Could a Cannabis Compound Beat Antibiotic Resistance?
A common cannabinoid might be the answer to combating drug-resistant superbugs, according to new results published by researchers in the journal .
The paper, authored by an interdisciplinary group at McMaster University, Canada, describes the screening of 18 different cannabinoids in investigation of their antibacterial properties, and the successful use of one of these compounds,
, in killing methicillin-resistant Staphylococcus aureus (MRSA), one of the most common hospital superbugs.
CBG and others show antibiotic activity
In the first part of the study, researchers focused on five major cannabinoids: cannabichromene (CBC), cannabidiol (CBD), cannabigerol (CBG), cannabinol (CBN), and tetrahydrocannabinol (THC), as well as a selection of their acidic precursors and synthetic isomers.
“In this study, we investigated 18 commercially available cannabinoids and they all showed antibiotic activity, some much more than others,” said study lead Eric Brown, professor of biochemistry and biomedical sciences at McMaster, .
“The one we focused on was a non-psychoactive cannabinoid called CBG, as it had the most promising activity,” Brown explained. “CBG proved to be marvelous at tackling pathogenic bacteria. The findings suggest real therapeutic potential for cannabinoids as antibiotics.”
The cannabinoids were tested using static abiotic solid-surface assays, where they were assessed by how well they were able to inhibit the formation and growth of biofilms produced by MRSA. In these tests, CBG was seen to be the most potent inhibitor, with as little as 0.5 𝜇g/ml able to reduce biofilm formation by 50 percent.
These can be particularly dangerous, as they are extremely difficult to remove and can form on the skin and on the surface of medical implants – increasing the possibilities of repeat infection and infection spread.
Spurred on by its performance in these biofilm studies, the researchers decided to go further and assess the in vivo efficacy of CBG using a mouse model. Once again, CBG was able to successfully combat MRSA, with its efficacy directly comparable to that of vancomycin, an
that is often used in the treatment of superbugs.
Early days for CBG antibiotic research
As well as holding strong potential as a treatment for MRSA, the researchers also believe that CBG could be developed further into a much more general use antibiotic.
MRSA bacteria are classified as , meaning that they have a single, thick cell wall. In contrast, gram negative bacteria have separate inner and outer cell membranes, making these infections generally much harder to treat. Common gram-negative bacteria species include E. coli, salmonella, and legionella.
In initial tests, the McMaster University researchers found CBG and other cannabinoids to be relatively ineffective at inhibiting the drug-resistant gram-negative bacteria used in this study, E. coli. However, when used in conjunction with small quantities of the antibiotic polymyxin B, which is known to disruptor of the outer membrane for such bacteria, CBG was also able to combat drug-resistant gram-negative pathogens.
This “hidden broad-spectrum antibacterial activity,” as the researchers refer to it in their paper, further lends credence to the idea of the cannabinoids as an important area for antibiotics research.
CBG, not an instant fix
Despite the immense promise demonstrated by CBG in the study, the researchers emphasize that the compound is not some immediately available ‘readymade’ fix for antibiotic resistance.
CBG was observed to exhibit some toxicity towards otherwise ‘good’ host cells, making CBG more of an important lead or a starting point, rather than a finished pharmaceutical product.
“It opens a therapeutic window, but a narrow one, to develop this into a drug,” said Brown. “The next steps are to try to make the compound better in that it is more specific to the bacteria and has a lower chance of toxicity.”
Other cannabinoids, including CBD, have previously shown promise as antibiotic candidates. Speaking to Analytical Cannabis last year, Dr Mark Blaskovich, a researcher at the University of Queensland, discussed how it might not even be necessary to understand an antibiotic’s mechanism of action in order to progress with its development.
“Even for antibiotics that have been around for a long time, like polymyxins which were discovered in the 1940s, we still don't know, completely, their mechanisms of action,” he explained.
“So, if you know it's effective at killing the bacteria, and it’s not inducing resistance – which appears to be the case for CBD – there shouldn't be any significant roadblocks in advancing it further, from a regulatory perspective.”