1. Yersinia pestis: The agent of Plague
Professor
Alaa Al-Charrakh
Babylon University

2. Plague – infection of wild rodents, transmitted interspecies occasionally from rodents to humans, by bites of fleas.
Outbreak: seen in India, Africa, North/South of America and S.E. Asia.
Black death – pandemic that killed 2/3 of Europeans (~75 millions people) in late 1340s.

3. Plague is caused byYersinia pestis G-ve rod; exhibits striking bipolar staining with Wright-Giemsa stain; non-motile.

4. Pathogenesis 1
Polymorphs→ killed
Monocytes→ survive
By coagulase

5. Clinical findings
After 2-7 days of incubation, patients presented with high fever, painful lymphadenopathy, enlarged, tender nodes (buboes) in groin and axillae. Sometimes with vomiting and diarrhoea.
Later disseminated intravascular coagulation (DIC) leads to hypotension, altered mental status, renal & cardiac failures.

6. As a result, the patient develops a severe bacterial pneumonia, exhaling large numbers of viable organisms into the air during coughing fits. Up to 90 percent of untreated patients will die representing a highly contagious health hazard to nursing staff.

7. Diagnostic: important to recognize early, confirms with lab
Diagnostic: important to recognize early, confirms with lab. Specimens: taken from blood, aspirates of enlarged lymph nodes and sputum. Control: (1) streptomycin, alternatively tetracycline; (2) destruction of plague-infected rodents, (3) vaccine (formalin-killed) for travelers.