Overview
This lecture covers spirochetes: their characteristics, important genera, related diseases—especially syphilis—and key diagnostic methods and treatments.
Introduction to Spirochetes
- Spirochetes are spiral-shaped, motile bacteria.
- Major genera: Treponema, Borrelia, and Leptospira.
Treponema and Syphilis
- Treponema pallidum causes syphilis; it is slender and corkscrew-shaped.
- Treponema pallidum subspecies pertenue is the agent of yaws (non-venereal, tropical disease).
- Other species include Treponema endemicum (endemic syphilis) and Treponema paraluiscuniculi (rabbit syphilis).
- The axial filament (like bacterial flagella) provides motility.
Stages of Syphilis
- Primary syphilis: painless ulcer (chancre), lymphadenopathy; appears 2-4 weeks after infection; transmitted sexually or by vertical (mother-to-fetus) route.
- Secondary syphilis: mucocutaneous lesions, generalized lymphadenopathy, skin eruptions; highly infectious; occurs 6-8 weeks after chancre.
- Latent syphilis: asymptomatic; can be early (≤1 year after secondary) or late (>1 year); sexually non-infectious but can transmit to fetus.
- Tertiary (late) syphilis: may affect heart, CNS, skin, bones; hallmark is gumma (granulomatous lesion); not infectious except mother-to-fetus.
- Congenital syphilis: transmitted to fetus, causes stillbirth, deformities, blindness, and deafness.
Treatment and Prevention
- Penicillin is the drug of choice for syphilis.
- Tetracycline is an alternative for penicillin-allergic patients.
- Prevention includes early detection and testing, especially for sexually active individuals.
Diagnostic Tests for Syphilis
- Dark field microscopy: direct detection in primary syphilis.
- Non-treponemal tests: VDRL (Venereal Disease Research Laboratory), RPR (Rapid Plasma Reagin); used for screening.
- Treponemal confirmatory test: FTA-ABS (Fluorescent Treponemal Antibody Absorption).
Borrelia
- Borrelia burgdorferi causes Lyme disease; Borrelia recurrentis causes relapsing fever.
- Transmitted by ticks (Ixodes species).
- Lyme disease symptoms: skin lesion (erythema migrans), neurological and cardiac issues, arthritis.
- Diagnosis by serology (immunofluorescence, ELISA).
Leptospira
- Leptospira interrogans causes leptospirosis.
- Found in kidneys of rodents/animals; transmitted via contaminated water, food, or urine.
- Clinical signs: mild fever, jaundice, renal failure, conjunctivitis.
- Diagnosis: rise in IgM antibody titers.
Key Terms & Definitions
- Spirochete — spiral-shaped, motile bacterium.
- Chancre — painless ulcer of primary syphilis.
- Lymphadenopathy — swelling of lymph nodes.
- Gumma — granuloma in tertiary syphilis.
- Dark field microscopy — technique to visualize spirochetes.
- VDRL/RPR — screening blood tests for syphilis.
- FTA-ABS — confirmatory test for syphilis antibodies.
Action Items / Next Steps
- Review and memorize the stages and clinical features of syphilis.
- Study diagnostic algorithms for syphilis testing.
- Prepare for detailed immunology and serology lessons on syphilis testing.