metronidazole + rifaximin + vancomycin

This is a combination of three antibiotics—metronidazole, rifaximin, and vancomycin—used primarily in the management of severe or refractory Clostridioides difficile infection (CDI). Each component has a distinct mechanism of action: - Metronidazole is a nitroimidazole antibiotic that disrupts DNA synthesis in anaerobic bacteria. - Rifaximin is a non-systemic rifamycin derivative that inhibits bacterial RNA synthesis by binding to the beta-subunit of bacterial DNA-dependent RNA polymerase. - Vancomycin is a glycopeptide antibiotic that inhibits cell wall synthesis by binding to D-alanyl-D-alanine termini in peptidoglycan precursors. This triple therapy may be considered for patients with CDI who have failed standard treatments or have recurrent/refractory disease. While metronidazole and vancomycin are established therapies for CDI, rifaximin can be added as an adjunctive agent, particularly when there is poor response to the initial regimen. The combination aims to maximize antibacterial activity against C. difficile while minimizing recurrence[1][2][4][6].