Plague, Tularemia, Brucellosis Flashcards
what is the cause of plague?
Yersinia pestis (Y. pestis)
shape and gram stain of Y. pestis?
- large rod-shaped or coccobacillus
- gram negative
Y. pestis metabolism
- aerobe or facultative aerobe
- non-lactose fermenter
how is Y. pestis transmitted?
1 - flea to mammal (bubonic). Flea regurgitates in bite site, organisms enter lympathics and cause regional adenitis (bubo).
2 - mammal to mammal (pneumonic). respiratory droplets.
urban vs. rural plague
urban was through rats and accounted for major human outbreaks. rural is sporadic and in developing countries mostly. caused by flea bite, contact with indigenous rodent, or domestic pet.
Y. pestis extracellular pathogens
- anti-phagocytic capsule (F1)
- V and W antigens for survival in macrophage
- anti-phagocytic properties dependent on human 37C temperature
Y. pestis intracellular properties
- persistence within mammalian monocytes
Y. pestis toxins
- LPS endotoxin
- exotoxin
clinical features of bubonic plague
- fever
- malaise
- painful lymphadenopathy
clinical features of pneumonic plague
- fever
- cough
- shortness of breath
clinical features of septicemic plague
- no bubo
- dissemination via blood
plague complications
- DIC
- skin hemorrhages (black death)
- meningitis
plague immunity?
- antibodies develop over time
- military vaccine used in Vietnam against bubonic plague
plague diagnosis
- bubo aspirate: gram and culture positive confirmed by fluorescent antibody microscopy
- blood culture: positive
- serology: rise in antibody to F1 capsule with hemagglutination test
plague treatment
- 10 days streptomycin or tetracycline or chloramphenicol
what causes Tularemia?
F. tularensis
shape and grain stain of F. tularensis
small unencapsulated pleomorphic gram negative
metabolism of F. tularensis
- aerobic slow grower
- requires cysteine, glucose or thioglycolate
F. tularensis infectious dose?
5-10 organisms
F. tularensis routes of human infection
- rabbit: contact
- arthropod: ticks, deer flies
- infected tissues, animal bite, etc.
F. tularensis pathogenesis
- tick bite
- skin lesion
- enter lymphatics, local lymphadenopathy
- bacteremia follows, granuloma formation (spleen and liver)
- intracellular survival in monocytes
- endotoxin has role in symptoms
F. tularensis clinical features
- similar to plague
- abrupt onset fever, chills, malaise
- syndromes (see other card)
F. tularensis specific syndromes
- ulceroglandular: most common, skin ulcer and painful adenopathy
- typhoidal (bacteremia)
- pneumonia
F. tularensis diagnosis
- fluorescent antibody staining of node biopsy
- serologic: 4X titer increase or single titer greater than 1:160 at 2 weeks
F. tularensis treatment
- either streptomycin 7-10 days or tetracycline 14 days
Brucella gram stain and morphology
- pleomorphic
- gram negative
brucella metabolism
- slow grower
- requires CO2 for optimal growth
Brucella species
- B. abortus (cattle), milk or meat
- B. suis (swine), meat, airborne, slaughterhouse
- B. melitensis (goat, sheep), milk, cheese
- B. canis (dog), urine
brucella pathogenesis
- infectious abortion in huffed animals
- infects reticuloendothelial system in humans
- neutrophils - multiply in monocytes - granulomas in liver, kidney, spleen, bone marrow
brucella clinical features
- systemic and non-focal (FUO)
- fever, chills, myalgias, headache, arthralgias
- intracellular survival prolongs initial symptoms
brucella complications
- osteomyelitis
- endocarditis
brucella diagnosis
- occupational history
- blood culture
- serologic: 4X titer increase
- bone marrow biopsy in difficult FUO cases
brucella treatment
doxycycline and rifampin for 6 weeks
prevention of brucella
- vaccination of calves
- herd testing
- physical barriers
