Treponema Pallidum
Etiology/Bacteriology
Taxonomy
Domain: Bacteria
Phylum: Spirochaetes
Order: Spirochaetales
Family: Spirochaetaceae
Genus: Treponema
Species: T. pallidum
Description
Treponema pallidum is a motile, spirochaete bacteria that has subspecies that can cause treponemal diseases such as syphilis, pinta, bejel, and yaws. Syphilis is caused by the subspecies T. pallidum pallidum, pinta is caused by T. pallidum carateum, bejel is caused by T. pallidum endemicum, and yaws is caused by T. pallidum pertenue. The four subspecies of T. pallidum are morphologically and serologically identical, however their course of action and transmission differs from one another. Even though T. pallidum can cause all four of these diseases, the most serious and concerning of these is syphilis. T. pallidum is a small bacterium that cannot be seen via Gram stain because it is too thin. However, it can be viewed by using dyes like Dieterle Stain (1). It can also be detected by serology tests. Syphilis is transmitted venereally while the other T. pallidum diseases are not. There were reported cases of syphilis-like symptoms dating back to the 14th and 15th centuries with a possible origin being Europe. The symptoms appear in 3 stages and include sores, rashes, latent periods, nervous system damage and eventually death. Because of the seriousness involved with syphilis, most of the research is on this disease and therefore the remainder of this page is based upon it as well.
History
There are reported cases of syphilis-like symptoms that date back to the 13th-14th century in Europe(2). However, the first treponemal diseases are theorized to have originated in East Africa. The disease is said to have migrated from Africa into Asia, Europe, and North America possibly due to the slave trade(3). Another theory is that the disease started in Europe and from there spread to Africa, Asia, and North America. It is said that a European explorer named Vasco da Gama carried the disease to Calcutta in 1498 and from there it spread to Africa and then Asia by 1520(4). There is also a possibility that syphilis cases were reported as a mistake because before 1500 there was not a distinction between syphilis and leprosy(5). However, it is important to remember that these are all just theories and there is no definitive answer for where or when Syphilis emerged. It wasn't until 1905 that the bacteria that causes syphilis was discovered by German researches. From 1932 until 1972 the Tuskegee study was conducted in order to watch the progression of the disease. By 1943 Penicillin was widely used to combat this disease. However, in 1947 there was a large outbreak of syphilis cases in the U.S. 600,000 cases were reported that year making this outbreak the second largest syphilis epidemic recorded with the first being in Europe in the 1400's(8)(9).
Pathogenesis
Transmission
Syphilis is transmitted venereally via direct contact with sores(6). This can include anal, vaginal, and oral contact with an infected person. Syphilis can also be transmitted congenitally from mother to child through the placenta during pregnancy. Syphilis cannot be transferred by toilet seats, swimming pools, door knobs, eating utensils, sharing clothes, etc. because it is oxygen sensitive(7)(10).
Colonization
Syphilis can only naturally grow in human hosts(12). It can attach to a wide variety of cells such as epithelial, endothelial, and fibroblastlike cells. Syphilis enters the body through a breach in the skin or mucous membranes. It can move to the blood stream, spinal fluid, and to other internal organs very rapidly via its internal flagella. This can be seen in the secondary stage of infection when the body is covered in a rash as a result of infection with the disease(10).
Incubation and Infectious dose
As seen in guinea pigs, the infectious dose of Treponema pallidum is anywhere between about 10 to 1,000,000 organisms. However the mean number seems to be about 100 organisms to cause infection(11). The incubation period is relatively long.
Virulence Factors
Syphilis has a few very important virulence factors. One factor in particular it its corkscrew shape. It's shape gives it the ability to move through gel-like material which is necessary when moving through the genital and oral cavities. This allows syphilis to enter in areas many other disease causing bacteria could not(10).
Clinical features
Incidence and Mortality
Symptoms
Diagnosis
Treatment
Mercury, Arsenic, Penicillin, magic bullet
Prevention
Host Immune Response
References
(1)http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Treponema_pallidum.html
(2)http://www.news-medical.net/health/Syphilis-History.aspx
(3)http://cid.oxfordjournals.org/content/40/10/1454.full
(4)http://www.infoplease.com/cig/dangerous-diseases-epidemics/syphilis-sexual-scourge-long-history.html
(5)http://archive.archaeology.org/9701/newsbriefs/syphilis.html
(6)http://www.cdc.gov/std/syphilis/stdfact-syphilis.htm
(7)http://www.webmd.com/sexual-conditions/guide/syphilis
(8)http://www.intheknowzone.com/sexual-health-topics/syphilis/history-of-syphilis.html
(9)http://www.gendercentre.org.au/resources/polare-archive/archived-articles/syphilis.htm
(10)http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1360276/
(11)http://www.ncbi.nlm.nih.gov/pmc/articles/PMC257764/
(12)http://cmr.asm.org/content/19/1/29.full
References
Created by Rachael Acosta, student of Tyrrell Conway at the University of Oklahoma.
