteria causing inflammatory disease and thus creating problems in infected (Salyers and Whitt., 2002). |
| 5. Host Ranges and Animal Models |
| T. pallidum is an obligate internal parasite, meaning that it requires a mammalian host for survival. In the absence of mammalian cells, T. pallidum will be killed by the absence of nutrients, exposure to oxygen and heat. T. pallidum causes the human disease syphilis. Since T. pallidum cannot be grown in culture, animal models are needed to study syphilis. Although mice and monkeys can be used, rabbits are the animal model almost exclusively studied in the lab. Rabbits are used because unlike monkeys they are inexpensive and unlike mice, rabbits develop the signs and symptoms of human primary and secondary syphilis (MicrobeWiki: T. pallidum). |
| 6. Host Protective Immunity |
| The primary clearance mechanism responsible for removal of T. pallidum from syphilitic chancres is believed to be antibody‐mediated treponemal opsonization and subsequent phagocytosis and killing by macrophages (Cameron et al., 1998). |
