Yersinia pestis presentation

history, morphology, classification, laboratory diagnosis and treatment

1. Yersinia pestis By : S.Gowtham , III – B.Sc Microbiology.

2. Content 2 Introduction Morphology Classification Life cycle Pathogenesis Treatment Control

3. Introduction Yersinia pestis , the cause of bubonic and pneumonic plague in humans, persists in populations of wild rodents in many parts of the world and is transmitted primarily by the bites of infected fleas. Infection by the bacterium Yersinia pestis is most often associated with the infamous Black Death of the middle ages, a pandemic that cost Europe a third of its population in the 14 th and 15 th centuries. Plague is a seasonal disease with most reported human cases occurring between March and October. 3

4. 4 Pandemic 1 – Plague of Justinian (542-750 AD) Severely weakened Eastern Roman Empire. 25-50 million deaths; 25-30% of Empire. 5000 deaths per day in Constantinople. Pandemic 2 – Black Death (1346-1353 AD) Devastated Europe. 50 million deaths. 60% of European population. Pandemic 3 – China/Worldwide (1855-1959 AD) Mostly in China, India and Indonesia. Spread globally in 1894 from Hong Kong. About 15 million deaths. Pandemics

5. 5 Gram negative rod with striking bipolar staining with special stains. Non motile. Grow as facultative anaerobe on many bacteriologic media. Growth is more rapid in media containing blood or tissue fluids are fastest at 30’C. Virulent, wild-type Yersinia pestis carries V and W antigens, Which are encoded by genes on plasmids. A 72-kb plasmid is essential for virulence. A virulent strains lack the plasmid. Some stable avirulent strains have served as live vaccines. Among several exotoxins produced, one is lethal for mice in amounts of 1 micro gram. This homogenous protein produces beta-adrenergic blockage and is cardio toxic in animals. Morphology

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7. 7 ADD A FOOTER Domain : Bacteria Kingdom : Prokaryotae Phylum : Proteobacteria Class : Gammaproteobacteria Order : Enterobacteriales Family : Enterobacteriaceae Genus :   Yersinia Species :   pestis Classification

8. 8 After ingested by a flea from a lymphatic's, Yersinia pestis multiplies in the flea gut and expresses a coagulase that clots ingested blood, occluding the proventriculus , rendering the flea “blocked”, that is, unable to move food from its esophagus to its midgut . Thus the flea repeatedly attempted to feed, and because it is unable to ingest blood, it regurgitates the newly infected blood back into the bloodstream of the mammal on which it is feeding, therefore transferring the microorganism from the flea to the mammal. Approximately 25,000 to 1,00,000 Yersinia pestis organisms are inoculated into the skin of the mammal host during this process. The bacteria migrate through cutaneous lymphatic's to regional lymph nodes where they are phagocytosed but resist destruction. The rapidly multiply, causing destruction and necrosis of lymph node architecture with subsequent bacterimia , septicemia and endotoxemia that can lead quickly to shock, disseminated intravascular coagulation and coma. Life cycle

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10. Pathogenesis 10 The pathogens rapidly reach the lymphatic's and an intense hemorrhagic inflammation develops in the enlarged lymph nodes, may undergo necrosis and become fluctuant. Often reach bloodstream and become hemorrhagic and necrotic lesions may develop in all organs. Meningitis, pneumonia and serosanguineous pleupericarditis are prominent features. Primary pneumonic plague results from inhalation of infective drops, with hemorrhagic consolidation, sepsis death.

11. 11 After an IP of 2- days, there is high fever and painful lymphodenopathy in commonly with greatly enlarged, tender modes in the groin or axilla . Vomiting and diarrhea may develop with early steps. Later DIC leads to hypotension, altered mental status, renal and cardiac failure. Terminally signs of pneumonia and meningitis can appear. Yersinia pestis multiplies intravascularly and can be seen in blood smears. Clinical findings

12. 12 Plague should be suspected in febrile patients who have been exposed to rodents in known endemic areas. Rapid recognition and lab confirmation of disease are essential in order to institute life saving therapy. Specimens Blood for culture Aspirates of enlarged lymph nodes for smear and culture. Acute and convalescent sera for antibody levels. Sputum for culture. CSF for smear and culture. Smears Examined after staining with Giemsa’s stain and with specific immunofluorescent stains. With Wayson’s stain, may show striking bipolar appearance. CSF and sputum smears should also be stained. Laboratory Diagnosis

13. 13 Culture On BA, MCA plate and in infusion broth. Growth on solid media may be slow but blood culture are often positive in 24 hrs. Tentatively identified by biochemical reactions. Definite identification is best done by immunofluorescense . All cultures are highly infectious and must be handled with extreme caution. Serology In previously unvaccinated, a convalescent serum antibody titer of 1:16 of greater is presumptive evidence of infection. A titer rise in two sequential specimens confirms the serologic diagnosis. Laboratory Diagnosis

14. 14 Amino glycosides: Streptomycin and Gentamicin S treptomycin is the most effective antibiotic against Yersinia pestis and the drug of choice for treatment of plague, particularly the pneumonic form. Chloramphenicol Chloramphenicol is a suitable alternative to amino glycosides in the treatment of bubonic or septicemic plague and is the drug of choice for treatment of patients with Yersinia pestis invasion of tissue spaces into which other drugs pass poorly or not at all. Tetracycline's This group of antibiotics is bacteriostatic but effective in the primary treatment of patients with uncomplicated plague. Sulfonamides Sulfonamides have been used extensively in plague treatment and prevention. Fluoroquinolones Fluoroquinolones , such as ciprofloxacin, have been shown to have good effect against Yersinia pestis in both in vitro and animal studies. Treatment

15. 15 Vaccination Worldwide , live attenuated and formalin-killed Yersinia pestis vaccines are variously available for human use. The vaccines are variably immunogenic and moderately to highly reactogenic . They do not protect against primary pneumonic plague. Treatment

16. 16 Prevention Preventive measures include informing people when zoonotic plague is present in their environment. Advising them to take precautions against flea bites and not to handle animal carcasses. Generally people should be advised to avoid direct contact with infected body fluids and tissues. When handling potentially infected patients and collecting specimens, standard precautions should apply. Control

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