Microbiology Fun

Some of you may be interested in Pritish's new line of microbiology-related T-shirts. They're hilarious!

http://www.pritishirts.com

He's open to suggestions for more T-shirt designs.

Case of the Week 26

Here is a tricky case for you to ponder. I was doing some research a few years back, using beef as a control for immunohistochemical staining. My fellow researchers and I were very surprised to see the above cysts in our beef samples. These were run-of-the-mill sirloin cuts bought at the local supermarket.

Identification?
What are these parasites, and could they potentially infect humans?

Answer to Case 26

This is a classic example of the muscle cyst form of Sarcocystis. This apicomplexan parasite has a lifecycle similar to Toxoplasma gondii. Depending on the species, humans can be the definitive host (and contract a GI infection) or the intermediate host (and form muscle cysts). This particular species is S. cruzi, which is not a human pathogen. However, S. hominis is also found in beef and can be transmitted to humans. Interestingly, S. hominis has been not been reported in the U.S., but may be found in beef from many other regions, including Europe.

Congratulations to Dr. R - the only one to get this correct (I told you it was tricky!)

Case of the Week 24

Here's another video from the wonderful world of entomology.
These tiny little things regularly crawl on us. Yes, even if we shower regularly.
Identity?
What disease is associated with them?

Answer to Case 24

Identity?
Ian got this one - these are Dermatophagoides mites (House Dust Mites)
These microscopic mites are in our soft furnishings (especially our beds), feeding on our shed skin flakes, and depositing feces. It is the feces that can trigger an allergic reaction in susceptible individuals.

What disease is associated with them? The allergens in house dust mite feces can trigger asthma, eczema, perennial rhinitis.

Case of the Week 23

The following worm was extracted during endoscopy, where numerous similar worms were seen attached to the large intestinal mucosa. The worm measures approximately 40 mm. CLICK ON IMAGE TO ENLARGE.

Diagnosis?
Images were taken at the London School of Hygiene and Tropical Medicine and shown with Permission.

Answer to Case 23

Answer: Whipworm (a.k.a. Trichuris trichuria)

Note the small head wrapped around the body. The size and location are also important clues.
Good job Alasdair and Heather!

Case of the Week 22

Alex made the following movie for me, based on some footage I took during my daily commute. Caution: contains music; Turn your speakers either up or down!



Questions based on the movie:
1. List 5 infectious diseases spread by mice.
2. Mice can act as reservoirs for which parasitic infections?

Answer to Case 22

I had specified 'mice' for this week's questions, but I should have generalized it to rodents, since there is considerable overlap among the various disease-carrying species.

Tom made a great start in answering the questions. I will elaborate below. Keep in mind, this is just a list of the more common diseases - there are many more!

1. List 5 infectious diseases spread by rodents:
Tom says:
1. and 2. Rat bite fever (Streptobacillus moniliformis, Spirillum minor)
3. Hanta virus
4. Lymphocytic choriomeningitis
5. Plague & Leptospira
6. heebie jeepies (right Pritish?)

Here are some other diseases:
Viral:
Lassa fever, Argentine hemorrhagic fever, Venezuelan hemorrhagic fever, hemorrhagic fever with renal syndrome, Venezuelan equine encephalitis, and tick-borne encephalitis.

Bacterial:
Rocky mountain spotted fever, Boutonneuse fever, scrub typhus, murine typhus, tick-borne relapsing fever, Lyme disease, and salmonellosis (with S. typhimurium)

2. Rodents can act as reservoirs for which parasitic infections?:
Babesia
Toxoplasma gondii (named after the African rodent it was first described in, Ctenodactylus gundi)
Chagas disease
Cutaneous and visceral leishmaniasis
Echinococcosis (E. multilocularis and E. vogeli)
Angiostrongyliasis
Schistosomiasis (with S. japonicum)
Hymenolepsis (Both H. nana and H. diminuta)

Tom also gave us the following:
"Just remember, these rhyming species carry lots of nasties: rats, bats, & cats (not sure about wombats...)" Although, 'man's best friend' doesn't get off the hook either - more on this in a future case of the week...


It is important to note that rodents can spread disease in a number of ways: the infectious organism can be excreted in urine and then be inhaled following aerosolization (e.g. Hanta virus) or ingested (e.g. Leptospirosis), or the organism can be directly inoculated through a bite (e.g. rat bite fever). Vectors can also be involved such as fleas, ticks, mites, mosquitoes, sand flies, and reduviid bugs. Finally, rodents may harbor a stage of the disease that is not directly infectious to humans and must first be transmitted to another non-human host (e.g. echinococcosis).

Case of the Week 21

Did you know you can leave a message using the 'anonymous' feature? Feel free to leave a comment!

The following cyst is seen in this iodine stained wet-preparation from stool. It measures 16 microns in diameter.

Diagnosis?
What is the significance of finding this organism in this sample?
CLICK ON IMAGE TO ENLARGE.