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48 Cards in this Set

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What are the Rickettsia
Members of the family Rickettsiaceae are obligate intracellular bacteria that are usually transmitted by arthropods
What are the four groups of Rickettsia
Typhus
Spotted Fever
Ehrlichioses
Others
What are the genera of Rickettsia
Rickettsia
Ehrlichia
Anaplasma
Coxiella
Orientia
Bartonella (not actually Rickettsiaceae)
What is the general structure and physiology of Rickettsia
Fastidious, obligate intracellular (except Bartonella), pleomorphic, Gram negative coccobacilli
Limiting membranes contain muramic and diaminopimelic acid
Why are members of the family Rickettsiaceae not free living
They require cofactors such as ATP, NAD, and coenzyme A from the host cell
They leak essential metabolites when outside the host cell
What does spread of Rickettsia from cell to cell involve
Actin polymerization, similar to Listeria and Shigella
Where in the cell does the Typhus group of Rickettsia grow in the cell
Usually free in the cytoplasm
Where does the Spotted fever group of Rickettsia grow in the cell
Sometimes in the nucleus
Where does the Ehrlichia and Anaplasma group of Rickettsia grow in the cell
Phagosome of human granulocytes or monocytes (depends on organism)
Where does the Coxiella burnetii group of Rickettsia grow in the cell
Cytoplasmic vacuoles
The pathogenesis of what microorganisms is vasculitis caused by proliferation of the organisms in the endothelial lining of small arteries, veins, and capillaries. Vascular lesions are prominent in the skin (except with Q fever)
Typhus group and Spotted Fever group organims, caused by Rickettsial bacteria
What are the clinical manifestations of Rickettsial infection
Skin rash, (except Q fever), fever, severe headache, malaise, prostration, and enlargement of the spleen and liver
Where are Rickettsiae most frequently isolated from patients
The blood. A four fold rise in antibodies is tested
What is the treatment for Rickettsial infections
Tetracyclin and chloramphenicol if started early. These only suppress Rickettsial growth
Sulfonamides enhance their growth and are contraindicated
What is the epidemiology of Epidemic typhus
Also called louse-borne typhus, prototype of the typhus group of rickettsial diseases. The disease and Brill Zinsser disease are caused by Rickettsia prowazekii.
What disease does Rickettsia prowazekii cause
Epidemic typhus
What is the epidemiology of Louse-borne typhus
Person to person by the body louse Pediculus corporis. Louse feces are scratched into a bite
What is Brill-Zinsser disease
Recrudescence of an old typhus infection.
Why does Brill Zinsser disease occur
Rickettsia can persist for many years in the lymph nodes of an asymptomatic individual. Humans may therefore be the primary reservoir of Rickettsia prowazekii
What cute little furry animal may serve as a reservoir of Rickettsia prowazekii
The flying squirrel
These are signs and symptoms of what disease:
Severe systemic infection and prostration. 2 week fever. Rash starts in the axillary fold and upper frame and spreads centrifugally. Face, palms, and soles are spared. 40% case fatality rate
Epidemic typhus
How is Epidemic typhus prevented
Delousing, vaccination
What causes Murine (endemic) typhus
Rickettsia typhi. Shares a common soluble antigen with Ricketsia prowazekii
Who gets Murine (epidemic) typhus
Those whose occupation or living condition brings them in close contact with rats and their fleas
What is the clinical feature of murine typhus
Similar to but milder than epidemic typhus. Again, rash starts on the trunk
Note that rashes of spotted fever organisms are primarily peripheral
What causes Rocky mountain spotted fever
Rickettsia rickettsii
What are the two principal vectors of rocky mountain spotted fever
Wood tick Dermacentor andersoni
Dog tick Dermacentor variabilis
What disease has the usual picture of a child with an acute, severe febrile disease characterized by myalgia, malaise, plus a late-appearing rash?
Disease caused by Rickettsia rickettsii, such as rocky mountain spotted fever. A few patients may have a fulminant febrile disease resulting in death within 4-5 days
The rash of what usually appears first on the extremities, moves centripetally, and involves the palms and soles?
The rash of Rocky mountain spotted fever and other members of the spotted fever group
An experimental vaccine for Rocky mountain spotted fever targets what surface antigens on Rickettsia rickettsii
Antigens OmpA and OmpB
What are the two spotted fevers caused by Rickettsiae
Rocky mountain spotted fever and Rickettsial pox
What causes Rickettsial pox
Rickettsia akari
How is Rickettsial pox transmitted
It is a zoonotic disease (Mus musculus). Seems to be transmitted among mice by mouse ectoparasites. Transmitted to humans by house mites
What are the clinical manifestations of Rickettsial pox
Mild disease, with a rash that resembles varicella (chicken pox). A painless papule that ulcerates and forms an eschar usually occurs at the site of the mite bite
What are the two Ehrlichiosis diseases
Human monocytic ehrlichiosis
Human granulocytic ehrlichiosis
What is the etiology of Human monocytic ehrlichiosis
Ehrlichia chaffeensis is transmitted by ticks (Amblyomma americanum) and infects human monocytes
What is the clinical manifestation of Human monocytic ehrlichiosis
Resembles rocky mountain spotted fever but the rash is usually fleeting and only occurs in 33% of cases
What is the etiology of Human granulocytic ehrlichiosis
It was Ehrlichia, but now it's Anaplasma Phagocytophilum
What causes Q fever
It is a zoonotic infection caused by Coxiella burnetii
How is Coxiella burnetii, which causes Q fever, different from other rickettsial organisms
Resistant to desiccation and physical agents
Survives for long periods of time in the inanimate environment
Does not elicit agglutination to Proteus Z antigen (negative Weil Felix)
Infrequently produces a rash
Transmitted by aerosols
What is the reservoir for Coxiella burnetti
Domestic livestock, mainly goats, sheep, or dairy cattle
What disease resembles influenza, nonbacterial pneumonia, hepatis, or encephalopathy, and can cause chronic infection that may lead to endocarditis
Q fever, though it is often asymptomatic
How is Q fever prevented
New emphasis on vaccine
What causes scrub typhus
Orientia tsutsugamushi
What are the clinical manifestations of scrub typhus
An acute febrile illness that resembles epidemic typhus except an eschar (punched out ulcer with a blackened scab) indicates the location of the mite bite
What diseases does Bartonella quintana cause
Classical trench fever: body louse vector
Urban trench fever: louse-borne
Bacillary angiomatosis: immunocompromised
What diseases does Bartonella bacilliformis cause
Carrion's disease transmitted by sand fly; localized to rivers and valleys of Andes mountains; fever, bacteremia, anemia (Oroya fever), with or without cutaneous manifestation (verruga)
What diseases does Bartonella henselae cause
Cat scratch fever: lymphadeopathy, fever, occasional visceral and osteolytic lesions. Probably flea vector
Bacillary angiomatosis: immunocompromised