On August 11, PathogenDx announced that they received an AOAC Performance Tested Methods Certificate for their QuantX total yeast and mold test. Six days later, on August 17, Medicinal Genomics announced that AOAC approved their PathoSEEK 5-Color Aspergillus Multiplex Assays under the same AOAC Performance Tested Methods program.
Both assays are specifically designed with cannabis and hemp testing in mind and designed to expedite and simplify microbiological testing. PathogenDx’s QuantX quantifies the total amount of yeast and mold in a sample while also measuring against safety standards.
In addition to the total yeast and mold count test, PathogenDx has also introduced a 96-well plate, improved sample preparation and new data reporting with a custom reporting portal for compliance testing.
The Medicinal Genomics platform can detect four species, including A. flavus, A. fumigatus, A. niger, and A. terreus in both flower and infused edibles. The PathoSEEK microbial testing platform uses a PCR-based assay and provides an internal plant DNA control for every reaction.
This technique verifies the performance of the assay when detecting pathogens, allegedly minimizing false negative results commonly due to set up errors and experimental conditions.
AOAC International is a standards organization that works in the cannabis testing space through their CASP program to evaluate and approve standard testing methods for the industry.
In this “Leaders in Cannabis Testing” series of articles, Green interviews cannabis testing laboratories and technology providers that are bringing unique perspectives to the industry. Particular attention is focused on how these businesses integrate innovative practices and technologies to navigate a rapidly changing landscape of regulatory constraints and B2B demand.
PathogenDx is an Arizona-based provider of microbial testing technologies. Since their inception in 2014, they have broadened their reach to 26 states in the US. In addition to cannabis product testing, PathogenDx also provides technologies for food safety testing, environmental testing and recently started offering human diagnostics testing to support COVID-19 response efforts.
We interviewed Milan Patel, CEO and co-founder of PathogenDx. Milan founded PathogenDx as a spin-off from one of his investments in a clinical diagnostics company testing for genetic markers in transplant organs. Prior to PathogenDx, Milan worked in finance and marketing at Intel and later served as CFO at Acentia (now Maximus Federal).
Aaron Green: What’s the history of PathogenDx?
Milan Patel: PathogenDx was effectively a spin-off of a clinical diagnostics company that my partner Dr. Mike Hogan, the inventor of the technology, had founded when he was a professor at the University of Arizona, but previously at Baylor Medical College back in 2002. I had invested in the company back then and I had realized that his technology had a broad and wide sweeping impact for testing – not just for pathogens in cannabis specifically, but also for pathogens in food, agriculture, water and even human diagnostics. In the last 14 months, this became very personal for every single person on the planet having been impacted by SARS-CoV-2, the viral pathogen causing Covid-19. The genesis of the company was just this, that human health, food and agricultural supply, and the environment has and will continue to be targeted by bacterial, fungal and viral pathogens impacting the safety and health of each human on the planet.
We founded PathogenDx and we pivoted the company from its original human organ transplant genetics market scope into the bigger markets; we felt the original focus was too niche for a technology with this much potential. We licensed the technology, and we repurposed it into primarily cannabis. We felt that achieving commercial success and use in the hands of cannabis testing labs at the state level where cannabis was first regulated was the most logical next step. Ultimately, our goal was and is to move into markets that are approved at the federal regulatory side of the spectrum, and that is where we are now.
Green: What year was that?
Green: So, PathogenDx started in cannabis testing?
Patel: Yes, we started in cannabis testing. We now have over 100 labs that are using the technology. There is a specific need in cannabis when you’re looking at contamination or infection.
In the case of contamination on cannabis, you must look for bacterial and fungal organisms that make it unsafe, such as E. coli, or Salmonella or Aspergillus pathogens. We’re familiar with recent issues like the romaine lettuce foodborne illness outbreaks at Chipotle. In the case of fungal organisms such as Aspergillus, if you smoke or consume contaminated cannabis, it could have a huge impact on your health. Cannabis regulators realized that to ensure public health and safety there was more than just one pathogen – there were half a dozen of these bugs, at a minimum, that could be harmful to you.
