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Novel Cannabis Assay Detects Microorganisms in Rapid Time

By Leo Bear-McGuinness

Published: Nov 06, 2018   
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A novel DNA-based microarray assay can identify potentially life-threatening microorganisms in less than 6 hours – a faster turnaround time than traditional plate-based enumeration methods.

The technology, which has been developed by PathogenDx, has a host of other benefits, too. Assay samples don’t need to be enriched or incubated before testing and the technology can identify multiple microorganisms simultaneously. 

As many microorganisms present in cannabis samples can pose a risk to individuals with weakened immune systems, PathogenDx’s rapid microbiological testing technology could allow labs to screen more samples, more effectively and offer better protection to consumers.  

What Makes the Assay so Effective?

“It’s revolutionary,” says Milan Patel, Co-Founder, and CEO, PathogenDx. A leading testing technology company for the cannabis, agricultural and botanical industries, PathogenDx has always been at the cutting edge of microorganism assays. 

“Traditional microbial methods can take up to 72 hours or longer after enrichment and plating,” he explains. “And in the case of real-time PCR, the additional steps of DNA extraction, purification and quantitation add more time and cost to the process”. In comparison, PathogenDx’s new assay “can process raw samples to fully tested results, in less than 6 hours.”

In addition, the technology operates on a precise DNA-specific level, meaning it’s able to identify the exact species of any pathogens present. A major improvement over traditional colony counting methods, this greater accuracy is on trend with tightening state regulations and could give testing labs more confidence when deciding if a product is safe for consumption. 

“Classical microbial is not molecular,” explains Patel. “It requires a person to enrich and incubate a sample for days until the colonies have grown and then counting the cells on a grid. Typically, it relies on a microbiologist to count the colonies of those pathogenic cells under a microscope. This is subjective and is highly variable, compared to our DNA-based method.”

Currently, Californian State Regulations require the detection of less than 1 colony forming unit per gram (CFU/g) for six dangerous microorganisms: Salmonella, E. coli and four species of Aspergillus. Not only can PathogenDx’s technology enable a user to count down to 0.1 CFU/g, but its measurements are triplicated (recorded three times) to confidently ascertain the presence of any pathogenic organisms.

Lastly, the new method can search for multiple microorganisms at once – one of the many features that reduce the required testing time. This ability allows PathogenDx to screen for all six microbial species as specified by Californian regulations in one rapid scan. 

“What this means for a lab is significant testing efficiency in terms of being able to test more samples per day, with less labor and cost, and faster turn-around,” adds Patel. 

How Does the Assay Compare to Other Methods?

To test the efficiency of their assay, PathogenDx had its instrument analyzed by Steep Hill Laboratories, one of the leading licensed cannabis analytical services in California. Led by Dr Reggie Gaudino, the Steep Hill team validated the assay by testing it against a traditional microbial plate enumeration method. 

After conducting over 1,400 individual experiments which tested the assay’s limits of detection, its sensitivity, specificity and reproducibility, the team found PathogenDx’s method to be “both rapid and precise in identifying which organisms are present in a viable or non-viable state”. In other words, the assay could detect and identify pathogens without a delay, even though the pathogenic cells present may have been stressed or injured.

This instantaneous feature could be a crucial benefit for any lab detecting Aspergillus species. As fungi, Aspergillus species have different growth patterns to bacteria, meaning precise counts can’t always be determined. PathogenDx’s assay could help address this issue by using any mycotoxins present to identify the species – something traditional methods can’t achieve. 

However, plate culture methods aren’t without their merits – they are known as ‘The Gold Standard’, after all. For example, the plate method the Steep Hill team used to compare with the PathogenDx technology required further growth on solid media. This added time gave the bacteria and fungi a chance to multiply and become detectable pathogens. Plus, in the past, Dr Reggie Gaudino and other Steep Hill scientists have championed the benefits of total yeast and mold counts in pathogen detection. 

In the end, though, the PathogenDx method was more sensitive with respect to the detection of organisms in the absence of growth – a valuable feature if time is of the essence. In addition, the technology also distinguished between the presence of non-viable and viable organisms after a 24-hour enrichment period.

Verifying the assay against the federal standards of the AOAC, FDA, and USDA, the Steep Hill team also showed that the DNA-based method was able to outperform the recovery of pathogenic strains down to 1 colony forming unit compared to plate culture.,In another validation study conducted by Brightside Scientific, which compared enriched versus unenriched testing samples, the assay was found to be superior in comparing 1 CFU in 10 replicate samples to plate cultures. 

What’s Next for the PathogenDx Assay?

For the health and safety of cannabis consumers, products require thorough testing and screening to ensure pathogenic microorganisms aren’t present. As neglecting or poorly performing this duty can lead to sickness and even the death of consumers, dependable and proven testing technologies are a must for any analytical cannabis lab. 

“We already know the lack of tolerance the public and governments have for an outbreak of E. coli or Salmonella in restaurant chains like Chipotle,” says Patel. “Consumers will become increasingly aware that improperly tested cannabis can offer this threat as well and will demand change”.

The DNA-based assay developed by PathogenDx has been proven to be a more rapid and effective method for determining the presence of pathogens in cannabis samples. They hope is that it will be adopted by analytical cannabis labs across the country in order to effectively screen samples, faster.

“We hope that the validation tests will attract more labs to purchase our equipment, so they can become more efficient in identifying an unsafe product from a safe product, in a faster and more economical way,” says Patel. “We believe our products to be disruptive to the testing industry and will contribute to better safety for the public, both within the US and around the globe”.

Leo Bear-McGuinness

Science Writer & Editor

Leo joined Analytical Cannabis in 2019. From research to regulations and analysis to agriculture, his writing covers all the need-to-know news for the cannabis industry. He holds a Bachelor's in Biology from Newcastle University and a Master's in Science Communication from the University of Edinburgh.


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