DNA-driven pathogen detection for cannabis-hemp products


Shortcomings in traditional culture testing leave the industry in search of methods that can enumerate or count the presence of microbes whether dead or alive. Dr Jack Regan presents an alternative

DNA-driven pathogen detection for cannabis-hemp products

The seemingly limitless potential for growth of the cannabis-hemp industry has not been without hurdles. Rampant production quality issues and the on-going challenge of uniform testing standards to ensure the safety of cannabis and CBD products continue to present a challenge for both regulators and consumers.

Cannabis and hemp must be tested for potency, ensuring labelling and dosages are consistent, and it must also meet strict limits on the amount of acceptable heavy metals, toxins, pesticides, and bacterial and fungal counts. The presence of some pathogens must be zero as some are capable of causing severe and even fatal infections.

Smoking, vaping or ingesting contaminated products poses a significant risk to not just immunocompromised individuals, but also healthy consumers. Regulators in the US, for example, now require testing in each state to safeguard the consumer where products are approved for consumption and only sold in licensed dispensaries.

As the number of cannabis and CBD edibles and beverage products on the market increases, so does the challenge for regulators to control untested products. Recently, the FDA issued a warning to consumers about the unverified claims of CBD products and therapies, while also issuing warning letters to manufacturers of many untested products. But, conducting testing for cannabis is not also without its challenges.

As the number of cannabis and CBD edibles and beverage products on the market increases, so does the challenge for regulators to control untested products

Medical marijuana is now legal in 29 states in the US, nine of which have also legalised recreational marijuana. Of concern, four of the 29 states do not require testing, namely Arizona, Michigan, Montana and Rhode Island. There is always the potential that growers and producers might be more inclined to send contaminated products to these unregulated states.

In Massachusetts, where stringent regulations exist, investigative reports found that three out of four dispensaries sold cannabis positive for yeast and mould, which is a clear sign that currently used testing methods need further improvement.

Shortcomings of culture testing

The predominant testing method to confirm safety in the cannabis-hemp industry relies on culture, which is the process of placing a sample into an enriched broth that is kept in a temperature and sometimes oxygen-controlled environment for optimal microbial growth. 

However, different microbes grow under different conditions, with different nutrient, temperature, and oxygen requirements, making it impossible to have universal growth conditions. Also, the time required to confirm the presence or absence of bacteria (generally 24 hours), yeast (two days to a week), and moulds (several days to as much as four weeks) extends the time required to clear a product as being safe.

Culture growth can also significantly shift the relative abundance of different microbes, making some of them hard or impossible to detect, which could cause a false negative test result.

Aside from different growing conditions and growth times, culture methods are also unable to identify the presence of dead microbes that may have died naturally or been killed by the producer using chemical means.

The presence of dead microbes raises the risk that live microbes might also be present. As such, it is desirable to have a technology that is sensitive enough to detect the presence of dead pathogens. These shortcomings of culture testing leave the industry in search of alternative methods that can enumerate or count the presence of microbes, whether dead or alive.

A method generating excitement due to its high sensitivity is a genetic test called polymerase chain reaction (PCR), and it is capable of detecting pathogens with only a single organism present. PCR can also be multiplexed to look for many pathogens at once. Further, the detected quantities are not biased due to differences in species growth rates.

Automating the PCR processes, so they are completable by an instrument, is what the team has developed at LexaGene

PCR tests can return results in roughly an hour, and most importantly, don’t require the extra step of culturing. However, the problem with PCR is that it is very technical, forcing laboratories to hire skilled molecular biologists, which ultimately increases the cost of testing above what most laboratories may be willing to spend.

Cost reduction can be achieved using automation and microfluidics; so skilled molecular biologists are not needed, and less PCR testing material is needed when screening samples.

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Automating the PCR processes, so they are completable by an instrument, is what the team has developed at LexaGene. The analyser is a fully automated microfluidic PCR instrument, capable of processing samples and identifying several pathogens at once, including bacteria such as E. coli and salmonella, as well as yeast, and moulds.

Case study: Beta testing onsite

In the autumn of 2019, LexaGene worked with CDX Analytics, a cannabis reference laboratory that had already been manually performing PCR, to run beta testing onsite. CDX was pleased with the results of the instrument and its ability to remove cannabinoids from samples, which often inhibit the PCR reaction.

Cannabis and hemp testing generally falls into the same category as food safety testing because the THC and CBD-containing products are consumed. Products such as CBD-containing lotions are often tested by the same reference labs, if tested at all, but don’t technically fall under the food safety category.

CEO Jack Regan: Automating the PCR processes, so they are completable by an instrument, is what the team has developed at LexaGene

CEO Jack Regan: Automating the PCR processes, so they are completable by an instrument, is what the team has developed at LexaGene

Consumed products are also generally regulated by the FDA, which recommends testing laboratories use products that have been certified by the Association of Official Agriculture Chemists (AOAC) International. The Association for Public Health Laboratories (APHL) is another agency involved, and in the absence of federal guidance, has now published a document for state medical cannabis testing programmes to use in setting up their testing requirements.

The  USP, American Herbal Pharmacopeia (AHP), and ASTM International (formerly known as American Society for Testing and Materials) are also involved in developing testing guidelines to improve quality and safety for cannabis products. Needless to say, following testing requirements is confusing and still being worked on by many groups looking to improve consumer safety.

Patient safety

Guidelines are being established to protect consumers, especially immunocompromised ones. The pathogens of most interest to the cannabis industry are Salmonella, Aspergillus, Klebsiella, E. coli, Pseudomonas, Acinetobacter, Streptococcus, and Clostridium. These pathogens present a risk to consumers and can be deadly.

In contrast, pathogens such as Botrytis (Gray Mould), powdery mildew, Mucor, Penicillium, Cladosporium, and other moulds are plant pathogens. These generally do not cause disease in humans but are the focus of agricultural testing to protect crops. To the farmer, these are equally important, as plant pathogens can cause millions of dollars in damage.

Beyond the lab, better testing by producers, whether it be for food or cannabis and hemp, is the first step when it comes to identifying the presence of mould, pesticides, and other contaminants in harvested crops before they are shipped. Agricultural testing can help producers ensure the good quality of the product they are shipping and prevent issues down the line.

Improvements to testing methodologies are needed so consumers can have greater confidence in the safety of the products they are consuming. Similarly, agricultural farmers need advancements to minimise the probability of crop loss. Performing genetic testing by an automated PCR instrument is a move that can yield better profits and safety for all.

N.B. This article is featured in the January 2020 issue of Cleanroom Technology. Subscribe today and get your print copy!

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