The beauty of our technology, using a Microarray is that we can do what is called a multiplex test, which means you’re able to test for all bacterial and fungal pathogens in a single test, as opposed to the old “Adam Smith” model, which tests each pathogen on a one-by-one basis. The traditional approach is costly, time consuming and cumbersome. Cannabis is such a high value crop and producers need to get the answer quickly. Our tests can give a result in six hours on the same day, as opposed to the two or three days that it takes for these other approved methods on the market.
Green: What is your business model? Is there equipment in addition to consumables?
Patel: Our business model is the classic razor blade model. What that means is we sell equipment as well as the consumables – the testing kits themselves.
The PathogenDx technology uses standard, off-the-shelf lab equipment that you can find anywhere. We didn’t want to make the equipment proprietary so that a lab has to buy a specific OEM branded product. They can use almost any equipment that’s available commercially. We wanted to make sure that labs are only paying a fraction of the cost to get our equipment, as opposed to using other vendors. Secondly, the platform is open-ended, meaning it’s highly flexible to work with the volumes that different cannabis labs see daily, from high to low.
One equipment set can process many different types of testing kits. There are kits for regulated testing required by states, as well as required environmental contamination.
Green: Do you provide any in-house or reference lab testing?
Patel: We do. We have a CLIA lab for clinical testing. We did this about a year ago when we started doing COVID testing.
We don’t do any kind of in-house reference testing for cannabis, though we do use specific reference materials or standards from Emerald Scientific, for example, or from NCI. Our platform is all externally third-party reference lab tested whether it’s validated by our external cannabis lab customers or an independent lab. We want our customers to make sure that the actual test works in their own hands, in their own facility by their own people, as opposed to just shrugging our shoulders and saying, “hey, we’ve done it ourselves, believe us.” That’s the difference.
Green: Can you explain the difference between qPCR and endpoint PCR?
Patel: The difference between PathogenDx’s Microarray is it uses endpoint PCR versus qPCR (quantitative real time PCR). Effectively, our test doesn’t need to be enriched. Endpoint PCR delivers a higher level of accuracy, because when it goes to amplify that target DNA, whether it’s E. coli, Salmonella or Aspergillus pieces, it uses all the primer reagent to its endpoint. So, it amplifies every single piece of an E. Coli (for example) in that sample until the primer is fully consumed. In the case of qPCR, it basically reaches a threshold and then the reaction stops. That’s the difference which results in a much greater level of accuracy. This provides almost 10 times greater sensitivity to identify the pathogen in that sample.
The second thing is that we have separated out how the amplified sample hybridizes to the probe. In the case of our assay, we have a microarray with a well in it and we printed the actual probe that has the sequence of E. coli in there, now driving 100% specificity. Whereas in the qPCR, the reaction is not only amplifying, but it’s also basically working with the probe. So, in that way, we have a higher level of efficiency in terms of specificity. You get a definite answer exactly in terms of the organism you’re looking for.
In terms of an analogy, let’s take a zip code for example which has the extra four digits at the end of it. In the case of endpoint PCR, we have nine digits. We have our primer probes which represent the standard five digits of a zip code, and the physical location of the probe itself in the well which serves as the extra four digits of that zip code. The analyte must match both primary and secondary parts of the nine-digit zip code for it to lock in, like a key and a lock. And that’s the way our technology works in a nutshell.
Endpoint PCR is completely different. It drives higher levels of accuracy and specificity while reducing the turnaround time compared to qPCR – down to six hours from sample to result. In qPCR, you must enrich the sample for 24 to 48 hours, depending on bacteria or fungus, and then amplification and PCR analysis can be done in one to three hours. The accuracies and the turnaround times are the major differences between the endpoint PCR and qPCR.
Green: If I understand correctly, it’s a printed microarray in the well plate?
Patel: That’s correct. It’s a 96-well plate, and in each well, you’ve now printed all the probes for all targets in a single well. So, you’re not running more than one well per target, or per organism like you are for qPCR. You’re running just one well for all organisms. With our well plates, you’re consuming fewer wells and our patented foil-cover, you only use the wells you need. The unused wells in the well plate can be used in future tests, saving on costs and labor.
Green: Do you have any other differentiating IP?
Patel: The multiplex is the core IP. The way we process the raw sample, whether it’s flower or non-flower, without the need for enrichment is another part of the core IP. We do triplicate probes in each well for E. Coli, triplicate probes for Salmonella, etc., so there are three probes per targeted organism in each of the wells. We’re triple checking that you’re definitively identifying that bug at the end of the day. This is the cornerstone of our technology.
