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[Microbiology] Re: Question on a MacFarland Standards

John Gentile via microbio%40net.bio.net (by yjgent from nospamcox.net)
Fri Oct 10 20:38:26 EST 2008

On 2008-10-10 17:08:25 -0400, "Rivera Morales, Luis [JR]" 
<luis.rivera from medtronic.com> said:

> Hi, Mr. Friedel
> I saw you e-mail on the internet when I was searching for how to create
> microorganism supension with a know population?  I know that some people
> use MacFarland Standard, but We don't have MacFarland Standard, we have
> Densichek colorimeter by biomeriuex.  Please, would you tell me how can
> I prepare those kinds of microbial suspension given a know concentration
> (for example, 10e6, 10e7 or 10e8).
> Thank you very much,
> Luis Rivera Morales
> Associate Microbiologist/Sterilization
> MPROC-Juncos
> Phone: 787-561-2840
> Fax: 787-561-2413

	The bioMeriuex colorimeter usually comes with 4 tubes with McFarland 
Standards 0.5, 1, 2, 3 and 4. These are made with latex particles and 
are very stable.The colorimeter should have colored sections on it 
relating to the 4 standards.

	You can also make your own standards using a formula with Barium 
Chloride and H2S04. A Google search found several sites that had the 
recipie, and Wikepedia even has a chart of each standard up to 4 with 
approximate bacterial concentratioin and nephelometer transmittance and 
absorbance for each one. I tried to copy it into this message but it 
did not format correctly.

John Gentile
Newsletter editor
Rhode Island Apple Group
John Gentile MS, M(ASCP)
Laboratory Information Mgr.
VA Medical Center
Providence, RI 
yjgent from cox.net

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