Gram-negative bacteria thrive in virtually all environments that support life. They are an important medical challenge because the outer membrane that protects them from gram staining also protects them from many antibiotics, detergents, and anti-microbial enzymes produced by the immune system. In fact, when immune cells lyse gram-negative bacteria cells it can cause a toxic reaction that can include an increased respiratory rate, and low blood pressure — a life-threatening condition known as septic shock.
What organisms are classified as BTGN?
According to the United States Pharmacopeia’s website,
“There is no strict definition of this group of micro-organisms. They are defined operationally as those micro-organisms that show growth in the stated conditions on Violet Red Bile Glucose Agar medium. They include, Gram negative bacteria that grow in the presence of bile salts, non-lactose fermenting but able to utilize glucose, e.g., some Bile Tolerant Gram Negative Bacteria includes members of the family Enterobacteriaceae, Pseudomonads and Aeromonas.”
Because there is no strict definition for BTGN, and the operational definition is based on growth in a specific medium, developing a DNA-based test is difficult. Therefore, our research led us to conclude that the species covered in our PathoSEEK Total Enterobacteriaceae assay and the PathoSEEK Pseudomonas aeruginosa assay sufficiently cover BTGN species. For ease of use, we multiplexed theses assays so customers can test both assays in one well.
Where is Bile-Tolerant Gram Negative Testing Required?
The American Herbal Pharmacopeia and the United States Pharmacopeia both list BTGN in their monographs. There are several regulatory agencies that use those documents to set their testing requirements, including:
- Canada
- Colorado*
- Connecticut
- Florida*
- Hawaii
- Illinois
- Maine
- Massachusetts
- Minnesota
- Nevada
- New Hampshire
- New Mexico
- New York
- North Dakota
- Ohio
- Pennsylvania
- Rhode Island
- Puerto Rico
- Utah
- Washington
Why Use qPCR for BTGN testing on Cannabis?
Peer-reviewed studies have shown that qPCR testing methods are able to more accurately detect and quantify bacteria species present on a cannabis sample than culture-based methods. The Bile-Tolerant Gram-Negative test looks for a specific DNA sequence that exists in all aerobic bacteria. Because of this, the Bile-Tolerant Gram-Negative test can detect all BTGN species, regardless of whether they grow in culture. Culture-based tests can only detect the species that grow in a given medium and timeframe. Conversely, qPCR can more effectively exclude off-target microbial species, such as yeasts and molds, which have been shown to grow in bactera culture medium.
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