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Old 03-19-2013
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Microbiology Tick Bite Fever

A 25-year-old man develops fever, muscle pain and headache 1 week after being bitten by a tick in the grand canyon. the fever remits and he feels better in 7 days. 2-4 days later, his symptoms recur. a Giemsa stain of a peripheral blood smear shows the bacterium illustrated. which of the following is the most likely explanation for the recurrence of the symptoms?

A- Expression of endotoxin-like structures on the surface of the organism
B- Migration of the organism from the tissue site to the blood stram
C- Production of a toxin that had become suppressed during the infection
D- Secondary infection by a different organism of the same species
E- Variation of a major surface protein antigen of the organism

Tick Bite Fever-untitled.jpg
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Please explain the answer!
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B- Migration of the organism from the tissue site to the blood stream

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Old 03-19-2013
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Correct Answer E might be correct.

I think that E is correct.

Borrelia recurrentis is a species of Borrelia. It can be associated with relapsing fever. B. recurrentis is usually transmitted from person to person via the human body louse. It is notable for its ability to alter the proteins expressed on its surface. This is what causes the "relapsing" characteristic of relapsing fever.
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E makes sense.
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E- Variation of a major surface protein antigen of the organism

The spirochete borrelia recurrentis has the capacity to change it's surface antigens periodically. Antibodies produced against the antigen are effective initially, but when the organism changes it antigens they become ineffective. Hence the infection/bacteremia and fever returns/relapses.
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