Treponema pallidum (PCR)

Swab of skin or mucous membrane lesion

Treponema pallidum is a spiral-shaped, motile bacterium that causes the sexually transmitted infection known as syphilis.
The bacterium is mainly spread through sexual intercourse (vaginal, anal or oral) and can infect various parts of the body, including the genitals, anus, mouth and other mucous membranes.
The symptoms of syphilis vary depending on the stage the disease is in (primary, secondary, latent and tertiary stage). The disease is treatable with antibiotics, especially in the early stages of infection.

In the primary stage, syphilis classically presents with a single chancre (skin ulceration with a diameter of 1-2 cm) but there can also be multiple lesions.
In the secondary stage, a diffuse rash occurs frequently involving the palms of the hands and soles of the feet, and there can also be sores in the mouth or vagina.
In the latent stage (which can last for years) there are few or no symptoms.

In the tertiary stage (approximately 3-15 years after the initial infection) syphilis may present as one of three forms:
- gummatous syphilis: soft, tumor-like balls of inflammation (gummas) of various sizes form in different tissues (mainly skin, bone, liver)
- cardiovascular syphilis: development of syphilitic aortitis which can result in the formation of aortic aneurysms
- late neurosyphilis: in general, involvement of the central nervous system in syphilis can happen at any stage. With early involvement of the central nervous system, the disease typically manifests as syphilitic meningitis or is asymptomatic. In later stages, the infection can manifest as meningovascular syphilis leading to general paresis (syphilitic paresis) or degeneration of neural tracts in the dorsal root ganglia.

Syphilis can also be transmitted from mother to baby during pregnancy or birth, resulting in congenital syphilis.
Approximately 40% of babies born to women with untreated syphilis can be stillborn or die from the infection as a newborn. Babies born with congenital syphilis can have bone damage, severe anemia, enlarged liver and spleen, jaundice, nerve problems causing blindness or deafness, meningitis, or skin rashes.