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October 2019

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Subject:
From:
Richard Albert <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Date:
Wed, 2 Oct 2019 07:27:02 -0500
Content-Type:
text/plain
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text/plain (144 lines)
I will take this opportunity to share the following.  The question I have
always had about USP <51> is how 'real' world it is.  Real world
microbiology is not a microbe growing in a Petri dish.  I have seen
formulations containing preservatives be very effective when evaluated
according to USP <51>.  However the preservatives were not effective when
the microbial growth was as a biofilm.  Has anyone else observed something
similar or evaluated preservative effectiveness against microbial growth as
a biofilm.

Richard A. Albert
Senior Microbiologist
Kleen Test Products



On Tue, Oct 1, 2019 at 5:04 PM Robert Pritchett <
[log in to unmask]> wrote:

> Hello all,
>
> USP <51> AET has the following text regarding preparation of test strains:
>
> "Use standardized suspensions of test strains or prepare as stated below."
> "The viable microorganisms used in the procedure should be part of a
> freshly growing culture (e.g., in logarithmic growth phase) with the
> exception of A. brasiliensis spores."
>
> I've encountered at least one contract lab who uses pre-made commercially
> available lyophilized cultures specifically marketed for AET. The
> lyophilized cultures are hydrated and then used for testing and that lab
> tells me they consider this the mentioned "standardized suspensions" from
> the USP text. The contract laboratory does perform proper method
> suitability using the premade AET cultures with passing results and I have
> seen the validation work for using AET pre-made cultures, but I still
> question the acceptability of the practice.
>
> My personal opinions/talking points are as follows:
> - Why? It's simpler and more cost effective to start a fresh culture and
> any analyst with the title microbiologist should be able to adjust
> suspensions accordingly
> - Introducing recently desiccated, starved, frozen, and stressed cells as
> a challenge to a preservative system seems like a very bad idea - a weak
> preservative system might pass when it would otherwise fail when challenged
> with fresh cultures
> - The validation work cannot possibly represent the varied materials and
> preservative systems that may be tested for AET
>
> At this time, I've requested laboratories performing AET for my site to
> always use fresh cultures.
>
> With that said, I'm open to hear what others may say on the topic. Can
> anybody defend using pre-made commercial cultures for AET?
>
> -RP
>
>
>
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Science Advisory Board https://www.scienceboard.net/

Steris - http://www.sterislifesciences.com/

Charles River Laboratories - http://www.criver.com/

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

Microbiologics, Inc. - http://www.microbiologics.com

BD Industrial Media - http://www.bd.com/ds/

Boston Analytical http://www.bostonanalytical.com/

Associates of Cape Cod, Inc. - http://www.acciusa.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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