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Rickettsia

Rickettsia. By. Dr. Emad AbdElhameed Morad. Lecturer of Medical Microbiology and Immunology. Morphology. Short bacilli. Difficult to stain by Gram . Best stained by Giemsa stain. Rickettsia by Giemsa stain. Cultural characters.

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Rickettsia

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  1. Rickettsia By Dr. Emad AbdElhameed Morad Lecturer of Medical Microbiology and Immunology

  2. Morphology Short bacilli. Difficult to stain by Gram. Best stained by Giemsa stain. Rickettsia by Giemsa stain

  3. Cultural characters They are obligatory intracellular parasites because they can notmake its own ATP. Thus, like viruses they could not growon artificial media. However, they grow on: Tissue culture. Embryonated eggs. Laboratory animals.

  4. Antigenic characters Rickettsia share antigens with certain strains of proteus (OX-K, OX-2, OX-19). So, these proteus strains could be used in serodiagnosis of rickettsial diseases. Weil-Felix reaction

  5. Species

  6. Pathogenesis All rickettsia are transmitted to man by the bite of arthropod vector. After entering the body, rickettsia will invade: Endothelial lining of blood vesselsleading to rash.

  7. Epidemic typhus

  8. Caused by Rickettsia prowazeki. Transmitted from man to man by louse. Occurs during wars. The patient suffers from: Fever Headache (affection of brain blood vessels) Rash Gangrene of hands and feet (vascular occlusion)

  9. Epidemic typhus (war & louse & rash)

  10. Endemic typhus Rickettsia typhi Rats Rat flea Man Resemble epidemic typhus BUT Lower mortality Milder

  11. Rocky mountain spotted fever

  12. The name refers to the region in which the disease was first found. Caused by Rickettsia rickettsii. Transmitted from dogs & rodentsto man by ticks. The patient suffers from: Fever Headache Rash affecting extremities Conjunctival redness

  13. Rocky mountain spotted fever

  14. Laboratory diagnosis of rickettsial diseases

  15. Specimen: Blood & skin biopsy. Culture: Tissue culture or chick embryo. Direct detection in clinical specimen: PCR Immunological methods Serological diagnosis: Detection of rising titerof anti-rickettsial antibodies by ELISA. Weil-Felix reaction: no longer used because it is non specific.

  16. Treatment • Tetracycline: the drug of choice. • Chloramphenicol: the second choice. Prevention • Epidemic typhus: anti-louse measures. • Endemic typhus:rat proof building. • Rocky mountain spotted fever:tick repellents.

  17. Coxiella burnetii

  18. Coxiella is similar to rickettsia but differs in: More resistant to drying and disinfectants. Survive for months in dry animal discharges due to endospore formation. Not transmitted by arthropods. However, it is transmitted from cattle, sheep and goats to man causing Q fever

  19. Pathogenesis Q fever is a zoonotic disease. Coxiella passes in the milk and excreta of cattle, sheep and goats. Man is infected by: Inhalation of dust contaminated with the excreta of infected animals. Consumption of unpasteurized milk. People at risk of infection are: farmers, butchers, veterinarians and laboratory personnel.

  20. Q fever IP: 2 weeks. Acute Q fever: Fever + influenza like symptoms Pneumonia in 50 % of the cases Granuloma in the LIVER, spleen and bone marrow Chronic Q fever: Life threatening endocarditis Laboratory diagnosis: serological for rising antibody titer

  21. Q fever

  22. Treatment • Doxycycline Prevention • Proper pasteurization of milk up to 60 degree. • Formalin killed vaccine is available for people at risk.

  23. Best Regards

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