mjl1717
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which bacteria are motile beside proteus, salmanella, listeria and treponema (spirochete)?
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| yasmeen
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listeria has tumbling motility
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| whitmer
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Escherichia, Enterobacter, and Serratia. 
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| bactitech
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It's easier to learn the big nonmotile ones - Klebsiella pneumoniae, Shigella sp., Bacillus anthracis. Those three come to mind although I'm sure there are others. Most of the Enterobacteriaceae are motile organisms. Why are you memorizing motility lists?
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| mjl1717
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because I never know what angle usmle will come at me on exam. if they use the word "motile" that will help me r/o certain species. Thank You
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| bactitech
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I didn't mean to come down hard on you. I know you have LOTS of material to cover in a short amount of time. When we teach MT students microbiology, we go more by the big splits. With gram negative rods, it's oxidase positive vs. oxidase negative. With gram positives it's catalase positive vs. catalase negative.
Once you get into ox negative Enterobacteriaceae, then you have other splits. Remembering the few that are non-motile is a much easier way to go as there are lots fewer of those. If you need any other help feel free to PM me.
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| study_ing
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thanks bactitech. ive always found micro overwhelming. that helped. cud u please suggest where such clues are given regarding enterobacteriace
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| mjl1717
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bachtitech has stated that one of the test to do is lactose fermentation. {I notice that some books even break it down into fast and slow lactose fermenters}
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| bactitech
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Gram negatives are divided into lactose fermenters and nonlactose fermenters. There are some "slow" lactose fermenters (Acinetobacter calcoaceticus baumanii comes to mind - this is a very problematic sometimes nosocomial pathogen in hospitals that can get very resistant). Gram negatives are also oxidase negative and oxidase positive. MOST lactose fermenters are ox negative (Aeromonas sp. can be a lactose fermenter that is ox positive, however). Some nonlactose fermenters are oxidase positive and are glucose oxidizers, or glucose nonfermenters. The lactose fermentation helps you differentiate gram negatives on MacConkey agar, which will show LF's as purple colonies with various morphologies, and NLF's as clear colonies with various morphologies. When we teach MT students we try to point on the various morphs. I've been doing it long enough I can pretty much tell what they are by morph and smell, but if the colonies are small and there are mixed morphs I can't always tell what they are. We must sub them out one colony morphology at a time and then run ID's/sensis on them. This is why microbiology results take some time. Every subculture takes a day. Some ID's take more than one day. If there are problems with ID's sometimes the bugs must be sent to a reference laboratory. Nothing is cut and dried.
Klebsiella/Enterobacter group organisms are VP positive (Voges Proskauer). However, the Klebs are nonmotile and the Enterobacters are motile. Kleb. pneumoniae is indole negative; Kleb. oxytoca is indole positive. Kleb. pneumoniae is lysine decarboxylase positive, ornithine negative.
It comes down to rote memorization if you must know the truth. When I started micro in 1974, the lab I worked in still used conventional media. After setting up biochemicals day after day and reading them out, you get to know your reactions pretty well. We had a "short" bio for lactose fermenters, and a "long" bio for nonlactose fermenters.
Short - SIM (H2S/Indole/Motility), citrate agar slant, Lysine, ornithine, VP.
Long - OF dextrose (oxidative/fermentative), citrate, urea, PAD (phenylalanine agar), SIM, lysine, ornithine, arginine, VP, raffinose [I think - it's been a long time, could have been another sugar though], VP, DNAse agar.
These media will pretty much ID the majority of the Enterobacteriaceae. SIM and OF Dextrose are stabbed once. If motile, the growth will be diffuse in SIM, if nonmotile, you will see a straight line of growth with no diffusion. H2S turns the medium black. Indole reagent is dropped on top - if it turns pink it's positive. OF dextrose is yellow all the way (starts out green) if glucose is fermented. If oxidized, it will be yellow at the top only, if a nonfermenter, it will stay green.
The MT registry has questions on media reactions and plate media. I tell the students to know their reactions cold going in. I have no idea whether you're required to know all these reactions or not.
What are the two swarming Proteus sp? P. mirabilis and P. vulgaris. PMIR is ornithine pos and indole negative. PVUL is ornithine neg and indole pos. They are both Urea pos and PAD pos. This is the type of stuff we have to know. Nowadays, automated equipment like VITEK does our ID's for us in micro wells on cards. It's more difficult for MT students nowadays to learn these reactions because they don't get visuals from tubes any more.
You need to sit down with a micro chart on the Enterobacteriace and look at it closely.
I worked tonight so must shut down for now. Any specific questions, you can PM me :-). I can't help you with general global questions such as "how do I study micro" though. :-)
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| frontal
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bactitech: great post. 'Medical Microbiology-31 years'- what does it mean?
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| mjl1717
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probably means she's been outstanding in the carreer for 31 years
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| bactitech
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I don't know about "outstanding" but I've been a registered medical technologist since 1974. All but about five years of that have been spent in microbiology. I've worked exclusively in micro since 1988. I now work at a large "integrated" facility. We do the micro work for four hospitals, including the local medical school. We see LOTS of stuff!
Thanks for the vote of confidence, though
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| frontal
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Which probably means you're out here to help and not to prepare for the exam. Thank you for your presence.
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