Thursday, April 27, 2017

Answer to Case 444

Answer: not a parasite; most consistent with banana seeds.

This is something that we commonly see in my lab, and I've previously featured other examples of banana seeds on this blog. Here are the links to 2 previous posts:
Case 139
Case 402

Because I've received some degree of skepticism when I've posted banana seeds in the past, I decided to conduct an experiment to see if I could recreate their appearance through some laboratory digestion techniques. So here was my process:

Step 1. Sacrifice my banana from lunch for the good of science

Note the small immature seeds that are seen in these longitudinal sections. A fun fact - the bananas that we buy in the grocery store have been bred so that the seeds never mature. Wild bananas have large seeds which make the fruit less pleasant to eat.

Step 2. Add bananas to pre-prepared tubes of proteinase K in buffer. (Unfortunately I didn't have any amylase which would have digested the carbohydrates in the banana. However, this was the best I could do to simulate the digestive process). Vortex to mix and then incubate at 56 degrees Celsius while gently shaking (the standard tissue digestion that we use for PCR pre-processing).

Step 3. Check regularly. I first checked every 10 minutes , but very quickly realized that this was going to be a long process. After the first 4 hours, this is how the banana sections looked:

Step 4. Check again, 24 hours later - looking pretty good!
Step 5. Final check - 48 hours. Success! I think that these look nearly identical to our clinical specimen. What do you think?
Close-up view of the seeds (look a lot like the previous cases):

Again, it's not a perfect match since the actual patient specimen was subjected to the entire gastrointestinal digestive process. However, the strings of immature seeds can clearly be seen. Here is how they look microscopically:
You can also appreciate the starch granules of the banana (taken using a 40x and 100x objective):

I hope you all enjoyed this experiment as much as I did!


Anonymous said...

Bobbi you are awesome! This made my day! Of course, you took your banana and replicated the mimic. Love it!!!

Kawsar Talaat said...

That is fantastic! Thank you for the scientific proof!

infectiologue said...

Just closed an email to someone with delusional parasitic infection, another set of 8 pictures.

Thanks for showing this fantastic example!


Kevin Barker said...

This is amazing Bobbi! A true parasitologist! Thank you so much for sharing!

Sugar Magnolia said...

Now that's REAL science! Love it!

Roshan Nagar said...

Good idea..

Anonymous said...

So much fun and you do have amylase in your lab -- it's called spit. Old time histotechs have known for years and used as diastase instead of commercial reagents.

Bobbi Pritt said...

Too funny! And you're right of course - I could have used some good old fashioned salivary amylase. However, it probably would have taken me a while to generate enough, and I'm guessing that I would have gotten a fair amount of bacterial overgrowth if I conducted the experiment over ta 48-hour period.

The alternative that I was going to try if my first experiment didn't work was to get some amylase from our histology lab. They routinely use us in the periodic acid Schiff stain.