Iturin A-conjugated AgNPs as resistance-proof Antimicrobials: Coordinated suppression of outer membrane vesicle biogenesis and energy metabolism in Escherichia coli for food safety applications

The antimicrobial efficacy of silver nanoparticles (AgNPs) in food safety applications is increasingly compromised by rapid bacterial resistance evolution through virulence upregulation. A biofunctionalized nanohybrid (Iturin A-AgNPs) was engineered to synergistically combine the amphiphilic lipopeptide iturin A with AgNPs to counteract resistance mechanisms in Escherichia coli (E. coli). Transcriptomic and phenotypic analyses revealed that PVP-AgNPs triggered bacterial adaptation via overexpression of outer membrane vesicle (OMV) biogenesis genes (e.g., MlaA/C/E), flagellar assembly proteins (FliC/D/F/G/I), and suppression of energy metabolism (atpC/G/H). In contrast, Iturin A-AgNPs suppressed these resistance-driving pathways by (1) downregulating flagellar assembly proteins to impair bacterial motility, (2) breaking the “dormant mode” of reduced energy metabolism, and (3) overriding the PVP-AgNPs resistance phenotype mediated by Mla system upregulation. This multi-target mechanism effectively prevented the emergence of resistant phenotypes, as evidenced by a reduction in the minimum inhibitory concentration (MIC) against AgNPs-resistant E. coli. These findings highlight the potential of biofunctionalized nanohybrids to combat antimicrobial resistance through coordinated genetic and metabolic interference, offering a template for engineering next-generation antibacterial agents.