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Quick confirmation on microbiol standards for water
We have always used 1 or less than 1 CFU/cm2 as the standard for our RO water. We buy in some RO water to supplement our own small RO unit.
This standard has been questioned by the company supplying the RO water.
Would be interested in opinions here of our standard for cosmetics manufacturing.
Thanks.
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9 Replies
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Questioned how?. That you can use 100?. Of course, they wouldn’t have to change the filters and the UV lamps so often.
Keep your standards as high as you can, that’s my opinion.
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Hi @DAS yes I agree we should maintain our standards. We had an interesting exhange with the RO water supplier as follows:Our email to them was as follows:“Our Quality Manager has alerted me to the microbiol test for the RO water delivery we received on Tuesday 15 September. From the attached photo you will see that the result is between 1 CFU/cm2 and 5 CFU/cm2. Usually, we would expect 1 or less than 1 CFU/cm2 . We have our own RO system, and the result is always ND (no bacteria detected). Our previous suppliers result was always 1 or less than 1 CFU/cm2 .”Their reply (from chemist):“From the information provided, what I understand is:1 CFU/cm2 = 1000 CFU/ml (per 1 ml sample)
5 CFU/cm2 = 10,000 CFU/ml (per 1 ml sample)
So in this case, your QC is <1 MPN/100 ml (per 100 ml sample).
Your QC show <1 MPN/100 ml sample which is interpreted as no detection.
The only difference is the unit (MPN) because of different testing method, but still your result per 100 ml sample is no detection. If in 100 ml sample has no detection, same goes to 1 ml of sample, no detection. So there should be no problem with your QC result.”
I have since found out that their own QC takes samples from the plant tap, not from a filled 18L bottle that is supplied to us. In my opinion this testing eliminates the possibility that the 18L bottles may be contaminated.
If, with our own testing from other suppliers we have also had results of 1 or less than 1 CFU/cm2, then I would expect the same from this supplier. I have missed anything? I’m not a water quality expert.
Thanks.
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It seems to me that none of you have an understanding that is correct.
From the attached photo you will see that the result is between 1 CFU/cm2 and 5 CFU/cm2.
- The measurement of volume is in CUBIC centimetres not SQUARE centimetres so this statement is without meaning.
From their reply:
1 CFU/cm2 = 1000 CFU/ml (per 1 ml sample)
Which repeats your mistake and adds a far worse one: 1 cubic cm is THE SAME as 1 mL.
So, frankly, the entire exchange is meaningless. -
With respect @Belassi are you telling me that the manufacturer of the microbiol test has got the test units wrong? Attached here is a photo of the units used by the test manufacturer, and they use cm2.
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Yes. And so have you…
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@mikethairwhihc kit are you using in the photo please?
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cm^2 is for the area, that makes sense to me since it’s a plate. I’m not a microbio person; I don’t know how schulke converts from CFU per area to CFU per volume, I also don’t understand how the QC from your supplier converts to MPN since that looks to be based on dilutions and the FDA method says you need at least 3 dilutions.
If I were in your shoes, I would try to use another supplier and contact a schulke technical rep to try and get some data from them.
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Hi @sven we are using https://www.schuelke.com/intl-en/products/mikrocount-duo.phpHighly recommended.
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Thanks @EVchem …… in the process of contacting schulke technical.
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