Rifaximin

Rifaximin, a gastrointestinal-selective antibiotic, binds the β-subunit of bacterial DNA-dependent RNA polymerase, resulting in inhibition of bacterial RNA synthesis. Rifaximin susceptibility is higher against Gram-positive strains (MIC: 0.03-5 mg/ml) compared to Gram-negative bacteria (MIC: 8-50 mg/mL)^[1][2]. In Vitro: Rifaximin has a good inhibitory activity against Staphylococcus, Streptococcus, Enterococcus, Escherichia coli, Shigella, Salmonella, Bacillus cereus, Moraxella catarrhalis, Haemophilus influenzae, Haemophilus ducreyi, Bacteroides bivius-disiens, Gardnerella vaginalis, Lactobacillus spp.,Mobiluncus spp.,Neisseria gonorrhoeae, Pseudomonas and Acinetobacter . Rifaximin rarely causes side effects^[1].
Rifaximin (0.1, 1.0 and 10.0 µM) causes significant and concentration-dependent reduction of cell proliferation, cell migration and PCNA expression in the Caco-2 cells vs. untreated cells^[2].
Rifaximin (0.1-10 μM) downregulates Akt/mTOR and p38MAPK/NF-κB pathways through a PXR-dependent mechanism^[2]. In Vivo: Rifaximin administration (30 or 50 mg/kg/day) increases survival rates of colitic mice and reduces colitis severity by improvement of wasting syndrome, histologic scores, decrease in colon IL-2, IL-12, IFN-gamma and TNF-alpha (protein and mRNA) levels, and diminishes colon myeloperoxidase (MPO) activity^[3].