USMLE

Leptospira interrogans

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Bacteria - Gram Negative
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Leptospira interrogans 

  • Characteristics
    • Spirochete with hook-shaped ends
      • Does not gram stain well 
  • Transmission
    • Found in water contaminated with animal urine
      • Animals (rodents, dogs, cattle, sheep) are natural reservoirs
      • Seen in freshwater sports (e.g. swimmers, canoers, kayakers, etc.)
      • Most prevalent in tropics (e.g. Hawaii)
  • Presentation
    • Leptospirosis
      • Conjunctival suffusion
        • extreme redness of eye without exudate
        • Photophobia may be rarely seen
      • Flu-like symptoms (non-productive cough, myalgias)
    • May be complicated by liver and renal failure
      • Also known as Weil’s disease (icterohemorrhagic leptospirosis) 
      • Severe form that presents with jaundice and azotemia
  • Diagnosis 
    • Clinical and laboratory findings are not very sensitive or specific; most diagnosis is clinical
    • Microscopic Agglutination Test
      • Reference standard assay, but is not widely available
    • Immunoglobulin M via enzyme-linked immunosorbent assay (ELISA)
    • Dark-field microscopy 
  • Treatment 
    • Doxycycline or Azithromycin (macrolide) for mild disease 
    • Penicillin or ceftriaxone used for severe disseminated disease