Bacteriology-50 Rickettsia*
Terms
undefined, object
copy deck
- 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