Clinically important Spirochaete infections

• Spirochaetes discussed in the lecture:

  • Leptospira interrogans causing Leptospirosis
  • Treponema pallidum ssp. pallidum causing Syphilis
  • Borrelia burgdorferi causing Lyme disease (borreliosis)
• Spirochaetes are motile with flagellae in the periplasmic space, too thin to see on light microscopy, and require specialized culture media for growth
• Diagnosis of spirochaete infections in the laboratory can be done through:

  • Fluorescent microscopy
  • PCR
  • Serology (testing blood or CSF for evidence of an immune response)
• Clinical features of Syphilis:

  • Infection progresses in stages and may become chronic if untreated
  • Transmission: sexual, vertical (in utero from infected pregnant woman via hematogenous spread to her fetus)
  • Incubation period: average 3 weeks (10-90 days)
  • Period of Infectiousness: primary and secondary stages (infectious lesions or rash present)
• Syphilis pathogenesis involves:

  • Direct contact between mucous membrane and infected lesion
  • Transplacental spread
  • Lesions of primary and secondary syphilis are highly infectious
  • Structure of outer membrane "hides" the spirochaete from the host immune response
• Clinical course of Syphilis (untreated):

  • Day 0: Exposure
  • Day 21 approx: Chancre (primary syphilis)
  • Incubation period: 10-90 days
  • 4-10 weeks: Secondary syphilis
  • Latent syphilis: Years/decades
  • Tertiary syphilis
• Laboratory diagnosis of Syphilis includes:

  • Dark field microscopy showing spirochaetes in lesion fluid
  • Serology tests like RPR (non-treponemal) and TPPA (treponemal)
  • Tertiary Syphilis can present with granulomatous lesions, neurosyphilis, and cardiovascular syphilis
• Treatment of Syphilis:

  • Penicillin is the treatment of choice
  • Doxycycline can be used in penicillin allergy
  • Prevention includes safe sex, contact tracing of sexual partners, and antenatal screening and treatment of mothers with positive serology
• Likely Diagnosis for a 25-year-old hill walker with a circular, erythematous, non-itchy rash on their leg, low grade fever & joint pain: Lyme disease
• Lyme disease is caused by Borrelia burgdorferi, transmitted by hard ticks (Ixodes spp.)
• In Lyme disease, early signs and symptoms include an Erythema migrans rash with a central redness and outer erythematous ring, while later signs can involve headache, fever, conjunctivitis, myalgia, and neurological manifestations like facial nerve palsy and meningitis
• Chronic Lyme disease may present post-infectious symptoms but does not require further courses of antibiotics once treated appropriately
• Laboratory diagnosis for Lyme disease includes serology for later stages and PCR on joint fluid or tissue for arthritis/skin manifestations
• Treatment for Lyme disease varies: Doxycycline for early manifestations, Amoxicillin for pregnancy & young children, and IV ceftriaxone for neuroborreliosis
• Prevention of Lyme disease involves protective clothing, tick repellent, and careful tick removal
• Likely Diagnosis for a 30-year-old admitted to the ICU with fever, low blood pressure, jaundice, elevated transaminases, and acute kidney injury after canoeing in the River Liffey: Leptospirosis
• Leptospirosis is caused by Leptospira interrogans, transmitted through contact with water, moist soil, or vegetation contaminated with the urine of infected animals
• Clinical manifestations of leptospirosis can range from mild febrile illness to severe forms like Weil's disease, characterized by headache, fever, rash, shock, thrombocytopenia, abnormal liver function, jaundice, and acute kidney injury
• Prevention of leptospirosis includes rodent control, avoiding water sources if there are skin abrasions or cuts, and there is no vaccine available for humans