spirochetes

• Order

  • Spirochaetales
• Family


  • Spirochaetaceae
• Genus


  • Borrelia
  • Treponema
  • Leptospira

  
• Spirochetes


  • Slender, flexous, helically shaped, unicellular bacteria
  • 0.1 – 0.5µm =width
  • 5 – 20 µm = long
  • gram-negative
  • anaerobic, facultatively anaerobic, aerobic - depending on the species

  
• Spirochetes (Motility)


  • Flexible cell wall around which several fibrils are wound – for motility
  • Periplasmic flagella – also known as: axial fibrils, endoflagella, axial filaments - periplasmic fibrils
• Spirochetes (Multiplication)


  • Treponema – transverse fission
  • Leptospira - binary
  • Borelia - fission
• Leptospires (Genus Leptospira)


  • Tightly coiled, thin, flexible
  • 0.1µm wide
  • 10 - 15µm long
  • spirals are very close together, appears to be cocci in chains
  • One or both ends have hook or bent (Shepherd's crook)
  • Motion is rapid and rotational (corkscrew – like)
• Genus Leptospira


  • All have two periplasmic flagella
  • Can not be readily stained, but can be impregnated with silver and visualized
  • Unstained smear can not be visualized by bright field microscopy
  • Visible by dark field, phase contrast & immunofluorescent microscopy
  • Obligate aerobes

  
• Genus Leptospira


  • Pathogenic organism - Leptospira interrogans
  • Saprophytes - Leptospira biflexa

  
• Genus Leptospira (Virulence factors and Pathogenicity)


  • Reduced phagocytosis in the host
  • Soluble hemolysin produced by some virulent strain
  • Cell mediated sensitivity to leptospiral antigen by the host
  • Small amount of endotoxins produced by some strains
• Infections caused by Leptospires


  • Leptospirosis
  • Swineherd's disease
  • Weil's disease
  • Fort Bragg fever
  • Pretibial fever
  • Canicola fever
  • Autumnal fever
• Leptospirosis


  • Enter the human host thru small breaks in the skin or intact mucosa
• Leptospirosis (Clinical manifestation)


  • Major renal lesion – interstitial nephritis with associated glomerular swelling and hyperplasia that does not affect the glomeruli
  • Conjucntival suffusion – most characteristics physical findings
  • Weil disease – severe systemic disease which includes: renal failure, Hepatic failure, Intravascular disease, death
• Leptospirosis (Epidemiology)

  • Natural host - Live in the lumen of renal tubules, Excreted in urine
  • Reservoir - Dogs, Rats and other rodents
• Leptospirosis (Transmission)


  • Directly by contact with the urine of carriers
  • Indirectly by contact with bodies of water contaminated with the urine of carriers
• Leptospirosis (Control measures)


  • Rodent elimination
  • Drainage of contaminated water
• Leptospirosis (Laboratory Diagnosis)


  • Collection and handling - Acute phase (first week of the disease): Blood or CSF, Urine – yield is much higher after the first week of illness
  • Optimal recovery – fresh specimen inoculated directly into culture media
• Leptospirosis (Laboratory Diagnosis - Microscopic examination)


  • Direct demonstration of leptospires – 1st week but not recommended
• Leptospirosis (Laboratory Diagnosis - Isolation and identification)


  • Direct inoculation of 1 to 2 drops of freshly drawn blood or CSF
  • Can be grown in artificial medium: Fletcher's semi-solid, Stuart liquid, Ellinghausen-McCullough-Johnson-Harris (EMJH) semi-solid medium
• Leptospirosis (Laboratory Diagnosis - Serologic test)


  • Leptospiral bacteremia - IgM antibodies – detected within 1 week after onset of disease, IgG antibodies – detected a month or more after the onset of illness
• Borreliae (Genus Borrelia)


  • Most species cause relapsing fever except for Borrelia burgdorferi which causes Lyme borreliosis
  • All pathogenic Borrelia are arthropod – borne
  • Much less tightly coiled than those of the leptospires
  • Stains easily and visualized by bright field microscopy

  
• Significant species (Genus Borrelia)


  • Relapsing fever - Borrelia recurrentis, Borrelia duttonii
  • Lyme disease - Borrelia burgdorferi

  
• Borrelia recurrentis (Virulence factors)


  • Antigenic variation – causes relapse
  • Evades complement by acquiring and displaying suppressive complement regulators - C4b- binding protein, Factor H - allows complement evasion and immune system suppression
• Borrelia recurrentis (Epidemiology)


