Hybrids of 3-Hydroxypyridin-4(1<i>H</i>)-ones and Long-Chain 4-Aminoquinolines as Potent Biofilm Inhibitors of <i>Pseudomonas aeruginosa</i> Potentiate Tobramycin and Polymyxin B Activity

The biofilm formation of <i>Pseudomonas aeruginosa</i> involves multiple complex regulatory pathways; thus, blocking a single pathway is unlikely to achieve the desired antibiofilm efficacy. Herein, a series of hybrids of 3-hydroxypyridin-4(1<i>H</i>)-ones and long-chain 4-aminoquinolines were synthesized as biofilm inhibitors against <i>P. aeruginosa</i> based on a multipathway antibiofilm strategy. Comprehensive structure-activity relationship studies identified compound <b>30b</b> as the most valuable antagonist, which significantly inhibited <i>P. aeruginosa</i> biofilm formation (IC₅₀ = 5.8 μM) and various virulence phenotypes. Mechanistic studies revealed that <b>30b</b> not only targets the three quorum sensing systems but also strongly induces iron deficiency signals in <i>P. aeruginosa</i>. Furthermore, <b>30b</b> demonstrated a favorable <i>in vitro</i> and <i>in vivo</i> safety profile. Moreover, <b>30b</b> specifically enhanced the antibacterial activity of tobramycin and polymyxin B in <i>in vitro</i> and <i>in vivo</i> combination therapy. Overall, these results highlight the potential of <b>30b</b> as a novel anti-infective candidate for treating <i>P. aeruginosa</i> infections.