There are different cleanliness classes in pharmaceuticals. Class 100 or 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 particle counts. Some people have confusions about the limits of ISO 5 class and ask me for its clarifications.
Suppose if you had exposed 5 plates and each had 1 CFU then the average will be 1 and according to the specification area fails in the viable count.
The average of all exposed plates should be less than 1. For example, if you had exposed 5 plates and all plates have the following number of colony forming units.
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.
Even you can have 4 CFUs in a single plate as below.
The average of these counts is 4/5 = 0.8 CFU/plates and it also complies the specification.
None of the regulatory guidelines says that how much count could be there in a single plate. It means you should have 1 CFU less than the number of Petri plate exposed in class ISO 5 area to get average CFU less than 1 to comply with the specification. Therefore, the average of all exposed plates should be less than 1 CFU /plate but not in any individual plate.
In most of the cases when we expose the Petri plate or active air sampling, we don't everage the count of the plates sampled in the area. In such conditions, we should consider <1 CFU/plate as 0 CFU/plate because we can get <1 CFU only by averaging the results as described in the above examples.
However, it is not good to have a single CFU in ISO 5 area because the sterile filling is done here and it will contaminate the sterile product being manufactured in the area. Therefore, we should focus to get 0 CFU in such critical areas.
The average of all exposed plates should be less than 1. For example, if you had exposed 5 plates and all 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
|
Even you can 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/plates and it also complies the specification.
None of the regulatory guidelines says that how much count could be there in a single plate. It means you should have 1 CFU less than the number of Petri plate exposed in class ISO 5 area to get average CFU less than 1 to comply with the specification. Therefore, the average of all exposed plates should be less than 1 CFU /plate but not in any individual plate.
In most of the cases when we expose the Petri plate or active air sampling, we don't everage the count of the plates sampled in the area. In such conditions, we should consider <1 CFU/plate as 0 CFU/plate because we can get <1 CFU only by averaging the results as described in the above examples.
However, it is not good to have a single CFU in ISO 5 area because the sterile filling is done here and it will contaminate the sterile product being manufactured in the area. Therefore, we should focus to get 0 CFU in such critical areas.
Hi,
ReplyDeleteThanks for posting about this important topic. I personally disagree with the statements which implies averaging of data related to microbial contamination of the EM plates. This is simply for many reasons however most importantly because such bad practice of averaging may cover up some contamination during critical processing. for me, the meaning of "less than 1" in the regulatory guidance is the fact that we can not simply say "zero" as we may have some contamination which we are not aware of or not detected. I invite you to kindly study the topic further and amend the article accordingly. Thanks and kind regards, Mohamed
Hi Mohamed,
DeleteYou have rights to have an opinion different from the article but I don't think regulatory guidelines have any hesitation in writing 0 cfu/plate.
Furthermore, we are not monitoring environment directly but we check it in the terms of cfu/plate and we can write 0, if we don't find anything.
If my interpretation for <1 cfu/plate is wrong then regulatory authorities must change it to 0 cfu/plate and every plate because anyone can interpret it wrongly like me.
Sir,we used to expose 1 plate at one location defined in sop. Then how this will work
ReplyDeleteIn that condition, it will be zero.
DeleteHi Ankur
ReplyDeleteThanks for the article. I have a doubt here, We have to report the final results at decimal points as specified in specification. To me 0.6, 0.8 are equal to 1 (based on rounding the figures). I agree if the specification says less than 1.0.
We can't determine colony forming units in decimal, therefore we write <1.
DeleteI really appreciate your comments and discussions, as it helps to gain more technical knowledge.
ReplyDeleteHi sir
ReplyDeleteI have one doubt, if we expose only one plate in BSC per day and we'll get one colony in plate then what is the result we have to write.
Hi Ankur,
ReplyDeleteI want to clarify one doubt.
Suppose we expose two settle plates in sterile filling enclosure at the time of product filling and found one cfu in one plate and in other plate 0 cfu, in this case can we report the result as <1 cfu/plate by averaging the results of two plates?
The number of active air samples is determined entirely after the evaluations of the companies. And I think these evaluations are very valuable in order to protect the product.
ReplyDeleteIf you look at the ISO 14644-1 active air limits, the limits are determined in cubic meters. There is no information about the possibility of taking an average. I do not agree that the result of the average is valid when the result of the average is <1 cfu/petri, as it has no basis and will prevent us from determining the regional contamination.
Yes as the average is less than one
ReplyDeleteWe exposed 2 plates .plate 1. 4cfu
ReplyDeletePlate 2. 3cfu count.
Sample 1ml. And dilution 1/10.
What's the cfu/ml????