Microbiology unknowns

[LPN709]

So our class is scheduled to do our micro unknowns in a couple of weeks. I've searched for some threads on here about the subject but they all seem to be several years old so i'm starting a new one.

I'm very worried. The threads I read talk about all of these tests to run on the unknown like citrate, urease, starch hydrolysis, etc. I have no idea what any of these things are. We were only taught how to do a negative stain, simple stain, and just last week a gram stain. So all we've been taught is how to identify the shape, arrangement, and gram status of the organism...I'm really worried it seems odd my teacher isn't teaching us all of the things that all of you here on AN say is just common knowledge in microbiology. Am I worrying to much and should just concentrate on why my teacher is showing us in lab? I'm so lost and don't know what to do I appreciate any responses!!

[akulahawkRN, ADN, RN, EMT-P]

While I'm not going to say that you shouldn't worry, I will say that your professor will not be able to give you the "unknowns" exam until you've been presented with, and performed, the tests necessary to identify all the "critters" in your unknowns. Just shape, arrangement, and gram status will help narrow things down quite a bit. Microbes will tend to grow better under certain conditions... and they're all listed in a "book" that you should be able to reference.

A few years ago, I was in similar shoes as you... I was very concerned that I wasn't going to be able to identify the unknown organism. Well, we learned a few more ways to test the organism's various properties and then one day, we got our unknowns and we got started. Trust me, you won't need to do a "shotgun" approach where you use every test known... you'll start with looking at your organism and then you'll select your first tests that you can run right then to narrow things down and you'll put the stuff in an appropriate growth media. You'll be referencing the tests as you go along, which will help you select the "next" test.

In my case, I was able to tentatively ID the unknown in about 3 tests, but I ran a couple more tests to confirm my findings, and I was able to do it because I had the time.

The hardest thing to do is ensure that your don't inadvertently contaminate your "unknowns" sample, especially early on.

This is totally doable and you'll be taught the skills needed to make the ID. It truly won't be some random bug... it'll be one that is very well known to your instructor.

[NCH, RN]

My class went through the same thing, we learned all of the test plates and tubes during our unknown.

It's really not that bad, you just perform transfers, streaks and stains, then identify the changes in appearance or mobility in the different plates, you also identify shape and arrangement. Once you have all of the information, you then compare it and match it with a chart.

[dorkypanda]

The unknowns project was fun. do the tests you need to do and write down your observations clearly for your note taking. by looking at results you can detect which you may have and which you don't have. If you're confused maybe re do a test if time permits to confirm your thoughts. And also make sure to make new batches of your separated unknowns just in case something happens to your current supply. this is a good thing to do because you'll have extra material to work with. I've heard stories from my professor saying someone dropped their test tube and they made a backup of separated unknown.

[SopranoKris, MSN, RN, NP]

Unknowns was my favorite part of Micro. It's like solving a mystery :)

Make a flow chart and use the tests you know to eliminate organisms and narrow down your answer.

A. Gram stain - gram negative or positive?

B. Bacillus or cocci? Strep? Staph?

C. Once you've determined Gram +/- and shape, then try to grow your organism on different media - selective (e.g. mannitol salt agar), differential (e.g. EMB, McConkey's, etc.) and possibly enriched (e.g. blood agar for strep)

D. You can also do differential tests in test tubes (e.g. nitrate broth, MRVP, etc.)

Here's a great link that explains all the selective, differential & enriched tests you can do: Microbiology Lab : MOLB 2210

BTW, our professor gave us extra points if we identified using the least number of tests possible for that organism. Take a judicious look at the tests. If your organism is a Gram positive cocci, you're going to the skip the tests for E. coli (Gram negative bacilli), get it?

Good luck!

[Kuriin, BSN, RN]

The unknown aspect of Microbiology lab was exciting, unnerving, and fun. Because it is your final project, you are given a specific amount of time to find it.

Try doing it color blind. Purple and pink are pretty much the exact same. I had my unknowns isolated for two weeks without me knowing until I had my teacher and several students tell me, "it's isolated". lol...

[Sizzline]

When we did our unknown, we took several lab periods to accomplish it. We spent an entire lab period doing practices of the different tests, and reading the results of tubes/plates that had been prepped for us and seeing what they meant. A second lab period was used to do the tests on our actual unknown, and then a third and final one was reading the results for it and making an identification. The lab report was due the following week.

[studentnursemon86]

We had almost half the semester to work on ours. Our lab instructor gave us our unknown and there were lab handbooks with all of the tests and how to do them.

It also told is which test to do next based on the results of the current test we were doing.

It was pretty straight forward. I got 100% on mine :)

I hope yours is similar. It was probably my favorite lab pre-nursing.

[LPN709]

I had my unknown today and I made a 100% on mine. I'm so excited :) I guess I was worrying too much. Thank you all for your advice!

[akulahawkRN, ADN, RN, EMT-P]

Good job!!

[studentnursemon86]

Congrats!

[LPN709]

Good job!!

Thank you! :)