Treponema pallidum is a
spirochaete bacterium with subspecies that cause
treponemal diseases such as
syphilis,
bejel,
pinta, and
yaws. The treponemes have a cytoplasmic and an outer membrane. Using
light microscopy, treponemes are only visible using
dark field illumination.
Subspecies
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This section requires expansion. (December 2010) |
At least four
subspecies are known:
- Treponema pallidum pallidum, which causes syphilis
- T. p. endemicum, which causes bejel or endemic syphilis
- T. p. carateum, which causes pinta
- T. p. pertenue, which causes yaws
Some variation occurs as to which are considered subspecies, and
which are species. The cause of pinta is sometimes described as
Treponema carateum, rather than a subspecies of
T. pallidum, even when the subspecies convention is used for the other agents.
[1]
Laboratory identification
This bacterium can be detected with special stains, such as the
Dieterle stain.
T. pallidum is also detected by
serology, including
nontreponemal VDRL,
rapid plasma reagin, and treponemal antibody tests (
FTA-ABS),
T. pallidum immobilization reaction, and
syphilis TPHA test).
[2]
Clinical significance
T. p. 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. p. pallidum
allows it to move in a corkscrew motion through a viscous medium such
as mucus. It gains access to the 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. p. pallidum (syphilis); however, their transmission is not venereal in nature and the course of each disease is significantly different.
Genome
In the 17 July 1998 issue of the journal
Science, a group of biologists reported how they sequenced the
genome of
T. pallidum.
[3]
The recent sequencing of the genomes of several spirochetes permits a
thorough analysis of the similarities and differences within this
bacterial phylum.
T. p. pallidum has one of the smallest
bacterial genomes at 1.14 million base pairs, and has limited metabolic
capabilities, reflecting its adaptation through genome reduction to the
rich environment of mammalian tissue. The shape of
T. pallidum is flat and wavy, unlike the other spirochetes, which are helical.
[4]
Vaccine
No
vaccine for syphilis is available as of 2015. The outer membrane of
T. pallidum has too few surface proteins for an
antibody
to be effective. Efforts to develop a safe and effective syphilis
vaccine have been hindered by uncertainty about the relative importance
of humoral and cellular mechanisms to protective immunity,
[citation needed] and because
T. pallidum outer membrane proteins have not been unambiguously identified.
[5]
References
- Antal GM, Lukehart SA, Meheus AZ (January 2002). "The endemic treponematoses". Microbes Infect. 4 (1): 83–94. doi:10.1016/S1286-4579(01)01513-1. PMID 11825779.
- Fisher, Bruce; Harvey, Richard P.; Champe, Pamela C. Lippincott's Illustrated Reviews: Microbiology (Lippincott's Illustrated Reviews Series). Hagerstown, MD: Lippincott Williams & Wilkins. ISBN 0-7817-8215-5.
- Fraser CM, Norris SJ, Weinstock GM et al. (July 1998). "Complete genome sequence of Treponema pallidum, the syphilis spirochete". Science 281 (5375): 375–88. doi:10.1126/science.281.5375.375. PMID 9665876.
- Clark, D.P., Dunlap, P.V, Madigan, J.T., Martinko, J.M. Brock Biology of Microorganism. San Francisco: Pearson. 2009. 79 p.
- Tomson FL, Conley PG, Norgard MV, Hagman KE (September 2007). "Assessment of cell-surface exposure and vaccinogenic potentials of Treponema pallidum candidate outer membrane proteins". Microbes Infect. 9 (11): 1267–75. doi:10.1016/j.micinf.2007.05.018. PMC 2112743. PMID 17890130.
Further reading
External links
- "Syphilis- CDC Fact Sheet." Centers for Disease Control and Prevention. May. 2004. Centers for Disease Control and Prevention. 7 February 2006
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