Cannabidiol (CBD), derived from the Cannabis plant, has shown potential in dentistry for its antimicrobial properties, particularly against oral bacteria. Denture-associated infections, a common issue among denture wearers, present a challenge in antimicrobial enhancements to poly(methyl methacrylate) (PMMA), the primary material for dentures due to its favorable physical and aesthetic qualities. To address this, researchers developed PMMA denture coatings infused with CBD nanoparticles. The CBD coatings were synthesized using UV curing and characterized via 1H NMR, SEM, and FTIR spectroscopies. Antimicrobial activity was assessed against Staphylococcus aureus, Escherichia coli, and Streptococcus agalactiae. CBD demonstrated significant bactericidal effects on Gram-positive bacteria with a minimum inhibitory concentration (MIC) of 2–2.5 µg/mL and a minimum bactericidal concentration (MBC) of 10–20 µg/mL but was ineffective against planktonic Gram-negative bacteria. However, biofilm studies revealed a 99% reduction in biofilm growth for both Gram-positive and Gram-negative bacteria on CBD-infused PMMA compared to standard PMMA. The CBD disrupted bacterial cell walls, causing lysis. Dissolution studies indicated effective release of CBD molecules, crucial for antimicrobial efficacy. This study highlights CBD’s potential for antibiotic-free denture coatings, reducing dental biofilms and plaque formation, and improving oral health outcomes.

Staphylococcus aureus poses a significant threat in both community and hospital settings due to its infective and pathogenic nature combined with its ability to resist the action of chemotherapeutic agents. Methicillin-resistant S. aureus (MRSA) represents a critical challenge. Metal-chelating thiosemicarbazones (TSCs) have shown promise in combating MRSA and while previous studies hinted at the antimicrobial potential of TSCs, their mechanisms of action against MRSA are still under investigation. We screened a chemical library for anti-staphylococcal compounds and identified a potent molecule named R91 that contained the NNSN structural motif found within TSCs. We identified that R91 and several structural analogs exhibited antimicrobial activity against numerous S. aureus isolates as well as other Gram-positive bacteria. RNAseq analysis revealed that R91 induces copper and oxidative stress responses. Checkerboard assays demonstrated synergy of R91 with copper, nickel, and zinc. Mutation of the SrrAB two-component regulatory system sensitizes S. aureus to R91 killing, further linking the oxidative stress response to R91 resistance. Moreover, R91 was found to induce hydrogen peroxide production, which contributed to its antimicrobial activity. Remarkably, no mutants with elevated R91 resistance were identified, despite extensive attempts. We further demonstrate that R91 can be used to effectively treat an intracellular reservoir of S. aureus in cell culture and can reduce bacterial burdens in a murine skin infection model. Combined, these data position R91 as a potent TSC effective against MRSA and other Gram-positive bacteria, with implications for future therapeutic development.

Aims:The mechanism by which synovial fluid (SF) kills bacteria has not yet been elucidated, and a better understanding is needed. We sought to analyze the antimicrobial properties of exogenous copper in human SF against Staphylococcus aureus. Methods:We performed in vitro growth and viability assays to determine the capability of S. aureus to survive in SF with the addition of 10 µM of copper. We determined the minimum bactericidal concentration of copper (MBC-Cu) and evaluated its sensitivity to killing, comparing wild type (WT) and CopAZB-deficient USA300 strains. Results:UAMS-1 demonstrated a greater sensitivity to SF compared to USA300 WT at 12 hours (p = 0.001) and 24 hours (p = 0.027). UAMS-1 died in statistically significant quantities at 24 hours (p = 0.017), and USA300 WT survived at 24 hours. UAMS-1 was more susceptible to the addition of copper at four (p = 0.001), 12 (p = 0.005), and 24 hours (p = 0.006). We confirmed a high sensitivity to killing with the addition of exogenous copper on both strains at four (p = 0.011), 12 (p = 0.011), and 24 hours (p = 0.011). WT and CopAZB-deficient USA300 strains significantly died in SF, demonstrating a MBC-Cu of 50 µM against USA300 WT (p = 0.011). Conclusion:SF has antimicrobial properties against S. aureus, and UAMS-1 was more sensitive than USA300 WT. Adding 10 µM of copper was highly toxic, confirming its bactericidal effect. We found CopAZB proteins to be involved in copper effluxion by demonstrating the high sensitivity of mutant strains to lower copper concentrations. Thus, we propose CopAZB proteins as potential targets and use exogenous copper as a treatment alternative against S. aureus.

