Case 6
A male CDC employee had diarrhea for six weeks before consulting the occupational health
clinic. He had traveled to several different African countries a few weeks prior. His
symptoms included abdominal cramps and frothy stools. The man treated himself with
metronidazole without improvement. A stool specimen preserved in zinc polyvinyl alcohol
(Zn-PVA) was submitted to the reference laboratory for diagnostic evaluation. Smears were
made from the specimen, stained with trichrome, and examined. An example of cyst-like
organisms, averaging 13 to 14 micrometers in diameter, that were found in moderate
numbers in the trichrome stained smear. The movie clip simulates focusing through several
planes when you move the slider control of your viewer back and forth. Figures A and B
show examples of a different stage of the same or similar organisms, averaging 15 to 16
micrometers in diameter. What is your diagnosis? Based on what criteria?