Spirochetes Flashcards
what mediates motility of spirochetes?
spirochetes have coiled cell wall and are motile due to endoflagella (internal, in between outer and inner membrane)
“drill” into cells to invade
how are spirochetes best visualized?
dark-field microscopy or immunofluorescent stains (very tiny, skinny)
what are the 3 genera of spirochetes that cause human disease?
BLT:
Borrelia: Lyme’s (B. burgdorferi), relapsing fever (B. recurrentis)
Leptospira: leptospirosis (L. interrogans)
Treponema: syphilis (T. pallidum)
left untreated, diseases occur in stages
Lyme disease is due to infection by ______, transmitted by bites of small deer tick _____
Lyme disease is due to infection by Borrelia burgdorferi (spirochete), transmitted by bites of small deer tick lxodes
*note that nymphal stage is most aggressive portion of life cycle (May-July)
host vs reservoir vs vector
host: living animal or plant on/in which parasite lives
reservoir: organism in which parasite that is pathogenic for some other species lives and multiples without damaging its host
vector: organism that transmits a pathogen from one organism or source to another
where in the US is Lyme disease most common?
Northern Hemisphere (northeast US) - 10-50% ticks infected in East, only 2% in West
overall, Lyme disease most commonly reported vector-borne illness in US
*note that transmission requires tick attachment for 24+ hours
what antibiotic can be given as prophylaxis for Lyme disease from a tick bite?
doxycycline
what are the only known virulence factors of Borrelia burgdorferi (spirochete), and what is their function?
surface exposed lipoproteins OspA-F
allow attachment of B. burgdoferi to mammalian cell
what are the clinical stages of Lyme disease from Borrelia burgdorferi (spirochete) infection?
highly variable among patients - brief or chronic, localized or multiple systems
early infection stage 1: localized (days later) —> slowly expanding erythema migrans (EM) hot to touch and itchy/painful
early infection stage 2: disseminated (days-weeks) —> flu-like, then (weeks-months) —> musculoskeletal pain, bursae, neurological manifestations (Bell’s palsy)
late infection stage 3: persistent infection —> chronic nervous system and joint involvement (Lyme arthritis, esp. in knee)
ALL stages curable with antibiotics
how is Lyme’s disease (Borrelia burgdorferi, spirochete) diagnosed in presence and absence of EM (erythema migrans), respectively?
presence of EM —> clinical presentation + exposure in endemic area enough for antibiotic treatment without serology
absence of EM —> 2-test serological approach (EIA followed by 2nd EIA if positive or ambiguous)
*serological tests less effective early in disease
what is relapsing fever caused by? what is the difference between epidemic and endemic relapsing fever?
caused by Borrelia recurrentis (spirochete) - sudden onset of fever with chills which ends abruptly and relapses about a week later (severity/duration decrease with each relapse)
epidemic relapsing fever: louse-borne (only after crushing lice), usually during war/poverty/famine
endemic relapsing fever: tick-borne, rodents are reservoir, Western US
what disease does Leptospira interrogans (spirochete) cause? where does it come from?
leptospirosis: chronic renal infection of wild/domestic animals (dogs most common), human infection via direct/indirect contact (shedding of organism)
also viable in fresh (not salt) water for weeks
rapidly disseminates in bloodstream, wide variety in clinical presentation
what disease does Treponema pallidum (spirochete) cause?
syphilis: transmitted most often by sexual intercourse, but also through placenta/birth/kissing/blood transfusion
most infectious early in disease - primary and secondary lesions rich in spirochetes (highly infectious) on fingers, breasts, lips, oral cavity, genitals
can invade virtually any organ, including CNS
what organism causes syphilis, and what are the stages of disease?
caused by Treponema pallidum
primary: chancre (primary lesion) at inoculation site, heals spontaneously (30% cured without treatment)
secondary: disseminated, secondary lesions anywhere on body
latent: serologic tests positive but no clinical manifestations (blood remains infectious), 30% stay here untreated
tertiary (late): slow progressing inflammatory disease affecting any organ —> neurosyphilis, cardiovascular syphilis, gummatous syphilis (rare)
what do neurosyphilis, cardiovascular syphilis, and gummatous syphilis, complications of tertiary (late) syphilis, cause, respectively?
neurosyphilis: symptoms range from subacute meningitis to mental deterioration
cardiovascular syphilis: necrosis of aorta
gummatous syphilis (rare): painless skin lesions and deep/gnawing pain bone lesions
*note congenital syphilis may result in loss of fetus, stillborn, or developmental abnormalities
[remember that syphilis is caused by Treponema pallidum]
