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:

Case of the Week 151

The following were seen microscopically (4x objective) on a non-nutrient agar plate containing stool. The patient was from Cambodia and presented with abdominal pain and eosinophilia.



Here is a macroscopic image of the agar plate with the stool specimen.




Diagnosis?

Answer to Case 151

Answer: Probable infection with Strongyloides stercoralis. Other larvae, such as those of hookworm species, can have a similar appearance on agar culture, and thus it is important to correlate the laboratory findings with the clinical presentation. In this case, the patient had a long standing eosinophilia, consistent with ongoing autoinfection with S. stercoralis. Microscopic examination of the larvae can also confirm the identification. MicrobeMan gave a great description in his comment to this post: "The nutrient agar plate very nicely demonstrates the production of furrows left in the wake of the migrating larvae, which emanate away from the central "dollop" of feces. The bacteria are dragged along by the migrating worms and grow in the furrows, which acts as an indicator for larval migration. As a side note, this particular scenario can play out in vivo, as well. In the host, gut flora can be introduced outside of the intestinal lumen by larvae that have penetrated the intestine." The last point above is very important; bacteria introduced into the blood stream by migrating larvae can cause bacterial sepsis and contribute to the morbidity and mortality of strongyloidiasis.

Case of the Week 150

A 50 year old male from South America died suddenly and an autopsy was performed. show are hematoxylin and eosin stained tissue sections of myocardium (heart muscle). Diagnosis?
(CLICK ON IMAGES TO ENLARGE)

(100 times original magnification)


(400 times original magnification)


(1000 times original magnification)


(1000 times original magnification)

Answer to Case 150

Answer: Trypanosoma cruzi amastigotes

congratulations to Josh, Alasdair, BW, and Anonymous who wrote in with the correct answer!

The diagnostic features of this case are:
1. Location in cardiac muscle
2. formation of "pseudo-cysts"



3. Amastigotes (non-motile forms) within pseudocysts, containing both a nucleus and rod-shaped kinetoplast