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27 Cards in this Set

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What are Rickettsia?
Rickettsia is a small, Gram neg non motile rod to coccoid shaped bacterium. Like Chlamydia it is an obligate intracellular parasite(steals ATP).
What are some of the differences between Rickettsia and Chlamydia?
1. Rickettsia requires an arthropod vector(except for Q fever)
2. Rickettsia replicates freely in the cytoplasm, Chlamydia in endosomes(inclusions)
3. Rickettsia has a tropism for endothelial cells that line blood vessels, Chlamydia likes columnar epithelium.
4. Cause different diseases. Most Rickettsia cause rashes, high fevers and headaches.
Some Rickettsia share antigenic characteristics with certain strains of Proteus vulgaris bacteria. TRUE/FALSE
TRUE. The Proteus vulgaris strains that share these common antigens are designated OX-2, OX-19, and OX-K.
What is the Weil-Felix reaction?
It is a classic test that uses these cross reacting Proteus vulgaris antigens to help confirm a diagnosis of a Rickettsial infection.
Hoe is the WEIL-FELIX test executed?
It is done by mixing the serum of a patient suspected of having a Rickettsial disease, with antigens from specific strains of Proteus vulgaris. If the serum has anti-Rickettsial antibodies, latex beads coated with Proteus antigens will agglutinate, indicating a positive W-F test.
Infact, when this test is done on a patient with symptoms of Scrub-typhus infection, a negative OX-19 and OX-2, along with a positive OX-K is confirmatory.
Therapy for all Rickettsial diseases consists of doxycycline and chloramphenical. TRUE/FALSE
TRUE.
What is Rocky mountain spotted fever?
It presents within a week after a person is bitten by either the wood tick, Dermacentor andersoni or the dog tick, Dermacentor variabilis. Both can transmit Rickettsia rickettsii.
What are the signs of RMSF?
Fever/conjunctival redness/severe headache and a rash that appears around the body.
RMSF is more common in the southeastern US tick belt, then in the Rocky mountain region(Appalachian spotted fever). TRUE/FALSE
TRUE.
What is its pathgenesis?
They proliferate in the endothelial lining of small blood vessels and capillaries causing small hemorrhages. though it can resolve in several weeks, it can be fatal if A/B therapy is delayed.
What is Rickettsia akari?
It causes Rickettsialpox and is transmitted to humans via mites that live on house mice. Though it often self limiting, it responds quite well to doxycycline.
What is Rickettsia prowazekii?
Two species of Rickettsia cause typhus; R. prowazekii,(epidemic form) and R. typhi,(endemic form).
Infection with one confers immunity to the other.
R. prowazekii wiped out a third of Napoleon's army, and caused 3 million Russian deaths during WW 1. TRUE/FALSE
TRUE.
Currently, flying squirrels are the reservoir in the southern US. Some cases occur when lice or fleas from infected squirrels bite humans. TRUE/FALSE
TRUE. Epidemic typhus is given by fever and headache, though the rash spares the palms soles and face, unlike RMSF. Patients may become delirious or stuporous. Gangrene may develop as well.
What is a common treatment protocol for R. prowazekii?
Tetracycline/Chloramphenicol
What is Brill-Zinsser disease?
patients who recover without antibiotic therapy from epidemic louse born typhus could still retain the pathogen, R. prowazekii, in a latent state. It may relapse as Brill-Zinsser dz.
Though there is no skin rash, due to preformed antibodies.
How is Brill-Zinsser dz diagnosed/
It is made by demonstarting a rapid early rise in IgG titer specific for Rickettsia, rather than a rapid rise in IgM, which occurs in the primary infection. Untreated patients may serve as reservoirs between epidemics.
What is Rickettsia typhi?
Endemic flea borne typhus is similar to epidemic typhus, yet it is not as severe and is not epidemic in nature.
Rodents serve as reservoir, and the disease is transmitted to humans via the rat flea, Xenopsylla cheopis. ( This flea was responsible for transmission of the bubonic plague).
Fever, rash and headache develop, though it is milder, than the epidemic form, it can be serious.
What is the therapy?
Doxycycline and Chloramphenicol
What is Rickettsia tsutsugamushi?
It is found in Asia and southwest pacific. It affected soldiers during WW2 and in the vietnam war.
It is spread by the bite of larvae(chiggers) of mites. The mites live on rodents and the chiggers live in the soil. (Scrub) There is fever, headache and scabs. Therapy is the same as the others.
What is Bartonella)Rochalimaea quintana)?
Also called Trench fever, it is a louse borne febrile disease that occurred during WW1. It is not aqn obligate intracellular organism.
What are the signs?
Patients develop fevers, rash and a headache with severe back and leg pains.(After recovery, many soldiers relapsed 5 days later(quintana), but fatalities are rare.
What is Bartonella(formerly Rochalimaea henselae)?
It is also called cat scratch disease and bacillary angiomatosis.
Regional lymphnodes will enlarge and a low grade fever may occur. The agent Bartonella henslae. Anti Bartonella antibodies have been found.
What is Bacillary angiomatosis?
B. henslae may also be responsible for B. angiomatosis, which involves proliferation of small blood vessels in the skin and organs of AIDS patients.
What is Coxiella burnetti?
This organism is unique to the Rickettsia, because like the Gram + spore formers(Clostridium and Bacillus), it has endospore form. this confers certain properties to the agent.
What are some of the properties conferred to the spore form of Coxiella burnetti?
1. Resistance to heat and drying(milk and pasteurization processes).
2. Prolonged extracellular existance(outside of host)
3. Non-arthropod transmission; C. burnetti grows in tick and cattle. Spores are viable in dried tick feces on hides and dried cow placentas. When spores are inhaled by humans, Q fever results.
4. Pneumonia: This is the only Rickettsial disease that causes pneumonia similar to that of Mycoplasma, and there is no rash.
What is Ehrlichia canis/chafeensis?
Dogs get the bacteria from ticks which jump from dog to dog. Humans can be bitten.
E. chafeensis causes human Ehrlichiosis, and is similar to RMSF(high fever and headache, rashes are seen less frequently.