Spirochaetes

• What type of bacteria are spirochetes?

  Gram-negative bacteria
• What does the term "spirochetes" mean in Greek?

  Coiled hairs
• What unique feature do spirochetes possess that aids in their locomotion?

  Axial filaments
• Where are axial filaments located in spirochetes?

  In the periplasmic space
• How do axial filaments enable pathogenic spirochetes?

  They allow spirochetes to burrow through their hosts' tissues
• What are the three genera of spirochetes based on gross morphology?

  • Treponemes: slender with tight coils
  • Borrelia: thicker with fewer and looser coils
  • Leptospira: resemble Borrelia but have hooked ends
• What is the most important treponemal species that causes human disease?

  Treponema pallidum
• How are the subspecies of Treponema pallidum distinguished?

  By their epidemiologic characteristics and clinical presentation
• What diseases are caused by different subspecies of Treponema pallidum?

  • Syphilis: T. pallidum pallidum
  • Yaws: T. pertenue
  • Pinta: T. carateum
  • Endemic syphilis (bejel): T. pallidum endemicum
• Why is T. pallidum extremely sensitive and unable to survive exposure to drying or disinfectants?

  Because it cannot be spread through contact with inanimate objects
• What is the most common route of spread for syphilis?

  Direct sexual contact
• Can T. pallidum cross the placental barrier?

  Yes, it can cross the placental barrier in a syphilitic mother
• What happens to T. pallidum if donated blood is stored at refrigerator temperatures for 3-4 days?


  The treponemes die
• What are the four stages of the clinical course of syphilis?

  1. Primary syphilis
  2. Secondary syphilis
  3. Latent syphilis
  4. Tertiary syphilis
• What is the earliest indication of syphilis infection?

  The appearance of a small hard ulcer called a chancre
• Where can a chancre appear on the body?

  On the external genitalia, cervix, perianal area, anal canal, or lips
• What is the nature of the chancre associated with primary syphilis?

  It is painless and has an exudate of serum in the center
• How long does it take for a chancre to heal?

  Within 3-6 weeks
• What clinical signs appear during secondary syphilis?

  Prominent skin lesions dispersed over the entire body surface
• What symptoms do patients typically experience during secondary syphilis?

  Flulike syndrome with sore throat, headache, fever, myalgias, anorexia, and lymphadenopathy
• How long do the symptoms of secondary syphilis usually last?

  They usually disappear within 3 months
• What characterizes the latent stage of syphilis?

  There are no clinical manifestations but serological evidence of infection
• How long can the latent period of syphilis last?

  20 years or longer
• Why is tertiary syphilis relatively rare today?

  Due to widespread use of antibiotics
• What are the three basic forms of tertiary syphilis?

  1. Gummas: painful, swollen tumors in tissues
  2. Cardiovascular syphilis: damage to small arteries in the aortic wall
  3. Neurosyphilis: involvement of any part of the nervous system
• How can congenital syphilis occur?

  A pregnant syphilitic woman can transmit T. pallidum to the fetus through the placenta
• What are some potential outcomes of syphilis in pregnancy?


  Abortion, premature delivery, stillbirth, and perinatal death
• What are some signs of congenital syphilis in childhood?

  Keratitis, Hutchinson’s teeth, saddle-nose, periostitis, and CNS anomalies
• What is the laboratory diagnosis process for syphilis?

  • Microscopy: important for screening primary syphilis
  • Serology: reactive at the secondary stage
• Why is microscopy important for screening primary syphilis?

  Because serological tests for this stage are not reliable
• What types of microscopy are used to examine exudate from the primary chancre?

  Dark-field microscopy and ultraviolet microscopy
• Why can't T. pallidum be seen in Gram-stained preparations?

  Because it is very thin
• What are the two types of serological tests for syphilis at the secondary stage?

  • Non-specific tests (non-treponemal tests)
  • Specific tests (treponemal tests)
• What are non-treponemal tests used for?

  For screening and to determine treatment efficacy
• What do non-treponemal serological tests detect?

  Reagin-type antibodies
• What is the antigen used in non-treponemal tests derived from?

  An extract of beef heart (cardiolipin)
• What are examples of non-treponemal tests?

  VDRL test and Rapid plasma reagin (RPR) test
• What do treponemal-type serological tests look for?

  Antibodies against the spirochete itself
• What are some common treponemal tests in use?

  ELISA, FTA-ABS, and MHA-TP tests
• What are the three nonvenereal treponemal diseases?


  1. Endemic syphilis
  2. Yaws
  3. Pinta