USP Testing | Frequently Asked Questions
When testing dietary supplements, probiotics, botanicals, or drug products, selecting the appropriate microbiological method is essential to ensure compliance with FDA regulations and to maintain product integrity. The United States Pharmacopeia (USP) offers scientifically valid methods specifically designed to address the unique challenges posed by these complex product types.
This FAQ provides guidance on when and why USP methods should be used, the importance of suitability and preparatory testing, and how Eurofins helps streamline compliance by tracking product testing history. Whether you are submitting a product for the first time or updating your quality control procedures, this resource is designed to clarify key requirements and help you avoid common pitfalls.
When would I use USP methods for testing?
FDA 21 CFR Part 111 requires that test methods are scientifically valid, and demonstration of their validity shall be recorded. USP testing is a valuable option that meets these criteria for many reasons. When a product is not a food item and falls into the category of a dietary supplement, probiotic, botanical, or drug product, USP offers specific methods to allow for the complex nature of these product types. The complex active ingredients can often result in method interferences, false positives and negatives, and other issues. USP specific methods are appropriate for these types of complex matrices. Methods can be validated to show that the method is appropriate for the product being tested and would recover the organism of interest if it were present.
When should a suitability or preparatory test be performed?
For USP Microbiological test methods, suitability and preparatory analyses are performed to ensure not only the validity of the method for your product but also to decrease the chance of false negatives. Due to the complex nature of ingredients and compounds found in dietary supplement and probiotic products and ingredients, there are often matrix interference issues with common enumeration and pathogen detection methods. Performing USP suitability or preparatory testing is a way to ensure the validity of the method for your products.
The industry standard is to perform the suitability test on any product being tested for the first time. Periodic testing should also be performed as a quality control check when there are changes in the manufacturing of a product, including changes in suppliers or alterations to product formulations.
Why does Eurofins recommend suitability or preparatory testing?
If you are looking to be “USP Compliant”, suitability and/or preparatory testing is required by the FDA. Skipping this step can be risky, as during an FDA audit you will want to make sure you have documentation supporting that the method is scientifically valid and appropriate for your product.
What is the difference between the suitability of test method and the preparatory method?
The difference lies in the type of product to be tested. The suitability of test method is specifically associated with USP chapters 61 and 62, testing of non-sterile products, while the preparatory test is aligned with USP chapters 2021 and 2022 for testing of dietary supplements. The tests are very similar and generate information that identifies the possible presence of microbial growth inhibitors.
Does Eurofins track which samples have undergone suitability or preparatory testing?
Yes! We keep track of your product name each time a new sample is submitted. To make sure we do not repeat suitability on your sample, we suggest submitting the sample with the same product or reference a previous sample number to ensure our Registration Team can pull up your information. It is also best practice to keep track on your side which products or formulas have previously undergone suitability or preparatory testing. Working together will help eliminate the redundancy of unnecessarily performing once more on the same formula.
What information does Eurofins need when submitting a sample?
Due to the requirement to conduct suitability testing on the initial submission of each unique product formulation, Eurofins needs information regarding the products submitted for USP testing. This allows Eurofins to refer to the suitability testing that has already been completed for subsequent submissions of the same product and avoids adding unnecessary testing. This can be accomplished by one (or all) of the following routes:
► Include the full product name on each submission.
► Include the product SKU on each sample submission.
► Provide a reference sample number from a previous submission of the same product.
What does suitability test “Failure” mean?
In certain cases, the product under test inhibits the growth of an organism or organisms tested for using the USP methods. When this occurs, Eurofins automatically retests using additional steps to neutralize the inhibitory effects of the product on the test organism. However, if the spike organism is still not recovered following the series of additional steps taken to neutralize the inhibitory effects of the product, Eurofins Microbiology will report a suitability failure along with a neutralization statement.
► Suitability test “failure” does not mean that the test for the organism/organisms of interest has failed. In fact, it indicates that the organism is not likely to be present in the product due to the product being naturally inhibitory towards that organism.
► The USP chapter <2021> offers specific language to address this situation, which is as follows:
“If, in spite of the incorporation of suitable inactivating agents and substantial increase in the volume of diluent, it is still not possible to recover the viable cultures described above, and where the article is not suitable for the employment of membrane filtration, it can be assumed that the failure to isolate the inoculated organism is attributable to the bactericidal or bacteriostatic activity of such magnitude that treatments are not able to remove the activity. This information serves to indicate that the article is not likely to allow proliferation or contamination with the given species of microorganism. Monitoring should be continued in order to determine the inhibitory range and bactericidal activity of the article.”
► The Eurofins Microbiology Analytical Report includes the following statement to summarize the position of the USP stated above:
“Neutralization of the product is not applicable, due to the microbicidal activity of the product, it is not likely to contain specified microorganism.”
Conclusion
In today’s regulatory environment, you want to protect your brand with industry-leading testing that ensures consumer safety. When testing supplement products or ingredients specifically to meet USP or EP microbial requirements, you need a research partner offering comprehensive analysis, which includes preparatory and suitability testing to verify data accuracy, reduce false negatives and deliver the highest level of quality assurance.
For additional questions or to dive deeper on the testing considerations for USP:
