Why did MGC make updates to the TYM testing process?

On June 16th, 2022 MGC released an updated workflow for TYM testing. This included a new User Guide and a new Validation document. Why?

This update is a result of months of torture testing our TYM process, during which: 

  • Six different internal lab users tested the same samples to understand the process variance
  • A beta-testing site ran the updated protocol on real-life samples and achieved concordance with plating
  • Inclusion and exclusion testing was expanded to 30 and 50 organisms respectively as seen in other AOAC SMPRs

Download the PathoSEEK® Total Yeast and Mold Detection Assay with SenSATIVAx® & TLP Extraction Validation Document

 

New PT Recommendation for flower

In order for your lab to validate the new PathoSEEK® Total Yeast & Mold Detection Assay with SenSATIVAx® Extraction protocol, we recommend the following standard from NSI: 

  • PT Express Catalog Number CMPT-085B from NSI Lab Solutions 

This new CRM includes both yeast and mold organisms, which more accurately represents what labs encounter on real-life samples and achieves better concordance when comparing qPCR and plating results.

 

Important information regarding Cq to CFU conversion equations for TYM Testing:

The Medicinal Genomics Total Yeast and Mold assay targets ITS (Internal Transcribed Spacer) regions in the yeast and filamentous fungi genomes.   The prevalence of these regions can vary by 10-100x between organisms.

Mathematically, The equation assumes 1 genomic copy = 1 PCR target. Yeast have ~20 ITS regions per genome and molds have 50-100 ITS regions which means when amplifying these organisms in situ, you’re not amplifying 1 copy, but 20-100 copies per copy of the genome.  This increases the sensitivity of qPCR when targeting a region present in multiple copies per genome.

Plate enumerations for yeast and mold is highly variable due to 4 variables involved that can vastly affect results

  1. Time the plate is incubated
  2.  Carbon source
  3. Temperature used
  4. Organisms that do not culture

Using an assay that targets a genomic region present in 20-100 copies is less variable than juggling the 4 previously mentioned growth factors. In addition, having 10X higher sensitivity or 100X higher sensitivity isn't a deficit when you are comparing it to a ‘gold standard’ of plating which also accepts that many microbes are unculturable.