asmi
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name them ?
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| crista
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stafilococus aureus
pseudomonas
klebsiella
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| asmi
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staph. aureus , pseudomonas , enterobactericeae
also candida, aspergillus
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| anne
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staph.aureus,epidermidis,saprophyticus(all staph)
klebsiella and pseudomonas are i guess oxidase +ve(possess cytochrome c).i'm not sure if they are cat+ve.
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| crista
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all strept. are catalaso negative
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| krsma
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Catalase + :
-All species of genus Staphylococcus
-Family Enterobacteriaceae (which includes Citrobacter, E.Coli, Enterobacter, Klebsiella, shigella, yersinia, proteus, salmonella, serratia)
Oxidase + :
-Neisseria
-Pseudomonas
-Vibro
**I didn't find anything about any fungi, but i'm sure asmi is right about candida and aspergillus.
but I'm not sure about Pseudomonas ??? but I'm sure everyone is right about that also
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| asmi
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what is the importance of catalase test / enzyme ?
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| krsma
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CATALASE TEST
Some bacteria and macrophages can reduce diatomic oxygen to hydrogen peroxide or superoxide. Both of these molecules are toxic to bacteria. Some bacteria, however, possess a defense mechanism which can minimize the harm done by the two compounds. These resistant bacteria use two enzymes to catalyze the conversion of hydrogen peroxide and superoxide back into diatomic oxygen and water. One of these enzymes is catalase and its presence can be detected by a simple test. The catalase test involves adding hydrogen peroxide to a culture sample or agar slant. If the bacteria in question produce catalase, they will convert the hydrogen peroxide and oxygen gas will be evolved. The evolution of gas causes bubbles to form and is indicative of a positive test.
OXIDASE TEST
Cytochrome oxidase is an enzyme found in some bacteria that transfers electrons to oxygen, the final electron acceptor in some electron transport chains. Thus, the enzyme oxidizes reduced cytochrome c to make this transfer of energy. Presence of cytochrome oxidase can be detected through the use of an Oxidase Disk which acts as an electron donator to cytochrome oxidase. If the bacteria oxidize the disk (remove electrons) the disk will turn purple, indicating a positive test. No color change indicates a negative test.
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| asmi
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thanks
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| Cedrick
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A posteriori
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| bactitech
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An important test for the ID of Listeria is catalase. It is positive. The morphology of Listeria and Group B Strep (Strep. agalactiae) is similar on a plate. However, Listeria is catalase positive and is a gram positive rod, whereas Group B strep is catalase negative and is a gram positive cocci.
One doesn't see Listeria very often, but this is a very important test to remember for this organism.
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| DrVirgo
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Bactitech,
Thanks for all your explanations.
do you have some kind of chart/flow sheet with all this information?
I think it would be a good idea to break down the organisms like this
catalase + and - then oxidase, urease, etc...
Thanks
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| study_ing
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wil really appreciate that bactitech
as well as ur opinion on pseudomonas
well there is also clinical signifance of being catalsae positive. in CGD, these organism are likely to cause infections whilst catalase negative do not
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| bactitech
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Micro people don't memorize organisms by one reaction. They study the gram negs as a group and learn about them; they study the gram pos as a group and learn about them, etc. etc.
It is easier to learn about families of organisms than lists and lists of bacteria by one reaction.....
Organisms can cause infection regardless of catalase reactions, i.e. Group A Beta strep, which is catalase negative, and can be "flesh eating." Please get this idea out of your head because it's not true.
BTW, what is CGD????
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| DrVirgo
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CGD is Chronic Granulomatous Disease.
Its a lack of NADPH oxidase, so no respiratory burst.
Patients are usually kids who get recurrent infections with catalase positive organisms.
Thanks for the advice bactitech... I am memorizing/studying the organisms like you said, however its good go have a summation/review for final quick studying.
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| bactitech
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http://www.cgd.org.uk/
http://www.emedicine.com/DERM/topic719.htm
Yes, in this one RARE disease, catalase positive organisms are the villain. However, the chances of your seeing this disease in your lifetime is.....well....RARE. It is a zebra, not a horse.
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| mjl1717
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thx.-- actually that disease is of significance for step 1
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| bactitech
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I'm not saying it's not significant and that you don't need to know about it - I'm just saying you probably won't run into it much in real life. If I'm wrong, let me know when you're done with your residency.
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| DrVirgo
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Yes,
It is funny that such a rare disease is given so much importance for the boards.
CGD is mentioned in Micro, Immuno, Biochem, Patho, and Genetics! Yet we will probably never see it in real life!
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| giovanni83
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So definetivily microorganism we must keep out if there's CGD are:
Catalase + :
-All species of genus Staphylococcus
-Pseudomonas
-Family Enterobacteriaceae (which includes Citrobacter, E.Coli, Enterobacter, Klebsiella, shigella, yersinia, proteus, salmonella, serratia)
is it right??
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