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Updates to PathoSEEK® Total Count Tests

This notice was sent out to our customer distribution list in February of 2022. Posted here for any who may have missed it.

This notice is to inform you that our team is devoting its full attention to standardizing our assays to align with the new standards set by the AOAC for the industry as well as the new cannabis-specific certified reference materials (CRMs) that have become commercially available. We believe these standards and these tools will lead to better concordance across microbial testing platforms. We also believe it is important to be transparent with you regarding our process. 

First, we do not anticipate any changes to our presence-absence tests. Our Aspergillus 5-color multiplex assay and our  shiga-toxin producing E.coli (STEC) and Salmonella multiplex assay have already received AOAC certification. However, given our experience with enumeration assays, we expect there will be changes to our protocol and/or qPCR cycle threshold (Cq) to CFU equations as we calibrate them to culture-based platforms using commercially-available CRMs. 

Embracing Standardization

Last year brought many challenges to the cannabis space, but one welcomed change was the implementation of more standards for microbial detection. For many years, we have described the unique challenges we face evaluating dried flowers intended for inhalation that contain difficult-to-detect endophytes. These facts further complicate matters:

  • Each jurisdiction sets different colony forming unit (CFU) limits
  • Regulators reference undeclared “gold standard” methods
  • Few certified reference materials (CRMs) exist that are in the presence of a cannabis matrix

In 2019, AOAC released their first Standard Method Performance Requirements (SMPRs) for Aspergillus and Cannabis. AOAC currently has SMPRs for Aspergillus, Salmonella/STEC and Total Yeast and Mold Count (TYMC) for the cannabis industry. AOAC’s actions prompted several companies to certify their methods according to the newly released SMPRs.

We quickly did the same as we, too, believe it is critical for benchmarking technologies and instilling more trust in the industry. Our first AOAC-certified assays are species-specific tests that detect the four pathogenic species for Aspergillus, STEC, and Salmonella species. This makes our enumeration assays our new priority, and while AOAC has not yet released SMPRs for additional enumeration assays, we have learned a lot about this process. In fact, we plan to apply this process to all of our enumeration tests, regardless of the AOAC timelines for releasing these SMPRs.

This process will force our assays to be concordant to a culture-based standard and new CRMs that are now available for the cannabis industry. We already published our experience using our current calibration curves for Cq to CFU calculations when the Dichloran Rose-Bengal Chloramphenicol agar medium (DRBC) was used as the plating standard, and a matrix control that is unfortunately not available for wide distribution. The study demonstrated that our method detected more pathogens than the reference method on real-world cannabis samples. Unfortunately, sourcing the matrix as a nationwide standard is difficult due to interstate commercial restrictions. Regulators in several states have requested we calibrate to CRMs that are widely available. We agree with them as this is the only way we can standardize our tests across the different jurisdictional requirements in each state.

Next Steps

In the coming weeks, we will be publishing updates to our User Guides that will include new Cq to CFU equations that are calibrated to defined culture-based platforms and with specific CRMs to address these concerns. We will test these internally with 6 different lab users to understand the process variance and expand our inclusion and exclusion testing to 30 and 50 organisms respectively as seen in other AOAC SMPRs.

We anticipate Total Yeast and Mold Count (TYMC), Total Aerobic Bacterial Count (TAC),  Total Coliform, and Bile Tolerant Gram-Negative Bacteria (BTGN) methods to be updated serially in this order in the coming months.

As we do this we will be updating all of our SOPs to align in the User Guide format.

As you undoubtedly know, building tools for a nascent industry is challenging, and it often requires course correction when new information becomes available. But we remain committed to developing and providing you with the best tools possible. As always, we appreciate your understanding and cooperation, and we value your feedback and collaboration.


Please do not hesitate to reach out to our support team with any questions:

support@medicinalgenomics.com or call (866)-574-3582


Medicinal Genomics