What are the three major genera of spirochetes?
- treponema
- borrelia
- leptospira
What causes syphilis? Why is it difficulty to see under light microscopy? How can you improve visibility? What are its physical and biochemical characteristics?
- -Treponema pallidum
- -hard to see b/c they are long, but wicked skinny; use darkfield, immunofluoro, silver salts or EM
- -cannot be cultured!
- -would be Gm-, motile, helicoid and flexible w/ axial filament = internal flagella
- -easily killed by heat, soap & water, or drying but very resistant to freezing (revived after -80°C!)
What are the stages of syphilis and how do you dx each one?
1° after 1-4 wks incubation
- infectious
- -DERM: spontaneously-healing, genital chancres
- -SYST: focal lymphadenopathy
2° after 2-10 wks post 1° onset
- infectious
- -DERM: generalized papulosquamous rash, condyloma lata
- -SYST: h/a, f/c, leukocytosis, wt. loss, sore throat
- -RENAL: dysfunction
3° after 2-20 years
- not infectious
- -SYST: gummas, hypersensitivity
- -CNS: paresis, meningitis, tabes dorsalis
- -COR: aortic valves, aortic aneurysm
How is syphilis tx?
“Syphilis is exquisitely sensitive to antibiotics.”
- -Pen G IM x 1 dose
- -if allergy: long course of doxy
What are other treponemal disease?
Yaws, Bejel and Pinta
What causes yaws? Properties? Tx?
T. pertenue in tropical areas
- -open skin sore transmission
- -children
- -no trans-placental trans
- -Primary lesions = mother yaw = raspberry
- -sensitive to Pen G
- -will cause false positive T. pallidum tests
What causes bejel? Properties? Tx?
T. pallidum ssp. “endemicum”
- -Syrian peds
- -Similar to yaws
- -No venereal trans
What causes pinta? Properties? Tx?
T. carateum in Central and S Amer
–flat, non-ulcerating skin lesions of hands, feed and scap that heal spontaneously –> depigmented area left behind
What are other, non-treponemal spirochete pathogens?
- -Borrelia spp.
- -Leptospira spp.
What causes lyme disease?
Borrelia burgdorferi which is visible in light microscopy; can only be cultured in chick embryo thus far
What is the reservoir and vector of lyme dz?
white footed mouse is reservoir
–Ixodes spp. ticks = vector
What is the pathogenesis of lyme dz?
Three stages:
- 3-14 days after bite: bulls-eye expanding erythema chronicum nigrans w/ fever, h/a, stiff neck and malaise
- various neuro and cardio sx; bilat facial nerve palsy
- arthritis; occur weeks to months after bite and may last years
Dx Lyme dz?
- -sx (e.g. bulls-eye rash)
- -ELISA for circulating Abs
Tx Lyme dz?
tetracycline; ampicillin for young kids
–PenG or ceftriaxone work, too
Leptospira pathogenesis and sx?
transmitted by rats, dogs and other animals; occ hazard for sewage workers, slaughter house, rat-infested areas
- -infected urine
- -ingestion or mucus membrane entry–> circulation–>end organs
- -biphasic w/ illness followed by remission followed by immunopathology
- -causes Weil’s dz (infectious jaundice), nephritis, meningitis
Leptospira dx?
culture or serological ID
Leptospira tx?
Penicillin; erythromycin and tetracycline
Is there a vaccine for Lyme? For Leptospira?
There was one for Lyme against outer surface protein A (OspA) that was given to those at high risk (e.g. foresters), but it is no longer available.
–There is no vaccine for Leptospira
How is syphilis transmitted?
3 ways:
- -genital contact
- -vertical transmission via placenta
- -very rare: blood transfusion (rare b/c cannot live in blood alone for very long time)
How do you dx syphilis?
- Microscopy with darkfield
- Non-Specific Serology
- -use cardiolipin to react with serum samples of pts w/ suspected syphilis case (e.g. VDRL=viral dz research lab; RPR=rapid plasma reagin) - Specific Serology
- -more expensive, more specific (i.e. fewer false positives)
- -immunofluorescence (FTA-ABS) or micro-hemagglutination with Abs in the pt’s serum
- -ELISA–USED AT DHMC
- -TPI T. palldium immobilization; important if false poz suspected
- -will remain positive even after tx (vs. non-specific tests)
What causes relapsing fever?
Borrelia recurrentis (epidemic, not in U.S., louse transmission) An Borrelia hernsii (endemic in W U.S. ticks-->rodents-->ticks-->humans)
What is the clinical course of relapsing fever?
4-5 days fever, 7-10 afeb
–wash, rinse repeat 3-10 times
How do you dx relapsing fever?
- -blood smear
- -bioassay (inject into mouse)
How do you tx relapsing fever?
-tetracycline derivatives
