Treponema pallidum


>Leptospira species (includes pathogenic and saprophytic species)
>Borrelia species (36 known strains). Most common strains associated with Lyme disease:
     1] Borrelia burgdorferi
     2] Borrelia afzelii
     3] Borrelia garinii
>Treponema pallidum led

Treponema pallidum


  • Spirochaete bacterium with subspecies that cause treponemal diseases such as syphilis, bejel, pinta and yaws.  
  • Treponemes have a cytoplasmic and outer membrane.
  • Using light microscopy treponemes are only visible using Dark field illumination.  
  • T. pallidum causes syphilis and is a motile spirochaete that is generally acquired by close sexual contact, entering the host via breaches in squamous or columnar epithelium. 
  • The helical structure of T. pallidum pallidum allows it to move in a corkscrew motion through a viscous medium such as mucus. It gains access to host’s blood and lymph systems through tissue and mucous membranes.

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Important considerations:  The choice of an agent should be based on local antimicrobial sensitivities, site of infection, cost, and comorbid conditions.   Generally, the most common agents/regimens are listed first.

Syphilis (primary, early latent):  Less than one year.
Primary: ulcer or chancre at site of infection.
Secondary: rash, mucocutaneous lesions, adenopathy

  1. Benzathine Penicillin G (Bicillin L-A) 2.4 million units IM as a single dose
  2. PCN-allergic patients / alternatives:  Ceftriaxone 1 gram IV/IM q24h x 10 – 14 days OR  Doxycycline 100mg twice daily for 2 weeks  OR  Azithromycin 2000mg x 1 OR
    Tetracycline 500mg four times daily for 2 weeks.   Note: pregnant women should be treated with pcn (desensitize patient if necessary).

Syphilis (late, or greater than one year duration):  

  1. Benzathine Penicillin G 2.4 million units IM weekly x 3 doses
  2. PCN-allergic patients / alternatives:   Doxycycline 100mg twice daily for 28 days OR  tetracycline 500mg orally four times daily for 28 days.   Note: pregnant women should be treated with pcn (desensitize patient if necessary).

Neurosyphilis:  (Desensitize penicillin allergic patients)

  1. Penicillin G  3 to 4 million units q4h IV for 10-14 days
  2. Alternative(s):   Procaine penicillin 2.4 million units IM once daily  PLUS  probenecid 500 mg orally four times daily for 10-14 days.


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