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The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
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Mon, 8 May 2006 11:12:07 -0400
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Brendan:

Compliance to Ph. Eur. aside, is this level of efficacy sufficient to 
maintain effectively product integrity?






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05/07/2006 10:15 PM
Please respond to The Pharmaceutical Microbiology Forum Email List

 
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        Subject:        [SPAM]::[PMFLIST] Preservative testing


Can members of the forum offer their opinion on how to evaluate a
preservative efficacy result.

Given that the Ph.Eur states in the General Notices for Limits:

"In determining compliance with a numerical limit the calculated result of
a test or assay is first rounded to the number of significant figures
stated, unless otherwise prescribed.
The last figure is increased by one when the part rejected is equal or
exceeds one half unit, whereas it is not modified when the part rejected 
is
less than one half unit."

Consider the following example being a result for an oral product
challenged with A.niger where the requirement is for a log reduction in 
the
viable count of log 1 at 14 days with no increase thereafter:
(Note: the log reduction is stated as 1 not 1.0)

Example A
                  Challenge   14 Days           28 days
Count/ml          480,000           170,000           28,000
Log (2 sig figures)     5.68        5.23        4.45
Log reduction           -           0.45        1.23

Example B
                  Challenge   14 Days           28 Days
Count/ml          480,000           170,000           28,000
Log (rounded)           6           5           4
Log reduction           -           1           2

Example A fails as a log 1 reduction is not achieved at 14 days.
Example B passes as a log 1 reduction is achieved at 14 days.

In this actual result if we apply the limit as defined in the Ph. Eur a
pass is achieved. In trying to apply greater accuracy with the use of log
values to 2 decimal places a fail is achieved. Which result would you
accept?

Brendan Lincoln
Microbiologist
Pacific Pharmaceuticals Ltd


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------------------
The PMFList (http://microbiol.org/PMFList_info.htm) is operated from
The Microbiology Network (http://microbiol.org) and supported by
our sponsors (http://microbiol.org/sponsor.htm) as a service to
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

American Type Culture Collection - http://www.atcc.org

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

Biolog - http://www.biolog.com

Biomerieux - http://industry.biomerieux-usa.com

Dupont Qualicon - http://www.qualicon.com

EMD Chemicals - http://www.emdchemicals.com

EMSL Analytical, Inc. - http://www.emsl.com

Genomic Profiling Systems, Inc. - http://www.genprosys.com

MIDI, Inc. - http://www.midi-inc.com

Millipore - http://www.millipore.com

Pall - http://www.pall.com

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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