Rickettsia

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Rickettsia

  1. 1. RICKETTSIA ELIZABETH P. QUILES, M.D.,FPASMP DEPARTMENT OF MICROBIOLOGY OUR LADY OF FATIMA UNIVERSITY COLLEGE OF MEDICINE
  2. 2. RICKETTSIA <ul><li>CHARACTERISTICS: </li></ul><ul><li>Structurally similar to gram (-) bacilli </li></ul><ul><li>- DNA & RNA </li></ul><ul><li>- enzymes for Kreb’s cycle </li></ul><ul><li>- ribosomes for protein synthesis </li></ul><ul><li>- inhibited by antibiotics  Tetracycline & Chloramphenicol </li></ul>
  3. 3. <ul><li>Originally thought to be viruses because: </li></ul><ul><li>- small size </li></ul><ul><li>- stain poorly with gram stain </li></ul><ul><li>- grows only in cytoplasm of Eukaryotic cells </li></ul><ul><li>- obligate intracellular parasites EXCEPT Coxiella </li></ul>
  4. 4. <ul><li>Reservoirs – animals & arthropods </li></ul><ul><li>Humans are accidental hosts </li></ul><ul><li>Cell wall: </li></ul><ul><li>- peptidoglycan </li></ul><ul><li> - LPS – have weak endotoxic activity (absent in Ehrlichia) </li></ul><ul><li>Genera: </li></ul><ul><li>Rickettsia Rochalimaea </li></ul><ul><li>Coxiella Ehrlichia </li></ul><ul><li>Orientia </li></ul>
  5. 5. <ul><li>Stains weakly with gram stain  Giemsa or Gimenez stain </li></ul><ul><li>Easily destroyed by heat, drying & bactericidal agents EXCEPT Q fever  due to the formation of endospore-like structure by C. burnetti </li></ul>
  6. 6. <ul><li>Intracellular location: </li></ul><ul><li>typhus group – cytoplasm </li></ul><ul><li>spotted fever group – nucleus </li></ul><ul><li>Rochalimaea – surface of Eukaryotic cells </li></ul><ul><li>Coxiella & Ehrlichia – cytoplasmic vacuoles </li></ul>
  7. 7. <ul><li>PATHOLOGY </li></ul><ul><li>Multiply in endothelial cells of small blood vessels </li></ul><ul><li>Vasculitis </li></ul><ul><li>(skin – rashes;other organs – DIC & vascular occlusion) </li></ul><ul><li>Swollen & necrotic </li></ul><ul><li>Thrombosis of the vessels </li></ul>
  8. 8. <ul><li>VECTORS: </li></ul><ul><li>RMSF – Dermacentor andersoni </li></ul><ul><li>Rickettsialpox – Allodermanyssus sanguinus </li></ul><ul><li>Scrub typhus – trombiculid mites </li></ul><ul><li>Epidemic typhus – Pediculus humanus </li></ul>
  9. 9. <ul><li>Ehrlichiosis – Amblyomma americanus (lone star tick) </li></ul><ul><li>Trench fever – Pediculus humanus </li></ul><ul><li>Murine typhus – Xenopsylla cheopis & </li></ul><ul><li>Ctenophalides felis </li></ul>
  10. 10. RICKETTSIAL INFECTIONS <ul><li>Fever, headache, malaise, prostration, skin rash & hepatosplenomegaly </li></ul><ul><li>Classified into groups: </li></ul><ul><li>1. Typhus Group – Epidemic typhus, Murine typhus, Scrub typhus </li></ul><ul><li>2. Spotted Fever Group – RMSF, Rickettsialpox </li></ul><ul><li>3. Q Fever </li></ul><ul><li>4. Trench fever </li></ul><ul><li>5. Ehrlichiosis </li></ul>
  11. 11. TYPHUS GROUP <ul><li>Maculopapular rashes with the sparing of the palms & soles </li></ul>
  12. 12. EPIDEMIC TYPHUS (LOUSEBORNE TYPHUS) <ul><li>Etiology: R. prowazekii </li></ul><ul><li>severe systemic infection & prostration </li></ul><ul><li>more fatal </li></ul><ul><li>Brill-Zinsser Disease  recrudescent disease </li></ul>
  13. 13. ENDEMIC TYPHUS (MURINE TYPHUS) <ul><li>Etiology: R. typhi </li></ul><ul><li>similar features with Epidemic typhus but milder & rarely fatal except in the elderly </li></ul>
  14. 14. SCRUB TYPHUS <ul><li>Etiology: Orientia tsutsugamushi </li></ul><ul><li>resembles Epidemic typhus except for the ESCHAR </li></ul><ul><li>generalized lymphadenopathy & lymphocytosis </li></ul><ul><li>cardiac & cerebral involvement may be severe </li></ul>
  15. 15. SPOTTED FEVER GROUP <ul><li>Rash appear 1 st on the extremities with involvement of the palms & soles </li></ul>
  16. 16. RICKETTSIALPOX <ul><li>Etiology: R. akari </li></ul><ul><li>mild disease resembling Varicella </li></ul><ul><li>firm red macule at the bite site  deep-seated vesicle  eschar </li></ul>
  17. 17. Q FEVER (QUERY FEVER) <ul><li>Etiology: Coxiella burnetti </li></ul><ul><li>MOT: inhalation of dust containing the organism or aerosols </li></ul><ul><li>Excreted in the urine, feces & milk </li></ul><ul><li>Individuals at risk: food handlers, ranchers & veterinarians </li></ul>
  18. 18. <ul><li>Resembles Influenza & nonbacterial pneumonia, hepatitis or encephalopathy </li></ul><ul><li>No rash or local lesion </li></ul><ul><li>Weil Felix test (-) </li></ul>
  19. 19. TRENCH FEVER <ul><li>Etiology: R. quintana </li></ul><ul><li>Manifestations: headache, exhaustion, pain, sweating, cold extremities & fever with roseolar rash </li></ul><ul><li>Relapses occur </li></ul>
  20. 20. EHRLICHIOSIS <ul><li>ETIOLOGY: </li></ul><ul><li>E. sennetsu – Sennetsu fever </li></ul><ul><li>E. chaffeensis – Human ehrlichiosus </li></ul><ul><li>Leukocytic rickettsia – parasitize lymphocytes, neutrophils & monocytes </li></ul>
  21. 21. <ul><li>SENNETSU FEVER: </li></ul><ul><li>Fever, cervical lymphadenopathy, inc. peripheral mononuclear cells & atypical lymphocytes </li></ul>
  22. 22. <ul><li>HUMAN EHRLICHIOSIS: </li></ul><ul><li>Similar to RMSF </li></ul><ul><li>Leukopenia & thrombocytopenia </li></ul><ul><li>Only 20% of cases present with rash </li></ul>
  23. 23. DIAGNOSIS <ul><li>Weil-Felix test – not specific </li></ul><ul><li>Serological tests – most sensitive & specific </li></ul><ul><li>- microimmunofluorescence </li></ul><ul><li>- microagglutination </li></ul><ul><li>- complement fixation </li></ul>
  24. 24. ? - - - ++ - - OXK ? - - + - - +/- OX2 ? Trench fever - Q fever - Rickettsialpox + RMSF - Scrub typhus ++ Endemic typhus ++ Epidemic typhus OX19 WEIL-FELIX DISEASE
  25. 27. THANK YOU

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