  • Tick-borne endemic relapsing fever - Soft ticks of Genus Ornithodoros, Via infected saliva during attachment
  • Louse-borne epidemic relapsing fever - Body louse of Pediculus humanus, Infected lice are crushed or scratched into the skin
• Borrelia recurrentis (Laboratory diagnosis)


  • Microscopic examination - Giemsa or Wright's stained blood smears taken during the febrile period
• Borrelia burgdorferi (Virulence factors)


  • Binding factor H – allows complement evasion and immune system suppression
  • Ability to bind plasminogen and urokinase-type plasminogen activator to its surface - Convert plasminogen to plasmin – fascilitate tissue invasion
• Borrelia burgdorferi (Clinical manifestation)


  • Lyme disease is divided into two stages: Early stages - 1st stage (localized) - Erythema migrans, 2nd stage (early disseminated) - 2ndary skin lesions, migratory joint and bone pain, Splenomegaly, severe malaise and fatigue, Neurologic and cardiac pathology
  • 3rd stage (late persistent) - Cardiac, Mucoloskeletal, Neurologic system, Arthritis is the most common symptoms
• Borrelia burgdorferi (Epidemiology)


  • Transmitted via bite of infected Ixodes ticks
  • Pathogen transmission is associated with the length of attachment of ticks to skin
  • Three species - Borrelia burgdorferi sensu lato, Borrelia burgdorferi sensu stricto, Borrelia garinii, Borrelia afzelii

  
• Borrelia burgdorferi (Laboratory diagnosis)


  • Specimen collection - serum for serology, PCR, Urine antigen, CD57
  • Two tiered approach for Serologic test - 1st step (IFA or EIA screen), 2nd step (IgM and/or IgG Western blot)
• Treponemes (Genus Treponema)


  • 0.1 – 0.2µm in thickness
  • 6 - 20µm in length
  • Difficult to visualized in bright field microscope
  • Can be visualized using dark field microscope
  • Three periplasmic flagella are inserted into each end of the cell

  
• Genus Treponema


  • Treponema pallidum subsp. pallidum - syphilis
  • Treponema pallidum subsp. pertenue - yaws
  • Treponema pallidum subsp. endemicum - endemic syphilis
  • Treponema carateum - pinta
• Treponema pallidum subsp. pallidum (Virulence factors)


  • Ability to cross intact mucous membranes and placenta
  • Disseminate throughout the body
  • Infect almost any organ system
  • Antigenic variation of cell surface protein
• Treponema pallidum subsp. pallidum (Transmission)


  • Direct sexual contact with active primary and secondary syphilitic lesion
  • Genital organs – usual site of inoculation
  • Non genital contact with a lesion on the lip, transplacental transmission to a fetus
• Treponema pallidum subsp. pallidum (Stages of Syphilis)


  • Primary stage - Primary lesion develops 10 – 90 days after infection, Chancre – teeming with treponemes, Extremely infectious, Found on the Cervix, vaginal wall, anal canal, No systemic signs and symptoms
  • Secondary stage - 2 – 12 weeks after development of primary lesion, Secondary lesions of the skin and mucous membranes – highly infectious
  • Tertiary syphilis - Development of granulomatous lesions (gummas) in the Skin, Bones, Liver, Degenerative changes in the CNS – neurosyphilis, Syphilitic cardiovascular lesions, not infectious
• Treponema pallidum subsp. pallidum (Laboratory diagnosis)


  • Lesions of primary and secondary syphilis contains large number of spirochetes
  • Dark field microscopy is performed
  • Oral lesions should not be examined
  • Culture methods are not available
  • Serology is the normal method of diagnosis
  • Demonstration of motile treponemes in the material from chancre is diagnostic for primary syphilis
• Treponema pallidum subsp. pallidum (Serologic tests)


  • Two major types - Nontreponemal test (Detect reaginic antibodies, Excellent screening tests - VDRL, RPR), Treponemal test (Detect antibodies specific for treponemal antigen, Example - TP-PA, EIA)
  • Both have low sensitivities in the primary stage, 100% sensitivity in the secondary stage, Treponemal test retain very high sensitivity in the tertiary stage
• Non venereal treponemal diseases


  • Treponema pallidum subsp. pertenue - Disease – yaws, Course of yaws resembles that of syphilis, Early stage lesions -granulomatous nodules
  • Treponema pallidum subsp. endemicum - Disease - Endemic syphilis or Bejel, Can progress to gummas of the skin, bones and nasopharynx, Transmitted by direct contact or sharing contaminated utensils, Dark field microscopy is not useful because of normal oral spirochetal biota
  • Treponema carateum - Diseased - Pinta, Acquired by person to person contact, Rarely transmitted by sexual intercourse