As of now, there are only two cannabis testing labs in Connecticut. Last year, regulators in the state approved a request from AltaSci Labs to raise the testing limits for yeast and mold at their lab from 10,000 colony forming units per gram (cfu/g) up to 1 million. The other lab, Northeast Laboratories, has kept their limits at 10,000 cfu/g.
Connecticut state flag
According to CTInsider.com, that request was approved privately and unannounced and patients were notified via email of the change. Ginny Monk at CTInsider says patients enrolled in Connecticut’s medical cannabis program have been outspoken over safety concerns, a lack of transparency and little voice in the decision-making process.
Connecticut has a small medical cannabis market with roughly 54,000 patients in the program and they are in the midst of readying the launch of their adult-use market.
A yeast and mold test showing colony forming units
Following public outcry regarding the change at the recent Social Equity Council meeting, state regulators have proposed a change to microbial testing regulations. The new rule will set the limit at 100,000 cfu/g for yeast and mold and requires testing for specific forms of Aspergillus, a more harmful type of mold.
Kaitlyn Kraddelt, spokeswoman for Connecticut’s Department of Consumer Protection, the agency in charge of testing regulations for the state’s cannabis program, told CTInsider.com that they involved several microbiologists to develop the new rule. “These new standards, which were drafted in consultation with several microbiologists, will prohibit specific types of yeast and mold in cannabis flower that may cause injury when inhaled and allow 10^5 cfu/g of colony forming units that have no demonstrated injurious impact on human health,” says Krasselt.
The rule change is now undergoing a public comment period, after which the Attorney General’s office will get a review period. If approved, it’ll head to the legislature, where a committee has 45 days to act on it.
Increasing cannabis use across the US has come with increased scrutiny of its health effects. Regulators and healthcare providers are not just concerned about the direct effects of inhaling or consuming cannabinoids, however, but also about another health risk: microbial contamination in cannabis products. Like any other crop, cannabis is susceptible to contamination by harmful pathogens at several points throughout the supply chain, from cultivation and harvesting to distribution. Many state regulators have set limits for microbial populations in cannabis products. Consequently, testing labs must adopt efficient screening protocols to help companies remain compliant and keep their customers safe.
Some of the pathogens common to cannabis flower include Aspergillus fungus species such as A. flavus, A. fumigatus, A. niger and A. terreus. Cannabis might also harbor harmful E. coli and Salmonella species, including Shiga toxin-producing E. coli (STEC). Regulations vary by state, but most have set specific thresholds for how many colony forming units (CFUs) of particular species can be present in a sellable product.
The gold standard method for detecting microbes is running cultures.
Growers and testing labs need to develop a streamlined approach to remain viable. Current methods, including running cultures on every sample, can be expensive and time-consuming, but by introducing a PCR-based screening step first, which identifies the presence of microbial DNA – and therefore the potential for contamination – laboratories can reduce the number of cultures they need to run, saving money and time.
The Risk of Aspergillus Contamination
Contamination from Aspergillus species can bring harm to cannabis growers and their customers. The state of Michigan is currently undergoing the largest cannabis recall in its history from Aspergillus contamination.
If contamination grows out of control, the pathogen can damage the cannabis plant itself and lead to financial losses. Aspergillus can also cause serious illness in consumers, especially those that are immunocompromised. If an immunocompromised person inhales Aspergillus, they can develop aspergillosis, a lung condition with a poor prognosis.
A Two-Step Screening Process
The gold standard method for detecting microbes is running cultures. This technique takes weeks to deliver results and can yield inaccurate CFU counts, making it difficult for growers to satisfy regulators and create a safe product in a timely manner. The use of polymerase chain reaction (PCR) can greatly shorten the time to results and increase sensitivity by determining whether the sample has target DNA.
Using PCR can be expensive, particularly to screen for multiple species at the same time, but a qPCR-based Aspergillus detection assay could lead to significant cost savings. Since the average presumptive positive rate for Aspergillus contamination is low (between 5-10%), this assay can be used to negatively screen large volumes of cannabis samples. It serves as an optional tool to further speciate only those samples that screened positive to comply with state regulations.
