Sunday, May 19, 2019

Case of the Week 545

This week's case was donated by Dr. David Pritchard. The following worm was noted in the toilet of a patient with an extensive international travel history. Likely identification?

Monday, May 13, 2019

Case of the Week 544

This week's case features an interesting finding in a concentrated stool specimen. The photos are from my awesome technical specialist, Heather Arguello. The individual structures are approximately 25  micrometers in length, while the longer tubular structure is 330 micrometers long.


Sunday, May 12, 2019

Answer to Case 544

Answer to Parasite Case of the Week 544: Ascus with ascospores (presumed mushroom) spores. Interestingly, it is morel season in many parts of the United States, and these appear to be a perfect match to morel ascospores!
While we commonly see mushroom spores in stool specimens (and have to differentiate them from  helminth eggs), and intact ascus (a sac in which the spores of ascomycete fungi develop) is rarely seen. Thanks again to my lead tech Heather who took the time to snap a photo of this cool finding!

Monday, May 6, 2019

Case of the Week 543

This week we are featuring our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp.

The patient is a 15 year old boy returning from swimming camp, who presents with several-day history of profuse watery diarrhea. A stool specimen was submitted for parasite examination, and multiple small (3-6 ┬Ám), round structures were identified. The following photos are taken after:

1. Negative fuchsine staining according to Heine (brightfield microscopy)
2. Negative fuchsine staining according to Heine (phase-contrast microscopy)

3. Ziehl-Neelsen staining (“cold” modified technique)

Sunday, May 5, 2019

Answer to Case 543

Answer to Parasite Case of the Week 543: Cryptosporidium sp. oocysts

The case shows how Cryptosporidium oocysts look in a variety of different preparations including phase contrast (very cool). As we are all taught during training, Cryptosporidium spp. oocysts are red-pink using a modified acid fast stain (as shown in image 3 of this case) and measure 4-6 micrometers in diameter, thus allowing their differentiation from the similarly-appearing Cyclospora cayetanensis oocysts (which are 8-10 micrometers in diameter). Florida Fan reminded us that not all of the oocysts will reliably stain with the modified acid fast stain, and thus some may appear as 'ghost' cells or negative outlines. A modified safranin stain can also be used and has been reported to more reliably stain the oocysts.

Florida Fan mentioned that the direct fluorescent antibody (DFA) for Cryptosporidium spp. oocysts - widely regarded as the most specific microscopic method - doesn't necessarily detect all Cryptosporidium species, and thus there is the potential false negative results. In certain cases, confirmation with another method may be helpful.

Finally, Old One tells a tale of prior infection in our case comments that he thankfully survived! It is indeed possible that his prior infection stimulated development of a protective immune response - likely an interferon-gamma mediated memory T cell response. However, it is not clear if this immune response would prevent future infections with all different species of Cryptosporidium.

Thanks again to Idzi for sharing this beautiful and classic case!

Monday, April 29, 2019

Parasite Case of the Week 542

This week's case is a lovely gif image compiled by our excellent parasitology technical specialist, Heather Arguello. The following structures were seen on a non-nutrient agar culture that had been inoculated with corneal scrapings. The plate had been overlain with Escherichia coli to provide a food source for parasites that may be present in the specimen. The central structure is ~40 micrometers in maximum dimension, while the rounded structure to the left is ~15 micrometers in diameter. Identification?

Sunday, April 28, 2019

Answer to Case 542

Answer to Parasite Case of the Week 542: Acanthamoeba sp. trophozoite and cysts

The free-living amebae, Acanthamoeba species and Naegleria fowleri (but not Balamuthia mandrillaris) can be grown on non-nutrient agar overlain with bacteria to provide a food source for the organisms. In this case, the presence of a characteristic double-walled cyst and trophozoite, along with the source (corneal scrapings) allow us to identify this ameba as an Acanthamoeba species.
We sadly did away with our free-living amebae culture a while back and replaced it with a multiplex real-time PCR assay. It's faster than culture, while providing equal sensitivity, so it is better for patient care. However, I do miss seeing these cool organisms grow in culture!

Monday, April 22, 2019

Case of the Week 541

This week's case was generously donated by Drs. Mauro Saio and David Hamer. The patient is a middle-aged male who noted the following objects in his stool. Individually, they measured approximately 1 cm in length. Identification?

Sunday, April 21, 2019

Answer to Case 541

Answer to Parasite Case of the Week 541: not a parasite; citrus juice vesicles.

This is a not-uncommon finding in stool that is helpful to recognize, since it is occasionally submitted as a potential parasite. In this case, the patient reported eating clementines regularly. So here is a dissection of a clementine for comparison:

Pretty good, huh? Of course it's not possible to recognize the type of citrus from this case alone, and a report of "not a human parasite" is usually sufficient for patient care.
Wikipedia has a nice article on juice vesicles if you would like more information.

Monday, April 15, 2019

Case of the Week 540

This week's beautiful photographs are from Emily Fernholz at my lab. These objects were seen in a human stool specimen and measure approximately 80 micrometers in length. Identification?

The features are nicely appreciated on this video: