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What are the general characteristics of Rickettsiae?
- Intracellular organisms
- Very small (0.2-0.8 micro meters)
- Grown in egg yolk or cell lines
- Zoonoses humans accidental host
- Infection transmitted by ticks
- Short, non-motile G(=) bacilli
- Not grown in cell-free media
- Groups divided according to clinical infection: Spotted Fever, Typhus, Scrub typhus
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What are the Etiologic agent?
- Rocky Mountain Spotted (Rickettsia rickettsii)
- Typhus (Rickettsia prowazekii (murine)) and R. typhi louse borne)
- Scrub typhus (Orientia tsutsugamushi)
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What are the Laboratory Diagnosis?
- ID in refernce laboratories
- Requires Level 3
- Most labs do serology (latex, IF, Weil-Felix OX19, OX2, OXK)
- Molecular techniques not standarizd
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What are the characteristics of Rocky Mountain Spotted fever?
- Transmitted by Ticks
- R. rickettsii
- Organism first seen 1916
- Humans accidental host
- Disease acquired by tick bite
- Live and replicate in host endothelial cells
- Spread is hematogenous
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What are the Clinical Manifestations of Rocky Mt Spotted Fever?
- Flu-like symptoms, incubation 7 days
- Symptoms:fever, myalgia, headache
- Rash begins in ankles and wrist, extending to palms and soles of feet
- Once disseminated can cause vasculitis of blood vessels, lungs, breain heart
- Mechanism not understood
- Te or chloramphenicol
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What are the characteristics of the Typhus group?
- R. typhi (endemic)
- Replicate in cytoplasm
- Cell lysis release all ricketts
- Vector is a flea
- Symptoms include fever, headache and rash occurs in trunk and extremities, if present, rarely on palms of hands
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Characteristics of The other typhus group:
- Epidemic louse-borne typhus
- R. prowasekii transmitted by louse
- Reservoirs are primarily humans
- The clinical course may resemble spotted fever, the rash may appear in hands and feet
- Unlike spotted fever may involve the face
- Untreated has a mortality rate 40%
- Recrudescent typhus called Brill-Zinsser
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What are the characteristics of Scrub typhus?
- Occurs in India, Burma, Russia, and Australia
- Orientia tsutsugamushi transmitted by mites
- Similar symptoms of rickettsia fever, headache and rash
- Rash starts in the trunk and spreads to extremities does not involve palms and hands
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What are the characteristics of Enrlichia chafeensis?
- Human monocytic ehrlichiosis
- Obligate intracellular G(=) coco bacillus
- Multiply in phagosomes of host WBC
- Patient is febrile, leukopenic, thromocytopenic, and anemic
- Only 20% patients have rashes (most common in pediatric patients)
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What are the S/S of Ehrlichia?
- Neutropenia in acute phase, leukocytosis in later stages (not always) thrombocytopenia
- Hypoproteinemia, hypoalbuminemia, and decreased sodium, potassium, chloride during the first 10 days
- CPK and LDH often elevated in acute infection
- Elevated ALT, AST, and AlkP
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