Spirochaetes

• Spyro kits


  A type of bacteria
• Types of Spyro kits

  • Tripona
  • Boralia
  • Leptospira
• Spyro kits


  • Thin, helical shape
  • Motile with screw-like motion
  • Gram-negative with inner cell membrane, peptidoglycan layer, and outer membrane
  • Have periplasmic flagella
• Structure of Spyro kit flagella

  1. Flagella originate from inner cell membrane

  2. Reside in periplasmic space

  3. Wrap around cell to enable screw-like motion
• Tripona


  Causes syphilis
• Boralia


  Causes relapsing fever and Lyme disease
• Leptospira


  Causes different types of disease
• Spyro kits cannot be easily visualised using normal staining and light microscopy
• Tripona pallidum


  • Thin, tightly coiled with straight ends
  • Requires dark-field or fluorescence microscopy to visualise
  • Cannot be grown in vitro, requires rabbit epithelial cells
  • Facultatively anaerobic, can use glucose oxidatively
• Tripona pallidum has 3-4 periplasmic flagella attached at each cell end
• Boralia and Leptospira have different numbers of periplasmic flagella compared to Tripona
• Virulence factors of Tripona pallidum

  • Outer membrane adhesive proteins
  • Hyaluronidase to degrade tissue
  • Coating with host fibronectin to evade phagocytosis
  • Tissue disruption from host immune response
• Pathogenesis


  The process by which a disease or condition develops and progresses
• Virulence factors


  Characteristics of a pathogen that contribute to its ability to cause disease
• Virulence factors of pathogens

  • Outer cell membrane proteins
  • Adhesive proteins that promote adherence to host cells
  • Hyaluronidase that degrades hyaluronic acid in tissue lining
  • Coating with host cell fibronectin proteins that protect against phagocytosis
• Pathogens enter tissue lining

  They degrade tissue lining using hyaluronidase, cover themselves with fibronectin from host cells, and the host immune response further weakens the host
• Treponema pallidum has only humans as a natural host
• The only way to contract syphilis is through contamination with human materials
• Safe sex is important to prevent syphilis
• Borrelia


  A genus of spiral-shaped, Gram-negative bacteria
• Borrelia


  • Have 7-20 periplasmic flagella that provide twisting/screw-like motility
  • Can be visualized by light microscopy using special staining techniques (not Gram stain)
• Microaerophilic


  Requiring low levels of oxygen for growth
• Borrelia have slow growth rates, with 18 hour division times
• Borrelia species


  • Borrelia burgdorferi (causes Lyme disease)
  • Borrelia species that cause relapsing fever
• Borrelia use endotoxins rather than exotoxins to degrade host tissues
• Host immune reactivity against Borrelia may contribute to clinical disease in Lyme disease
• Vectors for Borrelia


  • Ixodes ticks (for Lyme disease)
  • Lice and ticks (for relapsing fever)
• Lyme disease and relapsing fever are major vector-borne diseases
• Leptospira


  Spiral-shaped bacteria with hooks at one or both ends
• Leptospira


  • Have 2 periplasmic flagella that attach at both ends
  • Are obligate aerobes, requiring oxygen for growth
  • Grow slowly, needing vitamins, fatty acids, and amino acids
• Leptospira interrogans


  The human pathogenic species of Leptospira
• There are over 500,000 severe cases of human leptospirosis worldwide, with 2-5% mortality
• Leptospira can cause severe, life-threatening infections like renal failure and meningitis
• Leptospira invade tissues


  They disrupt the endothelial lining of blood vessels, leading to organ damage
• Reservoirs for Leptospira


  • Rodents
  • Livestock
  • Companion animals like dogs
• Leptospira can be transmitted through contact with urine from infected animals