Research background. Herbal antimicrobials exist in plants and their derived compounds. One such compound is cannabidiol (CBD) extracted from the plant, Cannabis Sativa, , also referred to as hemp or marijuana, has drawn interest for its alleged antibacterial and antioxidant abilities. With the increasing problem of antibiotic resistance and the desire to reduce antibiotics in the food industry, researchers are exploring the potential of cannabinoids as an alternative antimicrobial agent. The use of cannabidiol (CBD) in food and beverage products is a growing trend, it is also important for manufacturers to approach this new area with more studies. Milk is a key component in the production of most dairy produce. The products made from milk usually undergo various processes such as pasteurization, fermentation, curdling, and aging to create the final product. This study aims to examine the potential of CBD isolate as a antimicrobial agent which can be used in dairy products to reduce microbial growth and extend their shelf life. . Experimental approach. This paper investigated the antilmicrobial properties of CBD against L. monocytogenes in milk as the key solvent to perform studies. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of CBD in TSB was carried out at 37 degrees C in 24 h. CBD's antilisterial activity was found for whole milk and skim milk at 4 degrees C for 3 days by analyzing their respective growth and kill curves. Results and conclusions Both the MIC and MBC for L. monocytogenes was found to be 2 mu g/mL measured by dilution series and plating, respectively. CBD significantly slowed the growth of listeria populations in milk but its effectiveness of CBD was dependant on the fat content of milk. In this paper, we have discussed the potential for using and improving CBD as a preservative to combat L. monocytogenes in dairy products that use milk as a primary ingredient.

Osteoarthritis is the most prevalent joint disease in the United States, with many patients requiring surgical replacement of the affected joint. The number of joint arthroplasty procedures performed each year is increasing, and infection is a leading cause of implant failure. Staphylococcus aureus is the most frequently isolated organism associated with periprosthetic joint infections of the knee or hip, and due to the emergence of antibiotic-resistant strains, treatment options are limited. Here, we show that synovial fluid from osteoarthritic patients is iron restrictive toward S. aureus and, for strains representing the clonal lineages USA100, USA200, USA400, and USA600, bactericidal. Remarkably, community-associated methicillin-resistant S. aureus (CA-MRSA) strain USA300-LAC was highly resistant to synovial fluid killing but could be sensitized to killing by mutation of the GraXRS regulatory system and GraXRS-regulated mprF gene or by small-molecule inhibition of GraR. Thus, we propose the GraXRS-VraFG regulatory system and mprF as targets for future therapeutics for treatment of S. aureus bone and joint infections.IMPORTANCE Osteoarthritis, a degenerative disease that results in the breakdown of joint cartilage and underlying bone, is the most prevalent joint disease in the United States. Surgical intervention, including total joint replacement, is a clinically effective procedure that can help to restore the patient's quality of life. Unfortunately, joint replacement procedures come with a risk of infection that is estimated to occur in 1 to 2% of cases, and periprosthetic joint infection (PJI) is a leading cause of implant failure, requiring revision surgery. Staphylococcus aureus is well known for its ability to cause PJIs and was found to be the most frequently isolated organism from PJIs of the knee or hip. Antibiotic-resistant strains can often limit treatment options. In this study, we demonstrate that the MRSA strain LAC can resist killing and grow in human synovial fluid from osteoarthritic knees. Furthermore, we show that the GraXRS regulatory system is required for the displayed synovial fluid resistance. We further demonstrate that a small-molecule inhibitor of GraR sensitizes LAC to synovial fluid, validating the Gra system as a therapeutic target for the treatment of PJIs in humans.

Due to its limited treatment options, multi-drug resistant bacteria such as Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) still remains a serious public health threat. The creation of new compelling antimicrobial materials, antibiotics and optional methodologies, which are successful against resistant microbes, is earnestly required. The legalization of cannabis in Canada has provided a new opportunity to investigate the antimicrobial studies of both extracts and individual cannabinoids. This study investigates pure cannabidiol (CBD) isolated from Cannabis sativa by using a methodology of extraction, purification, characterization, and quantification of CBD. The shredded plant material was dissolved in ethanol, with the extract further purified using supercritical fluid chromatography (SFC) to obtain purified CBD. Product purity was confirmed by HPLC and NMR spectroscopy. CBD’s antibacterial activity on MRSA strain USA300 bacteria was studied using dilution series in liquid culture and disk diffusion assays to provide the minimum inhibitory concentration (MIC) and minimal bactericidal concentrations (MBC). The results showed that CBD exhibited a significant bactericidal effect on MRSA with the MIC value of 2.5 µg/mL and MBC of 10 µg/mL. CBD powder form gave a higher antimicrobial activity than its oil form in terms of the inhibition zone. This study shows that CBD exhibits good antimicrobial impact against the MRSA strain showing its utility for enabling a new antibiotic free method for treating MRSA infections. Keywords—CBD, antimicrobial activity, MRSA

