<p>Previous studies have explored combining β-lactams with siderophores to create Trojan horse molecules that can penetrate the outer membrane of Gram-negative bacteria via TonB-dependent transporter (TBDT). While the main advantage explaining their enhanced antibiotic activity is believed to be improved membrane permeability, other factors remain underexplored. This study evaluates three siderophore-β-lactam compounds: a bis-catechol siderophore linked to ampicillin or loracarbef, and a mixed bis-catechol-mono-hydroxamate siderophore linked to cefaclor. Minimal inhibitory concentrations showed that siderophore conjugation could enhance β-lactam efficacy by over 8000-fold. Comparison with unconjugated β-lactams revealed a complex interplay between β-lactamase susceptibility, competition with endogenous siderophore, membrane uptake, and binding to penicillin-binding proteins (PBPs). Enhanced PBP binding, particularly in <i>Escherichia coli</i>, emerged as a key factor contributing to improved bacterial inhibition by siderophore-β-lactam conjugates. Overall, the study provides insights into how siderophore conjugation enhances β-lactam activity and the therapeutic potential of the conjugates as narrow or broad-spectrum antibiotics.</p>

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Unraveling the mechanisms behind the enhanced efficacy of β-lactam-based sideromycins

  • Evelyne Lacasse,
  • Renaud Binette,
  • Héloïse Guibout,
  • Riu Liu,
  • Yun-Ming Lin,
  • Manuka Ghosh,
  • Pierre-Luc Boudreault,
  • Marvin J. Miller,
  • François Malouin

摘要

Previous studies have explored combining β-lactams with siderophores to create Trojan horse molecules that can penetrate the outer membrane of Gram-negative bacteria via TonB-dependent transporter (TBDT). While the main advantage explaining their enhanced antibiotic activity is believed to be improved membrane permeability, other factors remain underexplored. This study evaluates three siderophore-β-lactam compounds: a bis-catechol siderophore linked to ampicillin or loracarbef, and a mixed bis-catechol-mono-hydroxamate siderophore linked to cefaclor. Minimal inhibitory concentrations showed that siderophore conjugation could enhance β-lactam efficacy by over 8000-fold. Comparison with unconjugated β-lactams revealed a complex interplay between β-lactamase susceptibility, competition with endogenous siderophore, membrane uptake, and binding to penicillin-binding proteins (PBPs). Enhanced PBP binding, particularly in Escherichia coli, emerged as a key factor contributing to improved bacterial inhibition by siderophore-β-lactam conjugates. Overall, the study provides insights into how siderophore conjugation enhances β-lactam activity and the therapeutic potential of the conjugates as narrow or broad-spectrum antibiotics.