Tags: petri-dish, safety, cannabis testing, total yeast and mold, plating, qPCR, microbial testing

Yvonne Helbert presents "A Growing Problem: How Temperature and Carbon Source Affect Culture Based Microbial Results" at CannMed 2022.

Many states applied regulations from the food industry to cannabis microbial testing, citing either the American Herbal Pharmacopoeia (AHP) or U.S. Pharmacopeia (USP). States that adopt these microbial regulations usually call for Total Aerobic Bacteria Count with a limit of 100,000 CFU/g.

The current microbial testing methods utilized in the cannabis industry fall into two broad categories: culture dependent (plating) and culture independent (molecular). The cannabis testing labs that use plating methods are most often using a universal media with a standard growth temperature. However, this approach fails in its mission to quantify the total microbial load because not all microorganisms are culturable, grow on the same substrate or at the same temperature, yet somehow plating has achieved “gold standard” status.

Molecular methods target the DNA sequences that are unique to the target microorganism instead of relying on its ability to grow. A common critique against molecular methods is that they detect DNA from both viable and non viable organisms; however, there are methods available to mitigate this viability concern. Additionally, an organisms viability is dependent on the culturing conditions. Plating methods will often fail to grow otherwise viable organisms if the temperature or carbon source is not suitable, thus making the live-dead debate a circular argument.

The team at Medicinal Genomics has tested both bacterial monocultures and naturally contaminated cannabis flowers to show that bacterial microorganisms cannot be grown at a universal temperature. This fact makes it very difficult to compare a culture independent molecular method to the ‘one size fits all plating method’ when trying to meet a Total Bacteria Count requirement. This data will be presented along with accompanying sequencing data to show that different organisms grow at different temperatures.

свернуть