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May 2006

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From:
Victor Mencarelli <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Date:
Tue, 30 May 2006 15:08:54 -0400
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Jill,

I have always been a proponent of NOT doing anything more than you have to 
when dealing with testing issues.  The more you do, the more likely you 
are to have an unexpected lab result that now places your product 
potentially in jeopardy for scrapping.

That said, if you can prove that your product is adequately neutralized to 
recover the organisms in you method verification (note I did NOT say 
validation as the more I think of it the more impossible it will be for 
micro to ever "validate" something!) then your procedure WITHOUT the pH 
adjustment is acceptable.  That said, you may still be questioned by a 
regulator as to why you aren't ensuring that your procedure produces test 
systems with pH within the range of 6-8.  While this is a nice 
"theoretical" growth range, I (and I am sure others on the listserve as 
well) have seen organisms capable of growing in pH of 4 as well as in pH 
of 9.  Therefore, is it REALLY necessary to have pH adjusted to "neutral" 
or is that just going to get us into further trouble?  From where I stand, 
all I see is added issues arising if we begin to try to bring our pH 
artificially to neutral.  More importantly, if we change the pH of the 
test solution, are we REALLY testing the PRODUCT or are we testing 
something else (e.g., the pH adjuster, the technique, etc.....)?

IF you choose to move down the path toward accepting the pH adjustment as 
"necessary", then I think you really need to think long and hard about HOW 
you are going to show that your procedure consistantly gives a pH of 6-8 
without having to CHECK the pH every time you perform the test. Otherwise, 
a whole NEW set of variables will be brought into play which we are going 
to need to discuss: sterilization of the pH system, use of sterilized 
water to rinse probes, etc.

Ultimately, if you can show that your material tests are verifiable 
without the adjustment, AVOID THE ADJUSTMENT.  IF you can't get your 
product methods verified without adjusting the pH then you can either 
choose to find or modify a method to allow for a more neutral ("bug 
happy") pH or make the leap of faith into adjustments.  However, I would 
caution you to be CERTAIN you are ready to deal with the other issues 
before making the jump to making test solution pH adjustments.

Vic Mencarelli
Regulatory Affairs Specialist
Engelhard Corp.
50 Health Sciences Dr.
Stony Brook, NY 11790
P: 631-380-2482
F: 631-689-6880
E-mail: [log in to unmask]

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Jill Blythe <[log in to unmask]> 
Sent by: The Pharmaceutical Microbiology Forum Email List 
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05/30/2006 11:27 AM
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Subject
[PMFLIST] pH Adjustments






In light of the harmonized microbial methods that I believe were signed 
off on in November, 2005, what are the thoughts out there on pH 
adjustments of the sample dilution to between 6-8?  Is it necessary to 
make the pH adjustment if we can show by dilution or neutralization, 
recovery of all the challenge microorganisms?

Also, if during validation, a pH adjustment is necessary, how close to 
the pH obtained during validation would one have to be for routine 
testing? Plus or minus 0.2 pH units or just between 6-8?

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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

=================================
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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