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Subject:
From:
Evangelia Georgiadou <[log in to unmask]>
Reply To:
The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Date:
Mon, 2 Sep 2019 10:54:42 +0300
Content-Type:
text/plain
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text/plain (166 lines)
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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