Flavomycin inhibits conjugative transfer of plasmid-mediated antibiotic resistance genes by perturbing energy support and pilus assembly

The global dissemination of multidrug-resistant (MDR) bacteria, driven by horizontal gene transfer mechanisms such as conjugation, poses a significant threat to global public health. Conjugative plasmids facilitate the rapid spread of resistance genes, complicating clinical treatment of infections. This study investigates the inhibitory effects of flavomycin on plasmid-mediated resistance genes transfer and explores its underlying mechanisms. Our results demonstrate that flavomycin suppresses the conjugative transfer of plasmids encoding clinically important resistance genes, including blaCTX-M, blaNDM, and mcr-1 genes, in a dose-dependent manner, reducing conjugation frequencies by up to 14 to 100-fold. Mechanistically, flavomycin’s inhibition of plasmid transfer is attributed to the depletion of intracellular ATP and L-arginine, which are crucial for the energy-dependent conjugation process. Transcriptomic analyses revealed significant downregulation of genes associated with energy metabolism, while exogenous supplementation of L-arginine restored conjugation frequencies. Additionally, flavomycin suppressed the expression of mating pair formation (MPF) genes and disrupted pilus biogenesis, as confirmed by scanning electron microscopy. These findings highlight flavomycin as a potent inhibitor of horizontal gene transfer, acting through the disruption of energy metabolism and pilus assembly impairment. This work underscores the potential of targeting conjugation to combat the spread of MDR bacteria.