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Treponema pallidum

Order: Spirochaetales

Genus: Treponema

Species: pallidum

First dicovered in 1905 by German bacteriologist Fritz Schaudinn (1871-1906). This Gram-negative, spirochete (spiral-shaped) organism is highly motile. Movement is achieved by means of filaments which lie below the outer membrane, within the periplasmic space, of the organism. These filaments, or periplasmic flagella as they are also known, wind around the body and are attached at both poles (i.e. ends). Movement resembles that of a cork screw, see image on left. On average the organism will measure 0.15µm in diameter and 10 -1 3µm in length. Diseases caused by Treponema are called treponematoses.


Growth Requirements

Treponema prefer almost neutral environments within the pH range of 7.2 - 7.4. Their optimal growth temperature is from 30 ⁰C - 37⁰C and as microaerophiles they require oxygen for survival but in very small amounts. Due to their complex nutritional requirements Treponema are extremely difficult to cultivate in the laboratory. However, these complex requirements are met within humans who are the sole natural host to the organism, it can be grown in apes and rabbits.These organisms are parasitic and therefore pathogenic to their human host. They attach to the epithelium of the host by means of a hook and can be found in the oral cavity, intestinal tract and perigenital areas. Studies on human volunteers have found that only 57 organisms were required for infection to occur. Once attached the organism will rapidly multiply and can enter the blood stream.


History

Subspecies Treponema pallidum pallidum is the organism responsible for syphilis, a disease first seen in fifteenth century Europe when Christopher Columbus returned from his explorations of the New World. Leading scholars at the time believe it was brought to Europe, by the explorers, from these previously unkown parts of the world. Today it is believed the more probable explanation is that Treponema pallidum evolved from a subspecies already present in southern Europe and combined with naiviety and promiscuity at the time there arose worldwide transmission which continues today. The disease is prolific worldwide with a reported 11 000 new cases reported in the United States alone in 2007. This organism is transferred through sexual contact, regardless of sexual preference with the chance of exposure increased by the number of sexual partners.


Pathogenesis

The symptoms will usually take place in 3 stages - approximately 21 days after exposure a painless area of ulceration can form, called a chancre. Despite the absence of pain, the area will be raw and will be full of treponemes and therefore highly con120px-Extragenital_syphilitic_chancre_of_the_left_index_finger_PHIL_4147_lores.jpgtagious (http://www.patient.co.uk/doctor/Syphilis.htm). Ulceration is usually in the genital area but can form at any area where the skin is compromised and exposure has taken place, see image at right. Secondary symptoms can appear 2-6 weeks after the chancre has disappeared and can include lesions on the skin and mucous membranes, hair loss, fever, rash and joint pains. The patient is highly infectious during this stage and symptoms can persist for months. Tertiary, third, stage symptoms can include soft tumors, gummas, in the organs and irreversible brain and cardiovascular damage.


Treatment

All stages are treated with antibiotics, these include Penicillin, Tetracycline and Doxycycline. Dosages depend on the stage of the disease. Even after successful treatment low levels of antibodies can remain in the body and expectant mothers who are infected can pass the infection on to the baby resulting in still birth or severe birth defects. (http://www.cdc.gov/std/syphilis/default.htm).


Extras

A few people in history reputeded to have succumed to the disease include Adolf Hitler, Mussolini, Beethoven, Napoleon, Al Capone and Christopher Columbus himself.