Giardia questions are deceptively “simple”: a kid goes camping, gets diarrhea, and you’re supposed to move on. But NBME-style vignettes love to test whether you understand mechanism + morphology + transmission + treatment—and whether you can rule out close-looking distractors. Let’s do a true Q-bank breakdown where every answer choice teaches you something high-yield.
Tag: Microbiology > Mycology & Parasitology
The Clinical Vignette (Giardia lamblia)
A 23-year-old graduate student returns from a weekend backpacking trip. Over the past week he has had foul-smelling, greasy diarrhea, bloating, flatulence, and crampy abdominal pain. He denies fever or blood in the stool. He drank from a stream after filtering water with a portable device. Exam shows mild diffuse abdominal tenderness. Stool studies are negative for fecal leukocytes.
Question: Which organism is the most likely cause?
Correct answer: Giardia lamblia (Giardia duodenalis)