We were just approved by the State of New York, and the New York Department of Health has 13 different organisms for testing on cannabis. Think about it: one of the most rigorous testing requirements at a state level – maybe even at a federal level – and we just got approved for that. If you had to do 13 organisms separately, whether it’s plate culture or qPCR, it would become super expensive and very difficult. It would break the very backs of every testing lab to do that. That’s where the multiplexing becomes tremendously valuable because what you’re doing is leveraging the ability to do everything as a single test and single reaction.
Green: You mentioned New York. What other geographies are you active in?
Patel: We’re active in 26 different states including the major cannabis players: Florida, Nevada, California, Arizona, Michigan, New York, Oklahoma, Colorado and Washington – and we’re also in Canada. We’re currently working to enter other markets, but it all comes down to navigating the regulatory process and getting approval.
We’re not active currently in other international markets yet. We’re currently going through the AOAC approval process for our technology and I’m happy to say that we’re close to getting that in the next couple of months. Beyond that, I think we’ll scale more internationally.
I am delighted to say that we also got FDA EUA federal level authorization of our technology which drives significant credibility and confidence for the use of the technology. About a year ago, we made a conscious choice to make this technology federally acceptable by going into the COVID testing market. We got the FDA EUA back on April 20, ironically. That vote of confidence by the FDA means that our technology is capable of human testing. That has helped to create some runway in terms of getting federalized with both the FDA and the USDA, and certification by AOAC for our different tests.
Green: Was that COVID-19 EUA for clinical diagnostics or surveillance?
Patel: It was for clinical diagnostics, so it’s an actual human diagnostic test.
Green: Last couple of questions here. Once you find something as a cannabis operator, whether its bacteria or fungus, what can you do?
Patel: There are many services that are tied into our ecosystem. For example, we work with Willow Industries, who does remediation.
There’s been a lot of criticism around DNA based technology. It doesn’t matter if it’s qPCR or endpoint PCR. They say, “well, you’re also including dead organisms, dead DNA.” We do have a component of separating live versus dead DNA with a biomechanical process, using an enzyme that we’ve created, and it’s available commercially. Labs can test for whether a pathogen is living or dead and, in many cases, when they find it, they can partner with remediation companies to help address the issue at the grower level.
Another product we offer is an EnviroX test, which is an environmental test of air and surfaces. These have 50 pathogens in a single well. Think about this: these are all the bad actors that typically grow where soil is – the human pathogens, plant pathogens, powdery mildew, Botrytis, Fusarium – these are very problematic for the thousands of growers out there. The idea is to help them with screening technology before samples are pulled off the canopy and go to a regulated lab. We can help the growers isolate where that contamination is in that facility, then the remediation companies can come in, and help them save their crop and avoid economic losses.
Green: What are you most interested in learning about?
Patel: I would prefer that the cannabis industry not go through the same mistakes other industries have gone through. Cannabis started as a cottage industry. It’s obviously doubled every year, and as it gets scaled, the big corporations come in. Sophistication, standards, maturity all help in legitimacy of a business and image of an industry. At the end of the day, we have an opportunity to learn from other industries to really leapfrog and not have to go through the same mistakes. That’s one of the things that’s important to me. I’m very passionate about it.
One thing that I’ll leave you with is this: we’re dealing with more bugs in cannabis than the food industry. The food industry is only dealing with two to four bugs and look at the number of recalls they are navigating – and this is a multi-billion-dollar industry. Cannabis is still a fraction of that and we’re dealing with more bugs. We want to look ahead and avoid these recalls. How do you avoid some of the challenges around antimicrobial resistance and antibiotic resistance? We don’t want to be going down that road if we can avoid it and that’s sort of a personal mission for myself and the company.
Cannabis itself is so powerful, both medicinally as well as recreationally, and it can be beneficial for both consumers and industry image if we do the right things, and avoid future disasters, like the vaping crisis we went through 18 months ago because of bad GMPs. We must learn from those industries. We’re trying to make it better for the right reasons and that’s what’s important to me.
Green: Okay, great. That concludes the interview. Thank you, Milan.
Patel: Thank you for allowing me to share my thoughts and your time, Aaron.
