DNA Testing Methods

Posted by Milan Patel on June 15, 2018



With recent and ongoing advancements in molecular biology, DNA testing has become a useful instrument to assess the safety, quality and integrity of the cannabis supply chain.

DNA testing can be used in different contexts by different operators in the industry including researchers, business operators and regulatory authorities. State regulators may use DNA testing methodology to assess the safety and authenticity of samples, and uncover any breaches in legal use of pesticides.

Emerging technologies have the potential to simplify the DNA technology methods, although the uptake of these by the cannabis industry may be limited for some time by cost and availability. DNA is an improved testing method that will assist in the protection of consumers’ health and safeguard producers from fraud and illegal commerce.

Cannabis Microbial Testing Methods

California requires testing for some pathogenic microbial impurities that some labs are not fully prepared to accurately test or identify. Some impurities, like shiga toxin-producing E.Coli (STEC) and salmonella can usually be correctly identified under a microscope by an expert, but cannabis testing labs that are currently using culture-based tests for microbials will have a very difficult time validating their method on Aspergillus, for example.

Pathogenic strains of Aspergillus species, which includes A. fumigates, A. flavus, A. niger, and A. terreus are notoriously difficult to grow in culture medium. It takes days and a too-early culture conclusion can lead to severe under-reporting of Aspergillus. In addition to this major drawback, A. niger looks remarkably like brasiliensis, and can be easily mistaken. A false negative or false positive in this example can do a world of harm to the consumer or the grower. This is just one example of culture-based testing shortcomings.

Labs using DNA sequencing technology do not have issues with this type of mistaken identity. DNA-based pathogen testing for cannabis can definitively distinguish microbial pathogens that look alike because they do not rely on the human eye to make the distinction. Similar to DNA crime lab testing, DNA sequencing technology results have a high level of microbial sensitivity, microbial specificity and reliability.

The shortcomings in older culture-based tests represent a serious concern to cannabis growers, and especially to cannabis patients who may be immune-compromised. One false negative can ruin their recovery, or worse.

The pinpoint accuracy of DNA-based pathogen testing for the cannabis industry is getting a lot of attention from regulators and many labs that are quickly incorporating it into their testing protocols.

Research has demonstrated that often what grows in a culture medium is not fully or truly representative of the microbial composition on cannabis flower sample and may lead to false positive results. The plated tests were not specifically designed to be used on cannabis. They don’t take into account the plant’s unique combination of beneficial microbes, or the fertilizer and pesticides, which can influence what grows in the culture.

Detection Methods

With more surgical precision than the standard culture-based methods, DNA-based methods are superior to culture-based methods. It is better suited to the cannabis industry because it is more specific and faster than plate counting methods. Labs and growers prefer certain DNA-based testing kits, like PathogenDx,  because they are relatively easy to use for anyone with basic molecular biology training and can be smoothly integrated into a protocol. No specialized mycology training is required.

DNA-based testing systems are less open to interpretation since specific genetic signatures are used rather than colony morphology. Multiplex solutions, like PathogenDx, can test all state-regulated microbial organisms in one simple test. With the bandwidth and flexibility to adapt to the ever-changing state microbial testing guidelines, they also provide maximum detection down to 0.1 CFU for pathogenic organisms. Accurate results are obtained quickly, helping with valuable turnaround time; everyone in the industry likes that!

It is important to choose the right DNA-based method. Some claim they multiplex organisms, but labs need to check validation data and make sure specificity is not compromised over sensitivity. This is where PathogenDx has developed the ideal solution; not only does PathogenDx multiplex all organisms in one reaction, but it delivers the balance of sensitivity and specificity. PathogenDx ensures you do not get false negatives and false positives while truly delivering results to the letter of the law.

DNA-based evidence is often a slam dunk in other industries. Microbial testing on cannabis is no different. This technology is a great fit for the cannabis industry.

If you are a cannabis testing lab, contact us today at or call us at 800-641-5751 to learn why PathogenDx DNA-based testing is your best choice for microbial testing.

Topics: cannabis testing

Written by Milan Patel