CBD: A Potent Antimicrobial Agent

Given that dangerous strains of bacteria are only becoming more resistant to conventional antibiotics, the need for novel treatments of bacterial infections has never been more urgent. In fact, to even speak of the emergence of a post-antibiotic era could be considered wishful thinking. In 2019, the Centers for Disease Control and Prevention wrote that scientists need to recognize the need to “stop referring to a coming post-antibiotic era—it’s already here.”


We need solutions.


For a long time, researchers have known that cannabis has antimicrobial properties. As early as 1976, Klingeren and ten Ham found that the minimum inhibitory concentrations (MIC) for both tetrahydrocannabinol (THC) and cannabidiol (CBD) fell within the range of 1-5 μg mL-1 for Gram-positive staphylococci and streptococci. These findings were supported by a report in 2008 then showed that all five major cannabinoids—CBD, THC, cannabigerol (CBG), cannabichromene (CBC), and cannabinol (CBN)—exhibited MIC values within the 0.5-2 μg mL-1 range against methicillin-resistant Staphylococcus aureus (MRSA) strains.


Now, a new report published just this year by an international team based partly out of the University of Queensland in Australia has found even more good news, particularly about CBD. In their January paper published in Communications Biology, the authors wrote that they discovered that CBD has “consistent activity against a wide range of Gram-positive bacteria, including a variety of drug-resistant strains. Intriguingly, this activity extends to a small subset of Gram-negative bacteria, including pathogens of concern such as Neisseria gonorrhoeae.


In all, the researchers found that CBD demonstrated antimicrobial activity against 20 types of Gram-positive bacteria, including MRSA, multidrug resistant (MDR) Streptococcus pneumoniae, Enterococcus faecalis, Clostridioides difficile, and Cutibacterium acnes, as well as four Gram-negative bacteria strains that are each responsible for serious infections: Neisseria gonorrhoeae (gonorrhea), Neisseria meningitides (meningitis), Moraxella catarrhalis (upper respiratory infections), and Legionella pneumophila (Legionnaire’s disease). They also found that CBD exhibited an extremely low toxicity when exposed to human cells and human embryonic kidney cells.


While this is very positive news, there is one very important drawback: CBD's limited systemic activity due to its propensity for serum binding, thereby making it largely ineffective in treating broad, bacterial infections. To create a successful treatment for bacterial infection based on CBD, future research will need to focus on developing synthetic analogs that can mimic its antimicrobial properties while making it less susceptible to serum binding.


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