gram-negative

English translation: See explanation

19:41 Jan 20, 2003
English to English translations [PRO]
Medical
English term or phrase: gram-negative
"Spinal lesions are commonly caused by tuberculosis or gram-negative organisms. These are organisms that cannot be detected using standard dying techniques."
I don't quite see the point of the last sentence. Does it mean that GRAM is a non-standard dying technique? Maybe in 1995 (when the book was written) it was not a standard technique and now it is, or is it still not one of the standard dying techniques? Which are then the standard dying techniques?
Pablo Fdez. Moriano
Spain
Local time: 09:07
English translation:See explanation
Explanation:
GRAM NEGATIVE ORGANISMS - A common class of bacteria normally found in the gastrointestinal tract that can be responsible for disease in man (sepsis). Bacteria are considered to be "gram negative" because of characteristic staining properties under the microscope. The gram staining characteristics of bacteria have resulted in an important classification system for the identification of bacteria.


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Note added at 2003-01-20 19:59:59 (GMT)
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I understand the sentence to mean that standard, i.e. non-
Gram tests, cannot detect these organisms.

Gram-positive organisms have a cell wall composed almost entirely of peptidoglycan whereas Gram-negative organisms have a lipid rich outer wall. This fundamental difference allows the Gram stain to work.

http://www.arches.uga.edu/~kristenc/history.html
Selected response from:

Kim Metzger
Mexico
Local time: 02:07
Grading comment
Thank you, Kim, I also think standard means here non-Gram techniques. All other contributions were also very helpful, especially eldira's amazingly well documented reply.
4 KudoZ points were awarded for this answer



Summary of answers provided
4 +2See explanation
Kim Metzger
3 +3The Gram staining method does not work on certain bacteria
eldira
5 +1you are absolutely right, the sentence is absolutely wrong
Elisabeth Ghysels
5Spelling mistake
Lesley Clayton
5Gram staining technique is a standard technique . . .
Fuad Yahya


Discussion entries: 1





  

Answers


6 mins   confidence: Answerer confidence 4/5Answerer confidence 4/5 peer agreement (net): +2
See explanation


Explanation:
GRAM NEGATIVE ORGANISMS - A common class of bacteria normally found in the gastrointestinal tract that can be responsible for disease in man (sepsis). Bacteria are considered to be "gram negative" because of characteristic staining properties under the microscope. The gram staining characteristics of bacteria have resulted in an important classification system for the identification of bacteria.


--------------------------------------------------
Note added at 2003-01-20 19:59:59 (GMT)
--------------------------------------------------

I understand the sentence to mean that standard, i.e. non-
Gram tests, cannot detect these organisms.

Gram-positive organisms have a cell wall composed almost entirely of peptidoglycan whereas Gram-negative organisms have a lipid rich outer wall. This fundamental difference allows the Gram stain to work.

http://www.arches.uga.edu/~kristenc/history.html



    Reference: http://www.mymedadvice.com/default.asp?U=/html/4/gls_2262.ht...
Kim Metzger
Mexico
Local time: 02:07
Native speaker of: Native in EnglishEnglish
PRO pts in pair: 2249
Grading comment
Thank you, Kim, I also think standard means here non-Gram techniques. All other contributions were also very helpful, especially eldira's amazingly well documented reply.

Peer comments on this answer (and responses from the answerer)
agree  Arthur Borges: I used to wonderif they weren't bacteia that could only be weighed in ounces or existed only in zero gravity. Then I looked it up and was highly disappointed to find out that it's just like Kim says.
5 hrs

agree  zebung
6 hrs
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7 mins   confidence: Answerer confidence 5/5 peer agreement (net): +1
you are absolutely right, the sentence is absolutely wrong


Explanation:
The Gram stain is used for some decennia at least (I would have to check, but I'm certainly not far of the mark with: at least 50 years); indeed the gram negative organisms are not coloured by the gram staining technique, but they are easily visible nevertheless.
Greetings,

Nikolaus

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Note added at 2003-01-20 20:09:40 (GMT)
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well, as eldira found out, not 50 years but 150 years.


    Reference: http://medic.med.uth.tmc.edu/path/grampro.htm
Elisabeth Ghysels
Local time: 09:07
PRO pts in pair: 28

Peer comments on this answer (and responses from the answerer)
agree  Alexandra Tussing
2 hrs
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8 mins   confidence: Answerer confidence 3/5Answerer confidence 3/5 peer agreement (net): +3
The Gram staining method does not work on certain bacteria


Explanation:
The Gram staining method, named after the Danish bacteriologist who originally devised it in 1844, Hans Christian Gram, is one of the most important staining techniques in microbiology. It is almost always the first test performed for the identification of bacteria. The primary stain of the Gram's method is crystal violet. Crystal violet is sometimes substituted with methylene blue, which is equally effective. The microorganisms that retain the crystal violet-iodine complex appear purple brown under microscopic examination. These microorganisms that are stained by the Gram's method are commonly classified as Gram-positive or Gram non-negative. Others that are not stained by crystal violet are referred to as Gram negative, and appear red.

