Zrzut_ekranu_2011-02-12_(godz._17.35.32).png Yersinia pestis



Yersinia pestis is the best-known human pathogens within the genus Yersinia. Y. pestis is a highly virulent pathogen that causes the highly fatal systemic disease known as plague.

Biology
  • Y.pestis is gram-negative, facultatively anaerobic rods (pic.1)
  • fermenter, oxidase negative
  • lipopolysaccharide consists of somatic O polysaccharide, core polysaccharide (common antigen), and lipid A (endotoxin)
  • is covered with a protein capsule



Virulence  Picture 1. Yersinia pestis
  • resist killing (the type III secretion system mediates this properity)
  • has two plasmids that encode virulence genes: fraction 1 gene (codes for an antiphagocytic protein capsule), and plasminogen activator (Pla) protease gene (degrades complement components C3b and C5a, preventing opsonization and phagocytic migration;
  • show serum resistance



DiseaseScreen_shot_2011-02-13_at_20.24.38.png







Picture 2. Symptoms of bubonic plague.
Epidemiology
Screen_shot_2011-02-13_at_19.48.35.png

  • Y.pestis is a zoonotic infection
  • humans are accidential host
  • natural reservoirs include rats (pic.3) squirrels, rabbits, and domestic animals
  • disease is spread by flea bites or direct contact with infected tissues or person to person by inhalation of infectious aerosols from a patient with pulmonary disease













Picture 3. Rat, natural reservoir of plague.