Gram

Martin Harvey martin at broken-cross.demon.co.uk
Fri Aug 8 10:22:15 EST 1997


In article <5setjl$k3l$1 at upsn21.u-psud.fr>, Yves Dessaux
<Yves.Dessaux at isv.cnrs-gif.fr> writes
>In article <9708032033.AA06833 at alpha.incqs.fiocruz.br>, 
>ivano at ALPHA.INCQS.FIOCRUZ.BR says...
>
>>Do you know any new methodology to differentiate gram positive from gram
>>negative bacteria.  Sometimes it is very difficult to se the difference 
>>on the microscope. I have  an older technique, but I would like to see 
>>more.
>
>Boehringer - if I am right - sells a kit consisting of plastic
>stripes covered by a reagent that you only need to deep into a bacterial 
>culture. It gives you the Gram type of the bacteria, though some
>false responses are sometimes seen (but a list of the organisms
>susceptible to yield a false response is provided with the kit).
>
>YD
I always DID have trouble with the Gram stain, but there again who
doesn't? :-)

As far as I'm concerned, the stain is a very subjective test which is
(in the case of cell ageing/ gram variables) open to interpretation.
Modern test kits give a more reproducible response, but (I suppose) are
pulling away from Gram's original idea of staining, washing and
counterstaining.

The ultimate 'gram-test' would be to measure membrane phospholipids
composition by GC-MS - giving a fingerprint for each species. But who's
got the money and time to do all that?

(sigh)
Martin Harvey



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