ø¤º°* Medical Microbiology Winter 2006 Club*°º¤ø

moonischasingme1 · Mar 14, 2006

We're starting our unknown project this morning in lab. Should be interesting with lots of chaos. I hope my lab partner dropped over spring break.

Columnist · Mar 14, 2006

Stpauligirl, thanks for your help with my question about the lab report. We don't start our unknowns until a week from Thursday, so I'll keep everything you said in mind.

Do we track the information in our notebooks and then have to prepare a typed report to turn in? (I realize that is more of a question for my instructor -- duh!) What I mean is, is this the common way of doing things?

We do not have to do an oral report, as far as I know. Thank goodness! It's not that I am afraid of public speaking, it's just that I don't want the hassle! :lol2:

Columnist · Mar 14, 2006

I'm still having difficulty with the whole Selective and Differential thing. Can anyone help out? Why is Mannitol Salt Agar both selective and differential? Any helpful sites? Thanks!
:smackingf

Kathyz, maybe this will help...

"Selective" relates to categorizing a bacterium, overall. Let's say you have a group of bacteria called "marbles." Within this large group are many different types of marbles: some are blue, some are orange, and some are orange with green swirls. A selective test will only allow SOME of these marbles to pass to the next round of choosing. Let's say our selective test is a funnel with a particular size hole. The orange marbles are smaller in diameter than the blue ones, so only the orange marbles (solid and swirled) pass through the funnel.

In this case, our test has "selected" the orange marbles. The blue ones are exlcluded.

"Differential" relates to categorizing bacteria within their subset. So, after our selective test, we're left with a subset of two types of marbles: solid orange and swirled. We want to separate the swirled ones from the solid ones, so we use a differential test. Let's say our differential test is a medium that can somehow make the swirled marbles glow in the dark. We put all the marbles onto this medium. After the test, the medium still contains ALL of the orange marbles, but only the swirled ones glow in the dark, which allows us to identify them.

Specific to MSA, it is selective because it categorizes bacteria into salt-tolerant and non-salt-tolerant subsets. In other words, bacteria such as streptococcus, which cannot tolerate a salty environment, will not grow on an MSA plate. Staph, on the other hand, CAN tolerate a salty environment, so it will grow on an MSA plate. Hence, MSA "selects for" salt tolerance.

However, "salt tolerant" encompasses a group of many different strains of staph bacteria (the "subset"). The "differential" aspect of MSA categorizes these subsets based on their ability to perform mannitol fermentation. So, you might put three strains (subsets) of staph on an MSA plate. All will grow, but only the one that performs mannitol fermentation will change the pH of the medium, thus giving a positive reaction.

I hope this helps and doesn't confuse you even more! :uhoh3:

Columnist · Mar 14, 2006

We're starting our unknown project this morning in lab. Should be interesting with lots of chaos. I hope my lab partner dropped over spring break.

:lol2: :lol2: :lol2:

I feel your pain.

My lab partner is a complete airhead. I have to spend so much time just going over what the instructor said TWO MINUTES AGO ("Did he say we each take a plate, or do we only get one plate per group?") that I get precious little time to actually DO THE EXPERIMENTS!

Ah, well. Before we know it, it will be over. Good luck on your unknown!

stpauligirl · Mar 14, 2006

Stpauligirl, thanks for your help with my question about the lab report. We don't start our unknowns until a week from Thursday, so I'll keep everything you said in mind.
Do we track the information in our notebooks and then have to prepare a typed report to turn in? (I realize that is more of a question for my instructor -- duh!) What I mean is, is this the common way of doing things?
We do not have to do an oral report, as far as I know. Thank goodness! It's not that I am afraid of public speaking, it's just that I don't want the hassle!

Our teacher gave us a report sheet where we will record everything that she wants us to report about for our unknown. the sheet has a list of tests that we need to do. I am surprised that your teacher isn't issuing a report sheet for you guys. I can send you a blank if you like, just think how much you would impress your teacher!!!!

Maybe she waits until you actually start to give you guys more direction.....it seems messed up to me.

Definitely keep track of everything you do with your unknown in a notebook. Even if you dont think something is significant.

Good luck and wait and see what happens when you get started, I am here for you if you need me.

