Treponema pallidum Treponema pallidum infections

Treponema pallidum appearance

  • spirochaete (spiral-shaped) bacterium with a flexible cell wall
  • Gram-negative, but very slim (0.15 µm or less) and can only be visulized by dark-field microscopy, electron microscopy, or special staining techniques that effectively increase their diameter to bring them within the resolving power of the light microscope (immunofluorescence techniques, silver impregnation techniques)
  • motile, axial filaments (endoflagella)
  • non-spore-forming

Infections caused by Treponema pallidum

Treponema pallidum ssp. 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. ssp. 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.

Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact.

The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, and tertiary). The primary stage classically presents with a single chancre (a firm, painless, non-itchy skin ulceration), secondary syphilis with a diffuse rash which frequently involves the palms of the hands and soles of the feet, latent syphilis with little to no symptoms, and tertiary syphilis with gummas, neurological, or cardiac symptoms. It has, however, been known as "the great imitator" due to its frequent atypical presentations. Diagnosis is usually made by using blood tests.

Syphilis is thought to have infected 12 million additional people worldwide in 1999, with greater than 90% of cases in the developing world. After decreasing dramatically since the widespread availability of penicillin in the 1940s, rates of infection have increased since the turn of the millennium in many countries, often in combination with human immunodeficiency virus (HIV)(Wikipedia).

Syphilis treatment

  • benzathine penicillin G (intramuscular)
  • penicillin G potassium (intravenous); neurosyphilis

  • ceftriaxone

Penicillin allergy
  • doxycycline
  • azithromycin

Syphilis vaccination

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, and because T. pallidum outer membrane proteins have not been unambiguously identified (Wikipedia).



Treponema pallidum morphology Treponema pallidum cell morphology Treponema pallidum spirochete