Yersinia pestis

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Organism
- Gram negative bacillus, bipolar staining
- Enterobacteriaceae
- Virulence plasmids
- YOP, F1 capsular proteins - Pathogenesis
Epidemiology
- SW US
- Rat Fleas
- Urban - rats and humans
- sylvatic - wild rodents and human
- Y. Pestis multiples in foregut of flea
- Regurgitates into bite
Virulence factors
- F1 - antiphagocytic
- V + W Ag - antiphagocytic
- Intracellular survival in macrophages
- Three different virulence plasmids
Manifestations
- Site of bite: necrotic ulceration
- Drains to LN in macrophge
- Multiplication creates bubos; painful and tender
- Bacteremia: DIC, septic shock, systemic spread, necrotizing hemorrhagic pneumonia
Diagnosis/therapy
- Rapid diagnosis essential
- Gram smear of bubo aspirates
- Culture on blood agar
- 50-75% fatal without antibiotics
- Pneumonic form worse
- 10 days tetracycline