Design and synthesis of neomycin-oxazolidinone hybrid antibiotics: exhibiting synergistic activity against Pseudomonas aeruginosa via outer membrane disruption.

Antibiotic resistance among multidrug-resistant pathogens has become a major global health challenge, highlighting the urgent need for new antibacterial strategies beyond conventional bactericidal agents. In this study, we designed and synthesized 14 neomycin-oxazolidinone hybrid antibiotics, comprising one direct neomycin-tedizolid hybrid, nine tedizolid-neomycin hybrids with alkyl linkers of varying lengths, and four linezolid-neomycin hybrids with different linker lengths. Following antibacterial spectrum evaluation against ESKAPEE pathogens, the representative compound H08 exhibited antibacterial activity against S. aureus and E. coli comparable to that of the parent antibiotics. Structure-activity relationship analysis revealed a clear influence of linker length on antibacterial activity. More importantly, H08 demonstrated synergistic antibacterial activity with all eight clinically used antibiotics evaluated against P. aeruginosa. Notably, the strongest synergistic effect was observed with novobiocin, whose MIC was reduced by 128-fold in the presence of H08. Mechanistic studies demonstrated that this synergistic effect primarily resulted from disruption of the bacterial outer membrane, thereby facilitating intracellular accumulation of co-administered antibiotics. In addition, the representative hybrids exhibited low cytotoxicity toward mammalian cells. These findings identify neomycin-oxazolidinone hybrids as promising antibiotic adjuvants for potentiating the activity of existing antibiotics against Gram-negative pathogens and provide a useful strategy for combating multidrug-resistant bacterial infections.