2. Plague, Tularemia & Brucellosis Flashcards
(40 cards)
What microbe causes plague?
Yersinia pestis
What are the physical and biochemical characteristics of Y. pestis?
- Enterobacteriaceae family
- Large, bipolar (safety pin) staining, Gm(-), pleomorphic rod
- Facultative aerobe (notes say “aerobic or facultative aerobic” slides just say “facultative”)
- Glucose fermenter
- Non-Lactose fermenting
- non-motile
- Catalase +
- Oxidase -
What do you stain with do see bipolar staining?
Giemsa or Wayson stain
What is the epidemiology of plague?
zoonotic transmission --humans accidental hosts can be either: -arthropod --> mammal (bubonic) -mammal --> mammal (pneumonic) *pneumonic can be 1° from inhalation or 2° to bubonic plague that causes bacteremia
What is the geographic distribution of plague in the U.S.?
mostly southwestern U.S.
Animal resevoirs of Y. pestis?
mostly rodents; In U.S. prairie dogs, squirrels, weasels, skunks, woodrat, cats
Arthropod vectors of Y. pestis?
rat flea
What is the epidem. of urban plague?
epizootic (animal epidem) in urban black rats; as they die off their fleas –> humans; first bubonic then pneumonic
What is the epidem. of rural plague?
incidental contact with wild rodents or their fleas;
- -SW u.s. (10 cases/yr), indian, s. amer, s. afr, s. russia
- -flea bite, hand contact w/ wild animal, pet
Is Y. pestis and extra- or intra-cellular pathogen?
Can be both. Intracellular in monocytes
What virulence factors does Y. pestis employ?
- F1 antigen = anti-phag capsule (only active at human body temp)
- Endotoxin (from LPS)
- V & W antigens –> allow intracellular growth in monocytes
- exotoxin
What is the role of toxins in plague pathogenesis?
Both endotoxin and exotoxins
–endotoxin leads to DIC which causes the cutaneous hemorrhages and necrosis = “black” death
How do you dx plague?
- smear (and culture per Levinson) from blood, bubo pus or sputum
- 4X rise in Ab titer for F1 (caps. Ag)
- fluorescent Ab staining against F1
How is plague prevented?
- -72 quarantine for Positive Pts.
- -flea control
- -rodent control (esp at ports)
- -inactivated vaccine (used in Vietnam; no longer available in U.S.)
- -chemoprophylaxis for exposed w/ tetracycline
How is plague tx’ed?
10 days of tetracycline and/or streptomycin (Levinson says combo is tx of choice); chloramphenicol works, too
- -no significant resistance
- -surgical drainage not needed
What is the difference between bubonic and pneumonic plague?
bubonic:
–bite skin –> local lymph nodes
What are the different clinical presentations of plague?
- bubonic: fever, malaise & painful lymphadenopathy
- pneumonic: fever, cough & SOB
- septicemic: DIC, skin hemorrhages, plague meningitis
If a pt survives plague, will pt have immunity?
yes
What is the causative agent of tularemia?
Francisella tularensis
What is the epidemiology of tularemia?
transmitted from infected animals or arthropods to humans; ~200 cases/yr in the 90s; e.g. muskrat trappers in VT
What are the animal resevoirs of tularemia?
rabbits (handling furs or eating under-cooked), deer
- -other rodents
- -cat bites
- -dog aerosolized when shaking off water in Martha’s Vineyard
- > 100 different species of wild animals
Which are the arthropod vectors of tularemia?
ticks (DERMAcentor variabilis) and deer flies
Which individuals are at high risk for contracting tularemia?
–lab workers, trappers, vets
Describe the pathogenesis of tularemia.
- infection via: handling, tick bite, ingestion or inhalation
- skin lesions –> local lymphatics
- lymphadenopathy
- bacteremia
- granuloma formation in reticuloendothelium (spleen, liver)
* *Survives intracellularly in Monocytes/Macrophages
* *Endotoxin –> systemic symptoms
