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Abstract This study aimed to assess the ultrapure cannabidiol (CBD) antibacterial activity and to investigate the antibacterial activity of the combination CBD + polymyxin B (PB) against Gram-negative (GN) bacteria, including PB-resistant Gram-negative bacilli (GNB). We used the standard broth microdilution method, checkerboard assay, and time-kill assay. CBD exhibited antibacterial activity against Gram-positive bacteria, lipooligosaccharide (LOS)-expressing GN diplococcus (GND) (Neisseria gonorrhoeae, Neisseria meningitidis, Moraxella catarrhalis), and Mycobacterium tuberculosis, but not against GNB. For most of the GNB studied, our results showed that low concentrations of PB (≤ 2 µg/mL) allow CBD (≤ 4 µg/mL) to exert antibacterial activity against GNB (e.g., Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii), including PB-resistant GNB. CBD + PB also showed additive and/or synergistic effect against LOS-expressing GND. Time-kill assays results showed that the combination CBD + PB leads to a greater reduction in the number of colony forming units per milliliter compared to CBD and PB alone, at the same concentration used in combination, and the combination CBD + PB was synergistic for all four PB-resistant K. pneumoniae isolates evaluated. Our results show that CBD has translational potential and should be further explored as a repurposed antibacterial agent in clinical trials. The antibacterial efficacy of the combination CBD + PB against multidrug-resistant and extensively drug-resistant GNB, especially PB-resistant K. pneumoniae, is particularly promising.

Gastric metastasis is rare but it can be the initial symptom of cancer. The second leading cause of this type of metastasis is breast cancer. A lack of clinical signs and nonspecific side effects of the treatment of primary tumors can lead to the misdiagnosis of metastatic gastric cancer. Upper gastrointestinal endoscopy with biopsy and immunohistochemistry should be used for diagnosis. Treatment is palliative; it includes chemo, endocrine, and radiation therapies. Four patients with breast cancer and gastric metastasis were identified. All the patients tested positive for estrogen and progesterone receptors, and received chemotherapy and hormone therapy. One patient underwent surgery and two received radiation therapy. Patients with breast cancer and gastrointestinal symptoms should be investigated for gastric metastasis, given its morbidity and negative impact on quality of life.