The journal Frontiers in Plant Science recently shared an important article from researchers at Simon Fraser University in British Columbia, highlighting the “Pathogens and Molds Affecting Production and Quality of Cannabis Sativa.”
As a chemist focused on the science of preventing and mitigating mold in greenhouse and indoor cannabis grow facilities, this piece was fascinating to me. Like many others, it details and explains prevalent mold like Penicillium, Cladosporium and Aspergillus – things I see in grows every day.
But wait, there’s more fungi
The research and resulting article also brought up another type of fungi – endophytic mold. Endophytic mold usually lives symbiotically with plants, or is at least beneficial for both plant and fungi.
But not always.
In the past, the industry has believed that damaging mold spores were found on the outside of the flower. When moved, that flower would release the spores and send them flying – often creating massive cross-contamination issues for indoor grows.
“While cannabis is an incredibly powerful plant in terms of its medicinal properties, it is unfortunately highly susceptible to many pest and pathogens,” says Hope Jones, PhD, CEO, Adivina & ECS. “And it is this susceptibility that is so challenging to many inexperienced or undisciplined grow operations.”
Now, however, we know that there’s another culprit to add to the list: the inner parts of the plant can also be a source of endophytic cross contamination and mold.
Since it grows inside of the plant, this fungus creates high spore counts that can cross contaminate from outside, into the flower.
Treating mold in a facility
Here’s the good news:
This seemingly bad news – that there’s a new fungus to worry about, and it is inside the flower – may actually help cannabis grows struggling with mold, and those who are following the proper protocols already.
Effective mitigation protocols can include things like treating HVAC systems, controlling humidity, using products like chlorine dioxide to treat irrigation lines, enforcing protective clothing and shoe covers for employees, reducing the amount of in-and-out for employees around grow rooms.
These are important upstream and environmentally-focused integrated pest management (IPM) programs that will usually keep facilities clean and relatively mold-free.
But if these programs are in place, and there’s still an issue, Endophytic fungi may be to blame.
If you are having ongoing mold issues but have ruled out cross-contamination and a facility without proper protocol, look to the mother plant.
“Small mistakes in agricultural practices are amplified with cannabis,” Dr. Jones continues. “And today’s propagation practices of traditional cloning add to this vulnerability. Cannabis is an annual plant and by keeping mothers in a perpetual state of vegetative growth for years, and taking repetitive cuttings produces clones in a highly stressed state. This stressed state diminishes genetic potential and weakens a plant’s ability to fight disease and pests.”
Testing for and addressing endophytic fungi
If these concerns are ringing a bell, remember, there is also a way to test for Endophytic mold.
Checking cuttings from suspected mother plants over a period of time is the best way to see if the Endophytic mold is present.
A section of the mother plant cutting is placed into a solution (for example, as outlined by the article, a very concentrated hypochlorite followed by 70% Ethanol) that will kill all of the microorganisms that are present on the surface of the plant tissues.
From there, an unadulterated dissection of the internal tissues can be extracted and cultured for quantification and identification of endophytic fungi.
“Tissue culture offers a form of genetic rebooting returning the plant to its natural genetic potential and thereby strengthening its natural ability to defend against environment assault,” says Dr. Jones. “It also allows the breeder to conduct pathogenic disease testing which provides the entire industry with a higher level of scientific certainty and analysis.”
If you find this mold inside of the mother plant, your facility’s mold problem could be a systemic issue, not an environmental one.
If you do find that Endophytic mold is causing issues, of course, you may have to destroy the mother plant.
This should not mean the end of a strain. Tissue culture on a cutting is an option that can eliminate the unwanted fungi and save the genetics. Using those genetics to regrow a mother will start fresh and avoid the intrinsic mold that was plaguing the strain prior.
The practice of checking mother plants for Endophytic mold is not yet commonplace in cannabis, but the hemp business is leading the way.
They’re testing to create very clean plants, so you don’t have issues during cultivation.
Major growers in the U.S. could save millions in lost harvests with mold mitigation. If your current IPM program isn’t doing the trick, you may want to follow in hemp’s footsteps and look inside the plant.
I think that we need to start changing the terminology around the hazards associated with cannabis from food safety hazards to product safety hazards. These hazards have not only been associated with harmful effects for those that ingest cannabis infused products, but also for those that consume the cannabis products in other ways such as inhalation (vaping or smoking). So, when we refer to these hazards as food safety hazards, the immediate thought is edibles, which misleads cultivators, manufacturers and consumers to have a false sense of security around the safety of products that are consumed in other ways.
