Micro: Borrelia & Leptospira Flashcards
What is the basic structure of spirochetes?
dual membrane w endoflagella in periplasmic space
no gram stain
What are the 3 basic spirochetes and their diseases?
treponema - syphilis, yaws, pinta
borrelia - lyme dz and relapsing fevers
leptospira - leptospirosis
What are the general characteristics of spirochete diseases?
cause widely disseminated, often chronic dz (predilection for CNS)
complex dzs often occur in stages
host immune response responsible for clinical manifestations
What is the epidemiology of lyme dz?
transmitted by Ixodes (hard) ticks
zoonosis that can infect domestic animals
What are the manifestations of lyme dz?
stage 1: erythema migrans and constitutional symptoms
stage 2: CNS (numbness, stiff neck, facial muscle paralysis) heart (heart block)
stage 3: joint swelling and pain
How is lyme dz diagnosed?
B. burgdorferi rarely recovered from clinical specimens
pts w erythema migrans often seronegative
other forms require serologic confirmation (ELISA plus immunoblot)
PCR on joint fluid as adjunct
How is lyme dz treated?
orally - doxy, amoxil
IV ceftriaxone for severe refractory
What is post lyme dz syndrome?
pts remain symptomatic after appropriate therapy
persistent inf, autoimmune rxn, psychological factors?
What is the prophylaxis for lyme dz?
antibiotic prophylaxis of tick bites not cost-effective
no vaccine available
minimize risk
How is borrelia burgdorferi maintained in nature?
2 year enzootic life cycle involving ticks and small rodents
What is the epidemiology of relapsing fevers?
all arthropod-borne (ticks or lice)
EPIDEMIC caused by B. recurrentis on human body louse, severe and can be lethal, inf from crushing louse into wound itching not bite itself
ENDEMIC from soft ticks, animal reservoirs, milder dz
What is a key feature in the pathogenesis of relapsing fever?
antigenic variation
What is the clinical presentation of relapsing fevers?
acute onset, flu-like symptoms
conjunctival suffusion, petechiae, hepatosplenomegaly
CNS in 1/3 of pts
death from myocarditis, shock, hepatic failure (40% of untreated)
How is relapsing fever diagnosed?
demo organisms in peripheral blood smear
serology not helpful
What is the treatment of relapsing fever?
tetracycline, erythromycin, or penicillin
What is the Jarisch-Herxheimer rxn?
due to cytokine cascade following release of spirochetal contents
sudden high fever, flushing, vasomotor instability, tachy
can be fatal
passive admin of anti-TNF alpha may diminish
What is the epidemiology of leptospirosis?
animal reservoirs, transmitted by organisms excreted in urine
risk derived from occupational, military, recreational exposure
What is the clinical presentation of leptospirosis?
biphasic illness
initial phase = leptospiremic = flu-like
second = immune - caused by IgM immune complexes
both phases can present in 2 forms
anicteric - aseptic meningitis, uveitis, rash, conjunctival suffusion
icteric - hepatic and renal dysfxn (ATN), myocarditis, vascular collapse (Weil’s dz)
How is leptospirosis diagnosed?
culture from blood during first 7-10 days, after only urine, special culture media
serology - 4 fold rise in agglutination titer or titer >1:100
What is the treatment and prevention of leptospirosis?
oral doxy can prevent in endemic areas
IV amp, pen, ceftriaxone, tetracycline for tx
supportive therapy
vaccination of livestock/pets, rat control
