Answer to Parasite Case of the Week 788: Pentatrichomonas hominis trophozoites
Note the classic 'jerky' motility of P. hominis trophozoites. I've never seen so many P. hominis in a specimen before!
Like Trichomonas vaginalis, there is no known cyst stage of this protozoan parasite. P. hominis trophozoites move using 5 flagella: 4 are directed anteriorly, while the 5th is directed posteriorly, forming the outer edge of an undulating membrane. This results in characteristic motility that Dr. Richard Bradbury likes to describe as "a man trapped inside a plastic bag"! You can see a very nice video and still images of this phenomenon in Case of the Week 737. For those of you who have been following this blog since the beginning (2007!), you may recall that P. hominis was the parasite highlighted in Case of the Week 5. Check out the fun video that Alex Ball made for me back then in the Answer to the Case of the Week 5.
Thanks again to Idzi Potters and the Institute of Tropical Medicine Antwerp for donating this great case!
2 comments:
Thank you Dr. Pritt for such a rare video. The advent of fixatives preserves the organisms yet this only renders us a post mortem picture. The last time I saw a live trophozoite of E. histolytica/ dispar was in 1980 while working as a volunteer in the Out Patient Department of the Refugees Processing Center Phanatnikhom, Thailand. We had no means for concentration nor stains, just direct smears on raw stool in saline drawn from a bag for perfusion. Just imagine a piece of jigsaw puzzle without sharp corners, the amoeba extending out a pseudopod in one direction and draws the entire sac of cytoplasm with it, then it projects itself in another direction and pulls along the rest of it. It was fascinating to see.
Thank you and best wishes,
Florida Fan
Thank you for the comment, Florida Fan. I agree that we rarely get to see motile protozoa these days as the containers with fixative are given directly to patients at many labs. It's better for preservation of morphology, but makes it a little less interesting for the lab! I've never seen a motile E. histo/dispar trophozoite outside of a research lab. It sounds like a fascinating thing to see.
Best,
Bobbi
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