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November 2013

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Subject:
From:
"Merideth, Curt" <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Date:
Wed, 13 Nov 2013 19:16:47 +0000
Content-Type:
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I think it's because 5 is less than the limit of detection.

(0+1)/2 = 0.5cfu/plate

At this point I round it to 1cfu/plate, apply the dilution factor and report as 10 cfu/g.

Even if you don't round it up, the limit of detection of <1cfu/plate would still apply here.

Although I know some disagree, I don't believe increasing the number of replicates decreases the limit of detection either.  So in your example 5cfu/10 plates = 0.5cfu/plate same as above, round it or apply the limit of detection.

Regards,

Curt
Curt Merideth | Manager - Microbiology
Long Pharmaceuticals, LLC | [log in to unmask]

-----Original Message-----
From: The Pharmaceutical Microbiology Forum Email List [mailto:[log in to unmask]] On Behalf Of Robert Ryan
Sent: Thursday, November 07, 2013 11:16 AM
To: [log in to unmask]
Subject: Re: [PMFLIST] Microbial Enumaration Results - When No Growth Pbserved

I'd like if I may to take this discussion a little further.

From my experience of duplicate plate counting: at a 1 in 10 dilution

Zero / zero = <10
Count / count = sum / 2

Zero / one = <10

What I would like to discuss is;

The wording in the pharmacopoeias is not entirely explanatory as to why:

Zero / one (does not) = five

I have since been bred to ignore such questions and just record <10 but I remember when I first started in this industry writing 5.

Is it perhaps that stating 5 is to definitive? Would <5 be a closer representation of the diluent and count.

What would the result be if I plated ten times and half recorded 1 and the other half zero?

As for convention on the <1 and zero debate I think we should all state zero and stop hiding behind pour hot tail graphs.

Rob Ryan.
Microbiology Team Leader

Thornton and Ross Ltd
tel: 01484 842217
email: [log in to unmask]

-----Original Message-----
From: The Pharmaceutical Microbiology Forum Email List [mailto:[log in to unmask]] On Behalf Of Malathi Elumalai
Sent: 21 October 2013 14:18
To: [log in to unmask]
Subject: Re: [PMFLIST] Microbial Enumaration Results - When No Growth Pbserved

Hi

If your dilution is 1:10 , then 1 colony is consider as 10, so there is no growth in both plates , you should write as <10 cfu(limit of detection)

On Thu, Oct 17, 2013 at 11:36 PM, Guna N <[log in to unmask]> wrote:

> Hi Peter,
>
>      when you are not getting any count on both the plates, then it 
> should be considered as <1 cfu/ plate. So the average will be <1 cfu/each plate.
> But We cant say nil or zero.
>
> Example
>   If it is 1:10 dilution, no growth on both plates.
>
> Plate(01)= <1.
> Plate(02)=<1.
>
> Average = < 1.
>
>
>                    <1cfu  100
> Formula=--------------------
>                        10gm
>
>  Result should be <10 CFU/plate.
>
> As you are considering  the dilution first, it ll be confusing.
>
>
> I think it may help to clear you.
>
> Regards,
>
> Guna.N
>
> Microbiologist,
> Microlabs pvt ltd.
>
> > Date: Wed, 16 Oct 2013 15:13:22 +0000
> > From: [log in to unmask]
> > Subject: [PMFLIST] Microbial Enumaration Results - When No Growth
> Pbserved
> > To: [log in to unmask]
>  >
> > Dear Forum
> >
> > I am looking for an answer to the following question, in order to 
> > help
> me determine what the most widely used method is:
> >
> > When performing the Harmonised Microbial Enumeration Test (HMET) and 
> > no
> growth is observed on any of the two plates containing 1/10 dilution 
> of the sample, would you class the result as:
> >
> > <5cfu - Based on multiplying by the dilution factor of 10 and then
> dividing by number of plates (two).
> >
> > <10cfu - Based on multiplying by the dilution factor and not taking 
> > the
> number of plates into consideration.
> >
> > All replies are greatly appreciated.
> >
> > Regards
> >
> > Peter
> > Peter Mathieson (BSc Hons)
> > Microbiology Project Manager
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Accugenix - http://www.accugenix.com

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

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

BD Diagnostic Systems - http://www.bd.com/ds/

Biolog - http://www.biolog.com

EMD Millipore -  http://www.emdmillipore.com/biomonitoring

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

Microtest Laboratories, Inc. - http://www.microtestlabs.com

Pall - http://www.pall.com

NovaTek International - http://www.ntint.com

Rapid Micro Biosystems - http://www.rapidmicrobio.com  (formerly GPS)

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

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

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Please take a second to visit our sponsors' web sites and say thank you for their support of this service.


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Accugenix - http://www.accugenix.com

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

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

BD Diagnostic Systems - http://www.bd.com/ds/

Biolog - http://www.biolog.com

EMD Millipore -  http://www.emdmillipore.com/biomonitoring

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

Microtest Laboratories, Inc. - http://www.microtestlabs.com

Pall - http://www.pall.com

NovaTek International - http://www.ntint.com

Rapid Micro Biosystems - http://www.rapidmicrobio.com  (formerly GPS)

Steris - http://www.sterislifesciences.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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The Microbiology Network (http://microbiologynetwork.com) and supported by
our sponsors 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.


Life Technologies - http://www.lifetechnologies.com/PharmaAnalytics

Accugenix - http://www.accugenix.com

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

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

BD Diagnostic Systems - http://www.bd.com/ds/

Biolog - http://www.biolog.com

EMD Millipore -  http://www.emdmillipore.com/biomonitoring

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

Microtest Laboratories, Inc. - http://www.microtestlabs.com

Pall - http://www.pall.com

NovaTek International - http://www.ntint.com

Rapid Micro Biosystems - http://www.rapidmicrobio.com  (formerly GPS)

Steris - http://www.sterislifesciences.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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