Gram staining is based on the ability of bacteria cell wall to retaining the crystal violet dye during solvent treatment. The cell walls for Gram-positive microorganisms have a higher peptidoglycan and lower lipid content than gram-negative bacteria. Bacteria cell walls are stained by the crystal violet. Iodine is subsequently added as a mordant to form the crystal violet-iodine complex so that the dye cannot be removed easily. This step is commonly referred to as fixing the dye. However, subsequent treatment with a decolorizer, which is a mixed solvent of ethanol and acetone, dissolves the lipid layer from the gram-negative cells. The removal of the lipid layer enhances the leaching of the primary stain from the cells into the surrounding solvent. In contrast, the solvent dehydrates the thicker Gram-positive cell walls, closing the pores as the cell wall shrinks during dehydration. As a result, the diffusion of the violet-iodine complex is blocked, and the bacteria remain stained. The length of the decolorization is critical in differentiating the gram-positive bacteria from the gram-negative bacteria. A prolonged exposure to the decolorizing agent will remove all the stain from both types of bacteria. Some Gram-positive bacteria may lose the stain easily and therefore appear as a mixture of Gram-positive and Gram-negative bacteria (Gram-variable).

Finally, a counterstain of basic fuchsin is applied to the smear to give decolorized gram-negative bacteria a pink color. Some laboratories use safranin as a counterstain instead. Basic fuchsin stains many Gram-negative bacteria more intensely than does safranin, making them easier to see. Some bacteria which are poorly stained by safranin, such as Haemophilus spp., Legionella spp., and some anaerobic bacteria, are readily stained by basic fuchsin, but not safranin. The polychromatic nature of the gram stain enables determination of the size and shape of both Gram-negative and Gram-positive bacteria. If desired, the slides can be permanently mounted and preserved for record keeping.

Besides Gram's stain, there are a wide range of other staining methods available. By using appropriate dyes, different parts of the bacteria structures such as capsules, flagella, granules, and spores can be stained. Staining techniques are widely used to visualize those components that are otherwise too difficult to see under a light microscope. In addition, special stains can be used to visualize other microorganisms not readily visualized by the Gram stain, such as mycobacteria, rickettsia, spirochetes, and others. In addition, there are modifications of the Gram stain that allow morphologic analysis of eukaryotic cells in clinical specimens.

http://www.uphs.upenn.edu/bugdrug/antibiotic_manual/Gram1.ht...


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Note added at 2003-01-20 20:14:45 (GMT)
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More information on the tuberculosis bacillus and staining methods:

...some bacteria are neither gram positive or negative - for example Mycobacterium tuberculosis, the causal agent of tuberculosis, is an acid-fast bacillus: spirochaetes including Treponema pallidum {the causal agent of syphilis} whose cell wall is so thin that it doesn\'t take up dye easily:

http://www.infection-control.org.uk/gram.html

Some bacteria stains: (from http://www.hoflink.com/~house/Microbio.html#anchor52009)

Bacteria Stains, Media
Acid Fast Stain —For Mycobacteria
http://www2.austin.cc.tx.us/microbugz/13acidfast.html

Flagella Stain
http://www2.austin.cc.tx.us/microbugz/16flagella.html

Gram Stain I — History and mechanisms
http://health.upenn.edu/bugdrug/antibiotic_manual/Gram1.htm

Gram Stain II — Discussion, history, development
http://www.encyclopedia.com/searchpool.asp?target=@DOCTITLE ...\'s%20stain

Gram Stain, Spore Stain, Streak Plates — Lab exercise. Much information
http://www.slic2.wsu.edu:82/hurlbert/micro101/pages/101lab6....

Gram Stain Procedure I — Basic info and procedure
http://medic.med.uth.tmc.edu/path/grampro.htm

Gram Stain Procedure II — Overview, information, procedure
http://www.meddean.luc.edu/lumen/DeptWebs/microbio/med/gram/...

Gram Stain Procedure III
http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/prostr...

H2S Test — SIM Media
http://www2.austin.cc.tx.us/microbugz/42sim.html



eldira
Indonesia
Local time: 14:07
Native speaker of: Native in IndonesianIndonesian
PRO pts in pair: 85

Peer comments on this answer (and responses from the answerer)
agree  Alexandra Tussing: quite impressive
2 hrs

agree  Scott Evans: Somebody did their homework (and quite well!)
6 hrs

agree  Tanja Abramovic
12 hrs
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20 mins   confidence: Answerer confidence 5/5
Gram staining technique is a standard technique . . .


Explanation:
. . . if there ever was one. It is certainly one of the most widely used techniques.

Incidentally, "staining" is much more commonly used than "dying" in the context of microbiological studies.

As I read it, the sentence implies (weakly) that the gram stain is a standard technique. The last sentence should have said, "These are organisms that cannot be detected using standard dying techniques, such as the gram staining technique."

As to which techniques are "standard," there may not be a definitive answer, as what was non-standard yesterday could very well be run of the mill today. For a good introduction to stains, here is a useful link:

http://www.arches.uga.edu/~kristenc/index.html


    Reference: http://www.arches.uga.edu/~kristenc/index.html
Fuad Yahya
Native speaker of: Native in ArabicArabic, Native in EnglishEnglish
PRO pts in pair: 893
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14 hrs   confidence: Answerer confidence 5/5
Spelling mistake


Explanation:
Please note that it is not 'dying' as written in the original (from 'to die' as in 'dead'), but 'dyeing' (from 'to dye' as in 'stain, colour').

Ref: any dictionary.

Lesley Clayton
France
Local time: 09:07
Native speaker of: Native in EnglishEnglish
PRO pts in pair: 32
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