Medicine & USMLE

Treponema pallidum: Overview

Bacteria - Gram Negative
  1. Neisseria spp: Overview
  2. Neisseria gonorrhoeae
  3. Neisseria meningitidis
  4. Haemophilus influenzae
  5. Bordetella pertussis
  6. Brucella
  7. Legionella pneumophila
  8. Pseudomonas aeruginosa: Overview
  9. Pseudomonas aeruginosa: Disease
  10. Salmonella Overview
  11. Salmonella typhi
  12. Salmonella enteritidis
  13. Shigella
  14. Yersinia enterocolitica
  15. Escherichia coli: Overview
  16. Enterohemorrhagic E. Coli (EHEC)
  17. Enterotoxigenic E. Coli (ETEC)
  18. Klebsiella pneumoniae
  19. Campylobacter jejuni
  20. Vibrio spp.
  21. Helicobacter pylori
  22. Borrelia burgdorferi (Lyme Disease)
  23. Leptospira interrogans
  24. Treponema pallidum: Overview
  25. Treponema pallidum: Diagnosis
  26. Congenital syphilis
  27. Chlamydia: Overview
  28. Chlamydia trachomatis
  29. Chlamydia pneumoniae vs. psittaci
  30. Rickettsia rickettsii
  31. Rickettsia typhi vs. prowazekii
  32. Anaplasma vs. Ehrlichia
  33. Coxiella burnetii (Q fever)

Treponema pallidum overview

  • Characteristics
    • Spirochete
    • Technically gram negative
      • Too thin to be visualized on light microscopy
    • Motile
  • Transmission
    • Sexually transmitted
      • Frequent in MSM, HIV positive patients
      • Most commonly intimate contact with infectious lesion
      • Blood transfusion
      • Transplacentally from mother to fetus
      • Common in developing countries
  • Disease (syphilis
    • Primary syphilis
      • Painless chancre (ulcer on genitals)
        • Localized disease, occurs within 5 weeks from contact
        • Painless ulcer with raised, red borders
        • Heals within weeks without treatment
    • Secondary syphilis
      • Disseminated disease presenting 5-10 weeks after chancre resolution
      • condyloma lata
        • smooth, painless, wart-like white/grey lesions on genitals
      • maculopapular rash including palms and soles
        • Note: Palm and soles rash is also seen in Coxsackievirus and Rocky Mountain spotted fever
      • constitutional symptoms, lymphadenopathy, patchy hair loss also seen
    • Latent syphilis (+ serology without symptoms) may follow
    • Tertiary syphilis
      • Occurs many years after untreated infection
      • Gummas (chronic granulomas)
        • Painless, indurated granulomatous lesion that may ulcerate
        • Found in skin, bones, liver, heart (new murmur)
      • Aortitis/aortic aneurysm
        • Involvement and obliteration of vasa vasorum
          • blood vessels supplying thoracic aorta (not present in abdominal aorta)
        • Resulting  inflammation and ischemia weakens the aortic wall, causing aneurysm
      • Neurosyphilis
        • Can technically occur at any stage of syphilis, but more common in late-stage disease
        • Tabes Dorsalis
          • Occurs decades after initial infection with untreated syphilis
          • Posterior column of spinal cord impaired
            • Loss of proprioception and vibratory sense
            • Hyporeflexia
            • Stabbing nerve pain
            • Sensory ataxia
              • Broad-based gait
              • Inability to maintain balance with eyes closed (+ Romberg sign)
              • Charcot joint (joint damage due to neurodegeneration)
            • Loss of bladder function (neurogenic incontinence)
        • Argyll Robertson pupils
          • Constrict normally in accommodation (light-near-dissociation)
          • Fail to constrict in response to light (non-reactive)
          • Thought to result from damage to tectum of midbrain
        • Meningoencephalitis
          • Presents with headaches, dementia, or stroke
        • General paresis
          • Presents with progressive dementia and diffuse paralysis
  • Treatment
    •  Penicillin G
      • IM penicillin for primary or secondary syphilis and early latent syphilis
      • IV penicillin G for late latent syphilis 
      • Doxycycline as alternative for treating early and late latent syphilis
    • Treatment can cause Jarisch-Herxheimer reaction
      • Flu-like syndrome (fever, chills, headache, myalgia) after antibiotics are started
        • due to killed bacteria releasing gram-negative endotoxin