There are several product safety hazards that have been associated with cannabis. These hazards can become a public health problem if not controlled as they could harm the consumer, regardless of the method of consumption.
Let’s take a look at the different types of hazards associated cannabis:
Biological Hazards refer to those microorganisms that can cause illness to the consumer of a product that contain them. They are not visible to the naked eye and are very dangerous when their metabolic by-products (toxins) are ingested or their spores are inhaled. The symptoms for illnesses caused by these microorganisms will vary. Consumers may experience gastrointestinal discomfort (vomiting, diarrhea), headaches, fever and other symptoms. The ingestion of these pathogens, allergens or their by-products may lead to death, if the illness is not treated on time or if the consumer of the product is immunocompromised. In addition, the inhalation of mold spores when smoking cannabis products, can lead to lung disease and death. Some of the biological hazards associated with cannabis are: Salmonella sp., E. coli, Clostridium botulinum, Aspergillus sp. and Penicillium sp.
Chemical Hazards refer to those chemicals that can be present in the plant or finished product due to human applications (pesticides), operational processes (extraction solvents and cleaning chemicals), soil properties (heavy metals), environmental contamination (radiological chemicals) or as a result of occurring naturally (mycotoxins and allergens). Consuming high concentrations of cleaning chemicals in a product can lead to a wide range of symptoms from mild rash, burning sensation in the oral-respiratory system, gastrointestinal discomfort or death. In addition, long term exposure to chemicals such as pesticides, heavy metals, radiological contaminants and mycotoxins may lead to the development of cancers.
Physical Hazards refer to those foreign materials that may be present in the plant or finished product. Foreign materials such as rocks, plastics or metals can cause harm to the consumer by chipping teeth or laceration of the mouth membranes (lips, inner cheeks, tong, esophagus, etc.) In the worst-case scenario, physical hazards may lead to choking, which can cause death due to asphyxiation.
These hazards can be prevented, eliminated or reduced to an acceptable level when foundational programs (Good Agricultural/Cultivation Practices, Good Manufacturing Practices, Allergen Management Program, Pest Control, etc.) are combined with a Food [Product] Safety Plan. These lead to a Food [Product] Safety Management System that is designed to keep consumers safe, regardless of the method of consumption.
I have been studying microorganisms for over 35 years, and the elusive critters still fascinate me! Here in Microbiology 101, I write about the foundation of knowledge on which all microbiologists build. You may have a general interest in microbiology or have concerns in your operation. By understanding microbiology, you understand the diversity of microorganisms, their source, control of microorganisms and their importance.
The term microbiology covers every living being we cannot see with the naked eye. The smallest microbe is a virus. Next in size are the bacteria, then yeast and mold cells, and the largest microbes are the protozoans. The tiny structure of a virus may be important in the plant pathology of cannabis, but will not grow in concentrates or infused products. A virus is not living, until it storms the gate of a living cell and overtakes the functions within the cell. Viruses are the number one cause of foodborne illness, with the number one virus called Norovirus. Think stomach flu. Think illness on cruise ships. Viruses are a food service problem and can be prevented by requiring employees to report sickness, have good personal hygiene including good hand washing, and, as appropriate, wear gloves. Following Good Manufacturing Practices (GMPs) is critical in preventing the transfer of viruses to a product where the consumer can be infected.
The largest microbial cell is the protozoan. They are of concern in natural water sources, but like viruses, will not grow in cannabis products. Control water quality through GMPs, and you control protozoans. Viruses and protozoans will not be further discussed here. Bacteria, yeast and mold are the focus of further discussion. As a food microbiologist, my typical application of this information is in the manufacturing of food. Because Microbiology 101 is a general article on microbiology, you can apply the information to growing, harvesting, drying, manufacture of infused products and dispensing.
It is not possible to have sterile products. Even the canning process of high temperature for an extended time allows the survival of resistant bacterial spores. Astronauts take dehydrated food into space, and soldiers receive MREs; both still contain microbes. Sterility is never the goal. So, what is normal? Even with the highest standards, it is normal to have microbes in your products. Your goal is to eliminate illness-causing microorganisms, i.e. pathogens. Along the way, you will decrease spoilage microbes too, making a product with higher quality.