Staphylococcus aureus is a significant cause of human infection. Here, we demonstrate that mutations in the transcriptional repressor of purine biosynthesis, purR, enhance the pathogenic potential of S. aureus. Indeed, systemic infection with purR mutants causes accelerated mortality in mice, which is due to aberrant up-regulation of fibronectin binding proteins (FnBPs). Remarkably, purR mutations can arise upon exposure of S. aureus to stress, such as an intact immune system. In humans, naturally occurring anti-FnBP antibodies exist that, while not protective against recurrent S. aureus infection, ostensibly protect against hypervirulent S. aureus infections. Vaccination studies support this notion, where anti-Fnb antibodies in mice protect against purR hypervirulence. These findings provide a novel link between purine metabolism and virulence in S. aureus.

Staphylococcus lugdunensis has acquired recognition as a relatively new and serious pathogen that is often clinically misidentified as S. aureus. To cause infection S. lugdunensis must circumvent host immunity, including the innate defenses presented by professional phagocytes such as macrophages. In this study, we demonstrate for the first time that macrophages of murine and human origin are not microbicidal towards S. lugdunensis and that phagocytosed S. lugdunensis remain viable within infected macrophages over an extended period (>24 h). Interestingly, phagocytosed S. lugdunensis, which fail to replicate, also do not intoxicate host cells, thus distinguishing the intracellular lifestyle of S. lugdunensis from that of S. aureus. Dextran pulse‐chase and LAMP‐1 immuno‐localization studies reveal that phagocytosed S. lugdunensis take up residence inside LAMP‐1‐positive phagolysosomes where the bacteria persist for at least 24 hours. Phagocytosed S. lugdunensis are modified within macrophages such that they are sensitized to in vitro stresses imposed by antimicrobial peptide treatment (e.g. polymyxin B), exposure to non‐ionic detergent (e.g. Triton‐X100), and the staphylococcal selective medium mannitol salt agar. We further demonstrate that optimal survival of S. lugdunensis requires O‐acetylated peptidoglycan since a S. lugdunensis oatA mutant, which is more sensitive to killing by lysozyme than WT, survived to a lesser extent in the phagosome. Through pharmacological disruption of lysosome function, either prior to or post phagocytosis, we demonstrate that S. lugdunensis bacteria can be coaxed into escaping the phagolysosome and replicating within both murine macrophages and primary human macrophages. Notably, however, intracellularly replicating S. lugdunensis fail to intoxicate infected macrophages as indicated by the host cells' ability to phagocytose IgG‐opsonized targets and remain refractory to vital dye staining. We propose that macrophages harboring S. lugdunensis in vivo represent a bacterial reservoir and events that disrupt macrophage function would allow these bacteria to proliferate whilst remaining protected from extracellular immune factors.Support or Funding InformationCanadian Institutes of Health ResearchThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Staphylococcus lugdunensis is a commensal bacterium that can cause serious infection suggesting an ability to circumvent aspects of host immunity. We demonstrate here that macrophages fail to kill ingested S. lugdunensis and the bacteria persist for extended periods, without replicating, within mature LAMP-1-positive phagolysosomes. Phagocytosed S. lugdunensis also do not intoxicate host cells in contrast to Staphylococcus aureus. Optimal survival of S. lugdunensis requires O-acetylated peptidoglycan because an oatA mutant, which is more sensitive to killing by lysozyme than wild type, survived to a lesser extent in macrophages. In vitro models of macrophage infection reveal that viable intracellular S. lugdunensis bacteria can be made to grow by pharmacologic perturbation of phagosome function or by phagocyte intoxication by S. aureus toxins. Remarkably, replicating S. lugdunensis is not constrained by LAMP-1 and phosphatidylserine-positive endomembranes, which is distinct from S. aureus that replicates within phagolysosomes. In vivo, S. lugdunensis can also reside in the murine Kupffer cell where the bacteria persist without replicating and require oatA to resist killing in vivo. The intracellular environment of the macrophage represents a niche where S. lugdunensis can exist while protected from extracellular immune factors and may serve as a reservoir from which these bacteria could disseminate.