bakpity
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Hi!
Can you tell me which organisms can be stained by acid fast besides mycobacterium?
Moreover I read that mycobacterium is the only one that can conventionally be termed acid fast. How should I interpret this?
Txs
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| bactitech
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Acid fast organisms include the Mycobacteria, of which M. tuberculosis is one.
Acid fast staining is used for identification purposes of some other organisms, but these are not reported as "acid fast" organisms. This is done in the lab after they have grown out on media. Nocardia sp. is one that is considered "partially acid fast" when it's stained with a certain type of acid fast stain (a different decolorizer, I believe).
When a doctor orders a culture for "acid fast" bacteria, it is assumed that he/she is looking for Mycobacteria. The lab processes the specimen and stains it with an acid fast stain. We use auramine/rhodamine fluorescent stain on direct specimen smears as it is much more sensitive than the traditional Ziehl-Nielsen or carbol fuchsin stain that shows "red snappers." We still use the ZN stain AFTER we have growth.
The solid medium used to isolate acid fast organisms will also grow Nocardia and sometimes this organism is found in the acid fast culture as a fluke. By and large, however, Mycobacteria sp. are what are referred to as "acid fast."
Clear as mud, right :-(?
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| bactitech
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http://www.austin.cc.tx.us/microbugz/html/acid-fa...
http://www.sahealthinfo.org/tb/microacid.htm
Kinyoun and Ziehl-Nielsen differ in that ZN uses heat and Kinyoun is a "cold" method.
Article on Nocardia:
http://www.moffitt.usf.edu/pubs/ccj/v5n1/departme...
Differentiating gram positive rods using acid fast staining:
http://www.med.sc.edu:85/mycology/mycology-2.htm
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| mdwannabe
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I think microsporidium is weakly Acid-Fast as well. It is good to know, since it can cause diarheal outbreaks and can cause chronic diarhea in AIDS.
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| bactitech
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Cryptosporidium stains with carbol fuchsin, but antigen testing is much more sensitive than staining.
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| mdwannabe
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Are u saing it is not AF?
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| bactitech
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Cryptosporidium stains with acid fast stain, but when one refers to "acid fast organisms" one is referring to the Mycobacteria. Acid fast staining is used when microbiologists identify Mycobacteria, and also other organisms (differentiation of Nocardia/Streptomyces/Actinomyces).
If you want to test a stool specimen for Cryptosporidium, the most sensitive methodology is antigen testing, NOT staining. Our kit is a combination Giardia/Cryptosporidium antigen kit. We only report out what the doc orders, however, but all specimens are tested for both if either is ordered. This is the test kit we use (as does many other labs)
http://www.bd.com/clinical/products/direct/cpacgc...
(Check out sensitivity/specificity information)
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| mdwannabe
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got you ... thanks... I do remember that crypto was AF weakly... But I see your point for generality..
Thanks again.
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