Environmental Screening of a Cannabis Production and Processing Facility: A Comparison of an Environmental DNA Microarray and Traditional Microbiological Plating Methods: Page 3 of 3

December 18, 2019
Abstract / Synopsis: 

As the cannabis industry continues to expand and become more heavily regulated, the need for screening tools that detect microbial contamination increases. While screening has primarily focused on the raw product, there has been little emphasis on the actual facilities in which that product is processed, which has the potential to be a contaminating source for the cannabis product. The following case study was performed to demonstrate the utility and necessity of environmental screening in a cannabis production and processing facility. Samples were collected for assessment of microbial contamination across 11 locations throughout the facility. Each sample was assessed by traditional microbiological plating and an environmental DNA microarray to compare the effectiveness of both methods.


This study highlights the utility of environmental screening as a tool to evaluate potential microbial contamination within an agricultural production and processing facility. While largely harmless, many of the microorganisms detected in this surveillance carry potential risks to both human health and agricultural products and yields.

Highly ubiquitous in the environment and agricultural samples, it is unsurprising that Pseudomonas spp. was the most prevalent isolate in this study; while some species of Pseudomonas can be harmful, many serve as plant commensals and are not especially concerning (5). Conversely, the detection of organisms such as Golovinomyces spp. and Cladosporium spp. are more concerning. The presence of Golovinomyces spp. is particularly problematic from an agricultural perspective because these species are a major cause of powdery mildew in plants, which is capable of reducing or destroying agricultural yields (6). By comparison, Cladosporium spp. is relatively ubiquitous in the air, but can be a significant allergen and can pose health concerns in susceptible individuals (7). Without environmental screening, microbial contamination such as this may go undetected, imposing risks to agricultural yields and human health. Provided such screenings, steps can be taken to reduce contamination, modify decontamination procedures as necessary, and monitor facilities to ensure rapid detection of any recurrence of contamination.

Further, this study emphasizes the advantages of utilizing the PathogenDx EnviroX microarray technology in microbial detection as compared to traditional microbiological plating. In addition to producing results in a more cost-effective and rapid manner as compared to traditional plating, the EnviroX microarray displayed equal or greater sensitivity in detecting microbial contamination in all sample cases (Table II). In fact, there were many cases in which the agar plates displayed no growth but EnviroX detected contamination, for both bacterial and fungal isolates. In addition, EnviroX provided speciation of many of the contaminants present, a distinguishing characteristic that could not be determined by the agar plating alone. Notably, without these species-level identifications, the observed temporal and spatial relationships could not have been ascertained. While some patterns can be observed from the agar plates, the species-level identifications could not be made without further experimental analysis. Furthermore, without species-level identifications, the degree of risk associated with the specific contaminants present cannot be fully appreciated. Taken together, these data support the usefulness and need for environmental screening in agricultural processing facilities, and highlights the critical advantages in utilizing microarray technology for microbial detection, as opposed to traditional microbiological methods.

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About the Authors

Chelsea Adamson is a microbiologist and Benjamin A. Katchman is a principal scientist at PathogenDX in Tucson, Arizona. Direct correspondence to: [email protected]

How to Cite this Article

C. Adamson and B.A. Katchman, Cannabis Science and Technology 2(6), 54-61 (2019).