Conclusion
Overall, screening protocols have become a necessary part of cannabis production, and to reduce costs, testing labs must optimize methods to become as efficient as possible. With tools such as PCR technology and a method that allows for initial mass screening followed by speciation only when necessary, laboratories can release more samples faster with fewer unnecessary analyses and more success for cannabis producers in the marketplace.
In 1887, Julius Petri invented a couple of glass dishes, designed to grow bacteria in a reproducible, consistent environment. The Petri dish, as it came to be known, birthed the scientific practice of agar cultures, allowing scientists to study bacteria and viruses. The field of microbiology was able to flourish with this handy new tool. The Petri dish, along with advancements in our understanding of microbiology, later developed into the modern field of microbial testing, allowing scientists to understand and measure microbial colonies to detect harmful pathogens in our food and water, like E. coli and Salmonella, for example.
The global food supply chain moves much faster today than it did in the late 19th century. According to Milan Patel, CEO of PathogenDx, this calls for something a little quicker. “Traditional microbial testing is tedious and lengthy,” says Patel. “We need 21st century pathogen detection solutions.”
Milan Patel first joined the parent company of PathogenDx back in 2012, when they were more focused on clinical diagnostics. “The company was predominantly built on grant funding [a $12 million grant from the National Institute of Health] and focused on a niche market that was very specialized and small in terms of market size and opportunity,” says Patel. “I realized that the technology had a much greater opportunity in a larger market.”
Milan Patel, CEO of PathogenDx Photo: Michael Chansley
He thought that other markets could benefit from that technology greatly, so the parent company licensed the technology and that is how PathogenDx was formed. Him and his team wanted to bring the product to market without having to obtain FDA regulatory approval, so they looked to the cannabis market. “What we realized was we were solving a ‘massive’ bottleneck issue where the microbial test was the ‘longest test’ out of all the tests required in that industry, taking 3-6 days,” says Patel. “We ultimately realized that this challenge was endemic in every market – food, agriculture, water, etc. – and that the world was using a 140-year-old solution in the form of petri dish testing for microbial organisms to address challenges of industries and markets demanding faster turnaround of results, better accuracy, and lower cost- and that is the technology PathogenDx has invented and developed.”
While originally a spinoff technology designed for clinical diagnostics, they deployed the technology in cannabis testing labs early on. The purpose was to simplify the process of testing in an easy approach, with an ultra-low cost and higher throughput. Their technology delivers microbial results in less than 6 hours compared to 24-36 hours for next best option.
The PathogenDx Microarray
Out of all the tests performed in a licensed cannabis testing laboratory, microbial tests are the longest, sometimes taking up to a few days. “Other tests in the laboratory can usually be done in 2-4 hours, so growers would never get their microbial testing results on time,” says Patel. “We developed this technology that gets results in 6 hours. The FDA has never seen something like this. It is a very disruptive technology.”
When it comes to microbial contamination, timing is everything. “By the time Petri dish results are in, the supply chain is already in motion and products are moving downstream to distributors and retailers,” Patel says. “With a 6-hour turnaround time, we can identify where exactly in the supply chain contaminant is occurring and spreading.”
The technology is easy to use for a lab technician, which allows for a standard process on one platform that is accurate, consistent and reproduceable. The technology can deliver results with essentially just 12 steps:
Take 1 gram of cannabis flower or non-flower sample. Or take environmental swab
Drop sample in solution. Swab should already be in solution
Vortex
Transfer 1ml of solution into 1.5ml tube
A look at how the sample is added to the microarray
Conduct two 3-minute centrifugation steps to separate leaf material, free-floating DNA and create a small pellet with live cells
Conduct cell lysis by adding digestion buffer to sample on heat blocks for 1 hour
Conduct Loci enhancement PCR of sample for 1 hour
Conduct Labelling PCR which essentially attaches a fluorescent tag on the analyte DNA for 1 hour
Pipette into the Multiplex microarray well where hybridization of sample to probes for 30 minutes
Conduct wash cycle for 15 minutes
Dry and image the slide in imager
The imager will create a TIFF file where software will analyze and deliver results and a report
Their DetectX product can test for a number of pathogens in parallel in the same sample at the same time down to 1 colony forming unit (CFU) per gram. For bacteria, the bacterial kit can detect E. coli, E. coli/Shigella spp., Salmonella enterica, Listeria and Staph aureus, Stec 1 and Stec 2 E.coli. For yeast and mold, the fungal kit can test for Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger and Aspergillus terreus.
