transco
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i just started the micro section for kaplan yesterday, and its not all that great! i realize that its just straight up memorization, but does anyone have an ideas on makin it easier? it seems like i learn one thing and after i've learned another thing, i forget the first things i learned. argh! so frustrated right now!!! :| :x
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| bm
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try the physiology section of kaplan  or brs if you have it. bugs are easier to memorize and easier to forget. i'd say do it at the end of your review.
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| bactitech
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As a medical microbiologist, we have to know the schemata cold. I suggest separating out the gram positive from the gram negatives first.
Then, take the gram positives and break them down into catalase positives and catalase negatives (cocci). Catalase pos = Staphylococci. What differentiates these? Coagulase production. S. aureus=coag pos. S. epi (now known as coagulase negative staph in most clinical reports) = coag neg.
Then break down the strep by hemolysis: beta=Group A (Strep pyogenes),B (S. agalactiae),C,F,G. The alpha streps=S. pneumo, viridans streptococci. The gamma streps = enterococci and Group D non-enterococci.
Catalase is the big splitter of the cocci. You go down the line from there.
With gram negative rods, they either ferment glucose or they don't. With the fermenters, they're either lactose positive or lac negative. We report out all preliminary GNR's by their lactose reaction, if possible.
Lactose negative rods can be either oxidase neg or pos. The oxidase negs are MOSTLY fermenters, and the oxidase pos ones are mostly nonfermenters.
If you draw out a chart for yourself on paper, with gram pos on one chart and gram negs on the other, it will begin to make more sense.
If anyone needs any more help understanding micro, let me know.
I tell new techs that it will take them a year to feel comfortable reading plates.
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| Malaysian
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bactitech.....I wanna learn more from you!!
Can you help me out on the bacillus bit(mainly the enterococci)how to remember those......I would appreciate the explanation above regarding the gram negative to be completed......the cocci bit really helped.Thank you for your time.
Also is your knowledge in viruses/parasites just as good?Thanks once again.
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| bactitech
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I am confused by your response. Enterococci are....cocci, not a bacillus. They are gamma hemolytic (i.e. no hemolysis), catalase negative (as are all streptococci) and appear gray on a plate. They are one of the most difficult organisms, for some reason, for new techs to learn as far as morphology. Enterococci are Group D streptococci. All group D's turn bile esculin positive. However they are split off from other Group D strep by a rapid reaction we do on a disc called a PYR disc. Enterococci are PYR positive. This enables us to tell the doc right away it's a Group D and not wait overnight for a bile esculin reaction. The old schemata was to sub the suspected enterococci colony to a BE and a 6.5% salt broth and incubate overnight. Enterococci are BE+ and grow in 6.5% (high concentration) salt broth. Group D non-enterococci are BE+ but do NOT grow in 6.5% salt broth. The strep are very complicated when it gets into the different type of viridans strep so I'm not going to go any further about those.
Lactose fermenters are almost all glucose fermenters and are mostly oxidase negative (with the exception of Aeromonas sp. - but all of those aren't necessarily lactose fermenters...there is always an exception in micro). The old way of identifying these organisms was by the ImVic reactions (indole, motility, VP, methyl red, citrate I think). Anyway, back in the 70's, when we used real media instead of automated cards for identification, we would set up SIM (for H2S, indole, and motility), citrate slant, ornithine, lysine (the decarboxylases), and VP broth and incubate overnight. Depending on the reactions, we would key out the lactose fermenters.
Nonlactose fermenters that are oxidase negative got more media. We added arginine decarboxylase, raffinose broth (I think - it's been a long time), OF glucose, urea slant, PAD slant, and a DNAse plate (for Serratia sp.). Ferric chloride is added to the PAD - it turns dark for a positive reaction. Again, depending upon the results of these reactions, we could key out the majority of the nonlactose fermenters. We use API now for a backup method if our automated method doesn't work. It has essentially the same reactions in a strip that is inoculated and incubated overnight. Reagents are added and the results numerically keyed out.
Non-lactose fermenting gram negative rods are a whole other ballgame. These are sometimes oxidase positive but can be oxidase negative. An oxidase test should ALWAYS be performed on any nonlactose fermenting colony, but it must NOT be performed off MacConkey agar. It must be done off a nonselective medium. This is a critical reaction and your setup schemata depends upon it.
I'm not sure how far you want me to go. This is obviously a complicated subject. Just reading about it can be confusing. If you have time (ha ha) just go to your hospital's micro lab (best to call first) and they'll be glad to show you around. It makes more sense if you see some of this stuff.
Again, it takes at least a year of working with this stuff on a daily basis to get comfortable with it. There are always exceptions. Sometimes one must go for "best fit". Sometimes bugs must be sent out to state laboratories and ultimately the CDC for identification.
I've read more O&P exams than I want to admit over the years, although we aren't doing them on our shift now (thank goodness). The most common parasite in the US is Giardia lamblia. Unless the patient has a travel history outside the US, you are better off ordering a Giardia antigen test than a whole O&P examination. The last two positives I saw that were something other than this (outside of surveys, which we must do biyearly) were from a child that was in for surgery from Guatemala (Trichuris trichuria) and a child from a Romanian orphanage who was being adopted by a couple here in the US (remember all the Romanian orphans in the 90's?). This poor child had at least 3 parasites. Most of the WORLD's population carries parasites in undeveloped countries. The most important thing in parasitology is to MEASURE what you think is a parasite. If the measurements don't add up to what you think you are looking at, it's not it. Also, it's difficult for a novice to pick out parasites from all the junk in a stool. You just have to train your eyes to see it. After a few hundred exams, it gets easier :-(.
I've never worked in Virology, so I don't know much of anything about that subject. That's a whole other ballgame.
Hope this helps.
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Thanks bactitech....it surely helped me orient myself!!
What has your expereince been with malarial parasites(plasmodium) and babenesia(I've never come across this parasite before yet its occ. tested on the exam)
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| bactitech
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I've only seen Babesia on a survey. We are not in an endemic area for this organism. We surely do not see a lot of orders for malaria in NW Ohio. However, we did have a positive about a year ago from a child that was traveling with a musical group that originated from Africa. There were parasites EVERYWHERE on the slide. One of our techs worked in parasitology for 2 years at Cleveland Clinic. She was able to speciate it pretty quickly, but our microbiologist (Ph.D.) had to come in and check it before it went out. I would have had to look in books, debate, and still have it checked out. These are always good learning experiences for us as they come up so rarely. We only get a couple orders a year for malarial parasites, and they usually go through the Hematology department first, as they make the slides.
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Can you give me more info. on this babenesia case....what eaxctly did you see on the slide?
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| bactitech
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It's not babenesia - it's babesia.
http://www.cdc.gov/ncidod/dpd/parasites/babesia/d...
http://www.biosci.ohio-state.edu/~parasite/babesi...
I don't remember a thing about the survey - it was quite a few years ago. Hope the links help.
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Thanks for the links and correcting me.
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