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Micro Matters: How Important Is Microbial Testing of Cannabis Products?

By Roxanne Newman

Published: Oct 02, 2019   
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“Microbial testing in the cannabis industry is extremely important, particularly for immunocompromised medical cannabis patients who can get infected easily,” says Amanda Horodyski, the passionate microbiology manager at Atlantic Test Labs Inc, a cannabis testing service company.

Giving a rare insight into her microbiological expertise, Horodyski will be a presenting at Analytical Cannabis’ webinar with her talk Microbial Contaminants: A Comparison of New and Old Methods, which will take place on the 15th of October. In anticipation of the webinar, Analytical Cannabis caught up with Horodyski to discuss the importance of microbial testing of cannabis, the biggest challenges the industry currently faces, the best microbial methods, and what’s to come in the future. 

Challenges of microbial testing for cannabis

With a lot of momentum right now, the legalization of either medicinal or recreational cannabis has the industry steadily growing. However, more transparency with regards to independent laboratory testing needs to be established.

“Laboratory testing requirements vary from state to state and a lack of standardized testing creates confusion in the industry. I think the industry needs a consensus on the best procedures with the safety of the consumer in mind,” says Horodyski.

“There are currently no standardized methods for microbial testing,” continues Horodyski. “In Maryland, independent testing facilities are required to have an ISO 17025 accreditation. This accreditation means that equipment is calibrated, methods are validated and verified, and standard operating procedures are followed. Although this accreditation is important, it does not guarantee that the best procedure is being utilized.”

However, introduction of standardized methods is not the only challenge in the current microbial testing industry; many problems arise from sample preparation and analysis.

“A problem that can arise during microbial testing is cross-contamination between samples. At Atlantic Labs, we receive samples in batches of up to 40 at a time and we must ensure that we weigh out our samples in biological safety cabinets to limit contamination. Another step we have done to mitigate cross-contamination is ensure our microbiology laboratory is separate from our chemistry laboratory and we maintain it as an ISO class 7 cleanroom,” explains Horodyski.

In addition to cross-contamination, detection of microorganisms at low levels also seems to be a prominent issue in the microbial testing industry.

“Accurately quantifying low levels of microorganisms is another big challenge. This is important because low microbial counts have the potential to replicate over time. Methods with enrichment steps are the best way to ensure that the cannabis is not contaminated,” says Horodyski.

Upon a positive microbial contaminant result, an important aspect is to identify the source of the contamination and limit reoccurrence. However, this also seems to be a challenging area.

“When samples fail for mold or bacteria, the client typically does not have the expertise to understand where the contamination came from and the preventative measures to take,” Horodyski confirms.

Fortunately, Atlantic Labs have put in place a few solutions.

“For clients and testing facilities, we use RODAC plates (replicate organism detection and counting) to test surfaces, walls, trimmers, and even living plants. Once we have identified the organisms, we can narrow down the source of contamination and recommend disinfection techniques. This is a great resource for our clients so they can prevent any future contamination,” explains Horodyski.

Best methods and the future of microbial testing

There are many different methods available for microbiological testing, with disadvantages and advantages existing for each, but the crux seems to be time.

“The incubation period is the time-limiting factor, yet it is an important step for consumer safety,” Horodyski continues. “This incubation step is required for E. coli and Salmonella species quantification and can range from 16-24 hours.”

When this lengthy incubation time is put in tandem with detection methodologies, the overall time microbial testing takes soon stacks up. So every minute saved is a big advantage.

“Traditional culture plating methods can take up to seven days, in contrast a PCR method [which] takes around two days, including the incubation period,” she says.

However, time is not the only factor to consider when comparing these methods, but also working knowledge, accuracy, and reliability.

“Culture-based techniques often result in false positives because plating is easier to contaminate and requires a trained microbiologist on staff in order to distinguish between yeast and bacteria species,” explains Horodyski.

“I recommend a real-time quantitative PCR procedure. This method is superior, because it is extremely sensitive. Traditional culture plating methods will become outdated, as it is not viable for high-volume laboratories. Ultimately, I see PCR as the method for standardized testing,” she concludes.

Amanda Horodyski will present her talk, Microbial Contaminants: A Comparison of New and Old Methods at Analytical Cannabis’ webinar on the 15th of October. You can register here to attend.

Roxanne Newman

Team Lead, Conference Production

Roxanne joined Analytical Cannabis in 2019 as conference producer, where she helps to organize our webinars, online symposia, and physical events in Europe and the US. She graduated from Anglia Ruskin University in 2019 with a 1st class Bachelor's in Biomedical Science and was also awarded the Undergraduate Prize for Physiology from the Physiological Society, London. During her studies, Roxanne also received a prestigious summer research studentship to investigate the effect of natural products on the gut epithelial.


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