Their QuantX is the world’s first and only multiplex quantification microarray product that can quantify the microbial contamination load for key organisms such as total aerobic bacteria, total yeast & mold, bile tolerant gram negative, total coliform and total Enterobacteriaceae over a dynamic range from 100 CFU/mL up to 1,000,000 CFU/mL.
Not all of the PathogenDx technology is designed for just microbial testing of cannabis or food products. Their EnviroX technology is designed to help growers, processors or producers across any industry identify areas of microbial contamination, being used as a tool for quality assurance and hazard analysis. They conducted industry-wide surveys of the pathogens that are creating problems for cultivators and came up with a list of more than 50 bacterial and fungal pathogens that the EnviroX assay can test for to help growers identify contamination hotspots in their facilities.
Using the EnviroX assay, growers can swab surfaces like vents, fans, racks, workbenches and other potential areas of contamination where plants come in contact. This helps growers identify potential areas of contamination and remediate those locations. Patel says the tool could help growers employ more efficient standard operating procedures with sanitation and sterilization, reducing the facility’s incidence of pathogens winding up on crops, as well as reduction in use of pesticides and fungicides on the product.
Deploying this technology in the cannabis industry allowed Milan Patel and the PathogenDx team to bring something new to the world of microbial testing. Their products are now in more than 90 laboratories throughout the country. The success of this technology provides another shining example of how the cannabis market produces innovative and disruptive ideas that have a major impact on the world, far beyond cannabis itself.
Microbial contamination on cannabis products represents one of the most significant threats to cannabis consumers, particularly immunocompromised patients who are at risk of developing harmful and potentially fatal infections.
As a result, regulatory bodies in the United States and Canada mandate testing cannabis products for certain microbes. The two most popular methods for microbial safety testing in the cannabis industry are culture-based testing and quantitative polymerase chain reaction (qPCR).
When considering patient safety, labs should choose a method that provides an accurate account of what is living on the sample and can specifically target the most harmful microbes, regardless of the matrix.
1. The Method’s Results Must Accurately Reflect the Microbial Population on the Sample
The main objective of any microbial safety test is to give the operator an indication of the microbial population present on the sample.
Figure 1: MA data collected directly from plant material before and after culture on 3M petrifilm and culture-based platforms.
Culture-based methods measure contamination by observing how many organisms grow in a given medium. However, not all microbial organisms grow at the same rate. In some cases, certain organisms will out-compete others and as a result, the population in a post-culture environment is radically different than what was on the original sample.
One study analyzed fifteen medicinal cannabis samples using two commercially available culture-based methods. To enumerate and differentiate bacteria and fungi present before and after growth on culture-based media, all samples were further subjected to next-generation sequencing (NGS) and metagenomic analyses (MA). Figure 1 illustrates MA data collected directly from plant material before and after culture on 3M petrifilm and culture-based platforms.
The results demonstrate substantial shifts in bacterial and fungal growth after culturing on the 3M petrifilm and culture-based platforms. Thus, the final composition of microbes after culturing is markedly different from the starting sample. Most concerning is the frequent identification of bacterial species in systems designed for the exclusive quantification of yeast and mold, as quantified by elevated total aerobic count (TAC) Cq values after culture in the total yeast and mold (TYM) medium. The presence of bacterial colonies on TYM growth plates or cartridges may falsely increase the rejection rate of cannabis samples for fungal contamination. These observations call into question the specificity claims of these platforms.
