Spirochetes Flashcards
Treponema bacteriology
Treponema pallidum -> syphilis
Too thin for Gram stain!
- 5-15 microns x 2 microns (less than resolving power of light)
- > darkfield, electron, fluorescent or silver stain
- structure similar to Gram-negative
Cannot grow in culture
Very sensitive to heat, drying, soap, etc
- survive in blood 24 h (no risk from blood banks)
- survive in tissue days
- survive in rich media, anaerobic
- can store at -80C -> revive
- perpetuate in lab within rabbit testicles?
Overview of spirochetes
Long, flexible
Internal flagellum aka axial filament
- between cytoplasmic and outer membrane
- spiral -> hooked to both ends -> motility
Gram negative-like structure
Binary fission
Treponema -> syphilis, yaws, pinta, non-pathogens
Borrelia -> Lyme, relapsing fever
Leptospira -> leptospirosis
Treponema transmission
Usually direct contact of genitalia or mucous
- not in late stages of disease
Mother -> infant -> stillbirth, abortion, congenital secondary
- preventable by prenatal tx
Blood -> fresh transfusion, needlestick
Treponema pathogenesis
Incubation = 2-6 wks - replication at primary and secondary sites
Primary lesion = chancre
- 1-4 wks incubation -> heals spontaneously in 1-5 wks
- genital + focal lymphadenopathy
Secondary = disseminated
- 2-20 wks post-primary
-> generalized papular rash, lesions (flanks, hands, feet)
-> arthritis, renal, etc
- highly infectious lesions
Tertiary -> CNS, aortic valve, penetrating ulcers
- rubbery “gumma”
- hypersensitivity, not organism
Syphilis diagnosis
Clinical exposure, history
Old test: “Wasserman’s antibody” reacts with cardiolipin/phosphatidylglycerol -> fixation
- antibody? may be to T pallidum or host tissue released
Microscopy - darkfield of lesion exudate - may be sufficient
Non-specific - sensitive, performed first -> confirm with specific
VDRL - flocculation/clumping on slide with cardiolipin
Rapid plasma reagent (RPR)
Specific:
FTA-ABS = fluorescent Trep Ab - absorption
(absorb non-specific with non-pathogenic Treponema)
Micro-hemagglutinin - vs RBCs coated with Trep antigen
ELISA - most common at DHMC
TPI - T pallidum immobilization - antibody + complement -> cidal
- difficult, only reference labs, use for suspected false positive
False positives: VDRL, mononucleosis, malaria, etc
No PCR - don’t have primers, not as sensitive
Syphilis treatment
Very sensitive to penicillin - no resistance!
- duration depends on stage, must eliminate all
- alternatives: erythromycin, tetracycline
No vaccine (can't culture to study) - genomics -> target molecules?
Other Treponema
Treponema pallidum = syphilis
- subspecies endemicum -> bejel - similar to yaws, Syrian kids
T pertenue -> yaws (lesion looks like raspberry)
- tropical, only through open sores (not venereal, transplacental)
- resembles pallidum, test positive
- sensitive to penicillin
T carateum -> pinta aka carate
- Central and South America
- flat, non-ulcerating lesions of hands, feet, scalp -> depigmented
- senstive to penicillin
Some non-pathogenic Treponema in GI, genitals, etc
Relapsing fever epidemiology
Borrelia hernsii, recurrentis
- thicker than Treponema -> visible under light microscopy
- grow in chick embryo
Hernsii - endemic in western US rodents -> ticks -> humans
Recurrentis - epidemic - human -> lice -> humans
Relapsing fever clinical
Relapsing fever: 3-10 cycles
- 4-5 d fever -> 7-10 d afebrile
- due to mutation of antigens (linear plasmid)
Dx: clinical + observation in blood (Wright’s stain or darkfield)
Tx: tetracycline (penicillin or erythromycin for pregnant and kids)
Lyme disease bacteriology
Borrelia burgdorferi
- 7 linear, 2 circular plasmids
- does not require/use Fe - manganese metaloenzymes
Endemic to eastern US, midwest, NW
- white-footed mouse -> deer tick -> 8000 cases/yr
- transmitted by nymph, adult in late spring and summer
Lyme disease clinical
First stage: 3-14 d -> expanding erythema -> fever, stiff neck, h/a
Second: neuro, cardiac
Third: migrating arthritis - months-> years
- chronic arthritis if untreated or specific HLA (autoimmune?)
Dx: difficult to isolate organism
- rash + ELISA
Tx: tetracycline, ampicillin for kids
Vaccine: OspA membrane protein, effective
- cross-reactive -> arthritis -> lawsuits -> discontinued
Leptospira
Uncommon: rats, dogs -> urine (sewage workers, slaughterhouse)
Skin, aerosol -> bacteremia -> kidney, liver, meninges, conjunctiva
- myalgia, h/a, photophobia, fever
- Weil’s disease - specific serovar -> renal, hepatic -> 25% fatal
Dx: culture, serology
Tx: penicillin, erythromycin, tetracycline
- no vaccine
