Dronedarone hydrochloride targets cardiolipin and phosphatidylglycerol to increase colistin susceptibility in gram-negative pathogens.

Treating multidrug-resistant (MDR) infections has become progressively dependent on limited therapeutic options, particularly polymyxins, such as colistin. This reliance has precipitated a concerning epidemiological trend: the emergence and global propagation of plasmid-mediated (mcr) as well as chromosome-mediated polymyxin resistance. Consequently, escalating resistance rates will certainly lead to diminished clinical efficacy of colistin, correlating with elevated mortality in septic patients who already face therapeutic limitations. Utilizing antimicrobial potentiators to restore the sensitivity of resistant pathogens to polymyxins represents a promising pharmacological strategy for reinvigorating the clinical utility of these agents. Here, we demonstrate that dronedarone hydrochloride (DH) exhibits significant synergistic bactericidal activity with colistin against colistin-resistant strains. DH enhances the antibacterial potency of colistin by approximately 32-fold (MIC from 8 μg/mL to 0.25 μg/mL in ExPEC ECQ001), effectively reversing resistance phenotypes. In vivo therapeutic efficacy studies demonstrated that combination therapy achieved a statistically significant reduction in bacterial burden compared to colistin therapy alone. Mechanistic studies revealed that DH has the capacity for specific molecular interactions with two critical phospholipid components: cardiolipin and phosphatidylglycerol (PG) in bacterial membranes. This binding induces membrane disruption, impairs energy production, and stimulates oxidative stress, which collectively augment the bactericidal activity of colistin. These findings position DH as a viable antibiotic adjuvant with translational potential for combination therapies against MDR pathogens. The dual targeting of membrane integrity and redox homeostasis presents a strategic advantage in circumventing conventional resistance mechanisms, thereby extending the application potential of colistin in contemporary antimicrobial regimens.IMPORTANCEColistin remains a last resort antibiotic for treating infections caused by extensively drug-resistant pathogens. However, the emergence of colistin resistance has significantly compromised its clinical utility. Our research identifies and characterizes that dronedarone hydrochloride (DH) restores bacterial sensitivity to colistin by binding to cardiolipin (CL) and phosphatidylglycerol (PG). Mechanistic studies revealed that DH bound specifically to CL and PG, thereby enhancing membrane disruption, impairing energy production, and stimulating oxidative stress levels, which collectively augment the bactericidal activity of colistin. These findings present DH as a lead compound for combating colistin resistance, while offering novel mechanistic insights into its role as a colistin potentiator.