The Live Dead Problem
Figure 2: The enzyme is instantaneously inactivated when lysis buffer is added
One of the common objections to using qPCR for microbial safety testing is the fact that the method does not distinguish between live and dead DNA. PCR primers and probes will amplify any DNA in the sample that matches the target sequence, regardless of viability. Critics claim that this can lead to false positives because DNA from non-viable organisms can inflate results. This is often called the Live-Dead problem. However, scientists have developed multiple solutions to this problem. Most recently, Medicinal Genomics developed the Grim Reefer Free DNA Removal Kit, which eliminates free DNA contained in a sample by simply adding an enzyme and buffer and incubating for 10 minutes. The enzyme is instantaneously inactivated when lysis buffer is added, which prevents the Grim Reefer Enzyme from eliminating DNA when the viable cells are lysed (see Figure 2).
2. Method Must Be Able to Detect Specific Harmful Species
Figure 3: The team spiked a known amount of live E. coli into three different environments
Conversely, qPCR assays, such as the PathoSEEK, are designed to target DNA sequences that are unique to pathogenic Aspergillus species, and they can be run using standard qPCR instruments such as the Agilent AriaMx. The primers are so specific that a single DNA base difference in the sequence can determine whether binding occurs. This specificity reduces the frequency of false positives in pathogen detection, a frequent problem with culture-based cannabis testing methods.
Additionally, Medicinal Genomics has developed a multiplex assay that can detect the four pathogenic species of Aspergillus (A. flavus, A. fumigatus, A. niger, and A. terreus) in a single reaction.
3. The Method Must Work on Multiple Matrices
Figure 4: The team also placed TSB without any E. coli onto a petrifilm to serve as a control.
Marijuana infused products (MIPs) are a very diverse class of matrices that behave very differently than cannabis flowers. Gummy bears, chocolates, oils and tinctures all present different challenges to culture-based techniques as the sugars and carbohydrates can radically alter the carbon sources available for growth. To assess the impact of MIPs on colony-forming units per gram of sample (CFU/g) enumeration, The Medicinal Genomics team spiked a known amount of live E. coli into three different environments: tryptic soy broth (TSB), hemp oil and hard candy. The team then homogenized the samples, pipetted amounts from each onto 3M™ Petrifilm E. coli / Coliform Count (EC) Plates, and incubated for 96 hours. The team also placed TSB without any E. coli onto a petrifilm to serve as a control. Figures 3 and 4 show the results in 24-hour intervals.
Table 1: DNA was spiked into various MIPs
This implies the MIPs are interfering with the reporter assay on the films or that the MIPs are antiseptic in nature.
Many MIPs use citric acid as a flavoring ingredient which may interfere with 3M reporter chemistry. In contrast, the qPCR signal from the Agilent AriaMx was constant, implying there is microbial contamination present on the films, but the colony formation or reporting is inhibited.
Table 3: SenSATIVAx DNA extraction can successfully lyse the cells of the microbesTable 2: Different numbers of DNA copies spiked into chocolate
This is not an issue with DNA-based methods, so long as the DNA extraction method has been validated on these matrices. For example, the SenSATIVAx DNA extraction method is efficient in different matrices, DNA was spiked into various MIPs as shown in Table 1, and at different numbers of DNA copies into chocolate (Table 2). The SenSATIVAx DNA extraction kit successfully captures the varying levels of DNA, and the PathoSEEK detection assay can successfully detect that range of DNA. Table 3 demonstrates that SenSATIVAx DNA extraction can successfully lyse the cells of the microbes that may be present on cannabis for a variety of organisms spiked onto cannabis flower samples.
Across the country, there is a patchwork of regulatory requirements that vary from state to state. Regulations focus on limiting microbial impurities (such as mold) present in cannabis in order for consumers to receive a safe product. When cultivators in Colorado and Nevada submit their cannabis product to laboratories for testing, they are striving to meet total yeast and mold count (TYMC) requirements.In a nascent industry, it is prudent for state regulators to reference specific testing methodologies so that an industry standard can be established.
TYMC refers to the number of colony forming units present per gram (CFU/g) of cannabis material tested. CFU is a method of quantifying and reporting the amount of live yeast or mold present in the cannabis material being tested. This number is determined by plating the sample, which involves spreading the sample evenly in a container like a petri dish, followed by an incubation period, which provides the ideal conditions for yeast and mold to grow and multiply. If the yeast and mold cells are efficiently distributed on a plate, it is assumed that each live cell will give rise to a single colony. Each colony produces a visible spot on the plate and this represents a single CFU. Counting the numbers of CFU gives an accurate estimate on the number of viable cells in the sample.