Yeast and mold were discussed on CIJ in a previous article, Total Yeast & Mold Count: What Cultivators & Business Owners Need to Know. Fuzzy mold seen on the top of food left in the refrigerator too long is a quality issue, not a safety issue. Mold growth is a problem on damaged cannabis plants or cuttings and may produce mycotoxin, a toxic chemical hazard. Following Good Agricultural Practices (GAPs) will control mold growth. Once the plant is properly dried, mold will not grow and produce toxin. Proper growing, handling and drying prevents mycotoxins. Like mold, growth of yeast is a quality issue, not a safety issue. As yeast grow, they produce acid, alcohol and carbon dioxide gas. While these fermentation products are unwanted, they are not injurious. I am aware that some states require cannabis-infused products to be alcohol-free, but that is not a safety issue discussed here.
What are the sources of microorganisms?
People. Employees who harvest cannabis may transfer microorganisms to the plant. Later, employees may be the source of microbes at the steps of trimming, drying, transfer or portioning, extract processing, infused product manufacture and packaging.
Ingredients, Supplies and Materials. Anything you purchase may be a source of microorganisms. Procure quality merchandise. Remember the saying, “you get what you pay for.”
Environment. Starting with the outdoors, microbes come from wind, soil, pests, bird droppings and water. When plants are harvested outdoors or indoors, microbes come from the tools and bins. Maintain clean growing and harvesting tools in good working condition to minimize contamination with microbes. For any processing, microbes come from air currents, use of water, and all surfaces in the processing environment from dripping overhead pipes to floor drains and everything in between.
In Part 2 I will continue to discuss the diversity of microorganisms, and future articles will cover Hazard Analysis and Critical Control Points (HACCP) and food safety in more detail. What concerns do you have at each step of operations? Are you confident in your employees and their handling of the product? As each state works to ensure public health, cannabis-infused products will receive the same, if not more, scrutiny as non-cannabis food and beverages. With an understanding and control of pathogens, you can focus on providing your customers with your highest quality product.
Editor’s note: This article should serve as a foundation of knowledge for yeast and mold in cannabis. Beginning in January 2018, we will publish a series of articles focused entirely on yeast and mold, discussing topics such as TYMC testing, preventing yeast and mold in cultivation and treatment methods to reduce yeast and mold.
Cannabis stakeholders, including cultivators, extractors, brokers, distributors and consumers, have been active in the shadows for decades. With the legalization of recreational adult use in several states, and more on the way, safety of the distributed product is one of the main concerns for regulators and the public. Currently, Colorado1, Nevada and Canada2 require total yeast and mold count (TYMC) compliance testing to evaluate whether or not cannabis is safe for human consumption. As the cannabis industry matures, it is likely that TYMC or other stringent testing for yeast and mold will be adopted in the increasingly regulated medical and recreational markets.
The goal of this article is to provide general information on yeast and mold, and to explain why TYMC is an important indicator in determining cannabis safety.
Yeast & Mold
Yeast and mold are members of the fungi family. Fungus, widespread in nature, can be found in the air, water, soil, vegetation and in decaying matter. The types of fungus found in different geographic regions vary based upon humidity, soil and other environmental conditions. In general, fungi can grow in a wide range of pH environments and temperatures, and can survive in harsh conditions that bacteria cannot. They are not able to produce their own food like plants, and survive by breaking down material from their surroundings into nutrients. Mold cannot thrive in an environment with limited oxygen, while yeast is able to grow with or without oxygen. Most molds, if grown for a long enough period, can be detected visually, while yeast growth is usually detected by off-flavor and fermentation.
Due to their versatility, it is rare to find a place or surface that is naturally free of fungi or their spores. Damp conditions, poor air quality and darker areas are inviting environments for yeast and mold growth.
Cannabis plants are grown in both indoor and outdoor conditions. Plants grown outdoors are exposed to wider ranges and larger populations of fungal species compared to indoor plants. However, factors such as improper watering, the type of soil and fertilizer and poor air circulation can all increase the chance of mold growth in indoor environments. Moreover, secondary contamination is a prevalent risk from human handling during harvest and trimming for both indoor and outdoor-grown cannabis. If humidity and temperature levels of drying and curing rooms are not carefully controlled, the final product could also easily develop fungi or their growth by-product.
