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May 2006

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Subject:
From:
Scott Sutton <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Date:
Wed, 31 May 2006 08:00:46 -0400
Content-Type:
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Dan,

I understand your point, but I maintain there is a real difference between
the Limit of Detection (1 CFU on a plate) and the Limit of Quantification
(25 CFU).

As to your question - I would report it out today as an average of 17 CFU/ug
or mL.  This is common accepted practice.  It is also wrong and should be
corrected.  If we don't start paying attention to the accuracy of our
methods who will?

Let me ask the question you posed differently - how would you report out
plate counts of 358 and 402?

Most of us would report them out as TNTC and hopefully we did a dilution
that fell into the range of CFU/plate that is accurate.  We are comfortable
with the idea of a countable range justification for eliminating inaccurate
counts at the high end, why should the accuracy be ignored at the low?

Scott

Scott Sutton, PhD
Pharma Consultant, Microbiology
Vectech Pharmaceutical Consultants, Inc
http://www.vectech.com
+1 585-594-8273  
This Message is privileged, confidential and protected by law from
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-----Original Message-----
From: The Pharmaceutical Microbiology Forum Email List
[mailto:[log in to unmask]] On Behalf Of Daniel Prince
Sent: Tuesday, May 30, 2006 5:58 PM
To: [log in to unmask]
Subject: Re: [PMFLIST] Bioburden

Scott and others,
I slightly disagree if the meaning here is to report all counts as less than
an accepted minimum countable range [e.g., 25]  times 1 times the dilution
factor even when counts are detected.

This is because there is a dramatic difference in accurate disclosure if
detectable counts are ignored and the result is reported simply as < some
number, N [in this thread <250.]

<250 can mean all counts from 0-249cfus with any one of the possible 250
count outcomes as probable as another. Clearly, if you have two plates each
with 23 or 24 organisms you get a much different feel about the data if you
report about 230 cfu/gram versus <250 with no mention of what you so growing
on the plates.

How would you report the following hypothetical result? Assume there are no
lab errors or inhibitory issues at play. Would you conclude <250 or  <2,500
cfu or average all of the detectable counts to obtain an estimate of 147
cfu/mL?
Dilution                  #cfu, duplicate counts
1:10			24, 10
1:100		           1, 0

Furthermore, when all plates from a dilution range are 0 the proper
convention is to report the count as <10 not <250. This is as per FDA BAM. 

In closing, the most valuable and powerful attribute that the classical
methods have is that they speak to real, living, viable, replicating
organisms. This must not be diminished or marginalized. Conversely, rapid
methods with greater "accuracy" do not measure living, viable, replicating
organisms. Is it possible that what they do measure is in fact not readily
interpretable in connection to our classical viability techniques? If so,
there will be some who accept this fact and consider the results obtained by
the new technique as valid while others will not, citing instead a
preference for a culture technique.


Sincerely,
Daniel L. Prince, Ph.D.
President
Gibraltar Laboratories, Inc.
122 Fairfield Road
Fairfield, NJ 07004
973-227-6882 ext. 519
973-227 0812 FAX
www.gibraltarlabsinc.com



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------------------
The PMFList (http://microbiol.org/PMFList_info.htm) is operated from
The Microbiology Network (http://microbiol.org) and supported by
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the scientific community.

Please take a second to visit our sponsors' web sites and say thank you for their support of this service.

Accugenix - http://www.accugenix.com

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ATS Laboratories - http://www.ats-labs.com

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NovaTek International - http://www.ntint.com

Raven Biological Labs - http://www.ravenlabs.com

Veltek Associates, Inc - http://www.sterile.com

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The nature of this service is to provide a medium for communication.  The specific statements and endorsements of individuals participating in the discussions are not necessarily those of The Microbiology Network, Inc., the PMF, or the sponsors of the list.

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