55. Spirochetes Flashcards
bug that causes syphilis?
treponema pallidum
treponema pallidum general characteristics?
- Spirochetes – thin, spiral bacteria
- hard to cx
- dx w/serology
- humans as primary host
- grows slowly, only in human tx
treponema pallidum epi/vector?
- transmission by sexual contact
- incidence decreased in last decade
- assoc w/risk of HIV infection
treponema pallidum pathogenesis?
- adherent outer membrane proteins
- produc of hyaluronidase to facil perivascular infiltration (damage really related to vascular damage!)
- fibronectin coat prevents phagocytosis
- pt’s immune response leads to tissue damage
treponema pallidum disease?
Syphilis
- dev of a painless ulcer (chancre)
- flu-like illness w/lymphadenopathy and later a disseminated rash (palms and soles of feet)
Late syphilis. Chronic inflammation w/granulomatous lesions: CNS (neurosyphilis) (causes dementia-like sxs, so test dementia pts w/RPR) or blood vessels (cardiovascular syphilis)
Congenital: fetal disease w/latent manifestations or multiorgan malformations
treponema pallidum dx?
- Microscopy: darkfield w/fresh specimen; direct fluorescent Ab test
- Serology – diagnostic test of choice: Nontreponemal tests (VDRL, RPR) (standard, often false positive in pts w/lupus or HIV…if negative then R/O sypthilis) and Treponemal tests (FTA-ABS) (specific for syphilis so use for f/u a positive RPR)
treponema pallidum tx/prevention?
- may undergo spontaneous cure or progress
- PCN is the drug of choice
- doxycycline = alternative for early syphilis
- ceftriaxone = for late syphilis (ie neurosyphilis because gets into CNS better)
borrelia burgdorferi general characteristics?
- Spirochetes – thin, spiral bacteria
- hard to cx
- dx w/serology
- zoonotic
- GN but stain poorly
- commonly seen w/Giemsa stain
- microaerophilic w/complex nutritional req’s – so hard to grow
borrelia burgdorferi epi/vector?
- transmitted by hard ticks: primarily Ixodes species
- acquired by ticks in first feeding phase (larva); transmitted to humans in subsequent feedings by nymph (usu) and adults
- transmission requires prolonged feeding (>24 hours), pt doesn’t remember seeing the tick because it’s super small
- reservoirs are white-footed mouse (human disease) and white-tailed deer
- most common vector-borne disease in USA
borrelia burgdorferi disesae?
Lyme Disease
1. early localized erythema migrans; accompanied by fever, malaise, headache, and muscle aches
2. early disseminated 3-5 weeks after tick bite; multiple erythematous lesions w/myalgias, arthralgia, headache, fatigue, cranial nerve palsies (CN VII), meningitis, and cardiac dysfunction (conduction abnormalities like a heart block)
3. late disseminated weeks to months after tick bite; mostly arthritis
No evidence for infectious chronic lyme disease (so don’t treat w/Abx w/chronic sxs)
borrelia burgdorferi diagnosis?
- microscopy and cx not useful
- erythema migrans: rash makes Dx! (early on, serology often negative at this point)
- serology is test of choice for disseminated disease but false-positive results caused by cross-reactions and high level of background positives, this is: ELISA must be confirmed w/Western Blot test
borrelia burgdorferi treatment/prevention?
- doxycycline for early localized or disseminated disease
- amoxicillin or cefuroxime when doxy is contraindicated
- ceftriaxone for disseminated disease (because gets into CSF better to treat things like Bell’s palsy)
leptospira general characteristics?
- Spirochetes – thin, spiral bacteria
- hard to cx
- dx w/serology
- zoonotic
- really long
- worldwide dist, more common outside the states
leptospira epi/vector?
- zoonosis: chronic renal infection of carrier animals that excrete in urine to env’t. Nonhuman mammals are hosts w/no vector
- humans contract disease through direct contact w/cuts or abrasions in skin
- activity related: rice paddies, triathlons in infected water, open sewers in favelas in developing countries (super common there)
- EXPOSURE TO WATER THAT HAS BEEN CONTAMINATED BY ANIMALS
leptospira disease?
Leptospirosis
- asymptomatic infection (90%)
- febrile illness
- biphasic, severe disease: septicemic from direct damage (5-7 days, fevers, myalgias, vomiting, diarrhea, conjunctival suffusion) or immunologic from immunologic damage (4-30 days duration, hepatic failure w/jaundice and renal failure/Weil’s disease, cardiac disease, pulm hemorrhage, meningitis)
