Microbiology unknown - Neisseria tests?

[lovesbunnies]

Hello everyone,

I am starting nursing school this fall, and I am currently finishing my last two pre-reqs this summer.

We are working on our unknown project in microbiology, and so far I've been able to determine that my organism is a gram-negative cocci. So far, my research has revealed that gram-negative cocci are rather uncommon, and I most likely am dealing with a species of Neisseria bacteria.

It looks like the best way to determine whether I'm dealing with a Neisseria bacteria is to look for a positive result from an oxidase test, which I will do tomorrow in lab. However, as part of the project, we are required to perform three media tests with positive results, and I haven't been able to find much information about which media tests can be used with Neisseria. So far in lab, we have practiced with EMB, MIO, TSI, BAP, mEndo/mFC, and tests for various enzymes (citrase, coagulase, catalase, urease, lipase, oxidase). (I omitted the selective media for gram-positives, since I know I won't need to use those.) Aside from the oxidase test, which I will be doing, would any of those other tests give me any relevant information?

My professor has said she will help us with tests that we haven't practiced in lab yet if we need to use something else. I am seeing that Thayer-Martin agar (?) is commonly used for Neisseria species (but only for N. gonorrhoeae?), so I'll ask her about that tomorrow. I've also read that Neisseria species grow well on BAP, but they don't lyse RBCs, so that would be a negative result and I'd have to run another test anyway (in addition to possibly getting points deducted). I have also read about Cystine Typticase Agar being used with Nesseria, so I will ask about that.

If it helps at all, I obtained my organism by swabbing around the drain of a drinking fountain. (Our professor didn't assign organisms to us--we started off by swabbing a surface of our choice and then we selected a colony from what grew on our plate.)

I feel like I crammed a lot into this post, but if you read it and can offer any insight on what tests I should do, I would really appreciate it! Thank you!

[Golfer87]

You need to use a Dichotomous Key. It helps determine identification between to Gram Negative or two Gram Positive bacterium.

[NurseGirl525, ASN, RN]

Are you not required to use a dichotomous key? We had to. I'm thinking you are not going to find gonorrhea around a drain of a drinking fountain. You should have performed all the tests you need throughout the semester in lab. Our instructor did not help us at all. Most classes you are pretty much on your own with the unknown. Using the key will help you a lot.

[Golfer87]

Are you not required to use a dichotomous key? We had to. I'm thinking you are not going to find gonorrhea around a drain of a drinking fountain. You should have performed all the tests you need throughout the semester in lab. Our instructor did not help us at all. Most classes you are pretty much on your own with the unknown. Using the key will help you a lot.

My instructor was excellent, as well as the textbook and Mastering.

I came upon the key by chance after banging head trying to prove identification of my isolate.

We were never told to use a dichotomous key. Yes it was helpful.

[lovesbunnies]

I don't remember my professor mentioning a dichotomous key at all. We just practiced the tests I mentioned in my first post, and then we started our unknown project. I tried to do a little research on dichotomous keys and all I was able to find was that a positive oxidase test would indicate a Neisseria species. I haven't been able to find anything about what media to use for identifying gram negative cocci, and I need to have three positive media results for my lab report. It seems like the more research I try to do to figure out what my next steps should be, the more confused I get. :\

[NurseGirl525, ASN, RN]

We did ours at the end of the semester after we had done all of the testing labs. With a key, you will start at whether it is gram positive or negative, then whether it is a bacilli or cocci, then you go from there. I don't see how you can do this by just guessing which is basically what you are doing here.

A dichotomous key it what a microbiologist would use to help them identify what kind of bacteria they are dealing with. Say there was contaminated water and the microbiologist needed to identify what it was so they knew what kind of treatment to give to those who were sick or to simply know how to eradicate it from the water. That is kind of what you are doing here. Just trying to look up all gram negative cocci bacteria is not going to help you. You need to perform the other tests so you can determine what it is. Whether it's a citrate, oxidase, etc, these need to be performed. Not just random tests you may think give you a positive result. Then as you get your results whether they are positive or negative, you plug them in the key to determine what the bacteria is. You are trying to determine your unknown from 2 tests. It's not really possible to do that.

[lovesbunnies]

That helps a lot, thank you. My professor did say that our tests would lead us down a "path" to identifying our organisms, but she didn't give us much more information than that, so I was feeling kind of lost. I think I have a better idea of how to move forward with my tests now.