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Subject:
From:
"Chhibber, Jitendra" <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Date:
Wed, 4 Sep 2019 20:19:04 +0000
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Hi Evangelia,
One CFU does not necessarily mean that 1 bacterium grew into the 1 colony. Conversely, 1 spreader can grow all over the plate and inhibit or mask other bacteria. Due to the variabilities in the sampling methods, USP <1116> places more emphasis on calculation of Contamination Recovery Rate (CRR) irrespective of the number of CFUs. For ISO 5, the CRR is <1 % (not to be confused with <1 CFU).

For areas classified as ISO 5, no microbial contamination is allowed, i.e. the count should be 0 CFU/plate at all the locations. Each location is sampled and the results trended on an individual basis. You cannot calculate average microbial count from the results obtained from multiple locations. One CFU/plate from any location will trigger an investigation, cleaning and sanitization, appropriate corrective action/s and resampling to verify that the location is back in control.

Jitendra Chhibber
Zimmer Biomet, 
Palm Beach Gardens, FL,
USA

-----Original Message-----
From: The Pharmaceutical Microbiology Forum Email List <[log in to unmask]> On Behalf Of Evangelia Georgiadou
Sent: Monday, September 02, 2019 3:55 AM
To: [log in to unmask]
Subject: [EXTERNAL] [PMFLIST] Cfu counts in class A

[WARNING] This email did not originate inside Zimmer Biomet. Use caution before clicking on links or attachments.


Hello forum members,

I came across the following statement and i would like your comments on it.

*From Pharmaceutical Guidelines…*



Less than 1CFU/Plate in ISO 5 Class- How is it possible?

There are different classes in pharmaceuticals.Class ISO 5 is the highest cleanliness class, found on pharmaceutical industries and used in LAF and sterile filling area.This area is monitored for viable and non-viable counts.Some people have confusions about the limits of ISO 5 class and ask me for its clarifications.

All cleanliness classes have different standards for viable and non-viable particles but ISO 5 has <1 CFU per plate count for the viable count that makes the people confused because physically,the existence of less than 1 CFU is not passable.We cannot count colony forming units less than 1 (in
decimals) then why all the regulatory guidelines have this specification for the ISO 5 class.

Suppose if you had exposed 5 plates and each had 1 CFU then the average will be 1 and according to the spacification,the area fails in the viable count.

The average of all exposed plates should be less than 1.For example,if you have exposed 5 plates and all the plates have the following number of colony forming units:

Plate

1

2

3

4

5

Count

1

0

1

1

0



Average of these counts is 3/5=0.6 CFU/plate and it is within the specification.

You can have more than 1 CFU in one or two plates.See the following results:

Plate

1

2

3

4

5

Count

2

0

2

0

0



The average of these counts is 4/5=0.8 CFU/plate and it is also complies the specification.

Even if you have 4 CFUs in a single plate as below:

Plate

1

2

3

4

5

Count

0

0

4

0

0



The average of these counts is 4/5=0.8 CFU/plate and it is also complies the specification.

None of the regulatory guidelines says how much count be there in a single plate.It means,that you should have 1 CFU less than the number of petri plate exposed in a class ISO 5 area to get average CFU les than 1 to comply the specification.Therefore, the average of all exposed plates should be less than 1CFU/plate but not in any individual plate.

It should be clearly defined in SOPs,how many plates will be exposed in the area during viable count monitoring,because the number of plates plays a significant role in the determination of average.



Thank u

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The PMFList (http://microbiologynetwork.com/pmflist.asp) is operated from
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.
If your company would be interested in sponsoring this community, please contact [log in to unmask]



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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