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Subject:
From:
Timothy Cser <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Date:
Thu, 18 Jun 2020 17:53:02 +0000
Content-Type:
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text/plain (324 lines)
Hey Don!  Yes, the standard mixed cellulose membrane will have a very  quick wetting time.  The reason we'd want to add some sterile diluent is so the organisms are countable.  With just a few mLs all the colonies will be concentrated in the middle of the membrane and make it difficult to count.

We sell a PVDF filter that's designed to avoid binding antibiotics and other compounds.  Yes, sometimes during method development you'll find a binding that you might not have been aware of and see some inhibition.  We work with many customers who might be having this issue and moving to a PVDF filter is one of the options.  We have a compatibility chart that's more based on chemistry but it's useful because it has many compounds that you'd be able to see upfront aren't compatible with that particular filter.

Yes, any sample over about 10mL is probably perfectly fine without a pre-wet.  All we're trying to do is spread out the contamination, if present, so it's countable.

The .22u vs .45u argument is still prevalent although 95% of firms do use the .45u filter for bioburden testing.  The biggest reason is that the pore size is nominal, meaning the largest pore would never exceed .45u but the average pore size is smaller.  These larger pores allow the nutrients from the media to get to the colonies faster.  "Not larger than .45u" is also written into the guidances, which I'm sure you know, so that's what people follow.  We performed a study of .45u vs .22u and both were able to retain B. diminuta up to about 1000 CFU before any passage occurred in the .45u filter but the recovery on the .45u filter was about 20% higher with larger colonies.  In addition. The .45u filters product faster that can also reduce the chances for binding product.

I can send this paper to anybody who'd like it.....feel free to contact me directly at [log in to unmask]

Sincerely,

Tim Cser
MilliporeSigma

-----Original Message-----
From: The Pharmaceutical Microbiology Forum Email List <[log in to unmask]> On Behalf Of Donald English
Sent: Tuesday, June 16, 2020 4:52 PM
To: [log in to unmask]
Subject: Re: [PMFLIST] Water Filtration Bioburden

Hi Tim,

It is my understanding that membrane filter composed of mixed cellulose fibers have a quick wetting time in which a pre-wetting might not have to be performed.  Is this correct?

What is your  opinion in about using hydrophilic membrane filters that are composed of PTTE or Nylon if there is a concern about binding of ingredients in an aqueous formulation to the filter?  From conducting preservative challenge testing, I do know that Methylcellulose is able to bond to certain types of preservatives.  If there was an issue, I think that this would come up in the performance of suitability testing of the formulation in which spiked microorganisms could not be recovered.

For conducting membrane filtration of purified water samples, I see no reason as to why a membrane filter composed of mixed cellulose fibers cannot be used on a routine basis without pre-wetting since a normal aliquot for testing is 100-mls.

The next question then comes up as whether it is best to use a 0.22 or 0.45 micron membrane filter for water testing.  I have seen many opinions expressed during the years in which one is the best for usage.

Regards,
Don

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


Sent from my iPhone

> On Jun 16, 2020, at 4:31 PM, Crystal Booth <[log in to unmask]> wrote:
>
> Hi Alison,
>
> I agree with Tim. Also, if you are testing a small amount, you can add it to a sterile diluent (such as sterile water or Fluid A, etc.) prior to filtering the entire amount.  You'd want to do a negative control of your diluent.
>
> Kind regards,
> Crystal Booth
>
> Crystal Booth, M.M.
> Regional Manager
> PDASE Chapter President
> PSC Biotech Corporation
> 700 Corporate Center Drive Pomona, CA 91768 Mobile (909) 620-0757
> https://clicktime.symantec.com/3AnnKY7SHRzG8EnWaVxUowD6H2?u=https%3A%2
> F%2Fwww.biotech.com%2F
>
>
>
> -----Original Message-----
> From: The Pharmaceutical Microbiology Forum Email List
> <[log in to unmask]> On Behalf Of Timothy Cser
> Sent: Tuesday, June 16, 2020 12:24 PM
> To: [log in to unmask]
> Subject: Re: [PMFLIST] Water Filtration Bioburden
>
> [CAUTION: This email originated from outside of the organization. Do
> not click links or open attachments unless you recognize the sender
> and know the content is safe.]
>
> Hi Alison.  How much water are you testing?  If it’s 100mL a pre-wet isn’t needed.  If it’s a small amount like 5mL, you can pre-wet with 10-20mL of sterile water/diluent.  Pre-wetting is designed to minimize any binding of the article you’re wishing to test but water isn’t a problem.
>
> Tim Cser
> MilliporeSigma
> MilliporeSigma is a division of Merck KGaA, Darmstadt, Germany
>
>> On Jun 16, 2020, at 9:18 AM, Berman, Alison <[log in to unmask]> wrote:
>>
>> Hi all,
>> For those of you performing bioburden testing of waters using the filtration method, are you using a pre-wet, a rinse, or both a pre-wet and a rinse?
>> If a study is performed showing equivalency with and without a pre-wet and/or rinse, it is acceptable to forego them?
>> Thanks
>>
>> Alison Berman, MFS
>> Supervisor
>> Quality Control - Microbiology
>>
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