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Rickettsia

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  • 1. RICKETTSIA ELIZABETH P. QUILES, M.D.,FPASMP DEPARTMENT OF MICROBIOLOGY OUR LADY OF FATIMA UNIVERSITY COLLEGE OF MEDICINE
  • 2. RICKETTSIA
    • CHARACTERISTICS:
    • Structurally similar to gram (-) bacilli
    • - DNA & RNA
    • - enzymes for Kreb’s cycle
    • - ribosomes for protein synthesis
    • - inhibited by antibiotics  Tetracycline & Chloramphenicol
  • 3.
    • Originally thought to be viruses because:
    • - small size
    • - stain poorly with gram stain
    • - grows only in cytoplasm of Eukaryotic cells
    • - obligate intracellular parasites EXCEPT Coxiella
  • 4.
    • Reservoirs – animals & arthropods
    • Humans are accidental hosts
    • Cell wall:
    • - peptidoglycan
    • - LPS – have weak endotoxic activity (absent in Ehrlichia)
    • Genera:
    • Rickettsia Rochalimaea
    • Coxiella Ehrlichia
    • Orientia
  • 5.
    • Stains weakly with gram stain  Giemsa or Gimenez stain
    • Easily destroyed by heat, drying & bactericidal agents EXCEPT Q fever  due to the formation of endospore-like structure by C. burnetti
  • 6.
    • Intracellular location:
    • typhus group – cytoplasm
    • spotted fever group – nucleus
    • Rochalimaea – surface of Eukaryotic cells
    • Coxiella & Ehrlichia – cytoplasmic vacuoles
  • 7.
    • PATHOLOGY
    • Multiply in endothelial cells of small blood vessels
    • Vasculitis
    • (skin – rashes;other organs – DIC & vascular occlusion)
    • Swollen & necrotic
    • Thrombosis of the vessels
  • 8.
    • VECTORS:
    • RMSF – Dermacentor andersoni
    • Rickettsialpox – Allodermanyssus sanguinus
    • Scrub typhus – trombiculid mites
    • Epidemic typhus – Pediculus humanus
  • 9.
    • Ehrlichiosis – Amblyomma americanus (lone star tick)
    • Trench fever – Pediculus humanus
    • Murine typhus – Xenopsylla cheopis &
    • Ctenophalides felis
  • 10. RICKETTSIAL INFECTIONS
    • Fever, headache, malaise, prostration, skin rash & hepatosplenomegaly
    • Classified into groups:
    • 1. Typhus Group – Epidemic typhus, Murine typhus, Scrub typhus
    • 2. Spotted Fever Group – RMSF, Rickettsialpox
    • 3. Q Fever
    • 4. Trench fever
    • 5. Ehrlichiosis
  • 11. TYPHUS GROUP
    • Maculopapular rashes with the sparing of the palms & soles
  • 12. EPIDEMIC TYPHUS (LOUSEBORNE TYPHUS)
    • Etiology: R. prowazekii
    • severe systemic infection & prostration
    • more fatal
    • Brill-Zinsser Disease  recrudescent disease
  • 13. ENDEMIC TYPHUS (MURINE TYPHUS)
    • Etiology: R. typhi
    • similar features with Epidemic typhus but milder & rarely fatal except in the elderly
  • 14. SCRUB TYPHUS
    • Etiology: Orientia tsutsugamushi
    • resembles Epidemic typhus except for the ESCHAR
    • generalized lymphadenopathy & lymphocytosis
    • cardiac & cerebral involvement may be severe
  • 15. SPOTTED FEVER GROUP
    • Rash appear 1 st on the extremities with involvement of the palms & soles
  • 16. RICKETTSIALPOX
    • Etiology: R. akari
    • mild disease resembling Varicella
    • firm red macule at the bite site  deep-seated vesicle  eschar
  • 17. Q FEVER (QUERY FEVER)
    • Etiology: Coxiella burnetti
    • MOT: inhalation of dust containing the organism or aerosols
    • Excreted in the urine, feces & milk
    • Individuals at risk: food handlers, ranchers & veterinarians
  • 18.
    • Resembles Influenza & nonbacterial pneumonia, hepatitis or encephalopathy
    • No rash or local lesion
    • Weil Felix test (-)
  • 19. TRENCH FEVER
    • Etiology: R. quintana
    • Manifestations: headache, exhaustion, pain, sweating, cold extremities & fever with roseolar rash
    • Relapses occur
  • 20. EHRLICHIOSIS
    • ETIOLOGY:
    • E. sennetsu – Sennetsu fever
    • E. chaffeensis – Human ehrlichiosus
    • Leukocytic rickettsia – parasitize lymphocytes, neutrophils & monocytes
  • 21.
    • SENNETSU FEVER:
    • Fever, cervical lymphadenopathy, inc. peripheral mononuclear cells & atypical lymphocytes
  • 22.
    • HUMAN EHRLICHIOSIS:
    • Similar to RMSF
    • Leukopenia & thrombocytopenia
    • Only 20% of cases present with rash
  • 23. DIAGNOSIS
    • Weil-Felix test – not specific
    • Serological tests – most sensitive & specific
    • - microimmunofluorescence
    • - microagglutination
    • - complement fixation
  • 24. ? - - - ++ - - OXK ? - - + - - +/- OX2 ? Trench fever - Q fever - Rickettsialpox + RMSF - Scrub typhus ++ Endemic typhus ++ Epidemic typhus OX19 WEIL-FELIX DISEASE
  • 25.  
  • 26.  
  • 27. THANK YOU