Case of the Week 154

A biopsy of the large intestine was performed on a 43 year old HIV positive male with chronic watery diarrhea. Hematoxylin and eosin stained sections are shown below, which reveal multiple small (5-7 micron diameter) objects that appear to sit on the mucosal surface.

Large intestine mucosal surface, 400x original magnification. Objects of interest shown by arrow heads.


1000x original magnification


Deep mucosal crypt in the large intestine, 400x original magnification


1000x original magnification


What additional tests could be performed for confirmation?

Answer to Case 154

Answer: Cryptosporidium spp.
C. parvum and D. hominis are the 2 main species causing human disease.

As some of the commentors mentioned, this case demonstrates the classic site and morphology of this parasite - small, round, 5-7 micrometer diameter parasites with an intracellular, extra-cytoplasmic location in the intestine. As Alasdair mentioned, cryptosporidiosis can be fatal in HIV+ and is one of the most common infections associated with HIV/AIDS.

Additional tests that could be performed for confirmation include stool examination with modified acid fast or safranin stains, or antigen detection methods. The latter is typically the most sensitive method for detecting Cryptosporidium.

Case of the Week 153

The following were found on Stool ova and parasite exam. No history is available. The objects vary in size from 5 to 10 micrometers in diameter.





Identification?

Answer to Case 153

Answer: Blastocystis hominis

Anonymous said it well: "Blastocystis. There are different morphological forms of the organism and subtypes. Host specificity is poor. Many experts have dropped the "hominis".

I will look forward to further studies to determine if we keep the species designation. Meanwhile, I will continue to use the nomenclature used by the U.S. Centers for Disease Control and Prevention on their excellent Parasite web site, DPDx

Blastocystis can be identified in stool specimens by its characteristic cyst morphology, with central vacuole and peripheral nuclei (below).

Trichrome Stain, 1000x original magnification


This "thick-walled cyst" is thought to be the form of the organism that is transmitted to others. However, much is unknown about Blastocystis, including its life cycle and ability to cause disease. Recent phylogenetic studies have placed this organism in the informal group, the stramenopiles, which include water molds, diatoms, and brown algae. I'm sure there will be much more information to come on this fascinating protozoan parasite.

Case of the Week 152

The following were found in a stool parasite exam from a 50 year old farmer with bloody diarrhea. Identification?

Unstained wet preparation, object measures approximately 100 micrometers in length


Unstained wet preparation, object measures approximately 100 micrometers in length


Trichrome stained preparation, object measures approximately 70 micrometers in diameter.

Answer to Case 152

Answer: Balantidium coli trophozoites and cyst

This giant protozoan seems to inspire parasitologists everywhere by its size and unique features. As Tom said "It's like the over-sized mascot of the protozoan world. It is so big and fuzzy, it just makes you want to give it a hug." My predecessor, Dr. John Thompson, used to call it "the aircraft carrier of the fecal flotilla."

Perhaps the the folks at GIANTmicrobes WILL someday make a plush version. If you can get a plush bedbug to snuggle with, surely you could get a big furry protozoan? Until then, you will have to make do with the following image: