While lots of testing still needs to be done, if only a fraction of the health claims for cannabis are proven true, it may well go down as one of the greatest medicinal plants in history. Adding to its growing number of uses, investigators at the University of Queensland’s Institute for Molecular Bioscience’s Centre for Superbug Solutions—in collaboration with Botanix Pharmaceuticals, an early-stage drug discovery company investigating topical uses of synthetic cannabidiol for a range of skin conditions—found that cannabidiol was remarkably effective at killing a wide range of Gram-positive bacteria, including bacteria that have become resistant to other antibiotics.

Amazingly, the researchers reported they found that cannabidiol is active against bacteria that are often responsible for many serious infections, such as Staphylococcus aureus and Streptococcus pneumoniae, with a potency similar to that of established antibiotics such as vancomycin or daptomycin. The researchers reported their findings yesterday at the annual meeting of the American Society for Microbiology in San Francisco.

“Given cannabidiol’s documented anti-inflammatory effects, existing safety data in humans, and potential for varied delivery routes, it is a promising new antibiotic worth further investigation,” noted lead study investigator Mark Blaskovich, PhD, a senior research chemist at the University of Queensland. “The combination of inherent antimicrobial activity and potential to reduce damage caused by the inflammatory response to infections is particularly attractive.”

Cannabidiol, the main non-psychoactive chemical compound extracted from cannabis and hemp plants, has been approved by FDA for the treatment of a form of epilepsy and is being investigated for a number of other medical conditions, including, anxiety, pain, and inflammation. While there is limited data to suggest cannabidiol can kill bacteria, the drug has not been thoroughly investigated for its potential as an antibiotic.

“We assessed the antimicrobial activity of synthetically produced cannabidiol, free from isolation-dependent impurities that may confound biological testing results obtained with plant extracts,” the authors wrote. “Cannabidiol was tested in a suite of standard antimicrobial assays, starting with broth microdilution assays against a range of aerobic and anaerobic Gram-positive bacteria. Time-kill, resistance induction, and biofilm disruption experiments were also conducted, along with an assessment of in vivo activity against MRSA in a murine neutropenic thigh infection model.”

Importantly, the drug retained its activity against bacteria that have become highly resistant to other common antibiotics. Under extended exposure conditions that lead to resistance against vancomycin or daptomycin, cannabidiol did not lose effectiveness. Moreover, cannabidiol was also effective at disrupting biofilms, a physical form of bacteria growth that leads to difficult-to-treat infections.

“Cannabidiol was remarkably effective at killing a range of Gram-positive (but not Gram-negative) bacteria, with broth microdilution MICs similar to clinical antibiotics such as vancomycin and daptomycin,” the authors concluded. “Notably, activity was retained against-resistant strains of S. aureus (MRSA, VISA, VRSA), Streptococcus pneumoniae (MDR), and E. faecalis (VRE). Cannabidiol was bactericidal, showed low levels of propensity to induce resistance, and was active against MRSA biofilms.”