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Subject:
From:
Donald English <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Date:
Thu, 28 May 2020 20:39:14 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (129 lines)
Dear Kyriaki,

In most pharmaceutical manufacturing plants, microbial testing of
purified water is conducted by using membrane filtration in which a 100-ml
aliquot is used.  There is no need to worry about standard deviation
between plates since a single membrane filter is used.

In 9215B. Pour Plate Method of Standard Methods for the Examination of
Water and Wastewater, I do not see anything about plating duplicate 1.0 ml
and 0.1 ml aliquots of a water sample from an undiluted sample and a 1.0-ml
aliquot from a 1:100 dilution.

If you want to perform duplicate plate counts, I have no objections.
However, see Table 9020 VI of Section 9020 for the acceptable range of an
allowable logarithm difference for duplicate counts.

If you have a properly designed purified water system, the microbial counts
in a distribution loop are normally low such as between <1 and 10 CFU/ml.
I would think hat it would be somewhat difficult to establish an allowable
standard of deviation for 2 plates at a sampling site with such low counts.

Don

Donald J. English Microbiological Quality Consulting LLC
Florham Park, New Jersey 07932


On Thu, May 28, 2020 at 7:18 PM Kyriaki Antoniou <[log in to unmask]>
<[log in to unmask]> wrote:

> Dear all,
>
> Could you give me your knowledge/opinion on the below matter?
>
> Microbiological water analysis, in pharmaceutical company, is performed in
> duplicate for each sample. What is the best (allowable) Standard
> deviation/RSD between the two results from the duplicate testing? Is there
> any guideline to follow? If not, can you set your own RSD as per USP <1225>?
>
>
>
> Best Regards
>
> Kyriaki Antoniou
>
> Microbiology Department Manager
>
>
> Remedica Ltd
>
> Tel.: +357 25-553000 | Direct Tel.: +357 25-553508 (Internal: 508) | Fax:
> +357 25-390192
> Site address: Remedica Ltd, Aharnon Street, Limassol Industrial Estate,
> 3056 Limassol, Cyprus-EU
> Mailing address:  Remedica Ltd, P.O. Box 51706, CY-3508, Limassol Cyprus-EU
> Web: www.remedica.eu<http://www.remedica.eu/>
>
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Steris - http://www.sterislifesciences.com/

Charles River Laboratories - https://www2.criver.com/l/60962/2020-03-27/h6jqv6

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

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

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

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 PMF or the sponsors of the list.

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