What is TYMC?
TYMC, or total yeast and mold count, is the number of colony forming units present per gram of product (CFU/g). A colony forming unit is the scientific means of counting and reporting the population of live bacteria or yeast and mold in a product. To determine the count, the cannabis sample is plated on a petri dish which is then incubated at a specific temperature for three to five days. During this time, the yeast and mold present will grow and reproduce. Each colony, which represents an individual or a group of yeast and mold, produces one spot on the petri dish. Each spot is considered one colony forming unit.
Why is TYMC Measured?
TYMC is an indicator of the overall cleanliness of the product’s life cycle: growing environment, processing conditions, material handling and storage facilities. Mold by itself is not considered “bad,” but having a high mold count, as measured by TYMC, is alarming and could be detrimental to both consumers and cultivators.
The vast majority of mold and yeast present in the environment are indeed harmless, and even useful to humans. Some fungi are used commercially in production of fermented food, industrial alcohol, biodegradation of waste material and the production of antibiotics and enzymes, such as penicillin and proteases. However, certain fungi cause food spoilage and the production of mycotoxin, a fungal growth by-product that is toxic to humans and animals. Humans absorb mycotoxins through inhalation, skin contact and ingestion. Unfortunately, mycotoxins are very stable and withstand both freezing and cooking temperatures. One way to reduce mycotoxin levels in a product is to have a low TYMC.
Yeast and mold have been found to be prevalent in cannabis in both current and previous case studies. In a 2017 UC Davis study, 20 marijuana samples obtained from Northern California dispensaries were found to contain several yeast and mold species, including Cryptococcus, Mucor, Aspergillus fumigatus, Aspergillus niger, and Aspergillus flavus.3 The same results were reported in 1983, when marijuana samples collected from 14 cannabis smokers were analyzed. All of the above mold species in the 2017 study were present in 13 out of 14 marijuana samples.4
Aspergillus species niger, flavus, and fumigatus are known for aflatoxin production, a type of dangerous mycotoxin that can be lethal.5 Once a patient smokes and/or ingests cannabis with mold, the toxins and/or spores can thrive inside the lungs and body.6, 7 There are documented fatalities and complications in immunocompromised patients smoking cannabis with mold, including patients with HIV and other autoimmune diseases, as well as the elderly.8, 9, 10, 11
For this reason, regulations exist to limit the allowable TYMC counts for purposes of protecting consumer safety. At the time of writing this article, the acceptable limit for TYMC in cannabis plant material in Colorado, Nevada and Canada is ≤10,000 CFU/g. Washington state requires a mycotoxin test.12 California is looking into testing for specific Aspergillus species as a part of their requirement. As the cannabis industry continues to grow and advance, it is likely that additional states will adopt some form of TYMC testing into their regulatory testing requirements.
Centre for Disease control and prevention. 2004 Outbreak of Aflatoxin Poisoning – Eastern and central provinces, Kenya, Jan – July 2004. Morbidity and mortality weekly report.. Sep 3, 2004: 53(34): 790-793
Cescon DW, Page AV, Richardson S, Moore MJ, Boerner S, Gold WL. 2008. Invasive pulmonary Aspergillosis associated with marijuana use in a man with colorectal cancer. Diagnosis in Oncology. 26(13): 2214-2215.
Szyper-Kravits M, Lang R, Manor Y, Lahav M. 2001 Early invasive pulmonary aspergillosis in a leukemia patient linked to aspergillus contaminated marijuana smoking. Leukemia Lymphoma 42(6): 1433 – 1437.
Verweii PE, Kerremans JJ, Voss A, F.G. Meis M. 2000. Fungal contamination of Tobacco and Marijuana. JAMA 2000 284(22): 2875.
Ruchlemer R, Amit-Kohn M, Raveh D, Hanus L. 2015. Inhaled medicinal cannabis and the immunocompromised patient. Support Care Cancer. 23(3):819-822.
McPartland JM, Pruitt PL. 1997. Medical Marijuana and its use by the immunocompromised. Alternative Therapies in Health and Medicine. 3 (3): 39-45.
Hamadeh R, Ardehali A, Locksley RM, York MK. 1983. Fatal aspergillosis associated with smoking contaminated marijuana, in a marrow transplant recipient. Chest. 94(2): 432-433.
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