Rickettsia

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Rickettsia
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Howard Ricketts

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• (Rickettsia)
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Reckettsiales
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Common characters

• Obligated intracellular parasites
• Related to arthropod vector.
• Zoonosis.

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Morphology stains

• Arranged irregularly
• polymorphism
• Small G- bacilli
• Giemsa stain violet or blue

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Cultural properties

• Binary fission
• Have both DNA and RNA
• Culture susceptible animal (guinea pig), yolksac
  of chick embryo, cell culture.

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Resistance

• weak, sensitive to antibiotic
• Survive in low temperature and dry condition
• Sulfanilamide can stimulate reckettsias
  proliferation

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Antigenic sturcture

• Group specific antigen
• Endotoxin similarly to endotoxin of bacteria
• Specy specific antigen
• membrane protein
• Weil-Felix reaction(????)
• Detect anti-rickettsial antibodies in a
  patients serum by agglutination of the proteus
  organisms. ( rickettsia posses Ag that
  cross-react with Ab of the O antigen of certain
  proteus)

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Pathogenic mechanism
Endotoxin ? Phospholipase A
Pathogenic material
Bite or feces of arthropod vector
Local( small blood vessels in lymphoid
tissue )
Pathogenic mechanism
(First bacteremia)
vascular endothelial cells
(Second bacteremia)
Fever, headache, rash
Pathogenic sites
vessels
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Pathogenicity

• Pathogenic materials
• Endotoxin similarly to endotoxin of bacteria
• Phospholipase A lysis the cell membrane and
  lysosome membrane of the host cell, causing
  hemolysis
• Pathogenic mechanism invade the epithelial cells
  of small blood vessule

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Pathogenic mechanism
Endotoxin ? Phospholipase A
Pathogenic material
Bite or feces of arthropod vector
Local( small blood vessels in lymphoid
tissue )
Pathogenic mechanism
(First bacteremia)
vascular endothelial cells
(Second bacteremia)
Fever, headache, rash
Pathogenic sites
vessels
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Infective route

• SourceRickettsiae normally enter the body
  (mammalian reservoir) through the bite or feces
  of an infected arthropod vector.-----arthropod
  vector mite, tifck, louse, flea
• Pathogenic mechanism invade the epithelial cells
  of small blood vessule

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Pathogenic mechanism
Endotoxin ? Phospholipase A
Pathogenic material
Bite or feces of arthropod vector
Local( small blood vessels in lymphoid
tissue )
Pathogenic mechanism
(First bacteremia)
vascular endothelial cells
(Second bacteremia)
Fever, headache, rash
Pathogenic sites
vessels
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Epidemic typhus (R.prowazekii)??????

• Louse-borne substandard living condition, poor
  sanitaion overwhelming bacterimia

Human
Human louse
Human louse
Human
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Epidemic typhus (R.prowazekii)??????

• Fever (temperature rises to 40ºC
• Treatment sanitation, eradication of human lice
  vaccine, tetracycline

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Endemic typhus (R. mooseri)????????

• Transmitted way

human louse
rat
rat flea
rat louse
human
human
rat flea
human louse
rat
feverheadackmaculopapular rash
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Immunity

• Mainly depends on CMI
• Strong immunity after recovery

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Microbiological examination

• Specimen blood
• Isolation and culture guinea pig
• Serological test Weil-Felix reaction

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Principle of prevention and treatment

• Control and eradicate its intermediate
• host and reservoir host
• SpecificityRat lung vaccine(???????)

Prevention
Treatment
 Chloramphenicol(???) Tetracycline(???) Ban-Sulfa
drugs(??????)
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Thank you!