Rapid Antibacterial Activity of Cannabichromenic Acid against Methicillin-Resistant Staphylococcus aureus

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) has proven to be an imminent threat to public health, intensifying the need for novel therapeutics. Previous evidence suggests that cannabinoids harbour potent antibacterial activity. In this study, a group of previously inaccessible phytocannabinoids and synthetic analogues were examined for potential antibacterial activity. The minimum inhibitory concentrations and dynamics of bacterial inhibition, determined through resazurin reduction and time-kill assays, revealed the potent antibacterial activity of the phytocannabinoids against gram-positive antibiotic-resistant bacterial species, including MRSA. One phytocannabinoid, cannabichromenic acid (CBCA), demonstrated faster and more potent bactericidal activity than vancomycin, the currently recommended antibiotic for the treatment of MRSA infections. Such bactericidal activity was sustained against low-and high-dose inoculums as well as exponential- and stationary-phase MRSA cells. Further, mammalian cell viability was maintained in the presence of CBCA. Finally, microscopic evaluation suggests that CBCA may function through the degradation of the bacterial lipid membrane and alteration of the bacterial nucleoid. The results of the current study provide encouraging evidence that cannabinoids may serve as a previously unrecognised resource for the generation of novel antibiotics active against MRSA.

Effect of Ursolic and Oleanolic Acids on Lipid Membranes: Studies on MRSA and Models of Membranes

“…After 20 h of incubation at 37 °C, 30 µL of resazurin solution (0.02% resazurin) were added to the wells for 40 min. Bacterial growth was quantified by recording fluorescence at 590 nm [ 23 ]. The lowest concentration of compound that resulted in inhibition of bacterial growth was used to determine the MICs.…”

The antimicrobial effect behind Cannabis sativa

“…73 Microscopic evaluation of the effect of CBCA against B. subtilis also showed an alteration of the bacterial membrane and nucleoid, that lead to cell lysis. 76 CBD showed a membrane-related activity causing a depolarization of the cytoplasmatic membrane and a disruption of the membrane potential in S. aureus. Furthermore, the combination CBD with bacitracin caused defects in cell division and cell envelope irregularities apparently due to a down-regulation of a very important cell division gene called ezrA.…”

“…Besides, the permeabilization of the outer membrane of Gram‐negative bacteria decreased the MIC of CBG for these bacteria (from >128 to 1 μg/ml) and allowed CBG to act in the inner membrane similarly as in Gram‐positive bacteria 73 . Microscopic evaluation of the effect of CBCA against B. subtilis also showed an alteration of the bacterial membrane and nucleoid, that lead to cell lysis 76 . CBD showed a membrane‐related activity causing a depolarization of the cytoplasmatic membrane and a disruption of the membrane potential in S .…”

“…Moreover, the endocannabinoid anandamide (AEA) and the endocannabinoid‐like, arachidonoyl serine (AraS) also were able to inhibit biofilm formation, the reduced metabolic activity of pre‐formed biofilms, and altered biofilm‐associated virulence factors such as hydrophobicity, cell aggregation, and spreading ability in MRSA 74 . Finally, recent reports demonstrated the antibacterial activity of CBD, CBDA 75 , and CBCA 76 against Gram‐positive bacteria, including MRSA.…”

Antimicrobial and Antiviral (SARS-CoV-2) Potential of Cannabinoids and Cannabis sativa: A Comprehensive Review

“…A time-kill assay showed considerable reduction of CBCA activity after 8 h of exposition to MRSA. The activity of CBCA was observed against both the exponential and stationary phases of MRSA and was independent of their cellular metabolism [ 52 ]. The killing activity of many antibiotics is attributed to their effect on dividing bacteria cells, which is crucially interrupted by the stationary phase of MRSA, resulting in higher morbidity in nosocomial infections [ 53 ].…”