A team of Canadian researchers have shown that cannabigerol (CBG) can be effective in combatting drug-resistant bacteria like MRSA, sparking hopes that the compound may offer a new defence against superbugs.
The researchers tested five different Cannabis compounds for possible antibiotic effects, finding that one of the most promising interactions was between CBG and methicillin-resistant Staphylococcus aureus (MRSA). MRSA is one of the most common bacterial superbugs found in hospitals.
The compound was found to kill a significant number of MRSA microbes in test tube studies. In addition, the non-psychoactive compound also killed ‘persistor’ cells, which are particularly resistant to antibiotics. These cells are known to cause repeat infections. Further, CBG killed MRSA microfilm, which often persists on the skin and medical implants.
Following the findings, the researchers went on to test the effects of CBG on MRSA-infected mice. Preliminary findings from that study, which has not yet been published, suggests that CBG can be as effective in treating the infection as vancomycin – an antibiotic which is commonly used, and considered to be a last line of defence against drug-resistant bacteria. Full results from that research are currently under review by the ACS Infectious Diseases journal.
Eric Brown, a microbiologist who led the work at McMaster University in Hamilton, Ontario, said cannabinoids were “clearly great drug-like compounds”, but noted it was early days in assessing the compounds for use in the clinic. “There is much work to do to explore the potential of the cannabinoids as antibiotics from the safety standpoint,” he said.
In the study, Brown, and his team, describes how the rapid global spread of drug resistance, caused by microbes developing mutations that protect them against antibiotics, has driven an urgent need to explore new sources of drugs.
Bacteria fall into two classes depending on the makeup of their cells. MRSA bugs are known as gram positive bacteria, and have a single, thick cell membrane. Gram negative bugs differ in having inner and outer cell membranes, and these infections can be harder to treat. In the World Health Organization’s priority list of drug-resistant bacteria, all three ranked as a “critical” priority are gram negative, namely Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacteriaceae.
Brown found that CBG and other cannabinoids did not work well against gram negative multi-drug resistant bugs. But the team went on to show that when CBG was used with small quantities of polymyxin B, an existing antibiotic that disrupts the outer membrane of gram negative bacteria, the cannabis compound wiped out the drug-resistant pathogens.
To study the compound, Brown’s team synthesised CBG in the lab using the chemicals olivetol and geraniol. “We are now pursuing the required paperwork to work with a wide variety of cannabinoids,” he said.
The study is of particular interest as antibacterial compounds produced by cannabis normally are not very effective inside the body. Given the positive results that the McMaster team have produced in mice, there is renewed hope for using these compounds as effective tools in the fight against bacteria.
“These are likely made as a defence mechanism to protect the plant from bacterial and fungal infections, but to date have not been very useful for human infections as they really only work outside the body,” comments Mark Blaskovich, who studies antibiotic cannabis compounds at the University of Queensland. “That’s what makes this new report potentially exciting – evidence that cannabigerol is able to treat a systemic infection in mice.”