USMLE Q Bank Step 1-9

A 29 year-old man presents to his physician complaining of fatigue and lethargy for the past 3 days after he came back from a hiking trip in Northern California. During the trip, he noticed a rash on his left arm. The rash was smaller but now it’s expanding in size. On examination, the rash looks round with central clearing.

What is the most likely organism involved in this condition?

A- Meningococci

B- Staphylococcus aureus

C- Borrelia burgdorferi

D- Rickettsia prowazekii

E- Treponema pallidum


This is most likely the characteristic rash of  Lyme disease. It is caused by borrelia burgdorferi infection transmitted by Ixodes tick. Other microorganisms don’t show this particular rash.

The correct answer is C

4 thoughts on “USMLE Q Bank Step 1-9”

  1. That’s true. Thanks Dr Bilal

  2. Hi Mr F

    We care!

    Thanks for the comment

  3. Doxycycline 200mg should b taken in stat dose….

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