rifabutin + polymyxin B

**rifabutin + polymyxin B** is an investigational antibiotic combination comprising two agents: **rifabutin**, a rifamycin-class antibiotic, and **polymyxin B**, a cationic lipopeptide antibiotic. This combination is explored primarily for the treatment of infections caused by multidrug-resistant (MDR) Gram-negative bacteria, especially *Acinetobacter baumannii*. The mechanism of synergy is based on polymyxin B's ability to disrupt the bacterial outer membrane, enhancing the permeability and uptake of rifabutin. While the synergy between polymyxin B and rifampicin (another rifamycin) is well-established and documented in preclinical models, recent in vitro studies specifically show that **polymyxin B paired with rifabutin** has even greater synergistic effects than with rifampicin, suggesting a broad application against resistant *A. baumannii* strains[4]. Both agents have distinct bacterial targets (cell envelope for polymyxin B, RNA polymerase for rifabutin), enabling rapid bactericidal action and potential for minimized resistance development.