Modification of the D3 Array Combined (Formerly the DetectX Combined) for the Detection of Aspergillus, Salmonella, and Shiga Toxin-Producing Escherichia coli in Dried Cannabis Flower with Optional Enrichment: AOAC Performance Tested MethodSM 012201.

Background: The D3 Array Combined assay (PTM 012201) is a qualitative test for the detection of Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Aspergillus terreus, Salmonella species, and a broad range of Shiga toxin-producing Escherichia coli (STEC) serogroups in cannabis matrixes. The test involves extraction of nucleic acids from samples followed by preamplification, Loci polymerase chain reaction (PCR), and subsequent Labeling PCR. The PCR amplification product is then hybridized to a DNA microarray. Detection of bacterial and fungal pathogens is determined by fluorescence.

Objective: The objective of this study was to validate the D3 Array Combined method with an optional enrichment step in dried cannabis flower (delta 9-tetrahydrocannabinol (THC) >0.3%), with the use of the Live/Dead Enrichment (LDE) reagent. The method modification was validated with optional enrichment time points at 0, 2, and 24 hours.

Methods: The evaluation followed study designs from the AOAC Microbiology guidelines and AOAC Standard Method Performance Requirements (SMPRs®) 2019.001, 2020.02, and 2020.012. The modified method was compared to SMPR confirmation procedures and an unpaired Aspergillus consensus method. The results were evaluated utilizing a probability of detection (POD) statistical model.

Results: Results showed no statistically significant difference, at the 95% and 90% confidence intervals, between the candidate method presumptive D3 Array Combined positive results and the confirmed cultural positive results at all contamination levels and enrichment time points.

Conclusions: This study provides data that demonstrate the PathogenDx D3 Array Combined is a reliable method for detection of Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Aspergillus terreus, Salmonella species, and a broad range of STEC serogroups in dried cannabis flower from 0-24 hours enrichment, for all these organisms.

Highlights: This highly sensitive method provides results within hours of sample acquisition, compared to qPCR or cultural methods where results are obtained in 2-7 days. This method also provides the option of enrichment, providing compliance options for all cannabis testing state regulations.