The plate count methodology for TYMC is standardized and widely accepted in a variety of industries including the food, cosmetic and pharmaceutical industries. The FDA has published guidelines that specify limits on total yeast and mold counts ranging from 10 to 100,000 CFU/g. In cannabis testing, a TYMC count of 10,000 is commonly used. TYMC is also approved by the AOAC for testing a variety of products, such as food and cosmetics, for yeast and mold. It is a fairly easy technique to perform requiring minimal training, and the overall cost tends to be relatively low. It can be utilized to differentiate between dead and live cells, since only viable living cells produce colonies.
Petri dish containing the fungus Aspergillus flavus. Photo courtesy of USDA ARS & Peggy Greb.
There is a 24 to 48-hour incubation period associated with TYMC and this impedes speed of testing. Depending on the microbial levels in a sample, additional dilution of a cannabis sample being tested may be required in order to count the cells accurately. TYMC is not species-specific, allowing this method to cover a broad range of yeast and molds, including those that are not considered harmful. Studies conducted on cannabis products have identified several harmful species of yeast and mold, including Cryptococcus, Mucor, Aspergillus, Penicillium and Botrytis Cinerea. Non-pathogenic molds have also been shown to be a source of allergic hypersensitivity reactions.The ability of TYMC to detect only viable living cells from such a broad range of yeast and mold species may be considered an advantage in the newly emerging cannabis industry.
After California voted to legalize recreational marijuana, state regulatory agencies began exploring different cannabis testing methods to implement in order to ensure clean cannabis for the large influx of consumers.
Unlike Colorado, California is considering a different route and the recently released emergency regulations require testing for specific species of Aspergillus mold (A. fumigatus, A. flavus, A. niger and A. terreus). While Aspergillus can also be cultured and plated, it is difficult to differentiate morphological characteristics of each species on a plate and the risk of misidentification is high. Therefore, positive identification would require the use of DNA-based methods such as polymerase chain reaction testing, also known as PCR. PCR is a molecular biology technique that can detect species-specific strains of mold that are considered harmful through the amplification and analysis of DNA sequences present in cannabis. The standard PCR testing method can be divided into four steps:
The double stranded DNA in the cannabis sample is denatured by heat. This refers to splitting the double strand into single strands.
Primers, which are short single-stranded DNA sequences, are added to align with the corresponding section of the DNA. These primers can be directly or indirectly labeled with fluorescence.
DNA polymerase is introduced to extend the sequence, which results in two copies of the original double stranded DNA. DNA polymerases are enzymes that create DNA molecules by assembling nucleotides, the building blocks of DNA.
Once the double stranded DNA is created, the intensity of the resulting fluorescence signal can uncover the presence of specific species of harmful Aspergillus mold, such as fumigatus.
These steps can be repeated several times to amplify a very small amount of DNA in a sample. The primers will only bind to the corresponding sequence of DNA that matches that primer and this allows PCR to be very specific.
PCR testing is used in a wide variety of applications Photo courtesy of USDA ARS & Peggy Greb.
PCR is a very sensitive and selective method with many applications. However, the instrumentation utilized can be very expensive, which would increase the overall cost of a compliance test. The high sensitivity of the method for the target DNA means that there are possibilities for a false positive. This has implications in the cannabis industry where samples that test positive for yeast and mold may need to go through a remediation process to kill the microbial impurities. These remediated samples may still fail a PCR-based microbial test due to the presence of the DNA. Another issue with the high selectivity of this method is that other species of potentially harmful yeast and mold would not even be detected. PCR is a technique that requires skill and training to perform and this, in turn, adds to the high overall cost of the test.
Both TYMC and PCR have associated advantages and disadvantages and it is important to take into account the cost, speed, selectivity, and sensitivity of each method. The differences between the two methodologies would lead to a large disparity in testing standards amongst labs in different states. In a nascent industry, it is prudent for state regulators to reference specific testing methodologies so that an industry standard can be established.
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