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