Monday, April 19, 2010

Case of the Week 114

The following brain touch-preparations were stained with giemsa and viewed with a oil immersion objective. Diagnosis? (CLICK ON IMAGES TO ENLARGE)

50x oil

100x oil

50x oil

100x oil

Sunday, April 18, 2010

Answer to Case 114

Answer: As stated by cmassey, "Toxoplasma gondii. Criteria: rupturing cyst with what appear to be escaping tachyzoites. Morphology is crescent shape with a large nucleus and they appear to fit in the 4-8um by 2-3um size given in diagnostic literature."

Great job to everyone who wrote in! This case demonstrates a few nice features of T. gondii. First, there are both cyst and free tachyzoite forms as seen here:

Also, many of the tachyzoites demonstrate the classic 'arc' shape (Toxon is Greek for arc):

Monday, April 5, 2010

Case of the Week 112

The following were seen macroscopically in a duodenal aspirate. They range in length from 7 to 10 millimeters.

When they were viewed microscopically using a 4x objective, the following smaller microscopic objects were also seen in between the macroscopic objects:

Using a 4x objective, the head and tail of the larger objects looked as follows:


Higher magnification revealed that some of these small objects were moving!
Here's one that measures 60 micrometers in greatest dimension.

After some time, the following was observed:

Here's one of the microscopic objects moving. It measures approximately 300 micrometers in length.

What would happen if we plated the duodenal aspirate contents on an agar for Strongyloides stercoralis culture?

Sunday, April 4, 2010

Answer to Case 112

Answer: Hookworm; specifically Necator americanus

Cmassey said it very well with the following:
"Oh boy! Lots of cool photos! Looks to be Necator americanus with adults in the first photo, eggs and first-stage larva in the second photo, cutting plates in the third photo, bursa of adult male in the fourth photo, followed by eggs and emerging larvae. I feel like this is a trick question but if we plated the aspirate on agar then they should show furrows after some time. Not as well and as deep as Strongyloides but still detectable and more snake-like than whip-like."

Cmassey is correct on all accounts. This is Necator americanus as evidenced by the cutting plates instead of 'teeth' of Ancylostoma duodenale. Furthermore, hookworm larvae will indeed create furrows in agar culture, very similar to those created by Strongyloides stercoralis. If stool is plated directly after being passed, it will take some time for the eggs to mature and hatch the L1 larvae; therefore, it would take a few extra days for the characteristic tracks to be produced in the agar. Remember that hookworm eggs are immature when passed, and take a few days to mature and release larvae. This usually occurs in the soil, but larvae can also be seen in stool when it has been sitting for a few days prior to examination. In this case, the duodenal aspirate was delayed in transit, allowing time for the eggs to mature and hatch.

In regard to the agar culture method, this method was first presented by Tamiki Arakaki in 1988 as a means of increasing the detection of Strongyloides stercoralis from stool. Since the original description, numerous investigators have shown a significant increase in sensitivity over O&P concentration methods and the Baermann funnel technique. Arakaki also noted that hookworm could be seen by the agar method, but that the furrows were characteristically much thicker than those left by Strongyloides larvae, and thinner than those left by free-living adults of S. stercoralis. I'm not sure I would easily be able to tell hookworm from Strongyloides furrows apart, but we could definitely confirm that the hookworm larvae left macroscopically visible tracks in the agar, by migrating through the agar and dragging bacteria with it.

Here's an image from this case:

Nice tracks!

Finally, Anonymous had a interesting suggestion with "Ostertagia ostertagi". This is a parasite of cattle, that has rarely been reported from humans - typically in cases where humans and livestock live in close proximity. However, the characteristic morphology of the adults and larvae in this case were consistent with N. americanus.