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

The rapid global dissemination of multidrug-resistant (MDR) bacteria, primarily driven by horizontal gene transfer through conjugative plasmids, poses a significant challenge to modern medicine. Conjugation enables the efficient spread of antibiotic resistance genes across bacterial populations, severely compromising the efficacy of existing therapies. This study examined the inhibitory potential of flavomycin against plasmid-mediated transmission of clinically relevant resistance genes and elucidated the underlying molecular mechanisms. Results showed that flavomycin markedly reduced the conjugative transfer of plasmids carrying bla_CTX-M, bla_NDM, and mcr-1 genes in a dose-dependent manner, decreasing conjugation frequencies by approximately 14- to 100-fold. Mechanistic analysis indicated that inhibition of plasmid transfer resulted from intracellular depletion of ATP and L-arginine, both essential for the energy-dependent conjugation process. Transcriptomic analyses revealed broad suppression of genes involved in energy metabolism, while supplementation with exogenous L-arginine restored conjugation frequencies. Additionally, flavomycin down-regulated the expression of mating pair formation (MPF) genes and disrupted pilus biogenesis, as confirmed by scanning electron microscopy. These findings identify flavomycin as a potent inhibitor of horizontal gene transfer, acting through disruption of bacterial energy metabolism and impairment of pilus assembly, and highlight its potential as a promising strategy to limit the propagation of MDR bacteria.