Columnist · Mar 14, 2006

Our teacher gave us a report sheet where we will record everything that she wants us to report about for our unknown. the sheet has a list of tests that we need to do. I am surprised that your teacher isn't issuing a report sheet for you guys. I can send you a blank if you like, just think how much you would impress your teacher!!!!
Maybe she waits until you actually start to give you guys more direction.....it seems messed up to me.
Definitely keep track of everything you do with your unknown in a notebook. Even if you dont think something is significant.
Good luck and wait and see what happens when you get started, I am here for you if you need me.

Well, I just looked at the syllabus ( :idea: ), and it says the entire next lab-lecture is about how to do the lab report. Der.

Today, I finished my flowchart for my unknown, so at least now I have the roadmap for what I need to do. Should be a cakewalk, right? Right??

stpauligirl · Mar 14, 2006

Well, I just looked at the syllabus (), and it says the entire next lab-lecture is about how to do the lab report. Der.
Today, I finished my flowchart for my unknown, so at least now I have the roadmap for what I need to do. Should be a cakewalk, right? Right??

Well,I am glad that you found the info, good luck and remember I am here if you need help

Kathyz · Mar 14, 2006

Ladies, I feel your pain. Unfortunately I'm one of those airheaded lab partners. I swear my teacher doesn't explain things well. Or maybe it's just my age. Fortunately for me I received an A on my first lecture exam so I think my partner saw it and gained some respect for me. Up until then she was kind of 1/2 and 1/2 about me. I'm always relying on her; poor girl.

Semi, thanks SO MUCH~!! Your marble analogy was great. Sometimes I forget that what we're trying to do are learn various methods to identify our unknowns once we receive them next month!! First test: gram stain. Got that one down. My head is usually swimming with organic chemistry and not biology!!

Just did a big report on prions, v-CJD and Mad Cow. Earned some points my having cute pictures on my transparencies. Pretty scary stuff. A recent cow was just diagnosed in Ohio I believe. Stay away from eating the brains and we'll all be OK.

ChristineN, BSN, RN · Mar 15, 2006

Hi, my school is on quarter's so I'll be starting Microbiology the week after next. I just finished A&P II and am looking forward to a new challange! :specs:

Nurse-To-Be-Joy · Mar 15, 2006

Hi, my school is on quarter's so I'll be starting Microbiology the week after next. I just finished A&P II and am looking forward to a new challange!

Good luck! Read back throughout this thread and you will find some great Micro resources.

ChristineN, BSN, RN · Mar 15, 2006

Good luck! Read back throughout this thread and you will find some great Micro resources.

Thanks Joy, I'll be sure to do that!

KellyC · Mar 16, 2006

Hi everyone. I have not posted in a while.

Medmic, A&P2, and my job are keeping me busy. But thank God I am almost done. I just finished med mic lab practical this morning and also last lecture test in A&P. The lab practical was tough, we saw a little bit of everything from parts of microscope, to antimicrobial testing(zone diameter measurement), to M/O under the microscope and then the different selective and differential media and the gram neg flowchart and the the diff media that go with it and coagulase test and so on. Phew!

We had 16 stations and 50 questions.

I am doing well in A&P2 I have a high A. but man oh man in med mic i am strugling. I got an A on the first lecture test but from then on i'd been getting Bs and most of the class is getting C's and Ds( we had 4 tests so far). The prof is hard. He says if it's in the book then it's just fair that he could put it on the exam. He does have web notes but very general. Each exam is comprised of 4 chapters.

A&P2 just comes easier for me I guess than Med mic. A lot lot more stuff in medmic. BUt I enjoy the medmic lab though. I have an A avg and I think I did pretty well on the lab practical. BUt I calculated my grade and even if I make a perfect score(yea right, I doubt that I would even make an A) on the final I still would not get an A. Guess a B will do, but who does not want an A.

I read the other posts and well done for all of you who are getting A's in Med mic. It's a difficult class. And good luck to all of us. I know for some of us the final is just around the corner. Hang in there. I am.

I'm still having difficulty with the whole Selective and Differential thing. Can anyone help out? Why is Mannitol Salt Agar both selective and differential? Any helpful sites? Thanks!
:smackingf

Hi. Hope this helps.

MSA is selective for gram+ bacteria which means only gram+ ones will grow on the media. It's differential because it differentiates between pathogenic staph aureus and non-pathogeninc staph epi.