PET and test-microorganisms preparations

Hi guys,

In my firm, we send PET tests to a microbiologists. We do microbial quality testing in-house on batch ourselves. However, I want to become more aware of the process that goes into microbiology and testing of cosmetic products. I decided to look into some standards like the ISO 11930, this gave me a lot of useful information. UPS <61> did not really explain things like ISO standards does. 

My question to you guys is: 
When using microbial strains to make the preparation of test-microorganisms to inoculate, do you make it by growing your own strains and diluting it to a certain cfu/ml? Or is it possible to get your hands on finished standardised strains with a larger cfu/ml? It seems to me that the preparation of test-microorganisms takes up so much time. Is there a simpler way?


  • MarkBroussardMarkBroussard Member, Professional Chemist
    Short Answer:  No

    Unless you are going to offer this as a commercial service to third-party clients, it really is not going to make any sense to set up your own in-house PET testing lab for just your client base.  It would cost you probably 5X to do it in-house as opposed to sending it to a testing lab set up to perform these tests.

    If you are intent on doing this, see if you can procure lyophilized, standardized cultures of your test microbes so you don't have to spend inordinate time maintaining your culture bases.
    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    See website for details
  • I don't agree with you Mark. For example testing batches in-house is very cheap. We use Compact Dry plates that easily speeds the test times and reduce preparation times. They cost $4 each and covers testing on Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, Escherichia coli and Totale Aerobic Count. These plates can also be used for PET testing, and the only thing missing to get PET-testing done in-house for me is the cultures of test-microorganisms. 

    I have seen many different prices on PET-testing, generally around $1155, but I have also paid $90. 

    I think doing these tests in-house also improves the safety of the facility and products, as you can test more frequently. 
  • MarkBroussardMarkBroussard Member, Professional Chemist
    edited January 2018
    Like I said ... check into the man-hours required to maintain a set of cultures relative the frequency with which you perform PCT tests and then determine whether it is worth it or not for your operation.

    Yes, QC plate count testing on batches is cheap ... that's a whole lot different than PCT testing.  That's why I recommended checking into lyophilized cultures that you can just reconstitute when you need if you do PCT on low volume.

    I would be interested in learning about what you are currently using and what you find out regarding maintaining cultures.
    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    See website for details
  • MicroformulationMicroformulation Member, Professional Chemist
    Under a comprehensive cGMP/SOP program, you would want to send them out. Firstly, it gives you third party validation. Secondly, unless you are a Microbiologist, the interpretation of these tests could be sub-par. Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications. BS.Pharm Albany College of Pharmacy, Union University.
  • edited January 2018
    I have talked to Microbiologics, and found out that Epower™ can be a good solution for my needs. Available in concentrations ranging from 10E2 and 10E8 CFU per pellet and is offered at $38 per pellet. 

    My goal for this is to not need cultures that needs maintenance to reduce costs required to personnel.

    I think doing our own  PET testing as part of our already in-house stability testing reduces research time for new products, and speeds product launches, as well as improve safety of the products. For example I can retrieve parts of the Schülke koko test, in addition to the implementing of ISO 11930. This way I can test the efficacy of the preservative effect, but also the efficacy in the long term through detailed stability testing. 

    I will let you guys know my experience and the over all costs once I get started. 
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