USMLE-Rx Step 3 Qmax Challenge #31045

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USMLE-Rx Step 3 Qmax Challenge #31045A 54-year-old man presents to the office because of 3 days of diarrhea. The patient reports that 3 days ago he started to experience bloody diarrhea 5-6 times a day, associated with significant abdominal pain. He also noticed chills but did not check his temperature. He denies recent travel except to a restaurant in a nearby town about 1 week ago. He has no sick contacts and no recent antibiotic exposure. His temperature is 38.4°C (101.2°F), blood pressure is 135/65 mm Hg, pulse is 91/min, and respiratory rate is 18/min. On examination the mucous membranes are slightly dry, and the patient has abdominal pain primarily around the umbilicus, with no rebound or guarding. Laboratory tests show a leukocytosis with left shift. Stool is guaiac positive. Gram stain of the stool sample reveals curved gram-negative rods as shown in the image. A preliminary stool ova and parasite culture 2 days later shows few protozoa, but the results of bacterial culture are still pending.

What is the most likely cause of this patient’s diarrhea?

A. Blastocystis hominis
B. Campylobacter jejuni
C. Clostridium difficile
D. Cryptosporidium parvum
E. Shigella dysenteriae


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19 thoughts on “USMLE-Rx Step 3 Qmax Challenge #31045”

  1. Spyros Kanakaris

    I would say E. Because Campylobacter jejuni grows @ 42 C and most common appears in children. If anybody else thinks about C also please explain why.

  2. Spyros Kanakaris

    I meant B not C it was my mistake. So i believe it is E not B. If anyone has a different opinion explain why

  3. Answer is B ) campylobacter jejuni
    As shigella usually with overcrowded and patient denies any sick contacts

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