Understanding Yersinia Pestis: Plague, Transmission, and Prevention

1. Yersinia Pestis

2. Yersinia • Y. pestis • Y. pseudoctuberculosis • Y. entercolitica

3. Species of Yersinia Bubonic Y pestis Plague Septicemic Pneumonic Food / water born diseases Y pseudotuberculosis 6 serotypes Y enterocolitica 27 serotypes

4. Yersinia pestis • Discovered by yersin and Kitasato • Short plump ovoid gram negative bacillus. • In Giemsa stained smears it shows bipolar staining (safety pin appearance). • It is capsulated, nonmotile.

5. Cultural characters • Aerobic and facultative anaerobic • Optimum temperature for growth is 27°C • Nutrient agar: transparent colonies • Blood agar: dark brown colonies due to absorption of hemin pigments

6. Ghee broth • Y.pestis when grown in a flask with oil or ghee floated on top, • a characteristic growth occurs which hangs down from under surface of ghee, resembling stalactites (stalactite growth)

7. Virulence factors • Fraction-I or F-I: Envelope protein which inhibits phagocytosis. • V and W proteins also inhibit phagocytosis. • Plague toxin: This is an endotoxin

8. Historical Impacts • The first plague was in 542 B.C. and lasted almost 60 years. • The second and most severe pandemic was in the 14th century, also known as the Black Death. • The final and most recent pandemic occurred in 1894.

9. Transmission of the Plague • Plague is a zoonotic disease • Fleas found on rodents( xenopsiella cheopis) carry disease • Man to man transmission is through the droplets from coughing

10. How man acquire Plague ?

11. How man acquire Plague ? Squirrel Rat Sylvatic plague Urban plague Flea Flea Infected flea bite human beings Spread via blood (Septicemic) Bubonic Plague Pneumonia & Meningitis Inhalation by other humans Pneumonic Plague

12. Diseases caused by Yersinia Pestis • Bubonic plague: based on the lymphatic system. • Septicemic plague: Centers in the bloodstream. • Pneumonic Plague: Centers in the lungs.

13. Plague: Clinical Manifestations Bubonic Pneumonic Septicemic Cervical bubo Gangrene Ecchymosis

14. Clinical feautres • Bubonic Plague • Constitutional symptoms • Lymphadenopathy • “bubo”: inguinal lymphnodes enlarged • May suppurate and drain • Septicemic Plague • Same terminal event of bubonic plague • Massive involvement of blood vessels leads to hemorrhages in skin and mucosa: BLACK DEATH

15. Primary pneumonic plague Organisms inhaled Lobular or lobar pneumonia Pulmonary necrosis Bacteremia Multiorgan seeding, failure Sepsis • Highly infectious form of plague

16. Laboratory diagnosis • Samples - blood, sputum, aspirated bubo fluid, splenic tissue on postmortem • Microscopy– Gram stain and Methylene blue stain: bipolar staining bacilli

17. Laboratory diagnosis • Culture – Blood agar, Ghee broth • Animal inoculation: Guinea pigs and rats injected subcutaneously with bubo fluid. Animals die within 2-5 days. • Antigen detection- F1 glycoprotein in bubo fluid and sputum • Serology –Antibodies to F1 glycoprotein appear at the end of 1st week of illness, and remain positive for several years • Rapid tests (PCR, DFA, etc) at reference labs

18. Identification features of Y pestis Ways of staining – bipolar staining Y pestis BA: Colonies are characteristically sticky CIN agar (cefsoludin irgasan- novobiocin) Gram stain

19. Treatment and Prevention • Tetracycline is drug of choice. • Vaccines: Two types • Killed vaccine: Haffkine’s vaccine. Virulent strain, Whole bacterial cell vaccine, 2000 million organisms/ml • Dosage: .05 ml S/C followed by 1ml after 7-14 days • Live vaccine: Avirulent strain of Y.pestis: Otten’s tjiwidej strain and Girard's 76 strain

20. Yersinia pseudotuberculosis & enterocolitica Facultative intracellular pathogens Pathogenesis Invade macrophages & epithelial cells Feces of wild and domestic animals Source of infection Ingestion of contaminated food or water Mode of transmission Y enterocolitica: pigs / dogs

21. Clinical manifestations Children < 5 yrs Acute enteritis with prolonged diarrhea Older children & adults Gastroenteritis Diarrhea Abdominal pain Terminal ileitis Mesenteric lymphadenitis LN enlarge Women 15-45 yrs Diarrhea with arthritis & erythema nodosum Liver, hemoglobinopathies, DM, Steroids Preexisting disease

22. Lab Diagnosis Y enterocolitica Specimens Stool samples Microscopy Gram negative coccobacilli – Gram stain Culture Non lactose fermenter – MAC agar Bulls eye colonies - CIN agar (cefsoludin – irgasan- novobiocin) Identification Biochemical tests

23. Tularemia • Francisella tularensis -Intracellular gram neg. coccobacillus. • It is also known as rabbit fever due to the fact that it may be transmitted to hunters and others who may have exposure to infected rabbits

24. Tularemia • Human infection may occur by handling or eating infected meat or drinking contaminated water Several forms: • Ulcers • Nodes • Pneumonic • usually ulceroglandular disease

25. Pasteurella multocida • Non motile, gram negative rod resembling yersinia. • Normal inhabitant og respiratory tract ofanimals like dogs cats cattle etc. • Human infections rare, but may cause wound sepsis following animal bites